IONS FROM AND WITHIN AN
     ALLISON J-33 COMBUSTOR
Environmental Protection Agency Contract

      No. 68-04-0001 - Final Report
         A. M. Mellor, R. D^Anderson,

        R.  A. Altenkirch, and J. H. Tuttle
              Report No. CL -72-1

            THE COMBUSTION LABORATORY
           SCHOOL OF MECHANICAL ENGINEERING
               PURDUE UNIVERSITY
               LAFAYETTE, INDIANA
                  June 1972

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                                               EPA-R2-72-097
                  Emissions from and within an
                     Allison J-33 Combustor
            Environmental Protection Agency Contract
                  No. 68-04-0001 - Final Report
                               by
A. M. Mellor, R. D. Anderson, R. A. Altenklrch. and J. H. Tuttle
                       Report No. CL-72-1
                    The Combustion Laboratory
                School of Mechanical  Engineering
                        Purdue University
                       Lafayette, Indiana
                            June 1972

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                           ACKNOWLEDGEMENTS

     Special thanks are extended to Mr. Thomas Miller for his assistance
in the construction and maintenance of the experimental  facility and also
for his assistance in obtaining the data contained in this report.
     Messrs. P. Leonard, M. Franzen, S. Jochem, R. Shisler, S.  Jones,
G. McFarron, and K. Gross greatly aided in both the construction and
maintenance of the experimental facility and data gathering and analysis.
     The initial phase of the facility development was conducted under
Contract DAAE07-69-C-0756 with the Army Tank and Automotive Command;
subsequent facility development and the research described herein were
supported by the Environmental Protection Agency under Contract 68-04-
0001.  G. Kittredge, B. McNutt, and K. Hellman of the Office of Air
Programs provided valuable assistance.

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                           TABLE OF CONTENTS

                                                               Page

LIST OF TABLES	     v

LIST OF FIGURES	    vi

ABSTRACT	    ix

SECTION I.  INTRODUCTION AND SUMMARY 	     1

SECTION II.  DESIGN AND OPERATION OF THE
      EXPERIMENTAL GAS TURBINE COMBUSTION  FACILITY 	     4

  A.    Test Cell Hardware	     5
        1.  A1r System Description	     5
        2.  Fuel System Description  	     7
        3.  Combustor Description	     7
        4.  Probe Addition Section Description	     9
        5.  Probe Description  	     9
        6.  Probe Positioner Description	    20
        7.  Back-Pressure System Description 	    23
        8.  Water System Description	    28
  B.    Control Room Instrumentation 	    28
        1.  Temperature Monitoring Instrumentation 	    30
        2.  Emission Monitoring Instrumentation  	    31
            2.1  The Carbon Monoxide Analyzer System 	    31
            2.2  The Nitric Oxide Analyzer System  	    33
            2.3  Total Hydrocarbon Analyzer System 	    40
  C.    Summary	    40

SECTION III.  RESULTS AND DISCUSSION 	    42

  A.    Combustor Operating Points 	    47
  B.    Internal Measurements	    50
        1.  Gas Temperatures	    50
        2.  Nitric Oxide	    54
        3.  Carbon Monoxide	    59
        4.  Summary	    64
  C.    Combustor Exhaust Plane Measurements 	    64
        1.  Gas Temperatures	    66
        2.  Exhaust Plane Emissions of Nitric
              Oxide and Carbon Monoxide	    66
            2.1  The Influence of Air Flow Rate	    69
            2.2  The Influence of Overall  Equivalence
                   Ratio	    74
            2.3  The Influence of Combustor Pressure 	    75
  D.    Other Parameters 	    84
  E.    Summary	    84

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                                                                       IV
                                                               Page
SECTION IV.  FUTURE EFFORTS 	    86
LIST OF REFERENCES	    93
APPENDIX A:  EFFECT OF N02 CONVERTER ON NO	    95

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                            LIST OF TABLES
Table                                                          Page
 2-1.          0-33 Design Resume	     11
 2-2.          NO Interference Data (after Fontljn
                 et al., 1969, 1970)	     39
 3-1.          Selected Combustor Operating Points  	     49
 4-1.          Operating Point and Emissions Obtained
                 from Two J-33 Combustors  in Series	     89

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                            LIST OF  FIGURES

Figure                                                        Page
 2-1.           Combustion  facility air system	     6
 2-2.           Combustion  facility fuel system	     8
 2-3.           Combustor arrangement 	    10
 2-4.           Combustor and probe addition section 	    12
 2-5.           Combustion  facility schematic	    13
 2-6.           Gas  sampling  probe body	    16
 2-7.           Gas  sampling  probe block	    17
 2-8.           Gas  sampling  probe tip	    18
 2-9.           Gas  sampling  probe	    21
 2-10.          Gas  sampling  probe and
                 positioning systems  	    22
 2-11.          Axial  and radial (black box)
                 probe positioners	    24
 2-12.          Back pressure valve schematic   	    26
 2-13.          Back pressure valve guidance
                 system  and  engine	    27
 2-14.          Combustion  facility water system	    29
 2-15.          Gas  handling  system	    32
 2-16.          CO analyzer system	    34
 2-17.          Nitric oxide  detector schematic	    36
 2-18.          Hydrocarbon sample handling and
                 analyzer  system  	    41
 3-1.           Typical gas turbine combustor
                 flow schematic	    43
 3-2.           J-33 combustor configuration, gas
                 sampling  planes (4  of 6), and
                 probe trace position	    45

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                                                                     vn
Figure                                                        Page

 3-3.           Relationship  of probe  trace  and  gas
                 sampling  points  to J-33  combustor
                 configuration	    46

 3-4.           Combustor operating point  matrix	    48

 3-5.           Temperature versus axial position
                 (ma = 6.0 Ibs/sec, $ = .217,
                 p = 5 atm)	    51

 3-6.           NO concentration versus axial posi-
                 tion for 0°  (ma = 6.0 Ibs/sec,
                 $ = .217, p  = 5 atm)	    55

 3-7.           NO concentration versus axial po-
                 sition  for  90° ccw (ma = 6.0 Ibs/sec,
                  = .217, p  = 5 atm)	    58

 3-10.          CO concentration versus axial po-
                 sition  for 0° (ma = 6.0  Ibs/sec,
                 <{> = .217, p  = 5 atm)	    60

 3-11.          CO concentration versus axial po-
                 sition  for 90° ccw (ma = 6.0 Ibs/sec,
                 4> = .217, p  = 5 atm)	    61

 3-12.          CO concentration versus axial po-
                 sition  for 90° cw (ma =  6.0 Ibs/sec,
                 4> = .217, p  = 5 atm)	    62

 3-13.          CO concentration versus, axial po-
                 sition  for  180° cw (ma = 6.0 Ibs/sec,
                 4> = .217, p  = 5 atm)	    63

 3-14.          Schematic of postulated primary  and
                 secondary zone flow pattern for  the
                 J-33 combustor	    65

 3-15.          Combustor exit plane temperature
                 traverse  (probes in locations
                 numbered one in Fig. 3-3)	    67

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                                                                     vi i i
Figure                                                         Page

 3-16.         Combustor exit plane temperature
                 traverse (probes  in locations
                 numbered two in  Fig.  3-3)	    68

 3-17.         Radial  NO concentrations  at  combustor
                 exit  plane versus air flow rate
                 (average)	    70

 3-18.         Radial  NO concentrations  at  combustor
                 exit  plane versus air flow rate	    71

 3-19.         Radial  CO concentrations  at  combustor
                 exit  plane versus air flow rate
                 (average)	    72

 3-20.         Radial  CO concentrations  at  combustor
                 exit  plane versus air flow rate	    73

 3-21.         Radial  NO concentrations  at  the combustor
                 exit  plane versus overall  equivalence
                 ratio (average)	    76

 3-22.         Radial  NO concentrations  at  the combustor
                 exit  plane versus overall  equivalence
                 ratio	    77

 3-23.         Radial  CO concentrations  at  the combustor
                 exit  plane versus overall  equivalence
                 ratio (average)	    78

 3-24.         Radial  CO concentrations  at  the combustor
                 exit  plane versus overall  equivalence
                 ratio	    79

 3-25.         Radial  NO concentrations  at  combustor
                 exit  plane versus pressure (average)   ....    80

 3-26.         Radial  NO concentrations  at  combustor
                 exit  plane versus pressure	    81

 3-27.         Radial  CO concentrations  at  combustor
                 exit  plane versus pressure (average)   ....    82

 3-28.         Radial  CO concentrations  at  combustor
                 exit  plane versus pressure	    83

 4-1.           Complete combustion facility schematic   ....    87

 A-l.           Normalized concentration  versus inverse
                 temperature	    97

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                               ABSTRACT

     Because of the possible future widespread use of the gas turbine
engine in automobiles, and the imminence of federal  emission standards
for aircraft, gas turbine combustion and emission characteristics are
currently being investigated in earnest.  Much information concerning
specific pollutant concentrations as measured at the engine exhaust is
presently available.  Several analytical combustor modeling programs
have also been developed (Mellor, 1971).  The basic processes of pol-
lutant formation and destruction occurring within the combustor have,
however, received little attention to date.  In an effort, therefore,
to obtain this fundamental  type of experimental information, a gas
turbine combustion facility has been designed and constructed.
     After a review and description of the combustion facility, re-
sults are presented which include gas temperature, carbon monoxide,
and nitric oxide concentration profiles as a function of axial and radial
position inside an Allison  J-33 combustor.  In addition some combustor
exit plane measurements are reported.  Specifically, the isolated effects
of combustor pressure, overall equivalence ratio, and air flow rate on
CO and NO concentration at  various radial  positions  are investigated.
These results are qualitatively explained  in terms of basic combustor
processes.
     Unheated combustor inlet air was used for the above studies; a few
preliminary experiments using heated air are also described.

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                      I.  INTRODUCTION AND SUMMARY

      Emissions  from various types of combustion systems have been in-
 vestigated in some detail in recent years.  Government legislation has
 attempted to force the advancement of emission control technology through
 the establishment of  federal emission standards for many mobile and sta-
 tionary pollution sources.  As effort has been expended to meet the fed-
 eral  emission standards, continuous flow combustion systems have received
 increasing attention.  A continuous flow combustion device of wide appli-
 cation is the gas turbine.
      Because reasonably precise control  of the combustion process is
 possible in a gas turbine combustor, it is felt to possess inherent emis-
 sion  control advantages over other types of combustion systems.  In a
 gas turbine combustor, for example, it is theoretically possible and
 practically realistic to tailor the combustion zones to those conditions
 of local equivalence  ratio best suited to total emission reduction.  In
 general, this tailoring of the combustion zones is made possible because
 of the relative freedom of the combustor designer to specify the combus-
 tion  chamber configuration.  This configuration, of course, controls
 such  things as fuel  and air flow distributions, recirculation patterns,
 residence times, and other parameters of importance in emission control.
      In contrast, the combustion event in the spark or compression igni-
 tion engine combustion chamber is difficult to control.  Those techniques
which have been utilized to reduce spark ignition engine emissions, such
 as the alteration of ignition timing and exhaust gas recirculation, have
 in general resulted in the deterioration of that engine's performance.

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 Therefore to couple good vehicle performance with a minimum of pollu-
 tant emission is one reason that the gas turbine engine is  being con-
 sidered as a possible replacement for spark and compression ignition
 engines in many vehicular applications.
     Because of the possible future widespread use of the gas turbine
 engine in automobiles, and the imminence of federal emission standards
 for aircraft (which are in large part powered by gas turbine engines),  a
 definite need exists for fundamental information concerning gas turbine
 emissions.  It is most logical to begin a basic study of gas turbine
 pollution by investigating the effect of combustor operating parameters
 on pollutant emissions.  It is, however, imperative that the operating
 parameters be varied individually and that the effect of each single
 operating parameter change upon pollutant emission levels be noted.  To
 this end, an experimental  program, to be discussed in detail in the  fol-
 lowing pages, has been started.
     Briefly, the experimental setup consists of a J-33 combustor burning
 liquid propane.  Variable  engine parameters are combustor pressure,  equiv-
alence ratio, and air flow rate.  Later experiments will  also include
combustor inlet air temperature.  The condition of the engine is monitored
remotely during any experimental investigation.  A continuous gas-sampling
system for the determination of CO, NO and HC concentrations is employed.
Samples can  be extracted at the exit plane of the combustor as well  as  at
various internal  locations.  Temperatures are monitored both at the  exit
plane and internally, using a probe-mounted Pt/PtRh  thermocouple.
     Exit plane and internal combustor CO and NO concentrations and  gas
temperatures have been collected.  Temperature measurements indicate
that strong  radial  gradients exist, a result of the influence of penetration

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jets.  CO and NO concentration measurements at various  axial  positions
in the combustor yield the same trends reported in the  literature.   These
internal measurements were for a single operating point.
     Exit plane CO and NO concentrations at various radial  positions were
studied as functions of combustor pressure, equivalence ratio, and  air
flow rate.  Combustor centerline CO concentrations increased  with pressure;
other radial positions exhibited more erratic behavior.  NO concentrations
generally increased with pressure.  CO and NO exit plane  concentrations
increased with increasing equivalence ratio for almost  all  radial positions;
this trend is consistent with the observations of other investigators.
Increasing air flow rate caused the NO concentrations to  decrease only
slightly and CO to increase.

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                   II.  DESIGN AND OPERATION OF THE
             EXPERIMENTAL GAS TURBINE COMBUSTION FACILITY

     Once the determination was made to pursue in earnest gas  turbine
pollutant emissions research, the design and construction of an exper-
imental facility capable of realistically simulating gas  turbine com-
bustion was necessary.  The design, construction, and testing of such
a facility occupied the major portion of the preceding year's  experi-
mental program.  The facility was to be capable of simulating both auto-
motive and aircraft type gas turbine combustion realistically so that
combustor operating parameters (pressure, air flow, and overall equiv-
alence ratio) could be varied to determine fundamental trends  concerning
gas turbine emissions.  With the exception only of inlet air temperature
(which was not varied for most of the experiments conducted to date), it
is felt that the facility to be described is in fact such a realistic
simulation and that the data obtained and reported in the following sec-
tion verify the facility's ability to provide the desired fundamental gas
turbine emission information.
     This chapter essentially is divided into two sections.  The first
section provides a description of the test cell hardware and those aux-
iliary systems necessary for combustor parameter control  or component
survivability.  The second section of this chapter entails a description
of control room instrumentation.  Included are descriptions of those
systems required for monitoring the combustor condition,  various temper-
atures associated with the combustion process, and most significantly,
the combustor emissions.

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                        A.  TEST CELL HARDWARE

 1.  Air System Description
     Because of the large mass flow rates and high compressor pressure
 ratios used in many modern aircraft gas turbine engines, a large air
 compressor network is essential to any research laboratory attempting to
 study realistic gas turbine combustion.  The air compressor system which
 supplied the test facility had a capacity of approximately 3000 cu ft
 and could provide air system pressures of up to 2400 psig.  Sustained
 air flow rates of 6 Ibs/sec were possible for run durations of approx-
 imately 40 minutes under normal combustor operating conditions.  In ad-
 dition, the basic combustion system could pass air flow rates of up to
 10 Ibs/sec for short periods.  Although the main air system compressors
were in service throughout any run situation, the system was basically
of the blowdown type.   To date the air system has proven satisfactory for
the needs of the program.
     The basic test cell air system is shown schematically in Fig. 2-1.
The three inch main air supply ducting was of heavy wall carbon steel,
and all high pressure control lines were stainless steel.   The main air
supply system included two 3000 psig inlet capacity remotely controlled
air regulators mounted in parallel, a safety burst disc, a 2 1/8 inch
orifice type flow meter, a pneumatically operated air throttle valve,
and finally a diffuser section mounted immediately upstream of the com-
bustor.  Orifice plate differential pressure was monitored continuously
on a differential  pressure gage in the control room and recorded perma-
nently and continuously through a differential pressure transducer/Ellis
bridge amplifier/Honeywell Model  1508 Visicorder system.

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                          Main Air Line
a
               X-D
               Y
           Instrument
            Air Line
  Building  Air
                                                         Burst
                                                          Disc
                                            ir Throttle
                                              Valve
                                           Diffuser
       Z-
       I

To Water System
               Figure 2-1.  Combustion facilitv air svstem

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 2.   Fuel  System Description
      The  fuel  used in  the combustion  study was  commercial purity liquid
 propane since  it is inexpensive  and readily  available.  The  fuel system
 is  shown  schematically in Fig. 2-2.   When the 500  gallon storage tank
 was pressurized with nitrogen, the five  10 in x 10 ft cylindrical steel
 fuel  delivery  tanks were  filled  from  the storage tank.  This tank was
 then  isolated, and the  fuel delivery tanks were  pressurized to  the desired
 supply  pressure using  a ten bottle nitrogen  supply manifold.   All fuel
 flow  was  passed through a suitable fuel filter  and then underground to
 the test  cell  area. Fuel  flow rate was controlled through a pneumati-
 cally operated fuel throttle valve and measured using a Potter turbine
 flow  meter.  Frequency  converters were used  to  convert the flow meter
 output  to a calibrated  mi Hi amp  output signal.  Like the air flow, fuel
 flow  was  also  permanently  and continuously recorded using a six channel
 Honeywell Visicorder.
      In the interests of  safety  the main fuel system tanks were positioned
 away  from the  test  cell area, stainless steel lines and fittings were
 extensively used, both  manual and solenoid type vent valves and automatic
 pressure relief  valves  were judiciously placed  at  various system locations,
 and all fuel system pressures were continuously monitored.  The fuel sys-
 tem as shown in  Fig. 2-2 has performed satisfactorily to date.

 3.  Comb us tor  Description
      In the initial  facility configuration all  combustion occurred in an
Allison J-33 turbojet combustor mounted in a stainless steel  converging
housing.  The  combustor housing,  in turn, was secured to a thrust table.
The standard J-33 fuel  nozzle and conventional magneto-energized igniter

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  Fuel
Delivery
  Tanks
VP"
 	fuel Filter
in
                         -$—Kh-&
                                                         Fuel
                                                        Storage
                                                         Tank
                                              Nitrogen
                                              Manifold
                      Fuel Tlirottle Valve

                           Turbine Flow Meter
                                                      J-33 Combustor
                Figure  2-2.  Combustion facility fuel system

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 were  employed.   The basic  combustor arrangement is shown in Fig. 2-3.
 In  order  to  provide the necessary experimental data for a simultaneous
 analytical heat  transfer study, the J-33 flame tube was outfitted with
 several chromel-alumel thermocouples; the results of this study have
 been  reported by Owens (1972).  Through the courtesy of the Detroit
 Diesel Allison Division of General Motors, the J-33 design resume shown
 in  Table  2-1 was obtained.

 4.  Probe Addition Section Description
     The  J-33 combustor casing exit was flanged to accept the probe ad-
 dition section as shown in Fig. 2-4.  The purpose of this stainless steel
 section was  to change the direction of the exhaust gas flow such that a
 probe could  be directly inserted into the combustor.  The surface of this
 section was wrapped with copper water cooling lines, and the probe window
was cooled with  injected nitrogen.  Fig. 2-5 schematically shows the over-
 all facility configuration.

 5.  Probe Description
     The combustion chamber of a gas turbine engine is a most severe
environment.  It is characterized by relatively high mass flows, exces-
sive turbulence, large temperature gradients, high pressure in many
 cases, recirculating flow patterns, and extremely high local  temperatures
which in some locations approach the adiabatic flame temperature.  The
task of designing a probe capable of surviving this type of environment
for long periods of time is very challenging.  Some probe failures  have
in fact been mentioned in the open literature for probes attempting to
sample gas turbine engine exhaust at the engine exit station  (Hare  et al.,

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                                                  Igniter
Fuel Line

o

o
vl

D.
/

\
                                                                     Combustor
                                                                        />
                                                           Combustor  Casing
                              Fuel  Nozzle
                          Figure 2-3.  Combustor arrangement

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     Table 2-1.  J-33 Design Resume
Military Air Flow
Normal Air Flow
Military Inlet Temperature
Normal Inlet Temperature
Military Inlet Pressure
Normal Inlet Pressure
Military Volume Flow
Normal Volume Flow
Average Pressure Loss
Liner Cooling Air Flow
Primary Combustion Air Flow
Secondary Combustion Air Flow
7.64 Ibs/sec
7.17 Ibs/sec
435° F
390° F
141 in Hg abs
126 in Hg abs
40.7 cu ft/sec
40.9 cu ft/sec
4.5%
8.0%
23.4%
68.3%

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                                           purge
J-33 Corabustor

         Figure 2-4.  Combustor and probe addition section
                                                                          Sampling
                                                                           Probe

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Air System
Thrust Stand
                       Fuel System
                                                                   Transition Section
                                                                                Back-Pressure
                                                                                    Valve
                                              Probe Addition Section
                                                                                               Exhaust
                              Probe  Positioner
                             Figure  2-5.   Combustion  facility  schematic

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                                                                       14
 1971).   It  is  apparent that the engine exit station, although itself a
 severe  environment, is orders of magnitude less severe than the combustion
 chanter.  The  probe design which is to be reported below was found able
 to withstand the combustor environment.  One probe has sampled combustor
 exit  plane  gases for approximately eleven hours with only the develop-
 ment  of a relatively minor probe tip leak during the eleventh hour and
 has also sampled within the combustor for approximately 85 minutes (in-
 cluding a large fraction of that time sampling from the primary zone).
 A second probe of similar design has withstood over two hours inside the
 combustor.
      The development of the final successful probe design reflected the
 difficulties mentioned above.  Two early probe designs failed quickly
 but did provide through their failure the information needed to design
 an acceptable  probe.
      The intent of the probe was to sample gases and monitor gas temper-
 ature at various axial and radial positions within the combustor or at
 the combustor exit.  For purposes of gas temperature measurement a plat-
 inum/10% platinum rhodium thermocouple (MgO insulation, sheathed in in-
 conel) was mounted through small "half-moon" shaped sections directly to
 the side of a gas sampling probe; the resulting bead position was about
 1/16  in ahead of the gas sampling tip.  The thermocouple was of the ex-
 posed junction type and was intended to provide only gross estimates
of the  local combustor temperatures. A 1/16 in diameter thermocouple
with  .01 in wires failed, however, to provide the desired temperature
estimates.  Typical behavior was as follows:  upon insertion of the probe
into  the combustor the thermocouple provided reasonable temperature es-
timates.  After the probe was rotated through approximately 90°, however,

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                                                                       15
 the  thermocouple  signal became very erratic possibly indicating an inter-
 mittent breaking  and making or short-circuiting of the thermocouple lead.
 The  same behavior was noted with two other Pt/10%PtRh thermocouples of
 similar dimensions.  Consideration of the very brittle nature of the plat-
 inum leg of  this  thermocouple indicated that the failure of the two ther-
 mocouples was caused, most probably, by stresses in the platinum leg
 induced through the mechanical rotation of the probe.  New 1/8 in diameter
 thermocouples with .025 in wire diameter and with the platinum leg re-
 placed by "Fibro  Platinum" (which is better able to withstand turbulent
 high  temperature  conditions) have been mounted to the probe for subsequent
 temperature measurements and proved satisfactory for the experiments con-
 ducted to date.
      The probe was inserted into the J-33 combustor through the probe
 addition section  (see Fig. 2-4} and supported both at the probe window
 and  at the cradle of the probe positioner (to be described later).  The
 gas  sampling portion of the probe body consisted of three concentric
 316  stainless steel tubes as shown in Fig. 2-6.  The relative position
 of the three concentric tubes was maintained through the use of several
 small welded beads at various locations along the length of the probe,
 and  three distinct passages inside the probe body were thus assured.  Pres-
 surized cooling water entered the probe at the probe block (Fig.  2-7) and
 flowed to the probe tip in the outer annul us.  At the probe tip the cooling
water flow was reversed (see Fig. 2-8) and proceeded through the  center
 annul us back to the probe block where it exited.  The center probe body
 tube  carried sample gases to the gas sampling system delivery lines.
 Cooling water flow pressure was variable to approximately 250 psig.

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                                      3" ,.
                                      TT  dia.
                                             H2
-------
                                      Plug

                                                  Scale:   Full
                              A-A
Figure 2-7.  Gas sampling probe block

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                                 L.016"    H2° -
                                                        Scale  6:1
                                         B-B
Figure 2-8.  Gas sampling probe tip
                                                                               00

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                                                                       19
      The  design of  the gas sampling tip reflects consideration of the
 requirements  inherent in any suitable sampling probe design as well  as
 consideration of those factors peculiar to the particular combustor
 environment encountered.  In order to obtain accurate information con-
 cerning comfaustor gas composition, the composition of the gases at the
 entrance  of the gas sampling probe must be essentially identical to the
 gas composition at  the entrance of the emission monitoring instrumenta-
 tion.  In other words, all gas reactions must be quenched in the short-
est possible distance in the sampling probe.  One ideal way in which
 to accomplish this  immediate quenching entails the use of a converging-
diverging probe tip nozzle for rapid sample flow acceleration and ex-
pansion.  As the sampled gases then flow through the probe body, additional
reduction in gas static temperature may be realized through the added
quenching effect provided by the probe cooling water flow.  These two com-
bined quenching methods have been used frequently in the past in elemen-
tary flame studies and other assorted combustion experiments.
     However, one of the operating characteristics of the J-33 cornbustor-
fuel nozzle combination used in the subject research was the rapid increase
in carbon formation associated with operation at superatmospheric pressures.
Consequently, the final probe tip design shown in Fig. 2-8 represents a
compromise between the ideal  sampling probe and a probe able to withstand
the combustor environment.   For example, the ideal sampling probe would be
of infinitesimal diameter to prevent flow disturbance whereas a working
probe must be of sufficient diameter to allow a suitable cooling water
flow, as well as provide sufficient structural rigidity to withstand the
combustor environment.  Similarly, an ideal sampling probe tip would

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                                                                       20
 consist of a converging-diverging nozzle; however, such a tip could not
 be constructed so that mechanical integrity could be maintained and
 blockage by soot prevented.  Thus the final tip design and dimensions
 shown in Fig. 2-8 were finalized.  As an added safeguard against the
 possibility of carbon blockage, the probe gas sampling tube was purged
with nitrogen during all combustor starts, all purposely induced com-
 bustor transients, all probe rotations, and all combustor shutdowns.
Whereas probe blockage had consistently occurred with the earlier probe
designs, this major inconvenience was successfully avoided through the
use of the above mentioned operating procedures and probe design.
     In order to obtain a circular probe trace upon probe rotation,
the tip section of the probe was offset from the probe centerline by a
distance of 1 9/32 in following Sawyer et al. (1969).  This offset, as
well  as probe body, block, mounting plate, and drive gear are shown in
Fig.  2-9.

6.  Probe Positioner Description
     As previously mentioned, gas sampling and temperature measurements
were made inside the J-33 combustor as a function of axial and radial
position.   For the purpose of providing accurate, reproducible, and re-
motely controllable positioning of the probe tip within the combustor,
the probe positioning system as shown pictorially in Fig.  2-10 was con-
structed.   The circular probe block was positioned inside a roller bear-
ing pressed into the probe mounting plate.  The probe mounting plate in
turn was attached adjustably to the positioner carriage.  Remotely con-
trollable longitudinal movement of the positioner carriage was accomplished
through a worm gear/electric motor combination.  A series  of micro-switches

-------
Figure 2-9.   Gas sampling probe

-------
Figure 2-10.  Gas sampling probe and
        positioning systems
                                                                             r )
                                                                             I j

-------
                                                                       23
 (see  Fig. 2-11) aligned parallel to the carriage travel and actuated by
 a  cam extending from the positioner carriage provided accurate control
 room  information concerning the probe tip axial position by lighting ap-
 propriate control panel lamps.  To achieve remotely controllable probe
 rotation an electric motor/drive gear combination was mounted on the
 thrust stand near the probe addition section window.  This drive gear
 then  meshed with the probe gear (seen in Fig. 2-9) which was welded to
 a  collar mounted on the probe body.  A small, rounded pin extended
 through the collar and traveled in a smooth longitudinal slot which had
 been machined in the probe body.  In this way the probe body was allowed
 to slide axially through the collar but was prevented from rotating rel-
 ative to the collar.  A helipot driven by the probe gear and constituting
 part of a battery powered electrical circuit impressed a variable voltage
 on the Honeywell Visicorder.  After calibration of this assembly, the
 probe radial position was continuously and permanently recorded via the
 oscillograph trace.  Both axial and radial remote probe positioning
 schemes performed satisfactorily through the extent of the research ef-
 fort.

 70  Back-Pressure System Description
     In order to simulate modern gas turbine combustion, certain require-
ments are imposed upon combustor pressure.  In general aircraft gas tur-
bine applications, combustor pressures on the order of 15 atmospheres
are common.   However, in automotive gas  turbine applications combustor
pressures rarely exceed six atmospheres.  Therefore, in an attempt to
construct a facility acceptable for general gas turbine combustion re-
search, it was necessary to provide the  capability for continuous combustor

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Figure 2-11.  Axial and radial (black box)

            probe positioners
                                                                                i j
                                                                                -i-

-------
                                                                       25
 pressure  regulation  from  1-15 atmospheres.  The device designed for
 this  purpose  and shown in Fig. 2-12 and 2-13 consists of a translating,
 conical center-body, a beveled engine exit plane surface, and two con-
 centric cylinders.
      To insure  the survival of the center-body in the hot exhaust gas
 stream, pressurized  cooling water was forced through a large number of
 small holes drilled  through the front center-body cone.  This method of
 cone  cooling  essentially placed a protective sheet of water over the
 leading cone  surface and to date has successfully prevented any notice-
 able  erosion  of the center body cone.
      As can be seen in Fig. 2-13 the translating section of the back-
 pressure valve assembly was mounted on a dolly and accurately guided
 in movement through the use of linear bearings and precisely positioned
 hardened and  ground steel guide shafts.  Adjusting mechanisms were pro-
 vided on the  dolly to insure the accurate positioning of the center-body
 cone  and concentric cylinders.
      Control  of combustor pressure was effected through the action of
 three air cylinders mounted on the engine transition section (Fig. 2-13)
 and connected to the translating section of the back-pressure valve.  By
 increasing air cylinder pressure the back pressure valve cone was forced
 forward effectively reducing the engine exit area and thereby increasing
 combustor pressure.  The positioning of heavy springs against the piston
head on the unpressurized side of each air cylinder eliminated the jerking
effects of starting friction on the translating section motion and also
insured that atmospheric combustor pressure would be realized in the event
of an air system failure.  To date relatively precise and remote control

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                        Air Cylinder
H20 Inlet
                                                                                     Translating
                                                                                      Cylinder
          V  ,\ _ V  \  \\V\\\\  \  \  \
                                                                           Center Body
Transition Section
                                                      Cooling Holes

                        Figure 2-12.  Back pressure valve schematic

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                                                      27
Figure 2-13.   Back pressure valve guidance
             system and engine

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                                                                       28
of combustor pressure to a value of 10 atmospheres has been routinely
achieved.

8.  Hater System Description
     In order to provide adequate cooling for the back-pressure valve
cone and the gas sampling probe, a high pressure water supply system
was designed and installed and is schematically shown in Fig. 2-14.
The total system capacity was approximately 1000 gallons and could sup-
ply water as necessary at pressures up to 400 psig.  For the purposes
of insuring satisfactory water flow control, a remotely actuated main
water throttle valve was installed and found to function well.  All
system pressures were monitored continuously from the control room.

                   B.  CONTROL ROOM INSTRUMENTATION

     Prompted by the magnitude and complexity of the experimental re-
search effort and in the general interest of safety, all test cell
activity was monitored from a separate control room.  The instrumenta-
tion assembled within the control room can be conveniently divided into
three broad categories.  The first consists of that instrumentation
necessary for the safe and accurate control of all systems relating  to
the actual  operation of the main combustion system.  These systems have
been discussed previously and, therefore, need no further comment.  The
second class of instrumentation to be briefly discussed includes all
temperature monitoring systems assembled for the research.  The final
instrumentation category, and one of utmost importance to the objectives
of the research, includes all continuous flow emission monitoring

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         9
Main
 Air
Line
                                        1000 Gallon
                                       Water Storage
                                           Tank
                                                                  Vents
                                                                   -S—
                                                                              i-z
                                                                                          Water
                                                                                          Supply
                                                                                Water
                                                                              Softener
                                        ->- Back Pressure Valve Cooling Water
                                         >- Probe Cooling Water
                           Figure 2-14.  Combustion facility water system

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                                                                       30
equipment.  These  latter systems will be described fully in the follow-
ing section.  A six channel Honeywell Model 1508 Visicorder was used to
record the output  of the CO, NO, and HC detectors, as well as probe po-
sition and air and fuel flow rates, as mentioned previously.

1.  Temperature Monitoring Instrumentation
     In order to monitor the condition of the combustion facility
continuously, it was necessary to measure certain important system
temperatures.  Included in this list were local  combustor temperature
as measured through the use of a probe-mounted platinum/10% platinum
rhodium exposed junction thermocouple.  At the combustor exit sampling
plane, combustor exit temperatures were measured with two United Sensor
Corporation aspirated and radiation shielded chromel-alumel thermo-
couples.  These thermocouple probes were positioned with compression
fittings through the combustor casing and could be moved manually to
various, accurately known radial depths into the combustor exhaust plane.
Specially designed thermocouple positioners were used for this purpose.
All thermocouple outputs were recorded continuously on Honeywell class
15 self-balancing potentiometers.  The data to be reported were all
referenced to a temperature of 0° C.
     In addition, the back-pressure valve front cone temperature was
monitored during the initial  testing of the back-pressure system.  Once
it was determined that the cone water cooling provisions were more than
adequate to insure the cone's survival, this thermocouple was taken out
of service.
     The final  thermocouple employment was in the collection of flame
tube wall  temperature data to be used in conjunction with an analytical

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                                                                       31
gas turbine heat transfer study (Owens and Mellor, 1971, Owens, 1972).
For this purpose the J-33 flame tube was outfitted with a series of ten
chromel-alumel thermocouples.  The results of this investigation as well
as information concerning the relative positions of the thermocouples
and flame tube cooling slots and penetration air holes are presented in
Owens (1972).

2.  Emission Monitoring Instrumentation
     The gas concentrations measured during the present study were pre-
dominantly CO and NO, as discussed in Section I; the overall  gas sampling
system as well as the specific CO, NO, and hydrocarbon detection systems
are fully described below.
     The sample gas handling system is shown schematically in Fig. 2-15.
Unless otherwise noted, all lines, fittings, and other components were
stainless steel and/or teflon coated to minimize surface reactions or
adsorption causing distortion of the true gas composition as  the sample
gas was transported to the various analyzers; essentially the techniques
recommended by Chase and Hum (1970) were used.
     All instrumentation received span and zero checks before and after
each run, as well as frequent zero checks during each run.  In addition,
the entire sampling system was inspected weekly and cleaned as required.

2.1  The Carbon Monoxide Analyzer System
     A Beckman Model 315A (short path) NDIR (non-dispersive infrared)
analyzer was used for the continuous monitoring of sample gas CO con-
centration.  The analyzer section of this instrument employed a stacked
sample cell configuration with both a 13 1/2 inch cell for a  useful
range of 0-250 ppm (without back pressure), and a 1/8 inch cell for a

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Gas Sampling Probe
                                                                                   Relief
                                                                                    Valve
                                                      Purge System
      rurgu oybtum      i
       M2      I    f
    Converter
     NO
  Detector
   (Chem.)
                            Bypass
                             Flow
CO Analyzer
  (NDIR)
                                                                                    Heated
                                                                                      Line
                                                                            Bellows  Pump
            Vacuum
             Pump
     I
  Vacuum
   Pump
Total Hydrocarbon
    Analyzer
(flame ionization
   technique)
                                       •"igure 2-15.  Cas handling system
                                                                                                                ts)

-------
                                                                      33
 range  of 0-20%.   In  addition, the CO detector flow system incorporated
 a  back-pressure  regulator in the 0-250 ppm flow line, which allowed the
 cell pressure  to be  increased to 75 psig (limited by the thickness of
 the sapphire windows in the cell).  This modification allowed the lower
 range  sensitivity to be increased to 0-100 ppm full scale.  Repeatability
 for the  NDIR measurements was guaranteed to be 1% of full scale reading
 for both  ranges.   The specific CO analyzer flow system is shown schemati-
 cally  in  Fig.  2-16.  Normal CO concentrations encountered in the J-33
 combustor dictated the constant use of the 0-20% range.
     Condensate  traps positioned in the sample line and capable of with-
 standing  10 atmospheres pressure were reported by Beckman to eliminate
 the problem of water vapor interference on sampling measurement accuracy.
 However,  it should be mentioned that the presence of C02 in concentrations
 on the order of  300 ppm can cause approximately a 10 ppm CO measurement
 error.
     The normal  CO detector sample flow rate was 1600 cc/min.  Since for
 future run conditions low or atmospheric combustor pressure (not conducive
 to natural sample flow) might be desired, a vacuum pump was installed to
 insure adequate sample flow to the CO analyzer.   For the experiments de-
scribed in Section III (with combustor pressures of three atm and above),
the CO analyzer  response time was on the order of one second, indicating
rapid passage of the gas sample from the combustor to the instrumentation.

2.2  The Nitric Oxide Analyzer System
     The second gas constituent monitored was nitric oxide, and was  meas-
ured continuously using a chemiluminescent technique similar to that
recently developed by Fontijn et al.  (1969, 1970).   This method involves

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    .._ Water Traps
     3-0-
Sample
 Inlet
                    Calibrated Gas Manifold
                            	(
                           I -rr!
                           « &
                   I
               H   '
                            Span
                            Zero
Filter
                                                            jl/8"
                                                           Cell
       r
                                                                  0-20%
                                 13 1/2" Analyzer Cell
                                        0-100 ppm
                                              Filter
                                                       (
                               »J7  p<
                                ^•/  ' 
-------
                                                                      35
 the measurement of  the intensity emitted by the chemiluminescent reaction
 between nitric oxide and ozone.  The NO detector designed and constructed
 for the present research is shown schematically in Fig. 2-17.
     After the completion of the initial construction of the NO detector,
 the linearity of the instrument and its dark current behavior were thor-
 oughly investigated.  For the linearity study a gas mixture of known NO
 concentration was prepared by a partial pressure technique.  A known vol-
 ume of this prepared NO/N? mixture was then injected into the system's
 exponential dilution flask while N~ pressure upstream of the dilution
 flask was maintained at a constant pressure of 100 torr.  Total reaction
 flask pressure was maintained at 3 torr through a microvalve throttling
 control.  The dilution flask nitric oxide concentration will vary ac-
 cording to the equation (Fontijn et a!., 1969, 1970):
                          C = CQ exp (-Qt/V)
where
             C  = initial NO concentration in the injected sample
             Q  = volume flow rate
             V  = dilution flask volume
             t  = time
Therefore, if the electrometrometer net signal  (i.e.,  total  signal  less
dark current), when plotted on a semi-log scale versus time, is  a straight
line, the linearity of the instrument has been  shown.   After every NO de-
tector system modification, a linearity check was accomplished.   The  system
linearity was always realized.

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Gas
Sample
                         Shutoff
                          Valve
             Micro-Valves
                              Pressure
                              Regulator
                               ressure
                               Gauge
                                                   Flow
                                                  Meter
                                   J^ Three-way
                                        Valve
                    Exponential!
                     Dilution
                       Flask
                                     \
      Calibration Gas
                         Magnetic
Manometer
                      Photomultiplier
                            Tube
                                                                                High Voltage
                                                                                Power Supply
                        Manganese Dioxide Filter
                                                                      Vacuum Pump
                                Figure 2-17.  Nitric oxide detector schematic
                                                                                                               ON

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                                                                       37
      With  the  assurance of  linearity, meaningful calibration of the NO
 detector was then  accomplished with the use of only one span gas of
 known NO concentration (usually 202 ppm in Nj.  This gas was passed
 through  the NO detector and the electrometer signal noted.  The dark
 current  electrometer signal was also recorded.  From the linearity check
 the calibration curve was known to be a straight line.  The two points
 then determining the calibration graph of NO concentration versus net
 electrometer signal were the known concentration and net signal of the
 single span gas and the zero concentration point characterized by a net
 signal of  zero.  The NO detector was calibrated using the above single
 span gas technique before and after every experimental run.
     The method of operation of the nitric oxide detector is determined
 by the chemi luminescent reaction between NO and 0,.  It has been well
 verified that the chemi luminescence is due to the following reaction
 scheme (Fontijn et al., 1969, 1970):
                          NO + 03 •*• N02*
                                          hv
To prevent collisional deactivation of the excited N02* molecule and
thus to insure that a chemi luminescent type reaction does occur, total
reaction flask pressure was maintained at a level of 3 torr.  It was
then necessary, of course, to establish a vacuum tight flow system
through the NO detector.  A Welsh duo seal vacuum pump having a capac-
ity of 500 Jl/min at STP was used to draw sample gas through the instru-
ment.  Sample and ozone flows were monitored through observation of
reaction flask pressure and reactant partial pressures.

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                                                                      38
     Normal operation of the NO detector commenced with the establish-
ment of  a "relatively absolute" vacuum throughout the nitric oxide de-
tector flow system and reaction flask.  An ozone flow sufficient to
maintain a steady 2 torr reaction flask pressure was then established.
This ozone flow magnitude assured that 0., would be present in sufficient
excess to insure that the overall reaction be first order in NO.  The
ozone flow rate was then held constant through the duration of the run.
A micro-metering valve on the sample line was subsequently adjusted to
allow sufficient sample flow to establish a 3 torr total pressure in the
reaction flask.  The electrometer net signal  was noted and the NO con-
centration of the sample gas could then be deduced from the previously
discussed calibration curve.
     One difficulty was encountered initially with the NO detector total
response time, here defined as that time necessary for the complete re-
movable of an unwanted, "old" sample gas from the flow system and the
establishment of the correct reaction flask pressure and electrometer
output signal  for the new sample.   This total response time was on the
order of 5 minutes and considerably reduced the amount of NO data which
could be compiled during any one run.  Testing of the total system
showed that the MnO^ filter shown in Fig. 2-17 was responsible, as the
filter was packed too tightly.  Modification  of the filter design has
reduced the response time to about one minute.
     In large part responsible for the great  accuracy inherent in the
chemiluminescent technique of NO concentration measurement is the rel-
atively complete lack of interference of other sample gas constituents
upon the accuracy of the NO measurement.  Table 2-2 presents data

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                                                             39
          Table 2-2.   NO  Interference  Data

          (after,Fontijn  et al.,  1969,1970)
Constituent
  Max Concentration
Generally Encountered
   in Air Quality
   Monitoring,  PPM
 Concentration
Used at whi ch NO
Interference Was
  Detected at
NO 1 10 PPB, PPM
N02
C00
2
CO
C2H4
NH,
3
SO,
2
H 0
3
500

100
1
3

3

100% Saturation
9
650

300
5
9

25

75% Saturation

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                                                                      40
 taken by  Fontijn et al. (1969, 1970) which illustrate this most desirable
 quality.
     The  nitric oxide detector system also included a N0? converter as
 shown in  Fig. 2-15.  A detailed discussion of the converter and limited
 experimental results obtained from it are contained in Appendix A.

 2.3  Total Hydrocarbon Analyzer System
     Although a Beckman Model 402 Total Hydrocarbon Analyzer utilizing
 flame ionization detection was purchased for use in the subject research
 effort, instrument malfunctions delayed its use until late in the contract
 period.   For this reason only a few unburned hydrocarbon measurements
 are reported.  In Fig. 2-18 is shown the flow schematic for the hydro-
 carbon analyzer.  Note that a portion (51/2 feet) of the sample line
between the probe block and the relief valve was unheated; the use  of a
flexible  teflon-coated high pressure line between the block and the
purge system prohibited the use of heating tapes.

                              C.   SUMMARY

     Data have been obtained in the above-described facility and will
be described and discussed in the following section.  To repeat, the
only aspect of this work which limits its application to practical  en-
gines is that unheated air was used at the combustor inlet for most of
the studies.  However, as  will be shown below, much insight into the
combustion process in a J-33 combustor has been gained.

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                                                            Relief  Valve
Gas Sampling Probe
                                                 Purge  System
                                                                      Unheated
                                                                      Sample
                                                                      Line
                   To Remainder —
                      of Gas
                  Handling System
                  Control Room
       Electrometer
                                            Test Cell
                                                                Heated
                                                                Sample
                                                                Line
                                                                 Bellows  Pump
                                    FID
                                Hydrocarbon
                                 Analyzer
                                                                                             Outside
                                                                                                     Vent
             Span  Zero Burner
             Gas   Gas
Ai r
Figure 2-18.  Hydrocarbon  sample  handling  and  analyzer system

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                                                                       42
                     III.  RESULTS AND DISCUSSION

     In order to Intelligently present the data contained in this section,
it is first necessary to understand generally the basic gas turbine com-
bustion scheme.  Typical gas turbine combustors may be divided into three
characteristic regions as shov/n in Fig. 3-1:  the primary zone, the sec-
ondary zone, and the dilution zone.  The primary zone extends normally
from the fuel nozzle face to the first row of air addition holes and is
the region of most intense combustion.  Typical primary zone equivalence
ratios vary to either side of unity.  The secondary zone serves primarily
to complete the combustion initiated in the primary zone and for this
purpose receives additional air from penetration air jets.  The final
downstream combustor volume is termed the dilution zone.  Its purpose is
to reduce the combustor exit plane bulk temperature through air addition
to an acceptable turbine inlet temperature.
     For the Allison J-33 combustor used in the present investigation, a
NASA air flow program (Tacina and Grobman, 1969) has been used to estimate
that approximately eight percent of the total  combustor air flow enters the
primary zone through the air swirler located around the fuel nozzle in the
combustor dome.  The swirled inlet primary air is characterized by a low
pressure region in the center of the swirl necessary to induce the primary
zone flow recirculation (see Fig. 3-1) required for flameholding.  That
remaining air not entering through the combustor dome is directed into the
combustor either through film cooling slots or through secondary and dilu-
tion air holes.

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             primary combustion   jsecondary combustion
                                    secondary
                                   combustion
                                  i  dilution zone
                    zone
vaporization
    zone      wall
          recirculation
              zone
  central
recirculation
    zone
jet impingement
recirculation zone
                      Figure 5- 1 .   Typical gas turbine combustor flow schematic

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                                                                       44
      The Allison  J-33 combustor  is shown in Fig. 3-2.  Plane "c" in the
 figure  cuts  through  the  first  rov; of secondary air holes and corresponds
 approximately  to  the end of  the  primary combustion zone.  The volume
 contained  between planes "c" and "e" can be considered the secondary com-
 bution  zone, while that  combustor volume downstream of plane "e", the
 dilution zone.  The  three small  holes aligned upstream of plane "c" are
 primary zone air  addition holes  and the intermittently spaced wedges are
 the film cooling  slots.  Finally, the dome cutaway shows the combustor
 fuel  nozzle and air  swirler assembly.
      The four  planes shown in  Fig. 3-2 constitute four of the axial loca-
 tions from which  internal gas  composition samples were taken.  Planes "a"
 and "f", both  not shown  in Fig.  3-2, are located respectively 3 inches
 downstream of  the fuel nozzle  face (i.e. 2 1/2 inches upstream of plane
 "b")  and 1 3/8 inches downstream of the actual combustor exit plane.
 Henceforth plane  "f" will be designated the combustor exit plane.  Total
 combustor length  (from fuel nozzle face to actual combustor exit) is
 approximately  18  5/8 inches.
     As previously mentioned,  the gas sampling probe tip was offset to
 provide a circular trace upon  probe rotation.   Fig.  3-3 shows the location
of the  probe trace in the combustor exit plane sampling station as viewed
 from the combustor dose.  The  relative positions of the combustor cooling
slots,  penetration air holes, and gas sampling probe positions should be
noted.  (It should be mentioned again that the designated combustor exit
 plane is in reality a plane 1 3/8 inches downstream of the actual combustor
exit.)  The 0°, 90° cw (clockwise),  180°,  and  90° ccw (counter-clockwise)

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Figure 3- 2 .   J-33 combustor configuration, gas sampling
       planes (4 of 6), and probe trace position
                                                                                    Ul

-------
                                                                          46
                      Temperature Probe No. 1,
                                          Location No.  1
              Location No. 2  *
Location No. 1
  Temper-
   ature
  Probe
  No.  2      •X-"
      Location No.  2
              View from Combustor Dome
                     Downstream
                                                5.83'
                                                           Jet 5
Jet 4
                                                              2 9/16" Dia.
                                                    Film Cooling Slot
                                                    Secondary Air Hole
                  Figure 3-3.   Relationship of probe  trace
                          and  gas  sampling  points  to
                         J-33  combustor configuration

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                                                                       47
 designations will  be  used consistently to refer to the different radial
 probe  positions  as  shown in the figure.

                      A.  COMBUSTOR OPERATING POINTS

     Having now  established the particular J-33 combustor configuration,
 it is  appropriate  to  detail the selected J-33 combustor operating points.
 For the subject  research combustor air flows of 3.75, 4.57, and 6.0 Ibs/sec,
 combustor absolute  pressures of 3, 5, and 10 atmospheres, and combustor
 overall equivalence ratios of 0.217, 0.283, and 0.345 were used, with liquid
 propane as fuel.  Unheated inlet air was used for the experiments described
 in this section.  Those combinations of the above parameters that were
 investigated are shown graphically in Fig. 3-4 and in tabular form in
 Table  3-1.  The base  combustor operating point corresponded to an airflow
 of 6.0 Ibs/sec, an overall  equivalence ratio of 0.217, and a combustor
 pressure of 5 atmospheres.   It is of importance to emphasize that during
 any run only one parameter was varied from the base condition.  As can be
 inferred from Fig. 3-4, and unlike the technique of Sawyer et al. (1969),
 equivalence ratio variation was accomplished through fuel flow rate alter-
 ation at a constant air flow rate, thus eliminating major concomitant
 primary zone and overall residence time changes.
     Because of time limitations and the unrealistic use of unheated
 combustor inlet air for these experiments, combustor traverses were made
only at the base operating  point, B in Table 3-1.   Measurements at the
other six operating points  were limited to the exit plane.  Due to the
unavailablity of functioning hydrocarbon analyzing instrumentation during

-------
                                                       48
          m   (Ibs/sec)
           a
Figure 3-4.   Combustor operating point matrix

-------
                                                                49
              Table  3-1.   Selected Combustor
                          Operating  Points1^
Fig. 3-4
Point
Designation
A
8**®
C
D
E
F
G
Overall
Equivalence
Ratio
0.217
0.217
0.217
0.283
0.217
0.345
0.217
Air flow
Rate,
Ibs/sec
6.0
6.0
6.0
6.0
4.57
6.0
3.75
Combustor
Pressure,
atm abs
3
5
10
5
5
5
5
Normal Design Operation:
                    0.232f         7.17           4.2
±    For each condition only a single parameter variation
         from the base point was allowed.
A    The acquisition of a complete data set for each
         point required more than one run.
*    Point B is designated the combustor base operating
         point.
®    Combustor traverses were made at this operating
         condition.
t    Calculated for C,Hg as fuel, following Zucrow and
         Warner (1956).

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                                                                        50
 this  portion  of  the  study,  only gas temperatures and carbon monoxide
 and nitric  oxide concentrations will be reported.

                         B.   INTERNAL MEASUREMENTS

      The  long  time required for accurate gas sampling measurements and
 the finite  capacity  of the  air system prevented the completion of a
 combustor traverse during any one experiment;  usually three to five
 runs  were needed.  Generally it was found that reproducibility within
 any given experiment was good, but somewhat poorer from run to run
 at a  given  operating point.  Thus all of the data points obtained inside
 the combustor will be reported below.  The difficulties with gas tempera-
 ture  measurement detailed in Section II prevented our obtaining as many
 local temperatures as concentrations.
      For  these internal measurements the probe was inserted into the
 combustor through the probe  addition section window and stationed at one
 of the planes shown  in Fig.  3-2.  After steady combustion at the base
 operating point  had  been established, measurements were taken at the
 initial probe position.  The probe could then be rotated to any of the
 three other radial positions shown in Fig. 3-2 and 3-3, or translated to
 another axial station.

 1.  Gas Temperatures
     The  internal temperature measurements shown in Fig. 3-5 provide much
 insight into the nature of the flow pattern and combustion process in the
J-33 combustor.  For convenience, the axial profiles at each radial  position
are connected by the heavy lines.

-------
   1700
   1500
   1300
-M
(O
O)
    1100
A    0°
O   90°  cw
D  180°
x   90°
                   ccw
     900
     700
                                     I
                                  I
I
J_
                                     6        8       10        12

                                        Distance from Injector, Inches
                                                             14
                           16
                           18
20
                               Figure 3-5.    Temperature versus  axial  position
                                   (n  = 6.0 Ibs/sec, g = .217,  P = 5  atm)

-------
                                                                        52
      In  the  first  six  inches of  the combustor, the maximum gas temperatures
 are  encountered  near the wall of the combustor (180°) while the recir-
 culation  zone  nearer to the centerline is relatively cold;  this last
 observation  suggests that a large portion of the air injected through the
 first  row of large  penetration holes at 8 inches recirculates back toward
 the  injector.  The  presence of these holes is most clearly seen in the
 180° profile at  about  8 inches,  in the 90° profiles at about 6 inches, and
 possibly  in  the  centerline profile between 4 and 6 inches.  Because of
 the  asymmetry  of the probe position at both 90° cw and ccw with respect
 to the penetration  holes (as shown in Fig. 3-3) these two temperatures are
 never equal;   the  90°  ccw values are generally the lower, due to jet 5.
     The  flame closes  to the centerline between 8 and 10 inches, where the
 maximum temperatures are observed.  Downstream of this station the tempera-
 tures decay  for  the most part as the remainder of the air is added
 through the  holes and  slots.  It thus appears that reaction continues
 well into the  secondary zone of  this combustor.
     One surprising result of the temperature measurements is their low
 values in the first 10 inches of the combustor:  the maximum value of
 about 1600°  K  (on the  centerline at 10 inches) is at least 400° K lower
 than one would expect  theoretically.  However, since the thermocouple
 bead did not melt during the experiments, temperatures on this order could
not have been experienced in any position through which the probe travelled.
     There are several  sources of error in temperature measurements with
 unshielded,  uncoated junctions:   one results from conduction along the
 thermocouple, but is negligible here due to the depth of immersion of the
probe into the combustor.   Catalyzed recombination reactions on the

-------
                                                                        53
 uncoated  Pt  leg would  increase the measured temperature over the gas
 temperature, which  is  the wrong trend.  Radiation heat transfer losses
 from  the  bead  to  the relatively cold combustor walls must also be
 considered.  However,  assuming the bead to have an emissivity of one and
 to be surrounded  by walls at 0° K results in a temperature measurement
 low by only  100°  K for an indicated value of 1600° K (the Nusselt number
 for heat  transfer to the bead is estimated as 43 in the primary zone).
 Thus  radiative corrections have not been applied to the data of Fig. 3-5
 and do not appear responsible for the unexpectedly low temperatures
 which  were measured.
      Most likely  direct impingement and subsequent evaporation of liquid
 fuel  on the  thermocouple bead is the source of the error, particularly
 near  the walls where the hollow fuel spray cone would be expected to
 persist (using rLO injected into ambient air, the spray cone angle was
 measured to be about 80°).  However, since even with this difficulty the
 highest temperatures at 4 inches were observed at 90° cw and 180°, the
 following qualitative  picture of the combustion process can be assembled:
 the flame zone follows the fuel  spray and is hollow in the primary, with
 a relatively cold embedded recirculation zone fed in part by the first
 large  air holes at 8 inches.   The zone ends at about the 8 inch position
where  the flame returns to the centerline.
     Thus the schematic of Fig.  3-1  is a reasonable representation of the
J-33 combustion process if the central and jet impingement recirculation
zones are merged and substantial  combustion is allowed in the secondary
zone.  It is also concluded that the particular 90° radial probe positions
chosen for these experiments  will  not exhibit equal temperatures or

-------
                                                                        54
 concentrations  since  the 90° ccw points are more directly aligned with
 penetration  jets;  as will be shown below, slightly lower NO and CO
 measurements were also obtained at 90° ccw.

 2.   Nitric Oxide
     Axial NO profiles for the four radial positions are presented in
 Fig. 3-6 through 3-9;  due to the large number of data points and
 considerable scatter  four separate figures are shown.  The general order
 of decreasing NO concentrations is 0°, 90° cw, 90° ccw, and 180°,
 respectively.
     High NO concentrations are found on the center!ine in the region
 thought to be within  the recirculation zone (the first 6 or 8 inches
 in Fig. 3-6), but the scatter in the data is also the worst here.  At
 10 inches at 0°, where the maximum temperature was measured, NO also
 reaches its maximum value, falling off downstream probably as a result
of dilution.  The 90° ccw values (Fig. 3-7) are generally lower than
 those at 90° cw (Fig. 3-8) due to the closer proximity to penetration
jets, and as in the temperature profiles, dilution from the first large
jet  (at 8 inches) can be seen at 8 and at 6 inches, respectively.  In
addition, the wall  concentrations (Fig. 3-9) clearly show the influence
of this jet at 8 inches.  Only slight radial variations are seen at 3
inches from comparison of the four figures;  more substantial variations
are exhibited downstream of this point.  The scatter in all of the data
decreases in moving downstream.
     All of the temperatures reported in Fig.  3-5 are too low for signifi-
cant NO formation via homogeneous reactions.  However, the general increase

-------
    25
    20
                                                 A= 0°


                                                 A= Average  Exit
                                                     Plane Value
Q-
O.
C
o
ea
i.

c
QJ
O
c
o
o
    10
                                                                    AA
                                8
                                      10
12
14
16
18
 &
_L_
 20
22
                          Distance from Injector, Inches


            Figure 3-6.   NO concentration versus axial position for Oc

                       (m  = 6.0 Ibs/sec, £ = .217, P = 5 atm)
                        a
                                                                                                      en
                                                                                                      en

-------
    25
    20
                 X  =   90° ccw


                 N  =   Average Exit
                       Plane  Value
o_
D_
c
o
     15
£
C
Ol
 O
O
     10
                               XX
                           1
1
                                       I
                   1
1
1
6     8     10    12    14    16

Distance from Injector, Inches
                                                                18
                                     20
                        22
          Figure  3-7.    NO concentration versus axial  position for 90° ccw

                       (m  = 6.0 Ibs/sec, 0 = .217, P  = 5 atm)
                         a
                                                                                                      en
                                                                                                      cn

-------
   25
   20
                                       o =   90* cw


                                       • =   Average  Exit

                                             Plane  Value
Q_

Q-
o

+J

c
 o
o
   10
                        o
                         O
                          -L
                     _L
                                                 o


                                                 o
                   JL
_L
-L
6      8    10     12      14    16


 Distance from  Injector,  Inches
J_
_L
                                                                18    20
                                                                 22
Figure 3-8.   NO concentration  versus  axial  position for 90° cw

            (m  = 6.0  Ibs/sec,    = .217, P = 5 atm)
              9
                                                                                                         tn

-------
c. *s
20
51
D-
g 15
4J
fO
t-
c
QJ
1 1°
O
0

5

f
D = 180°
• = Average Exit
Plane Value


D
D
a
D
D D D
n ° ° EL
O n r^
D D ™
D
1 1 1 1 1 1 1 1 1 1
2 4 6 8 10 12 14 16 18 20 22
               Distance from Injector, Inches



Figure 3-9.   NO concentration versus axial position for 180'


           (n  = 6.0 Ibs/sec, cj> = .217, P = 5 atm)
             a
en
00

-------
                                                                        59
 in  NO  concentration which  follows the zone of maximum temperature (i.e.,
 3 to 6 inches  at  180°,  Fig. 3-9;  about 7 inches at 90° cw, Fig. 3-8;
 and 8  to  10  inches at 0°,  Fig.  3-6} suggests firstly that NO is still
 forming in this zone and secondly that the measured temperatures are
 low, as was  concluded in the previous section.  The high values of NO
 observed  in  the recirculation zone at the 4 through 7 inch positions are
 most likely  a  result of entrainment into this zone:  although these values
 are suspect  because of  the large scatter in the data, it will be shown
 subsequently that NO is not formed in this region, when the results of
 varying the  air flow rate  are reported.

 3.  Carbon Monoxide
     Semi logarithmic plots of axial CO concentrations are shown as Fig.
 3-10 through 3-13, again grouped by radial probe position.  The high
 concentrations observed at those stations closest to the injector
 suggest that the region in which CO is formed was not accessible to the
 probe, a  finding which  is consistent with the proposed fuel rich zone
 very near the  injector  face.  In addition, the lower values at 180°
 suggest that CO oxidation is still occurring in the primary zone along the
walls;  the  reaction has been quenched in the recirculation zone by the
 cold air flowing upstream from the large penetration jets at 8 inches.
Because of the logarithmic concentration scale, the pattern of this jet
is not as  easily followed as in the temperature and NO concentration
profiles.

-------
                                                                   60
    100,000
     10,000
D-
O-
O
c
CJ
u
c
o
CJJ

o
      1000
       100
                            A
                            A
                                        A
                                        A
                                                       A

                                                       A
                    A=  0°


                    A *  Average  Exit

                        Plane  Value
J	I
J_
I
J	I
I
J	I
                     4        8       12        16


                     Distance from Injector,  Inches
                                      20
      Figure 3-10.   CO  concentration  versus  axial  position for 0'

                 (m   = 6.0  Ibs/sec,    =  .217, P = 5 atm)
                  a

-------
                                                                61




10,000
-r '
Q.
0.
*
c
o
I
J_>
^•*
OJ
o
c
o
CJ
o
1000



100
(
x v
: $
X
X
X

- X
•»
^
X
X
H>
X
••
- XM
x = 90° ccw
H = Average Exit
Plane Value
1 1 1 1 ! 1 1 1 1 1
) 4 8 12 16 20
                 Distance from Injector, Inches



Figure 3-11.  CO concentration versus axial position for 90°  ccv/


             (m, = 6.0 Ibs/sec,  = .217, P = 5 atm)
               a

-------
                                                                      62
    100,000
     10,000
Q.
Q.
-M
re
i.
4->
c
HI
u

o
       1000
        100
o
o
o
0
o
o
o
0
o
o

-
o = 90° a/
• = Average Exit
Plane Value
1 I I I I I t










0
o

1 1 1
                      4        8       12        16


                      Distance from Injector, Inches
20
      Figure 3-12.  CO concentration versus axial  position  for 90° cw

                  (m, = 6.0 Ihs/sec, 4> = .217, P = 5  atm)
                    a

-------
                                                                     63
    100,000
     10,000
£
c
Ol
o
o
       1000
        100
                        =  180°

                        =  Average  Exit

                          Plane -Value
                  I    I    I     I    I    I     I    I    I
                      4        8        12        16



                      Distance  from  Injector,  Inches
20
       Figure  3-13.   CO  concentration  versus  axial  position  for 180C


                  (m  =  6.0  Ibs/sec, <>  =  .217,  P  =  5  atm)
                    a

-------
                                                                       64
 4.   Summary
      The  flow  pattern  in  the  first 10 inches of the J-33 combustor
 postulated on  the  basis of the  temperature and concentration measure-
 ments  is  shown schematically  in Fig. 3-14.  The most important features
 are  the fuel rich  zone along  the dome and liner walls where CO (region
 1) and NO (region  1-3-5)  are  formed and the strong backflow of air
 (region 4) which quenches CO  oxidation in region 2.  It is the lack of
 substantial air addition  into the fuel rich region and too much air
 flow  into the  recirculation zone which is responsible for the high
 emissions of CO from this combustor.  However, since the highest tempera-
 ture  zones are probably fuel  rich, the NO emissions are low.  For this
 particular liner,  the results suggest that the placement of the first
 row of large penetration  holes will largely determine the emissions.

                C.  COMBUSTOR EXHAUST PLANE MEASUREMENTS

     Through internal measurements of temperature and composition the
 influence of liner design on CO and NO emissions has been discussed in
 the previous section;  combustor exit plane measurements are not as
 useful for this purpose because they obscure the important chemical and
 physical  phenomena occurring within the liner.  However, studies of this
 latter type can help reveal  the dependence of emissions on cycle design
 (as opposed to liner design) parameters.   Most of the data to be reported
 in this section pertain to NO and CO emissions as functions of overall
equivalence ratio, combustor pressure, and air flow rate,  but the
 limited temperature measurements obtained with the exit plane chrome!-alumel
thermocouples will be presented first.

-------
1.  Very fuel rich; much CO
    formation; fuel drops
    continue downstream
2.  CO quenched by cold
    recirculating air; NO
    entrained from wall flow
3.  Measured temperatures low
    due to drop impingement;
    some CO oxidation and NO
    formation
                                                                                      Penetration air
                                                                                      feeds recirculation
                                                                                      zone


                                                                                      NO formation
                                                                                      throughout this
                                                                                      high temperature
                                                                                      region 3-5
                                                          8
                      Distance from injector, inches

                   Figure 3-14.   Schematic of postulated primary and secondary
                            zone flow pattern for the J-33 combustor
                                                                                                            01
                                                                                                            in

-------
                                                                       66
 1.   Gas  Temperatures
      Only  the  influence of air flow rate on radial temperature profiles
 was  determined,  for the two sets of probe positions shown in Fig. 3-3.
 The  data for location number one are shown in Fig. 3-15, and those for
 location number  two in Fig. 3-16.  Note that in the former position probe
 one  is aligned with a penetration jet while probe two is midway betv/een
 a jet and  a film cooling slot;  in location number two probe one was
 directly aligned with a slot.
      As  expected, the mean gas temperature is higher when measured above
 a film cooling slot than above a penetration jet:  probe one exhibits
 higher values at both air flow rates in Fig. 3-16 than in Fig. 3-15.
 Probe two  at location two reveals somewhat lower temperatures since in
 this  position it  is closer to a penetration jet (see Fig. 3-3).  The
minima in  all of the curves represent the cores of the last row of pene-
 tration  jets near the end of the liner.
     These radial profiles clearly indicate the difficulty in calculating
a meaningful mass averaged temperature at the combustor exit;  in fact,
Fig.  3-15  and 3-16 suggest that the exhaust temperature decreases with
decreasing air flow rate, which is inconsistent with thermodynamics.

2.  Exhaust Plane Emissions of Nitric Oxide and Carbon Monoxide
      Exhaust plane concentration data as functions of the cycle design
parameters air flow rate, overall  equivalence ratio, and combustor
pressure will be presented in two ways:  firstly, numerical averages at
each radial position will be shown, and secondly, in order to demonstrate
the reproducibility of the measurements, all data will be shown.  Recall

-------
                                                             67
1123
1073
                                                      57  Ibs/sec
                                                     75  Ibs/sec
                                                      75 Ibs/sec
                                              Temp.  Probe One
                                              Temp.  Probe Two
                                           •  Temp.  Probe One
                                           X  Temp.  Probe Two
 623
                .5         1.0         1.5         2.0        2.5
                   Radial Distance from Combustor Wall  (Inches)
        Figure 3-15 •   Combustor exit plane temperature traverse
           (probes  in  locations  numbered  one  in  Fig.  3-3)

-------
                                                                    68
     1073
     1023
     973
     923
cu
E
o
     873
     823
     773
     723
     673
     623
     573
            m =3.75  Ibs/sec
             a
                                                         m =3.75 Ibs/sec
                                                          3-
                                           Temp.  Probe One


                                           Temp.  Probe Two

                                        •  Temp.  Probe One
          .5         1.0         1.5           2.0


          Radial Distance from Combustor Wall  (Inches)


Figure 3-16. Combustor exit plane temperature  traverse


   (probes in locations numbered two  in Fig.  3-3)
                                                                       2.5

-------
                                                                        69
 that only one  cycle  parameter was varied at a time, as shown in Fig. 3-4,
 in  order to  obtain these  data.

 2.1   The Influence of Air Flow  Rate
      Since the  air flow rate was varied at constant overall equivalence
 ratio (and pressure), it  was necessary to vary the fuel flow rate
 accordingly.  This was accomplished by changing the fuel differential
 injection  pressure.  Thus  in interpreting the effects of air flow rate
 on  NO and  CO emissions it may be necessary to consider changes in
 atomization and spray penetration as well as in primary zone and over-
 all  residence times.
      As  shown in Fig. 3-17 and  3-18, only a slight decrease in NO concen-
 tration  occurs  with  a 60%  decrease in air flow rate from the base
 condition;  this result indicates that either the residence time in those
 zones  responsible for NO  formation does not change greatly, or liquid
 droplet  combustion is the  predominant source of NO and remains relatively
 unchanged  throughout this  set of experiments.
      CO  emissions demonstrate a more interesting behavior and are displayed
 in Fig.  3-19 and 3-20.  A  general decrease is observed in passing to the
 lowest air flow rate tested, particularly on the centerline and at 90° cw.
At first these  results seem inconsistent with the NO results, but both
 can be explained in terms  of Fig. 3-14.  It has been hypothesized that
zone  1 is the predominant  region of CO formation and zones 1 and 3 of NO
formation.  Since NO formation does not change appreciably with air flow
rate, the flow pattern must remain essentially the same in zones 1  and 3.
The decreased CO emissions at 3.75 Ib/sec can then be attributed to poorer

-------
                                                                  70
    32
    28
    24
s:   20
Q.
O
a
s-
4J
C
O
O
c:
o
CJ
16
    12
          =   .217

         P = 5 atm
A    0°
o   90° cw
a  180°
x   90° ccw
                         m  , Ibs/sec
                          a

    Figure 3-17.  Radial NO concentrations  at  combustor

          exit plane versus air flow rate  (average)

-------
                                                                 71
Q.
Q_
O
c
Ol
u
o
    32
    28
    24  L.
20
    16
    12
            cj> =  .217

            P = 5 atm
            Average Values
               Connected
o
a
                 0°
                90° cw
               180°
                90° ccw
                         m , Ibs/sec
                          a
     Figure 3-18.   Radial NO concentrations at combustor

                exit plane versus  air flow rate

-------
                                                                 72
   10,000
OH

a.
o
•H
(3

-------
                                                                   73
    10,000
a.
a.
c
o
c
o
CJ

o
u
                 P   ,  = 5 Atm
                  comb


                   4o  = .217
     1,000
       100
                                           A    o°

                                           O   90°cw

                                           a   180°

                                                90°ccw
                                        Average Values

                                          Connected
                             m ,  Ibs/sec
                              3.
       Figure 3-20,
Radial CO concentrations at corabustor  exit

 plane versus air flow rate

-------
 quenching  of  the  CO  oxidation  in zone 2 and results from less penetration
 air  from zone 4 getting  to zone 2 at the low air flow rate.  At higher
 flow rates, approaching  the design point of 7.17 Ib/sec, the particular
 design  of  the J-33 can prevent substantial variations in primary zone
 residence  time.   These conclusions are also consistent with the postulate
 that the high NO  concentrations in zone 2 (see Fig. 3-6) result from
 entrainment from  zones 1 and 3 rather than NO formation in zone 2, since
 higher  NO  emissions  v/ere not observed at the lowest flow rate.
      If this  behavior were characteristic of combustors other than the
 J-33 liner, then  it  could be used to reduce CO (and probably HC) emissions
 at aircraft low speed ground idle and at automotive idle.  While main-
 taining an overall equivalence ratio close to the design value, compressor
 bleed air  flow could be  increased to prevent quenching of the CO oxidation
 reaction in the combustor.  The penalty for this method of emissions
 control would be  an  increased fuel consumption at idle.

 2.2  The Influence of Overall Equivalence Ratio
     The primary  effect of an increase in overall equivalence ratio would
be a change in the temperature in zones 1 and 3 of Fig. 3-14:  if these
zones were predominantly lean, then an increase in temperature and NO, and
 little  change in  CO would result;  if rich,  then temperature and HO would
decrease while CO increased.  On the other hand, if droplet combustion
were important then NO (and possibly CO) should increase simply as a
result of the presence of more droplets.  Of minor significance would be
a slight decrease in primary zone residence  time due to the increased
fuel  flow rate.

-------
                                                                       75
      The  results  of  a  change  in equivalence ratio are shown in Fig. 3-21
 through 3-24,  and it is observed that both NO and CO increase strongly
 with  overall equivalence ratio.  Most likely this results from the droplet
 effect noted above;  the CO increases as well because zones 1 and 3 are
 predominantly  rich.  Both the presence of droplets and the lack of
 sufficient air for complete combustion in these regions are entirely
 consistent with the  other observations which led to the model depicted
 in Fig. 3-14.

 2.3   The  Influence of  Combustor Pressure
      The  final cycle parameter which was varied was combustor pressure,
 at constant air flow rate and overall equivalence ratio;  the results
 of this study  are  shown in Fig. 3-25 through 3-28.  An increase in
 pressure will  increase the homogeneous rate of NO formation and both
 CO formation and  oxidation.   In addition, small decreases in fuel spray
 cone  angle and atomization may result.
      In Fig. 3-25  and  3-26 it is seen that a substantial increase in NO
 occurs with increasing pressure at all radial probe positions:  the
mass-averaged NO  concentration increases from 3 ppm at 5 atm to 11 ppm
at 10 atm, a factor of 3.67.  If one assumes that the Zeldovich mechanism,
with 0/02 equilibrium and N atoms in steady state, describes the gas-phase
NO formation kinetics, then it can be shown that the rate of formation
of NO increases with pressure to the 1.5 power;  in other words, on the
basis of homogeneous kinetics and under the assumption that the tempera-
ture and residence time in the NO forming region are  relatively
unaffected by total combustor pressure, the NO concentration at 10 atm

-------
                                                                  76
    32
    28
    24
£   20
D-
C
o

4J
<0

4J
c
o
u

o
o
16
    12
     8  -
     4  -
     0
.20
         m, = 6.0 Ibs/sec
          a

         P  = 5 atm
        A     0°

        o    90° cw
        D   180°
        x    90° ccw
                                                 .35
                      .25            .30


                   Overall  Equivalence Ratio


     Figure 3-21.  Radial NO concentrations at combustor

     exit plane versus overall  equivalence ratio (average)

-------
                                                                  77
Q.
Q.
ra
i.
4J
o
o
    32
    28
    24
20
16
    12
     0
.20
       rn  = 6.0 Ibs/sec
        a
       P  = 5 atm


       Average Values
          Connected
           o
           D
                0°
               90° cw
              180°
                     90° con
                                                .35
                .      .25            .30

                  Overall Equivalence Ratio

    Figure 3-22.  Radial NO concentrations at combustor

        exit plane versus overall equivalence ratio

-------
                                                                 78
c
o
   15,000


   14,000

   13,000

   12,000

   11,000


   10,000

    9,000

£   8,000


o   7,000
o
o   6,000
u

    5,000


    4,000

    3,000


    2,000 —

    1,000 —

         0
               m  = 6.0 Ibs/sec
                a
          —   P  = 5 atm
                     A
                     O
                     n
                     x
  0°
 90°cw
180°
 90°ccw
                     .217
         .283
                                                 .345
                    Overall Equivalence Ratio
         Figure 3-23.  Radial CO concentrations at the
               combustor exit plane versus overall
                   equivalence ratio  (average)

-------
                                                                  79
    15,000


    14,000

    13,000

    12,000

    11,000

|   10,000

o    9,000

£    8,000
c

g    7,000
u
o
u
6,000

5,000

4,000

3,000

2,000 —

1,000 —
         (H
                      A    0°
                      O   90°cw
                      n  180°
                      X   90°ccw
                 m  = 6.0 Ibs/sec
                  a
                 P  = 5 atm
                                             A
                     .217           .283         .345

                    Overall Equivalence Ratio

           Figure 3-24.  Radial CO concentrations at the
                    combustor exit plane versus
                    overall equivalence ratio

-------
                                                                  80
Q.
D_
CJ
O

O
O
    32
    28
    24
    20
O
£  16
12
     8
     4    -
             =  .217
           rci  = 6.0  Ibs/sec
            a
            A    0°
            o   90° cw
            a  180°
            x   90° ccv/
                        4      6        8      10

                     Combustor Pressure, Atm
                                                  12
       Figure  3-25.   Radial  NO  concentrations  at  combustor
              exit plane  versus  pressure  (average)

-------
                                                                   81
O
ra
O)
o
o
o
     32
     28
    24
    20
     16
    12   .
     8   -
     4  u
     0
  =  ,217

ITL = 6.0 Ibs/sec
 a

Average Values
   Connected
 A    0°
 O   90° cw
 a  180°
 x   90° ccw
                                              10
                                      12
          2      46      8

              Combustor Pressure, Atm

Figure 3-26.  Radial NO concentrations at combustor
            exit plane versus pressure

-------
   10,000-
               4>o  =   .217


               m   =  6.0  Ibs/sec
               3.
                                                                 82
cu
ex,
o
•H
O
O
c
o
u

o
u
    100L
                    90°ccw
            Average Values

              Connected
              2      4       6       8     10


                   Combustor Pressure, Atm



    Figure 3-27.  Radial CO  concentrations  at  combustor

              exit plane versus pressure (average)

-------
                                                                     83
   10,000
c
o
•H
rt
o
o
    1,000
     '
              0o  =  -217
           „,  m  =6.0 Ibs/sec
       100 '-•-•
                             •;•.•}--•

                                  \
                                             A
                                            O

                   A   o°
                   O   90°cw
                   n  180°
                   X   90°ccw
                Average Values
                  Connected
                        ]       3       3.       f
                        4       6       8     10
                       Combustor  Pressure,  Atra
        Figure 3-28.   Radial CO concentrations at combustor
                      exit plane versus pressure

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                                                                       84
 should  be  only  about  2.8  times  that at 5 atm.  Thus the observed increase
 cannot  be  explained on  the basis of homogeneous kinetics.
      In holding the fuel  flow rate constant as the pressure was increased,
 it was  generally found  necessary to decrease the pressure drop across
 the  injector.   Consequently, larger fuel droplets capable of forming in-
 creased concentrations  of NO were probably present at the higher pressures.
     The CO exhaust plane data  are shown in Fig. 3-27 and 3-28 and do not
 show a  single trend with  increasing pressure:  the center!ine concentration
 increases  as the  wall value decreases.  These observations are attributed
 to a decrease in  injector spray cone angle with increased pressure and are
 consistent with  the combustion  model shown in Fig. 3-14.

                          D.  OTHER PARAMETERS

     The heat release rate and  combustion intensity are not parameters
 that can be varied independently of others such as combustor pressure,
overall equivalence ratio, and  air flow rate once the combustor geometry
and fuel are defined.  Consequently, since the experimental  investigation
discussed  here employed a J-33  combustor burning liquid propane, the
isolated effects  of heat  release rate and combustion intensity on
pollutant  emissions were  not determined.

                                E.  SUMMARY

     In summary, the temperature and concentrations of CO and NO at
various axial  and radial  positions within the J-33 combustor have been

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                                                                       85
presented and discussed.  These profiles are similar to those reported
by Sawyer et al. (1969) but definitely show the effects of the particular
J-33 combustor configuration.
     Having acquired some fundamental information concerning the
internal combustor mechanisms responsible for the net CO and NO emissions
(at the base operating point), the effects of combustor pressure, overall
equivalence ratio, and air flow rate were isolated insofar as possible
and measured at the combustor exit plane.  General support was obtained
from these data for the model of the combustion process in the 0-33
combustor which had been postulated on the basis of the internal measurements

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                           IV.  FUTURE EFFORTS

     Emissions studies of the J-33 combustor using unheated inlet air were
reported in Section III;  however, as noted previously these results
constituted only a preliminary effort due to this unrealistic combustor
inlet temperature.  Gas turbines under consideration as alternatives to the
internal combustion engine in automobiles are of the regenerative type, and
the trend 1n aircraft engines is to higher compression ratios.   Thus it
is of interest to add air inlet temperature to those cycle design
parameters which can be varied in the experimental facility.
     To this end the double combustor facility shown in Fig. 4-1 has been
constructed.  The first J-33 combustor is used as an air heater for a
second J-33 mounted downstream.  Although the heated air will contain
pollutants, at levels of contamination similar to those reported in the
previous section, since the primary purpose of the facility is  to indicate
trends in emissions as functions of cycle and combustor design  parameters
(as opposed to absolute or baseline values) the use of vitiated air is
considered acceptable.
     For assistance in evaluating the performance of the double combustor
facility in meeting the objectives mentioned above, a few experiments
have been conducted to date.  Because these runs were of an exploratory
nature and the data are not complete, the successful operation  of the
facility is of more interest than the actual data to be reported here.

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A1r System
                       Fuel System
                                  J-33 Heating
                                   Contustor
                                                  Fuel System
                                                                J-33 Test
                                                                Combus tor
                                                                                 Probe Addition Section
                                                                                           Back Pressure
                                                                                               Valve
                                                                          Vobe
                                                                        Posi tioner
                           Figure  4-1.   Complete combustion facility schematic
                                                                                                              CD

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                                                                       88
     The probe  addition section and back pressure valve were mounted
at the exhaust  flange of the second J-33 combustor, and the gas sampling
probe was placed at  the exit plane of the test combustor.  Although the
thermocouple portion of the probe was destroyed during one overly long
and hot Ignition transient, the gas sampling probe has withstood over
one-half hour at this station to date.  We are presently replacing the
Pt/PtRh couple.
     A gas sampling  rake and chrome!/alumel thermocouple rake for
mounting in the diffuser section just upstream of the test combustor
are under construction but were not available for the emissions measured
to date;  thus the data to be reported are composites for both combustors.
In later studies the rakes will provide for null measurements to obtain
the true emissions from the test combustor.
     In Table 4-1 are presented those data obtained to date for the follow-
ing run conditions for the test combustor:  air flow rate 6 Ib/sec,
combustor pressure 3.4 atm abs, overall equivalence ratio 0.217, and
Inlet air temperature 630° K.  Without the null measurement to be provided
by the rakes, no attempt will be made to discuss these preliminary
emissions data since the equivalence ratio and pressure for the first or
heating combustor do not correspond to any of the operating points listed
in Section III.  To repeat, the purpose of this experiment was simply to
gain experience with the complete facility and associated instrumentation
(including the FID hydrocarbon analyzer).
     After the gas sampling and temperature rakes are Installed upstream
of the J-33 test combustor, detailed gas sampling (including CO, NO and HC)

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                                                               89
    Table 4-1.  Operating Point and Emissions Obtained
           from Two J-33 Combustors in Series*

Air Flow Rate                             6.0 Ib/sec
Combustor Pressure                        3.4 atm abs
Overall Equivalence Ratios
     First or Heating Combustor           0.130
     Second or Test Combustor             0.217
Inlet Temperature to Test Combustor1      630° K (680° F)
Pollutant        Radial Probe Position at Test Combustor
                              Exhaust Plane

                 0°      90° cw      90° ccw      180°
NO, ppm
CO, ppm
HC, ppm CH4
1.89
2250
950
2.61
1800
400
1.61
4500
2600
1.43
2020
1000
* Emissions are composites for both combustors.
± Calculated following Zucrow and Warner (1956).

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                                                                       90
 and  temperature  measurements  are  to be made at various stations within
 the  test  combustor as  functions of four overall cycle design parameters:
 inlet  air temperature, combustor  pressure, equivalence ratio, and air
 flow rate.   Each parameter will be varied independently from a standard
 run  condition.
     The  possibility of N(L formation in the combustor is a point of
 current discussion.  Significant  amounts of N(L have recently been found
 1n the exhausts  of commercial  and military jet engines, particularly at
 idle (Anon.,  1971,  Hare et al., 1971 and Vaught et a!., 1971).  These data
 were obtained primarily by use of the NCL-^O converter in conjunction with
 a chemiluminescent  NO  analyzer.   In view of the possibility of catalytic
 decomposition of NO by these  converters (see Appendix A), the observation
 of N02 by Hare et al.  (1971)  is questionable since only the converter and
 a chemHuminescent  detector were  used in the study to obtain NO  concen-
                                                               A
 tratlons.
     More confidence can be placed in the results of Airesearch (Anon.,
 1971)  because they also used  a NDUV analyzer at selected points to measure
 N02  directly.  They noted that "a check of several test power settings
 using a NDUV  analyzer  ... confirmed the magnitude of NO,, readings received
 on the chemiluminescent analyzer,"  but apparently no quantitative
 comparisons are  presented in  their report (Anon., 1971).
     Detroit  Diesel Allison (Vaught et al., 1971) compared NO as obtained
on a NDIR analyzer with that  from a chemiluminescent analyzer and generally
 found agreement within  10%.   However, total NO  from a converter-chemilu-
                                              A
minescent analyzer was  considerably less than that obtained with the

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                                                                       91
 Saltzman method  (27%  less at low speed ground idle and 6% less at take-off
 for the T-56 engine).  Note that if the converter is destroying NO, as
 well as converting N02 to NO, a lower NOX would be obtained with the
 chemiluminescent analyzer.
     The present investigation after completion of the J-33 study will
 turn to measurements  at the exhaust plane and within an Allison T-56
 combustor, particularly with respect to independent verification of the
 reported N02 levels (Vaught et al., 1971), as well as the Identification
 of those zones within the combustor which are responsible for the
 production of N02.  Instrumentation will consist of the converter-chemilu-
 minescent analyzer for NO and NO , and it is hoped that these data can be
 substantiated via the NDUV method for N02.  CO, HC, and temperature
 measurements will be made simultaneously with the N0x surveys.
     Although it will probably not be possible to simulate T-56 low speed
 ground Idle 1n the facility due to flameholding requirements in the
 heating combustor, since substantial N02 was observed at all of the
engine operating points (Vaught et al., 1971), it is felt that a reasonable
simulation of the T-56-A-15 operation and investigation of N02 formation
in the combustor can be accomplished.
     Another study which 1s planned 1s to use a gaseous rather than liquid
fuel;   an example of the success of this technique for emissions reductions
is the widespread use of natural gas in stationary combustion systems as
a short range method of reducing pollution.   For the aircraft or automotive
turbine engine, however, natural gas is not a practical fuel, and thus
prevaporlzing burners represent one compromise design (see for example

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                                                                       92
 Zwlck  et  a!.,  1971,  for  a Rankine cycle application).
     In spite  of  this  concensus, there has been no demonstration of the
 importante  of  heterogeneous effects with regard to emissions presented
 in the open literature for a current combustor can (Hellor, 1971).  The
 Berkeley  group (Sawyer et a!., 1969, Starkman et al., 1970, and Parikh
 et al., 1971)  has shown  that gaseous methane produces less HC, CO, and
 NO than liquid heptane,  when burned in a model laboratory combustor.
 However,  Inlet conditions to the combustor were not realistic (room
 temperature air and  pressure only slightly in excess of atmospheric),
 and not only the  physical state, but also the chemical nature of the fuel
 was changed as  well.
     It is  apparent  that a controlled investigation of the effect of
 using gaseous  rather than liquid fuel is needed.  It is proposed here
 that the experiments carried out with the T-56 combustor be repeated
 using gaseous  propane  fuel.  Internal and exhaust plane surveys of tempera-
 ture, HC, CO, NO, N02, and NOX will again be made.
     In sunuiary, the experimental setup using a single J-33 combustor or
 two combustors  in series has proven to be operable.  Preliminary data have
 been obtained,  but interesting and important investigations are left to
 be carried  out.  Future  efforts are to include the study of a high inlet
 temperature  combustor, the investigation of NOg formation in combustors
with emphasis on the T-56 can, and a determination of the effect on
 pollutant emissions when gaseous fuel rather than liquid fuel is used.

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                                                                      93
                          LIST OF REFERENCES
Anon., 1971, "Exhaust emissions test-Airesearch aircraft propulsion
and auxiliary power gas turbine engines," Report GT-8747-R,  Airesearch
Manufacturing Co. of Ariz.

Chase9 J. 0. and Hurn, R. W., 1970, "Measuring gaseous  emissions  from
an aircraft turbine engine," SAE Paper 700249.

Fontijn, A., Sabadell, A. J., and Ronco, R. J., 1969, "Feasibility
study for the development of a multifunctional emission detector  for
air pollutants based on homogeneous chemiluminescent gas phase  reac-
tions," TR-217, AeroChem Research Laboratories.

Fontijn, A. Sabadell, A. J., and Ronco, R. J., 1970, "Homogeneous  chem-
iluminescent measurement of nitric oxide with ozone," Anal.  Chem.  42,
575.

Fontijn9 A., 19719 AeroChem Research Laboratories, Personal  communica-
tion to A. M. Mel lor.

Hare, C. T.s Dietzmann, H. E., and Springer, K. J., 1971, "Gaseous emis-
sions from a limited sample of military and commercial  aircraft turbine
engines," Report AR-816, Southwest Research Inst.

Hodgesone J. A. „ Bell, J. P., Rehme, K. A., Krost, K. J., and Stevens,
R. K., 1971t "Application of a chemiluminescence detector for the  meas-
urement of total oxides of nitrogen and ammonia in the  atmosphere,"
AIAA Paper 71-1057.

Mellor, A0 M.9 19719 "Current kinetic modeling techniques for continuous
flow combustors," Emissions from Continuous Combustion  Systems  Symposium,
General Motors Research Laboratories.

Nelson, A. W., 1972, "Collection and assessment of aircraft  emissions
baseline data - turbine engines," Report PWA-4339, Pratt and Whitney
Aircrafts United Aircraft Corporation.

Owens, C. W.  and Mellor, A. H., 1971, "An investigation of gas  turbine
combustors with hiqh inlet air temperatures.  Second Annual  Report:
Part II:  Heat Transfer," TM-71-2, Jet Propulsion  Center, Purdue  Univer-
sity, USA TACOM Report No. 11328.

Owens, C. W., 1972, "Heat transfer in high temperature  gas turbine
combustion chambers," M.S.M.E. Thesis, Purdue University.

Parikh, P. G., Sawyer, R. F., and London, A. L., 1971,  "Pollutants from
methane fueled gas turbine combustion," College of Engineering Report
No. TS-70-15, University of California, Berkeley.

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                                                                     94
Sawyer, R. F., Teixeira, D. P., and Starkman,  E.  S.,  1969,  "Air pol-
lution characteristics of gas turbine engines," ASME  Trans.,  J.  Eng.
Power, 91_, 290.

Starkman, E. S., Mizutani, T., Sawyer, R.  F.,  and Teixeira, D.  P.,
1970, "The role of chemistry in gas turbine emissions,"  ASME  Paper
70-GT-81.

Tacina, R. R. and Grobman, J., 1969, "An analysis of  total  pressure
loss and airflow distribution for annular gas  turbine comb us tors,"
NASA TN D-5385.

Vaught, J. M., Parks, W. M., Johnsen, S. E. J., and Johnson,  R.  L.,
1971, "Final technical report collection and assessment  of  aircraft
emissions base-line data-turboprop engines (Allison T56-A-15),"  Report
EDR 7200, Detroit Diesel Allison Division, General  Motors.

Zucrow, M. J. and Warner, C. F., 1956, "Constant  pressure combustion
charts for gas turbines and turbojet engines," Purdue University
Engineering Experiment Station Bulletin No. 127.

Zwick, E. B., Mills, T. R., and Fio Rito,  R.,  1971, "Evaluation  of  a
low NO  burner," Report USG-1, Paxve, Inc.

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                                                                      95
                              APPENDIX A
                     EFFECT OF NOg CONVERTER ON NO
     A NOp converter was added to the nitric oxide detector system so
that the existing chenriluminescent NO detector could be used to meas-
ure the NOp concentration of the sample gas.  In principle, the con-
verter operates by heating the sample gas to a sufficient temperature
(approximately 600° C) such that the N02 will dissociate to NO.  The
NOp converter-NO system is shown schematically in Figure 2-15.  Paral-
lel flow paths to the NO detector are provided for the sample:  one
goes directly to the detector and the second passes through the con-
verter.  By intermittently changing the flow path taken by the sample
gas, the concentrations of NO and NO  can alternately be recorded.
                                    /\
The total NOp concentration is then the difference between the alter-
nating concentration levels.
     The converter was constructed according to specifications fur-
nished by the Environmental Protection Agency, which called for six
feet of one-eighth inch by .028 inch wall 316 type stainless steel
tubing.  The tubing was resistance heated by flowing an electric cur-
rent directly through it.  A thermocouple was attached to the tube
so that the tube temperature could be continuously monitored.
     No NOp concentration measurements were recorded, as preliminary
testing showed that the NO concentration in a 215 ppm sample gas (bal-
ance Np) was greatly reduced when the gas was flowed through the con-
verter.  It was observed that an increase in the converter temperature

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                                                                      96
from 23° C to 600° C was accompanied by a decrease in the NO concentra-
tion level recorded by the chemiluminescent detector.  Similarly,  the
recorded concentration level rose with decreasing converter temperature.
The recorded results for four individual runs are shown in Fig.  A-l.
The slopes of the curves of Fig. A-l depend upon the rate of temperature
increase, with run one having the highest rate.  The lowest concentra-
tions recorded are within an order of magnitude of the dark current of
the detector.
     In experiments using a commerical chemiluminescent detector with
a similar converter, reported quite recently by Nelson (1972), similar
irreproducible effects were observed with the "unconditioned" converter
when either NO in Np or N02 in air was flowed through the system.   Con-
verter conditioning was accomplished by repeated exposures to NO  with
                                                                A
the converter at high temperature.
     It is presently thought that the observed results can be attributed
to a surface catalytic reaction along the walls of the stainless steel
tubing (Fontijn, 1971).  Such a reaction is consistent with the lack of
reproducibility shown in Fig. A-l, the dependence on applied heating
rate, and the failure of Hodgeson et al. (1971) to find a similar effect
for samples containing less than 1 ppm NO.

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      1.0
c
o
•iH
•M
rt
(H
U

3


tN



OS



O
4)
O
C
O
u
  o

  o
  u
      o.i —
                                     Inverse Temperature  (°K~   x  10  )


                     Figure  A-l.   Normalized concentration versus  inverse temperature
                                                                                                           VO

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