EPA- The utilisation of alcohol in
460/3- light duty diesel engines
81-
010
RICZIRDO
CONSULTING ENGINEERS
Report No. EPA-*t60/3-8l-010
THE UTILISATION OF ALCOHOL IN LIGHT
DUTY DIESEL ENGINES
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Ricardo Consulting Engineers Ltd.
Bridge Works Shoreham-by-Sea
Sussex BN4 5FG England
28th May 1981
Report No. EPA-fr60/3-8l-010
THE UTILISATION OF ALCOHOL IN LIGHT
DUTY DIESEL ENGINES
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THE UTILISATION OF ALCOHOL IN LIGHT DUTY DIESEL ENGINES
SUMMARY
This report reviews the various approaches which can be employed to
facilitate the utilisation of alcohols - methanol and ethanol - in light
duty diesel engines. The characteristic problems and the relative advantages
of each approach are discussed. "It is concluded that successful application
to an engine of any of the available systems would require considerable
development efforts. The choice of which system to employ is likely to be
most heavily influenced by the proportion of alcohol substitution which is
required and the resulting engine first cost penalty which is deemed to be
acceptable.
Alcohol utilisation by more or less conventional spark ignited engines
appears to be far less problematical than conversion of diesel engines.
1. INTRODUCTION
With the rapidly rising cost of conventional, petroleum based road
fuels and increasing uncertainty with regard to their future supply, con-
siderable interest is currently being taken in alternative fuels. Alcohols,
particularly methanol and ethanol, have some characteristics which are
desirable in future alternative road fuels - they can be produced from a
variety of raw materials (some of which are renewable), suitable production
technology already exists, they can be easily transported and their storage
and handling poses,relatively few health and safety problems. Unfortunately
alcohols also have some disadvantages when compared with both conventional
gasoline and diesel fuel, many of the problem areas are associated with
those properties of alcohols which adversely affect their combustion
characteristics and hence affect aspects of the performance of any engines
in which they are utilised.
The purpose of this report is to examine the suitability of alcohols,
particularly methanol, for use as fuels in diesel engines employed in light
duty vehicles. Various methods by which alcohols can be used in diesel
engines have been investigated and are described in the literature, most of
the reported work has been associated with relatively large cylinder dis-
placement, direct injection (Dl), engines intended for heavy duty applica-
tions; nevertheless consideration of the published data permits an
appreciation to be gained of the likely performance of light duty diesel
engines when operating on alcohol fuel.
2. PROPERTIES OF ALCOHOLS
The chemical and physical properties which influence their suitability
as fuels for diesel engines have been thoroughly examined and are well
documented, see Table 1 (mainly from references 1 and 2).
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The energy content and the relative densities of alchols are con-
siderably lower than the corresponding figures for conventional diesel
fuels. Hence a greater volume of alcohols (in the ratio 2.5:1 for methanol
and 1.8:1 for ethanol) is necessary to provide the same amount of energy as
unit volume of diesel fuel. This implies that engine fuel consumption will
be considerably higher than using aicohol fuels and that changes in fuel
metering systems will be necessary.
Stoichiometric air/fuel ratios are considerably different for diesel
fuel, methanol and ethanol (approximately 14.8, 6.*» and 9.0:1 respectively).
This fact, combined with the differences in the specific energy content of
the fuels, implies that for equal equivalence ratios all the fuel/air
mixtures will have an approximately equal energy content. Hence an engine
operating at a particular condition on any of the fuels should deliver the
same power output.
The self ignition characteristics of fuels greatly influence their
suitability for use in diesel engines. Diesel fuels for road vehicles
normally have cetane numbers in the range k5-60; direct determination of
the cetane number of alcohols using conventional methods is not possible
but the testing of fuel blends and subsequent extrapolation of the results
suggests that the cetane numbers of methanol and ethanol are around 3 and 8
respectively (l). With such low ratings auto-ignition of pure alcohols in
a diesel engine is very difficult.
One reason for the low cetane numbers of alcohols is their high
latent heat of vaporisation, 3-5 x greater than that of typical diesel fuel.
Evaporation of a stoichiometric mixture of diesel fuel and air will cause a
drop in mixture temperature of about 17°C: corresponding figures for
methanol and ethanol are respectively about 200°C and 110°C. This large
difference between alcohols and diesel fuel obviously poses problems in
diesel engines since proper engine operation relies on the rapid auto-
ignition of the fuel following its injection into the air in the cylinder.
Unlike conventional diesel fuel alcohols have very poor lubricity and
hence there is a risk of high wear rates occurring in certain components of
an engine's fuel system, particularly the high pressure fuel injection pump,
which normally rely on the fuel for lubrication. This problem can usually
be overcome, either by component design changes or by the use of suitable
fuel additives (3. 5).
Alcohols cause degradation of many of the materials commonly used in
vehicle fuel systems (6-15). Many metals are subject to corrosive attack
and elastomers and similar materials may swell and/or soften. Methanol
appears to be more of a problem in this respect than does ethanol. Corro-
sive attack by alcohols is accelerated in many instances when water is
present.
In high pressure fuel injection systems such as those used in diesel
engines the properties of the fuel, e.g. density and bulk modulus, which
affect its characteristics as a hydraulic fluid can have a profound effect
on the overall performance of the system. The density and bulk modulus of
both methanol and ethanol are considerably different to those of conven-
tional diesel fuel hence problems such as cavitation in fuel lines and
injection nozzles often occur when using alcohols (h). These problems can
usually be overcome by changes to the hydraulic characteristics of the fuel
injection system.
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Blends of conventional petroleum based fuels and alcohols tend to be
very unstable in the presence of very small quantities of water (16) readily
separating into their constituent parts. Various techniques may be employed
in order to maintain a more stable blend e.g. mechanical emulsifiers (17),
chemical additives (18, 19) or ensuring the complete absence of water from
the blend (20).
3. METHODS OF UTILISATION
3.1 Direct Injection
As noted above both methanol and ethanol have very low cetane numbers
and hence their use in a diesel engine without some additional aid is not
generally possible. For successful operation of a diesel engine with
direct injection of a single, basically alcohol, fuel it is necessary to
significantly increase the cetane number of the fuel, this may be accom-
plished by using either (a) a special cetane improving additive or (b) by
blending the alcohol with a sufficient quantity of conventional diesel fuel
(notwithstanding the problems associated with preventing separation or such
blends). Other techniques which are not discussed here include use of
blends of alcohol and vegetable oils or three component blends of alcohol/
vegetable oil/diesel fuel (19, 21), and use of increased engine compression
ratio (which raises the temperature of the air in the cylinder prior to
injection of the fuel).
a) Alcohol + Cetane Improving Additive
For many years it has been known that various chemicals have the
ability to increase the cetane number of fuels to which they are added (22).
Most such additives function primarily by reducing the time required for the
chemical reactions which must occur during the delay period between the
start of fuel injection and the establishment of combustion; some additives
also have a beneficial effect on the physical processes - fuel atomisation
and local mixture preparation - which must occur during the delay period
(23). In either case the effect of the additive is to shorten the ignition
delay period, hence improving the cetane number of the fuel. Unfortunately
it is usually necessary to use quite a high proportion of additives in order
to increase the cetane number of alcohol fuels to a reasonable level, Fig. 1
shows some relevant results (3, 2^). It is worth noting that as the load on
an engine is reduced a greater proportion of ignition improving additive is
required (Fig. 1(b)). Such additives are relatively expensive and the
logistics of the supply of a fuel comprising alcohol + cetane improving
additive require careful consideration; various strategies are possible,
inc lud ing
i] Provision of a single pump unit at retail outlets dispensing 'neat'
alcohol. Such a fuel could be used directly in spark ignited engines
but would require the addition of cetane improver before it could be
utilised in diesel units.
ii] Distribution and retail supply of two alcohol fuels, one being 'neat'
alcohol for use in spark ignited engines. The other being alcohol +
cetane improver for diesel use.
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Strategy [i] is attractive from the point of view of the fuel production
and distribution industry but requires the addition of a supplementary
cetane improver tank and metering/mixing systems on diesel powered
vehicles. Strategy [ii] is fine for vehicle manufacturers and users but
poses problems for the fuel supply industry.
It is usually possible to offset to some extent the effects of low
cetane number by adjusting fuel injection timing. Retarding the timing may
ensure that the fuel is injected when the temperature of the air in the
engine cylinder is close to its maximum value so that fuel evaporation and
ignition occurs more rapidly; advancing the timing so that injection of
fuel commences relatively early provides a longer time during which the
necessary processes which take place during the ignition delay period, e.g.
fuel evaporation and mixture preparation, may occur before high compression
temperatures are reached and ignition occurs. Both approaches have some
undesirable side-effects: specific fuel consumption tends to increase when
either advanced or retarded timings are employed; when using conventional
diesel fuel exhaust smoke is increased with retarded timings (with alcohol
fuel smoke is usually at a low level so any such effect may be minimal);
advanced timings generally incur a penalty in terms of engine noise, since
combustion tends to be very rapid under such conditions giving high rates
of rise of cylinder pressure and high levels of engine structural excitation.
The most effective injection timings for a particular engine/fuel combination
are therefore best ascertained by practical tests.
Results of engine tests during which ethanol + cetane improving
additives were used have been reported in several publications (2, 3, k, 5,
23, 2k, 25, 26). The majority of the reported work was performed on
fairly large, direct injection (DI), truck engines rather than on the
smaller indirect injection (101) units commonly used in light duty vehicles.
Figs. 2(a) and (b) (3) show results of tests made on a turbocharged Dl
engine of 11 litres during which ethanol containing various amounts of
hexyl nitrate was employed. For these tests the full load power output of
the engine was reduced from that normally obtained when operating on diesel
fuel and the injection timing was advanced by 4°. At high load conditions
at both of the operating speeds shown engine performance was very similar
when operating on either diesel fuel or ethanol fuel. At low loads perform-
ance was poor on ethanol with a low concentration of ignition improver;
examination of the curves of rate of increase of cylinder pressure and HC
emissions suggests poor combustion under these conditions.
In the case of most diesel engines operating on conventional petroleum
based fuels the majority of the NOx emissions are NO, it is apparent from
the curves of NOx-NO in Fig. 2 that this is not the case when using ethanol
with a cetane improver, presumably due to the presence of the latter
material which is a compound containing nitrogen whose combustion reactions
are not fully understood. Nevertheless overall NOx levels with the alcohol
fuels are broadly similar to those occurring with diesel fuel (in fact over
the 13 mode, heavy duty emissions test procedure NOx emissions from this
engine were lower on alcohol fuel). Fig. 2 also shows that HC and CO emis-
sions were generally lower when using alcohol with a fairly high proportion
of cetane improver. With alcohol fuels exhaust smoke and particulate emis-
sions are generally very low.
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Fuel consumption is much greater with alcohol fuels than with conven-
tional diesel fuel due to the former's much lower specific energy content.
On a basis of energy consumption more or less equal figures appear to be
returned in both heavy duty Dl (3) and light duty IDI (26) engines.
b) Blends of Alcohol & Diesel Fuel
One of the main problems involved in the use of alcohol/diesel fuel
blends is their tendency to separate particularly in the presence of water.
Fig. 3 (20) indicates the poor stability of an ethanol/diesel fuel blend
witn different percentages of water present and at varying temperature:
methanol/diesel fuel blends appear to be even less stable that this.
Various steps can be taken to minimise blend separation problems. The
most obvious approaches are to ensure that the blended fuel is maintained at
a fairly high temperature and that water is totally excluded. Both of these
approaches are difficult to maintain in normal service; complete removal of
water during alcohol production is difficult and hence costly, commercial
grade alcohol (either methanol or ethanol) generally contains at least 3%
water.
Another possible approach is to produce an emulsion of diesel fuel and
alcohol which is stabilised by the addition of a surfactant (18);
unfortunately a considerable quanity of the surfactant appears to be
necessary to ensure complete blend stability and so permit long term blend
storage.
Use of alcohol/diesel fuel emulsions formed at or close to the fuel
injection pump on an engine can produce satisfactory results since there is
then insufficient time for the emulsion to separate before injection and
combustion. This approach has been employed by various investigators (24,
27), an obvious drawback is the need for two fuel tanks and appropriate
metering systems. It is claimed that some improvement in emulsion stability,
without the use of surfactant, can be achieved by employing a mechanical
device to thoroughly mix the emulsion's constituents (17).
Due to the low cetane number of alcohols their addition to diesel fuel
produces a blend with a relatively low cetane number, Table 2 (18). Hence
the performance of any engine in which such a fuel is used tends to be
degraded, and if acceptable performance is to be achieved the proportion of
alcohol in the blend must be limited.
Fig. 4 (27) indicates how use of alcohol/diesel fuel blends results in
a reduction of engine performance relative to that achieved with neat diesel
fuel (when using equal quantities of injected fuel). This is due partly to
the lower specific energy content of the blend (which can be at least partly
offset by increasing the quantity of injected fuel) and partly due to the
lower cetane number of the blend producing poorer combustion conditions
within the engine.
Fig. 5 (20) shows comparative efficiency and HC and NOx emissions data
for three types of diesel engines operating on various blends of ethanol and
diesel fuel. Thermal efficiency at light load falls with increasing ethanol
content, HC emissions increase significantly under similar circumstances,
NOx emissions with ethanol blends are generally equal to or lower than those
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produced with straight diesel fuel, while exhaust smoke is significantly
reduced. There appears to be no published data available regarding parti-
culate emissions but it would appear likely that use of alcohol/diesel fuel
blends would be beneficial in this respect.
3.2 Alcohol Aspiration/Diesel Fuel Injection
The use of aspirated alcohol as a means of partially replacing some of
the conventional diesel fuel normally used by an engine has some advantages
over alternative methods of alcohol utilisation. The principal benefit is
the fact that a relatively simple and hence cheap 'bolt-on' conversion kit
can be used with the conventional fuel injection equipment retained to
provide reduced quantities of diesel fuel for pilot ignition of the alcohol.
The main drawback is that only limited alcohol substitution is normally
possible.
Numerous investigations have been made into the use of aspirated
alcohol in diesel engines (10, 28, 29, 30, 31, 32). Both methanol and
ethanol have been employed and addition of the alcohol to the in-going air
stream using both carburettors and low pressure injection into the intake
manifold has been evaluated; simple carburation can involve some problems
due to 'icing' caused by the high latent heat of vapourisation of alcohols.
In all reported work it has been observed that the ignition delay period
increases as the quantity of alcohol added is increased. This is attributed
to the low cetane number of alcohol and its high latent heat of vapourisa-
tion, which depresses the temperature of the in-going charge. These factors
tend to promote quenching of combustion, particularly at light loads and
high speeds, resulting in engine misfire. At high loads the maximum quantity
of alcohol which can be employed is generally limited by the onset of
'knock' - very rapid, uncontrolled, combustion - which can damage the
engine.
Several methods including advancing the injection timing, increasing
the compression ratio, heating the in-going charge and using cetane number
improvers in the diesel fuel or the alcohol have been employed in attempts
to overcome the problem of quenching while using a high proportion of
alcohol fuel. Some of the approaches have proved beneficial in this res-
pect but have had an adverse effect on knock at high loads. Fig. 6 (10)
shows some typical results of tests on a single cylinder Dl engine where
attempts were made to maximise the substitution of diesel fuel by carburet-
ted alcohol by employing inlet charge heating and an ignition improver
(amyl nitrate) added to the diesel fuel. It can be seen that the level of
substitution relative to the measures taken is very different between high
and low speed. 80 per cent is only reached at 36.7 rev/s by inlet mixture
heating to 30°C and use of 2 per cent amyl nitrate whereas, at 16.7 rev/s,
75 per cent substitution was achieved without heating whilst at 80 per cent
the engine was knock limited to a lower load. Consequently to achieve
maximum levels of substitution over the speed range, both mixture heating
and ignition promoting additives would have to be modulated. The latter is
clearly not practicable.
At part load the substitution is less if the pilot charge of diesel
fuel is held constant. The pilot charge could be modulated with the
methanol with some extra complication.
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Other investigators (28, 29, 30, 31) generally report similar results
to those observed above with substitutions of 25-60% being achieved at
different engine operating conditions. To achieve a high overall alcohol
substitution rate, e.g. greater than 50%, in an engine operating over a
wide duty cycle would require considerably complexity with respect to
modulation of alcohol flow rate, diesel fuel pilot injection quantity,
injection timing, inlet charge heating and probably the use of a cetane
number improving additive. It is also worth noting that much of the rele-
vant research work carried out to date has been conducted on single cylinder
engines; in multi-cylinder engines an additional problem would be involved
in ensuring even distribution of the aspirated alcohol fuel to each cylinder,
this could be largely overcome by using fuel injectors in each inlet port
but such a solution would incur a significant cost penalty.
Little comprehensive data have been published on the effects of
aspirated alcohol on diesel engine exhaust emissions. Some results of
tests on a single cylinder Dl engine operating at 1200 rev/min (31) are
shown in Fig. 7. Both HC and CO emissions show large increases at low
loads with aspirated alcohol. NOx emissions are reported to be decreased
(32). Exhaust smoke is generally reduced by using aspirated alcohol, this
means that, disregarding any other constraints, e.g. increased cylinder
pressures, it is usually possible to achieve a greater power output from an
engine at a given smoke limit or, conversely, to operate at the same power
output with reduced exhaust smoke. This would suggest that lower particulate
emissions would be produced by a diesel engine using aspirated alcohol.
3.3 Dual Injection Systems
The dual injection system approach to employing alcohol fuels in
diesel engines has been under investigation for several years. Two separate
fuel injection systems each with their own pump and injector in each
cylinder are required. A small quantity of diesel fuel is first injected to
establish combustion in the cylinder, this is then followed by the addition
of the main, alcohol, fuel charge which is ignited by the burning diesel
fuel. The most obvious drawback of this approach is the complexity and
hence cost involved in providing two high pressure fuel injection systems.
The main advantage of such arrangements lies in their ability to efficiently
utilise high proportions of alcohol - in excess of 90% at full load and,
probably, over 50% in average vehicle usage.
Several experimental investigations in which this approach has been
applied to Dl and IDI engines have been reported (5, 20, 2k, 37, 38, 39, ^0)
and some heavy duty vehicles employing Dl engines with dual injection systems
have undergone road trials with some success. Such systems generally employ
injection of a fixed quantity of diesel fuel (generally in the region of
5-10% of the normal full load fuelling) which is sufficient to operate the
engine under idling (no-load) conditions, the alcohol quantity is modulated
to meet variable load requirements.
Comprehensive results of tests made on prechamber and swirl chamber
IDI engines together with a Dl unit using dual diesel fuel and ethanol
injection systems have been published (20). Fig. 8 indicates the combustion
chamber configurations employed. Fig. 9(a), (b) and (c) show the perform-
ance and emission results achieved with the different engines at 1500 rev/
min. Exhaust smoke was considerably reduced on all engines when using dual
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fuelling suggesting that, other constraints permitting, a greater power out-
put could be achieved. Thermal efficiency was fairly similar when using
either diesel fuel alone or diesel fuel + ethanol. For the swirl chamber
IDI and the Dl engines NOx emissions were reduced throughout the load range,
HC and, to some extent, CO emissions were generally increased when using
diesel fuel + ethanol. Similar effects have been observed during other work
with Dl engines in which diesel fuel + methanol dual injection was used and
where other fuels, for instance ethanol plus an ignition improver or
vegetable oil, have been used for pilot injection (38).
Despite the good performance results achieved with diesel fuel + alco-
hol dual injection systems there are obvious practical difficulties involved
in accommodating two injectors per cylinder on small engines especially
where the cylinder bore is of small diameter. It appears that other
approaches could be worth investigating. These might include using twin
high pressure fuel injection pumps, one for diesel fuel, the other for
alcohol, timed so that diesel fuel is injected first followed by the main
charge of alcohol both injecting through the same nozzle assembly incorporat-
ing separate fuel circuits and separate arrangements of holes spraying the
fuel into the chamber. The practical problems involved in producing such
nozzle assemblies appear rather daunting.
A less obvious problem associated with the dual injection system
approach is the fact that fuel injector nozzles rely to a large extent on
the fuel passing through them for cooling of the nozzle tip. The pilot
(diesel fuel) injector delivers only a small quantity of fuel even at full
load and problems of carbon build-up and hole blocking due to overheating
do occur (37).
3.Alcohol Injection with Surface Ignition
It has been known for many years that methanol and ethanol have
relatively low resistance to pre-ignition (33). Recently some attempts have
been made to capitalise on this phenomenon with regard to the promotion of
alcohol combustion in diesel engines. Tests have been conducted on modified
Dl (3*». 35) and IDI engines (36) during which 100% alcohol (without the
addition of any cetane number improving additives) has been injected into
the combustion chambers of engines into which a hot surface has been incor-
porated. The hot surface ignites the alcohol after which combustion
continues in the turbulent air/fuel mixture. Fig. 10 shows versions of Dl
and IDI engines employing surface ignition, another version of a Dl engine
(35) used a conventional glow plug extending into the combustion chamber as
the hot surface.
Fig. 11 shows some performance data for the engine shown in Fig.
10(a) (36). Ignition delay periods are rather long compared with what
might be expected from a conventional diesel engine but peak cylinder
pressure and particularly the rate of pressure rise are relatively low.
Brake thermal efficiency is also low but this may be due to other factors,
e.g. the level of friction of the particular engine used; other work (35)
reports indicated thermal efficiencies of the order of 50%. Little data has
yet been published on the exhaust emission characteristics of surface
ignition alcohol engines; it is suggested that aldehyde emissions are con-
siderably lower than those produced by spark ignited, alcohol fuelled,
engines (36).
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There is obviously considerable work still needed before a full
appreciation of the potential of surface ignition engines can be obtained.
Areas which may be anticipated to present problems include durability
aspects particularly of the fuel injection equipment and the surface
heater.
3.5 Alcohol Injection + Spark Ignition
Considerable work on the application of this concept to fairly large
heavy duty Dl engines has been reported (^1 , *t2) and prototype vehicles
using such engines have been produced. Fig. 12 illustrates the combustion
chamber configuration used in MAN-FM engines; obvious practical problems
occur when attempts are made to incorporate such an arrangement in engines
of small cylinder bore size since for best performance the relative posi-
tions of the spark plug and fuel injector are critical. During normal
operation most of the injected fuel is sprayed onto the wall of the com-
bustion chamber from where it evaporates to be mixed with the rapidly swirl-
ing air in the cylinder and taken past the spark plug where ignition occurs.
The MAN-FM engines have a multi-fuel capability and successful operation on
gasoline and diesel fuel as well as alcohols has been reported. In general
when operating on alcohol fuel power output is similar to that of a con-
ventional diesel engine of equal displacement, thermal efficiency tends to
be higher at high loads but rather lower at light load than that achieved
by a diesel engine; exhaust smoke is usually negligible. HC emissions are
higher than from a diesel engine but NOx is considerably lower.
Limited work has been reported on the application of spark ignition to
an IDI diesel engine to permit operation on alcohol (^3). The engine chosen
for conversion was completely unrepresentative of modern light duty engines
but the trends displayed in the test results may provide an indication of
what could be expected following conversion of a more typical modern engine.
Fig. 13 shows that indicated thermal efficiency was broadly similar whether
the engine was operating in the spark ignited mode on methanol or ethanol or
in compression ignition mode on conventional diesel fuel. CO and, more
especially, HC (unburned fuel) emissions were considerably higher during
operation on alcohol but NOx emissions were considerably reduced. No
particulate emissions were observed when operating on alcohol.
Other work has been reported during which spark ignition has been
applied to an IDI diesel engine with a more conventional combustion chamber
layout. In this work successful operation on gasoline was achieved but
alcohol use was not attempted [kk).
3.6 Conventional Spark Ignition
Much work has been carried out on the use of alcohols and alcohol/
gasoline blends in more or less conventional spark ignited engines (16, 26,
45-53)• Generally this approach represents the easiest path to utilisation
of alcohols as engine fuels. The high octane numbers of methanol and
ethanol permit the use of quite high engine compression ratios (circa 12:1)
and so enable good thermal efficiencies to be achieved.
Problems involved in alcohol utilisation include fuels/materials
compatibility, separation tendency of gasoline/alcohol blends, the poor
cold starting characteristics of 100% alcohol (51*) and the need to recali-
brate fuel metering systems. All of these problems can be fairly readily
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Considerable test data relating to spark ignited engine operation on
alcohol fuels has been reported. Fig. I1* (53) shows results obtained from
a CFR (single cylinder) engine at 9:1 compression ratio operating at 1200
rev/min on Indolene, methanol and methanol plus 5% water (M5W), two con-
ditions of intake manifold heat addition were applied - in the first a
constant inlet mixture temperature (Tm) of 82°C was maintained while in the
second a constant quantity of heat (that necessary to maintain the air/
Indolene mixture at 82°C) was supplied, in this case the air/methanol
mixture temperature was reduced due to the high latent heat of vapourisation
of the fuel.
Methanol and M5W fuels exhibited efficiency increases of 2-3% for the
range of test conditions. At equal intake mixture temperatures, methanol
and M5W produced 5-6% less power output than Indolene. For constant mani-
fold heat conditions (substantially lower mixture temperatures), methanol
and M5W produced 5-7% more power than Indolene. Peak NOx emissions were
reduced 30-40% with methanol and 45-60% with M5W over the Indolene reference
fuel. Mass specific CO emissions were essentially unaffected by fuel type.
Mass specific emissions of unburned fuel (UBF) were comparable for Indolene
and methanol at all test conditions. Indolene, methanol and M5W exhibited
comparable UBF emissions for constant mixture temperature. For the cooler
mixture temperatures at constant manifold heat conditions, the M5W fuel
demonstrated substantially increased UBF emissions.
It is likely that a substantially higher compression ratio could have
been used when operating on methanol resulting in even better thermal
efficiency, slightly higher power output and perhaps slightly increased HC
and NOx emissions. Production engines for operation on ethanol can employ
compression ratios of 10.5:1 or greater (26).
Table 3 shows results of tests on light passenger cars powered by
diesel and optimised, ethanol burning, spark ignited engines (26). In each
case the vehicle transmission ratios were adjusted to produce approximately
equal performance. It can be seen that the ethanol fuelled spark ignited
engine returned a fuel economy superior to that of the diesel engine when
fuelled with alcohol + ignition improver additive. The first cost of the
spark ignited engine would be significantly less than that of the diesel
un i t.
4. DISCUSSION
Currently all diesel engines used in passenger cars employ IDI com-
bustion systems. Some prototype Dl engines already exist and many manu-
facturers are engaged in development work aimed at bringing such engines
to production status. At present small Dl engines are at a disadvantage
when compared to IDI units in terms of lower specific power output, higher
exhaust emissions - especially HC, NOx and particulates, and greater engine
noise; but they do offer a gain in fuel economy of around 10% (55, 56).
Most reported work in the field of alcohol utilisation by diesel engines
have been with large, heavy duty Dl engines. It is therefore difficult to
make an accurate assessment of the merits of alcohol utilisation in light
duty diesel engines. Heavy duty engines generally operate over a restricted
speed range when compared with light duty units, have larger diameter
cylinders - rendering easier the introduction of additional fuel injectors,
spark plugs, etc. and have a much higher first cost so that the incremental
costs of the additional components necessary for alcohol utilisation take on
less significance.
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From the foregoing review of published test work it is apparent that
there are several ways in which alcohol may be utilised in a diesel engine.
All the possible approaches have disadvantages compared with the operation
of an engine on conventional, good quality, diesel fuel; a benefit common
to all the evaluated systems is that they permit substitution of at least
some of the conventional fuel normally used by an engine.
With regard to the proportion of alcohol fuel which may be used in
diesel engines employing various combustion systems only two approaches -
fuel injection with either surface or spark ignition - permit the use of
100% alcohol. With compression ignition (as in a conventional diesel
engine) the low cetane numbers of alcohols require that a significant pro-
portion, at least 101, of a vigorous (and expensive) ignition promoting
additive is necessary or that a considerable proportion, at least 50%, of
good quality diesel fuel be blended with the alcohol. When using alcohol
aspiration with injection of diesel fuel an average alcohol utilisation of
around 50% may be achieved with some complexity with regard to fuel quantity
modulation, use of inlet charge heating and perhaps the use of an ignition
promoting additive. Dual injection systems offer the possibility of using
around 50-60% alcohol over typical light duty vehicle cycles but with the
disadvantages of significant complexity and hence high cost.
In general all of the alcohol utilisation systems appear capable of
producing specific power outputs equal to, or in some cases greater than,
those achieved by comparable conventional diesel engines. In those cases
where higher powers are possible this is largely due to the fact that
exhaust smoke tends to be reduced when using alcohol and hence higher fuel-
ling rates may be employed before the smoke limit is reached.
Thermal efficiency of diesel engines fuelled with alcohols is
generally similar to that achieved on conventional diesel fuels. On a
volumetric or gravimetric basis a greater quantity of alcohol is consumed
due to the disparity in the calorific values of the fuels.
Little emissions performance data regarding alcohol fuelled diesel
engines has been found in the literature. Hydrocarbon or unburnt fuel
emissions produced by all diesel engines when using alcohol appear to be
substantially higher, particularly at low loads, than when operating on
conventional diesel fuel. It should be noted that HC analysers have a
variable response depending on the type of hydrocarbon being measured, hence
direct comparison of emissions produced when operating on such radically
different fuels as alcohols and diesel fuel may be misleading. It would
appear that all the alcohol utilisation systems for which some emission
results are available produce 2-3 times greater HC emissions at part load
than comparable, conventional, diesel engines, at high loads the increase
in HC emissions is generally of the order of 1.5 times. CO emissions
levels exhibit similar trends to those observed in respect of HC with
increases of the order of 50% at low load operating conditions.
Published NOx emissions levels with alcohol utilisation are generally
similar to or lower than those occurring with diesel fuel. Dual diesel/
alcohol injection systems appear from the limited data available, Fig. 9(b),
to produce significant reductions (around 50%) of NOx emissions in swirl
chamber IDI engines, the type of combustion system most commonly used in
light duty applications. Use of cetane improvers containing nitrogen com-
pounds may increase NOx emissions; little published data are available on
this subject.
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Alcohols do not appear to form soot during combustion and they do not
contain organic materials or sulphur so that, apart from any condensed
droplets of unburnt fuel, particulate emissions arising from the combustion
of pure alcohol should be non-existent. It therefore appears likely that
in those engine combustion systems where alcohol replaces a proportion of
the diesel fuel particulate emissions in terms of total mass and quantity
of organic matter should be reduced as the diesel fuel substitution rate
increases. The reduction is unlikely to be directly proportional to the
quantity of alcohol used since the presence of the alcohol generally impairs
combustion of the diesel fuel. In systems where 100% alcohol is utilised,
i.e. with surface or spark ignition, particulate emission levels would be
expected to be very low and to be largely attributable to combustion of
small quantities of lubricating oil. Ignition promoting additives may
influence particulate emissions. No reference to measurements of particulate
emissions of alcohol fuelled diesel engines has been found in the literature.
Emissions of some materials, especially aldehydes, are likely to be
considerably greater when using alcohols as diesel engine fuels. Insuf-
ficient data are available to permit quantification of likely levels.
Some ignition promoting additives may cause the formation of hazardous
hydrogen-carbon-nitrogen compounds - HCN, again no relevant data are
available.
All the diesel engine combustion systems capable of operation with
alcohol fuel are subject to various practical problems. Alcohols have poor
lubricity and hence they may cause accelerated wear of diesel fuel systems
and engine components: this may be overcome by adding small quantities of
lubricating oil to the fuel or by changing the design of critical engine
parts. Chemical attack by alcohols of certain materials may occur; this
problem appears to be at its worst when water is also present: changes to
the materials normally used in diesel fuel systems can usually provide a
remedy. High rates of cylinder bore wear have been observed in alcohol
burning engines; again a change in material or perhaps use of a modified
lubricating oil could be of benefit. Accommodation of two fuel injection
systems or additional spark or surface ignition systems in small displace-
ment engines is difficult and such additional components impose a signifi-
cant cost penalty.
It is difficult to reach a firm conclusion with regard to which
alcohol utilisation system is most suitable for application to light duty
diesel engines. Relatively little work has been carried out in applying
any of the available systems to light duty engines. The strategy to be
employed in alcohol utilisation, e.g; whether engines are to use large or
small proportions of alcohol, is of importance as is the level of the first
cost penalty which is deemed to be acceptable.
If only a small quantity of diesel fuel, say 10%, is to be substituted
by alcohol it would appear that use of a blended alcohol/diesel fuel, per-
haps with the addition of a blend stabilising agent, is the best solution.
Engine modifications would then be confined largely to re-optimisation of
the fuelling schedule with regard to injection timing and quantity and
little or no penalty in terms of first cost should result. Some wear/
corrosion problems may occur but they should not be insurmountable. Exhaust
emission levels should be changed very little.
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Use of 1001 alcohol in diesel engines is only possible where some
supplementary means of ignition, e.g. spark plug or surface igniter, is
provided. To date most published work involving spark ignition with
alcohol fuels has been carried out on relatively large Dl engines (MAN-FM).
Good performance on a range of fuels has also been achieved in spark
ignited, IDI, swirl chamber engines and although alcohol fuels have not
been employed to date it appears likely that they could be efficiently
utilised in such engines. HC emissions would be much higher than from a
comparable diesel engine, particulates would probably be low. Specific
power output and thermal efficiency similar to a diesel engine may be
achieved after considerable development. Little work has been carried out
on combustion systems using surface ignition. Their characteristics are
therefore not fully understood.
Use of direct injection of alcohol + cetane number improver permits
total replacement of diesel fuel and involves few changes to the engine.
(Depending on the fuel supply strategy adopted some complexity may be
involved in providing a vehicle fuel system which meters and mixes
ignition improver from one tank with 'neat' alcohol drawn from another).
Unfortunately quite a high percentage of (probably) expensive fuel additive
is necessary. The impact of such an approach on some (unregulated) exhaust
pollutants,especially HCN compounds, would probably be detrimental.
Dual injection systems utilising alcohol plus a small pilot charge of
diesel fuel appear to offer some potential, at least in large, heavy duty,
engines, for use where around 50-60% alcohol substitution is desired.
Application of such an arrangement to a small engine, particularly an IDI
unit would be difficult due to the problems involved in effectively locating
two fuel injectors and a heater plug (necessary for cold starting) in a
relatively small combustion chamber. The necessity for two, independent,
fuel systems imposes a significant cost penalty. HC emissions would be
markedly higher than those from a conventional diesel engine, particulate
emissions would probably be reduced.
Basically conventional, homogeneous charge, spark ignition engines
form the easiest route for alcohol utilisation either in blends of gasoline
with 10-15% alcohol or with 100% alcohol. Apart from any fuel/materials
compatibility problems, which should be fairly readily solved, only
relatively small changes in fuel metering systems and some provision for
cold starting (when using 100% alcohol) are necessary. For optimum
efficiency higher compression ratios should be employed. HC (unburnt
fuel) emission levels generally similar to or slightly greater than those
of conventional gasoline engines may be anticipated. NOx and CO emissions
would be lower. Application of an exhaust oxidising catalyst would probably
result in HC emission levels lower than those produced by an alcohol burning
diesel engine (with untreated exhaust), while CO and NOx may also be
slightly lower, particulate emissions should be virtually non-existent.
Specific power output would be considerably higher than from a diesel
engine. Vehicle fuel economy (at equal vehicle performance) could well be
superior when using an optimised spark ignited alcohol engine than when
using alcohol in a diesel power unit.
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5. CONCLUSIONS
5.1 Various methods exist by which alcohol fuels may be utilised in diesel
engines. All of the possible systems involve additional complexity
and cost and incur additional in-service maintenance requirements.
Considerable engine development is likely to be required before satis-
factory performance is achieved with any of the available systems.
2. Most of the possible approaches have only been applied to large, heavy
duty, engines. Their application to small, light duty, engines is
likely to prove difficult.
3. Use of alcohols in diesel engines significantly increases HC emissions
but may reduce NOx and particulates compared to operation on diesel
fuel. Specific power output and thermal efficiency are likely to be
generally similar.
4. The main factors which should influence the choice of alcohol combustion
system for a light duty diesel engine appear to be a) the proportion of
alcohol to be utilised and b) the acceptable additional engine cost.
5. For the various possible alcohol utilisation strategies different com-
bustion systems appear to be most ap'pl icable:-
100% utilisation - alcohol injection + spark or surface ignition
circa 50% utilisation - dual alcohol and diesel fuel injection systems
circa 10% utilisation - single injection of alcohol/diesel fuel blend
Application of any of these approaches to light duty diesel engines
will pose problems.
6. Use of single injection of alcohol + cetane number improver is unlikely
to prove feasible until an effective, cheap fuel additive is available.
7. Optimised spark ignition engines appear to be by far the least problem-
atical and cheapest means of utilising alcohols and (at equal per-
formance levels) are likely to produce vehicle fuel economy figures at
least as good as those provided by alcohol burning diesel engines.
6. REFERENCES
1. Bolt, J.A.
A SURVEY OF ALCOHOL AS A MOTOR FUEL
(SAE SP-25^, 196^)
2. Starke, K.W.
ETHANOL AN ALTERNATIVE FUEL FOR DIESEL ENGINES
(Paper B-59, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
3. Fahlander, S. & Walde, N.
ETHANOL FUELS WITH IGNITION IMPROVER FOR TURBOCHARGED DIESEL ENGINES
(Paper B-60, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
15
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k. Bandel, W. & Ventura, L.M.
PROBLEMS IN ADAPTING ETHANOL FUELS TO THE REQUIREMENTS OF DIESEL
ENGINES
(Paper B-52, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
5. Holmer, E.
METHANOL AS A SUBSTITUTE FUEL IN THE DIESEL ENGINE
(Paper 2-^, II Intnl. Symp. on Alcohol Fuels Technology, West Germany,
1977)
6. Leng, I.J.
FUEL SYSTEMS FOR ALCOHOLS-CORROSION AND ALLIED PROBLEMS
(Paper B-13, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
7. Nierhauve, B.
METHANOL-GASOLINE BLENDED FUELS IN WEST GERMANY-SPECIFICATION £ EARLY
FIELD EXPERIENCE
(Paper B-15, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
8. Keller, J.L.
ALCOHOLS AS MOTOR FUEL?
(Hydrocarbon Processing, May 1979)
9. Crowley, A.W. et al
METHANOL-GASOLINE BLENDS PERFORMANCE IN LABORATORY TESTS AND IN
VEHICLES
(SAE 750^19)
10. Scott, W.M. £ Cummings, D.R.
DUAL FUELLING THE TRUCK DIESEL WITH METHANOL
(Paper 2-5, II Intnl. Symp. on Alcohol Fuels Technology, West Germany,
1977)
11. NicholIs, R.J.
MODIFICATION OF FORD PINTO FOR OPERATION ON METHANOL
(ill Intnl. Symp. on Alcohol Fuels Technology, USA, 1979)
12. Rentz, R.L. £ Timbario, T.J.
AN ASSESSMENT OF ALCOHOL FUELS FOR STATIONARY GAS TURBINES
(ill Intnl. Symp. on Alcohol Fuels Technology, USA, 1979)
13. Ingamells, J.C. £ Lindqvist, R.H.
METHANOL AS A MOTOR FUEL OR A GASOLINE BLENDING COMPONENT
(SAE 750123)
1^. Graham, E.E. £ Judd, B.T.
NEW ZEALAND'S METHANOL-GASOLINE TRANSPORT FUEL PROGRAMME
(III Intnl. Symp. on Alcohol Fuels Technology, USA, 1979)
15. Paul, J.K.
ETHYL ALCOHOL PRODUCTION AND USE AS A MOTOR FUEL
(Noyes Data Corp., 1979)
16. ALCOHOLS A TECHNICAL ASSESSMENT OF THEIR APPLICATION AS FUELS
(API, 1976)
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17. Deshpande, A.S. et al
OPERATION OF A HEAVY DUTY TRUCK DIESEL ENGINE ON UNSTABILISED
METHANOL/DIESEL FUEL EMULSION AND PRELIMINARY DEMONSTRATION ROAD
TEST DATA
(Paper B-37, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
18. Moses, C.A. et al
EXPERIMENTS WITH ALCOHOL/DIESEL FUEL BLENDS IN COMPRESSION IGNITION
ENGINES
(Paper B-40, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
19. Mori, M.
ETHANOL BLENDED FUELS FOR DIESEL ENGINE
(Paper B-54, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
20. Sugiyama, H.
UTILISATION OF ALCOHOL AS A FUEL IN DIESEL ENGINES
(Paper B-43, IV Intl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
21. Bin, J.V.
MISTURA DE ALCOOL E OLEO DE MAMONA COMO UM COMBUST IVEL ALTERNATIVO
PARA MOTORES DIESEL
(Paper B-53, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
22. PERFORMANCE AND STABILITY OF SOME DIESEL FUEL IGNITION QUALITY
IMPROVERS
(SAE 534, 1950)
23. Bacon, D.M. et al
THE EFFECTS OF BIOMASS FUELS ON DIESEL ENGINE COMBUSTION PERFORMANCE
(Paper B-32, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
24. Holmer, E. et al
THE UTILISATION OF ALTERNATIVE FUELS IN A DIESEL ENGINE USING
DIFFERENT METHODS
(SAE 800544)
25. Bandel, W.
PROBLEMS WITH THE USE OF ETHANOL AS FUEL FOR COMMERCIAL VEHICLES
(Paper 2-3, II Intnl. Symp. on Alcohol Fuels Technology, West Germany,
1977)
26. Pischinger, G. et al
CONSUMPTION DATA AND CONSIDERATIONS ON THREE APPROACHES TO DIESEL OIL
SUBSTITUTION
(Paper B-58, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
27. Strait, J. et al
DIESEL OIL AND ETHANOL MIXTURES FOR DIESEL-POWERED FARM TRACTORS
(SAE 790958)
28. Barnes, K.D. et al
EFFECT OF ALCOHOLS AS SUPPLEMENTAL FUEL FOR TURBOCHARGED DIESEL
ENGINES
(SAE 750469)
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29. Singh, A.K. et al
A FUEL SYSTEM FOR DUAL-FUEL OPERATION ON AN AUTOMOTIVE DIESEL
(Paper B-^2, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
30. Naeser, D. £ Bennett, K.F.
THE OPERATION OF DUAL FUEL COMPRESSION IGNITION ENGINES UTILIZING
DIESEL AND METHANOL
(Paper B-55, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
31. Cruz, J. et al
DUAL FUELLING A DIESEL ENGINE WITH CARBURETTED ALCOHOL
(III Intl. Symp. on Alcohol Fuels Technology, USA, 1979)
3.2 Panchapakesan, N.R. et al
FACTORS THAT IMPROVE THE PERFORMANCE OF AN ETHANOL-DIESEL OIL DUAL
FUEL ENGINE
(Paper 2-2, II Intnl. Symp. on Alcohol Fuels Technology, West Germany,
1977)
33. Ricardo, H.R.
THE HIGH SPEED INTERNAL COMBUSTION ENGINE
(Blackie 6 Son Ltd., 1953)
3k. Nagalingam, B. et al
SURFACE IGNITION INITIATED COMBUSTION OF ALCOHOL IN DIESEL ENGINES - A
NEW APPROACH
(SAE 800262)
35. Nanni , N. et al
USE OF GLOW PLUGS IN ORDER TO OBTAIN MULTI-FUEL CAPABILITY OF DIESEL
ENGINES
(Paper B-39, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
36. Badami, M.G. et al
PERFORMANCE AND ALDEHYDE EMISSIONS OF A SURFACE IGNITION ALCOHOL
ENGINE AND COMPARISON WITH SPARK IGNITION ENGINES
(Paper B-38, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
37. Finsterwalder, G. 6 Kuepper, H.
METHANOL-DIESEL ENGINE WITH MINIMUM PILOT INJECTION QUANTITY
(Paper B-36, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
38. Pischinger, F.F. & Havertith, C.
THE SUITABILITY OF DIFFERENT ALCOHOL FUELS FOR DIESEL ENGINES BY
USING THE DIRECT-INJECT I ON METHOD
(Paper B-57, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
39. Dietrich, W. et al
INVESTIGATIONS AND RESULTS WITH MWM PI LOT-INJECTI ON ETHANOL COMBUSTION
SYSTEM
(Paper B-35, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
*»0. Hori, M. et al
ALCOHOL AS A DIESEL FUEL - AN EXPERIMENTAL INVESTIGATION OF ETHANOL IN
AN IDI DIESEL ENGINE WITH DUAL INJECTION
(SAE Australasia, July/August 1980)
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41. Urlaub, A.G. £ Chmela, F.G.
HIGH SPEED, MULTI-FUEL ENGINE: L9204 FMV
(SAE 7^0122)
42. Neitz, A. S Chmela, F.
RESULTS OF MAN-FM DIESEL ENGINES OPERATING ON STRAIGHT ALCOHOL FUELS
(Paper B-56, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
43. Adelman, H.G. £ Pefley, R.K.
UTILIZATION OF PURE ALCOHOL FUELS IN A DIESEL ENGINE BY SPARK
IGNITION
(Paper B-34, IV Intnl. Symp. on Alcohol FUels Technology, Brazil, 1980)
44. Overington, M.T. £ Haslett, R.A.
A NEW STRATIFIED CHARGE ENGINE BASED ON THE RICARDO COMET DESIGN
(l.Mech.E. Paper C253/76, 1976)
*45. ALCOHOLS £ HYDROCARBONS AS MOTOR FUELS
(SAE SP-254, 1964)
46. Koenig, A. et al
TECHNICAL £ ECONOMIC ASPECTS OF METHANOL AS AN AUTOMOTIVE FUEL
(SAE 760545)
47. Menrad, H.
A MOTOR VEHICLE POWER PLANT FOR METHANOL AND ETHANOL OPERATION
(ill Intnl. Symp. on Alcohol Fuels Technology, USA, 1979)
48. Galvin, M. et al
THE DEVELOPMENT OF CARBURETTOR SYSTEMS FOR THE USE OF ALCOHOL IN
SPARK IGNITED ENGINES
(Paper B-2, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
49. Johnson, R.T. £ Schlueter, D.J.
COLD START DRIVEABILITY, EMISSIONS AND FUEL ECONOMY OF A STRATIFIED
CHARGE ENGINE VEHICLE USING METHANOL
(Paper B-8, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
50.
Luengo, C.A. et al
EFFICIENT BURNING OF CONCENTRATED GASOHOL OF VARIABLE COMPOSITION IN
SPARK IGNITION ENGINES
(Paper B-22, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
51. Pinto, F.B.P.
ASPECTS OF THE DESIGN, DEVELOPMENT AND PRODUCTION OF ETHANOL POWERED
PASSENGER CAR ENGINES
(Paper B-23, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
52. Schmidt, Ph. et al
DESENVOLVIMENTO DE VEICULOS E M0T0RES A ALCOOL PELA VOLKSWAGEN DO
BRAS IL SA
(Paper B-24, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
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53. Johnson, R.T.
A COMPARISON OF GASOLINE, METHANOL AND A METHANOL/WATER BLEND AS
SPARK IGNITION ENGINE FUELS
(Paper 4-3, II Intnl. Symp. on Alcohol Fuels Technology, West Germany,
1977)
54. Harrington, J.A. et al
FUEL VAPORIZATION FOR FAST COLD STARTING OF ETHANOL FUELLED VEHICLES
(Paper B-21, IV Intnl. Symp. on Alcohol Fuels Technology, Brazil, 1980)
55. French, C.C.J.
FUEL EFFICIENT ENGINES FOR LIGHT DUTY VEHICLES
(XVIII FISITA, Hamburg, VDI-Berichte Nr. 370, 1980)
56. Monaghan, M.L.
THE HIGH SPEED DIRECT INJECTION DIESEL FOR PASSENGER CARS
(SAE 810477)
CRM/BEW
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PROPERTIES OF ALCOHOLS, DIESEL FUEL & GASOLINE
Chemical Formula
Molecular Weight
Composition - weight %
Carbon
Hydrogen
Su1phur
Relative Density
Distillation Characteristics
IBP °C
10% volume °C
50% volume °C
30% volume °C
FBP °C
Lower Calorific Value MJ.kg
Latent Heat of Vaporisation MJ/kg
Stoichiometric Air/Fuel Mixture,
by we ight
Cetane No.
Research Octane No.
METHANOL
ch3oh
32
37.5
12.6
0.796
65
1S.7=^%CL5
1.10
6.
3
M 10
ETHANOL
c2h5oh
46
52.2
13.1
0.79^
78.5
DIESEL FUEL GASOLINE
Mixtures of Hydrocarbons
26.8* (I, ^2.5/^W.7
230-250
(typically)
85-88
12-15
0.2-0.5
0.81/0.85
175/185
225/235
265/275
310/330
330/350
0.8*1
9.0
8
M 10
-v.25
14.8
45-60
100-110
(typically)
85-88
12-15
<0.1
0.72/0.76
28/38
45/55
90/105
150/160
180/200
%42.5- IVTI.7
^•35
^14.6
M0
90-97
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TABLE 2
PROPERTIES OF ALCOHOL-IN-DIESEL FUEL BLENDS
Fuel & Composition
Sp.Gr. Cetane Net Heat of Combustion
15.6°V Number Mjoule/kg (BTU/lb)
Neat Fuel
Referee grade
! II
diesel
0.844
47.4
42.38
(18,222)
Micro-emulsions
10% Ethanol
4%
surfactant
0.836
4 2.4
40.62
(17,465)
20% Ethanol
8%
surfactant
0.828
37.8
38.83
(16,695)
30% Ethanol
12%
surfactant
0.820
31.8
36.99
(15,906)
10% Methanol
10%
surfactant
0.833
41.8
39.47
(16,972)
20% Methanol
20%
surfactant
0.823
35.4
36.49
(15,689)
30% Methanol
30%
surfactant
0.812
28.5
33.43
(14,373)
Solut ions
10% Ethanol
0.839
40.4
41.27
(17,714)
20% Ethanol
0.833
33.8
39.51
(16,988)
30% Ethanol
0.828
29.3
38.00
(16,335)
*•0% Ethanol
0.822
24.5
36.45
(15,672)
TABLE 3
COMPARISON OF FUEL ECONOMY OF DIESEL AND SI ENGINES OPERATING ON ALCOHOL
Engine Type Fuel
1.6 1itre CI
1.6 1i tre CI
1.5 1i tre SI
Diesel
Ethanol +
Cetane Improver
Ethanol
Accel. Time (Sees)
0-80 km/h
12.9
12.8
12.3
Urban Fuel Economy
(1/100 km)
7.0
12.A
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FIG. 1(a) - Influence of ignition improver on
cetane number. Base fuel is 95%
ethanol.
hexyl nitrate
Cetane number
60
40
2-ethylhexyl nitrate
I
20
10 20 30
% by volume of ignition improver
FIG. 1(b) - Percentage needed of Cetanox in
methanol and cetane number in order
to minimise HC-emissions to *»00 ppm.
Part load, engine speed 2200 rev/
min, ambient air temperature 25°C.
|\
"5!
Si X -,0=f
??0" \ ^
\ 5 5
i"'°[ \ i
\ p
\ ¦ 0 ijj
. . . . . V ^ !
0.5. 1.0
BMEP MPa
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FIG. 2 - Emissions, combustion pressure, rate
of pressure increase, ignition delay,
and specific fuel consumption versus
BMEP for 8, 12 and 16$ ignition
improver (hexyl nitrate) in alcohol
and for diesel fuel oil. (a) Engine
speed 1300 rev/min.
C&(pp*rt)
0OO
Too
too
loo
NO,
1800
(ppm)
Soo
5co
(bo-l
too
9o
60
76 .
60
to
4o ¦
'» •' Pnt
(bor)
RoU of pressure increase
(bar/-cj>)
ID CCA)
»e feH
"J 40
(fcer)
8%
Diesel
-------
DP.81/935
Restricted
RI0RDO
CONSULTING ENGINEERS
Report No. EPA-460/3-81-010
(b) - Engine speed 2200 rev/min
Boo
Too
3oo
too
Rote of ttcre«>e
(boc/"C a)
loo
5o
D
t2
fl
(o
9
a
7
&
5
Boo
Soo
Joo
900
7oo
too
4©o
3 oo
too
ScO-
too-
(pprrV)
SYMftCK.5 * 6 V» ——
• 12%
e lfc%
A
toe-
loo-
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DP.81/935
Restricted
RICMD
C0N8ULTIN0 ENQINECR8
Report No. EPA-^60/3-8l-010
FIG. 3 ~ Ethanol solubility in diesel fuel
ORE PHASE
1.51 trrOWTO) ETHMOL
ETHMOL
DIESEL FUEL
40 GO
DIESEL FUEL «r.I
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DP.81/935
Restricted
RKZRDD
COMSULTIHO (MOJNEEM
Report No. EPA-*f60/3-8l-010
FIG. - Full load brake mean effective pressure
for Ford and John Deere engines as influ-
enced by the ethanol content of the fuel
x
o
0
X
ID
-J
1
UJ
or
ZD
tn
V)
Hi
£
UJ
>
120
110
100
g 90
UJ
L.
li_
UJ
z
<
UJ
2
sc
<
tE
0
80
TO
1 1 I
1 1 ¦ 1
900
-
-
750
JOHN
700
DEERE
ENGINE
~—-
650
—
FORD
'
ENGINE -
600
1 1 1
. 1 . 1
0 10 20 30
ETHANOL IN FUEL- % BY VOL.
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DP.81/935
Restricted
RK2RD0
COMSULTIMO ENGINEERS
Report No. EPA-*t60/3-8l-010
FIG. 5 - Influence of the proportion of Ethanol in
diesel fuel on efficiency and exhaust emis-
sions for three different engines (speed
1500 rev/min)
SKIRL CHAMBER
PRECKAKBER
OPEN CHAflBER (OC)
i 60
£ M 50
a u
£ 5
S £3
a u_
u_
—« uj 30
! |
i ]
1 A
r ¦¦
til:
—
—rJ
/J
-
r --J*
\
/
"1
1 1
5^^
o
H 3
^
S
2 y
e
o 1/1
^Ethanol in Diesel Fuel
2000
1 /
1
)$(
2 4 6 8 10 2
INDICATED ICAK-EFFECTIVE PRESSURE KG/CH2
8 10
1600
1200 |!
u
800 =
100
0
-------
RKaRDO
COMSULTINO CMOINCERS
-------
DP.81/935
Restricted
RI0RDO
CONSULTING CNOlNSEflS
Report No. EPA-*t60/3-8l-010
FIG. 7(a) - Effects of carbureted alcohol on
unburned hydrocarbon emissions at
various torque levels
aoo
4 z soo
X o
X _>
U _j
Z 2 400
« a
2 m
go. 300
200
100
J3
o o Diesel Fuel Only
Corburetad Mftlhofiol
Corbjrftted EtHonol
» \ o—Coi buretodEfhonol
1 \ (air preheofad)
^ \ Ayproqe Air/AlcohoF Raho a| |
rm\ \
\ \*v-
rdV \ \ \
J—I—l—l I 111'
9 12 13 IS ?r 24 27 SO 3S
BROKE TORQUE , N-m
FIG. 7(b) - Effects of carbureted alcohol on
carbon monoxide emissions at various
torque levels
too
¦ > Diesel Fuel Only
¦ > Corbureled Mefhonol
0----0 Carbureted Cthanoi
a-—a Carbureted Clbanol
(or preheated)
Average Air/Alcohol RaHo*| |
60
ro
so
\
I'8
N
z z
o
c
40
b/
30
20
I
I
V
X
27 30
33
24
BRAKE TORQUE , N-m
-------
DP.81/935
Rest r i cted
RI0RDD
CONSULTING ENGINEERS
Report No. EPA-^60/3~8l-01 0
FIG. 8 - Examples of combustion systems employing
dual injection
DltSEL FiJtL
IflJ. HO^ZLE
ETHWOL 1NJ.
NOZZLE
Prechamber with Two Injection
Nozzles.
DIESEL FUEL 1NJ NOZZLE
b) Swirl Chamber with Two Injection
Nozzles.
DIESEL FUEL
INJ. NOZZLE
Open Chamber with Two Injec-
tion Nozzles.
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DP.81/935
Restricted
RI0RDO
CONSULTING ENGINEERS
Report No. EPA-^60/3-81-0,10
FIG. 9 - Performance 6 emissions of engines using
dual injection (speed 1500 rev/min)
(a) Efficiency, exhaust emissions and ethanol
replacement rate (E/F) of dual injection pre-
chamber engine and original engine
5
2 U 6 8 10
INDICATED BEAM EFFECTIVE PRESSURE
KG/CM2
A 00
I 300
5 200
= 100
0
400
a 300
t 200
= 100
0
s 1000
O DIESEL FUEL
• DUAL FUEL
4
t U 6 8 10
INDICATED MEAN EFFECTIVE PRESSURE
KG/CH2
„ 200
200
. I
T i
r
i
V
\
I
N •
•
o-
O-
"2 A 6 8 10
INDICATED KAN EFFECTIVE PRESSUR:
KG/CA2
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DP.81/935
Restricted
RKZRDO
CONBULTINQ EWQIMEEAS
Report No. EPA-^60/3-8l-010
(c) Efficiency, exhaust emissions and E/F of dual
injection open chamber engine and original
eng i ne
O liltSLL FUIl • XML Flj>L
2
0
50
40
100
80
60
0
I \
t
2 A 6 8 10
INDICATED ICAH EFFECTIVE PRESSURE
KO/CII2
s 100
'2 U 6 8 10
INDICATED HEM EFFECTIVE PSESSURE
KG/CH2
-------
DP.81/935
Restricted
RK2RDD
CONSULTING CNQtNCERS
Report No. EPA-460/3-81-010
FIG. 10 (a) - Modified Dl engine with surface
ignition
Injector
Fuel in
Electrical
connect ion
Asbestos sheet
with heater
wire.
^^Cylinder head
S«£— Cylinder
Piston
FIG. 10(b) - IDI engine with surface ignition
¦2E.
t-Pintle nozzle spraying alcohol 2 -Terminal to low voltage
electrical supply(pow«r requirement 6Vi6amps * ifiWatts)
3* Asbestos surface wound wit h healing wires 4* Spherical •
shaped twirl combustion chamber $•Cylinder head
6 "Cylinder 7 • Pi slort
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DP.81/935
Restricted
RK2RDD
CONSULTING CN01NEER3
Report No. EPA-fr60/3-8l-010
FIG. 11 - Performance of surface ignition engine
using alcohol fuels (speed 1500 rev/min)
o Methanol
a Ethanol
1.0
2.0
BHP
3.0
30
26
22
4.0
c
a>
-o
O
i_
v
Q.
18 *
u
o
70
• Methanol
A Ethanol
¦62
4.0
1
1 1
—A —
—
• Methanol —
1
a Ethanol
1 1
1.0
2.0 3.0
BHP
M
3.0
2.0
1.0
4.0
E
o
U)
0)
(/>
0)
u
3
U)
in
a>
O
c
a) to
w l.
q u
CC o
1
_
// A
//
• Methanol
~ /
1
* Ethanol —
1 1
20
16 S"
12
1.0
2 .0
BHP
3.0
4.0
-------
RK^RDO
ccusunmo emqihec»»
Report No. EPA-*>60/3-8l-010
FIG. 12 - Combustion chamber of D25&6 FMUH methanol
eng ine
-------
DP.81/935
Rest ricted
RIGRDO
CON8ULTINO ENQINEEflS
Report No. EPA-fr60/3-8l-010
FIG. 13 - Performance of a spark ignited pre-
chamber engine on alcohol fuels (19:1
compression ratio; 900 rev/min)
(a) Unburned fuel emissions versus indicated horsepower
UBF
¦ WETNiNCl
. £
• oi £ se. fj£t
/
(b) Carbon monoxide emissions versus indicated
horsepower
CO
- «e rm no1.
-(T«AI»OL
- 6IE5IC ruct
\
s'
(c) Oxides of nitrogen emissions versus indicated
horsepower
NO, '
AS
NOj
cm >
METHANOL
IT»ANOl
¦ oicsel 'ucl
>•
(d) Indicated thermal efficiency versus indicated
horsepower
—»-¦i METHANOL
- — — C ThanOL
¦ ¦— oic«cl *uil
I HP
-------
DP.81/935
Restricted
RI0RDO
CONSULTING CNQIMKKRS
Report No. EPA-460/3-81-010
FIG. 14 - Performance of a CFR engine on methanol
fuels (9:1 compression ratio, 1200 rev/min)
0.40
0 35-
0 30-
025
9 I CR
MBT SPARK
9 I CR
MBT SPARK
09 10 II 1.2 13
EQUIVALENCE RATIO, AF
- MASS SPECIFIC EMISSIONS:
6JUDES OF NITROGEN (N0X)
100
e>
o
0
1
UJ
Q
O
z
§
o
10
—1 1 1—
1 r-- ¦
9 1 CR
\ v>_
— s T j\
ntJA
MBT SPARK
u
-
\\
— _
I i i
¦---jgssw—-^
100
QL
X
10 a
X
v
CD
0.9 10 II 12 13
EQUIVALENCE RATIO, <£AF
- MASS SPECIFIC EMISSIONS:
CARBON MONOXIDE (CO)
09 1.0 II 1.2 13
EQUIVALENCE RATIO, AF
- INDICATED POWER OUTPUT
9 I CR
MBT SPARK
20
s
e>
^15
Ul
CD
I
-» 10
UJ
r>
u.
Q
UJ
£05
¦D
m
¦z.
3
I I =F
9 I CR
MBT SPARK
_L
09 10 II 12 13
EQUIVALENCE RATIO, <£AF
- MASS SPECIFIC EMISSIONS:
UNBURNED FUEL (UBF)
INDOLENE
METHANOL
M5W
A- -Tm=82°C
O—Tm=82°C
Q--V82°C
1 1
~— Qm=C0NST
H-- Qm= CONST
—i 1
q:
x
' a.
x
o
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