Clean Automotive Technology...
Innovation that Works
United States
Environmental Prnti
Agency
Clean Diesel Combustion -
Clean, Efficient; and Cost Effective Technology
Diesel engines are used worldwide because they achieve better fuel economy, lower carbon dioxide
(CO2) emissions and produce higher levels of power than conventional gasoline engines. However,
diesel engines tend to be more costly and emit high levels of oxides of nitrogen (NOx) and particulate
matter (PM) emissions. While several technology options exist to decrease these emissions, the U.S.
Environmental Protection Agency (EPA) and industry partners are evaluating and developing EPA's
Clean Diesel Combustion (CDC) technology , which refines several existing technologies into a unique
engine design that is simultaneously clean, efficient, and cost effective.
Low Emission Diesel Technology
Kydraulically Intensified
Fuel Injection System
What is Clean Diesel Combustion?
The method of CDC encompasses a series of design
changes to the diesel engine, which decrease NOx
emissions while maintaining or improving engine
efficiency. The key concept of CDC technology is the
development of in-cylinder NOx control, where NOx
emissions are reduced in the engine combustion
chamber without penalizing the engine's efficiency.
Preliminary EPA research has demonstrated positive
results for a design that achieves in-cylinder NOx
emissions much lower than levels reported by industry.
To Diesel
P»rticul*tfi
FllUr
A clean diesel combustion engine with its various components.
Key Features of CDC Technology
EPA Fuel System - Uses a hydraulically intensified fuel
system to lower PM and smoke emissions, and improve
engine efficiency.
Boost System - Increases the engine power and the
efficiency of the combustion process, thus reducing
emissions and increasing fuel economy.
Low Pressure Exhaust Gas Recirculation (EGR) - Lowers
the peak combustion temperature to reduce the formation
of NOx.
PM Aftertreatment - Reduces the remaining smoke,
unburned hydrocarbons (HC) and carbon monoxide in the
exhaust to levels required for future emissions standards.
NOx Emissions
[g/bhp-hr]
Engine Speed [rpm]
This real engine test map shows that NOx emissions
are low over the entire engine operating map. Brake
mean effective pressure (BMEP) is a measure for
comparing performance of one engine to another.
-------
Clean Automotive Technology...
Clean, efficient, cost-effective
Technical challenges include lowering participate emissions coming directly from the engine,
demonstrating the robustness of the technology in real world operation, and keeping cost/durability
relative to other approaches for meeting future stringent diesel emission standards. EPA continues to
improve the development of this technology by addressing these issues.
Benefits of CDC
CDC, with its unique combination of technology
advances, offers benefits such as:
Low Cost- In-cylinder NOx control (where NOx
emissions are reduced in the engine combustion
chamber) greatly simplifies the aftertreatment
system requirements (conventional
aftertreatment to reduce smoke, PM, and HC).
Low Emissions - Potential to achieve levels of
2007/2010 Heavy-Duty Engine and Tier 2
emission standards without the use of NOx
aftertreatment.
Scalable - Applicable to both light-duty and
heavy-duty diesel engines.
Brake Thermal
Efficiency [%]
CO
1000 12M
I860 1700 2000
Engine Speed [rpm]
This real engine test map shows a high level of engine
efficienty at various speeds and ooads. For this test, the
boost was externally supplied, simulating a well-matched
turbocharger (P exhaust = P input + 1.5 psi)
Technology Advances to Achieve Emission Standard Levels
EPA emission standards - both 2007 heavy-duty engine and the Tier 2 standards for passenger vehicles -
call for major reductions (ranging from 77 to 95 percent) in NOx and PM emissions. Although several
methods are being examined to meet these future standards, today's primary path option to reduce diesel
NOx emissions is through the use of aftertreatment devices. NOx aftertreatment devices control emissions
downstream from the engine's combustion chamber, in the exhaust system rather than in the engine.
2007: Highway Diesel NOx Standards
gttip-hr
10
8
4
2
1985 - uncontrolled levels
1990
1998
NOx aftertreatment-based
0.2 g/bhp-hr
-90% reduction
2004 f
/
2007
For model year 2007, NOx emission standards for heavy-
duty engines are reduced over 90% of current standards.
Research on CDC technology suggests that cost-effective
alternatives for long-term NOx compliance may not need to
rely exclusively on NOx aftertreatment methods. CDC
technology may be an attractive alternate method to achieve
future stringent diesel emissions standard levels.
Currently, EPA is actively discussing CDC technology with
potential partners to continue advancing the research and
possibly introduce the concept into production in the future.
EPA420-F-04-023
March 2004
------- |