Diesel Engines

For at least the past three decades, compression-ignition direct-injection (CIDI) engines — commonly known as diesel engines — have demonstrated that they consume less fuel at part load (where automobiles normally operate) than conventional gasoline engines. If American drivers would accept CIDI engines, we could decrease our overall fuel consumption, be less dependent on foreign oil, and decrease the emissions of greenhouse gases in the United States. However, American drivers and manufacturers have not embraced CIDI-powered cars because of their reputation for hard starting in winter, noise, inadequate power, and odor. European manufacturers have solved these problems, but emissions of nitrogen oxides (NOx) and particulate matter (PM) have not been reduced to acceptable levels for the United States.

Argonne is working to make CIDI engines cleaner so that the United States can benefit from their many attributes. For example, Argonne has a low-inertia AC dynamometer cell furnished with the latest equipment for measuring gaseous and particulate emissions. The dynamometer and emissions equipment are capable of measuring transient and steady-state conditions.

Dynamometer with a 1.7L Mercedes-Benz Engine

The Mercedes-Benz test engine has a common-rail fuel-injection system, which allows complete control of such injection parameters as timing, duration, injection pressure, and number of injections per cycle. This dynamometer cell and engine are the basis of tests aimed at reducing NOx and PM emissions. Baseline tests of the system have been completed, and so Argonne researchers are using the results to map the engine's performance and emissions before researchers modify the engine for more 'real-world' evaluations.

Results

Thanks to Argonne's Rapid Prototyping Engine Control System (RPECS), researchers now have complete control of the fuel injection system, the exhaust gas recirculation system, and the turbocharger. Researchers have installed an AVL VisioScope, which allows them to take motion pictures inside a cylinder while the engine is running.

A recently completed research project used a Volkswagen 1.9-L diesel engine. This research, which was jointly sponsored by the Illinois Department of Commerce and Consumer Affairs (DCCA) and the U.S. Department of Energy's (DOE's) Office of Advanced Automotive Technology, tested the effect of blends of ethanol and diesel fuel. These results indicate that both NOx and PM emissions can be reduced significantly over some regions of the engine map. More importantly, there is an overlap in the regions of NOx and PM reduction. In most other technologies, reducing one component of emissions leads to an increase in the other component, but with ethanol-diesel blends, both components can be reduced in certain operating conditions.

Changes in NOx and PM Emissions with 15% Ethanol Blend. (Negative numbers indicate emissions reductions compared with neat diesel fuel)

Future Plans

Argonne researchers expect to continue work under way to sample exhaust PM. A follow-on proposal for the ethanol-diesel research has been submitted to DCCA to determine whether the regions of simultaneous NOx and PM reduction can be increased to cover a wider range of operating conditions.

In addition, a new proposal has been submitted to DOE to investigate and develop closed-loop control of diesel emissions. This proposal will draw on recently developed sensor technology developed at Argonne to measure NOx and PM emissions and control the engine on the basis of those measurements. Such closed-loop control has been used with gasoline engines since the 1980s, but it has not been used for diesel engines because of the lack of appropriate sensors. Testing of the closed-loop concept will make extensive use of Argonne's new dynamometer cell for engine testing and measurements. Argonne continues to look for a diesel engine manufacturer that will cosponsor the work.

September 9, 2004