Development of Clean Diesel Demonstration Vehicle with Alternative Combustion and Multivariable Control System, 03-R9636

Principal Investigators
Gary D. Neely
Dr. Jayant Sarlashkar
Dr. Shizuo Sasaki

Inclusive Dates:  07/01/06 – 01/02/08

Background - SwRI has been studying the use of highly dilute combustion modes such as low temperature combustion (LTC) and premixed controlled compression ignition (PCCI) for reducing engine-out NO_x and PM for many years. These combustion modes have demonstrated the potential for large reductions in NO_x and PM, especially at low engine loads without severe fuel economy penalties. However, maintaining good combustion quality (stability and noise) during transient operation has remained a challenge. This project was concerned with exploring the collection of parameters that could be used to maintain good combustion. Also, the engine-out NO_x emissions were measured over a European driving cycle to assess the potential of meeting a moderately severe emissions standard (Euro V).

Approach - A 2.2 liter Euro IV diesel vehicle was used to perform the following project objectives:

• Determine if a collection of parameters could be used to maintain good combustion under large variations in engine conditions (exhaust gas recirculation (EGR) amount, intake manifold pressure and temperature, and coolant temperature).
   
• Review and modify the engine control logic to improve the control of engine-out NO_x emissions as measured over the New European Driving Cycle (NEDC).
   
• Evaluate the tailpipe NO_x emissions and fuel economy over the European transient driving cycle to access the possibility of meeting Euro V emission regulation without NO_x catalyst.

Accomplishments - Using injection timing as the combustion control knob, a preliminary correlation was found between injection timing and in-cylinder oxygen concentration when similar compression temperatures were obtained. This correlation is illustrated in Figures 1 and 2.

In relation to the control logic review and modifications, the following accomplishments were achieved:

• Identified and addressed problem areas of the control logic and engine maps to improve engine-out NO_x control.
   
• Demonstrated improvement of the quick warm-up operation for catalyst temperature increase following a room temperature cold-start.
   
• Assessed improvements on a test vehicle over the NEDC test cycle.
   
• Reduced engine-out NO_x level from the baseline, but the level fell short of the Euro V target.

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