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

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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 NOx and PM for many years. These combustion modes have demonstrated the potential for large reductions in NOx 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 NOx 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 NOx emissions as measured over the New European Driving Cycle (NEDC).
     
  • Evaluate the tailpipe NOx emissions and fuel economy over the European transient driving cycle to access the possibility of meeting Euro V emission regulation without NOx 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 NOx 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 NOx level from the baseline, but the level fell short of the Euro V target.

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