A study of heavy-duty diesel engine operating parameter optimization was conducted. The goals of the study were to develop optimization algorithms applicable to engines and to demonstrate the efficiency and low emissions capabilities of a diesel engine outfitted with the latest technology and prototype equipment. A Caterpillar single-cylinder diesel engine with a prototype fuel injection system was used for the experiments.
A mathematical declaration of the optimization goal, meeting new emissions standards while retaining the lowest possible fuel consumption, was stated using an objective function and optimization was reduced to a problem of searching for a minimum or maximum on a hypersurface. The parameters to be optimized included injection pressure, boost pressure, EGR rate, and multiple injections. Previous studies have indicated that use of multiple injections, EGR, and flexible boosting can provide substantial simultaneous reductions in emissions, but careful optimization of the operating parameters is necessary in order to receive the full benefit of these combustion control techniques.
Using advanced optimization schemes, the engine was optimized for running at three important operating conditions, high engine speed (1737 rev/min) intermediate load (57%), high engine speed (1789) low load (20%), and intermediate speed (993 rev/min) high load (75%). Also, during the optimization process, interesting information about the effects of the parameters was produced. This information, together with the combustion diagnostic data gathered from the engine instrumentation, provides a more complete understanding of the combustion phenomena responsible for the emissions reductions possible with multiple injections and EGR.
The resulting optimized engine calibrations not only beat the US EPA mandated 2002/2004 emissions levels, but also provide reduced fuel consumption with respect to single injection, non-EGR baselines. Further, the present work demonstrates that response surface optimization is an effective method for optimizing engine operating engine operating parameters.