Development of heat-release rate-based emissions control models for a direct-injection diesel engine.

摘要

As emissions regulations for diesel engines are becoming more and more stringent worldwide, engine manufacturers will need to consider new engine control technologies which could reduce the exhaust emissions more efficiently. In this research, the combustion processes of a direct-injection diesel engine under various operating conditions were studied numerically. The linear control models of NOx and soot emissions were then developed by analyzing the relationships between the in-cylinder Heat-Release Rate (HRR) and the emission levels.;In the second part, HRR-based emissions control models were developed through numerical approaches. The heat release curve of each engine operating condition was generated from the calculated in-cylinder pressure trace. Linear control models for NOx and soot emissions were then constructed by analyzing the heat release and the emission be used in the high-speed engine control system which was proposed in this research.;Finally, a prototype diesel emissions control system was built. In this system, the real-time in-cylinder pressure was measured at each crank-angle as the engine was running and the real-time HRR was calculated to control an EGR valve. The NOx control model developed through the numerical simulations was implemented into the controller of the research engine. The experimental results showed that the NOx control model was effective in reducing NOx emissions under high RPM conditions. Recommendations were made on how the control models and the control system could be improved to extend their usefulness.;Keywords: diesel engine, emissions control, exhaust gas recirculation, multiple fuel injection, heat release rate, combustion, computational fluid dynamics, experiment;In the first part of this work, a three-dimensional CFD model was introduced to describe the two-phase turbulent flow and the combustion process inside the engine. The engine simulation code -- KIVA-3V was modified to solve the governing equations. The engine combustion models were calibrated using the in-cylinder pressure and emission data from the experimental research. Detailed numerical simulations were then conducted to investigate the effects of Multiple Fuel Injection (MFI) strategy and Exhaust Gas Recirculation (EGR) on NOx reductions. The simulation results showed that the use of the MFI strategy and EGR could effectively reduce the NOx emissions from a diesel engme.