A numerical study of a compression ignition engine operating with constant volume combustion phase: Effects of constant volume phase on combustion performance and emissions

摘要

A detailed numerical study is carried out to investigate the performance of a turbocharged compression ignition engine operating under a novel combustion strategy in which fuel injection and most of the combustion occur at a constant volume. Simulations have been performed using URANS based modelling approach along with several other sub-models. A detailed validation of the CFD model has been carried out using data from a conventional crank engine.A parametric study has been performed to investigate the effects of the duration and timing of the constant volume combustion phase (CVCP) on the engine's thermal efficiency and emissions, with comparisons against the conventional engine. Much higher in-cylinder pressures and temperatures are observed in the CVCP strategy.The results demonstrate that the CVCP strategy is capable of yielding reduced gross indicated specific fuel consumptions of up to 20% and far lower CO2 and soot emissions but incurs unacceptable increase to nitrogen oxide emissions. However, it was found that a combination of exhaust gas recirculation and improved fuel injection methods can counter the increased nitrogen oxide emissions under the CVCP strategy, while still maintaining the improved engine performance and low carbon-based emissions.