Control of Ignition Timing and Combustion Phase by means of Injection Strategy for Jet-Controlled Compression Ignition Mode in a Light Duty Diesel Engine 2020-01-0555
Premixed charge low temperature combustion such as PCCI (Premixed charge compression ignition) and HCCI (Homogeneous charge compression ignition) has been considered as a promising way to simultaneously improve the fuel economy and reduce the NOx/soot emissions compared to the traditional combustion mode. However, how to realize the stable combustion phasing is still one of the main challenges since reaction of the premixed charge is sensitive to the intake air properties (temperature, oxygen concentration) and chemical kinetics.
In this work, effects of multi-injection strategy on the controllability of premixed charge compression ignition were investigated in a light duty prototype diesel engine. Cylinder head was modified to ensure the configuration of two common rail direct injectors. One is for delivering the blended fuel of diesel and ethanol-gasoline to form the premixed charge, another is for injecting the jet-injection diesel fuel in order to trigger the ignition. Piston cavity shape was also optimized to reduce the THC and CO emission resulted from wall-wetting and incomplete combustion in the crevice. Several important factors including pre-injection timing, jet-injection timing, stratified charge prepared by double-pre injection, mass ratio of pre-injection to jet injection were investigated at four typical engine loads. Besides, a three-dimensional simulation conducted by CONVERGE was also carried out to analyze the in-cylinder working process of the JCCI mode.
Jingyu Zhu, Li Bo, Wuqiang Long
Dalian University of Technology, CATARC