Numerical investigation of twin swirl application in diesel engine combustion

Abstract

Unlike conventional Diesel engine Combustion Chambers (CC) which have single swirl, MR-Process CC has twin swirl that promotes fuel air mixture formation by enabling ideal vaporization of fuel spray directed towards tangentially to piston walls. For the initial studies 2-valve (one intake manifold) engine CC geometry was modified aiming to create twin swirls from the initial single swirl and this limited version of MR-Process named as Quasi MR-Process. It is concluded in these studies that a 4-valve engine is needed for an ideal twin swirl formation. However, design and application of 4-valve engine head with two intake manifolds that satisfies ideal twin swirl conditions inside the CC is a challenging task. In addition, proposed unique MR-Process CC is not known before and there is no available experimental data for the optimum values of injection characteristics, air flow field and swirl conditions. Optimum intake manifold and MR-Process CC shape design and optimum spray injection angle determination will be an expensive and time-consuming task if only utilized from experimental studies. In this study numerical analysis of MR-Process CC were performed to investigate the feasibility of twin swirl initiation and the results are presented. This study aims to reveal effectiveness/potential of twin swirl application on Diesel engines utilizing closed cycle simulations. For this purpose, the existing swirl model in open source KIVA3V-R2 code was modified to create perfect initial twin swirls at the start of the compression stroke. Then different angular velocities of the initial swirls and injection directions of fuel sprays were applied to obtain optimum fuel air mixture that ensues to increase efficiency and decrease harmful exhaust emissions. The analyzed results showed that MR-Process has potential to obtain better fuel air mixture, hence reduce emission levels while increasing efficiency of Diesel engines. This study also presents a basis for further full-cycle investigations of MR-Process CC.