Reducing exhaust emissions from an automotive DI diesel engine by means of air injection variable swirl inlet system

An air injection variable swirl inlet system (AIVSIS) by means of injecting air into helical intake passage for a diesel engine was developed. Steady flow rig test results showed that AIVSIS is able to increase or decrease the swirl strength in the cylinder at suitable injector position by different air injection directions. Position and air injection directions of injector, as well as nozzle hole diameter and air injection pressure were determined. Diesel engine test results showed that AIVSIS hardly affects volumetric efficiency in the cylinder. At lighter load operating conditions of 1500 rpm, the performance and the trade-off between NO_x and particulate emission (PT), brake specific fuel consumption (BSFC) are all improved using AIVSIS to reduce swirl strength without obvious increase of CO emission, but THC emission increases a little. At heavier load operating conditions, the performance and PT, THC and CO emissions are all improved using AIVSIS to increase swirl level, but at the same time, NO_x emission increases a little