Search

A newly developed " common-rail?valve?nozzle" hole type injector for a small direct injection spark ignition engine (125ml) is introduced in this paper. The injection parameters were adjusted by a high speed solenoid valve (HSV) numerically controlled. Based on testing results, the influences of air-fuel ratio and injection timing on performance of GDI engine are analyzed. Results show that the lean-burn limit can be extended and the fuel economy and emissions can be improved by using the combination of injection quantity with injection timing adjustment.

During quickly accelerating and sharply increasing load,the mass rate of air to engine doesn't consist with the variation of fuel flow,which results in air-fuel ratio decrease and makes the quality of mixture bad.As a result,the combustion of engine becomes worse and the smoke emission increases.To solve this problem,the air intake is modified by installing an electric supercharger (ES) in parallel with the original intake manifold,which makes the intake air be boosted to engine by the ES during the transient opera- tions.Test results showed that ES injecting air to engine under transient operating conditions of increasing speed or torque improves the combustion quality of engine and reduces the smoke emission,as well as boost power output.The improvement is more remarkable especially under the low speed and high torque transient conditions.