Air/Fuel Distribution Simulation in a Port Injected Gasoline Lean-burn Engine

In this paper, both numerical and experimental results of in-cylinder mixture distribution are presented, and predictions agree with measured data very well. With the simulation technique described herein, mixture ignitability in a port injection gasoline lean-burn engine can be satisfactorily evaluated based on predicted in-cylinder mixture stratification. The validation of the simulation technique can be divided into three stages. First, calculation results of in-cylinder flows are compared with measured data from Particle Image Velocimetry (PIV) measurements. Second, the accuracy of spray calculations is verified by comparing with spray measurements inside an atmospheric pressure bomb. Finally, the validated simulation technique is used to model engine intake and compression strokes with fuel injection. As a result, predicted results of mixture distribution immediately prior to ignition show a good tendency to match fuel vapor concentration distribution measured by Laser Induced Fluorescence (LIF) in an optically-accessed engine. Then, the validated simulation technique is further utilized to analyze mixture stratification mechanisms due to injection timing variations and intake port shapes. A good correlation is found between the predicted in-cylinder mixture distribution and the variation coefficient (co-variance) of indicated mean effective pressure (IMEP) obtained from engine test.