A Numerical Simulation Of Engine-out HC Emissions For Gasoline Engine

In this paper, a model was built to predict engine-out hydrocarbon emissions for spark-ignition engines. The model was completely researched and applied to the Model NJG427A5 automobile engine. Engine-out hydrocarbon emissions were studied under normal working conditions with this model.This paper introduces the development of numerical simulation, which especially introduces theoretical researches about uHC emissions all over the world. Then the paper compares their characteristics each other. Based on the analyzing the hydrocarbon mechanisms, the paper finds out that the sources are crevices, oil layers, bulk gas quenching, deposits, liquid fuel and exhaust valve leakage.Then, based on the simplified process of uHC mechanisms into two types, one is in top-land-ring crevice volume and the other is in oil layer. The uHC in top-land-ring crevice volume is regarded as the ideal gas, and Henry Law is believed to control from oil layer absorption and desorption. The main fraction in in-cylinder oxidation is the top-land-ring crevice volume. It is controlled by threshold model. The residual hydrocarbon and exhaust hydrocarbon oxidation models use experience formula. This paper writes the model of uHC emission by FORTRAN90. The parameters of engine are included in the program. We can get the value of uHC emissions just that those parameters are input into this program.Before the calibration of this program, the experimentation of the uHC emissions was measured, and using a least squares linear regression technique performed the calibration. The measured data of uHC emission in the condition of the same speed and the changed load testified that the model has a perfect effect.At last, the paper applies the calibrated model to the NJG427A5 engine. We can predict that delaying the spark timing and increasing coolant temperature, or reducing compression ratio and crevice volume can reduce the amount of uHC emissions.