Emission Modelling of Spark Ignition Engine Using Two Zone Finite Heat Transfer Model

Concerns about environmental pollution and global warming are increasing the demands on modern engines, which are expected to operate at high efficiency and at the same time have minimal emissions. Emission models to predict the level of engine exhaust gas have become increasingly important in the automotive industry. In this paper, a rapid chemical equilibrium composition model is applied to calculate the main combustion products from spark ignition engine such as carbon monoxide (CO), carbon di oxide (CO2), oxygen(O-2), water vapor (H2O), nitrogen (N-2) and nitrogen oxides (NOx) emission. A two-zone thermodynamic heat transfer model has been implemented and combined with chemical kinetic models such as Zeldovich mechanism and Tan-Lu mechanism based on equilibrium concentration for calculating nitrogen oxides (NOx) and carbon monoxide (CO) emissions respectively from a gasoline spark ignition engine. Nitrogen oxides (NOx), carbon monoxide (CO) and carbon di oxide (CO2) are the three major combustion products that are harmful for the environment and human health. A number of MATLAB programs are used for emission calculations and thermodynamic simulation of SI engine. It has been found that at slightly lean fuel-air equivalence Ratio (0.95 to 0.98) and moderate combustion temperature (2200 k - 2500 k), pollutant formation is minimum. Other engine parameters such as engine speed, spark timing, compression ratio are also optimized. The model is validated by experimental data from a gasoline direct injection SI research engine.