Study Of Combustion Process Simulation And Performance Optimization On Internal Combustion Engine Fueled With COG

Because of the energy crisis and environmental pollution,clean vehicle alternative fuels have stepped into people’s vision.Coke Oven Gas(COG),the main by-product of coking,is an ideal altenative fuel.Using it as an alternative fuel can not only achieve the comprehensive utilization of resources,but also can reduce the environmental pollution.The combustion of COG in internal combustion engine has the advantages of high combustion efficiency,less CO and THC emissions,but there are also some disadvantages such as decrease of power and increase of NOx emission.In order to play the advantages of COG and solve the problems in practical application,this paper uses the combination of theory and experiment to analyse the performance of COG engine.The main work and conclusions are as follows:(1)Study on the kinetic mechanism of COG.Based on the methane oxidation mechanism,the H2/CO combustion mechanism and the NOx formation mechanism,the COG mechanism was established by using sensitivity analysis and unimportant reaction elimination.The kinetic parameters of key reactions were optimized by means of sensitivity analysis,uncertainty analysis and particle swarm optimization.The basic combustion characteristics of COG mechanism were vertified by using the relevant experimental data.The results show that the optimized mechanism can predict the ignition delay time and laminar flame speed accurately,and it is suitable for the in-cylinder combustion,which can accurately simulate the process of combustion and NOx formation(2)Study on the numerical simulation models for COG engine.A 1D simulation model of COG engine was established by coupling the GT-POWER with CHEMKIN,and it can provide boundary conditions for 3D CFD simulation.The improved ignition model was established by KIVA software,and the combustion model and auto-ignition model were established by CHEMKIN.The 3D numerical simulation model of COG engine was established by combining the ignition model,combustion model and auto-ignition model with the main program of KIVA.The results show that the 1D numerical simulation model can accurately simulate the combustion process of the engine and predict the onset of knock.The 3D numerical simulation model can not only accurately simulate the combustion process in the cylinder,but also can simulate the generation process of in-cylinder emissions,and the pressure fluctuations during knocking.(3)Experimental study on COG engine.Based on the COG engine and the testing equipments,such as AVL FTIR,DEWETRON-CA and ETAS-LA4,the engine test platform was established to test the power,emissions and knock characteristics of COG engine.The results show that the power of the COG engine is 20%～30%lower than gasoline engine.The emission of NOx is 36%～45%higher than gasoline engine,while the emission of CO is 70%～76%and the emission of THC is 70%-78%lower than gasoline engine.Besides,COG engine is more prone to knock than gasoline engine.(4)Simulation study on COG engine.Based on the numerical simulation platform of COG engine,the effects of COG composition,combustion chamber structure,spark plug arrangement and compression ratio on the performance of engine were analyzed.The results show that the increase of methane content in COG can not only improve the engine power,but also can reduce the emission of NOx and the tendency of knock.Therefore,only the COG with high methane content can be used as the vehicle alternative fuel.The engine with pentroof combustion chamber has stronger power than the engines with hemispherical and bowl combustion chambers.Besides,the engines with pentroof and hemispherical combustion chamber are not easy to knock,but the NOx emission is slightly increased.In addition,increasing the bottom angle of pentroof combustion chamber can increase the engine power,but when the angle is more than 20 °,the influence on power,emssions and knock characteristics is not obvious.Therefore,considering the cost of the transformation,the pentroof combustion chamber with the angle of 20 ° can be used as the combustion chamber of COG engine.The location of spark plug can influence the in-cylinder combustion process,placing the plug in the middle of combustion chamber and increasing the plug height can increase the engine power,and reduce the tendency of knock.Therefor,the spark plug of COG engine should be placed in the top of combustion chamber.The engine compression ratio has obvious influences on the engine performance,and it should be optimized based on the characteristics of power,emssions and knock.(5)Optimization of COG Engine Performance.The optimizations of ignition advance angle and compression ratio of COG engine were carried out by using the multi-objective optimization algorithm.The results show that the ignition advance angle can be optimized with high accuracy and feasibility.Besides,based on the algorithm,the optimum compression ratio of COG engine is optimized as 10.7.