Research On Combustion Mechanism Of Coal To Liquid Diesel Engine Based On CONVERGE Software

Based on the energy distribution characteristics of China’s rich coal,lack of oil and gas,the demand for diesel oil in China is increasing,and the proportion of imports continues to rise.It has become an effective way to solve the energy problem in China to convert coal as industrial raw material into mixed hydrocarbon liquid fuel through different chemical processes.The F-T coal to diesel oil formed by indirect coal liquefaction has the advantages of high cetane number,short ignition delay and soft combustion.It can be blended with other fuels in any proportion to improve the combustion performance of the engine and reduce the emissions of harmful substances.In this paper,the combustion mechanism of F-T coal to liquid is simplified,and the combustion chemical kinetic model is constructed.Through the combination of bench test and numerical simulation,the differences between F-T coal to liquid and petrochemical diesel in power,atomization and emission are explored,the working process of F-T coal to liquid diesel is simulated,and the influence of F-T coal to liquid on combustion performance and emission performance under different combustion parameters is explored.Through the analysis of the composition of F-T coal to liquid,it can be seen that the physical and chemical properties of F-T coal to liquid can be accurately simulated by selecting n-octane and isooctane as the characterization fuel of F-T coal to liquid and mixing them in a certain proportion.Through the coupling simplification of two kinds of characterization fuels,the simplified mechanism of F-T coal to liquid is obtained,which contains 81 components and 361 elementary reactions.The combustion mechanism was introduced into the combustion model,and the simulation results were obtained with the help of the simulation software converse.Compared with the experimental results,it can be seen that the mechanism can better simulate the combustion process of F-T coal to liquid.Based on the engine test bench and mechanism documents,the performance differences between F-T coal to liquid and petrochemical diesel are explored.Through simulation and comparative analysis,it can be seen that:compared with petrochemical diesel,F-T coal to liquid reduces maximum effective power by 7.3%,combustion performance is optimized,NO_X emission peak value by 31%and soot emission peak value by 42%under the working conditions of 1400R/min and full throttle.By changing the combustion parameters of the engine,it can be seen that with the decrease of the diameter of the injection hole,the effective torque of the engine first increases and then decreases,the cylinder pressure and the average temperature in the cylinder increase,the fuel air mixing ratio is uniform,the NO_X emission increases and the soot emission decreases.With the increase of injection advance angle,the cylinder pressure and average temperature increase,the fuel air mixture is more uniform,and the power performance is improved.NO_X emission increased significantly and soot production decreased.With the shortening of injection duration,the cylinder explosion pressure and average temperature increase,the fuel air mixture is more uniform,the power performance increases,the soot emission decreases,but the NO_Xgeneration increases significantly.Therefore,the combustion process can be optimized and the pollutant emission can be reduced by choosing reasonable combustion parameters under the condition of ensuring the dynamic characteristics.