Visualization Test And Numerical Simulation Of Low Temperature Premixed Combustion Of Ethanol/Diesel Dual Fuel

With the frequent occurrence of the global energy crisis and the increasing environmental pollution,countries around the world have developed increasingly strict emission regulations for motor vehicles burning fossil fuels.The application of clean alternative fuels on diesel engines has received increasing attention.At present,the application of ethanol in diesel engines has become a hot spot for scholars in the field of internal combustion engines.The main purpose of this paper is to analyze how the ethanol affects the combustion process of the model in the ethanol/diesel dual-fuel premixed low-temperature combustion mode from the perspective of the flame information of the combustion process;to study the effective means of regulating the combustion mode to achieve clean and efficient combustion.Based on the optical dual fuel engine test bench(ethanol PFI+diesel DI),the ethanol/diesel premixed low temperature combustion was realized.The effects of ethanol premixing ratio,diesel injection timing and intake air temperature on the flame development and the regulation function of combustion process in-cylinder were studied;The three-dimensional simulation software CONVERGE was used to calculate the mixture distribution in-cylinder and emission characteristics.Through experiments,it is found that with the increase of ethanol premixing ratio,the ignition time is gradually delayed,the blue flame is obvious in the combustion process,the soot concentration is reduced,the ignition point appears in the central area of the cylinder,and the development of the ignition core becomes slow;In advance,the combustion process gradually moves forward,the premixing ratio increases first and then decreases slightly,the soot concentration increases first and then decreases,and the injection timing advances too much,causing the ignition point position to be transferred from the central region to the vicinity of the cylinder wall surface;The intake air temperature is increased,the combustion process is advanced,the combustion duration is shortened,the premixing ratio is first increased and then slightly decreased,the concentration of soot is first decreased and then increased,and the position of the ignition point does not change with the change of the intake air temperature.The simulation results show that the ethanol premixing ratio is increased or the diesel injection timing is advanced,and the equivalence ratio peak of the in-cylinder mixture is decreased.The area with the mixture equivalent ratio of 1.0 increases first and then decreases,and the mixing of fuel and air becomes uniform.The equivalent ratio is around1.0,and the combustion is the most intense.Therefore,the high temperature region(above1800K)of the in-cylinder combustion process first increases and then decreases,and the NO_x emission increases first and then decreases;the intake air temperature rises,resulting in in-cylinder combustion.The high temperature region of the process(above 1800K)increased,the NO_x emission increased,and the soot emission trend was consistent with the experimental results.As can be seen from the above research,the addition of ethanol will inhibit the formation and development of the fire core.The addition of proper amount of ethanol can improve the uniformity of the mixture,increase the proportion of premixed combustion,improve the combustion process,and reduce soot emissions.The diesel injection timing and the intake air temperature are double.The combustion process of fuel has a strong regulatory effect.