Multi-Dimensional Simulation Of The Influence Of Injection System Parameters On Combustion Process Of Highly Intensified Diesel Engine

Because of high speed and large cycle fuel injection quantity, highly intensified diesel must burn more than 40% fuel in about half of the combustion duration compared with ordinary diesel. Therefore, a higher requirement is asked for the organization of the combustion process. Diesel engine combustion system is consisted of fuel injection system, intake system, combustion chamber. The fuel injection system affects the atomization quality directly, thereby affects the mixture formation and the combustion efficiency. Therefore, the study of the law of fuel injection system parameters of highly intensified diesel on spray, mixing and combustion process is great significance to optimize the combustion process and achieve rapid combustion.Firstly, in this thesis three-dimensional simulation software FIRE was uesed to establish a highly intensified diesel engine combustion process simulation model. Studied the influence of WAVE model parameters and EBU model parameters on the simulation results.By comparing the simulation and experimental results, the accuracy of the simulation model was verified. On this basis, analyz the velocity field, fuel-air equivalence ratio and temperature field distribution and study the combustion mechanism.Secondly, build the spray characteristics parameters from spray micro characteristics and spray space characteristics, including:the spray Sauter diameter (SMD), the number of particles in different size fractions, fuel evaporation rate and spray penetration. Through the parameters, the laws of injection pressure, injection holes (nozzle diameter), injection timing, injection rate and spray angle on the diesel spray were quantitative studied. The results show that:under the same cycle fuel injection quantity, injection system parameters impact the quality of fuel atomization by influencing the number of fuel droplets of different droplet size.Build a series of characteristics parameters to describe fuel and air mixing and combustion process, including:turbulent mixing speed, mixture concentration variance, the mass fraction of fuel-air mixture in different equivalence ratio fractions and its contribution to the combustion, the ignition delay, center of combustion gravity, combustion duration. Through the parameters, the laws of injection pressure, injection holes (nozzle diameter), injection timing, injection rate and spray angle on the fuel-air mixing and combustion process were quantitative studied. The results show that: increasing injection pressure, increasing injection timing can improve the quality of fuel-air mixture and shorten the combustion duration, improve the thermal efficiency.Finally, the influence weight of injection pressure, injection holes (nozzle diameter), injection timing and spray angle on highly intensified diesel engine performance were studied by using orthogonal experiment method and the original diesel was optimized. The results showed that:the influence weight of the fuel injection system parameters on the power of diesel changes with the chang of combustion chamber calibre-depth ratio.