Simulation Study On The Influence Of Water Injection On Gasoline Compression Ignition Combustion

Increasingly severe energy issues and strict emission regulations have put forward higher requirements for the thermal efficiency and emissions of internal combustion engines.Partial premixed compression ignition of gasoline,as a new type of high-efficiency and lowpolluting combustion method,has become a research hotspot in recent years.However,it is prone to knocking under high load,which greatly limits the practical application of gasoline compression ignition.Studies at home and abroad have shown that water spray,as an effective auxiliary measure,can improve the knocking phenomenon under high load.Therefore,this paper uses numerical simulation method to study the application of water injection in gasoline compression ignition combustion.In this paper,a water spray atomization experiment was carried out in a constant volume bomb,and the effects of spray pressure,ambient temperature and fluid temperature on the spray penetration distance and spray cone angle were studied.The result was to calibrate the water spray model in the combustion simulation;The spray pattern of the model is in good agreement with the spray image taken in the experiment.Then,the Converge software was used to establish a CFD calculation model for gasoline compression ignition with water injection.Based on the bench experiment,the detonation boundary conditions are determined,and the KI index is used to characterize the detonation intensity.Under this condition,the influence factors such as the position of different sprinklers,the time of spraying and the amount of sprayed water are changed to study The impact of water injection strategy on whether knocking occurs during compression ignition of gasoline,as well as the knock intensity and emissions.The results show that with the intake water injection method,the relative amount of water injection will increase the knocking intensity within 60%,and the water injection has the effect of supporting combustion.If more than 80%,a fire will occur.Therefore,for gasoline compression ignition combustion methods,water injection into the intake port has certain application prospects in improving the thermal efficiency of gasoline compression ignition engines and saving fuel,but it is not suitable for suppressing the knocking tendency of gasoline compression ignition under high load.When using the direct water injection method in the cylinder,the relative water injection volume is between 80% and 160%,which can reduce knocking,but its thermal efficiency and emission performance are related to the water injection volume and the water injection time.It is related to the coordination of fuel injection timing.The simulation results show that the injection time of-25°CA,the injection time of-5°CA and the relative injection volume of 100%can obtain a smaller KI value and a lower emissions value while ensuring higher thermal efficiency.