Study On Air-assisted Fuel Injection System Of The Diesel Engine

With the increasing of the world energy crisis and environmental pollution,the necessities of design and performance optimization of fuel combustion equipment are emphasized again.Owing to its unique advantages in power range,high efficiency and low energy consumption,diesel engine is widely used in automobile,machinery and shipbuilding industry.It is very important to improve the fuel economy and reduce the emission of diesel engine.Therefore the article with a view to the injection system of diesel engine,researches the air assisted injection technology,while the injection to cylinder is a mixture of air and fuel.Promote the fuel atomization,improve the combustion effect and reduce the fuel consumption and emissions,aim to the new exploration and study of existing diesel injection system.First,this paper by using self-design off-line spray test stand,the high-speed camera and laser particle analyzer study the spray characteristics of two injection system which one has the air assisted injection and other doesn’t.Analyze the working parameters including injection pressure,injection,jet pressure and nozzle hole number,etc.Study the effects of these parameters on the spray characteristics.The results showed that in the situation of without air-assisted injection system,the spray cone angle and penetration distance increased with the increase of injection pressure,and the particle diameter decreased and the atomization effect became better;the effect of spray quantity on spray cone Angle and spray droplet size was small.In the situation of equipping air-assisted injection system,with the increase of the injection quantity,the spray cone Angle and the penetration distance increased,the percentage of droplet of the large diameter increased,and the atomization effect of spray droplets became worse.While nozzle number is increased from 3 to 4,the spray penetration distance decreases,the spray cone angle increases,and spray droplet mean diameter increases,but when the injection quantity increases,4 holes spray droplet crushing effect is better.The proportion of small diameter droplets in the air assisted injection system is much larger than that of non-air-assisted injection system.The air-assisted injection system is better than the non-air-assisted injection system.Secondly,based on the mechanism of aerodynamic force atomizing the fuel,this paper establishes the mathematical model of two injection system which are air-assisted and non-air-assisted.Using CFD software to set up numerical simulation models for the two kinds of injection system,complete the calculation of two injection system simulation model.The results show that the analysis results of the two kinds of injection systems consistent with the experimental results and the model result is reasonable and reliable.Finally,this article uses two injection system models to calculate and analyze the spray field.The results show that the particle size distribution of spray droplets under 30MPa injection pressure in air-assisted injection is basically the same as that of the spray droplets with non-air-assisted injection under the pressure of 80MPa.The particle size distribution of spray droplets under 60MPa injection pressure in air-assisted injection is basically the same as that of spray droplets under 100MPa spray pressure in non-air-assisted injection.The effect of air-assisted injection system on spray droplets is obvious.However the spray penetration distance differences of the two injection systems are relatively large,the low-pressure air-assisted injection system can make the fuel droplets as full as possible by extending the injection time,ignoring the effect on the combustion.This article in view of the air-assisted and non-air-assisted two injection systems has carried on the experiment and simulation researches and analyze their spray characteristics.The calculated data and the simulation results show that air-assisted injection system can reduce the injection pressure at the same time achieving the same effect of particle atomization with the non-air-assisted injection system under high pressure.Provide important theoretical and numerical basis for the application of air-assisted injection system in diesel engine,improving the fuel consumption and emission of diesel engines.