Experimental Study On Spray And Combustion Characteristics Of Direct Injection Aviation Kerosene In A Piston UVA Engine

Piston engine is widely used in the field of UAV because of its small size,light weight,high power,simple structure and operation.With high thermal efficiency and power to weight ratio,the spark ignition piston engine has become the main power device in UAV.Most of them use aviation gasoline as fuel.However,due to the transportation and storage of aviation gasoline,there are great potential safety hazards.With the increasing strategic demand for fuel simplification,aviation kerosene as the fuel of small piston engine has also become a trend.The viscosity and density of aviation kerosene are large,atomization is difficult,and the octane number of aviation kerosene is low,so it is easy to knock under the condition of large load.Therefore,it is of great significance to develop the research on direct injection aviation kerosene spray and combustion characteristics of UAV engine,and to find a way to suppress the aviation kerosene knock and improve the performance level of the engine.Firstly,based on the built-in-house high pressure common rail electronic control system,the spray characteristics of direct injection aviation kerosene were studied in the constant volume combustion chamber.The research results show that increasing the injection pressure and ambient backpressure can enhance the interaction between fuel and air,and promote the atomization of aviation kerosene.This result can be used as a guide for the injection pressure and injection timing of aviation kerosene combustion characteristic test in a single cylinder spark ignition engine.Then,based on a single cylinder spark ignition engine,this paper studies the effect of direct injection of aviation kerosene on the engine performance.As the octane of aviation kerosene is low,it is easy to knock under high compression ratio.On the basis of the original gasoline engine,reducing the compression ratio has a significant effect on broadening the load range,improving the power performance and suppressing the knock,but the engine economy will be reduced.Therefore,this paper studies the influence of different compression ratio on the engine load range,using the method of reducing compression ratio and combining different injection strategies to widen the load of range and recover engine power.Because of the large cycle variation when using aviation kerosene as fuel on the engine,this paper adopts the strategy of twin spark to reduce the cycle variation significantly.Based on this,the effect of different injection pressure and injection timing on engine performance are studied.Combined with secondary injection,the engine economy performance is improved,and the performance level of the engine burning aviation kerosene is close to that of the original engine.Finally,based on the characteristics of direct injection aviation kerosene easy to knock combustion in the single cylinder engine,this paper studies the influence of direct injection aviation kerosene mixed with ethanol fuel on engine performance with aviation kerosene as the basic fuel and ethanol as the auxiliary fuel.In this paper,different injection pressure,ethanol/aviation kerosene mixing ratio and injection timing are studied to widen the load range,recover the engine power,and achieve the engine burning aviation kerosene close to the original performance level.In this paper,different strategies are carried out to improve the performance of direct injection aviation kerosene in the cylinder of the spark ignition piston engine,which has certain guiding significance for the combustion of aviation kerosene in the spark ignition piston engine.