The Research On Operation Characteristic Of Piston Aero-Gasoline Engine

Unmanned aerial vehicle(UAV)is not only an indispensable air weapon equipment in war,but also has a good application prospect in the civil aerospace field.Two-stroke engine is an aerodynamic power plant,which obviously has greater advantages,such as compact structure,high power,and low cost.But its structure has some defects,such as the loss of air and fuel in the scavenging process,which ensure difficultly the engine power,safety and economy.So it is related to aviation piston engine technology development is important.This research object is a two-stroke engine,which transformed it to aviation piston gasoline engine.Due to loop scavenging,variable exhaust and GDI,theoretically,the residual gas in scavenging process can be improved,more fresh air can be sealed and the short-circuit loss of gasoline mixture can be reduced.In order to ensure the accuracy of the geometric model,the three-dimensional solid model of the engine was built by three-dimensional laser scanning technology,and the simulation model of the engine was established by the AVL_Fire software.The simulation model is calibrated by the experiment to ensure the accurate of the numerical model.Combining with the structure of the scavenging system,the intake and exhaust ports is optimal to match and three schemes are put forward.The three-dimensional simulation model is used to analyze and compare the influence on scavenging process,including residual gas distribution,the turbulence kinetic energy and the average velocity of the air flow are studied.Optimization of the scavenging system is suitable for the piston engine.Based on the structure of scavenging system,the influence law of fuel injection parameters in cylinder was studied.Firstly,the influence law of fuel injection direction was studied.Based on the preferred injection direction,the influence of fuel injection time was studied.Meanwhile,studying the injection pressure,fuel injection cone angle and other different programs were carried out on the formation of mixture of air and fuel.The spark plug position,the number of spark plugs and the layout of spark plugs were optimized for the rated flight program.It is found that the double sparks were more conducive to the rapid combustion,especially the asymmetrical arrangement scheme,which is more favorable to the formation of the fire core,increasing the flame surface density and making the combustion more stable.