Study On An Opposed Piston Two Stroke Internal Combustion Engine For Unmanned Aerial Vehicle

In the field of aircraft engine,piston engine have the advantages of small size,high power density,simple structure and low price.It has been widely favored by small-medium sized Unmanned Aerial Vehicle(UAV)and has been the main power unit for medium-high speed UAV.With the improvement of general aviation regulations and standards in China,the piston aircraft engine will be rapid development in the general aviation of our country in the future,and will show great market potential.In this paper,a four stroke engine Rotax914 was studied as a reference object,and the prototype experiment was conducted.The simulation model of the prototype was established by BOOST software,and validated by experimental data.In order to study the suitability of four-stroke engine on a UAV,a turbocharger was chosen and matched for the prototype.The performance at different altitudes was calculated,and the results show that after matching a turbocharger,the UAV can reach a height of 6000 m.In order to improve the power density and reliability of aircraft engine,a Opposed Piston Two-Stroke(OPTS)folding crank engine was studied in this paper.The design of piston motion mechanism and cylinder structure were carried out,and the prototype experiments were conducted.In addition,the BOOST software was used to establish the simulation model of OPTS prototype by "equivalent method",and verified by the experiment data.In order to improve the scavenging efficiency of OPTS engine,the simulation model was used to optimize the crank angle,intake and exhaust port height,intake and exhaust port width.The optimization results show that the prototype performance has been improved obviously at medium-high speed.So as to study the applicability of OPTS engine in UAV,the different altitude performance of OPTS engine was calculated by simulation.The results show that the maximum operating altitude of the non-charged OPTS engine is about 2800 m.In order to improve the high altitude performance of OPTS engine,a turbocharger was chosen and matched for the OPTS prototype.After the simulation calculation,the results show that the maximum working altitude of the turbocharged OPTS engine can up to 6000 m.To compare the suitability of a four-stroke engine and OPTS engine on a UAV,the engine size and weight were compared.The results show that OPTS engine has the advantages of power density.Therefore,OPTS engine is more suitable for UAV.