Turbocharging System Matching And Performance Simulation For Two-Stroke Aviation Cycle Engine

Two-stroke engine is widely applied as the small aviation power plant.Its output power declines sharply with the increase of altitude,so its usable elevation range is limited.Pressurization technology as the effective means to restore and strengthen engine power,can be used for the recovery of twostroke engine power at high altitude.On the basis of a two-stroke inlet injection aviation piston engine,the simulation model of prototype has been established in the GT-Power,and its reliability is verified using the engine dynamometer data.Through the combination of simplified matching calculation and GT-Power simulation,the most suitable turbocharger has been selected to match the prototype,and model of turbocharged two-stroke engine has been established incorporating GT2056 turbocharger and air to air intercooler.The operation of turbocharger has been controlled by wastegate,and the target flow rate of turbocharger has been set to decrease with the increase of altitude.During the whole altitude range,this control method can make the engine model run well.The compressor can operate with efficiency higher than 76%,enough surge margin and choke margin,and its maximum operating speed is under designed speed.The turbocharged engine has met the target with output power of 44 kW and BSFC of 463 g/kW·h at altitude of 7000 m.With the simulation and analysis of turbocharged two-stroke engine,laws of matching between turbocharger and engine under different altitude and engine speed are studied.The influence of varied altitude and engine speed on scavenging parameters(including exhaust back pressure,scavenging efficiency,delivery ratio and trapping efficiency)has been determined.The study results have shown that under the rated speed,the available exhaust energy of engine can maintain the high-efficiency operation of turbocharger at varied altitude.The number of high-efficiency operation points of turbocharged engine will decrease with the increase of altitude.According to the characteristics of two-stroke engine exhaust system,the geometric parameters of exhaust pipes,including divergent tube cone Angle,length and the expansion pipe length,have been optimized.The fluctuation effect of wave in exhaust pipe has been improved,which is beneficial to scavenging process of turbocharged engine.The recovery power of turbocharged engine at high altitude has been promoted further.After optimization,the output power of turbocharged engine at altitude 7000 m is 48.9kW,which is 11% higher than before.