Simulation Analysis On Cooperative Control Of Ignition And Knock Of Light-Weight, Spark Ignition, Heavy Oil Aeroengine

At present, the UAV(unmanned aerial vehicle) mainly uses turbojet, turboprop, turboshaft and turbofan engine in the field of light-weight aero-engine. However, the piston-engine still occupies an important place in the field of light-weight aero-angine due to small volume, light weight, high volume power, simple construction, easy operation, short production cycle and low cost.The aerial piston engine mainly uses gasoline as fuel whose vapour is readily explosive. However, the heavy oil is safer because of its higher flash point and volatility temperature. It is more suitable with special occasions which require integrated fuels. The related domestic researches mainly focus on taking advantage of lightweight of gasoline piston engine as well as safety and accessibility of heavy oil.Because of the great property difference between heavy oil and gasoline, fuel atomization of heavy oil which means a lot to ignition and combustion is difficult. The gas mixture is rather uneven at the time of ignition due to direct injection which against ignition and flame propagation. The reliable ignition and flame propagation is to be solved. The octane number of heavy oil is much lower than gasoline, so knock is easily appeared and urgent to be solved. On the basis of the above theory, the cooperative control of ignition and knock is needed to solve.This paper uses AVL Fire to simulate combustion process. Firstly, simulate and analyse ignition and knock separately of heavy oil in homogeneous mixture; Secondly, inject fuel directly into chamber to analyse atomization process of heavy oil, then simulate and analyse ignition and knock separately in heterogeneous mixture under different conditions; summary previous work, the paper controls cooperatively ignition and knock and provides the boundary of misfire and knock under multiple factors, with the help of orthogonal design, paper determines the best injection and ignition strategy; finally, using GT-POWER to establish entire set model, simulate and analyse variety methods which will suppress knock and influence engine performance.The main conclusions are as follows:early injection can benefit atomization and evaporation of heavy oil to form homogeneous mixture; improve initial temperature, select appropriate EGR rate and multi-injection rate can ensure better evaporation; richer mixture around spark plug, improve initial temperature, lower EGR rate, earlier ignition timing and higher ignition energy can guarantee formation of effective kernels and propagation of stable flame; rich or lean mixture, high EGR rate, late ignition timing and twice injection can suppress knock obviously; there is a proper domain of multiple factors within which the heavy oil could been ignited reliably and knock could been optimized to enhance engine performance.