Numerical Simulation Study On Knocking Of Kerosene Spark-ignition Engine For Unmanned Aerial Vehicle

In the field of aero engines,the ignited piston engine has the advantages of small size,high power density,simple structure and low price.It is widely favored in small and medium-sized unmanned aerial vehicles,especially the main power of medium and high speed long-endurance drones.Device.With the improvement of China's general aviation regulations and standards system,piston-type drone engines will also be vigorously developed in China's general aviation market,with great market potential.Currently,aero engines are mainly fueled by gasoline.Compared with gasoline,kerosene has the advantages of high safety and good low-temperature fluidity.The physicochemical properties of kerosene make i t more suitable for use in the aerospace sector.However,compared to gasoline,kerosene has a low octane number and is more susceptible to knocking under the same conditions.Knocking combustion is an important form of piston engine damage and needs to be avoided.In this paper,the aircraft engine ROTAX914,which is commonly used in aviation,is used as a prototype.The prototype is tested on the prototype,and the simulation model is built by AVL FIRE simulation software,and the accuracy of the simulation model is verified.In order to study the knocking combustion characteristics of the ROTAX914 engine with kerosene as fuel.Next,the detonation combustion characteristics of ROTAX914 engine with kerosene as fuel are studied.The three-dimensional CFD numerical simulation is used to study the detonation combustion process of the engine under different operating conditions,and the engine ignition timing and exhaust gas recirculation(EGR)technology are analyzed.And the effect of the mixture concentration on the engine knocking combustion intensity.The results show that the delayed ignition timing can effectively suppress the engine knocking combustion;with the increase of EGR rate,the knocking intensity is better suppressed;the richer or thinner mixture is beneficial to suppress the knocking combustion,and the former is to knock The suppression of combustion is more pronounced.Compared with previous studies,it is found that a higher EGR rate can also contribute to the knocking combustion of the engine.This paper further modified the number and position of the spark plugs,changed the dual spark plug configuration of the original machine into a single spark plug configuration,and analyzed the detonation combustion process of the engine under different working conditions in the new spark plug configuration to seek the best.The operating parameters inhibit the knocking combustion of the engine.The results show that the igniting of kerosene spark ignition engine can be better suppressed by delaying the ignition timing and using EGR technology.