Research On Combustion Characteristics And Knock Control For Piston Aviation Kerosene Engine

The spark ignited piston-type aviation kerosene engine is getting more and more attention in recent years for its advantages like small size,high power to weight ratio,reliable structure and easy maintenance.Comparing with gasoline,kerosene has the characteristics of high flash point,which means higher safety.However,the octane number and auto-ignition temperature of kerosene is small,which make it easy to knock at heavy load,and the viscosity of aviation kerosene is high and the saturated steam is low,which means that the atomization effect is poor.Hence,researching the combustion characteristics and knock combustion and the methods to control knocking of piston-type aviation kerosene engine has significant engineering application value.In this paper,a piston-type kerosene direct injection engine is studied.The influence of the end of injection,ignition advance Angle,excess air coefficient and cooling water temperature on the power performance,combustion stability and combustion process of piston-type aviation kerosene engine under partial load was studied.The results show that: the piston-type aviation kerosene direct injection engine under partial load runs more stably when the excess air coefficient is about 0.8.The choice of ignition advance angle is larger than that of gasoline,which is mainly determined by the special physical and chemical characteristics of aviation kerosene,and there is an optimal ignition advance angle.The end of injection has the optimal phase range in the intake stroke,which can reduce the combustion instability of the engine and improve the power performance appropriately.Cooling water temperature can affect the combustion characteristics of the engine to a certain extent.Reasonable control of cooling water temperature can ensure the stability of the engine and better power performance.The knock combustion analysis of piston-type aviation kerosene direct injection engine is carried out,and the knock frequency band of this engine is determined by calculating the heat release rate in the frequency domain.The heat release mechanism of knock of aviation kerosene engine is explored,which provides the research basis for the heat release control strategy of knock combustion.Analysis shows that knock was caused by the high energy value and heat release rate in 4.5~5.8kHz frequency band.The corresponding control strategy is proposed and verified by experiments.Test shows that: for the dual spark plug asynchronous ignition strategy can effectively surpress knock combustion and appropriately enhance the power performance.For the dual injection strategy,because the piston-type aviation kerosene direct injection engine works with a thicker mixture,the dual injection strategy has poor effect on knock suppression,but dual injection strategy can properly enhance power performance.For dual injection combined with dual spark plug asynchronous ignition strategy,knock can be effectively suppressed,at the same time,the power performance is further enhanced on the basis of dual injection to enhance the power performance.The knock intensity can be affected to some extent by controlling the cooling water temperature.However,too low or too high cooling water temperature will lead to power performance loss is serious,the working cycle of the engine fluctuates greatly,so reasonable control of cooling water temperature and corresponding control strategies are needed to achieve knock suppression.