Mechanism of exhaust valve lead deposition at a certain aero piston engine

In view of the serious problem of cylinder compressibility decay caused by exhaust valve lead deposited of during operation in the leaded aero gasoline condition at an aero-piston engine, based on analysis of the micro-morphology and composition of the lead deposited on exhaust valve, the formation mechanism of the pollutants on exhaust valve was analyzed in combination with the structure design and actual operating environment of this engine. Research shows that the excessive low temperature of valve operating is the fundamental cause of the pollutant deposition on the exhaust valve, and the propeller windmill factor and the design characteristic of the engine fuel system are the main reasons for the low temperature of the valve when the engine is in air idle condition. Based on this, a test scheme of reducing 200 r/min of the rotation speed of propeller in windmilling and leaning the mixture to control the exhaust gas temperature above 427 ℃ at low power status was proposed to increase the exhaust valve operating temperature, and was proved to be effective by the actual test.