Exhaust Valve Heating Boundary Heat Transmission Model And Thermal Load Estimate

As the oil resources gradual scarcity, the emission regulations became more andstricter, low emission, low energy consumption, high power and high torque arebecoming the major goals of car engine development. As research continues, somemethods have been laid out to improve the engine output capability, the technologyinclude mechanical supercharging, turbocharging, inlet and exhaust VVT, directinjection. But the more work strength for engine, the more degradation environment forits components. The exhaust valve which is important part of the valve mechanismworking area with high temperature and pressure and very difficult to touch withlubricating oil. So it is very easy to lose efficacy. Exhaust valve mechanical stabilityinfluence the engine power and emission and decision the property enhancement.This paper base on the D20engine which own inlet and exhaust VVT technology.Combine with the engine four strokes (intake stroke, compression stroke, power strokeand exhaust stroke) to study on the exhaust valve thermal boundary condition.And wedivide the valve seven areas basis exhaust valve and cylinder head relatively position.About the exhaust valve stem and cone, we use the equivalent heat transfer resistance tocalculation thermal boundary conditions. For the part of exhaust valve neck, we use softFLUENT to calculation couple fields to obtain thermal boundary conditions.The material of the exhaust valve is Cr-Mn-Ni-N austenite refractory steel whichhas excellent mechanical properties in elevated temperature and corrosion resistance. Soit was used in making automobile engine. We use the software ANSYS WORKBENCH,Then we obtain the thermal load curve which is related on times. This paper makes acontrast about temperature field which are separately obtained by simulation andreference documents. We find out that the first hot spots and the second hot spots onexhaust valve is consensus, and the temperature gradient is similitude with the real one.At last, we analyzes exhaust valve thermal intensity based on temperature field.then obtain the thermal stress and equivalent stress on maximum load. And we checkthe exhaust valve one hundred million cycle fatigue strength and material resistance toplastic deformation ability at long-term high temperature load and mechanical load...