Solving Inlet Valve Seat Wear Problem in High BMEP Engines

The rate of wear of valve seats on the valve and in the cylinder head is mainly a function of the seat load and the total relative displacement velocity after seating. The problem of wear becomes severer when the valve head deflects under large firing pressures observed in modern high bmep engines. A model relating the wear rate linearly with the product of load and the relative displacement at the seat is developed. After the valve closes, superficial delamination occurs when the shear strain due to friction at the surface exceeds the plasticity limit of material. The wear is minimised by reducing the co-efficient of friction at the interface or by reducing the relative displacement.

The model was validated by accelerated experiments on an actual engine running at an 18-bar bmep. Finite element analysis of the valve and the seat showed that the displacement of the valve seat could be linearly correlated with the deflection of the valve at the center. By increasing the thickness of valve head and hence the stiffness of the valve, the relative displacement at the seat after valve seating reduced and hence the wear. At the end of paper, a design norm for designing the valve head thickness for low wear rate is given.