A Study of Wear in Engine Exhaust Valve Depending on Valve Materials Using a Laboratory Simulator 2007-01-0944
Engine valve and seat insert wear is one of the most important factors affecting engine performance. The engine valve and seat insert must be able to withstand the severe environment that is created by: high temperature exhaust gases generated while the engine is running, rapid movement of the valve spring, high pressure generated in the explosive process. In order to study such problems, a simulator has been developed to generate and control high temperatures and various speeds during motion. The wear simulator is considered to be a valid simulation of the engine valve and seat insert wear process with various speeds during engine activity.
This work focuses on the various degrees of wear of five different test exhaust valve materials such as HRV40, STL #6, STL #32, HRV40-FNV (face nitrided valve), NBW-FNV (face nitrided valve). Throughout all tests performed in this study, the outer surface temperature of the seat insert was controlled at 350°C, the cycle number was 4.0×106, the test load was 6860N, the fuel was LPG, the test speed was 20Hz (2400RPM) and the seat insert material was HVS1-2.
The mean (standard deviation) maximum roughness of the exhaust valve and seat insert was 25.44 (3.16) μm and 27.53 (3.60) μm at the HRV40, 36.73 (8.98) μm and 61.38 (7.84) μm at the STL #32, 73.64 (23.80) μm and 60.80 (13.49) μm at the STL #6, respectively. The mean (standard deviation) maximum roughness of the face nitrided exhaust valve and seat insert was 21.88 (2.38) μm and 25.94 (3.07) μm at the HRV40-FNV, 24.52 (2.77) μm and 40.38 (11.33) μm at the NBW-FNV, respectively.
It was discovered that the maximum roughness of exhaust valve was lower as the high temperature hardness of the valve material was higher under the same test conditions such as temperature, test speed, cycle number, test load and seat insert material. The set of the HRV40-FNV exhaust valve and the HVS1-2 seat insert group showed the best wear resistance.