A study on wear and wear mechanism of exhaust valve and seat insert depending on different speeds using a simulator

Abstract

The wear of engine valve and seat insert is one of the most important factors which affect engine performance. Because of higher demands on performance and the increasing use of alternative fuel, engine valve and seat insert are challenged with greater wear problems than in the past. In order to solve the above problems, a simulator was developed to be able 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 different degrees of wear at three different singular test speeds (10 Hz, 25 Hz & multi-Hz). For this study, the temperature of the outer surface of the seat insert was controlled at 350°C, and the test load was 1960 N. The test cycle number was 6.0×10⁶. The mean (±standard error) wear depth of the valve at 10 Hz and 25 Hz was 45.1 (±3.7)μm and 81.7 (±2.5)μm, respectively. The mean wear depth of the seat insert at 10 Hz and 25 Hz was 52.7 (±3.9) μm and 91.2 (±2.7) μm, respectively. In the case of multi-Hz it was 70.7 (±2.4)/on and 77.4 (±3.8) μm, respectively. It was found that higher speed (25 Hz) cause a greater degree of wear than lower speed (10 Hz) under identical test condition (temperature, valve displacement, cycle number and test load). In the wear mechanisms of valves, adhesive wear, shear strain and abrasive wear could be observed. Also, in the wear mechanisms of seat inserts, adhesive wear, surface fatigue wear and abrasive wear could be observed.