International Journal of Advancements in Mechanical and Aeronautical Engineering
Author(s) : MANDLOI R.K. , PANDEY AJAY
Valves used in passenger car engines, running on gasoline, operate in a very hostile environment that is characterized by high temperatures and pressures, impact loading, thermal stresses, and fatigue loading. These engines, when in operation, result in generation of temperatures that are close to 600ºC inside the intake valve; the corresponding value for the exhaust valve being 700°C to 800°C, respectively. However, the exhaust valve temperatures can shoot up to 950°C for a retrofitted LPG – run gasoline engine. Engine valves, being subjected to such high temperature and pressures, are extremely vulnerable against wear and consequent failure. Wear failure of valves is a commonly encountered phenomenon and the fatigue crack growth has its own role to play in contributing to the failure. The wear mechanisms in valves of LPG – run retrofitted engines have been found to be a combination of oxidation and adhesive wear, though valves also fail due to surface erosion and corrosion. Since retrofitting is a common practice in many developing countries, it is important to understand and analyze the wear behavior and characteristics of valves originally designed for gasoline engines but subsequently used on LPG – run engines. In this work, wear analysis of a number of such worn - out engine valves was carried out for analyzing the failure patterns, failure causes and failure mechanisms after being in operation at high temperatures for a considerable period of time. A pin – on – disc wear tester was employed for carrying out exhaustive wear tests on valve specimens made from inlet and exhaust valves. The wear patterns thus obtained were analyzed for understanding the progressive growth of wear and eventual failure of engine valves.