The Study And Analysis On Elasto-hydrodynamic Lubrication Performance Of Piston Ring By Surface Micro-texturing

Piston ring–cylinder line is one of most important friction pairs in the internal engines. A bad working environment which connected its lubricating property, directly affects power, economy, emission property and service life of engine. With the development of science and technology in recent years and the need of energy and environment, the engine is developing towards the direction of advanced, high strength which led to serious frication and wearing of cylinder liner-piston ring. Therefore, it becomes very important to research the lubrication and friction performance of cylinder liner-piston ring to improve the lubrication condition and reduce the friction loss. Based on the elasto-hydrodynamic pressure lubrication theory, the paper created elasto-hydrodynamic fluid lubrication analysis model of cylinder liner-piston ring, which combined with the Reynolds equation, elastic deformation equation and Reynolds boundary conditions. The paper studied importance of elasto-hydrodynamic fluid lubrication when the piston moved to top dead center at compression stroke, friction lubrication performance were also studied considering various of micro-texture surfaces. Research shows that the average oil film pressure is at about 12 MPa at 4°~12° BTDC in compression stroke, surface elastic deformation starts to be notable at 10° BTDC in compression stroke. For surface texturing model, the micro-texture modeling at middle of surface goes against with the oil film formation, and it is helpful when micro-texture modeling at the side of surface.On this basis, the paper improved friction testing machine to be variable pressure to simulate cylinder pressure. The friction force is obtained between piston ring and cylinder line under different pressure load, engine speed and temperature field. It is verified the importance of elastohydrodynamic lubrication near the TDC on the compression.The paper also did some test of micro-texture surface with a to-and-fro friction test apparatus. Friction and lubrication performance were studied on different micro-texture surface modeling considering r different pressure load, engine speed and temperature field. Five different piston ring specimens were compared and the results showed the micro-dimples textured at the crowning position are not applicable for the piston ring, which has a higher coefficient of friction than the non-textured piston ring. However, the micro-dimples textured at both sides of the contact face can reduce the coefficient of friction in the test, especially for highly turbocharged vehicle engines that have a high cylinder pressure. Additionally, the results of the durability test imply better stability for practical use.