Study On The Multi-scale Simulation And Testing Method Of Cylinder-Piston Ring Lubrication State

The different lubrication state of friction pair will inevitably lead to different friction power consumption and wear. To ensure the reliability and power of the internal combustion engine, it is first to ensure that the friction pair in the best lubrication state. A key problem of lubrication state and transformation characteristics is to achieve real-time measurement of lubrication state. Especially, determining the transformation features from fluid lubrication state to mix lubrication state and boundary state is important.For this aim, the selection of the test method is firstly carried out, and then the characteristics of the friction state are analyzed. Finally, the friction state of cylinder liner piston ring is measured and verified in real time.The contact resistance method is an effective test method at the lubrication state analysis, the circuit is simple and it does not require expensive test equipment, but there are difficulties in reflect the film thickness quantitatively. By using self-made rotating point contact friction and wear tester, with combined experimental and theoretical analysis method, the relation between the contact point film thickness ratio and the contact resistance is established, so as to determine the lubrication state of point contact.Friction power loss caused by cylinder -piston ring is an important part of internal combustion engine friction power loss; it is a key component which effected internal combustion engine reliability, economy and power. In compression, combustion, expansion and exhaust strokes, Cylinder-piston ring friction pair will experience hydrodynamic lubrication, mixed lubrication, boundary lubrication friction and other states. In order to investigate the real-time lubricant state of Cylinder-piston ring, experimental study was carried out based on resistance measurement test method. This part of the experiment is completed with homemade reciprocating cylinder-piston ring experimental table. The practicability and reliability of contact resistance method determined the cylinder -piston ring lubrication states are verified through the temperature, load classification experiments.According to the traditional view, the lubrication state divided into fluid dynamic pressure lubrication, elastohydro-dynamic lubrication, the mixed lubrication and boundary lubrication. In recent years, some scholars believe that there is a separate lubricate state between elastohydro-dynamic lubrication and boundary lubrication, which is thin film lubrication.EHL lubrication and thin film lubrication are two different lubrication states. Lubrication mechanism is different and the adopted theoretical basis is also quite different. To determine the thin film lubricant state characteristics, on the basis of the EHL calculation, adapted the modified formula for the overall average equivalent viscosity, a faster and more accurate computational model is established to simulate thin film lubrication state of friction pair.Considered comprehensive lubricating surface roughness, the deformation in the circumferential direction of the liner, the viscosity of lubricating oil and other factors, a three-dimensional transient lubrication mathematical model for the cylinder-piston ring is established. The performance of cylinder-piston ring lubrication system is comprehensive studied, the minimum film thickness, the distribution of pressure, friction, etc., are calculated, which provides a basis for engineering design of cylinder liner and piston ring friction state.