Cooperative Control Of Friction And Oil Consumption By Partition Discriminating Texturing On Cylinder Liner

The friction and oil consumption of Cylinder Liner-Piston Ring(CL-PR)system is key to energy-saving and emission-reducing design of Internal Combustion Engine(ICE).On one hand,reducing friction could improve the engine mechanical efficiency;on the other hand,reducing lubricating oil consumption could reduce the particle emissions,so it is important to design the low-friction and low-oil consumption CL-PR pair.With the development of surface science and tribology of mechanical parts,the surface texturing technology has been a hot spot,and it has much potential in the application of CL-PR system in ICE.Due to the varying working condition of CL-PR,several lubrication states exists under a working cycle.According to the different lubricating requirements,it is necessary to design suitable textures on the different position on cylinder liner surface.In this thesis,based on a four-cylinder gasoline engine,the lubrication model and oil consumption model of the textured CL-PR were established for investigating the effects of micro-dimple geometrical parameters and distribution patterns on the tribological and oil consumption properties of CL-PR.The simulation results indicated that square array mode of textured micro-dimples on cylinder liner has the best lubrication performance,which was then validated by motored engine test.Based on this,the best dimple parameters(diameter 25μm,depth 8μm,area ratio 5-10%)are selected according to the demands of balancing friction and oil consumption.Secondly,the theoretical research was conducted to design the partition discriminating textured liner according to the different lubricating demands at different ring position on liner.Near the fired Top Dead Center(TDC),the main goal is to increase the film thickness and reduce the asperity contact friction;while at middle position of each stroke,the main goal is to decrease the friction power loss.It was found that texturing the micro-dimples with 10% area ratio near the fired TDC and with 5% area ratio at the middle position of the cylinder liner has the optimal lubricating and friction-reducing effects.Thirdly,the laser surface texturing technology was utilized to process the cylinderliner samples for conducting the friction tests of CL-PR pair.The testing results demonstrated that liner surface texturing could reduce the friction of CL-PR pair under different lubrication states.Compared with the honing liner,the average friction coefficient of the completely textured liner decreased by approximately 18.6-37.6%under fluid lubrication state,while the average friction coefficient decreased by approximately 1.8-6.1% under boundary and mixed lubrication state.For the partition discriminating textured liner,near the TDC area,texturing the micro-dimples with 10%area ratio is better than 5% area ratio,which validated the simulating results.In addition,compared with the honing liner,the average friction coefficient of the partition discriminating textured liner decreased by approximately 23.5-40.1% under fluid lubrication state,while the average friction coefficient decreased by approximately 1.9-5.8% under boundary and mixed lubrication state,which means the partition discriminating textured liner is feasible and applicable.Finally,the liner surface was divided into several functional regions according to the requirements of reducing friction and oil consumption.After laser processing several liner texturing schemes,a set of engine bench tests were carried on for validating.The motored engine test results validated that texturing the micro-dimples with 10% area ratio near the fired TDC and with 5% area ratio at the middle position of the liner could reduce the friction torque,which means the friction-reducing effects is in accordance with the simulation results.What is more,the partition discriminating textured liner(texturing the dimples with 10% area ratio near the fired TDC and with5% area ratio at the piston skirt contacting region of the liner)can not only reduce reduce the fuel consumption under most engine working conditions,but also reduce the lubricating oil consumption,which means the design of this textured liner can control the friction and oil consumption cooperatively.