Abstract:Research of existing automobiles of energy-saving and emission reduction is very important in the interim period before popularization of new energy automobiles. Some research results showed that about 50% frictional loss of engine was generated from friction pair of piston-cylinder liner system. Based on great usage amount of engines, frictional loss of engine was reduced within a narrow range; it could exert a large influence on energy consumption and environmental enhancement. The 1.6L engine of Jetta car was used as testing subject. The pits on the Cybister bengalensis’ surface, which could reduce drag and increase wearability, were applied to the main friction pair of engine—piston skirt for the first time. Firstly, the ranges of bionic apertures and separation distances were designated according to the configuration sizes of pits of cybister surface. Then the optimal bionic apertures and separation distances were determined by relative speed drag reduction rate on the basis of relative speed of bionic piston under the three calibration conditions. The ultimate speed of bionic piston was increased as drag reduction rate increased, and the anti-drag and wear-resisting were improved with smaller friction of bionic piston. Secondly, the stress arrangement of thermalstructure coupling analysis of standard piston skirt showed that the maximum stress was at the top and the maximum deformation was at the bottom. Variable aperture and variable line spacing of bionic holes was innovatively designed. Larger aperture and greater line spacing were located near the piston top. Three levels and three factors orthogonal test was made. Level one was holes distribution, which included uniform form, stagger form, line by line to increase; level two was bionic hole, including throughhole, pit, pit and through-hole alternating; level three was bionic aperture, including three bionic aperture sizes. Under the worst conditions, standard and nine bionic pistons were done by finite element thermalstructure coupling analysis. Three typical target variables were selected as test indexes, which were maximum stress of the top of piston, maximum deformation of piston skirt and maximum stress of spill port. The test indexes of nine kinds of bionic pistons were optimized by range analysis. Primary and secondary factors were bionic hole, holes distribution and bionic aperture, and optimal combination were stagger form, pit and through-hole alternating, and bionic aperture as 2.5, 2, 1.5, 1mm. Finally, three pistons as standard piston, the best optimal performance bionic piston and optimal combination piston were selected, and the durability tests were done on test bench of engine. The temperature of the top of piston in every air cylinder, gas pressure gradient, piston wear extent and piston skirt’s surface roughness were got, which could verify the superiorities of anti-drag and wear-resisting of bionic pistons. Results of simulation and bench test indicated that the former was better in deformation and its skirt bottom had less wear and better lubrication when comparing the variable aperture, variable line spacing and uniform distribution bionic holes; through-hole unloaded concentrated stress best; the best aperture range was 1~3.5mm; stagger form could avoid blind angle in oil gathering, configuration oil and storage chip; bionic piston abrasion loss was reduced by 90%, power of work gas was increased by 50% in the air cylinder and heat dissipation efficiency was increased by 0.5% compared with standard piston.
