A study on the effect of ring pack structure on blowby

摘要

When internal combustion engine (IC) is operating, the gas in combustion chamber flow into crankcase through the ring pack, and other gas in crankcase will flow into combustion chamber through the same ring pack. If the latter occurs, it is considered to be reverse blowby. The oil accumulating in ring pack will be blowed into the combustion chamber by flowing gas. It not only increases the oil consumption, but also deteriorates the fuel combustion conditions with the increasing of pollutant in exhaust. As researches show, oil consumption in ring pack has three ways: oil evaporation, oil throwing and oil blowing. The third one is the major of oil consumption. Therefore, the reverse blowby through ring pack is the key point to reduce oil consumption, and needs to be strictly controlled. The gas mass flowing into combustion chamber can be represented by the reverse blowby through the top ring. Thus, a great deal of attention is focused on improving reverse blowby through top ring to reduce oil consumption and pollutant emission. Based on hydrodynamic lubrication model, asperity contact model and piston ring dynamics model, the paper regards high speed four-stroke diesel as object, to analyze dynamic characteristics of ring pack and calculate blowby. Taking the reverse blowby through top ring as optimization parameter, different structural parameters in ring grooves are used as design parameters. After the orthogonal experimental simulation and sensitivity analysis, ring pack structural parameters can be achieved, which has great effect on the optimization parameter.