壁面改性强化活塞油腔换热的模拟试验

Experimental Study on Heat Transfer Enhancement of Piston Gallery Wall with Micro-Nano Structure Modification

为满足大缸径发动机活塞的冷却需要,必须采用冷却油腔进行强制冷却;但随着发动机强度的不断提升,活塞冷却油腔的换热已无法满足低速船用柴油机高强化程度发展的需求.为提升往复运动活塞冷却油腔的换热能力,从壁面改性角度着手,在不改变任何活塞结构前提条件下,将微纳米结构用于冷却油腔表面.利用往复振荡换热模拟试验研究其强化传热的效果,结果表明:试验往复振荡冲击换热的最佳换热充液率为50%,既可保证液体对壁面的冲击速度,也可使上壁面形成有效的液膜覆盖;随着转速的增加,会增大液体与气体在腔内的混合程度,在一定范围内能强化内冷油腔的换热;采用微结构超亲表面后,强化换热效果最大.

In order to meet the cooling needs of pistons of large-bore marine diesel engines,the cooling oil cham-ber must be used for forced cooling.However,with the continuous power intensification,the heat exchange of the piston cooling oil gallery has been unable to meet the needs of the high intensifying degree of the low-speed marine diesel engine.In order to improve the heat exchange capacity of the reciprocating piston cooling oil gallery,a micro-nano structure was first used for the cooling oil gallery surface modification without changing any piston structure,and then a reciprocating oscillation heat transfer simulation experiment was used to study its heat transfer en-hancement effect.The results show that the best heat transfer filling rate of the reciprocating oscillation shock heat transfer is 50%.It can not only ensure the impact speed of the liquid on the wall surface,but also make the upper wall surface to form an effective liquid film cover.Increase of the rotating speed will increase the mixing degree of the liquid and gas in the gallery,and then strengthen the inner cooling oil gallery within a certain range.After adopting the micro-nano structure with super-hydrophilicity surface,the heat transfer effect is significantly im-proved,18%larger than the polished surface.