柴油机冷却水套的优化设计方法

Optimization Design of Cooling Water Jacket in Diesel Engines

各缸的冷却均匀性是高强化柴油机设计的基本要求之一。本文以CFD商用软件STAR-CCM+为工具,对某型六缸柴油机冷却水套进行了模拟计算和优化设计。采用进出口在同一端的方式,容易造成缸盖各缸冷却水流量分配不均匀,进而产生各缸盖冷却水速度差异很大的现象。根据流量和压差的关系,引入了流阻图的概念,进行流阻分析,通过改变上水孔尺寸,改变相应的流阻大小,灵活调整各缸盖冷却水流量分配。结果表明,基于此方法进行改进后,各缸流量分配基本均匀,冷却水流量最大不均匀度由50%降低到4.6%,冷却效果得到明显改善。最后,通过改变不同的总进口流量,进一步验证了该方法的有效性。

The cooling uniformity of each cylinder is one of the basic requirements in designing highly intensified diesel engines. In this paper, commercial CFD software STAR-CCM＋ is used as a tool to conduct simulation and optimization design of cooling water jacket for a six-cylinder diesel engine. It is found that when the inlet and outlet of cooling water are located on the same end of engine, it is likely to cause uneven water flux distribution, leading to significant difference in the flow velocity of cooling water in cylinder head. According to the relationship between flux and pressure drop, a concept of flow resistance chart is introduced with flow resistance analysis performed. By changing the size of water holes between cylinder block and cylinder head and hence the corresponding flow resistance, the distribution of water flux in each cylinder can be flexibly adjusted. The results show that after modification with the scheme proposed, the water flux distribution is basically uniform with the maximum unevenness of water flux reducing from 50% to 4. 6%. Finally by changing the overall inlet mass flow, the effectiveness of the scheme is further verified.