气缸盖冷却水腔内两相流动沸腾传热仿真研究

Simulation of Two-Phase Flow Boiling Heat Transfer in Cylinder Head Cooling Water Jacket

采用计算流体动力学软件CFX,考虑气缸盖内冷却水的热力学相变特性,应用汽液两相流过冷沸腾换热计算模型,对不同影响因素下由柴油机气缸盖与冷却水腔组成的流固耦合传热系统进行了整场离散、整场求解,得到了不同影响因素下气缸盖火力面温度场分布;通过与试验结果的对比分析,证明了仿真计算结果的有效性。研究结果表明:与单相流不考虑沸腾换热相比,考虑汽液两相流的过冷沸腾换热能够有效降低气缸盖火力面的最高温度,提高冷却水的进口速度,降低进口温度;适当减小冷却系统的压力,可以进一步有效降低气缸盖火力面温度,减小气缸盖火力面的热负荷。该结果可为进一步研究柴油机气缸盖的沸腾冷却及可控性提供参考。

The computational fluid dynamics software CFX was applied and the thermodynamic phase change characteristics of the cylinder head cooling water were considered.The calculation model of sub-cooled boiling heat transfer for gas-liquid two-phase flow was used for the fluid-solid coupling heat transfer system which is composed by the diesel engine cylinder head and the cooling water jacket with the method of discretizing and solving for the entire domain.The cylinder head temperature field distribution was obtained under the different influence factor conditions and validated by the experimental data.The results show that,compared with the single-phase flow without considering the boiling heat transfer,the sub-cooled boiling heat transfer of gas-liquid two-phase flow can effectively reduce the highest temperature of the cylinder head flame-face,and increase the inlet speed of cooling water and lower the inlet temperature.In addition,the cooling system pressure drops appropriately which further reduces the cylinder head flame-face temperature,thus lowering the heat load of the cylinder head flame-face.