基于热流固直接耦合法的柴油机冷却水腔结构优化分析

Optimization of Cooling Water Jacket Structure Based on Thermal-Fluid-Solid Direct Coupling Method

针对495ZLQ柴油机原冷却水腔结构存在机体水腔周向流动不善,缸盖水腔后部及底部存在低流速区的问题,提出了三套改进优化方案。采用热流固直接耦合法分别建立机体-缸盖-缸套-缸垫-冷却水腔的整机流-固耦合传热模型,利用自适应网格划分技术进行网格划分,进行了不同柴油机工况下的数值模拟计算。研究结果表明:在不同工况下,方案3为最优方案;对于机体冷却水腔,采用双侧进水使得优化后的机体第一、第二缸排气侧冷却水流量比原机增大了约2.5倍,改善了机体水腔内冷却液的周向流动,降低了缸套内表面进排气侧的周向温差;对于缸盖,降低主喷孔高度及设计引流帽结构可以提高缸盖鼻梁区冷却液的流速,从而改善该处的热负荷状况。

To solve problems of poor circumferential flow in block water jacket and low flow velocity zones existed in rear and bottom portions of head water jacket in Model 495ZLQ Diesel Engine, three improved schemes were brought forward. The 3D fluid-solid coupled heat transfer model, including engine block, head, liner, gasket and water jacket, were developed by direct coupling method and the optimal meshes were obtained by using the adaptive meshing technology respectively. And the three schemes were simulated under different engine operating conditions. Results show that the third scheme has the best performance for various operating conditions. Cooling water entrance varied from single inlet to double inlets, the cooling water flow on exhaust sides of cylinder 1 and cylinder 2 increases by 2. 5 times than the original, improving the circumferential flow of block water jacket and reducing circumferential temperature difference between intake and exhaust sides of cylinder linear inner surface. By decrease of main jet height and adding guiding cap in the head, the flow velocity in bridge zone is increased, improving thermal load condition.