某发动机冷却水套散热性能分析及优化

赵真真，刘红莉，董淑锦

安徽江淮汽车集团股份有限公司，安徽 合肥  230601

摘要：为准确评估发动机水套换热性能，基于AVL_FIRE软件对某发动机缸盖、缸体水套的流速、换热系数进行计算流体动力学（computational fluid dynamics，CFD）仿真分析。仿真结果表明：第4缸排气侧流速相对其他缸偏低，部分区域换热系数较小，无法满足评价标准；缸盖集成排气歧管后端法兰处冷却液流速较低，下层水套基本没有冷却液流动，为流动死区，容易使热负荷集中；冷却液体积流量为136 L/min时，发动机水套流阻为42 kPa，相对匹配功率为450 W的电子水泵，水套流阻较大。将第4缸气缸垫的一个水孔截面积增大80%，增设1个气缸垫水孔，另外一个水孔截面积减小10%，同时将堵棒流通长度增加150%，通过碗形塞优化排气歧管后端水套上、下层的连通，对优化水套进行CFD分析及流-固耦合分析，结果表明：冷却液体积流量为136 L/min时，水套流阻为35 kPa，满足匹配的电子水泵功率要求；优化后第4缸缸体下层水套冷却液流动明显改善，第2、3缸进排气门鼻梁区后端换热系数偏低，但缸盖水套关键区域温度满足限值要求。

关键词：水套；换热系数；流阻；冷却；发动机鼻梁区

Analysis and optimization of heat dissipation performance of an engine cooling water jacket

ZHAO Zhenzhen, LIU Hongli, DONG Shujin

Anhui Jianghuai Automobile Group Co., Ltd., Hefei 230601，China

Abstract：To accurately assess the heat exchange performance of the engine water jacket, computational fluid dynamics (CFD) simulations are conducted using AVL FIRE software to analyze the flow rate and heat transfer coefficient of the water jackets in the cylinder head and engine block of an engine. The simulation results indicate that the flow rate on the exhaust side of cylinder 4 is relatively lower than that of other cylinders, and the heat transfer coefficient of some areas is insufficient to meet the evaluation standards. The coolant flow rate at the rear flange of the integrated exhaust manifold on the cylinder head is low, resulting in minimal coolant flow in the lower water jacket, creating a dead zone for flow. At a coolant flow rate of 136 L/min, the flow resistance of the engine water jacket is 42 kPa, which is relatively matched to an electronic water pump with a power of 450 W, indicating high flow resistance in the water jacket. By increasing the cross-sectional area of one water hole in the cylinder head gasket by 80% and adding another water hole, while reducing the cross-sectional area of another water hole by 10% and increasing the flow length of the blocking rod by 150%, the flow between the upper and lower layers of the water jacket at the rear end of the exhaust manifold is optimized using a cup-shaped plug. CFD analysis and fluid-structure interaction analysis of the optimized water jacket are conducted, showing that at a coolant flow rate of 136 L/min, the water jacket flow resistance is reduced to 35 kPa, meeting the power requirements of the matched electronic water pump. After optimization, the coolant flow in the lower water jacket of cylinder 4 is significantly improved. Although the heat transfer coefficients in the nose area at the rear end of the intake and exhaust valves of cylinders 2 and 3 are still low, the maximum temperatures of the cylinder head and block met the specified limits.

Keywords: water jacket; heat transfer coefficient; flow resistance; cooling; engine nose area