发动机冷却水套设计及改进

Design and Improvement of Engine Cooling Water Jacket

针对某发动机设计了冷却水套并运用三维数值仿真技术对该水套冷却性能进行仿真分析发现,缸盖排气侧高温区的流场分布极不均匀,冷却液未能实现对缸体的完全绕流冷却,缸体水套存在局部低流速区。进一步分析发现,分水孔对流场分布具有很大的影响,并据此修改分水孔方案。仿真结果表明:改进方案缸盖高温区流场分布比较均匀,冷却液也实现了对缸体的完全绕流冷却,消除了原水套中的低流速区,高温区局部平均流速1.7 m/s,传热系数12 000 W/(m^2·K),水套平均流速大于0.5 m/s,冷却性能得到了改善。最后分析了金属纳米流体的强化换热效果,结果表明:浓度5%的铜水纳米流体局部传热系数比纯水提高了41%,效果明显的同时所需泵功也有所增加。

A cooling water jacket was designed for an engine and used to investigate its cooling performance with 3-D numerical simulation technology. It is found that flow field distribution of hightemperature region in the cylinder head exhaust side is very non-uniform and the coolant failed to circulate fully around the cylinder block water jacket, forming local low velocity zone in it. Further analysis revealed that the water jacket passage design greatly influenced on flow field distribution. So an improved water jacket scheme was proposed and analyzed. Simulated results shows that the flow field distribution in head high-temperature region became uniform and the low velocity zone disappeared. The coolant average velocity in hightemperature region reaches about 1.7 m/s and the average heat transfer coefficient about 12 000 W/（m2 ·K）, the average velocity of the whole water jacket is greater than 0.5 m/s,the cooling condition gets improved. It is demonstrated that improvement of the water jacket passage is an effective method for enhancing its cooling capacity. Finally,enhanced effect of heat transfer using Metal nanofluid was studied. Results show that the local average heat transfer coefficient of nanoftuid with 5% copper increases 41% than pure water,while the pumping power required also increases.