卧式柴油机冷却水套结构优化与流动特性分析

针对卧式柴油机结构特点,设计了强制冷却闭式循环系统水套结构,在不同工况下对水套入口流量及关键点的温度和压力进行了测试与分析.利用计算流体动力学软件对冷却水套的流场、压力场和换热系数分布进行了分析,并对原水套结构进行了优化.结果表明:原水套平均流速为1.00 m/s,平均换热系数为7 767 W/( m2· K),压力损失为0.027 MPa,基本符合工程设计要求；但各缸冷却水流速和传热系数不均匀,在公共水腔中部、二缸缸体水套上部出现大的漩涡,二缸鼻梁区、两个排气道下方局部区域存在流动死区.结构优化后,水套平均流速达到1.35 m/s,平均换热系数达到9 826 W/(m2·K),较原方案分别提高了35％和26.5％.在热负荷最大的缸盖鼻梁区,冷却水平均流速达到1.33 m/s,提高了41.5％,换热系数都在5000 W/( m2· K)以上,没有出现原方案中的局部流动死区和大的漩涡.

A Structural Optimization Cooling Water Jacket and an Analysis of Its Flow Characteristics of New-type Horizontal Diesel Engine

According to the structural characteristics of new-type horizontal diesel engine, the cooling jacket of forced cooling closed-loop system was designed, the temperature and pressure of inlet position and key points of cooling jacket were measured and analyzed under different working conditions. Computational fluid dynamics (CFD) software was utilized to study the fluid flow and the flow field, the pressure field and heat transfer coefficient distribution were analyzed and optimized. The results indicated that the mean flow velocity, average heat transfer coefficient and whole pressure loss of the original cooling jacket were 1.00m/s, 7767W/(m2·K) and 0.027MPa respectively. They met the requirements of engineering design. But the cooling water flow velocity and average heat transfer coefficient between two cylinder bore were non-uniform. There were big swirls in the central region in public cavity and the top region in the second cylinder block water jacket and dead flow region in the bridge of the nose area of the second cylinder head and the local area below two exhaust port. After optimization,the mean flow velocity and average heat transfer coefficient came up to 1.35m/s and 9826W/(m2·K), increased by 35% and 26.5% respectively than the original design. The mean flow velocity of cooling water came up to 1.33m/s,increased by 41.5% and the average heat transfer coefficient was greater than 5000W/(m2·K) in the bridge of the nose area of cylinder head. Compared to the original design, there was no dead flow region, no big swirls existed in new cooling jacket.