机车柴油机喷油嘴三维流场数值模拟及其改进研究

Improved Design and Three-dimensional Numerical Simulation of Nozzle of a Locomotive Diesel Engine

通过FLUENT软件利用可压缩流体的三维湍流模型和无粘流动模型对改进前后喷油嘴内流场进行了数值模拟。对比研究发现,90°密封座面的压力损失小于60°密封座面;随着喷射压力的提高喷油嘴流量系数有减小的趋势;喷孔倒角可以增大喷油嘴流量系数,同时可以减少高压喷射带来的压力损失。在高强化中速机车柴油机上220 000 km的实际运用结果表明,该型针阀偶件大大减少了故障率,并且其工作可靠性、使用寿命有大幅度提高。

The three-dimensional numerical simulation for the compressible flow inside the nozzle tip was conducted by using FLUENT software. The study shows that there is less pressure loss in seal seat surface with 90° angle compared with 60° angle; as the injection pressure increases, the discharge coefficient of the nozzle decreases; the discharge coefficient would become larger if the fillet of nozzle hole is applied, which will help to reduce the pressure lose caused by high injection pressure. A medium speed locomotive diesel engine equipped with the improved nozzle has experienced more than 220 000 km of practical application and the result indicates that the rate of failure of needle couple significantly reduces, and reliability and durability of nozzle increase.