气液联合式碎石器气穴控制分析

Analysis on Cavitation Control of Gas-liquid Combined Lithotripter

针对气液联合式碎石器内部出现的气蚀问题,在建立基本控制方程及质量输运方程的基础上,根据碎石器结构原理同时参考主机液压系统管路布置,搭建了包含动力系统及控制系统的整机AMESim仿真模型。之后,基于影响气穴的参数类型及对应取值范围设计了正交试验方案,并进行了仿真分析,获得了提高活塞后腔最低压力的最优水平组合。最后,对于集中参数模型无法反映流体质点运动空间的不足,进行了CFD模型与AMESim输出最优参数组合的联合仿真,并和AMESim模拟结果进行了对比。结果表明:活塞后腔出现最低压力的时刻与活塞运动至下死点的位置完全对应,这也与实际工程中出现气蚀真相的位置十分吻合;活塞前腔杆径是影响最低压力的主要因子,同时最低压力与杆径及蓄能器初始容积都呈负相关、与蓄能器压力正相关,与工作压力没有表现出明显的相关性;采用最优水平组合时,AMESim计算得到的最低压力为2.29 MPa,而CFD仿真获得的最低压力为1.016 MPa,其远高于工况条件对应的空气分离压。

Aiming at the cavitation erosion problem in the gas-liquid combined lithotripter, on the basis of establishing the basic control equation and mass transport equation, the AMESim simulation model of the whole machine including the power system and the control system is established according to the structure principle of the lithotripter and the pipeline layout of the hydraulic system of the main engine. Then, an orthogonal test scheme was designed based on the types of parameters affecting cavitation and the corresponding value ranges. On this basis, the simulation analysis was carried out and the optimal level combination for increasing the minimum pressure in the rear cavity of the piston was procured. Finally, for the deficiency that the lumped parameter model cannot reflect the motion space of fluid particles, the co-simulation of CFD model and AMESim output optimal parameter combination is carried out, and the simulation results are compared with those of AMESim. The results show that the moment when the lowest pressure occurs in the rear cavity of the piston corresponds exactly to the position where the piston moves to the bottom dead center, which is also very consistent with the location of cavitation truth in practical engineering. The rod diameter of the piston front cavity is the main factor affecting the minimum pressure, and the minimum pressure is both negatively correlated with the rod diameter and the initial volume of the accumulator, and positively correlated with the accumulator pressure. There is no obvious correlation between the minimum pressure and the working pressure. When the optimal horizontal combination is adopted, the minimum pressure calculated by AMESim is 2.29 MPa, while that obtained by CFD simulation is 1.016 MPa, which is much higher than the air separation pressure corresponding to the working conditions.