液压阀口空化流的空气型空化模型及气相可压缩性的研究

Hydraulic valve is the key of fluid power transmission and control in hydraulic system. However, the gaseous cavitating flow, which occours in valve port under large pressure gradient, high speed transient flow condition, still have no accurate mathematical description. It is a difficult problem, but it is also the basis for high performance control valve design and accurate dynamic performance prediction of the system. Gaseous cavitation in oil medium hydraulic valve differs significantly from vaporous cavitation in water medium fluid machinery in nature. This project proposing an idea of Bunsen solubility transport equation which describes the physical process of gaseous cavitation, establishing a gaseous cavitation model, considering the influence of compressibility of gas phase. Based on the theoretical model, numerical investigation is carried out to predict the hydraulic valve cavitating flow. The project also carries out hydraulic valve transient pressure distribution measurement and the valve port flow visualization experiments. Experimental and numerical results confirm each other, provide the basis for the calibration of the theoretical model parameters, verify the correctness of the model. Research results of this project can provide theoretical basis for high performance hydraulic valve design, also have general reference value for cavitating flow and gas-liquid two-phase flow problem in other fields.

液压阀是液压系统的流体控制中枢，然而阀口在大压差、高速瞬变流中出现的空气型空化流动现象至今仍未有准确的数学描述，这已成为高性能控制阀设计、系统动态性能准确预测中的基础性难题。 基于对水介质流体机械的蒸汽型空化和油介质液压阀口的空气型空化本质机理的比较分析，本项目提出了用本生溶解度输运方程描述空气型空化物理过程的思路，建立空气型空化模型，并研究空化流中气相的可压缩性；基于所提出的理论模型，对液压阀口空化流动进行数值模拟；同时开展液压阀内瞬态压力分布测量及阀口流动可视化观测实验研究，实验与数值的结果相互印证，为理论模型的参数标定提供依据，验证模型的正确性。项目的研究成果可为高性能液压阀的设计提供理论依据，对其他领域的空化流及气液两相流问题也有普遍的参考价值。

油介质空化与水介质空化在产生机理与流动特征上存在一定的差异。研究油介质的空化机理，对完善油空化模型和改善液压系统的稳定性有着至关重要意义。实验研究发现：油介质空化机理与本生溶解度和饱和蒸汽压密切相关；油液流经阀口的空化流动的周期性与水空化流动的周期性存在差异，气体膨胀机制起到重要作用。数值模拟方面，本项目完成了基于油介质空化模型和本生溶解度输运方程的，基于压力的空化流动大涡模拟求解器；提出了非结构网格下新的TVD格式；提出了考虑气相可压缩性时稳健的新压力方程构造方法。