高速外啮合齿轮泵多控制体积内动态空化演变机理研究

Air released due to cavitation results in decrease of oil bulk modulus and volumetric efficiency of gear pump, and increase of pressure pulsations, which deteriorates the system stability. Due to the complexity of flow structure, the effects of dynamic air release and absorption and the interaction between pressure and flow rate, the influence of gas evolution on the flow characteristics of gear pump is very complicated. There is still a lack of deep understanding and effective theoretical approach on this problem. To address the phenomena of air release and absorption in hydraulic oil, this project intends to perform the research on oil-gas bubble dynamics and the velocities of air release and absorption by the complementary means of experimental and theoretical analysis. Furthermore, considering the gas flowing effect in open volume, the gas fraction model for open volume will be developed on the basis of gas and liquid mass conservation equations in the oil. The two-phase flow features during the flow tunnels will be investigated by this model. Finally, coupled with the fluid dynamics model of gear pump, the tooth space volume pressure, the impact mechanism of dynamic gas evolution on the volumetric efficiency and pressure pulsation will be revealed. This project will provide not only theoretical support to accurately analyze the cavitation evolution process, but also new ideas for cavitation prevention measures in the designing and modeling of high speed gear pump.

空化时气体析出，油液弹性模量减小，造成齿轮泵容积效率降低，压力脉动增大，稳定性变差。受齿轮泵流场结构、油液内气体析出消解动态效应以及压力流量耦合作用的影响，空化演变规律和对流动特性的影响机理非常复杂，对此目前还缺乏深入的认识和成熟的理论分析方法。本项目拟针对油液内空气析出消解现象，采用理论与试验相辅证的手段，开展油气两相气泡动力学和空气析出消解速率研究；进一步考虑连通容积内气体随油液的流动影响，结合控制容积内气体和液体的质量守恒方程，建立连通容积内油液含气率模型，研究流场中过流通道上油气两相流特性；在此基础上，耦合齿轮泵流体动力学模型，研究空化时齿腔压力、容积效率、压力脉动的变化规律，进而揭示其对齿轮泵流动特性的影响机理。本项目研究成果将为准确分析齿轮泵空化演变过程提供理论支撑，也将为高速齿轮泵防范空化设计提供新思路。

空化或气穴对液压系统和液压元件的流量品质、振动噪声特性有重要影响。空化时气体析出，油液弹性模量减小，造成液压泵容积效率降低，压力脉动增大，稳定性变差。外啮合齿轮泵作为常用的液压元件，高速化是其发展趋势，空化是发展高速齿轮泵的主要挑战之一。本项目围绕油液内空气析出消解效应、连通容积油液含气率模型和高速齿轮泵多控制体积内动态空化演变机理三方面开展了基础研究。首先，考虑了油液内空气析出消解效应，对经典的气泡动力学模型进行了修正，获得了稳定状态下气泡半径的解析公式，并得到了试验验证。其次，建立了油液含气率模型，研究了油液内气泡半径分布规律，拟合了气泡半径概率分布函数。并将含气率模型应用于节流口流动问题分析，实现了对节流孔质量流量的准确计算。最后，基于AMESim建立了齿轮泵耦合模型，分析了空化时齿轮泵建压过程、效率和压力流量脉动的变化规律，探明了齿轮泵空化演变对其流动特性的影响机理。该项目为液压泵空化分析提供了新的方法，为液压元件防空化设计提供了理论基础。