离心泵叶片前缘空化诱导空蚀作用机理研究

For centuries, cavitation has been an extremely constraint for the development of centrifugal pump. Its existence would even be a great threaten for pump safety. The phenomenon of cavitation erosion is complex since it involves both hydrodynamic and material properties. Hence, the physical mechanism of cavitation induced erosion is still an open debate. . In the current project, we are about to lucubrating the erosion mechanism specific in centrifugal pump by conducting experimental tests accompanied with numerical simulation and theoretical analysis. The development of the cavitating flow, impact load on blade and erosion will be tested simultaneously at the first place, based on of which the potential erosion probability of different cavitation structure would be obtained. In the meantime, the propagation pattern of the impulsive pressure wave and its energy attenuation will be analyzed. Afterwards, according to these investigations and with the supplementary of numerical simulation, the correlation between the impact load, cavitation shedding frequency and pit parameters could be found. Then we are able to reveal the mechanism of the leading edge cavitation induced erosion in centrifugal pump, and it is essential to establish cavitation model and its induced erosion model for centrifugal pump, by considering the rotating characteristics and the large curvature of the impeller. On the premise of this, we can build a coupled cavitation and erosion simulation method, which could provide a theoretical basis to enrich the cavitation erosion mechanism and improve the design method of centrifugal pump.

空化空蚀长久以来制约着离心泵的发展，甚至危害泵的安全稳定运行。鉴于空化空蚀同时涉及非定常流场特征以及材料结构特性，国内外研究尚未较好地揭示离心泵内叶片前缘空化诱导空蚀的作用机理。本项目拟以实验为主、结合理论分析与数值模拟的方法，对离心泵叶片前缘空化致空蚀机理进行深入研究。首先通过开发同步数据采集技术对空泡发展过程、叶片表面瞬态冲击载荷及空蚀过程进行同步测量，获得空泡的演变规律及其诱导腐蚀性能，研究空化流场脉动压力冲击波传播规律及其能量衰减机制；然后基于实验测量与数值模拟结果，分析建立蚀点相关参数与材料表面冲击载荷和空泡脱落频率之间的函数关系，进而揭示离心泵叶片前缘空化的诱导空蚀机理；最后考虑离心泵的旋转效应与大曲率几何结构特征，提出适用于离心泵的空化模型与空蚀模型，并据此建立离心泵内空化与空蚀的耦合仿真技术，为丰富和发展离心泵空化空蚀理论，提高我国离心泵的设计水平提供参考。

离心泵作为应用最广泛的水力机械之一，对其水力设计方法、内部流动机制的研究不但关系到国民经济的发展，还与人民群众的日常生活和生命安全密不可分，而离心泵中的空化现象却限制了离心泵向着尺寸更大、速度更快以及效率更高的方向发展。因此对空化及其诱导空蚀现象的研究有助于为离心泵水力设计、结构优化提供一定的参考，具有重要的理论和实际意义。.本研究针对水力装置中存在的空化问题，综合运用试验与数值模拟相结合的方法，首先对两种结构简单的水力装置文丘里管和孔板进行了研究，深入研究了空化诱导空蚀的机理和脉动压力冲击波的传播规律，探讨了空泡结构与空蚀的内在联系。研究表明空泡的脱落和溃灭阶段均具有破坏金属壁面的冲击波能量，其中溃灭阶段是主要原因。蚀点数量与面积的增加呈阶梯型而非线性。压力冲击波能量以水波状向外扩散辐射，其作用效果随着与固壁的距离增加而减弱。.基于文丘里管和孔板空化与空蚀的图像试验数据，建立了一种综合的空化与空蚀图像后处理研究方法，包括蚀点计算法、空蚀图像预测法和空化周期分析法。通过以上方法可利用试验和数值模拟的空化空蚀图像分析蚀点的数量和腐蚀面积、预测空蚀的区域和分布情况、提取空化演变的周期频率。.根据以上研究结论，并考虑离心泵的旋转效应与流场湍动能对空泡的影响，提出了一种适用于离心泵空化数值计算的RZGB空化模型和空蚀预测方法，建立了离心泵转速和几何结构与空泡半径的函数关系。通过对不同比转速离心泵空化数值计算开展普适性评估，结果表明RZGB空化模型能够较准确的预测离心泵内的特殊三角空泡结构，以及更为显著的空穴尾端非定常现象。最后基于空化空蚀图像后处理研究方法以及RZGB空化模型，建立了离心泵空蚀预测方法。.通过本项目的研究，丰富了离心泵的空化空蚀理论，建立的空化与空蚀图像后处理研究方法可广泛应用于离心泵或其他水力装置中对空化和空蚀区域进行分析预测，为优化设计提供理论和数据支撑。