泵自吸过程气液两相流动特性及自吸机理的研究

Self-priming pumps are applied widely in many situations, such as movable irrigation, frequently starting, difficultly filling water. Since the gas-liquid flow in the self-priming process in the pumps is too complicated to grasp the self-priming mechanism by now, the lack of the self-priming mechanism has become a bottleneck of the futher development of self-priming pumps..The project will focus on the transient gas-liquid two-phase flow during the self-priming. The experimental system will be built to test the inner flow characteristics and outer self-priming performance of the pump. The dynamic flow processes will be researched in details, such as gas-liquid suction, gas-liquid mixture, gas-liquid separation, gas exhaustion and liquid return. Combined with the experimental transient results, the flow field will be simulated transiently applying multi-phase Euler models jointed with slipping grid technology. The mathematical models and calculation methods of the flow inside the pump will be built, and the 3-demensional numerical simulation to describe the flow inside the pump during the self-priming will be realized at first home and abroad. The inner flow characteristics are linked with the outer self-priming performances by the research on the states of the key monitoring points. The influences on the self-priming performances by the hydraulic structures and the running parameters will be obtained further. .Based on the research on the gas-liquid two-phase flow in the pump during the self-priming, self-priming mechanism will be mastered, self-priming performance will be predicted and the theoretical hydraulic design method will be established, which will provide a theoretical basis for developing new and high level self-priming pumps.

自吸泵广泛应用于移动排灌、启动频繁和灌液困难等场合。由于自吸过程中气液两相流动非常复杂，自吸机理尚未掌握，已成为制约泵自吸技术发展的瓶颈。.项目将针对自吸过程气液两相瞬变流动开展研究。建立泵自吸过程气液两相流动特性与自吸性能外特性协同测试系统，研究泵内气液吸入、气液混合、气液分离、气体排出和液体回流的详细流动过程；结合气液两相流动瞬态测试数据，采用多相流欧拉分析方法结合滑移网格技术，对泵自吸过程开展非定常瞬态模拟研究，建立合适的数学模型与计算方法，首次实现泵自吸过程气液两相流动的三维数值计算。通过研究自吸关键监测点的流动状态，建立泵内部流动特性和自吸外特性之间的内在联系，研究泵水力结构、运行参数等对自吸流动过程的影响。.本项目旨在揭示自吸过程中气液两相流动规律，掌握自吸机理，预测自吸性能，建立自吸泵原理性水力设计方法，为开发新型高性能自吸泵提供理论依据。

自吸泵广泛应用于移动排灌、启动频繁和灌液困难等场合。由于自吸过程中气液两相流动非常复杂，自吸机理尚未掌握，已成为制约泵自吸技术发展的瓶颈。.为分析泵自吸过程气液两相流动特性，掌握泵的自吸机理，本文建立泵自吸过程内外特性协同测试系统，实现对65ZB-40C型外混式自吸泵进出口压力、流量以及泵转速的瞬态测试，得到泵自吸性能和水力性能；同时采用高速摄影技术对自吸过程中泵叶轮、气液分离室和蜗壳出口段内气液两相流动过程进行拍摄，并基于MATLAB对拍摄到的数字图像进行处理，研究气液混合和气液分离过程中气液两相流中气泡的大小、形态和运动规律。采用欧拉多相流模型、标准 湍流模型结合滑移网格技术并通过UDF功能加载试验所得的叶轮转速和出口压力曲线，对泵自吸过程的气液两相流动进行数值模拟，并与试验结果进行对比。研究结果表明，气液分离和气液混合过程总是伴随着气泡的生成、溃灭、聚并、分裂，自吸过程可以分为自吸启动过程(0-3s)，自吸稳定过程(3-20s)和自吸突变过程(20-30s)。叶轮进口处的气相空穴和叶轮外缘的均匀的气液混合层是泵稳定自吸的必要条件；自吸稳定过程占自吸时间的比例最大，对自吸性能影响最大；在气液分离室内大气泡分裂成小气泡有利于气体的排出；扩散段出口小气泡聚并变成大气泡并在出口处震荡、回旋，不利于气体的排出，同时造成了能量的损失。叶轮与隔舌间隙越小，经过隔舌进入蜗壳扩散段的气泡直径越小，形成的气泡群更容易排出泵体，有利于自吸性能的提高。.本项目丰富了流体机械内部瞬态流动过程的研究，对旋转机械内部两相流动、非定常瞬态流动的数值模拟方法和试验研究有重要的参考意义，同时自吸过程气液两相流动特性以及自吸机理的研究是创新自吸结构、提高自吸性能以及开发新产品的基础，为开发新型高性能自吸泵提供了理论依据，具有十分重要的理论研究价值与实际应用意义。