泵内气液瞬态流演变机理及其控制策略研究

The critical path to understand the gas-liquid mixing mechanism and optimize the self-priming capability and hydraulic performance of a self-priming pump is to investigate the evolution mechanism of gas-liquid transient flow and its control strategy. The gas-liquid mixed flow and its optimization control methods are the starting point of this project. The theoretical, numerical and experimental methods are used to understand the transient flow both in numerically and visualization. Also the imaging processing technologies are used to investigate the temporal and spatial characteristics of gas-liquid transient flow in self-priming pump. The evolution progress of gas volume fraction and bubble size in different areas of self-priming pump is revealed. Furthermore, the self-priming capability and hydraulic performance of self-priming pump models with different geometrical variants are investigated using the numerical and experimental methods. The influence of geometrical variants and inducers on the self-priming capability and hydraulic performance is revealed. The optimal objective functions are setup based on Kriging model and the NSGA II algorithm is used to search the optimal solution. The multi-objective optimizing control methods based on Kriging/NSGA II model are generated for optimizing the two-phase flow in self-priming pump. The outcomes of project provide a new explanatory on evolution mechanism of gas-liquid transient flow and its control strategy in the self-priming pump and enrich the fundamental theory of multi-objective optimization design method for self-priming pump. Finally, it can provide a theoretical support for optimizing the self-priming capability and hydraulic performance of self-priming pump.

泵内气液瞬态流演变机理及其控制策略的研究是掌握自吸泵自吸机理和改善自吸泵自吸性能和水力性能的关键途径。本项目以自吸泵气液混合流动及其优化控制策略为出发点，运用理论、数值与实验方法，对气液瞬态流结构进行数值及可视化研究，利用图像处理技术揭示空泡流的时空特征，定量探索不同区域内含气率及气泡尺寸的演化规律。采用数值和实验手段对不同几何参数方案下的自吸泵模型的自吸性能和水力性能进行研究，揭示水力几何参数及诱导轮对自吸性能和水力性能的定量影响关系。基于Kriging模型建立自吸泵设计指标的目标函数，采用NSGA II算法对目标函数进行最优化求解，建立基于Kriging/NSGA II模型的自吸泵多目标优化控制方法。项目研究成果将对自吸泵气液瞬态流的演变机理及其控制策略作出新的诠释，丰富自吸泵优化设计理论，为自吸泵的自吸性能及水力性能优化提供理论支撑。

自吸泵的自吸过程是复杂的高气相含量下的气液混合过程，当前泵内气相排出过程及机理未能得到完整揭示，在产品设计研发过程中仍采用半经验半理论方法。本项目以自吸泵为研究对象，结合数值模拟、可视化实验和计算机视觉等方法，研究了泵自吸过程中的气液混合过程和气液两相流分布时空演变规律，揭示自吸泵气液瞬态流的时空演变机理，完善了自吸泵性能影响关键因素及控制方法。结果表明：整个自吸过程中叶轮和蜗壳内的气相含量先上升后下降，出水管内的气相含量先下降后上升最后在自吸末期下降。随着自吸过程的发展，泵内的气泡数量呈现先快速上升，然后趋于稳定的规律，且与叶轮转速上升规律具有一致性。蜗壳扩散段的气泡直径主要在0.2-0.6mm左右，随着直径的上升数量呈现线性递减的规律，而泵体内回流气泡直径以0.4-0.5mm为波峰呈现正态分布。当储液量无法完全充满叶轮时，会导致自吸性能的显著下降；叶轮叶片数增加，使得泵内气液两相混合更充分，提高了排气效率，改善自吸性能，转速的上升会使得泵内含气量上升。此外，针对自吸泵通常用于输送含颗粒过流介质，研究了泵在输送固液两相流情况下的磨蚀特性，揭示了颗粒参数对过流部件的冲蚀特性以及泵性能的影响规律。提出了一种叶片自寻优设计方法，建立了叶片平均环量分布函数，实现了对离心叶轮优化设计。本项目的研究成果完善了自吸泵的气液瞬态流演变机理，为自吸泵产品设计提供可靠的理论支撑，有利于提高自吸泵自吸性能和运行可靠性。