基于固液两相流的离心泵性能研究及优化设计

发布时间：2019-04-12 15:34

【摘要】：固液两相离心泵输送的是两相流介质,其内部流场与性能和清水泵差距甚大,由于固相的存在,使得泵存在扬程和效率低下,磨损严重等问题,导致两相流泵的工作效率低,使用寿命缩短。因此,进行固液两相离心泵优化设计,提高其各项性能至关重要,意义深远。本文应用商用ANSYS软件,采用CFD数值模拟,对固液两相离心泵进行CFD模拟计算并对其叶轮进行优化且进行数值模拟。本文主要工作如下:首先,对固液两相离心泵的全流道进行建模并划分网格,对所用网格进行无关性验证。对离心泵设定边界条件后进行了定常数值模拟,研究单一粒径条件下,离心泵在不同固相体积分数工况的流场特性。研究结果表明:离心泵的扬程随固相体积分数的增加先上升后下降,其效率持续下降,叶片所受压力逐渐增大,且压力面较吸力面增大幅度更大。其次,对泵在单一粒径和组合粒径条件下的磨损和空化性能规律进行了研究。研究结果表明:颗粒直径和固相体积分数是影响两相流泵磨损和空化性能的主要参数,组合粒径下磨损程度更深,主要集中在叶轮后盖板和叶片压力面,单一粒径下的磨损则集中在前盖板和叶片吸力面出口;固相颗粒对泵空化具有一定影响,主要集中在叶轮头部进口。然后,对离心泵进行叶轮改型设计,改变叶片安放角和叶片包角,二者均按β曲线变化且具有关联性,对改型前后的五种方案进行数值模拟。研究结果表明:当叶轮进口安放角与进口包角的比值过大或过小,均未有优化效果;当比值略小于原始方案时,泵的效率达到最高,为效率最优方案;当比值略高于原始方案时,高效率范围最大,为高效最优方案。最后,在定常计算的基础上进行优化前后的三种叶轮模型的全流道非定常模拟,研究叶轮压力脉动特性与频谱特性。研究结果表明:叶片安放角与叶片包角可以决定叶轮流道的宽窄,叶轮流道的宽窄影响着进出口的压力脉动与振动幅值,当进口安放角与包角比值略小时,流畅的压力脉动幅值较大,而原始方案和比值较大时,压力脉动幅值与频谱更为均匀。所做研究为叶轮流道宽窄对压力脉动的影响提供了一定的研究基础。
[Abstract]:The solid-liquid two-phase centrifugal pump conveys the two-phase flow medium. The internal flow field and the performance of the two-phase centrifugal pump are different greatly. Due to the existence of the solid phase, the pump has the problems of low head, low efficiency, serious wear and so on, which leads to the low working efficiency of the two-phase flow pump. The service life is shortened. Therefore, it is of great importance to optimize the design of solid-liquid two-phase centrifugal pump and improve its performance. In this paper, using commercial ANSYS software and CFD numerical simulation, the solid-liquid two-phase centrifugal pump is simulated by CFD and its impeller is optimized and numerically simulated. The main work of this paper is as follows: firstly, the whole channel of solid-liquid centrifugal pump is modeled and meshed, and the grid is verified independently. The steady numerical simulation of centrifugal pump is carried out after the boundary conditions are set, and the flow field characteristics of centrifugal pump under different solid volume fraction are studied under the condition of single particle size. The results show that the head of centrifugal pump increases at first and then decreases with the increase of solid volume fraction, the efficiency of centrifugal pump decreases continuously, the pressure on the blade increases gradually, and the pressure surface increases greatly than that of suction surface. Secondly, the wear and cavitation properties of the pump under the conditions of single particle size and combined particle size were studied. The results show that the particle diameter and solid volume fraction are the main parameters affecting the wear and cavitation performance of the two-phase flow pump, and the wear degree under the combined particle size is deeper, mainly concentrated on the pressure surface of the rear cover plate and blade of the impeller. The wear under single particle size is concentrated on the front cover plate and the outlet of suction surface of the blade. Solid particles have a certain impact on pump cavitation, mainly concentrated in the impeller head inlet. Then, the impeller design of centrifugal pump is carried out, and the vane setting angle and the blade envelope angle are changed. Both of them change according to the 尾 curve and have correlation. The five schemes before and after the modification are numerically simulated. The results show that when the ratio of the inlet angle to the inlet angle of the impeller is too large or too small, there is no optimization effect, and when the ratio is a little less than the original scheme, the efficiency of the pump reaches the highest, which is the optimal scheme. When the ratio is slightly higher than the original scheme, the range of high efficiency is the largest, and it is the most efficient and optimal scheme. Finally, the unsteady simulation of three impeller models before and after optimization is carried out on the basis of steady calculation, and the pressure fluctuation and spectrum characteristics of the impeller are studied. The results show that the blade placement angle and the blade envelope angle can determine the width and narrow of the blade channel, and the width of the blade channel affects the pressure fluctuation and vibration amplitude of the inlet and outlet, when the ratio of the inlet setting angle to the inclusion angle is a little smaller, and the width of the blade channel affects the pressure fluctuation and vibration amplitude of the inlet. The amplitude of pressure fluctuation is larger, but the amplitude and spectrum of pressure fluctuation are more uniform when the original scheme and ratio are larger. The study provides a basis for the study of the influence of blade channel width on pressure pulsation.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH311

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