【作者】 王磊；

【导师】 李伟；

【作者基本信息】 江苏大学 ， 动力工程及工程热物理， 2020， 硕士

【摘要】 碱液循环泵广泛应用于氯碱蒸发采盐等重要工业流程,主要用于输送氨盐水、热碱液、熔融碱和滤液等固液两相介质。结晶固体颗粒冲刷、强腐蚀的工作环境对碱液循环泵的性能和可靠性提出了相当苛刻的要求。伴随着氯碱工业绿色发展理念的贯彻,要求碱液循环泵更加节能高效。因此,本文将重点研究流量工况和颗粒物性参数对碱液循环泵内部流动的影响以及颗粒浓度对叶片力学性能的作用规律。本文在江苏省重点研发计划重点项目“高效化工流程碱液循环泵关键技术开发与应用(BE2015001-4)”资助下完成,对一台离心式碱液循环泵进行了数值计算研究。本文主要工作及成果如下:(1)基于数值计算研究了不同流量工况下叶轮和蜗壳内压力、速度和熵产分布,并对数值计算结果进行了实验验证。结果表明,设计流量下扬程与实验误差为4.69%,效率误差为1.07%。在靠近压力面中部区域始终存在低速区,面积与流量呈负相关。叶片表面湍流造成的能量耗散远大于黏度引发的耗散,且两种耗散集中分布于叶片进口轮缘处和叶片出口附近;随着流量增大,能量损耗较高的区域面积变大,在叶片表面呈现扩散分布趋势。蜗壳流道内涡流由近似对涡经过破碎、汇聚形成单涡,涡核偏移至壁面附近,影响的区域面积变大。(2)基于全因子试验与两相流双欧拉法计算,探究了不同物性参数与泵性能、颗粒流动规律之间的关系。结果表明,经过权重分析建立的颗粒物性参数与性能之间的回归方程在局部空间内预测精度达到99%。固相在叶片进口与吸力面中后部易出现速度陡降,吸力面受脱流影响,出口速度紊乱。颗粒直径与颗粒密度对流场的作用相似,任一参数增大,颗粒不断向叶片压力面和后盖板交界处迁移。颗粒浓度的增加导致叶轮出口颗粒尾迹带变宽,固液两相分离明显。流量变化对于颗粒堆积位置影响较小,对堆积程度影响较大。(3)研究了流量工况、颗粒质量(直径、密度)、颗粒浓度对叶轮和蜗壳内压力脉动及叶轮径向力演变规律的影响。结果表明,随着流量增大,脉动峰值及主频幅值均先减小后增大;两相流条件下最小脉动峰值所在的流量比单相流大。叶轮蜗壳处脉动主频幅值与浓度正相关,但随着颗粒质量变大,蜗壳处脉动峰值及主频幅值先减小后增大,主频为一倍叶频。单相流条件下叶轮径向力脉动峰值在1.2Q最小,而两相流条件下径向力在1.4Q处最小;颗粒质量的增加使得叶轮径向力脉动峰值先减小后增加,而浓度的增加使得径向力脉动峰值不断递增。(4)基于双向流固耦合研究了碱液循环泵单相及两相流耦合流场变化规律,分析了颗粒浓度对叶片应力变形作用。结果表明,考虑了转子结构域的耦合,压力、轴向力和扬程的波形及相位在耦合前后差距较小,但幅值均有小幅增加,两相流条件下更为明显。不同颗粒浓度下叶轮等效应力及变形总体与单相流分布相似,最大等效应力发生在叶片出口与盖板焊接区域,轮毂处最小;随着颗粒浓度的增加,叶轮最大等效应力不断减小,变形量不断增加。叶片根部各交线变形量从进口到出口不断增加,且与颗粒浓度正相关;叶片进出口靠近后盖板处等效应力激增,变形量衰减加快;受颗粒浓度增加影响,叶片根部动应力低频信号变得杂乱,主频幅值变大。更多还原

【Abstract】 Alkali circulating pumps are widely used in the important industrial processes such as evaporation and salt production of chlor alkali.It is mainly used to transport solid-liquid twophase media such as ammonia brine,hot alkali liquid,molten alkali and filtrate.The performance and reliability of the alkali circulating pump are demanded by the working environment of crystal solid particle erosion and strong corrosion.With the implementation of the green development concept of chlor alkali industry,it is required that the alkali circulation pump be more energy-saving and efficient.Therefore,this paper will focus on the effect of flow conditions and particle physical parameters on the internal flow of alkali circulation pump and the effect of particle concentration on the mechanical properties of blades.This article was completed under the support of the key project of Jiangsu Key R & D Program "Development and Application of Key Technologies for High-efficiency Chemical Process alkali Circulation Pumps(BE2015001-4)",and a numerical calculation study was carried out on a centrifugal alkali circulation pump.The main work and achievements of this paper are as follows:(1)Based on the numerical calculation,the distribution of pressure,velocity and entropy production in impeller and volute under different flow conditions are studied,and the numerical results are verified by experiments.The results show that the error of head and experiment is 4.69% and the error of efficiency is 1.07%.There is always a low velocity region near the middle of the pressure surface,and the area is negatively related to the flow rate.The energy dissipation caused by turbulence on the blade surface is far greater than that caused by viscosity,and the two kinds of dissipation are concentrated at the blade inlet flange and near the blade outlet;with the increase of flow rate,the area with high energy loss becomes larger,and the distribution trend of diffusion appears on the blade surface.The vortex in the volute channel is broken and converged to form a single vortex by an approximate pair of vortices.The core of the vortex moves to the vicinity of the wall,and the area affected becomes larger.(2)Based on the full factor test and two-phase flow double Euler calculation,the relationship between different physical parameters and pump performance,particle flow law is explored.The results show that the prediction accuracy of the regression equation between the parameters and the properties of particles is 99% in local space.The velocity of the solid phase in the inlet and the middle and back of the suction surface of the blade tends to drop sharply.The effect of particle diameter and particle density on the flow field is similar.With the increase of particle concentration,the wake band of particles at the impeller outlet becomes wider and the solid-liquid two-phase separation is obvious.The change of flow rate has little effect on the position of particle accumulation and has great effect on the degree of particle accumulation.(3)The effects of flow condition,particle mass(diameter,density)and particle concentration on pressure fluctuation and radial force evolution of impeller and volute were studied.The results show that with the increase of flow rate,the peak value and the main frequency amplitude decrease first and then increase;The flow rate of the minimum fluctuation peak in two-phase flow is larger than that in single-phase flow.The amplitude of the main frequency of the pulsation at the volute is positively related to the concentration,but with the increase of the particle mass,the peak value and the amplitude of the main frequency of the pulsation at the volute first decrease and then increase,and the main frequency is at the blade frequency.The peak value of radial force pulsation of impeller is the smallest at 1.2Q in singlephase flow condition and the smallest at 1.4Q in two-phase flow condition;the increase of particle mass makes the peak value of radial force pulsation of impeller decrease first and then increase,while the increase of concentration makes the peak value of radial force pulsation increase continuously.(4)Based on the two-way fluid-solid coupling,the flow field of single-phase and two-phase coupling of alkali circulation pump was studied,and the effect of particle concentration on stress and deformation of blade was analyzed.The results show that,considering the coupling of rotor structure domain,the difference of wave form and phase of pressure,axial force and lift is small before and after coupling,but the amplitude increases slightly,especially under the condition of two-phase flow.The distribution of equivalent stress and deformation of impeller under different particle concentration is similar to that of singlephase flow.The maximum equivalent stress occurs in the welding area of blade outlet and cover plate,and the minimum is at the hub;With the increase of particle concentration,the maximum equivalent stress of impeller decreases and the deformation increases.The deformation of each intersection line at the root of the blade increased from the inlet to the outlet,and was positively related to the particle concentration;The equivalent stress increases sharply near the back cover plate at the inlet and outlet of the blade,and the deformation decreases rapidly;the low frequency signal of the dynamic stress at the root of the blade becomes disordered and the main frequency amplitude becomes larger due to the increase of the particle concentration.更多还原