离心泵作透平系统变转速及过渡过程研究

发布时间：2018-06-01 07:29

本文选题：离心泵作透平 + 变转速　；参考：《华南理工大学》2016年博士论文

【摘要】：能源发展面临着需求压力巨大、能源供给制约较多、能源生产和消费对生态环境损害严重、能源技术水平总体落后等挑战。当前全球都在经历新一轮的能源技术革命,以绿色低碳为导向,节能高效的能源技术已上升到国家发展和安全的战略高度。泵反转作液力透平被称为pump as turbine(PAT),这种能量回收装置应用于石油化工、冶金、煤炭以及废水处理等行业的中,回收介质中的余压能量,达到节能降耗的效果。目前,在上述工业关键领域,几乎全部采用进口透平机组回收液体余压能量,国内制造商面临的问题主要是回收率低和可靠性不高的问题。就工业应用来讲,着眼整个透平系统,考量装置运行安全性的研究,尤其是系统的瞬态效应,包括变转速的过渡过程,都是很有价值的议题。本文从内在的科学问题出发,针对泵作透平系统变转速及过渡工况特性进行研究,从透平的选型和性能预测,到透平系统的搭建和参数匹配,从设计转速工况到其它转速工况,再到连贯的过渡工况,本文从理论、数值计算和试验等三个方面进行了有针对性的研究。本文开展的研究工作如下:(1)PAT系统不同过程的试验和数值计算策略类比了工业测试和实验室研究用的离心泵作透平试验台的特点,针对PAT系统的稳态、准稳态和过渡过程提出合理的试验方案,搭建了相应的试验台和控制系统,成功实现了泵作透平瞬态过渡过程的性能测试和振动测试等;对比了相同过渡工况下雷诺平均法和大涡模拟法的计算结果,在稳态计算的基础上,提出了较为完善的过渡态数值计算策略,通过CFX-CEL和User Function实现对不同转速的定义,获得过渡过程的PAT内流和瞬变特征,并通过试验验证。(2)基于蜗壳和转轮匹配理论的运行工况点预测和PAT系统配置参照经典一元离心泵叶轮和蜗壳的匹配性理论,通过理论分析推导了考虑了叶片出口滑移和有限叶片数效应的透平转轮特性方程,提出了PAT最优工况点参数的预测公式和相应的泵与透平性能换算公式,该式不以比转速为变量,实例验证其具有较高的精度;研究了不同的负载泵对PAT系统的影响,探讨了高效PAT系统中PAT和负载的参数匹配特征,二者的最佳参数范围为/0.4~0.6T PQ Q=,/3.57~4.35T PH H=,揭示了变转速过程中负载和系统的性能特性。(3)恒定转速下PAT内流和外特性借助CFD研究了设计转速下PAT的内流场和外特性。重点探究了非定常工况下PAT流动域内的流场变迁、流量分配和水力载荷等问题,提出了内流场流量分析法,直观地揭示了PAT计算中简化前后泵腔误差较大的内流场机理,即前后泵腔和环形间隙的显著分流和流动损耗,发现流体在一些固定区域由环形区域进入两侧泵腔,而在另一些区域流回环形空间;监测了拉格朗日和欧拉观点下的转轮瞬时流量信息,一定程度上量化了流场的演变特征,为相关研究提供了借鉴;研究了设计转速下不同工况的水力损失分布,转轮水力载荷和压力脉动,以及轴向力和径向力等特征。(4)变转速下PAT的内流和外特性探讨了PAT的转速特性曲线和不同BEP点(最佳效率点)的内流场分布,发现不同转速和工况点下PAT的运行效率相差很大,研究透平系统变转速运行的一般规律具有显著的效益;选取了三个典型的不同转速BEP工况点,研究了其流场差异、叶片载荷、径向力、轴向力和水力脉动等参数的变化特征,即不同BEP点水力稳定性研究。结果表明,PAT的径向力和轴向力在幅值上总体上远小于水泵。随着转速的增加,轴向力逐渐增大且脉动加剧,PAT偏离设计工况和转速运行时蜗壳内压力脉动幅值有所增加,振动试验与压力脉动计算结果相一致。(5)PAT系统过渡过程下的瞬变特性研究分析了广义欧拉方程在水力机械中的应用,发现其不能直接用于计算PAT过渡过程的瞬态扬程;对PAT系统的转子进行了整体转动分析,确立了过渡过程流动域瞬态计算的整体策略;数值计算了恒压加减速和恒流加减速四个类型下的PAT瞬态流场,分析了该过程PAT的瞬态性能参数变化和流场演变特征,发现准稳态计算的数值大于过渡态计算和试验数值,过渡过程的计算值略大于试验值,计算与试验吻合较好;通过PAT内流场分析,发现过渡过程中流线分布和叶道涡的位置有显著的变化,流场最紊乱的时刻发生在过渡工况的起始时刻;通过非线性的转速函数优化了过渡过程的计算,获得了PAT和负载同步的计算结果,提升了过渡过程数值计算的精度;在特定的过渡工况计算模型中加入空化模型,获得了显著的汽蚀效应,证实了二者之间的相关性。
[Abstract]:Energy development is facing the challenges of huge demand pressure, more constraints of energy supply, serious energy production and consumption, serious damage to the ecological environment and the overall backward energy technology level. The current world is experiencing a new round of energy technology revolution, guided by green low-carbon, and energy saving and high efficiency energy technology has risen to national development and security. The hydraulic turbine is called pump as turbine (PAT). This energy recovery device is applied to the petrochemical, metallurgical, coal and wastewater treatment industries, and the residual pressure energy in the recycled medium can achieve the effect of energy saving and consumption reduction. At present, almost all of the key fields in the industry are used for the import of the imported turbine unit. The problem that the domestic manufacturers face is the problem of low recovery and low reliability. In terms of industrial applications, the research on the safety of the whole turbine system and the operation of the equipment, especially the transient effect of the system, including the transition process of the variable speed, is a very valuable issue. This article from the internal scientific problem. According to the research on the variable speed and transition condition characteristics of the turbine system, from the type selection and performance prediction of the turbine to the structure of the turbine and the matching of the parameters, from the design of the rotational speed to the other speed conditions, and then to the coherent transition condition, this paper has carried on the pertinent research from three aspects, the theory, the numerical calculation and the experiment. The research work of this paper is as follows: (1) the characteristics of the centrifugal pump used in the industrial test and the laboratory research are analogous to the characteristics of the centrifugal pump used in the industrial test and laboratory research, and the reasonable test scheme for the steady state, the quasi steady state and the transition process of the PAT system is proposed, and the corresponding test bed and control system are set up in the PAT system. The performance test and vibration test of the pump as the transient transition process are realized, and the results of the Reynolds mean method and the large eddy simulation method are compared under the same transition conditions. On the basis of the steady state calculation, a more perfect transition state numerical calculation strategy is put forward, and the definition of different rotational speeds is realized through CFX-CEL and User Function. The PAT internal flow and transient characteristics of the transition process are obtained and verified by experiments. (2) based on the operating condition point prediction of the worm shell and wheel matching theory and the matching theory of the classic one element centrifugal pump impeller and the volute with the PAT system configuration, the turbine runner with the effect of blade slip and finite blade number is derived by theoretical analysis. The characteristic equation, the prediction formula of PAT optimal operating point parameters and the corresponding formula of pump and turbine performance are put forward. This formula does not use the specific speed as the variable, the example verifies its high precision. The influence of different load pumps on the PAT system is studied, and the parameters matching characteristics of the PAT and load in the high efficiency PAT system are discussed, and the best two are the best. The parameter range is /0.4~0.6T PQ Q= and /3.57~4.35T PH H=, which reveals the performance characteristics of the load and the system in the process of variable speed. (3) the internal flow and external characteristics of PAT at design speed are studied with CFD at constant speed at the constant speed. The flow field, flow distribution and hydraulic load in the unsteady state of the PAT flow field are focused on. The flow flow analysis method of internal flow field is put forward to reveal the internal flow mechanism of the large error of the pump cavity before and after the simplified PAT calculation, that is, the significant shunt and flow loss of the front and back pump cavity and the annular gap, and find that the fluid enters the two side pump chambers from the annular region in some fixed areas and flows back to the annular space in some other regions; The instantaneous flow information of the runner in Lagrange and Euler's point of view quantifies the evolution characteristics of the flow field to some extent and provides reference for the related research. The hydraulic loss distribution in different working conditions at the design speed, the hydraulic load and pressure pulsation of the wheel, and the axial force and radial force are studied. (4) the internal flow of PAT under the variable speed and the internal flow of the rotating speed. The external characteristics of the PAT speed characteristic curve and the internal flow field distribution of different BEP points (the best efficiency point) are discussed. It is found that the operating efficiency of PAT at different rotational speeds and working conditions is very different. The general rule of the variable speed operation of the turbine system has significant benefits, and three different speed BEP operating points are selected, and the flow field difference is studied. The variation characteristics of the parameters such as the load of the blade, the radial force, the axial force and the hydraulic pulsation, that is, the hydraulic stability of different BEP points. The results show that the radial force and the axial force of the PAT are generally far smaller than the water pump. With the increase of the speed, the axial force increases gradually and the pulsation increases, and the PAT deviates from the design condition and the speed of the spiral case. The amplitude of pressure fluctuation is increased, and the vibration test is in agreement with the calculation results of pressure pulsation. (5) the transient characteristics of the PAT system under the transition process are studied and analyzed in the application of the generalized Euler equation in the hydraulic machinery. It is found that it can not be used directly to calculate the transient head of the PAT transition process; the whole rotation analysis of the rotor of the PAT system is true. The overall strategy of transient calculation in the flow field of the transition process is established. The PAT transient flow field under four types of constant pressure plus deceleration and constant current plus deceleration is numerically calculated. The transient performance parameters and the flow field evolution characteristics of the PAT are analyzed. It is found that the numerical value of the quasi steady state calculation is greater than the transition state calculation and the experimental values, and the calculation values of the transition process are calculated. It is a little bigger than the test value, and the calculation is in good agreement with the test. Through the analysis of the flow field in PAT, it is found that the distribution of streamline and the position of Ye Daowo in the transition process have a significant change, the most disordered time of the flow field occurs at the beginning of the transition condition, and the calculation of the transition process is optimized through the nonlinear rotational speed function, and the synchronization of the PAT and the load is obtained. The calculation results improve the accuracy of the numerical calculation of the transition process, and the cavitation effect is obtained by adding the cavitation model in the specific transition working model, which confirms the correlation between the two.
【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TH311

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