离心泵启动过程的瞬态内流和外特性

发布时间：2018-04-10 11:02

本文选题：离心泵 + 固液两相　；参考：《浙江大学》2013年博士论文

【摘要】：离心泵通常主要在稳定工况下运行,其工作转速、工况等基本不变或者变化非常缓慢,因此对离心泵的研究主要集中在稳定工况下进行。随着离心泵应用领域的拓展以及系统复杂程度的提高,离心泵也会在非稳定工况下运行,如启动、停机和转速变化等瞬态工况,离心泵在非稳定工况运行的水力性能日益受到重视,因此非常有必要开展离心泵在瞬态工况下的性能研究。本论文以在瞬态工况下运行的离心泵为研究对象,重点对启动过程中的水力性能进行了较为详细和深入的系统研究,获得了当输送介质中含有固体颗粒时的离心泵瞬态启动特性。论文首先根据动量矩定理提出了一种描述不可压缩流体机械瞬态操作条件下性能的广义欧拉方程式,借助于该方程式开展离心泵在各类瞬态操作条件下附加理论扬程的定量计算；其次,运用动网格方法进行了离心泵启动过程的数值仿真计算研究,建立了基于数值模拟的离心泵瞬态性能研究方法；再次,开展了离心泵启动过程的外特性实验测试研究,借助于无量纲分析方法揭示了离心泵启动过程的瞬态特性；最后,采用数值模拟方法开展了离心泵输送介质中含固体颗粒时的启动过程流动计算,获得了其瞬态特性。论文的主要研究工作如下： 1.从动量矩定理和水力机械内部流动理论出发,推导了一种描述不可压缩流体机械瞬态操作过程性能的广义欧拉方程式。该方程式可较全面地反映了整个叶片厚度变化和叶片型线变化对附加理论扬程的影响,并可被用于泵、风机、透平等不可压缩流体机械在各类瞬态操作过程中的附加理论扬程(或压头、压升)的定量预测。 2.运用动网格方法开展了离心泵输送清水介质时的快速启动过程的数值模拟研究,建立了基于数值模拟的离心泵瞬态操作过程的研究方法。论文研究工作中,建立了一个包含离心泵模型在内的循环管路系统,并在系统中设置了定压点,数值模拟中对整个系统进行计算。通过数值计算获得了启动过程中的许多特性,包括外特性的变化和内部流场的演化特性。进口压力呈现先降后升特性,流量在启动初期上升较为缓慢。无量纲流量在初始阶段快速上升至稳定值；无量纲扬程在启动初始阶段存在极大值,随后迅速下降低于准稳态值,而后又不断上升接近于准稳态值。 3.在所搭建的离心泵瞬态性能测试实验台上,对三种典型叶轮结构(普通闭式叶轮、复合叶轮和开式叶轮)的离心泵进行了清水介质的启动过程实验测试研究。通过实验获得了启动过程中转速、流量、扬程和轴功率随时间的变化结果,分析了各个物理量的变化特性。启动过程中转速上升规律基本稳定,不依赖于启动后稳定工况点的变化而变化；流量在启动初期上升较为缓慢,延迟于转速而上升到稳定值,并且随阀门开度的增加延迟变得更为严重；在启动过程中普遍存在压力冲击和轴功率冲击现象。 4.首先采用基于欧拉-欧拉方法的多相流模型,对固液两相流中固相属性对水力输送性能的影响以及泵流道内固体颗粒的分布进行了数值计算研究,分析了内部流场的变化特性。在离心泵启动实验中获得的转速与流量测试结果基础上,编写用户自定义函数施加到泵叶轮上和进口处充当计算边界条件,采用动网格方法开展了离心泵输送介质中含固体颗粒时的启动计算。研究发现当输送介质发生变化时,启动过程所表现出的性能差别是非常大的。启动前期瞬态性能基本相同,差别主要集中在启动后期；输送固液两相流时的扬程呈现先升后降的变化特性,明显区别于介质为清水时的持续上升趋势；当输送介质含固体颗粒时,扬程滞后于清水介质时的情形而达到稳定状态。
[Abstract]:Centrifugal pumps usually run in stable condition, the working speed, working basic constant or change very slowly, so the research of centrifugal pump is mainly concentrated in the stable condition. With the application development of the centrifugal pump and the increase of system complexity, centrifugal pump will run in unsteady conditions such as start, stop and speed change of transient conditions, the centrifugal pump becomes more and more important in the hydraulic performance of non steady operation, so it is very necessary to carry out research on the performance of centrifugal pump under transient conditions.
In this paper, a centrifugal pump running in transient conditions as the research object, focusing on the hydraulic performance in the process of starting a more detailed and in-depth study of the system, the centrifugal pump transient when the transport medium containing solid particles when the starting characteristics. Firstly, according to the momentum moment theorem is proposed to describe not the generalized Euler equation of compressible fluid mechanical properties of transient operating conditions, with the help of this equation to carry out quantitative pump additional theoretical head in all kinds of transient operating condition are calculated; secondly, using the dynamic mesh method obtained from numerical simulation of heart pump start calculation in the course of study, a numerical simulation method based on the study on the transient performance of centrifugal pump again, the external characteristics; experimental study of centrifugal pump during starting period, with the help of dimensionless analysis method to reveal the transient of the centrifugal pump during starting period In the end, the numerical simulation method is used to carry out the calculation of the starting process flow of the solid particles in the conveying medium of the centrifugal pump, and the transient characteristics are obtained.
The main research work of this paper is as follows:
Starting from the 1. theorem of moment of momentum and hydraulic mechanical flow theory, generalized Euler equation is derived to describe an incompressible fluid mechanical transient operation process performance. This equation can reflect the influence of the blade thickness and the blade profile changes on the theory of additional lift, and can be used to pump air. Additional theoretical lift machine, such as turbine incompressible fluid in various types of machinery during transient operation (or pressure, pressure rise) quantitative prediction.
2. simulation study using dynamic mesh method to carry out a centrifugal pump water medium fast startup process is developed based on the numerical method of centrifugal pump transient process based on numerical simulation. The research work, establish a complete model of centrifugal pump, circulation system, and set up a constant pressure point in the system in the calculation of the whole system. The numerical simulation obtained by numerical calculation. Many characteristics in the starting process, including the evolution characteristics of external characteristics and internal flow field changes. The inlet pressure is decreased and then the flow characteristics in the early start to rise more slowly. The dimensionless flow in the initial stage of rapid rise to a stable value; the dimensionless head in the initial stage of starting up the maximum value, then decreased rapidly than the quasi steady value, and then rising close to the quasi steady state value.
3. in the transient performance of centrifugal pump test bench is built on three kinds of typical structure of impeller (ordinary closed impeller, complex impeller and open impeller centrifugal pump) were studied experimental start-up process of water. Through the experiment speed, start the process of the flow, the changes of head and shaft power over time, to investigate the characteristics of various physical quantities. During the startup speed rise of basic stability, does not depend on changes in the starting point and the stable condition after change; flow increases slowly in the early start, delay in speed and rise to a stable value, and with the increase of valve opening delay becomes more serious there; pressure shock and shaft power shock phenomenon during startup.
The first 4. phase flow model based on Euler Euler method, the effect of solid phase properties of solid-liquid two-phase flow on the transmission performance of hydraulic pump flow and distribution of solid particles was studied numerically, analyzed the change characteristics of the internal flow field of centrifugal pump. In the experiment the speed and flow on the basis of the test results and write user defined functions applied to the pump impeller and inlet as boundary condition, the dynamic mesh method containing solid particles in the conveying medium when starting the calculation of centrifugal pump was carried out. The study found that when the transmission medium is changed, the performance difference is shown in the starting process is very large. Before the start of transient performance the same, the difference is mainly concentrated in the late start; transportation of solid-liquid two-phase flow when the head changes characteristics at first and then decreased, significantly different from the medium water holding time The rising trend is continued. When the medium contains solid particles, the lift falls behind the water medium and reaches a stable state.

【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TH311

【参考文献】