电站离心风机旋转失速的数值模拟研究

发布时间：2018-04-20 22:25

本文选题：翼型 + 离心风机　；参考：《华北电力大学》2011年硕士论文

【摘要】：G4-73型离心风机广泛应用于300MW及其以下火电机组,由于负荷变动、积灰或者安装质量等原因,风机经常在小流量工况下运行,在此类工况下运行的风机往往会出现旋转失速,甚至会出现喘振等流动失稳现象,直接威胁机组的安全运行。深入研究风机发生旋转失速的非稳态流动特性,对提高离心风机的运行效率、扩大稳定运行范围具有实际意义。本文采用Fluent软件,首先利用二维不可压缩雷诺时均方程、基于Realizable k ?ε紊流模型,对风机翼型在不同冲角下的流动情况进行了详细的数值模拟,研究了风机翼型在低雷诺数下的失速特性,分析讨论了翼型的分离流动以及冲角与分离点位置的关系。结果表明,随着冲角的增大分离点位置逐渐向翼型前缘移动,直至进入失速状态,进入失速的翼型吸力面近壁处出现了强烈的漩涡。本文基于Fluent软件提供的用户接口-用户自定义函数(UDF)进行编程,得到在风机出口所假设的节流阀模型,通过连续调节节流阀阀门开度,实现了G4-73型离心风机在小流量下旋转失速现象的全流场数值模拟。对设计工况下和失速工况下的流场进行对比,分析研究了失速过程中不同阶段下瞬时速度场和瞬时压力场。结果表明,随着阀门开度的减小,风机逐渐进入失速区域,叶轮内出现了明显的低速区,在靠近前盖板附近区域首先出现了逆流;随着时间步的推进,逆流逐渐扩散到后盖板,直至充满整个流道。
[Abstract]:G4-73 centrifugal fan is widely used in thermal power units under 300MW and below. Due to load change, ash accumulation or installation quality, the fan often runs under small flow condition, and the fan running under this kind of working condition often appears rotating stall. Even surge and other flow instability phenomenon will directly threaten the safe operation of the unit. It is of practical significance to study the unsteady flow characteristics of fan with rotating stall in order to improve the efficiency of centrifugal fan and expand the stable operation range. In this paper, Fluent software is used to simulate the flow of fan airfoil at different angles of attack by using two-dimensional incompressible Reynolds time-averaged equation and based on Realizable k? 蔚 turbulence model. The stall characteristics of fan airfoil at low Reynolds number are studied. The separation flow of the airfoil and the relationship between the angle of incidence and the position of the separation point are discussed. The results show that with the increase of the angle of incidence, the position of the separation point gradually moves to the front edge of the airfoil until it enters the stall state, and a strong vortex appears near the wall of the stall airfoil suction surface. Based on the user interface provided by Fluent software, user defined function (UDF), the throttle model assumed at the outlet of the fan is obtained, and the throttle valve opening degree is adjusted continuously by adjusting the throttle valve opening continuously. The numerical simulation of rotating stall phenomenon of G4-73 centrifugal fan under small flow rate is realized. The instantaneous velocity field and instantaneous pressure field in different stages of stall process are analyzed and studied by comparing the flow field under the design condition and the stall condition. The results show that with the decrease of valve opening, the fan gradually enters the stall area, and there is an obvious low speed zone in the impeller, and the reverse flow occurs first in the area near the front cover plate, and with the advance of the time step, the countercurrent gradually diffuses to the back cover plate. Until the entire channel is filled.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TH432

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