离心叶轮流场对进口压力脉冲的响应分析

Analysis of Flow Response to Intake Pressure Pulse in a Centrifugal Impeller

关键词:  离心叶轮  流场响应  压力脉冲  数值求解  时空分布 

Key words:  Centrifugal impeller  Flow response  Pressure pulse  Numerical solving  Time-space distribution

摘要:

为研究离心叶轮流场对进口压力脉冲的响应特性,根据推导出的相对坐标系下HLLC通量算式,自行开发了基于多块结构化网格的叶片机流场分析程序。首先对跨声Krain叶轮和亚声径向叶轮展开算例考核,程序计算的性能曲线和叶表压力数据与试验和商业软件的结果吻合较好,且具有较商业软件更快的计算速度。之后以径向叶轮为对象,数值求解其内流场对进口压力脉冲的响应,对结果的分析表明:脉冲越尖,上下游流场变化越不同步,导致出口流量和气动力矩峰值时刻的延迟,流场压力的时空分布找不到时间对称轴。叶片载荷的空间分布特征不因脉冲宽窄和时间推进而改变,脉冲越宽,流场受扰变化时间越长,载荷峰值就越偏离稳态值。流场密度的变化值在不同时刻的空间分布是近似的。 

Abstract:

In order to investigate the flow response of centrifugal impeller to intake pressure pulse, a flow-field analysis code for turbomachinery based on multi-block structured grids was developed independently, according to the deducted HLLC fluxes of convection terms in the relative coordinate system. Firstly the numerical examples of transonic Krain impeller and a subsonic radial impeller were carried out. The calculated performance curves and surface pressure distribution show favorable agreement with the data from test and commercial software, and furthermore, the code possesses a higher computing speed than the commercial software. Then taking the radial impeller as the research object, the flow responses to different inlet pressure pulses were simulated. The results indicate that, the upstream and downstream flow fields will be more non-synchronous when the pulse becomes sharper, which causes the delay of peak value moment of outlet mass flow and aerodynamic moment, and furthermore, makes the time-space distribution of pressure lose the symmetry axis of time. The characteristic of space distribution of blade load does not change with the variation of pulse width and time marching. The wider the pulse is, the longer the flow field changes, which causes the peak value of load to deviate further from the steady state. The space distribution of density variation is similar at different times.