为研究离心泵作透平(PAT)启动过程中的瞬态特性,根据转动方程编写UDF程序,基于Fluent滑移网格的转速控制方法对PAT启动过程进行模拟计算,并与试验结果进行对比验证。结果表明:启动初始时刻叶轮内形成了强烈的叶道涡,随着转速的增加,叶道涡的强度逐渐减小,压力呈梯度分布。启动初始时刻叶片载荷振荡分布,最大振幅出现在叶片中间位置,远高于稳态工况下的叶片载荷;径向力和轴向力都随着转速的增加急剧增大后振荡下降,当转速趋于稳定后,径向力和轴向力呈周期性振荡,轴向力脉动的幅值小于径向力的,每个振荡周期的脉动次数与叶片数一致。启动过程中转子做加速度逐渐减小的加速转动,來流压力越大,达到设计转速的时间越短,完成启动后的稳定转速越高;转动惯量越小,完成启动越快。
Abstract
In order to study the transient characteristics of centrifugal pump as turbine (PAT) in the process of startup, UDF programs were written according to the rotation equations. Rotational speed control method based on Fluent sliding mesh was used to carry out numerical simulation of PAT during startup process, which was compared with the experimental results. The results show that strong leaf vortices are formed within the impeller at the initial time of startup, besides, the intensity of blade vortex decreases gradually and the pressure assumes gradient distribution with the increase of rotational speed. Blade load shows oscillatory distribution at the initial time of startup, and its maximum amplitude appears in the middle of the blade position, which is much higher than blade load of steady state condition. Radial force and axial force both increase sharply with the increase of rotational speed but decrease oscillatorily soon afterwards. After the rotational speed intends to be stable, radial force and axial force assume periodic oscillation. Pulse amplitude of axial force is less than that of radial force, and each pulse frequency of the oscillation period is consistent with leaf number. The acceleration of rotor decreases gradually in the process of startup, moreover, the greater pressure of flow fluid is, the shorter time is to meet the design speed, and the higher the steady speed is after completion of startup. The smaller the moment of inertia is, the faster startup is completed.
关键词
泵作透平 /
启动过程 /
转速 /
瞬态特性
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Key words
pump as turbine /
startup process /
rotational speed /
transient characteristic
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