为研究核主泵在不同工况下运行的瞬态特性，基于RNG k－ε模型采用CFX三维非定常数值模拟方法分析其在4种不同同心度下压力脉动变化规律。结果表明，改变偏心距并未改变叶轮主频，随偏心距增加叶轮内压力脉动幅值先减小后增大。各偏心距在不同工况下压力呈相似规律变化，且波动次数等于导叶数目，即叶轮内流动状态受导叶影响较大。小流量工况下脉动幅值随偏心距增加波峰出现位置逐渐向下一时刻推移，且不同偏心距下压力脉动幅值差别较大；设计工况下叶轮流道内压力脉动幅值波动明显小于小流量工况，出口压力脉动幅值远大于进口。大流量工况时叶轮内各监测点压力脉动幅值在各偏心距下从叶轮进口到出口均呈不稳定波动，波动幅值远大于设计工况。偏心距为10"15 mm时核主泵运行压力脉动最小。%Inordertostudythetransientdynamiccharacteristicsofanuclearmainpumpunderdifferent conditions,the pressure fluctuation under four different volute eccentricities were analyzed based on the RNG k-εmodel by using CFX three-dimensional unsteady numerical simulation methods.The results show that the change of eccentricity does not alter the dominant frequency of impeller,however,with the increasing of eccentricity,the pressure amplitude inside the impeller decreases first and then increases.The pressure has a similar changing trend for different eccentricities under different working conditions and the wave frequency is just equal to the number of guide vanes which indicates that the flow state inside the impeller is greatly influencd by guide vanes.Under small flow conditions,with the increase of eccentricity the peak of pressure fluctuation amplitude gradually delays to appear and the amplitude difference of the pressure fluctuation becomes larger under different eccentricities.Under the design working conditions,the fluctuation in the impeller flow passage is less than that under small flow conditions and the pressure amplitude at outlet is greater than at inlet.Under large flow rates,at monitor points,the pressure amplitudes within the impeller under different eccentricities from inlet to outlet are unstable,and the fluctuation amplitudes are greater than under the design conditions.The analysis results show that the pressure fluctuation of nuclear main pump under various operating conditions reaches its minimal when the eccentricity is within 10~15 mm.
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