部分进汽机组激振力特性研究

Research of Exciting Force of Turbine under Partial Admission

针对涡轮部分进汽时非定常流动特性及其产生的激振力问题,使用商业软件NUMECA对不同转速涡轮内的流动进行了数值模拟。计算非定常流动下动叶轴向力和切向力,同时分析动叶表面的压力变化,得到激振力序列,对激振力进行频谱分析。研究发现:在堵塞部分与进汽部分的交界处存在较大切向压力梯度,造成轴向力和切向力的急剧变化;部分进汽下,叶轮激振力在基频下谐波分量最大,各倍频谐波分量依次减小,且各转速激振力频率主要集中在10倍频以下,超过10倍频的谐波分量较小。相同进口总压下,轴向力谐波分量随转速增大而增大,切向力则相反,且切向力各倍频谐波分量大小差距随转速增大而减小。

The unsteady effect of turbine under partial admission will result in strong flow exciting force. Com- mercial software NUMECA to simulate the flow field is used. The flow characteristics of unsteady flow is observed. The axial thrust and tangential force on rotor blades is calculated. The frequency of exciting force and the change of surface pressure on rotor blades is analyzed. The simulation results show that： there are great tangential pressure gradient exits in the inlet and outlet blocked area of rotor blades, which cause the rapid change of the axial thrust and tangential force on rotor blades ; when the turbine is under partial admission. The harmonic component of excit- ing force in fundamental frequency is the largest, and frequency of exciting force is mainly concentrated below 10 times of fundamental frequency. When the inlet pressure is the same, the harmonic of axial force is reduced and that of tangential force is increased with the increase of rotate speed.