不同体型调压室的瞬态水力特性对比分析

由于地形特征和调压室断面积的不同,水电站调压室体型也多种多样,从而使水电站过渡过程具有不同的瞬态特性。本文采用基于特征线法的一维计算及基于CFD方法和VOF模型的三维计算,比较了T型截面调压室和π型截面调压室过渡过程中的瞬态水力特性。一维计算结果表明,两种体型的调压室涌浪及调保参数随时间的变化规律相同,且调保参数均在控制范围以内。一维与三维的结果基本一致,但三维计算可反映液面的真实波动,即T型调压室在机组甩负荷工况下产生较大的涌浪波动,启动工况下产生立轴旋涡,并迅速蔓延到升管内,可能会影响水电站的安全运行。而π型调压室中的水流流态较平稳,未产生吸气旋涡。因此,采用π型截面的调压室更符合工程需要。

Comparative analysis of transient hydraulic characteristics of a surge tank with different section form

There are varied forms of surge tank in hydropower stations considering the difference of terrain feature and surge tank sectional area,which makes the transition process of the hydropower station with var- ious transient characteristics. In this paper, the 1D calculation based on method of characteristics (MOC) and 3D calculation based on the computational fluid dynamics (CFD) method and VOF model were used to make a comparison of T-section and π-section surge tank to provide some references for such hydropow- er station. The 1D results show that the surge wave shares the same tendency of the two section forms. The 3D results demonstrate the large surging waves under load rejection condition and serious air-trapped vertical vortices under start-up condition of the T-section surge tank. The air-trapped vertical vortices ap- pear on the liquid level and extend to the connection pipe with the flow,some bubbles even spread to the penstock. The appearance of air-trapped vertical vortices may affect the safe operation of hydropower sta- tion. While the transient flow in π-section surge tank is more stable and without appearance of the air-trapped vertical vortices. So,π-section surge tank is recommended.