贯流式水轮机增负荷过程的动态特性研究

Dynamic Characteristics Analysis of Tubular Turbine During Load Increase

新型电力系统结构下的卧式低水头贯流式电站,由于负荷的频繁变化所引起的水力冲击与水体重力引起的不平衡水力因素联合作用使得变负荷运行状态更加恶劣。为改善贯流式水轮机变负荷过程中动态品质,在考虑自由液面和水体重力的情况下,基于动网格技术对增负荷过程中内部流场流动特征和振动特性进行数值模拟。研究发现:受自由液面和水体重力影响,除机组内的压力分布均呈现出由顶部到底部压力逐渐增大的规律;增负荷过程中,随着桨叶角度的增大,来流撞击位置向吸力面偏移,头部低压区逐渐向压力面偏移,叶片吸力面的低压区面积增加;转轮区域由于尾水管的0.1 f_(n)低频压力脉动和转轮的旋转引起的3 f_(n)高频压力脉动的共同作用,成为贯流式水轮机的主要振动区域。

Under the structure of the new power system,horizontal low-head tubular hydropower stations experience e-ven more severe variable load operation due to the combined effects of hydraulic impacts caused by frequent load chan-ges and unbalanced hydrodynamic factors induced by the gravity of water bodies.In order to enhance the dynamic per-formance of bulb tubular turbines during variable load conditions,numerical simulations were conducted to analyze the flow characteristics and vibration behavior within the turbine during load increase,considering the free surface and wa-ter body gravity,based on dynamic mesh technology.The results are as follows.Influenced by the free surface and wa-ter body gravity,the pressure distribution within the unit generally increases from the top to the bottom.During the load increase process,as the blade angle increases,the position of incoming flow impact shifts towards the suction sur-face,causing the low-pressure region at the head to gradually shift towards the pressure surface,and the area of the low-pressure region on the suction surface of the blade expands.The runner region becomes the primary vibration area of the tubular turbine due to the combined effect of 0.1 f_(n) low-frequency pressure pulsations originating from the tailrace and 3 f_(n) high-frequency pressure pulsations induced by the rotation of the runner.