多能互补条件下转轮优化对水轮机低负荷区稳定性能的影响

多能互补系统中新能源发电的不稳定性使得作为调能机组的水电机组频繁在水力效率低、振动剧烈的低负荷区运行，严重影响机组的寿命。该研究以多能互补系统中的混流式水轮机为研究对象，在前期考虑工况权重系数的转轮多工况优化设计结果基础上，对比分析了优化前后转轮叶片的几何参数变化，不同负荷区的水轮机内部流动状态及压力脉动特征差异。研究结果表明：优化后叶片包角、安放角以及叶片长度均有所增加，叶片表面压力分布及转轮进出水边速度矩分布更加均匀，有助于改善水轮机低负荷区的空化性能、提高能量转换能力。转轮进出口安放角的增加很好地抑制了转轮进口背面脱流涡及出水边的脱流涡区，改善了尾水管的入流条件，使得尾水管涡带的强度和影响范围明显减小。叶片优化后，转轮内各频率的压力脉动幅值均有不同程度的降低，尾水管内压力脉动改善明显。尾水管内0.2f_n(f_n为转频)和14f_n压力脉动在低负荷工况(OP1)幅值降幅分别为45%和40%，额定工况(OP4)尾水管内0.2f_n压力脉动基本消除，14f_n压力脉动幅值降幅为31%。...

Influences of runner optimization on the stability performance of hydraulic turbine in the low-load range under the condition of multi-energy complementary

Hydropower is often required to adjust the load in the multi-energy complementary system, due to the strong volatility, intermittency, and instability of new energy power generation. Therefore, the turbine is forced to operate in a low-load area with the low efficiency and severe vibration over a long time. The operating conditions vary frequently to threaten the stability and operating life of the unit. It is necessary to optimize the overcurrent components of the turbine for the hydroelectric unit in the multi-energy complementary system. The hydraulically unstable flow can be suppressed to broaden the high-efficiency operation range of the turbine. In this study, a multi-operating optimization of the runner was implemented to consider the weight coefficient in the operation of the turbine under the condition of multi-energy complementation of wind, solar and water. The runner of turbine was obtained suitable for the multi-energy complementary condition. The unsteady numerical analysis and comparison were also carried out on the turbines before and after optimization. The research results show that: An appropriate increase in the weight coefficient of the operating conditions in the low-load area was effectively improved the cavitation performance and the efficiency of the turbine after the multi-condition optimization, particularly with the operational performance of the turbine in the high-load area. There was an increase in the inlet and outlet placement angles of the optimized runner blades, leading to effectively reduce the attack angle of the heading edge of the blade and the flow angle of the tailing edge of the blade under low-load conditions. The vortex was better restrained from the heading edge to the back of the blade. There was an increase in the flow separation area at the tailing edge of the blade, and the inflow conditions of the draft tube. The strength of the vortex band in the draft tube was significantly reduced. Under the low load conditions, the pressure pulsation in the draft tube was mainly the 0.2fn low-frequency pressure pulsation that caused by the vortex, and the low-amplitude pressure pulsation with the blade passing frequency at the inlet of the draft tube that caused by the rotation of the runner. The pressure pulsation in the runner was mainly the 0.8fn pressure pulsation that caused by the flow separation area at the tailing edge of the blade, while the 24fn high-frequency pressure pulsation was caused by the dynamic and static interference between the guide vane and the runner near the band. The 0.2fn low-frequency pressure pulsation was passed up from the draft tube. The pressure pulsation amplitudes of different frequencies in the runner and the draft tube were effectively reduced after optimization of the runner blade, indicating the particularly outstanding improvement of pressure pulsation in the draft tube. The amplitudes of pressure pulsation were reduced by 45% and 40%, respectively, in the draft tube with the frequency of 0.2 and 14fn under the low load condition (OP1). There was no pressure pulsation with the frequency of 0.2fn in the draft tube under rated condition (OP4). The amplitude of pressure pulsation of 14fn was reduced by 31%. The operation stability of the turbine was better improved in the low load area. The finding can provide a strong reference to optimize the operation of the turbine runner in the multi-energy complementary system.