Study On Internal Flow And Runner Response Of Ultra-high Head Pump-turbine

With the increasing development of electronic science and its related industries,people’s demand for power supply is getting higher and higher.Traditional thermal power generation technology is more polluting to the environment and cannot form a sustainable power supply,so hydroelectric power generation as a new generation of sustainable power generation technology has been vigorously developed by the state.As the core component of hydroelectric power generation,the pump turbine is related to the energy conversion of the whole power generation process.The energy conversion inside the ultra-high-head turbine is more intense than that of the conventional high-head turbine,and this energy conversion poses a greater challenge to its internal stability and structural strength.In this paper,we take an ultra-high head pump turbine as the research object and conduct a study on its internal flow,fluid vibration excitation,structural stress and modal characteristics under conventional operating conditions by means of numerical simulation,and the main contents and conclusions are as follows:The dynamic structural response of the runner is simulated using two way fluid-structure interaction.In order to understand the pressure pulsation,structural response and structural stress variation,a series of measurement points were set at key locations in the fluid region and the structural region of the runner to monitor the periodic pulsation and response.The results show that the main frequencies of pressure pulsation in the fluid region are mostly related to the rotating frequency of the runner,with the most intense pressure pulsation in the bladeless area of the guide vane and the most complex composition of external pressure pulsation in the area of the runner.From the frequency domain data,the presence of the coupling effect produces a significant enhancement of the 21f_n in the pressure pulsation at the measurement point in the runner region,and suppresses the low amplitude frequencies near this frequency.In terms of structural stress,there will be obvious stress concentration at the junction of the rotor blade and the upper and lower junction of the import and export nodes,with the most serious stress concentration at the junction of the blade and the upper crown at the exit position of the rotor.The results of the study on the influence of the structural modal characteristics on the inherent frequency of the structure show that:the inherent frequency of the runner will increase significantly when the size of the structure decreases,and the pre-stress and stiffening of the structure will have a small enhancement effect on the frequency of the runner,but the effect is not obvious and can be ignored under normal circumstances.The effect of the additional mass force of the fluid will have different degrees of weakening effect on the rotor frequency,causing the risk of resonance.For the structure itself,the rotor blade shape plays a decisive role in the inherent frequency and has a significant effect on the added mass factor.