Instability of pump turbine with S-shaped curve is characterized by large fluctuations of rotational speed during the transient processes.For investigating this phenomenon,a numerical model based on the dynamic slidin...Instability of pump turbine with S-shaped curve is characterized by large fluctuations of rotational speed during the transient processes.For investigating this phenomenon,a numerical model based on the dynamic sliding mesh method(DSSM)is presented and used to numerically solve the 3D transient flow which is characterized by the variable rotation speed of runner.The method is validated by comparison with measured data for a load rejection process in a prototype pump turbine.The results show that the calculated rotation speed agrees well with the experimental data.Based on the validated model,simulations were performed for the runaway process using an artificially assumed operating condition under which the unstable rotation speed is expected to appear.The results confirm that the instability of runner rotational speed can be effectively captured with the proposed method.Presented results include the time history profiles of unit flow rate and unit rotating speed.The internal flow characteristics in a typical unstable period are discussed in detail and the mechanism of the unstable hydraulic phenomenon is explained.Overall,the results suggest that the method presented here can be a viable alternative to predict the dynamic characteristics of pump turbines during transient processes.展开更多
The performance of a reversible pump turbine with S-shaped characteristics is of great importance to the transition processes such as start-up and load rejection. In order to predict the S-shaped curve accurately and ...The performance of a reversible pump turbine with S-shaped characteristics is of great importance to the transition processes such as start-up and load rejection. In order to predict the S-shaped curve accurately and develop a reliable tool for design improvement, a shear stress transport model (SST) with various numerical schemes for pressure term in the governing equation was investigated in a whole pump turbine including spiral casing, stay vanes, guide vanes, runner and draft tube. Through the computation, it was shown that different zones in the curve should employ different schemes to get the solution converged. Comparison of discharge-speed performance showed that good correspondence is got between experimental data and CFD results. Based on this, internal flow analysis was carried out at three typical operating points representing turbine mode, shut-off mode and reversible pump mode, respectively. According to the flow field concerned, the mechanism for the speed-no-load instability was explained, which provides good guidelines to take countermeasures in future design.展开更多
基金supported by the National Basic Research Program of China(Grant No.2009CB724302)the National Natural Science Foundation of China(Grant No.51176168)
文摘Instability of pump turbine with S-shaped curve is characterized by large fluctuations of rotational speed during the transient processes.For investigating this phenomenon,a numerical model based on the dynamic sliding mesh method(DSSM)is presented and used to numerically solve the 3D transient flow which is characterized by the variable rotation speed of runner.The method is validated by comparison with measured data for a load rejection process in a prototype pump turbine.The results show that the calculated rotation speed agrees well with the experimental data.Based on the validated model,simulations were performed for the runaway process using an artificially assumed operating condition under which the unstable rotation speed is expected to appear.The results confirm that the instability of runner rotational speed can be effectively captured with the proposed method.Presented results include the time history profiles of unit flow rate and unit rotating speed.The internal flow characteristics in a typical unstable period are discussed in detail and the mechanism of the unstable hydraulic phenomenon is explained.Overall,the results suggest that the method presented here can be a viable alternative to predict the dynamic characteristics of pump turbines during transient processes.
基金supported by the National Natural Science Foundation of China (Grant No. 50979095)
文摘The performance of a reversible pump turbine with S-shaped characteristics is of great importance to the transition processes such as start-up and load rejection. In order to predict the S-shaped curve accurately and develop a reliable tool for design improvement, a shear stress transport model (SST) with various numerical schemes for pressure term in the governing equation was investigated in a whole pump turbine including spiral casing, stay vanes, guide vanes, runner and draft tube. Through the computation, it was shown that different zones in the curve should employ different schemes to get the solution converged. Comparison of discharge-speed performance showed that good correspondence is got between experimental data and CFD results. Based on this, internal flow analysis was carried out at three typical operating points representing turbine mode, shut-off mode and reversible pump mode, respectively. According to the flow field concerned, the mechanism for the speed-no-load instability was explained, which provides good guidelines to take countermeasures in future design.
