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With the rapid development of large‐capacity hydraulic turbines and pumped‐storage power stations, hydraulic vibration analysis attracts increasing attention nowadays. To explore the influence of torque and speed variation on hydraulic vibration characteristics during transient processes and ensure the stability of hydropower stations, an improved analytical formula of turbine impedance involving the torque and speed variation was then derived. The free vibration analysis and forced vibration analysis using the transfer matrix method and the hydraulic impedance method were carried out. According to the numerical simulations, the obtained attenuation factors show differences in magnitude which illustrates that the torque variation and speed variation in transients do affect the damping rate of the vibration. In addition, the results indicated the natural angular frequencies of hydropower system were mainly dependent on the length of water conveyance system and pipe characteristics. It can be inferred form vibration mode shapes that for some specific frequencies, the magnitude of oscillatory pressure head and flow rate along the downstream tail tunnel are influenced by the hydraulic turbine. The correlation between the turbine impedance and guide vane openings tells that the hydraulic impedance is getting smaller as the opening increases. What's more, the corresponding free vibration analysis shows that the absolute value of the damping rate is closely related to the value of the flow rate. [ABSTRACT FROM AUTHOR]

The hydraulic turbine in turbine mode (TMHT) has significant advantages in residual energy recovery, but rapid optimization of its runner parameters has always been a challenge. To address this issue, the optimization algorithm ISMA‐BPNN is proposed based on the improved slime mold algorithm (ISMA) and back propagation neural network (BPNN). First, an efficiency characteristic neural network (ECNN) and a water head characteristic neural network (HCNN), which take the geometric parameters of the runner as input, and the efficiency and water head as outputs, respectively, are constructed by combining the orthogonal test‐based sample data, computational fluid dynamics (CFD), and BPNN. Then, the slime mold algorithm is improved and the optimal runner geometric parameters are obtained based on the ISMA, ECNN, and HCNN, to achieve rapid optimization of the TMHT runner. Finally, the CFD‐based numerical calculation accuracy is verified through real machine tests, and the feasibility of the ISMA‐BPNN‐based rapid optimization strategy for TMHT performance is further verified through CFD numerical simulation. [ABSTRACT FROM AUTHOR]

Objective: Study the effects of downstream passage through a novel turbine designed for fish safety, the Restoration Hydro Turbine (RHT), on American Eels Anguilla rostrata in a recirculating turbine test facility. Methods: A 55‐cm‐diameter RHT was operated under 10 m of hydraulic head and 667 revolutions/min. In total, 131 eels were passed through the turbine and 43 eels were used as experimental controls (length = 33.9–65.5 cm). High‐speed video of passage through the runner region was captured for 89% of turbine‐passed eels, and injury and behavioral effects were recorded immediately before and after passage, as well as after a 48‐h holding period. A subset of 37 eels was additionally examined with X‐ray imaging for internal injuries. Result: The 48‐h survival rate for both treatment and control groups was 100%, with no major internal or external injuries present after the holding period. Conclusion: This is a substantial improvement over eel survival rates through conventional Kaplan and Francis turbines, which may range from 40% to 95%, and suggests that hydropower turbines designed for safe downstream fish passage could be implemented without major impacts to eels. [ABSTRACT FROM AUTHOR]

Compared with the traditional reverse multistage pump as hydraulic turbine, hydraulic turbine in turbine mode (T‐type turbine) with low specific speed has higher single‐stage energy head, which can effectively reduce stages and increase the stability when it is used to recycle high residual pressure liquid. Blade number of runner is an important design parameter, which has great influence on the performance of T‐type hydraulic turbine and need to be further studied. Therefore, two‐stage T‐type turbine models with different blade numbers are established through numerical simulation. Then, the accuracy of numerical simulation is verified by test. Finally, the performance and pressure fluctuating characteristics of turbine with different blade numbers are obtained. The results show that: (a) Taking same blade numbers in both stages (traditional design method), the turbine efficiency can be higher with the blade number of primary runner and secondary runner are 14, but resulting the superposition of pulsation in secondary runner; (b) Taking different blade numbers in both stages, respectively, the superposition of pulsation can be effectively avoided, which also leads to the increase in efficiency, and up to 81.169%; (c) The method of using different number of blades in different stages can replace the traditional design method and effectively improve the hydraulic performance of T‐type hydraulic turbine. [ABSTRACT FROM AUTHOR]

Linear elastic fracture mechanics (LEFM) approaches are seldom used to analyze fatigue problems in hydraulic turbomachinery, where extremely simplified fatigue models are normally considered. In one of the largest Kaplan hydraulic turbines in the world, the piston rod, which is an important load transfer component, was found broken twice at the same location. This event, which leads to extremely high direct reparation costs and indirect costs, is a very useful case for research of fatigue problems in hydraulic turbines by means of LEFM. For this purpose, the crack growth progress in the piston rod is simulated with numerical LEFM techniques. A probabilistic model for the initial flaw size is considered. A reliability criterion, consisting in the probability of not having a critical crack or a fracture in the piston rod after a specific service time, is defined. Based on this model, the influence of initial crack models and operating services of the machine on the reliability of the unit is discussed. The calculated crack path and predicted number of loading cycles as a function of the initial crack size agree with the actual fracture section and operating time to fracture. [ABSTRACT FROM AUTHOR]

The design of a novel submerged hydraulic turbine for producing electricity by converting the available hydropower on canal locks during raising and lowering ships, but with the minimum overall impact on the facility, is being considered. The hydraulic head in such applications is low (few metres) and varies over time (from its maximum value down to zero) resulting in a low potential conversion of hydraulic head in electrical energy. The study involves the modification of the hydraulic transient system, the design and performance estimation of a hydraulic turbine. Based on the performance curves, a permanent magnet Vernier generator is designed. The models of the hydraulic turbine and generator are added to the system model and simulation results of the whole system are presented. [ABSTRACT FROM AUTHOR]

This study describes a new method for determining combined synchronous generator and water turbine bearings losses as well as stray‐load losses of a generator, based on measurement of the speed change during electrical braking. In the electrical braking regime, the total braking torque of a hydrogenerator is made up of the torques defined by losses in the runner chamber of the hydraulic turbine, ventilation losses in the hydraulic‐turbine generator, bearings losses in the generator and the water turbine, as well as electromagnetic and stray‐load losses in the short‐circuit. In this study, the torque–speed curve is represented by the corresponding equations which describe all the torques occurring during electrical braking. By applying these equations to the measured results and using some numerical calculations, combined generator and water turbine bearings losses as well as stray‐load losses can be obtained. The proposed method is applied on a 190 MW generator at the Hydro Power Plant (HPP) Djerdap (in Serbia). The obtained results demonstrated a very high level of accuracy when compared with the values found in the manufacturer's technical documentation (Electrosila). The proposed method has the best and most economical use in large synchronous generators and generators in older power plants. [ABSTRACT FROM AUTHOR]

SUMMARY On the basis of the Helmholtz decomposition, a grid-free numerical scheme is provided for the solution of unsteady flow in hydraulic turbines. The Lagrangian vortex method is utilized to evaluate the convection and stretch of the vorticity, and the BEM is used to solve the Neumann problem to define the potential flow. The no-slip boundary condition is satisfied by generating vortex sticks at the solid surface. A semi-analytical regularization technique is applied to evaluate the singular boundary surface integrals of the potential velocity and its gradients accurately. The fast multipole method was extended to evaluate the velocity and velocity gradients induced by the discretized vortex blobs in the Lagrangian vortex method. The successful simulation for the unsteady flow through a hydraulic turbine's runner has manifested the effectiveness of the proposed method. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]