Performance Prediction And Structure Optimization Of Hydraulic Turbines Based On Internal Flow Field

Under the existing manufacturing enterprises with high energy consumption of petroleum,chemical,seawater desalination and so on, generally there are many process phenomenon of turning the high-pressure fluid to a certain desired low-pressure vacuum through the valve or direct discharger. In the process of decompression and emissions, a large number of fluid pressure energy change into the heat energy and then disappeared in the environment, resulting this part of energy waste directly. If we can use the water turbine to recycle this part of energy, and the excess energy can be used for reproduction,so in the long-term process of production, the benefits is very considerable for the enterprises.Therefore, this paper refer to the low specific speed Francis turbine blade design principle and double-suction pump structure, then design a horizontal double-channel hydraulic turbine Francis. In the process of the study, in order to optimize its structure, ensure its performance and maximum efficiency of water recovery, but also to minimize its research costs, we adopt a thinking of modern hydraulic design which based on performance prediction. According to this actual situation of the subject, we made a hydraulic design and three-dimensional modeling of the whole flow passage of hydraulic turbine. Because the water-leading part have a certain impact on the structure,cost of production and hydraulic performance of the device, so we make use of different guide vane with or without guide vanes for the design program of the water-leading part. Oberviously, when no water-leading part the hydraulic turbine's structure is more compact, relatively low production costs, the relative hydraulic losses of the water-leading part is small. However, which program's the hydraulic performance is better is unknown. So we make the use of Computational Fluid Dynamics (short title CFD) analysis software, make a numerical simulation of the complex turbulent flow field of the hydraulic turbine's full flow passage, predict the performance and then optimize the structure based on the numerical simulation to replace the traditional model test. Through numerical simulation, specifically discussed the flow field in any program which velocity,pressure,streamline and circulation distribution,hydraulic losses and so on, compare simulation results from the overall conversion performance of energy, adaptability of changing condition and reasonable of flow field distribution, which optimize the structure of hydraulic turbine. Through a qualitative and quantitative comparative analysis about the numerical simulation results of several programs on the whole flow passage, obtain the conclusions as follows:(1) We can see through the comparison of the runner blade inlet circulation, although the spiral case of water turbine is the key component of formating circulation, it is difficult to achieve water supply or tangential velocity distribution uniform along the circumference of the runner blade inlet only through the spiral case, we must also use the guide vane to complement and amend circulation;(2) Through the comparative analysis, in the hydraulic turbine installations of adding with the guide vanes, the pressure,speed,streamlines distribution of flow passage which in the back of the water-leading part than those hydraulic turbine installations without guide vanes are more reasonable, and conducive to the high efficiency of energy conversion;(3) The results show that, it is not good for water flow to use the conventional vane with thick head, and in the vane head with energy loss seriously, thus using the vane of head modifying and airfoil thinning to study the hydraulic performance of hydraulic turbine, can reduce the guide vane flow speed of the head on the back and decrease the hydraulic loss of flow components;(4) At the optimal,high and low flow rate conditions, through numerical simulation of the hydraulic turbine's various vane airfoil, and through the comparative analysis, the hydraulic turbine with the negative curvature guide vane which its head drawn repairing with optimal efficiency and the hydraulic performance is better than other programs at low flow rate conditions, which shows that the guide vane with a wide conditions range of applications, select the hydraulic turbine guide vane for the requirement of the design, provides a useful reference value for the future structure optimization and performance prediction of hydraulic turbine.This paper based on the modern hydraulic design method of the performance prediction, used the design program of adding negative curvature guide vane during the study design, shorten the product design cycle and cost, and improved the efficiency of energy recovery.