Investigation Of Internal Flow Of A Cross-Flow Turbine And Runner Optimization Design

Hydropower resources in China has huge potential. Cross flow turbines are widely used in small hydropower plants due to its resource allocation, small ecological burden, simple technology, low investment characteristics. The cross flow turbine is widely used in small hydropower which is simple structure design, easy production, low cost, easy maintenance,good cavitation performance and wide flow of use. The cross flow turbine structure has a great influence on the performance of the turbine. The domestic and overseas scholar researchers have made some progress in the study of the shape, parameters and the influence on the performance of the cross flow turbine. In this paper, a cross flow turbine is used as the research object. The three-dimensional flow and energy distribution of the turbine are calculated by ANSYS CFX simulation software. The hydraulic turbine is modified under the design condition and the optimal method is used to optimize the blade. The three-dimensional unsteady coupling numerical calculation of the optimized model is carried out. The main work of this paper is divided into the following aspects:First of all, build the full channel model and mesh for the cross flow turbine and illustrate the grid independence. The numerical simulation was carried out to study the runner design.Based on steady numerical simulation, the runner of the cross flow turbine is remodeled by changing the blade number, the diameter ratio, blade setting angle and carry out a CFD whole channel numerical calculation. The results show that when the runner has 22 blades and diameter ratio is 0.70 and the angle increases, the efficiency and output of the blade are improved obviously. The flow field of the runner is improved, the energy loss is reduced and gas-liquid mixed more fully.Secondly, in order to study the comprehensively influence of the three parameters on the internal flow characteristics of the cross flow turbine, the radial basis function(RBF) neural network model is used to optimize the blade parameters. The results show that the overall performance of the optimization designed runner is improved to some extent, and the flow field of the runner is improved and the efficiency is obviously improved.Thirdly, the unsteady numerical simulation of the whole flow channel of the optimized runner is carried out. The pressure fluctuation characteristics of the optimized turbine are studied under unsteady conditions. The results show that the two kinds of optimization schemes have low frequency pressure fluctuation of 7.58Hz at the inlet and outlet of the runner. The eddy current intensity of the optirmized design scheme is more obvious which the core area is reduced, and the hydraulic stability is improved.