Dynamic Characteristic Analysis And Synthetical Optimization Of Francis Turbine's Runner

Stability, efficiency and cavitation are the three main characteristics of hydraulic turbine. With the developing trend of large size and large capacity, the turbine's natural frequencies are decrescent, maybe reaching the input forces' order of magnitude. So, it is becoming more and more important to analyze the stability of a turbine. The three main characteristics of hydraulic turbine are determined by the level of designing, which is relatively lower in China. The dynamic characteristic analysis and synthetical optimization of a hydraulic turbine is an important and difficult job. The main works are as follows:1 ) Taking liquid- structure interaction into account, natural frequencies and models of the runner and its blade both in the air and in the water are worked out. The effects of Centrifugal Force and hydraulic pressure on dynamic characteristics and the possibility whether the turbine is resonated on working are analyzed. The computational results are compared with that of experimentation, and can be used as a reference to design.2) A computational procedure is proposed to solve the interaction problem of elastic structure and fluid. Little simplification of fluid is carried out. The coupling algorithm solves the equations for the fluid and solid domains independently of each other. It transfers fluid forces and solid displacements and velocities across the fluid-solid interface. The algorithm continues to loop through the solid and fluid analyses until convergence is reached. Convergence in the stagger loop is based on the quantities being transferred at the fluid-solid interface. Arbitrary Lagrangian-Eulerian formulation is adopted to treat the moving interface between the fluid and the structure. The coupling algorithm isprogrammed based on ANSY5.6 with APDL. Two numerical examples are given. The results show the effectiveness of the procedure. By means of the program FSI, the dynamic stresses of the blade caused by the hydrodynarm'c pressure under varied situations are analyzed.3 ) Locale tests of a hydraulic turbine were made. Based on the tests, the problems of its acute vibration, noise and crack were settled down.4 ) Based on the dynamic analysis and hydraulic design, a synthetical optimization of the runner is carried out. It is the first time to introduce the genetic arithmetic into the synthetical optimization of the runner. A synthetical optimization program based on the runner's efficiency and dynamic characteristics is developedAll parts above have composed a full program to analyze the dynamic characteristics of a runner. Besides, every part can run independently to compute respectively the fluid-structure interaction vibration, the dynamic characteristics on transition and synthetical optimization. This program has been applied in DongFang Electrical Machinery Co., Ltd. and gained good comments.