Dynamic Analysis Of Coupled Multi-physics Of Bulb Tubular Turbine

With the rapid development of hydropower cause,bulb hydraulic turbine is used more widely in the development and utilization of hydropower,and is changed to the high-capacity,high specific speed,high efficiency direction.With large bulb turbine is put into operation,vibration problems have appeared to the turbine,such as Rub-Impact Fault between Rotor and Stator,runner blade crack and fracture,and some of which even lead to resonance between the plant and the adjacent hydraulic structures,seriously threatening the production of the plant.The Instability of bulb hydraulic turbine unit has become a prominent issue in the presence of unit operation,but also is the hot issues and difficult problem of today's research.In this paper,dynamics of bulb hydraulic turbine was the main research subject;with analysis method combing with nonlinear,unsteady and multi-physics coupling algorithms,the vibration characteristics of turbine shaft System Electromagnetic-rubbing coupling,the flow characteristics of the multidimensional fluid-solid coupling flow field of turbine transitionprocess and the dynamic characteristics of turbine fluid-solid coupling structure have been studied comprehensively;all above are significant in theory and practice to understanding the inherent mechanism of bulb turbine,improve the overall hydraulic performances of the bulb hydraulic turbine,and enhance the operation reliability and the life of the turbine unit.This paper mainly carried out studies as follows:(1)For the rub-impact fault between the rotor and the stator of bulb hydraulic turbine,by using the rotor dynamics theory and the modern nonlinear dynamics theory,established the electromagnetic-rubbing coupling mathematical model of the double-span dual-rotor system of the bulb hydraulic turbine to analyze the vibration response characteristics of the rubbing coupling system,with considering the mechanical unbalanced force of shafting,the nonlinear magnetic pull,the hydraulic unbalanced force and the nonlinear rubbing coupling effect.(2)By using the incremental form of Newmark-? method and the numerical algorithm of Newton-Raphson iteration,which verified the correctness of the mathematical modal,studied the dynamic response characteristics of the electromagnetic-rubbing coupling system of the bulb hydraulic turbine under conditions with different parameters of rotation speed,stators radial stiffness and rubbing friction coefficient,etc.;analyzed the complex nonlinear dynamic behavior of the shafting,and then got the vibration rubbing coupling response law of the double-span Dual-rotor system of the bulb hydraulic turbine,the results of which provides the guiding significance for improving the structural design of the turbine shafting.(3)Based on the bulb turbine group of a hydropower station in Liaoning Huanren,built a frame vibration response test system and established the finite element model;for the load shedding transition process of the bulb turbine with the output reduction from 100%to 75%,collected the y direction original vibration signals of the frame in the Field experiment and then processed and analyzed them;comparing with the simulation results,analyzed the frequency domain components of the frame with the results of which,verified the accuracy of adopting the fluid-solid coupling theory to analyze the turbine vibration,and thus prove the correctness and validity of dynamic analysis of the bulb turbine with different rotor diameters by applying this theory.Field test provides experimental supports to the coupled vibration characteristics analysis of the multi-physical fields and the transient dynamics analysis of the bulb turbine based on fluid-solid coupling and well verifies the theoretical results.(4)The semi-implicit method for solving pressure coupled equations in the calculation of the flow field,and the dynamic mesh were adopted to carry out the numerical simulation of the three-dimensional dynamic turbulent flow of whole ports in the start transition process and the runaway transition process of the bulb hydraulic turbine.The transient process of the pressure field and the flow characteristics of the flow field in the passages of the guide vanes and the runner were numerically simulated,which shows the state of the flow after through the turbine guide vanes and the effect of guide vane opening on the runner blade inflow.(5)Studied the inherent characteristics and the vibration response of the turbine under two conditions of empty passage and water filled passage and established the acoustics-fluid-solid multi-physic coupling dynamic model;compared the influence coefficients of the finite element simulation results with the results from the existing methods by using the wet-mode algorithm of asymmetric coupling,which shows that the vibration characteristics analysis based on the wet mode is possible to make up the inaccuracy of traditional method.As the particularity of the geographic environment set the Bulb hydraulic Turbine,the harmonic response of the turbine and the vibration response of the seismic spectrum were studied with the sequential coupling,based on wet-modal analysis,which provides a theoretical basis for the seismic stability of the turbine design.(6)For the fatigue and crack problems of the bulb hydraulic turbine key components,based on the fluid-solid coupling theory,studied the nonlinear coupling of the turbine with considering the unsteady numerical stimulation of the whole ports of the bulb hydraulic and the coupling of the transient dynamics equations of the whole unit;and analyzed the dynamic stress characteristics of the key components under typical working conditions to get the variation of the pressure pulsation of the key components and the dynamic variation of the maximum equivalent stress and the deformation,which provides the basis for the safe production of the turbine unit.For the operation stability,the paper studied the dynamic characteristics of the bulb hydraulic turbine in-depth,providing a theoretical method for optimal design and a scientific basis for solving dynamic problem of the bulb hydraulic turbine.