Fluid Excitation And Self-healing To Suppress Vibration Under Transient Flow Conditions Of Cogeneration Turbines

Large cogeneration turbine units have become a major development trend in solving the contradiction between supply and demand of urban central heating and improving the energy conversion heat efficiency due to their outstanding advantages such as high energy efficiency and low harmful gas emissions.Weak research foundations such as fluid excitation under transient flow conditions and its unique vibration-induced destabilization mechanism have become the main barrier to large-scale application of cogeneration units in China.By studying the fluid excitation induced by transient inlet disturbance and its solution method,this paper establishes a unified rotor system dynamics model describing the nonlinearity between the geometric nonlinearity of flexible blades and the excitation-dependent nonlinearity of periband friction damping,elucidates the fluid-induced vibration mechanism,establishes the self-healing vibration suppression technology based on periband damping,and provides the theoretical basis for establishing the optimized design method of turbine rotor inlet parameters and the high-efficiency stabilization and vibration damping technology.In order to investigate the fluid excitation mechanism under transient flow conditions,the fluid excitation model for transient flow conditions and its numerical calculation method are established.Fluid excitation model includes transient distribution pressure model and spatio-temporal discretization model on the blade surface,first of all,based on the continuity equation,Taylor's formula,to establish transient fluid excitation in the blade surface under transient flow conditions,and the use of spatio-temporal discretization method,to establish transient flow conditions fluid excitation spatio-temporal discretization model,the transient distribution excitation discretization for the transient uniform and steady-state distribution of the two parts,unified in the model,in order to simultaneously solve the fluid excitation"time distribution" and "spatial distribution" problem.The transient distributed pressure at the blade surface is obtained by establishing a method for solving the fluid excitation for transient flow conditions,solving the steady-state non-uniform excitation using inverse distance weighted interpolation,and solving the transient uniform excitation using the fast Fourier transform to obtain the fluid excitation for transient flow conditions.Based on the solution method of fluid excitation under transient flow conditions,the flow field simulation is carried out to obtain the flow line distribution,transient pressure distribution and pulsation in the calculation domain of the final luffing flow field and different lobe heights under different pumping conditions,to reveal the unsteady flow characteristics in the final luffing flow field affected by different inlet volume variation rate ?G and the mechanism of fluid excitation,and to discuss the influence of inlet velocity variation rate ?v and inlet angle variation rate ?? on the amplitude-frequency characteristics of fluid excitation.A rotor system dynamics model with biflex structural nonlinearity,shroud damping nonlinearity,and fluid excitation under transient flow conditions is developed and solved,and the model is simplified and dimensionally reduced by relative dynamic flexibility method using CN group theory to analyze the effects of biflex structural nonlinearity and periband damping nonlinearity on the inherent characteristics of the rotor system,and to study the vibration characteristics of the rotor system under fluid excitation with different inlet volume variation rate ?G.Based on the vibration suppression mechanism of shroud damping,a prediction method of rotor system stability suitable for transient flow conditions is established,with the objective of shortening the pumping time as much as possible without exceeding the amplitude and destabilizing the unit,and a self-healing vibration suppression method of rotor system based on periband damping is established.