Research On Zero Output Technology Of Low Pressure Cylinder Of Heating Unit In Thermal Power Plant

Taking a 350 MW steam turbine generator set of a domestic thermal power plant as the research object,some problems that may be encountered in the zero-output heating reform of the low-pressure cylinder are discussed.The numerical simulation method is used to analyze the minimum quality of the final stage of the steam turbine after the transformation.The flow field characteristics under flow and normal conditions,and the modal analysis of the single blade at the end of the low-pressure cylinder of this type of unit,predicted some resonance problems that may occur during operation.In this paper,the flow field characteristics of the last stage of steam turbine under the minimum mass flow rate and normal working conditions are analyzed firstly,and the variation of the flow characteristics of the final stage with the increase of mass flow rate is recorded,and the final stage static is obtained.The pressure distribution on the surface of the moving blade and the second and third-dimensional streamline diagram of the last stage moving blade show that the flow state of the end stage of the low pressure cylinder will change greatly with the decrease of mass flow in the stage.The main performance is that the angle of attack of the steam is negative,and the flow vortex is formed on the pressure surface and the suction surface of the blade,and the phenomenon of de-flow occurs,which also causes the phenomenon of blasting and water erosion of the blade.Secondly,the static characteristics of the final stage of the low-pressure cylinder of the unit are analyzed.The single blade is physically modeled by ProE.The model is imported into the static structural module of ANSYS software,and the single blade is modeled by free meshing.State analysis,the first eight natural frequencies of the blade and the corresponding deformation cloud map are calculated.The results show that the natural frequency of the blade is greater than the operating frequency of the unit,so no resonance phenomenon occurs during the operation of the unit.Finally,the dynamic characteristics of the last stage blades of the steam turbine are analyzed.Since the units are all operated at a speed of 3000r/min,the centrifugal force is applied to the modal analysis of the last stage blades.The vibration characteristics of the last stage blade are analyzed under six speed conditions.The natural frequency of the blade and the corresponding vibration mode are extracted.The Campbell diagram of the last stage bladeis drawn.The results show that the natural frequency of the same order of the blade increases with the increase of the rotational speed.Large,in the first three orders,the frequency change is greatly affected by the low rotation speed,and the influence of high rotation speed on the frequency change is not obvious;in the last five-order modal analysis of the last stage blade,the frequency changes with the increase of the rotational speed The more intense,it can be seen that in the latter five-order modal analysis,the frequency change is greatly affected by the high speed,and the frequency rise is not obvious at low speed.