CN-115688299-B - Assessment method for water erosion state of final-stage movable blade of steam turbine

CN115688299BCN 115688299 BCN115688299 BCN 115688299BCN-115688299-B

Abstract

The invention discloses an assessment method of a water erosion state of a final-stage movable blade of a steam turbine, which comprises the following steps of obtaining a flow channel geometric model of the final-stage movable blade of the steam turbine and fluid thermodynamic parameters in a flow channel of the final-stage movable blade of the steam turbine under all operating conditions, obtaining a blade geometric model of the final-stage movable blade of the steam turbine and a blade geometric model of a final-stage stationary blade of the steam turbine, introducing a fluid mechanics control equation, a momentum equation, a solid mechanics control equation and a fluid-solid coupling definition equation aiming at the flow channel geometric model and the blade geometric model, introducing boundary conditions and hypothesis conditions, carrying out grid division on the flow channel geometric model and the blade geometric model, calculating flow field thermodynamic parameter distribution by adopting a large vortex simulation method, then adopting a fluid-solid coupling calculation method, transferring the result of the flow field thermodynamic parameter distribution to the blade to carry out further calculation, carrying out numerical simulation to obtain stress distribution and deformation conditions of the final-stage movable blade, and carrying out water erosion degree calculation to obtain the water erosion state of the final-stage movable blade.

Inventors

YANG LUKUAN
ZUO DUNGUI
TANG MINJIN
XIA XIANXI
GUAN BINGXIN
FAN NIANQING
JIN XIAO
ZHU BAOYIN
LI SHANGYU
LAI YUNTING

Assignees

苏州热工研究院有限公司
中国广核集团有限公司
中国广核电力股份有限公司

Dates

Publication Date: 20260512
Application Date: 20220905

Claims (6)

1. The method for evaluating the water erosion state of the last-stage movable blade of the steam turbine is characterized by comprising the following steps of: Obtaining a geometric model of a runner of a final-stage movable blade of the steam turbine and fluid thermodynamic parameters in the runner of the final-stage movable blade under the full operating condition; Acquiring a blade geometric model of a final-stage movable blade of the steam turbine and a blade geometric model of a final-stage stationary blade of the steam turbine; Introducing a hydrodynamic control equation, a momentum equation, a solid mechanical control equation and a fluid-solid coupling definition equation aiming at the flow channel geometric model and the blade geometric model, and introducing boundary conditions and hypothesis conditions; grid division is carried out on the runner geometric model and the blade geometric model; firstly, calculating the distribution of the thermal parameters of the flow field by adopting a large vortex simulation method, then, transferring the result of the distribution of the thermal parameters of the flow field to a blade by adopting a fluid-solid coupling calculation method for further calculation, and carrying out numerical simulation to obtain the stress distribution and deformation condition of the final-stage movable blade; introducing a water erosion analysis module to calculate the water erosion degree so as to obtain the water erosion state of the last-stage movable blade of the steam turbine; Matching and correlating the operation condition of the steam turbine with the calculated water erosion degree, monitoring the thermal parameters of the steam turbine in real time in the operation process, and matching the corresponding water erosion degree to realize the prediction of the water erosion state of the last-stage movable blade of the steam turbine; The assumption condition is that the final stage blade is a rigid body, no relative axial displacement and deformation exist in the rotation process, the bidirectional coupling effect of the solid boundary forming the flow channel and the fluid is ignored, and the temperature change of steam in the flow channel is ignored; Setting the tail end face of the stator blade as an inlet, setting the front end face of the next-stage stator blade as an outlet, and selecting and interpolating inlet pressure, inlet temperature, outlet pressure and outlet temperature according to the fluid thermodynamic parameters in the final-stage movable blade flow channel under the full operating condition; The boundary conditions comprise boundary conditions of dynamic calculation of the moving blade, wherein the pressure of steam acting on the surface of the moving blade and the temperature of the steam at the juncture of the moving blade are set as boundary conditions of the moving blade surface, and influence of deformation of the moving blade on fluid and heat distribution is ignored; The calculating process of the water erosion degree adopts a nominal stress method, calculates the water erosion effect according to a linear accumulated damage theory, and comprehensively considers load conditions, average stress of the blade and fatigue strength coefficients; In the fluid-solid coupling calculation process, ansys software is adopted to complete fluid-solid coupling analysis, after flow field calculation is completed, the pressure distribution result on the surface of the blade is extracted and used for a contact interface of the fluid and the solid structure, namely a working face and a non-working face of the blade model under static structure analysis, centrifugal force is applied, and a cloud picture of blade strength and stress distribution is obtained under the combined action of multiple loads.
2. The evaluation method according to claim 1, wherein in the mesh division, a mesh repairing method is employed for meshes having a mass number of less than 0.3 to improve the quality of the mesh, and mesh inspection is performed after mesh repairing.
3. The evaluation method according to claim 1, wherein the hydrodynamic control equation is represented by the formula: ; In the formula, Indicating the density of the fluid and, The time is represented by the time period of the day, Indicating that in the direction of the x-axis, Indicating that in the direction of the y-axis, Indicating that in the direction of the z-axis, Representing the velocity component of the fluid along the x-axis, Representing the velocity component of the fluid in the y-axis direction, Representing the velocity component of the fluid along the z-axis.
4. The method of evaluation according to claim 1, wherein the momentum equation is represented by the formula: ; In the formula, The kinematic viscosity is indicated as such, Indicating the density of the fluid and, Is representative of the mass and force of the fluid, The pressure of the fluid is indicated and, Indicating the gradient of the pressure of the fluid, The time is represented by the time period of the day, Representing a fluid velocity field.
5. The evaluation method according to claim 1, wherein the solid mechanical control equation is represented by the following formula: ; In the formula, Representing the stress state at any one point in the solid, Representing the volumetric force of the solid.
6. The method of evaluating according to claim 1, wherein the fluid-solid coupling definition equation is represented by the formula: ; where the subscript f denotes a fluid, the subscript s denotes a solid, Representing the stress of the steel sheet, the stress, Indicating the direction.

Description

Assessment method for water erosion state of final-stage movable blade of steam turbine Technical Field The invention particularly relates to a method for evaluating the water erosion state of a final stage movable blade of a steam turbine based on large vortex simulation and FSI (fluid solid interaction, fluid-solid coupling). Background The steam turbine is an important device for thermal power and nuclear power, and the stability of the steam turbine is important for the electric safety of China. In order to reduce the cost of power generation operation and maintenance and realize high stability of the steam turbine, it is highly desirable to establish a comprehensive and systematic steam turbine life assessment and prediction technique. The final-stage movable blades serve as key components of the steam turbine, and are critical to operation safety. Factors that affect blade life have a high degree of nonlinearity, including size, materials, processing, operating conditions, and the like. The working condition of the steam turbine is changeable, the final stage bucket geometry and flow path are complex. Therefore, it is difficult to build a life prediction model concerning the effect of the last stage bucket erosion. These factors lead to lack of accuracy and systematicness in the prediction of erosion of the last stage bucket. In recent years, computational fluid dynamics and computational solid mechanics have been widely used in research of the usage characteristics of steam turbines and related materials. Based on three-dimensional flow theory, accumulation of advanced experimental data and gradual improvement of professional software, the numerical simulation of the final-stage movable blade can analyze and predict the water erosion characteristic more accurately, compared with pilot test, the numerical simulation test saves economic cost, and the numerical simulation can simulate the characteristics under various working conditions, so that more comprehensive data is provided for acquiring the water erosion characteristic under a large-scale working condition. Traditional final stage bucket erosion prediction techniques rely primarily on periodic maintenance and turbine monitoring systems. The method can realize the final-stage movable blade water erosion prediction to a certain extent, but has obvious defects such as incapability of analyzing the service life in real time, excessive dependence on maintenance plans, limited application range and the like. Disclosure of Invention In view of the above, the present invention aims to provide a method for evaluating the water erosion state of the last stage bucket of a steam turbine. In order to achieve the above purpose, the present invention adopts the following technical scheme: A method for evaluating the water erosion state of a final stage movable blade of a steam turbine comprises the following steps: Obtaining a geometric model of a runner of a final-stage movable blade of the steam turbine and fluid thermodynamic parameters including temperature, pressure, speed and steam parameters under a design working condition in the runner of the final-stage movable blade under a full working condition; Acquiring a blade geometric model of a final-stage movable blade of the steam turbine and a blade geometric model of a final-stage stationary blade of the steam turbine; Introducing a hydrodynamic control equation, a momentum equation, a solid mechanical control equation and a fluid-solid coupling definition equation aiming at the flow channel geometric model and the blade geometric model, and introducing boundary conditions and hypothesis conditions; grid division is carried out on the runner geometric model and the blade geometric model; Firstly, calculating the distribution of flow field thermal parameters (flow field temperature and pressure distribution), in particular the temperature and pressure distribution at the juncture of a flow field and a moving blade by adopting a large vortex simulation method, then adopting a fluid-solid coupling calculation equation, transferring the result of the distribution of flow field thermal parameters to the blade for further calculation, and carrying out numerical simulation to obtain the stress distribution and deformation condition of the final moving blade; introducing a water erosion analysis module to calculate the water erosion degree, and obtaining the water erosion state of the final-stage movable blade of the steam turbine. According to some preferred embodiments of the invention, when calculating the blade stress by adopting a fluid-solid coupling calculation method, calculating is completed by adopting ANSYS software, an ICEM module is used in a grid blade model, material characteristic parameters are imported into the ANSYS software, the pressure distribution of a flow field is transferred to a blade structure analysis through the fluid-solid coupling module in the ANSYS software, and numerical simula