阅读说明：本技术 一种适用于汽轮机叶片流热固耦合分析方法 (Thermal solid coupling analysis method suitable for turbine blade flow ) 是由 屈杰 高庆 朱蓬勃 谷伟伟 曾立飞 潘渤 马汀山 居文平 于 2021-08-10 设计创作，主要内容包括：本发明公开了一种适用于汽轮机叶片流热固耦合分析方法,本发明首先在所建立的模型上进行流体计算域与固体计算域间的热-流耦合计算,为了实现流体域和固体域热通量和温度的守恒传递,二者之间采用热连接面进行数据传递,流体域和固体域内同步求解并实时数据传递。接着在所建立的模型上进行流体计算域与固体计算域间的热-固耦合计算,其中热-固分析以传递并施加在固体表面的CFD压力结果作为边界条件,并读入热分析得到的节点温度作为热载荷,同时施加相应的约束条件以及转速,从而实现了模型的综合应力分析,可极大程度的提高模型计算方法的真实性及计算结果可靠性。(The invention discloses a method for analyzing the thermal solid coupling of steam turbine blade flow, which comprises the steps of firstly carrying out thermal-flow coupling calculation between a fluid calculation domain and a solid calculation domain on an established model, adopting a thermal connection surface to carry out data transmission between the fluid calculation domain and the solid calculation domain in order to realize the conservation transmission of heat flux and temperature of the fluid calculation domain and the solid calculation domain, and synchronously solving and carrying out real-time data transmission in the fluid calculation domain and the solid calculation domain. And then, carrying out thermal-solid coupling calculation between the fluid calculation domain and the solid calculation domain on the established model, wherein the thermal-solid analysis takes the CFD pressure result transmitted and applied to the solid surface as a boundary condition, reads in the node temperature obtained by the thermal analysis as a thermal load, and applies corresponding constraint conditions and rotating speed at the same time, thereby realizing comprehensive stress analysis of the model and greatly improving the authenticity of the model calculation method and the reliability of the calculation result.)

1. The method for analyzing the hot solid coupling of the flow of the turbine blade is characterized by comprising the following steps of:

s1, establishing a blade geometric model according to the flow structure of the steam turbine, and establishing a fluid and solid calculation domain according to the actual working condition;

s2, respectively carrying out grid planing on the fluid calculation domain and the solid calculation domain to generate a plurality of structured grids;

s3, determining boundary conditions of the fluid and solid calculation model;

s4, performing heat-flow coupling calculation between a fluid calculation domain and a solid calculation domain on the blade geometric model, analyzing heat transfer between the fluid domain and the solid domain, synchronously solving in the fluid domain and the solid domain, and performing real-time data transmission;

s5, solving a Navier-Stokes equation set in Reynolds by a flow solver numerical value in a fluid domain, introducing a Boussinesq turbulence model hypothesis to enable the Navier-Stokes equation set in turbulence calculation in Reynolds to be closed, and obtaining fluid calculation domain pressure, temperature and flow rate through calculation;

s6, solving a heat conduction equation only in a solid domain, establishing a temperature distribution curve between a fluid domain and the solid domain on a heat connection surface, carrying out repeated iterative solution through a heat balance equation to ensure the heat flux conservation transmission on two sides, and obtaining the node temperature through calculation;

s7, performing thermal-solid coupling calculation between a fluid calculation domain and a solid calculation domain on the blade geometric model, performing thermal-solid coupling analysis by taking the result of the fluid domain pressure transmitted and applied to the solid surface as a boundary condition, reading the node temperature obtained by the thermal-current coupling calculation analysis in S4 as a thermal load, applying corresponding constraint conditions and rotating speed, and finally performing comprehensive stress analysis on the model.

2. The method according to claim 1, wherein in step S4, the heat transfer equation is solved in the solid domain, and the discrete heat transfer equation of the control body is:

wherein omega is the volume of the unit control body,for control of normal vector on body surface, kappa is solid heat conductivity coefficient, rho is solid material density, c_PIs the specific heat.

3. The method for analyzing the hot solid coupling of the steam turbine blade flow as claimed in claim 1, wherein in the step S4, the thermal coupling surfaces between the fluid domain and the solid domain are completely unmatched thermal coupling technology, the units obtained by the FNMB decomposition algorithm are subjected to thermal coupling equation solution to obtain the independent temperature and heat flux of the coupling surfaces of each unit, and the surface temperatures of the units on the two sides are calculated to obtain the unit body temperature through weighted average.

4. The method for analyzing thermal solid coupling of turbine blade flow according to claim 3, wherein in S4, the thermal coupling equation is as follows:

wherein W is present when the cell faces are completely unconnected_i1, when the unit face portions are connected, 0 < W_i< 1, W when fully connected_i＝0。

5. The method for analyzing the flow thermosetting coupling of the turbine blade according to claim 1, wherein in S5, the flow solver is used to numerically solve the Navier-Stokes equation set for the reynolds time average, and the specific method is as follows:

wherein, the index range of i and j is 1, 2 and 3, rho is density, S is_MAs source terms of momentum equations, S_EFor the source terms of the energy equation, τ is the tensor of shear stress,in order to take the Reynolds stress term into account,in order to be a turbulent flux, the flow,a work term for stickiness.

6. The method for analyzing the thermal solid coupling of the turbine blade flow as claimed in claim 5, wherein in S4, a Boussinesq turbulence model is introduced to make the Navier-Stokes equation system of the turbulence calculation Reynolds time mean closed, and the specific method is as follows:

wherein, mu_effIs effectively adhesive.

7. The method for analyzing the thermal solid coupling of the turbine blade flow according to claim 1, wherein in S7, the stress has six components, three normal stresses and three shear stresses, and the matrix form is:

8. the method for analyzing the thermal solid coupling of the turbine blade flow according to claim 1, wherein in S7, the matrix form of the change of the stress is:

9. the method for analyzing the thermal solid coupling of the steam turbine blade flow according to claim 1, wherein in the step S7, the elastic body strain is caused by two parts of stress and temperature change:

{ε}＝{ε^th}+{ε^el}

wherein [. epsilon. ]^elIs the stress induced strain vector, { ε }^tThe temperature induced strain vector is given by the expression for the elastomer strain for each like material:

{ε^th}＝ΔT[a a a 0 0 0]^T

in the formula: a is the coefficient of linear expansion of the material, Delta T is T-T_refIs the temperature difference between the local temperature and the reference temperature.

Technical Field

The invention belongs to the field of power generation, and particularly relates to a thermal solid coupling analysis method suitable for a turbine blade flow.

Background

The continuous improvement of the turbine inlet parameters can lead to the continuous increase of the thermal load borne by the front-end blade, and when the blade runs under the high-temperature, high-pressure and high-speed environment for a long time, the material can be induced to generate thermal fatigue and high-temperature creep. During transient operation, such as start-stop, variable load, etc., thermal stresses and deformations within the high temperature components may further exacerbate and cause low cycle fatigue, which in turn affects the operational reliability and life of the blades in the high temperature region. Because the flow characteristic of the region has extremely three-dimensional characteristics and the pressure, temperature and velocity field distribution shows extremely uneven states, the flow characteristic, stress characteristic and strain condition of the turbine blade in a high-pressure and high-temperature environment are accurately analyzed, and the method has very important significance for development design and safety analysis of high-performance blades.

At present, a calculation method of flow, heat transfer and stress field coupling-free independent simulation is generally adopted for a simulation technology of a turbine blade in a high-pressure and high-temperature environment, namely, after flow calculation is performed through CFD software to obtain a pneumatic boundary condition, a result is transmitted to FEM calculation software in a one-way mode to perform subsequent calculation of a solid domain temperature field and a stress field. The simplified calculation mode causes the boundary condition of the calculation model to be inconsistent with the real model to a certain extent, and uncertain interpolation errors are generated in the simulation result.

Disclosure of Invention

The invention aims to overcome the defects and provide the thermal solid coupling analysis method suitable for the turbine blade flow, and the authenticity of the model calculation method and the reliability of the calculation result can be greatly improved.

In order to achieve the above object, the present invention comprises the steps of:

s1, establishing a blade geometric model according to the flow structure of the steam turbine, and establishing a fluid and solid calculation domain according to the actual working condition;

s2, respectively carrying out grid planing on the fluid calculation domain and the solid calculation domain to generate a plurality of structured grids;

s3, determining boundary conditions of the fluid and solid calculation model;

s4, performing heat-flow coupling calculation between a fluid calculation domain and a solid calculation domain on the blade geometric model, analyzing heat transfer between the fluid domain and the solid domain, synchronously solving in the fluid domain and the solid domain, and performing real-time data transmission;

s5, solving a Navier-Stokes equation set in Reynolds by a flow solver numerical value in a fluid domain, introducing a Boussinesq turbulence model hypothesis to enable the Navier-Stokes equation set in turbulence calculation in Reynolds to be closed, and obtaining fluid calculation domain pressure, temperature and flow rate through calculation;

s6, solving a heat conduction equation only in a solid domain, establishing a temperature distribution curve between a fluid domain and the solid domain on a heat connection surface, carrying out repeated iterative solution through a heat balance equation to ensure the heat flux conservation transmission on two sides, and obtaining the node temperature through calculation;

s7, performing thermal-solid coupling calculation between a fluid calculation domain and a solid calculation domain on the blade geometric model, performing thermal-solid coupling analysis by taking the result of the fluid domain pressure transmitted and applied to the solid surface as a boundary condition, reading the node temperature obtained by the thermal-current coupling calculation analysis in S4 as a thermal load, applying corresponding constraint conditions and rotating speed, and finally performing comprehensive stress analysis on the model.

In S4, the heat transfer equation is solved in the solid domain, and the discrete heat transfer equation for the control volume is:

wherein omega is the volume of the unit control body,in order to control the normal vector on the surface of the body, kappa is the solid heat conductivity coefficient, rho is the density of the solid material, and cP is the specific heat.

In S4, the thermal connection surface between the fluid domain and the solid domain adopts a complete non-matching thermal connection technology, the units obtained by FNMB decomposition algorithm are subjected to thermal coupling equation solution to obtain the independent connection surface temperature and heat flux of each unit, and the surface temperatures of the units on the two sides are calculated through weighted average to obtain the unit body temperature.

In S4, the thermal coupling equation is as follows:

wherein W is present when the cell faces are completely unconnected_i1, when the unit face portions are connected, 0 < W_i< 1, W when fully connected_i＝0。

In S4 and S5, a flow solver numerical value is used for solving a Navier-Stokes equation set during Reynolds, and the specific method is as follows:

wherein, the index range of i and j is 1, 2 and 3, rho is density, S is_MAs source terms of momentum equations, S_EFor the source terms of the energy equation, τ is the tensor of shear stress,in order to take the Reynolds stress term into account,in order to be a turbulent flux, the flow,a work term for stickiness.

In S4, a Boussinesq turbulence model is introduced, and a Navier-Stokes equation set is closed when turbulence calculation Reynolds is assumed, wherein the specific method is as follows:

wherein, mu_effIs effectively adhesive.

At S7, the stress has six components, three positive stresses and three shear stresses, and the matrix form is:

in S7, the change matrix form of the stress is:

at S7, the elastomer strain is caused by two parts of stress and temperature change:

{ε}＝{ε^th}+{ε^el}

wherein [. epsilon. ]^elIs the stress induced strain vector, { ε }^tThe temperature induced strain vector is given by the expression for the elastomer strain for each like material:

{ε^th}＝ΔT[a a a 0 0 0]^T

in the formula: a is the coefficient of linear expansion of the material, Delta T is T-T_refIs the temperature difference between the local temperature and the reference temperature.

Compared with the prior art, the method comprises the steps of firstly carrying out heat-flow coupling calculation between a fluid calculation domain and a solid calculation domain on an established model, carrying out data transmission between the fluid calculation domain and the solid calculation domain by adopting a heat connection surface in order to realize conservation transmission of heat flux and temperature of the fluid calculation domain and the solid calculation domain, and synchronously solving and carrying out real-time data transmission in the fluid calculation domain and the solid calculation domain. And then, carrying out thermal-solid coupling calculation between the fluid calculation domain and the solid calculation domain on the established model, wherein the thermal-solid analysis takes the CFD pressure result transmitted and applied to the solid surface as a boundary condition, reads in the node temperature obtained by the thermal analysis as a thermal load, and applies corresponding constraint conditions and rotating speed at the same time, thereby realizing comprehensive stress analysis of the model and greatly improving the authenticity of the model calculation method and the reliability of the calculation result.

Drawings

FIG. 1 is a computational model of an embodiment of the invention;

FIG. 2 is a vane fluid field grid of an embodiment of the present invention;

FIG. 3 is a leaf solid domain grid of an embodiment of the invention;

FIG. 4 is a result of a blade temperature field calculation according to an embodiment of the present invention;

FIG. 5 is a result of a blade stress field calculation according to an embodiment of the present invention; wherein, (a) is blade centrifugal stress, (b) is blade bending stress, (c) is blade thermal stress, and (d) is blade comprehensive equivalent stress;

FIG. 6 is a flow chart of the present invention.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

Referring to fig. 1 to 6, the present invention includes the steps of:

step one, establishing a blade geometric model through three-dimensional modeling software according to a geometric drawing by referring to a real through-flow structure of a steam turbine, and establishing a fluid and solid calculation domain according to an actual working condition;

step two, adopting commercial software to respectively carry out grid planning on the fluid calculation domain and the solid calculation domain to generate a plurality of structured grids;

step three, determining boundary conditions of the fluid and solid calculation model according to physical reality;

and fourthly, performing heat-flow coupling calculation between the fluid calculation domain and the solid calculation domain on the established model, analyzing heat transfer between the fluid domain and the body domain, performing data transfer between the fluid domain and the solid calculation domain by adopting a heat connection surface in order to realize conservation transfer of heat flux and temperature of the fluid domain and the solid calculation domain, and synchronously solving and transmitting data in real time in the fluid domain and the solid calculation domain.

The lattice-centered finite volume method is used in the calculation of the solid heat transfer analysis. Since there is no flow phenomenon inside the solid, the heat transfer equation can be simplified as follows for solving the temperature change of the solid within a given time step caused by the conservation of heat flux on the fluid-solid coupling surface:

in the formula: omega is unit control volume/m³；Is a normal vector on the control body surface; kappa is solid thermal conductivity/W (m. K)^-1(ii) a Rho is the density of the solid material/kg m^-3；c_PSpecific heat/J (kg. degree. C.)^-1。

The thermal connection surface adopts a complete non-matching thermal connection technology, the temperature and the heat flux of the connection surface of each unit can be obtained by solving a thermal coupling equation of the units obtained by the FNMB decomposition algorithm, and the temperature of the unit body can be further obtained by calculating the surface temperatures of the units on the two sides through weighted average.

Wherein W is when the unit faces are not connected at all_i1, when the unit face portions are connected, 0 < W_i< 1, W when fully connected_i＝0。

Step five, solving a Navier-Stokes equation set in Reynolds through a flow solver numerical value in a fluid domain, introducing a Boussinesq turbulence model hypothesis to enable the Navier-Stokes equation set in turbulence calculation in Reynolds to be closed, and obtaining important pneumatic parameters such as pressure, temperature and flow rate of a fluid calculation domain through calculation;

solving a Navier-Stokes equation set at Reynolds time through a flow solver numerical value, wherein the specific form is as follows:

in the formula: the value ranges of the indexes i and j are (1, 2, 3), and rho is density/kg.m³；S_MIs a source term of momentum equation; s_EIs an energy equation source term; τ is the tensor of shear stress;is the Reynolds stress term;is a turbulent flux;a work term for stickiness.

And introducing a Boussinesq turbulence model hypothesis, closing a Navier-Stokes equation set when turbulence is calculated and reynolds, wherein the specific form is as follows:

in the formula: mu.s_effIs effectively adhesive

And step six, solving the heat conduction equation only in the solid domain, establishing a temperature distribution curve between the fluid domain and the solid domain on the heat connection surface, repeatedly and iteratively solving through a heat balance equation to ensure the heat flux conservation transmission on two sides, and obtaining boundary parameters such as node temperature and the like through calculation. The heat transfer equation is of the form:

h_f(T_w-T_f)＝-h_s(T_w-T_s)

in the formula: h is_fFor fluid side conduction thermal coefficient/W (m.K)^-1；h_sFor solid side conduction thermal coefficient/W (m.K)^-1；T_wIs the temperature of the joint surface/K; t is_fIs the fluid side first layer grid center temperature/K; t is_sThe solid side first layer grid center temperature/K.

The solid-side heat transfer coefficient expression is:

in the formula: kappa is the local thermal conductivity/W (m.K)^-1(ii) a And deltay is the distance/m from the center of the first layer of grids to the wall surface.

And when the first layer of grid is not arranged inside the viscous bottom layer, the convection heat flux is needed, at the moment, the heat transfer between the fluid domain and the solid domain is suitable for adopting a high Reynolds number turbulence model combined with a wall surface function, and the heat transfer coefficient is solved by adopting the following formula:

in the adhesive bottom layer (y)⁺＜13.2)：

T⁺＝Pr y⁺

In the turbulent layer:

and step seven, performing thermal-solid coupling calculation between the fluid calculation domain and the solid calculation domain on the established model, performing thermal-solid coupling analysis by taking the result of the pressure of the fluid domain transferred and applied to the surface of the solid as a boundary condition, reading the temperature of the node obtained by the thermal-current coupling calculation analysis in the step four as a thermal load, further applying corresponding constraint conditions and rotating speed, and finally performing comprehensive stress analysis on the model.

The stress at any point in the elastomer in the three-dimensional problem has 6 components: 3 normal stresses and 3 shear stresses, the matrix form of which is:

the matrix form of the strain is:

according to the thermoelastic theory, elastomer strain is caused by two parts, stress and temperature change:

{ε}＝{ε^th}+{ε^el}

wherein [. epsilon. ]^elIs the stress induced strain vector, { ε }^thIs the temperature induced strain vector, whose expression for isotropic materials is:

{ε^th}＝ΔT[a a a 0 0 0]^T

in the formula: a is the coefficient of linear expansion of the material/m.K^-1；ΔT＝T-T_refIs the temperature difference between the local temperature and the reference temperature.