CN115374636A - Boiler numerical simulation and performance calculation coupled wall temperature prediction method - Google Patents
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Abstract
The invention relates to the technical field of boiler wall temperature calculation, and discloses a boiler wall temperature prediction method by coupling numerical simulation and performance calculation.
Description
Technical Field
The invention relates to the technical field of boiler wall temperature calculation, in particular to a boiler wall temperature prediction method based on coupling of numerical simulation and performance calculation.
Background
At present, a large-scale numerical simulation method is a very important means in the design and optimization process of a large-scale boiler. Reasonable and efficient flow, heat transfer, mass transfer, combustion and pollutant generation sub-models are the key to success of large-scale numerical simulation methods.
However, in the prior art, only numerical simulation is carried out to obtain the wall temperature of the boiler, but the method cannot be combined with the performance of the coal-fired power plant under deep peak shaving, so that the accurate prediction of the wall temperature of the boiler under the deep peak shaving of the coal-fired power plant is seriously influenced.
Disclosure of Invention
The invention provides a wall temperature prediction method for coupling boiler numerical simulation and performance calculation, which solves the technical problem of accurate prediction of the wall temperature of a boiler under deep peak regulation of a coal-fired power plant in the prior art.
In view of this, the first aspect of the present invention provides a method for predicting wall temperature by coupling boiler numerical simulation and performance calculation, comprising the following steps:
s1, modeling a geometric structure of the whole boiler to obtain a physical model of the boiler, setting an initial boundary condition of the wall temperature of the boiler, and constructing a mathematical model of a calculation method of the wall temperature of a heating surface of the boiler;
s2, carrying out numerical simulation on the mathematical model to obtain the heat flow density distribution of the boiler wall surface and the wall temperature distribution of the boiler wall surface;
s3, selecting the wall temperature of the water-cooled wall according to the wall temperature distribution of the boiler wall surface, calculating a wall temperature deviation value through the wall temperature of the water-cooled wall and a preset wall temperature, and comparing the wall temperature deviation value with the preset wall temperature, and if the wall temperature deviation value is larger than a preset deviation threshold value, executing the step S4; if the wall temperature deviation value is not greater than the preset deviation threshold value, outputting the corresponding wall temperature distribution of the boiler wall surface;
s4, taking the wall temperature and the heat flow density of the water-cooled wall as initial conditions of a hydrodynamic calculation method, and calculating the wall temperature of the boiler by using the hydrodynamic calculation method;
and S5, updating the initial boundary condition of the wall temperature of the boiler in the physical model of the boiler according to the wall temperature of the boiler, re-executing the steps S2-S3 until the calculation is converged, and outputting the wall temperature distribution of the wall surface of the corresponding boiler, wherein the calculation convergence condition is that the wall temperature deviation value of the wall temperature of the water-cooled wall and the preset wall temperature is not greater than a preset deviation threshold value.
Preferably, step S1 specifically includes:
the method comprises the steps of modeling a geometric structure of the whole boiler, wherein the whole boiler comprises a hearth, a water-cooled wall area, a combustor, a cold ash bucket, heat exchangers at all levels and a rear flue, in the modeling process, the hearth and the combustor of the whole boiler are respectively and independently modeled to obtain a physical model of the boiler, carrying out grid division on the physical model of the boiler, setting the thicknesses of the water-cooled wall and the furnace top screen type heat exchanger to be zero, setting an initial boundary condition of the wall temperature of the boiler, and constructing a mathematical model of the wall temperature calculation method of the heating surface of the boiler.
Preferably, the mathematical model comprises a turbulence model, a gas-solid two-phase flow model, a pulverized coal particle combustion model, a radiation heat exchange model and a nitrogen oxide generation model;
wherein the turbulence model adopts a Standard k-epsilon two-equation model; the gas-solid two-phase flow model specifically adopts a particle orbit model described by a Lagrange method; the pulverized coal particle combustion model comprises a pyrolysis model, a gas phase combustion model and a coke combustion model, wherein the pyrolysis model specifically adopts a two-step competition equation model, the gas phase combustion model specifically adopts a finite rate/vortex dissipation model, and the coke combustion model specifically adopts a dynamics/diffusion control reaction rate model; the radiation heat exchange model specifically adopts a discrete coordinate radiation model, wherein the radiation absorption coefficient of the gas phase is calculated by adopting a grey gas weighted sum model, and the nitrogen oxide generation model specifically adopts a CFD numerical simulation program.
Preferably, step S4 specifically includes:
taking the wall temperature and the heat flow density of the water-cooled wall as initial conditions of a hydrodynamic calculation method;
the tube wall temperature of the boiler was calculated by the following equation 1:
in formula 1, t q Presetting the temperature of steam in the pipe of the pipe section;
beta is the ratio of the outer diameter of the tube to the inner diameter of the tube;
mu is a heat dissipation coefficient, mu is 1 for the first row of tubes of the screen superheater, or the heat dissipation coefficient is calculated by interpolation according to the Bio-ohm criterion number Bi and the ratio beta of the outer diameter of the tubes to the inner diameter of the tubes, wherein,
q is the thermal load of the wall surface of the point pipe;
α 1 presetting the convection heat release coefficient of the flue gas side of the pipe section;
delta is the wall thickness of the tube;
α 2 heat release coefficient for the vapor side;
lambda is the heat conductivity coefficient of the metal of the tube wall;
wherein the point tube wall heat load q is calculated by the following formula 2:
in the formula 2, theta is the flue gas temperature of the preset pipe section, alpha 3 The heat release coefficient of the flue gas radiation of a preset pipe section is obtained; epsilon is the pollution coefficient of the pipe with the preset pipe section;
the smoke side convective heat release coefficient α was calculated by the following equation 3 1 Comprises the following steps:
in formula 3, K TP The coefficient of non-uniform heat absorption along the circumference of the pipe when the flue gas transversely scours the pipe bundle; c Z The correction coefficient is the row number of the tubes in the depth direction of the flue; d 1 Is the outer diameter of the tube; lambda [ alpha ] 1 The heat conductivity coefficient of the flue gas of a preset pipe section; v. of 1 For movement of smokeA viscosity coefficient; w is a 1 The flue gas speed of a preset pipe section;
wherein, the flue gas velocity w of the preset pipe section is calculated by the following formula 4 1 Comprises the following steps:
in the formula 4, B p Calculating fuel consumption for the boiler; v. of r Is the flue gas volume produced per unit of fuel; f r Is the cross-section flue gas flow area;
wherein the steam side convective heat release coefficient α was calculated by the following formula 5 2 Comprises the following steps:
in formula 5, λ 2 Presetting the steam heat conductivity coefficient of the pipe section; d 2 Is the inner diameter of the tube; v. of 2 Setting the steam motion viscosity coefficient of the pipe section; pr is the Plantt number of the steam of the preset pipe section; c t For correction of the coefficient, C is usually taken for the water vapor t ＝1；C l Correcting the coefficient for the relative length; w is a 2 The steam flow rate for a preset pipe section is calculated by the following equation 6:
in formula 6, D i 、v p 、f n Respectively the flow rate, specific volume and flow area of steam in the pipe, wherein the specific volume v p Calculating by a thermodynamic calculation program according to the steam temperature and the steam pressure;
wherein the point flue gas radiation heat release coefficient alpha is calculated by the following formula 7 3 Obtaining:
in the formula 7, the compound represented by the formula,
is the exposure coefficient at which radiant heat is most absorbed from the furnace; alpha (alpha) ("alpha") q The radiation heat release coefficient of the front smoke window to the first row of tubes; alpha is alpha p Is the radiation heat release coefficient of the flue gas between the screens.
According to the technical scheme, the invention has the following advantages:
the invention provides a wall temperature prediction method for coupling boiler numerical simulation and performance calculation, which comprises the steps of building a model of a geometric structure of a boiler, constructing a mathematical model of a wall temperature calculation method of a heating surface of the boiler, obtaining heat flow density distribution of the wall surface of the boiler and wall temperature distribution of the wall surface of the boiler through numerical simulation, correcting hydrodynamic calculation by taking the wall temperature and the heat flow density of a water wall as initial conditions of the hydrodynamic calculation method, calculating the wall temperature of the wall of the boiler by using the hydrodynamic calculation method, correcting initial boundary conditions of the wall temperature of the boiler in a boiler physical model according to the wall temperature of the wall of the boiler, re-performing numerical simulation until calculation convergence, obtaining the corresponding wall temperature distribution of the wall surface of the boiler, realizing the coupling between the numerical simulation and the calculation, and improving the prediction accuracy of the wall temperature of the boiler under the deep peak load regulation of a coal-fired power plant.
Drawings
FIG. 1 is a flow chart of a method for predicting wall temperature by coupling boiler numerical simulation and performance calculation according to an embodiment of the present invention;
FIG. 2 is a grid schematic of a combustor area cross-section provided by an embodiment of the present invention;
FIG. 3 is a schematic grid diagram of a central cross section of a furnace provided by an embodiment of the present invention;
fig. 4 is a grid schematic diagram of an overall cross section of a boiler provided by an embodiment of the invention.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
For easy understanding, referring to fig. 1, the method for predicting the wall temperature by coupling the boiler numerical simulation and the performance calculation according to the present invention includes the following steps:
s1, modeling a geometric structure of the whole boiler to obtain a physical model of the boiler, setting initial boundary conditions of the wall temperature of the boiler, and constructing a mathematical model of the wall temperature calculation method of the heating surface of the boiler.
And S2, carrying out numerical simulation on the mathematical model to obtain the heat flow density distribution of the boiler wall surface and the wall temperature distribution of the boiler wall surface.
S3, selecting the wall temperature of the water-cooled wall according to the wall temperature distribution of the wall surface of the boiler, calculating a wall temperature deviation value through the wall temperature of the water-cooled wall and a preset wall temperature, and comparing the wall temperature deviation value with the preset wall temperature, and if the wall temperature deviation value is greater than a preset deviation threshold value, executing the step S4; and if the wall temperature deviation value is not greater than the preset deviation threshold value, outputting the corresponding wall temperature distribution of the boiler wall surface.
And S4, taking the wall temperature and the heat flow density of the water-cooled wall as initial conditions of a hydrodynamic calculation method, and calculating the wall temperature of the boiler by using the hydrodynamic calculation method.
Wherein the tube wall temperature is the tube wall temperature of a water-cooled wall or a superheater of the boiler.
And S5, updating the initial boundary condition of the wall temperature of the boiler in the physical model of the boiler according to the wall temperature of the boiler, re-executing the steps S2-S3 until the calculation is converged, and outputting the wall temperature distribution of the wall surface of the corresponding boiler, wherein the calculation convergence condition is that the wall temperature deviation value of the wall temperature of the water wall and the preset wall temperature is not greater than a preset deviation threshold value.
In the embodiment, the initial wall temperature of the boiler is measured on site, and the initial boundary condition of the wall temperature of the boiler is corrected by calculating the wall temperature of the boiler through a hydrodynamic calculation method, so that the simulation calculation accuracy is improved.
The embodiment provides a wall temperature prediction method for coupling boiler numerical simulation and performance calculation, which includes the steps of building a mathematical model of a boiler heating surface wall temperature calculation method by modeling a geometric structure of a boiler, obtaining heat flow density distribution of a boiler wall surface and wall temperature distribution of the boiler wall surface through numerical simulation, correcting hydrodynamic calculation by taking the wall temperature and the heat flow density of a water-cooled wall as initial conditions of the hydrodynamic calculation method, calculating the wall temperature of the boiler by using the hydrodynamic calculation method, correcting initial boundary conditions of the boiler wall temperature in a boiler physical model according to the wall temperature of the boiler, performing numerical simulation again until calculation convergence, obtaining the corresponding wall temperature distribution of the boiler wall surface, achieving coupling between the numerical simulation and the hydrodynamic calculation, and improving prediction accuracy of the boiler wall temperature under deep peak load regulation of a coal-fired power plant.
In a specific embodiment, step S1 specifically includes:
the method comprises the steps of modeling a geometric structure of the whole boiler, wherein the whole boiler comprises a hearth, a water-cooled wall area, a combustor, a cold ash bucket, heat exchangers at all levels and a rear flue, in the modeling process, the hearth and the combustor of the whole boiler are respectively and independently modeled to obtain a physical model of the boiler, carrying out grid division on the physical model of the boiler, setting the thicknesses of the water-cooled wall and the furnace top screen type heat exchanger to be zero, setting an initial boundary condition of the wall temperature of the boiler, and constructing a mathematical model of the wall temperature calculation method of the heating surface of the boiler.
The modeling software can adopt Solidworks software, in the modeling process, the furnace chamber, the water-cooled wall area, the combustor, the cold ash bucket, each level of heat exchangers and the rear flue in the whole boiler are set according to actual positions, meanwhile, the appropriate simplification is carried out, the thicknesses of the water-cooled wall and the furnace top screen type heat exchanger are considered to be zero, the boundary condition of the wall temperature is set to be constant, meanwhile, the ICEM software is used for carrying out grid division, a regional and structured division method is adopted, and high-quality hexahedral structured grids are used for division. Meanwhile, in order to accurately simulate the characteristic of large physical vignetting gradient change of the primary combustion zone, the region of the burner is encrypted so as to accurately simulate the flow characteristic of the region. Because the cross section of the burner area is octagonal, and the cross sections of the upper part and the lower part are quadrilateral, the interface is arranged at the junction to ensure the data transmission between grids at the interface. After the grid independence judgment, the number of the selected grids is 2 560 727. Wherein, the cross section of the burner area, the grid of the central section of the furnace and the grid of the whole boiler are respectively shown as figure 2, figure 3 and figure 4.
In a specific embodiment, the mathematical model comprises a turbulence model, a gas-solid two-phase flow model, a pulverized coal particle combustion model, a radiation heat exchange model and a nitrogen oxide generation model;
wherein the turbulence model adopts a Standard k-epsilon two-equation model;
it should be noted that the gas flow in the furnace is a three-dimensional turbulent flow, and the present embodiment describes the fluid flow by using a Standard k-epsilon two-equation model. The Standard k-epsilon model has the best calculation economy and stability on the premise of ensuring the precision requirement on engineering application, and is widely applied to the calculation of the flow field in the boiler.
The gas-solid two-phase flow model specifically adopts a particle orbit model described by a Lagrange method;
it should be noted that the in-furnace process involves two-phase flow of pulverized coal particles and gas, and the movement and dispersion of the pulverized coal have a great influence on the combustion process. The calculation takes into account the interaction of the particles and the gas phase every 20 gas phase field iterations. The thermal mass changes caused by particle heating, pyrolysis volatilization and combustion processes of coke particles are considered in the particle motion equation.
The pulverized coal particle combustion model comprises a pyrolysis model, a gas phase combustion model and a coke combustion model, wherein the pyrolysis model specifically adopts a two-step competition equation model, the gas phase combustion model specifically adopts a finite rate/vortex dissipation model, and the coke combustion model specifically adopts a dynamics/diffusion control reaction rate model;
it should be noted that, due to the complex composition of the pulverized coal, the physicochemical reaction process of the pulverized coal is also complex. The heating of the coal dust particles in the hearth mainly comprises four stages: particle heating, volatile matter separation, coke burning and burnout.
(1) Pyrolysis model
The pulverized coal particles are continuously heated, so that pyrolysis volatilization can occur, and the phase is a volatilization analysis phase. In this embodiment, a traditional two-step competition equation model is used to describe the deposition of the volatile components, and different velocity expressions are used in different temperature ranges to calculate the deposition rate of the volatile components. The volatile components produced by pyrolysis enter the combustion process in the gas phase.
(2) Gas phase combustion model
The gas burned in the boiler under high temperature condition includes gas phase product released by heterogeneous reaction and coal powder pyrolysis gas product. The present embodiment employs a finite velocity/vortex dissipation model to describe gas phase combustion.
(3) Coke combustion model
The burning of coke plays a leading role in the burning of the powder. Generally involves two processes, one is the diffusion of the oxides to the particle surface and the heterogeneous reaction of the particle surface with the coke. The combustion of the coke is dynamic-diffusion combustion, namely the combustion of the coke is related to kinetic factors and is related to heat and mass transfer, a kinetic/diffusion control reaction rate model is selected to simulate the combustion process of the pulverized coal in the furnace, and the combustion rate of the coke is controlled by two factors, namely the rate of oxygen diffusion to the surface of the coke and the chemical reaction rate of the surface of the coke.
The radiation heat exchange model specifically adopts a discrete coordinate radiation model, wherein the radiation absorption coefficient of the gas phase is calculated by adopting a grey gas weighted sum model, and the nitrogen oxide generation model specifically adopts a CFD numerical simulation program.
It should be noted that, in the operation process of the utility boiler, the central temperature of the flame is very high, so the heat absorption mode of the water-cooled wall is mainly radiation heat exchange. In the embodiment, the description of the radiation process in the furnace adopts a discrete-coordinate radiation (DO) model, wherein the radiation absorption coefficient of a gas phase is calculated by adopting a weighted-sum-of-gray-gases (WSGGM) model.
In a specific embodiment, step S4 specifically includes:
s401, taking the wall temperature and the heat flow density of the water wall as initial conditions of the hydrodynamic calculation method.
It should be noted that the thermal load or the heat flux density is a prerequisite for the hydrodynamic calculation, and the hydrodynamic calculation calculates the accurate wall temperature according to the heat flux density. The heat flux density is obtained by numerical simulation of the boiler, and the accuracy of the numerical simulation is related to the wall temperature, so that the embodiment performs coupled calculation through the numerical simulation and hydrodynamic calculation.
In the coupled calculation process of boiler performance calculation and numerical simulation, the heat transfer data of the boiler side and the furnace side of the boiler are mainly transmitted. The interface of the boiler side and the furnace side is the fire-facing heat absorption side surface of the water-cooled wall, the heat flux density and the temperature on the surface need to be transmitted during coupling calculation, wherein the heat flux density is obtained by simulating the combustion value of the hearth, the heat flux density is transmitted to the boiler side to carry out hydrodynamic force and pipe wall temperature calculation, and the pipe wall temperature obtained by calculation of the boiler side is transmitted back to the hearth to serve as the temperature boundary condition of numerical simulation of the furnace side, so that the coupling calculation is realized.
The boilers can be divided into four types, namely natural circulation boilers, once-through boilers, forced circulation boilers and composite circulation boilers according to different flowing modes of working media in an evaporation system. Under the stable operation condition of various boilers, the hydrodynamic force calculation of the water wall in the boiler can be concluded as the balance problem of flow, pressure difference and enthalpy value.
The method is characterized in that tube groups are divided for different boiler water wall systems, and the method is mainly divided into three typical forms according to the difference of the link modes of the tube groups and the return: (1) a simple tube set; (2) The structure and the heating characteristic of each parallel pipe in the first-stage parallel pipe group are different, but the parallel pipes share the same inlet pipe and outlet pipe; (3) The secondary parallel pipe group consists of an inlet pipe, a plurality of parallel pipes and a plurality of outlet pipes.
In a specific example, the grid division is performed according to the distribution characteristics of the heat load curve, the position with high heat load is divided into thinner grids, and the position with low heat load is divided into thicker grids.
S402, calculating the tube wall temperature of the boiler according to the following formula 1:
in formula 1, t q Presetting the temperature of steam in a pipe of the pipe section;
wherein, the temperature of the steam in the pipe can be obtained by calculation according to the pressure and the enthalpy value in the pipe, or the temperature of the steam in the pipe can be obtained by inquiring a water and steam calculation table of the boiler.
Beta is the ratio of the outer diameter of the tube to the inner diameter of the tube;
mu is a heat dissipation coefficient, mu is 1 for the first row of tubes of the screen superheater, or the heat dissipation coefficient is calculated by interpolation according to the Bioho criterion number Bi and the ratio beta of the outer diameter of the tubes to the inner diameter of the tubes, wherein,
meanwhile, the heat dissipation coefficient can also be obtained by looking up the literature.
q is the thermal load of the wall surface of the point pipe;
α 1 presetting the convection heat release coefficient of the flue gas side of the pipe section;
delta is the wall thickness of the tube;
α 2 heat release coefficient for the vapor side;
lambda is the heat conductivity coefficient of the metal of the tube wall;
wherein the point pipe wall surface heat load q is calculated by the following formula 2:
in the formula 2, theta is the flue gas temperature of the preset pipe section, alpha 3 Flue gas of preset pipe sectionThe radiant heat release coefficient; epsilon is the pollution coefficient of the pipe with the preset pipe section;
the smoke side convective heat release coefficient α was calculated by the following equation 3 1 Comprises the following steps:
in formula 3, K TP The coefficient of non-uniform heat absorption along the circumference of the pipe when the flue gas transversely scours the pipe bundle; c Z The correction coefficient is the row number of the tubes in the depth direction of the flue; d 1 Is the outer diameter of the pipe; lambda [ alpha ] 1 The heat conductivity coefficient of the flue gas of a preset pipe section; v. of 1 Is the kinematic viscosity coefficient of the smoke; w is a 1 The flue gas speed of a preset pipe section;
wherein, the flue gas velocity w of the preset pipe section is calculated by the following formula 4 1 Comprises the following steps:
in formula 4, B p Calculating fuel consumption for the boiler; v. of r Is the flue gas volume produced per unit of fuel; f r Is the cross-section flue gas flow area;
wherein the steam side convective heat release coefficient α is calculated by the following formula 5 2 Comprises the following steps:
in formula 5, [ lambda ] 2 Presetting the steam heat conductivity coefficient of the pipe section; d 2 Is the inner diameter of the tube; v. of 2 Setting the steam motion viscosity coefficient of the pipe section; pr is the Plantt number of the steam of the preset pipe section; c t For correcting the coefficient, C is usually given for water vapor t ＝1；C l A relative length correction factor; w is a 2 The steam flow rate for a preset pipe section is calculated by the following equation 6:
in formula 6, D i 、v p 、f n Respectively the flow rate, specific volume and flow area of steam in the pipe, wherein the specific volume v p Calculating by a thermodynamic calculation program according to the steam temperature and the steam pressure;
wherein the point flue gas radiation heat release coefficient alpha is calculated by the following formula 7 3 Obtaining:
in the formula 7, the compound represented by the formula,
is the exposure coefficient at which radiant heat is most absorbed from the furnace; alpha is alpha q The radiation heat release coefficient of the front smoke window to the first row of tubes; alpha is alpha p The radiation heat release coefficient of the flue gas between the screens.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (4)
1. A boiler numerical simulation and performance calculation coupled wall temperature prediction method is characterized by comprising the following steps:
s1, modeling a geometric structure of the whole boiler to obtain a physical model of the boiler, setting an initial boundary condition of the wall temperature of the boiler, and constructing a mathematical model of a calculation method of the wall temperature of a heating surface of the boiler;
s2, carrying out numerical simulation on the mathematical model to obtain the heat flow density distribution of the boiler wall surface and the wall temperature distribution of the boiler wall surface;
s3, selecting the wall temperature of the water-cooled wall according to the wall temperature distribution of the boiler wall surface, calculating a wall temperature deviation value through the wall temperature of the water-cooled wall and a preset wall temperature, and comparing the wall temperature deviation value with the preset wall temperature, and if the wall temperature deviation value is larger than a preset deviation threshold value, executing the step S4; if the wall temperature deviation value is not greater than the preset deviation threshold value, outputting the corresponding wall temperature distribution of the boiler wall surface;
s4, taking the wall temperature and the heat flow density of the water-cooled wall as initial conditions of a hydrodynamic calculation method, and calculating the wall temperature of the boiler by using the hydrodynamic calculation method;
and S5, updating the initial boundary condition of the wall temperature of the boiler in the physical model of the boiler according to the wall temperature of the boiler, re-executing the steps S2-S3 until the calculation is converged, and outputting the wall temperature distribution of the wall surface of the corresponding boiler, wherein the calculation convergence condition is that the wall temperature deviation value of the wall temperature of the water-cooled wall and the preset wall temperature is not greater than a preset deviation threshold value.
2. The boiler numerical simulation and performance calculation coupled wall temperature prediction method according to claim 1, wherein the step S1 specifically comprises:
the method comprises the steps of modeling a geometric structure of the whole boiler, wherein the whole boiler comprises a hearth, a water-cooled wall area, a combustor, a cold ash bucket, heat exchangers at all levels and a rear flue, in the modeling process, the hearth and the combustor of the whole boiler are respectively and independently modeled to obtain a physical model of the boiler, carrying out grid division on the physical model of the boiler, setting the thicknesses of the water-cooled wall and the furnace top screen type heat exchanger to be zero, setting an initial boundary condition of the wall temperature of the boiler, and constructing a mathematical model of the wall temperature calculation method of the heating surface of the boiler.
3. The boiler numerical simulation and performance calculation coupled wall temperature prediction method according to claim 2, wherein the mathematical model comprises a turbulence model, a gas-solid two-phase flow model, a pulverized coal particle combustion model, a radiation heat exchange model and a nitrogen oxide generation model;
wherein the turbulence model adopts a Standard k-epsilon two-equation model; the gas-solid two-phase flow model specifically adopts a particle orbit model described by a Lagrange method; the pulverized coal particle combustion model comprises a pyrolysis model, a gas phase combustion model and a coke combustion model, wherein the pyrolysis model specifically adopts a two-step competition equation model, the gas phase combustion model specifically adopts a finite rate/vortex dissipation model, and the coke combustion model specifically adopts a dynamics/diffusion control reaction rate model; the radiation heat exchange model specifically adopts a discrete coordinate radiation model, wherein the radiation absorption coefficient of the gas phase is calculated by adopting a grey gas weighted sum model, and the nitrogen oxide generation model specifically adopts a CFD numerical simulation program.
4. The boiler numerical simulation and performance calculation coupled wall temperature prediction method according to claim 2, wherein the step S4 specifically comprises:
taking the wall temperature and the heat flux density of the water-cooled wall as initial conditions of a hydrodynamic calculation method;
the tube wall temperature of the boiler was calculated by the following equation 1:
in formula 1, t q Presetting the temperature of steam in the pipe of the pipe section;
beta is the ratio of the outer diameter of the tube to the inner diameter of the tube;
mu is a heat dissipation coefficient, mu is 1 for the first row of tubes of the screen superheater, or the heat dissipation coefficient is calculated by interpolation according to the Bioho criterion number Bi and the ratio beta of the outer diameter of the tubes to the inner diameter of the tubes, wherein,
q is the thermal load of the wall surface of the point pipe;
α 1 presetting the convection heat release coefficient of the flue gas side of the pipe section;
delta is the wall thickness of the tube;
α 2 heat release coefficient for the vapor side;
lambda is the heat conductivity coefficient of the metal of the tube wall;
wherein the point pipe wall surface heat load q is calculated by the following formula 2:
in the formula 2, theta is the flue gas temperature of the preset pipe section, alpha 3 The heat release coefficient of the flue gas radiation of a preset pipe section is set; epsilon is the pollution coefficient of the pipe with the preset pipe section;
the smoke side convective heat release coefficient α was calculated by the following formula 3 1 Comprises the following steps:
in formula 3, K TP The coefficient of non-uniform heat absorption along the circumference of the pipe when the flue gas transversely washes the pipe bundle; c Z A correction coefficient for the number of rows of tubes in the depth direction of the flue; d is a radical of 1 Is the outer diameter of the pipe; lambda [ alpha ] 1 The heat conductivity coefficient of the flue gas of a preset pipe section; v. of 1 Is the kinematic viscosity coefficient of the smoke; w is a 1 The flue gas velocity of a preset pipe section;
wherein, the flue gas velocity w of the preset pipe section is calculated by the following formula 4 1 Comprises the following steps:
in the formula 4, B p Calculating fuel consumption for the boiler; v is r Is the flue gas volume produced per unit of fuel; f r Is the cross-section flue gas flow area;
wherein the steam side convective heat release coefficient α was calculated by the following formula 5 2 Comprises the following steps:
in formula 5, λ 2 Presetting the steam heat conductivity coefficient of the pipe section; d is a radical of 2 Is the inner diameter of the tube; v. of 2 Setting the steam motion viscosity coefficient of the pipe section; pr is the Plantt number of the steam of the preset pipe section; c t For correction of the coefficient, C is usually taken for the water vapor t ＝1；C l A relative length correction factor; w is a 2 The steam flow rate for the preset pipe section is calculated by the following formula 6:
in formula 6, D i 、ν p 、f n Respectively the flow rate, specific volume and flow area of the steam in the pipe, wherein the specific volume v p Calculating by a thermodynamic calculation program according to the steam temperature and the steam pressure;
wherein the point flue gas radiation heat release coefficient alpha is calculated by the following formula 7 3 Obtaining:
in the formula 7, the compound represented by the formula,
exposure coefficient is the position where the radiant heat is most absorbed from the furnace; alpha (alpha) ("alpha") q The radiation heat release coefficient of the front smoke window to the first row of tubes; alpha is alpha p Is the radiation heat release coefficient of the flue gas between the screens.
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