JP2012211757A - Program and method for numerically analyzing combusting flow - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a program for numerically analyzing a combusting flow, which can reduce computational loads in the numerical analysis of a flow associated with combustion, and also enhance versatility close to a detailed reaction model and prediction accuracy, and to provide a method for numerically analyzing a combusting flow.SOLUTION: The program for numerically analyzing a combusting flow includes: a chemical reaction condition database creating means 6 for obtaining a chemical reaction condition during combustion by a numerical analysis using a predetermined conserved scalar variable and storing the chemical reaction condition in a chemical reaction condition database 42; an instant/local conserved scalar variable obtaining means 7 for obtaining an instant/local conserved scalar variable by a numerical analysis; an instant/local chemical reaction condition calculation means 8 for calculating an instant/local chemical reaction condition; an instant/local physical property value calculation means 9 for calculating an instant/local physical property value; and a combusting flow analyzing means 10 for numerically analyzing the flow associated with combustion by using the instant/local chemical reaction condition and the instant/local physical property value.

Description

  The present invention relates to a combustion flow numerical analysis program and a combustion flow numerical analysis method for numerically analyzing a flow accompanying combustion of hydrogen fuel and / or hydrocarbon fuel and oxidant.

Currently, about half of the world's energy supply is made up of hydrogen and hydrocarbon fuels. Therefore, optimization of combustion technology using hydrogen fuel and hydrocarbon fuel as one of the fuels is one of the important issues for reducing CO ₂ emissions.

Generally, combustion of a fuel and an oxidant is constituted by a multistage reaction with a large number of molecular species, and the combustion process is mainly governed by the following relationship.
(1) Chemical reaction elementary process (2) Mass conservation law for all chemical species present in chemical reaction process (3) Momentum conservation law for combustion mixture (4) Energy conservation law for combustion mixture

  Moreover, in order to specify the thermal conditions of the unsteady and non-uniform combustion mixture, it is necessary to provide the thermal property values of each chemical species and the state equation of the combustion mixture.

  For example, the chemical reaction process is considered to consist of 9 chemical substances and 21 elementary reactions when hydrogen fuel is used. In the case of using a hydrocarbon fuel, it is considered that 30 to several hundred kinds of chemical substances and 300 to 1000 or more elementary reactions are involved.

  In addition, the chemical reaction spatial scale and time scale are about 1/10 of the flow spatial scale and time scale, which is a reaction in a small space and in a short time. It must be finer than that. Therefore, when a numerical analysis of the governing equation is directly performed without using an approximate model for such a multistage reaction with a large number of molecular species, a huge calculation load is required. Therefore, although the chemical reaction element process has been studied in detail, it has been difficult to simultaneously analyze various multistage chemical reactions such as combustion flows and flows.

  Under such recognition, various methods have been proposed in the past for modeling chemical reactions and reducing the computational load by numerical analysis. For example, there is a so-called “simple reaction model” (Non-Patent Document 1, Non-Patent Document 2) that approximates a chemical reaction as a simple process. This simple reaction model assumes a virtual chemical reaction approximated to an actual reaction and calculates a chemical reaction by empirically determining a constant.

  In addition, many combustion phenomena in actual equipment such as gas turbines, furnaces, rocket engines, gasoline engines, boilers, and chemical synthesizers have similarities that do not depend on the type of fuel, and fuel and oxidizers are subsonic. It is known that a thin flame is formed in the case of flowing at a relatively slow speed of the above, and a method called “framelet approximation model” that approximates the thin flame by its characteristic function assuming the formation of the thin flame (non-patent There are literature 3 and non-patent literature 4).

  In this flamelet approximation model, the numerical analysis of the chemical reaction and the numerical analysis of the flow are separately performed in advance by using a conservative scalar variable representing the diffusion mixing of the combustion mixture of fuel and oxidant. .

The Japan Society of Mechanical Engineers, "Numerical calculation of combustion", Maruzen, February 2001, p1, 32, 59-86 Hashimoto et al., “A numerical analysis of pulverized combustion in a multi-burner furnace”, Energy & Fuels, USA, American Chemical Society, June 29, 2007, Vol. 21, p1950-1958 Norbert PETERS, “Turbulence combustion”, UK, Cambridge University Press, 2000, Vol. 21, p170-236 Nobuyuki Oshima, Takuji Nakajima, “Combustion Flow LES”, Journal of the Gas Turbine Society of Japan, July 2007, Vol. 35, no. 4, p9-14

  However, in the numerical analysis method of the combustion flow based on the simple reaction model as described in Non-Patent Document 1 and Non-Patent Document 2, since empirical constants are used, the chemical reaction is different from the actual one. There is a problem that the results are greatly different if the theoretical basis is poor and an appropriate constant cannot be given. For example, trace chemical species and side reaction processes necessary for the reaction of a specific product such as nitrogen oxide are lacking, and therefore, an empirical model must be relied upon for their prediction. In addition, since the production amount in the chemical reaction process is directly handled, it is necessary to evaluate the apparent reaction promotion when the turbulent field is approximated by an average, and the generality and the prediction accuracy are inferior.

  In addition, the numerical analysis method of combustion flow by the flamelet approximation model as described in Non-Patent Document 3 and Non-Patent Document 4 lacks versatility with respect to various fuels or changes in flow and thermal conditions. There is a problem that the range and analysis accuracy are limited in principle. For example, only numerical analysis of adiabatic conditions can be performed, and the Lewis number must be assumed to be 1 so that the diffusion coefficient of chemical species and enthalpy approximately match. Further, only one type of fuel can be handled, and the initial temperature of the supply source can be set to only one temperature. Similarly, only one oxidant can be handled, and the initial temperature of the supply source can be set to only one temperature.

  The present invention has been made to solve such problems, and reduces the calculation load in the numerical analysis of the flow accompanied by combustion, and improves versatility close to a detailed reaction model and prediction accuracy. It is an object to provide a combustion flow numerical analysis program and a combustion flow numerical analysis method.

  A combustion flow numerical analysis program according to the present invention is a combustion flow numerical analysis program for numerically analyzing a flow accompanied by combustion of a hydrogen fuel and / or a hydrocarbon-based fuel and an oxidant, the fuel, the oxidant, and those Among the plurality of stored scalar variables set based on each chemical composition in the combustion air-fuel mixture mixed with, a chemical reaction condition at the time of combustion is obtained by numerical analysis using the predetermined stored scalar variable, and the chemical reaction condition Chemical reaction condition database creation means for storing the chemical reaction condition database in the chemical reaction condition database, instantaneous / locally preserved scalar variable acquisition means for obtaining the instantaneous / locally preserved scalar variable by numerical analysis using the equation of motion of the preserved scalar variable, and the chemistry Using the chemical reaction conditions stored in the reaction condition database and the instantaneous and locally stored scalar variables Instantaneous / local chemical reaction condition calculating means for calculating time / local chemical reaction conditions; and instantaneous / local physical property value calculating means for calculating instantaneous / local physical property values using the instantaneous / local chemical reaction conditions and predetermined physical property values; The computer functions as combustion flow analysis means for numerically analyzing a flow accompanied by combustion of the fuel, the oxidant, and the combustion mixture using the instantaneous / local chemical reaction conditions and the instantaneous / local physical property values. It is said.

  Further, the combustion flow numerical analysis method according to the present invention is a combustion flow numerical analysis method for numerically analyzing a flow accompanied by combustion of hydrogen fuel and / or hydrocarbon fuel and oxidant, wherein the fuel, the oxidant And a chemical reaction condition at the time of combustion is obtained by numerical analysis using a predetermined stored scalar variable among a plurality of stored scalar variables set based on each chemical composition in a combustion mixture in which they are mixed. A chemical reaction condition database creation step for storing reaction conditions in a chemical reaction condition database; an instantaneous / locally stored scalar variable acquisition step for acquiring an instantaneous / locally stored scalar variable by numerical analysis using the motion equation of the stored scalar variable; Using chemical reaction conditions stored in the chemical reaction condition database and the instantaneous and locally stored scalar variables An instantaneous / local chemical reaction condition calculating step for calculating an instantaneous / local chemical reaction condition; and an instantaneous / local physical property value calculating step for calculating an instantaneous / local physical property value using the instantaneous / local chemical reaction condition and a predetermined physical property value; And a combustion flow analysis step for numerically analyzing a flow accompanied by combustion of the fuel, the oxidant and the combustion mixture using the instantaneous / local chemical reaction conditions and the instantaneous / local physical property values. .

  That is, the combustion flow numerical analysis program and the combustion flow numerical analysis method according to the present invention provide a flow analysis with combustion based on a flamelet approximation model focusing on the similarity in the combustion process of hydrogen fuel and hydrocarbon fuel. In the conventional method, the index variables selected from the empirical viewpoint are physically and mathematically specified, and a general-purpose numerical analysis program for combustion flow is constructed by combining them.

  Further, in the present invention, the chemical reaction condition database creation means includes a stored scalar variable setting unit for setting four types of stored scalar variables, and values of predetermined two types of stored scalar variables among the four types of stored scalar variables. A variable value combination setting unit for setting an arbitrary combination according to the above, a chemical reaction condition acquisition unit for acquiring the chemical reaction condition in the combination by polynomial approximation of the other two types of stored scalar variables, and the acquired chemical reaction condition It is good also as a structure provided with the database preparation part which memorize | stores it in the said chemical reaction condition database.

  Further, in the present invention, the storage scalar variable is a mass fraction ratio scalar variable set based on a mass fraction ratio of carbon contained in the fuel, the oxidizer, and the combustion mixture, the fuel, An enthalpy piece color variable set based on an enthalpy ratio of an oxidant and the combustion mixture; a fuel composition scalar variable set based on a mass ratio of hydrogen and carbon contained in the fuel or the combustion mixture; and It may be an oxidant or a oxidant composition scalar variable set based on a mass ratio of oxygen and nitrogen contained in the combustion mixture.

That is, the storage scalar variables are defined as hydrogen fuel (H ₂ ) and / or hydrocarbon fuel (C _n H _m ), oxygen (O ₂ ) and / or air (O ₂ + N ₂ + a small amount of inert noble gas). ) In the case of combustion with an oxidant, by setting the mass conservation law of hydrogen H, carbon C, oxygen O and nitrogen N and the conservation law of total enthalpy, In the approximate model, the heat insulation condition, the condition of Lewis number = 1, the fuel and the oxidant do not need to be restricted in numerical analysis such as one kind of condition each.

  In the present invention, the combustion flow analysis means may be analysis means based on a large eddy simulation method.

  In other words, the large eddy simulation (LES) method, which performs unsteady calculation using the spatial averaging equation, is adopted as an extension to the turbulent combustion model that is important in actual equipment. The implementation enables simulation of turbulent combustion flow.

  ADVANTAGE OF THE INVENTION According to this invention, while reducing the calculation load in the numerical analysis of the flow accompanying combustion, the versatility close | similar to a detailed reaction model and prediction accuracy can be improved.

It is a block diagram showing one embodiment of a computer provided with a combustion flow numerical analysis program concerning the present invention. It is the schematic which shows the range of the value of the combustion field of this embodiment, and the fuel composition scalar variable (xi) _f assumed. It is the schematic which shows the arbitrary combinations of two types of preservation | save scalar variables set by the variable value combination setting part of this embodiment. It is the schematic which shows the example of calculation of the instantaneous and local chemical reaction conditions in the instantaneous and local chemical reaction condition calculation means of this embodiment. It is a functional block diagram which shows the function of each structure of this embodiment. It is a flowchart figure which shows the flow of a process in the combustion flow numerical analysis program and combustion flow numerical analysis method of this embodiment. It is a flowchart figure which shows the flow of the process in the chemical reaction condition database preparation means of this embodiment. It is a perspective view which shows the cylindrical combustion flow field imitating the triple diffusion burner made into the analysis object in this Example 1. FIG. It is an enlarged view which shows the triple diffusion burner part of the combustion flow field made into the analysis object in Example 1. FIG. It is a three-dimensional graph which shows the database of the density created by the chemical reaction condition database creation means of the present Example 1. It is a distribution map which shows the time average value of the mass fraction ratio scalar variable (xi) of the XY cross section in the combustion flow field of the present Example 1. FIG. 6 is a distribution diagram showing a time average value of an oxidant composition scalar variable ξ _{o in} the XY cross section in the combustion flow field of the first embodiment. It is a distribution map which shows the time average value of the temperature of the XY cross section in the combustion flow field of the present Example 1. It is a distribution map which shows the time average value of the mass fraction ratio scalar variable (xi) of the XY cross section in the combustion flow field analyzed by the flamelet approximation model. It is a distribution map which shows the time average value of the temperature of the XY cross section in the combustion flow field analyzed by the flamelet approximation model. It is a distribution map which shows the time average value of the temperature on the Y-axis in the position of X = 100mm by the present Example 1 and a flamelet approximation model. It is a distribution map which shows the time average value of the temperature on the Y-axis in the position of X = 300mm by the present Example 1 and a flamelet approximation model. It is a distribution map which shows the time average value of the temperature on the Y-axis in the position of X = 500mm by the present Example 1 and a flamelet approximation model. It is a distribution map which shows the time average value of the temperature on the Y-axis in the position of X = 700mm by the present Example 1 and a flamelet approximation model.

  Hereinafter, an embodiment of a combustion flow numerical analysis program and a combustion flow numerical analysis method according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a computer 1 provided with a combustion flow numerical analysis program 1a in the present embodiment.

  The computer 1 in this embodiment is mainly composed of an input unit 2, a display unit 3, a storage unit 4 and an arithmetic processing unit 5. Hereinafter, each configuration will be described in detail.

  The input means 2 includes an operation key for inputting text and numerical values, an operation mouse, and the like. In the present embodiment, it can be used for input operations of numerical values such as initial conditions and setting conditions used when executing the combustion flow numerical analysis program 1a.

  The display means 3 is composed of a liquid crystal display, a CRT display, a touch panel, etc. for displaying images and text data, and can display the contents inputted by the input means, analysis results, etc. as a user interface in the combustion flow numerical analysis program 1a. It has become.

  The storage unit 4 includes a ROM (Read Only Memory), a RAM (Random Access Memory), a hard disk, a flash memory, and the like. The storage unit 4 stores various data and a working area when the arithmetic processing unit 5 performs an operation. It functions as.

  In the present embodiment, as shown in FIG. 1, the storage unit 4 is obtained mainly by a program storage unit 41 that stores the combustion flow numerical analysis program 1 a and a chemical reaction condition database creation unit 6 of the arithmetic processing unit 5 described later. A chemical reaction condition database 42 for storing the chemical reaction conditions, and a physical property value database 43 for storing physical property values measured in advance by experiments or theoretically obtained physical property values.

  The arithmetic processing means 5 is composed of a CPU (Central Processing Unit) or the like, and creates a chemical reaction condition database as shown in FIG. 1 by executing a combustion flow numerical analysis program 1a installed in the storage means 4. The computer 1 is made to function as means 6, instantaneous / locally stored scalar variable acquisition means 7, instantaneous / local chemical reaction condition calculation means 8, instantaneous / local physical property value calculation means 9, and combustion flow analysis means 10. Hereinafter, each component of the arithmetic processing means 5 will be described in more detail.

  The chemical reaction condition database creation means 6 uses a plurality of stored scalar variables set based on each chemical composition in the fuel, the oxidant, and the combustion mixture in which they are mixed, and uses the temperature, density, and chemistry for the stored scalar variables. A chemical reaction condition consisting of the seed fraction is acquired, and the chemical reaction condition is stored in the chemical reaction condition database 42. In the present embodiment, as shown in FIG. 1, a storage scalar variable setting unit 61, a variable value combination setting unit 62, a chemical reaction condition acquisition unit 63, and a database creation unit 64 are configured.

The storage scalar variable setting unit 61 sets four types of storage scalar variables. In the present embodiment, the mass fraction ratio scalar variable ξ, the enthalpy piece color variable ξ _h , the fuel composition scalar variable ξ _f, and the oxidant composition scalar variable ξ _o are set as the storage scalar variables. These conservative scalar variables include hydrogen fuel (H ₂ ) and / or hydrocarbon-based fuel (C _n H _m ) fuel, oxygen (O ₂ ) and / or air (O ₂ + N ₂ + trace amounts of inert rare). When combustion with an oxidant of gas) is set as a target, the mass conservation laws of hydrogen H, carbon C, oxygen O, and nitrogen N and the conservation law of total enthalpy are established. .

The mass fraction ratio scalar variable ξ is set based on the carbon C mass conservation law, and the mass fraction Z _{f of the} carbon C contained in the fuel and the mass fraction Z _{o of the} carbon C contained in the oxidant. And the ratio of the mass fraction Z of carbon C contained in the combustion mixture is expressed by the following formula (1).
... Formula (1)
Further, the equation of motion of the mass fraction ratio scalar variable ξ is expressed by the following equation (2).
... Formula (2)

  The mass fraction ratio scalar variable ξ is the same as the conserved scalar variable used in the framelet approximation model.

Further, the enthalpy scalar variable xi] _h is intended to be set on the basis of the conservation law of total enthalpy, the ratio of the total enthalpy h _f of the fuel, and the total enthalpy h _o of the oxidizing agent, the total enthalpy h of combustion mixture Is represented by the following equation (3).
... Formula (3)
The equation of motion of the enthal piece color variable ξ _h is expressed by the following equation (4).
... Formula (4)

Further, the fuel composition scalar variable ξ _f is set based on the law of conservation of mass of carbon C and hydrogen H contained in the fuel, and depends on the mass ratio of carbon C and hydrogen H contained in the fuel or combustion mixture. It is represented by the following formula (5).
... Formula (5)
The equation of motion of the fuel composition scalar variable ξ _f is expressed by the following equation (6).
... Formula (6)

The oxidant composition scalar variable ξ _o is set based on the law of conservation of mass of oxygen O and nitrogen N contained in the oxidant, and the mass of oxygen O and nitrogen N contained in the oxidant or combustion mixture. Depending on the ratio, it is expressed by the following equation (7).
... Formula (7)
Further, the equation of motion of the oxidant composition scalar variable ξ _o is expressed by the following equation (8).
... Formula (8)

  In Expressions (2), (4), (6), and (8), μ represents the viscosity coefficient, Sc represents the Schmitt number, and Pr represents the Prandtl number.

The variable value combination setting unit 62 is for setting an arbitrary combination based on the values of predetermined two types of stored scalar variables among the four types of stored scalar variables set by the stored scalar variable setting unit 61. In this embodiment, a fuel composition scalar variable ξ _f and an oxidant composition scalar variable ξ _o are used. Arbitrary combinations are set within the range of the value of the conserved scalar variable assumed within the range of the combustion conditions. For example, as shown in FIG. 2, by setting the fuel and the type of oxidizing agent used and the combustion field, a _n is set in the range a ₁ of the value of the fuel composition scalar variable xi] _f envisaged.

Therefore, the variable value combinations set unit 62 in the present embodiment, as shown in FIG. 3, to divide the a _n to a suitable distance from the value a ₁ of the fuel composition scalar variable xi] _f which are contemplated within the scope of the combustion conditions together, they are set any combination by dividing the value a ₁ of the are contemplated within the scope of the combustion conditions oxidant composition scalar variable xi] _o the a _m the appropriate intervals.

The chemical reaction condition acquisition unit 63 acquires the chemical reaction condition in each combination of the two types of stored scalar variables set by the variable value combination setting unit 62 by polynomial approximation of the other two types of stored scalar variables. . Therefore, in this embodiment, so as to obtain a chemical reaction conditions by polynomial approximation of the mass fraction ratio scalar variables xi] and enthalpy scalar variable xi] _h.

Specifically, for the combination of the value A ₁ from the value a ₁ of the set fuel composition scalar variable xi] _f a _n and oxidant composition scalar variable xi] _o and A _m by the variable value combinations setter 62 The mass fraction ratio scalar variable ξ and the enthalpy piece color variable ξ _h are slightly changed within the range of the respective combustion conditions, and the chemical reaction condition is changed to 2 of the mass fraction ratio scalar variable ξ and the enthalpiece color variable ξ _h . It is approximated by a variable polynomial.

  The database creation unit 64 stores the chemical reaction conditions for each combination acquired by the chemical reaction condition acquisition unit 63 in the chemical reaction condition database 42 of the storage unit 4.

  When calculation of the viscosity coefficient μ, Schmidt number Sc, and Prandtl number Pr is not necessary, or when calculation of the mass of the chemical species to be predicted is not required, acquisition of the chemical species fraction among the chemical reaction conditions and Storage in the chemical reaction condition database 42 can be omitted.

  Next, the instantaneous / local stored scalar variable acquisition means 7, the instantaneous / local chemical reaction condition calculation means 8, the instantaneous / local physical property value calculation means 9, and the combustion flow analysis means 10 will be described. These means are for numerical analysis of the flow accompanied by combustion using the chemical reaction conditions of the chemical reaction condition database 42 created by the chemical reaction condition database creation means 6.

  First, the instantaneous / locally stored scalar variable acquisition means 7 uses the equation of motion of the stored scalar variable, Equation (2), Equation (4), Equation (6), and Equation (8) to calculate the instantaneous / locally stored scalar variable. It is obtained by numerical analysis.

In this embodiment, Equation (6), which is the equation of motion of the fuel composition scalar variable ξ _f , and Equation (8), which is the equation of motion of the oxidizer composition scalar variable ξ _o , are combined to obtain a numerical solution. Thus, the instantaneous and local fuel composition scalar variable ξ _f and the instantaneous and local oxidant composition scalar variable ξ _o are obtained.

  The instantaneous / local chemical reaction condition calculation means 8 calculates the instantaneous / local chemical reaction condition using the chemical reaction condition stored in the chemical reaction condition database 42 and the instantaneous / local stored scalar variable.

For example, as shown in FIG. 4, the combination of the instantaneous and local fuel composition scalar variable ξ _f and the instantaneous and local oxidant composition scalar variable ξ _o acquired by the instantaneous / locally stored scalar variable acquisition means 7 is (a _x , A _x ), four combinations of the fuel composition scalar variable ξ _f and the oxidant composition scalar variable ξ _o stored in the chemical reaction condition database 42 adjacent to the combination (a _x , A _x ) (a _y , A _z ), (a _y , A _{z + 1} ), (a _{y + 1} , A _z ), (a _{y + 1} , A _{z + 1} ) are obtained, and the difference between the four combinations and the instantaneous / local combination The instantaneous and local chemical reaction conditions are calculated from the above.

  Note that the method for calculating the instantaneous / local chemical reaction condition for the instantaneous / locally stored scalar variable acquired by the instantaneous / locally stored scalar variable acquiring means 7 is not limited to the above-described one. The chemical reaction condition in the combination of the conserved scalar variables closest to the local conserved scalar variable may be the instantaneous / local chemical condition.

  The instantaneous / local physical property value calculating means 9 calculates an instantaneous / local physical property value using the instantaneous / local chemical reaction condition calculated by the instantaneous / local chemical reaction condition calculating means 8 and a predetermined physical property value.

  In the present embodiment, physical property values acquired in advance by experiments, theoretical calculations, etc. are stored in the physical property value database 43 of the storage means 4, and instantaneous / local chemical reaction conditions, that is, instantaneous and local temperature, instantaneous and local The physical property values necessary for the numerical analysis of the flow such as the viscosity coefficient μ, the Schmidt number Sc, and the Prandtl number Pr at the density and the instantaneous and local chemical fraction are obtained from the physical property database 43, and the instantaneous and local physical property values are obtained. Is calculated.

  The combustion flow analyzing means 10 numerically analyzes the flow accompanied by combustion of the fuel, the oxidant, and the combustion mixture using the instantaneous / local chemical reaction conditions and the instantaneous / local physical property values.

  In the present embodiment, a large eddy simulation method is used as an analysis method for analyzing a flow. This large eddy simulation method is a simulation based on a turbulent flow model in which turbulent vortices are spatially averaged. Note that the equations of motion of Equation (2), Equation (4), Equation (6), and Equation (8) are all given in a conserved form that does not have a generation term. The unified equations can be derived uniformly and easily, and high approximation accuracy can be obtained.

Equations obtained by spatially averaging Equations (2), (4), (6), and (8) are derived as follows.
... Formula (2 ')
... Formula (4 ')
... Formula (6 ')
... Formula (8 ')

  Here, the superscript-represents the spatial average, the superscript ~ represents the spatial fable average (also referred to as “density weight average”), and the subscript SGS represents the subgrid scale model constant representing the fluctuation effect below the spatial average. ing.

  In this embodiment, the flow is calculated by numerically analyzing the above equations (2 ′), (4 ′), (6 ′), and (8 ′) based on the large eddy simulation method. ing.

  The combustion flow analyzing means 10 is not limited to the one based on the large eddy simulation method, but a method for directly solving the Navier-Stokes equation without using a model, a method using another model such as a Reynolds average model, etc. Can be appropriately selected.

  Next, the operation of each component in the combustion flow numerical analysis program 1a of this embodiment and the combustion flow numerical analysis method will be described with reference to a functional block diagram showing the function of each component shown in FIG. 5 and a flowchart shown in FIG. .

  As shown in FIG. 5, first, the chemical reaction condition database creation means 6 obtains the chemical reaction conditions by a mathematical analysis using the stored scalar variables and stores them in the storage means 4 to create the chemical reaction condition database 42. (Step S1). Hereinafter, the creation procedure of the chemical reaction condition database 42 by the chemical reaction condition database creation means 6 in the present embodiment will be described with reference to FIG.

The stored scalar variable setting unit 61 of the chemical reaction condition database creation means 6 includes a mass fraction ratio scalar variable ξ shown in equation (1), an enthalpy piece color variable ξ _h shown in equation (3), and a fuel composition shown in equation (5). Four types of stored scalar variables are set, the scalar variable ξ _f and the oxidant composition scalar variable ξ _o shown in equation (7) (step S11).

Next, the variable combination setting unit 62 sets an arbitrary combination of the values of the two types of stored scalar variables, the fuel composition scalar variable ξ _f and the oxidant composition scalar variable ξ _o (step S12). Specifically, as shown in FIG. 3, based on the combustion conditions, as well as divide a _n from a ₁ assumable as the value of the fuel composition scalar variable xi] _f, assuming the value of the oxidizing agent composition scalar variable xi] _o The possible A ₁ to _Am are divided and set as a combination thereof.

Next, a reaction comprising temperature, density, and chemical species fraction in each combination of the fuel composition scalar variable ξ _f and the oxidant composition scalar variable ξ _o set by the variable value combination setting unit 62 by the chemical reaction condition acquisition unit 63. The condition is acquired by polynomial approximation of the other two types of stored scalar variables, the mass fraction ratio scalar variable ξ and the enthalpy piece color variable ξ _h (step S13).

And the database preparation part 64 memorize | stores the chemical reaction condition in each combination acquired by the said chemical reaction condition acquisition part 63 in the chemical reaction condition database 42 of the memory | storage means 4 (step S14). When the creation of the chemical reaction condition database for each combination of the fuel composition scalar variable ξ _f and the oxidant composition scalar variable ξ _o is completed, the process proceeds to the next step (return).

The instantaneous / locally stored scalar variable acquisition means 7 combines the equations of motion of the fuel composition scalar variable ξ _f and the oxidant composition scalar variable ξ _o and obtains a numerical solution thereof, thereby obtaining an instantaneous and local fuel composition scalar variable. ξ _f and an instantaneous and local oxidant composition scalar variable ξ _o are acquired (step S2).

Then, as shown in FIG. 5, the instantaneous / local chemical reaction condition calculation means 8 receives the instantaneous and local fuel composition scalar variable ξ _f and the instantaneous and local oxidant composition scalar variable from the instantaneous / local storage scalar variable acquisition means 7. ξ _o is acquired, and the chemical reaction conditions of the combination of the fuel composition scalar variable ξ _f and the oxidant composition scalar variable ξ _{o close to} the combination of the instantaneous and locally stored scalar variables are read from the chemical reaction condition database 42 and read. Instantaneous / local chemical reaction conditions are calculated based on the chemical reaction conditions that have been issued (step S3).

  Next, the instantaneous / local physical property value calculating means 9 acquires the instantaneous / local chemical reaction condition from the instantaneous / local chemical reaction condition calculating means 8 as shown in FIG. The approximate physical property value is read from the physical property value database 43, and the instantaneous / local physical property value is calculated (step S4). In the present embodiment, the viscosity coefficient μ, the Schmidt number Sc, and the Prandtl number Pr based on the instantaneous / local temperature, density, and chemical species fraction are calculated.

  As shown in FIG. 5, the combustion flow analyzing means 10 acquires the instantaneous / local chemical reaction conditions from the instantaneous / local chemical reaction condition calculating means 8, and the instantaneous / local physical property value calculating means 9 to obtain the instantaneous / local physical reaction conditions. Get the value. Then, using the obtained instantaneous / local chemical reaction conditions and instantaneous / local physical property values, the above formula (2 ′), formula (4 ′), formula (6 ′) and formula (8 ′), -Numerically analyze the flow accompanied by combustion by the simulation method (step S5).

According to the combustion flow numerical analysis program 1a and the combustion flow numerical analysis method of the present embodiment as described above, the following effects can be obtained.
1. Since the assumption of adiabatic conditions and the assumption of Lewis number are not required, the numerical analysis of the flow with combustion closer to the actual machine can be performed.
2. Numerical analysis of flows involving combustion with multiple fuels and / or multiple oxidants is possible.
3. The initial temperature in the fuel supply source can be set to a plurality of temperatures, and the initial temperature in the oxidant supply source can also be set to a plurality of temperatures.
4). Since the chemical reaction and flow calculation can be performed separately, the calculation load can be reduced.
5. By using the large eddy simulation method, it is possible to cope with a turbulent combustion flow.

  In Example 1, the predetermined analysis object was analyzed using the combustion flow numerical analysis program 1a and the combustion flow numerical analysis method according to the present invention. In addition, the “framelet approximation model” used in the conventional combustion flow analysis is used to analyze the analysis target under substantially the same conditions as the analysis target, and the combustion flow numerical analysis program 1a and the combustion flow numerical analysis according to the present invention are analyzed. The effectiveness of the method was investigated. Each analysis condition and analysis result will be described below.

(1) “Analysis target”
The analysis target in the first embodiment is a combustion flow field in a triple diffusion burner. FIG. 8 is a perspective view showing a combustion flow field as an analysis target in the first embodiment. FIG. 9 is an enlarged view showing a triple diffusion burner portion provided at one end of the combustion flow field to be analyzed.

  As shown in FIG. 8, the combustion flow field was a cylinder having a diameter of 600 mm and an X-axis direction of 700 mm. As shown in FIG. 9, the triple diffusion burner according to the first embodiment includes a central inner pipe, a middle pipe provided on the outer periphery of the inner pipe, and a middle pipe as an outlet for fuel and oxidant. The outer pipe is provided on the outer periphery of the pipe, and the outer diameter of the outer pipe is 23.9 mm.

(2) “Analysis conditions”
In the present Example 1, the case where the mixed gas of 1 type of fuel and 2 types of oxidizing agents burns was analyzed. The fuel and oxidant inflow conditions in Example 1 are summarized in Table 1 below.

As shown in Table 1, from the inner pipe, an oxidizer made of pure oxygen flows into the combustion flow field at an inflow speed of 35.4 m / s. Further, from the middle pipe, fuel in which propane (C ₃ H ₈ ) and butane (C ₄ H ₁₀ ) are mixed at a mass ratio of 1: 1 is in the combustion flow field at an inflow rate of 41.04 m / s. Is flowing in. Further, from the outer pipe, an oxidant composed of air flows into the combustion flow field at an inflow speed of 9.77 m / s. The temperature at the time of inflow of fuel and each oxidant was set to 300.15K. Furthermore, the pressure of the combustion flow field was atmospheric pressure.

Further, in the analysis using the “framelet approximate model”, only one type of fuel and oxidant can be handled, so a mixture of pure oxygen and air was used as the oxidant. The fuel and oxidant inflow conditions in the analysis using the “framelet approximate model” are summarized in Table 2.

  The oxidant flowing from the inner pipe and the outer pipe is a mixture in which pure oxygen and air are in a mass ratio of 78:22 so that the mass flow rates of pure oxygen and air, which are the oxidants of the first embodiment, are equal. I was worried.

(3) “Analysis results”
Hereinafter, the analysis result of the analysis using the first embodiment and the “framelet approximate model” will be described.

(3-1) Creation of chemical reaction condition database First, a chemical reaction condition database was created. The four conserved scalar variables used to create the chemical reaction condition database are a mass fraction ratio scalar variable ξ, an enthalpy piece color variable ξ _h , a fuel composition scalar variable ξ _f, and an oxidant composition scalar variable ξ _o . In the variable value combination setting unit 62 of the first embodiment, among these stored scalar variables, two types of mass fraction ratio scalar variable ξ and oxidant composition scalar variable ξ _o are set as combinations.

Here, the oxidizing agent composition scalar variable xi] _o, air, the mass fraction of oxygen atoms in the oxygen and air mixture Z _{O, Air,} an analysis redefine the following equation using the _{Z O, O2} and Z _O went.
... Formula (9)

Further, as shown in Table 1, the value of the oxidant composition scalar variable ξ _o in Example 1 is 0 for fuel flowing from the middle pipe and 1 for oxidant flowing from the inner pipe. Therefore, the value of the oxidant composition scalar variable ξ _o assumed within the range of the combustion conditions in Example 1 is in the range of 0 to 1, and 11 tables are created in increments of 0.1. Further, the density between the 11 tables was calculated by linear interpolation.

FIG. 10 is a graph showing the results of analyzing the density for a combination of two conserved scalar variables, a mass fraction ratio scalar variable ξ and an oxidant composition scalar variable ξ _o .

Regarding the chemical reaction condition database used for the analysis of the flamelet approximate model, as shown in Table 2 above, the amount of oxygen in the oxidant is 78% by mass, and therefore the oxidant composition scalar variable ξ _o in FIG. This corresponds to the 0.78 portion, and this value was used.

(3-2) Analysis of combustion flow Next, the combustion flow in the combustion flow field was analyzed by an analysis method based on the large eddy simulation method using the chemical reaction condition database created in (3-1). Note that the Euler implicit method is used for the time integration method, and the advection term diffusion scheme of the equation of motion is a linear precision center difference and a first precision upwind difference, each in a ratio of 95: 5. A coupling scheme was used. The upwind difference with first order accuracy was used for the advection term diffusion scheme of the scalar transport equation. Furthermore, the time step width was set to 1.5 × 10 ⁻⁵ sec / step.

  FIG. 11 is a time-average distribution of the mass fraction ratio scalar variable ξ in the XY cross section in FIG. The whiter the color, the higher the mass fraction of carbon atoms and the greater the amount of carbon. In the first embodiment, fuel is injected from the middle pipe. From FIG. 11, two white stripes can be seen. Further, the white color is dark in the vicinity of the inflow port, and the color becomes lighter as the distance from the inflow port increases. This indicates that the fuel is thick in the vicinity of the inlet, and diffuses as it moves away from the inlet.

FIG. 12 is a time average distribution of the oxidant composition scalar variable ξ _{o in} the XY cross section. The whiter the color, the higher the mass fraction of oxygen atoms and the greater the amount of oxygen. From FIG. 12, it can be seen that the oxidant shows a high value in the vicinity of the inlet and diffuses away from the inlet. In particular, in the first embodiment, since pure oxygen is injected from the inner pipe, it can be seen that an oxidant having a high oxygen amount is injected from the center.

  FIG. 13 is a time-averaged distribution of temperature in the XY cross section. The whiter the color, the higher the temperature, indicating that a combustion reaction is taking place. From FIG. 13, the double pipe is formed by mixing the oxidizer of the inner pipe and the fuel of the middle pipe and mixing the oxidizer of the outer pipe and the fuel of the middle pipe. I can see it.

  Further, in the first embodiment, since the oxidant supplied from the inner pipe is pure oxygen, the inner flame of the double flame is hot and burns intensely. It can also be seen that the inner and outer flames diffuse as they move away from the inlet and the temperature gradually decreases. The above results can be said to be close to the actual phenomenon in which the flame is gradually cooled by the outside air and the temperature is lowered.

(3-3) Comparison with Analysis Result by Framelet Approximation Model Next, an attempt was made to compare with an analysis result by the framelet approximation model. FIG. 14 is a time average distribution of the mass fraction ratio scalar variable ξ in the XY cross section analyzed by the flamelet approximate model. The whiter the color, the higher the mass fraction of carbon atoms and the greater the amount of carbon. Compared with FIG. 11, which is the time-average distribution of the mass fraction ratio scalar variable ξ in Example 1, the fuel shows a high value in the vicinity of the inlet, and the tendency to diffuse as it moves away from the inlet is the same. The distribution of the mass fraction ratio scalar variable ξ at each position was almost equal. As shown in Table 1 and Table 2 above, it is considered that such a result is obtained because the type of fuel flowing in from the middle pipe and the inflow speed are equal.

  On the other hand, regarding the temperature distribution, a difference appeared between the analysis result in the first embodiment and the analysis result by the flamelet approximation model. FIG. 15 is a time-averaged temperature distribution in the XY cross section analyzed by the flamelet approximate model. Compared with FIG. 13, the temperature analyzed by the flamelet approximation model can be seen that a double flame is formed as in the analysis result of the first embodiment. It can be seen that the temperature is kept high and not very diffuse.

  Therefore, in order to compare the temperature distribution in detail, the time average temperature distribution on the Y axis was also compared. FIG. 16 shows the time-average temperature distribution on the Y-axis at the position of X = 100 mm. The analysis result of the first embodiment is shown by the solid line, and the analysis of the flamelet approximate model is shown by the alternate long and short dash line. It is a result. As described above, the diameter of the outer pipe is 23.9 mm, and the position where X = 100 mm corresponds to a place about four times the diameter of the outer pipe.

  As shown in FIG. 16, the analysis result of the first embodiment and the analysis result of the framelet approximation model are common in that a) the temperature near the center is low, and b) the two high-temperature portions are approximately symmetrical. To do. Regarding a), the oxidant flowing from the inner pipe and the fuel flowing from the middle pipe are not sufficiently mixed in the vicinity of the center, and the fuel is not combusted. As for b), there are locations where the fuel is mixed with the oxidant flowing from the inner pipe and burning, and locations where the fuel is mixed with the oxidant flowing from the outer pipe and burning. It has appeared.

  On the other hand, with respect to the two high-temperature locations in the left-right substantially symmetrical manner of 2), in the first embodiment, the inner pipe side is hot and the outer pipe side is cold, whereas in the flamelet approximation model, the inner pipe side and the outer pipe side Are approximately the same temperature. In the first embodiment, fuel and pure oxygen are mixed on the inner pipe side, so that combustion is intensely hot, and fuel and air are mixed on the outer pipe side, so that the temperature is relatively low. Seem. On the other hand, in the flamelet approximation model, only one kind of oxidant can be handled. Therefore, the oxidants on the inner pipe side and the outer pipe side are the same, and it is considered that the temperatures are almost the same.

  17 to 19 are time average temperature distributions on the Y-axis at positions of X = 300 mm, X = 500 mm, and X = 700 mm, respectively.

  In Example 1, it can be seen that as the distance from the inflow port increases, the temperature distribution becomes uniform and the temperature gradually diffuses. Then, at the position of X = 700 mm, the temperature distribution has a gentle convex shape that is substantially axially symmetric, and the influence of the central oxidant is not observed. As described above, the diffusion of the temperature occurs when the flame is gradually cooled by the outside air. Therefore, it is considered that the analysis result according to the first embodiment shows a distribution close to the actual phenomenon.

  On the other hand, in the flamelet approximate model, as in the first embodiment, as the distance from the inflow port increases, diffusion and uniformization of the temperature distribution proceeds, but the speed is slower than that in the first embodiment. For example, at the position of X = 700 mm, a low temperature portion remains at the center due to the influence of the oxidizing agent, and the convex temperature distribution has a large gradient. This is because, in the flamelet approximation model, the Lewis number is assumed to be 1 so that the diffusion coefficient of the chemical species and the enthalpy are approximately the same, so that the diffusion of substances and temperatures is suppressed compared to the actual phenomenon. it is conceivable that.

(4) Summary With the combustion flow numerical analysis program 1a and the combustion flow numerical analysis method according to the present invention, it was possible to analyze the combustion flow using a plurality of oxidants. Therefore, it can be said that the range of use has become much wider than that of the flamelet approximation model in which only one kind of oxidant can be used.

  Further, even if the analysis results are compared, an analysis result closer to the actual phenomenon is obtained than the analysis result using the conventional flamelet approximation model, and it can be said that it is advantageous in terms of analysis accuracy.

  The combustion flow numerical analysis program 1a and the combustion flow numerical analysis method according to the present invention are not limited to the above-described embodiment, and can be changed as appropriate.

  For example, the combustion flow numerical analysis program 1a and the combustion flow numerical analysis method according to the present invention may be configured in combination with an existing flamelet approximate model. In the case of the premixed flame, a scalar variable based on the premixed flame may be added separately from the stored scalar variable, and the numerical analysis of the combustion flow may be performed.

DESCRIPTION OF SYMBOLS 1 Computer 1a Combustion flow numerical analysis program 2 Input means 3 Display means 4 Storage means 5 Arithmetic processing means 6 Chemical reaction condition database preparation means 7 Instantaneous / local storage scalar variable acquisition means 8 Instantaneous / local chemical reaction condition calculation means 9 Instantaneous / local Physical property value calculation means 10 Combustion flow analysis means 41 Program storage unit 42 Chemical reaction condition database 43 Physical property value database 61 Stored scalar variable setting unit 62 Variable value combination setting unit 63 Chemical reaction condition acquisition unit 64 Database creation unit

Claims (5)

A combustion flow numerical analysis program for numerically analyzing a flow accompanied by combustion of hydrogen fuel and / or hydrocarbon fuel and oxidant,
Numerical analysis of chemical reaction conditions during combustion using a predetermined stored scalar variable among a plurality of stored scalar variables set based on each chemical composition in the fuel, the oxidizer, and a combustion mixture obtained by mixing them. And a chemical reaction condition database creating means for storing the chemical reaction condition in the chemical reaction condition database,
Instantaneous / locally stored scalar variable acquisition means for acquiring an instantaneous / locally stored scalar variable by numerical analysis using the equation of motion of the stored scalar variable;
Instantaneous / local chemical reaction condition calculating means for calculating an instantaneous / local chemical reaction condition using the chemical reaction condition stored in the chemical reaction condition database and the instantaneous / locally stored scalar variable;
Instantaneous / local physical property value calculating means for calculating the instantaneous / local physical property value using the instantaneous / local chemical reaction conditions and the predetermined physical property value;
Combustion flow that causes a computer to function as combustion flow analysis means for numerically analyzing the flow accompanied by combustion of the fuel, the oxidant, and the combustion mixture using the instantaneous / local chemical reaction conditions and the instantaneous / local physical property values Numerical analysis program.   The chemical reaction condition database creation means sets a stored scalar variable setting unit for setting four types of stored scalar variables, and an arbitrary combination based on values of two predetermined stored scalar variables among the four types of stored scalar variables A variable value combination setting unit to perform, a chemical reaction condition acquisition unit to acquire the chemical reaction condition in the combination by polynomial approximation of the other two types of stored scalar variables, and the acquired chemical reaction condition to the chemical reaction condition database The combustion flow numerical analysis program according to claim 1, which causes a computer to function as a database creation unit to be stored in the combustion flow.   A mass fraction ratio scalar variable set based on a mass fraction ratio of carbon contained in the fuel, the oxidant and the combustion mixture; and the fuel, the oxidant and the combustion mixture. An enthalpy piece color variable set based on a gas enthalpy ratio, a fuel composition scalar variable set based on a mass ratio of hydrogen and carbon contained in the fuel or the combustion mixture, and the oxidant or the combustion mixture The combustion flow numerical analysis program according to claim 1 or 2, wherein the combustion flow numerical analysis program is an oxidant composition scalar variable set based on a mass ratio of oxygen and nitrogen contained in the atmosphere.   The combustion flow numerical analysis program according to any one of claims 1 to 3, wherein the combustion flow analysis means is analysis means based on a large eddy simulation method. A combustion flow numerical analysis method for numerically analyzing a flow accompanying combustion of hydrogen fuel and / or hydrocarbon fuel and oxidant,
Numerical analysis of chemical reaction conditions during combustion using a predetermined stored scalar variable among a plurality of stored scalar variables set based on each chemical composition in the fuel, the oxidizer, and a combustion mixture obtained by mixing them. A chemical reaction condition database creation step for acquiring the chemical reaction condition and storing the chemical reaction condition in the chemical reaction condition database;
Instantaneous / locally stored scalar variable acquisition step of acquiring the instantaneous / locally stored scalar variable by numerical analysis using the equation of motion of the stored scalar variable;
Instantaneous / local chemical reaction condition calculating step for calculating instantaneous / local chemical reaction conditions using the chemical reaction conditions stored in the chemical reaction condition database and the instantaneous / locally stored scalar variable;
Instantaneous / local physical property value calculating step for calculating the instantaneous / local physical property value using the instantaneous / local chemical reaction conditions and the predetermined physical property value;
A combustion flow numerical analysis method comprising: a combustion flow analysis step for numerically analyzing a flow accompanying combustion of the fuel, the oxidant and the combustion mixture using the instantaneous / local chemical reaction conditions and the instantaneous / local physical property values.