JP2017203560A - Combustion flow numerical analysis program and combustion flow numerical analysis method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion flow numerical analysis program and a combustion flow numerical analysis method that can be applied to a numerical analysis in which a combustion chemical reaction is non-equilibrium state and that can restrict an increasing in a calculation load accompanied with the application.SOLUTION: This invention comprises a chemical reaction condition data base making means 6 for storing chemical reaction conditions including a temperature at a thermal equilibrium state, a density at the thermal equilibrium state, and a mass burning rate under a thermal equilibrium state to a chemical reaction condition data base 42, using a prescribed conserved scalar quantity; an instantaneous and local conserved scalar quantity taking means 7 for acquiring an instantaneous and local conserved scalar quantity; an instantaneous and local chemical reaction condition calculation means 8 for calculating the instantaneous and local chemical reaction condition; an instantaneous and local physical property value calculation means 9 for calculating instantaneous and local physical property value using a conservation equation of an index scalar quantity and instantaneous and local chemical reaction condition; and a combustion flow analysis means 10 for numerically analyzing a flow accompanied with combustion of fuel, oxidant, and combustion mixture.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a combustion flow numerical analysis program and a combustion flow numerical analysis method for numerically analyzing a flow accompanied by combustion of a fuel and an 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. For this reason, although the chemical reaction process has been studied in detail, it has been pointed out that it is difficult to simultaneously analyze various multistage chemical reactions such as combustion flows and flows.

  Conventionally, numerical analysis of chemical reaction and numerical analysis of flow are separately performed for such problems by separating the numerical analysis of the chemical reaction and the numerical analysis of the flow by using a stored scalar quantity that represents the diffusive mixing of the combustion mixture of fuel and oxidant. There is a method called flamelet approach. However, this flamelet approach assumes a combustion reaction state with only one kind of stored scalar quantity, lacks versatility with respect to various fuels, or changes in flow and thermal conditions, and its application range and analysis accuracy are the principle. Limited.

  So far, the inventors of the present application have solved the problem of application range and analysis accuracy in the flamelet approach so that an efficient and highly accurate numerical solution can be obtained by using a plurality of stored scalar quantities. An invention related to a flow numerical analysis program and a combustion flow numerical analysis method has been proposed, and a patent right has been obtained (Patent Document 1).

Japanese Patent No. 5863109

  However, in the invention described in Patent Document 1, since it is assumed that the combustion chemical reaction is in an equilibrium state or a state close thereto, it is suitable for simulation in such a state. It cannot be applied to the numerical analysis of so-called non-equilibrium chemical reactions in which combustion proceeds little by little like a flow field.

  The present invention has been made in order to solve the problems related to the application limitation in the above patented invention, and can be applied to a numerical analysis in which the combustion chemical reaction is a combustion flow in a non-equilibrium state, and the calculation load associated therewith is also reduced. An object of the present invention is to provide a combustion flow numerical analysis program and a combustion flow numerical analysis method capable of suppressing the increase.

  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 fuel and an oxidant, and each of the fuel, the oxidant, and a combustion mixture obtained by mixing them. Among the plurality of stored scalar quantities set based on the chemical composition, using the predetermined stored scalar quantity, the chemical reaction conditions including the temperature in the thermal equilibrium state, the density in the thermal equilibrium state, and the mass burning rate are obtained by numerical analysis, Chemical reaction condition database creation means for storing the chemical reaction conditions in a chemical reaction condition database, and instantaneous / locally preserved scalar quantity acquisition means for obtaining an instantaneous / locally preserved scalar quantity by numerical analysis using the conservation equation of the preserved scalar quantity And the chemical reaction conditions stored in the chemical reaction condition database and the instantaneous and local storage Instantaneous / local chemical reaction condition calculating means for calculating instantaneous / local chemical reaction conditions using color quantities, an index scalar quantity conservation equation representing the non-equilibrium state of combustion reaction, and instantaneous using the instantaneous / local chemical reaction conditions -Instantaneous / local physical property value calculating means for calculating local physical property values, and the 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 A computer is made to function as a combustion flow analysis means for numerical analysis.

  A 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 a fuel and an oxidant, and each of the fuel, the oxidant, and a combustion mixture obtained by mixing them. Among the plurality of stored scalar quantities set based on the chemical composition, using the predetermined stored scalar quantity, the chemical reaction conditions including the temperature in the thermal equilibrium state, the density in the thermal equilibrium state, and the mass burning rate are obtained by numerical analysis, A chemical reaction condition database creation step for storing the chemical reaction conditions in a chemical reaction condition database, and an instantaneous / locally stored scalar quantity acquisition step for obtaining an instantaneous / locally stored scalar quantity by numerical analysis using the storage equation for the stored scalar quantity And the chemical reaction conditions stored in the chemical reaction condition database and the instantaneous / local storage scan -Instantaneous / local chemical reaction condition calculation step that calculates the instantaneous / local chemical reaction condition using the amount, and the conservation equation of the index scalar quantity that represents the non-equilibrium state of the combustion reaction and the instantaneous / local chemical reaction condition An instantaneous / local physical property value calculating step for calculating a local physical property value, and a flow accompanied by combustion of the fuel, the oxidant, and the combustion mixture using the instantaneous / local chemical reaction condition and the instantaneous / local physical property value. A combustion flow analysis step for numerical analysis.

  ADVANTAGE OF THE INVENTION According to this invention, while being applicable to the numerical analysis whose combustion chemical reaction is a combustion flow of a non-equilibrium state, the increase in the calculation load accompanying it can be suppressed.

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 quantity (xi) assumed. It is the schematic which shows the arbitrary combinations of two types of preservation | save scalar quantities set by the preservation | save scalar quantity 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 conceptual diagram which shows the premix combustion using the parameter | index scalar quantity G in 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 rectangular plate-shaped combustion flow field made into the analysis object in this Example 1. FIG. It is a three-dimensional graph which shows the database of the temperature in the thermal equilibrium state created by the chemical reaction condition database creation means of the present Example 1. It is the graph which looked at the three-dimensional graph shown in FIG. 10 in (xi) _c- axis direction. It is the graph which expanded a part of FIG. It is a three-dimensional graph which shows the database of the specific volume (reciprocal number of a density) in the thermal equilibrium state created by the chemical reaction condition database creation means of the present Example 1. It is the graph which looked at the three-dimensional graph shown in FIG. 13 in the ξ _c- axis direction. 3 is a three-dimensional graph showing a mass combustion rate database created by the chemical reaction condition database creation means of the first embodiment. FIG. 16 is a graph when the three-dimensional graph shown in FIG. 15 is viewed in the ξ _c- axis direction. It is a front view which shows the plot acquisition position of the Z-axis cross section in the combustion flow field of the present Example 1. FIG. It is a temperature distribution figure which shows the analysis result of the present Example 1. It is a temperature distribution figure in the plot acquisition position of the Z-axis cross section shown in FIG. It is a distribution map of the mass fraction ξ of the fuel in the air-fuel mixture showing the analysis result of the first embodiment. FIG. 18 is a distribution diagram of the mass fraction ξ of fuel in the air-fuel mixture at the plot acquisition position of the Z-axis cross section shown in FIG. 17. It is a distribution map of carbon ratio ξ _{c in} the fuel showing the analysis result of the first embodiment. FIG. 6 is a distribution diagram of an index scalar quantity G showing the analysis result of the first embodiment. FIG. 18 is a distribution diagram of the index scalar quantity G at the plot acquisition position of the Z-axis cross section shown in FIG. 17. 6 is an enlarged distribution diagram of an index scalar quantity G showing the analysis result of the first embodiment. FIG. It is a mass burning velocity distribution map which shows the analysis result of the present Example 1. It is a density distribution figure which shows the analysis result of the present Example 1. It is a density distribution figure in the plot acquisition position of the Z-axis cross section shown in FIG. It is a perspective view which shows the combustion flow field of the combustor made into the analysis object in this Example 2. FIG. It is a perspective view which shows the supply place of the fuel in this Example 2, and an oxidizing agent. It is the schematic which shows the data acquisition position and dimensionless coordinate of the cross-sectional plot in the present Example 2. It is a temperature distribution figure which shows the analysis result of the present Example 2. It is a temperature distribution figure in the data acquisition position of the cross-sectional plot shown in FIG. It is a mass burning rate distribution map which shows the analysis result of the present Example 2. It is a distribution map of carbon ratio ξ _{c in} the fuel showing the analysis result of the second embodiment. FIG. 10 is an enlarged distribution diagram of an index scalar quantity G showing the analysis result of the second embodiment.

  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.

  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 2 and analysis results 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. And a chemical reaction condition database 42 for storing the chemical reaction conditions.

  The program storage unit 41 is installed with the combustion flow numerical analysis program 1a of this embodiment. Then, the arithmetic processing means 5 executes the combustion flow numerical analysis program 1a, and causes the computer 1 and the like to function as constituent parts to be described later.

  In addition, the utilization form of the combustion flow numerical analysis program 1a is not restricted to the said structure. For example, the combustion flow numerical analysis program 1a may be stored in a non-transitory recording medium readable by the computer 1, such as a CD-ROM or a USB memory, and read directly from the recording medium and executed. . Moreover, you may utilize by a cloud computing system, ASP (application service provider) system, etc. from an external server.

  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 the means 6, the instantaneous / local storage scalar quantity 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. Hereinafter, each component of the arithmetic processing means 5 will be described.

  The chemical reaction condition database creation means 6 acquires chemical reaction conditions by using a plurality of stored scalar quantities set based on the respective chemical compositions in the fuel, the oxidant, and the combustion mixture obtained by mixing them, and the chemical reaction The conditions are stored in the chemical reaction condition database 42 of the storage means 4.

  The chemical reaction conditions in the present embodiment are such that instantaneous and local physical property values in the combustion field can be calculated based on the index scalar quantity G representing the non-equilibrium state of the combustion reaction in the instantaneous / local physical property value calculating means 9 described later. , Thermal equilibrium temperature, thermal equilibrium density and mass burning rate. The chemical reaction conditions are not limited to the temperature in the thermal equilibrium state, the density in the thermal equilibrium state, and the mass combustion rate, and may include a chemical species fraction and the like as necessary.

  As shown in FIG. 1, the chemical reaction condition database creation means 6 in this embodiment includes a stored scalar quantity setting unit 61, a saved scalar quantity combination setting unit 62, a chemical reaction condition acquisition unit 63, and a database creation unit 64. Have

The storage scalar amount setting unit 61 sets a plurality of storage scalar amounts. In the combustion reaction, carbon molecules and hydrogen molecules are generally oxidized and serve as fuel. Therefore, if carbon C and hydrogen H in the mixed gas are regarded as fuel, and oxygen O and nitrogen N are regarded as oxidants, the fuel and oxidant can be distinguished by elements rather than inflowing gas. Based on this idea, it is common to use the mass fraction ξ of the fuel in the gas mixture, the normalized enthalpy ξ _h of the gas mixture, the proportion of carbon in the fuel ξ _c , the proportion of oxygen in the oxidizer ξ _o A flame structure.

Therefore, in the present embodiment, as the stored scalar quantity, the fuel mass fraction ξ in the gas mixture, the normalized enthalpy ξ _h of the gas mixture, the carbon ratio ξ _c , and the oxygen ratio ξ _o in the oxidant Is set. Hereinafter, each storage scalar amount will be described.

The mass fraction ξ of the fuel in the mixture is set based on the law of conservation of mass of carbon C and hydrogen H contained in the fuel. The mass fraction Z _{C of} carbon C contained in the fuel and the fuel the sum of the mass fraction Z _H hydrogen H included, it is represented by the following formula (1).
... Formula (1)
When the fuel mass fraction ξ is replaced by ξ = Z _C + Z _H = Z, the conservation equation of the fuel mass fraction ξ is expressed by the following (2).
... Formula (2)

At this time, the mass fraction ξ of the fuel in the air-fuel mixture is defined within the range shown in the following equation (3).
... Formula (3)
As a result, the mass fraction ξ of the fuel in the air-fuel mixture is limited by the following formulas (4) and (5).
When
... Formula (4)
When
... Formula (5)

The normalized enthalpy ξ _h of the mixed gas is expressed by the following equation (6) that is made dimensionless by using the enthalpy reference values h _l and h _h (h _l > h _h ).
... Formula (6)
The simplified conservation equation of enthalpy h is expressed by the following equation (7).
... Formula (7)

At this time, assuming that the maximum value of the normalized enthalpy ξ _h of the mixed gas is ξ _{h, max} and the minimum value is ξ _{h, min} , the normalized enthalpy ξ _h of the mixed gas is within the range shown in the following equation (8). Defined.
... Formula (8)
Thereby, the normalization enthalpy ξ _h of the mixed gas is provided with the restrictions of the following expressions (9) and (10).
When
... Formula (9)
When
... Formula (10)

The carbon ratio ξ _c in the fuel is expressed by the following formula (11) as a ratio of the mass fraction ξ of the fuel in the air-fuel mixture and the mass fraction Z _c of the carbon C in the fuel.
... Formula (11)
Further, conservation equations carbon ratio Z _c in the fuel is represented by the following equation (12).
... Formula (12)

At this time, if the maximum value of the carbon ratio ξ _{c in} the fuel determined by the fuel composition is ξ _{c, max} and the minimum value is ξ _{c, min} , the carbon ratio ξ _c in the fuel is expressed by the following equation (13). Defined by range.
... Formula (13)
As a result, the carbon ratio ξ _c in the fuel is limited by the following equations (14) and (15).
When
... Formula (14)
When
... Formula (15)

The ratio ξ _o of oxygen in the oxidant is expressed as a ratio of Z _O + Z _N (= 1−ξ), which is the sum of the mass fractions of oxygen and nitrogen, which are oxidizers, and the mass fraction of oxygen, Z _O. It is represented by the following formula (16).
... Formula (16)
Further, the conservation equation of the mass fraction Z 2 _O of oxygen is expressed by the following equation (17).
... Formula (17)

At this time, assuming that the maximum value of the oxygen ratio ξ _O in the oxidizer determined by the fuel composition is ξ _{O, max} and the minimum value is ξ _{O, min} , the oxygen ratio ξ _o in the oxidizer is expressed by the following equation (18 ).
... Formula (18)
Thereby, the oxygen ratio ξ _o in the oxidizing agent is limited by the following formulas (19) and (20).
When
... Formula (19)
When
... Formula (20)

In Equation (2), Equation (7), Equation (12), and Equation (17), μ is the viscosity coefficient, σ _Z is the Schmitt number when the diffusion coefficient of each chemical species is assumed to be equal, Pr Represents the Prandtl number.

Next, the saved scalar quantity combination setting unit 62 is for setting an arbitrary combination based on a predetermined number of saved scalar quantity values among the plurality of saved scalar quantities set by the saved scalar quantity setting unit 61. is there. In the present embodiment, it is assumed that a fuel with different compositions composed of hydrogen H ₂ and methane CH ₄ flows from a plurality of fuel supply ports, and that each of these compositions changes over time. Therefore, the fuel mass fraction ξ in the air-fuel mixture set based on each chemical composition of the fuel and the carbon ratio ξ _c in the fuel are used.

Further, in the stored scalar quantity combination setting unit 62, any combination of the stored scalar quantities set in the present embodiment is an expression (3), an expression (8), an expression (13) assumed within the range of the combustion conditions. And a value within the range of the value of the stored scalar quantity represented by the equation (18). For example, as shown in FIG. 2, by setting the fuel and the type of oxidizing agent used and the combustion field, is a _n the range a ₁ of the value of the mass fraction ξ of the fuel in air mixture that is assumed Is set.

Therefore, saving scalar combination setting section 62 in the present embodiment, as shown in FIG. 3, suitably a a _n from the value a ₁ mass fraction ξ of the fuel in the air-fuel mixture are contemplated within the scope of the combustion conditions with divided into such interval is set to any combination by dividing the value a ₁ of the carbon percentage xi] _c in the fuel to be contemplated within the scope of the combustion conditions of a _m to the appropriate intervals.

  It should be noted that the combinations of the stored scalar quantities can be a plurality of combinations that are mathematically equivalent, and theoretically have no influence on the analysis result. Moreover, it is not limited to the combination of two types of storage scalar amounts, and three or more storage scalar amounts may be combined.

  The chemical reaction condition acquisition unit 63 acquires the chemical reaction condition in each combination of the storage scalar amounts set by the storage scalar amount combination setting unit 62 by numerical analysis.

In this embodiment, the value from the A ₁ A _m carbon ratio xi] _c of the storage scalar combination setting section 62 a _n and fuel from the values a ₁ mass fraction of the fuel in the air-fuel mixture which is set xi] by The dimensionless reaction calculation is performed based on the formulas (1) to (21) for the combination of the above, thereby obtaining the temperature in the thermal equilibrium state, the density in the thermal equilibrium state, and the mass burning rate, which are chemical reaction conditions.

  Then, the database creation unit 64 stores the temperature of the thermal equilibrium state, the density of the thermal equilibrium state, and the mass combustion rate, which are the chemical reaction conditions in each combination acquired by the chemical reaction condition acquisition unit 63, in the chemical reaction condition database 42 of the storage unit 4. To remember.

  Next, the instantaneous / locally stored scalar quantity acquisition means 7 uses the storage scalar quantity storage equation (2), (7), (12), and (17) to calculate the instantaneous / locally stored scalar quantity. Is obtained by numerical analysis.

In this embodiment, Equation (2), which is a conservation equation for the mass fraction ξ in fuel, and Equation (12), which is a conservation equation for the carbon fraction ξ _{c in} the fuel, are coupled and numerically solved. Is obtained, the instantaneous and local mass fraction ξ in the fuel and the instantaneous and local carbon fraction ξ _c are obtained.

  Next, 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 quantity. .

For example, as shown in FIG. 4, the combination of the instantaneous and local fuel mass fraction ξ acquired by the instantaneous / locally stored scalar quantity acquiring means 7 and the carbon fraction ξ _{c in} the instantaneous and local fuel is (a _x , A _x ), four combinations of the fuel mass fraction ξ and the carbon fraction ξ _{c in} the fuel stored in the chemical reaction condition database 42 close 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} ) chemical reaction conditions are acquired, and the difference between the four combinations and the instantaneous / local combination The instantaneous and local chemical reaction conditions are calculated from the above.

Thereby, the chemical reaction conditions, eg temperature, density and mass fraction, are expressed as the following equation (21) as a function of the instantaneous and local fuel mass fraction ξ and the carbon fraction ξ _{c in} the instantaneous and local fuel: Is represented by
,
,
... Formula (21)

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

  Further, the chemical reaction condition database creation means 6, the instantaneous / local stored scalar quantity acquisition means 7 and the instantaneous / local chemical reaction condition calculation means 8 in the present embodiment are the chemical reaction condition database creation means in the invention described in Patent Document 1. Since the same program code can be applied to the instantaneous / locally stored scalar variable acquisition means and the instantaneous / local chemical reaction condition calculation means, the versatility of the invention described in Patent Document 1 can be inherited.

  Next, the instantaneous / local physical property value calculating means 9 calculates the instantaneous / local physical property value using the conservation equation of the index scalar quantity representing the non-equilibrium state of the combustion reaction and the instantaneous / local chemical reaction condition. Hereinafter, the index scalar quantity will be described.

The index scalar quantity represents a non-equilibrium state of the combustion reaction. As shown in FIG. 5, the scalar amount in the present embodiment represents the state of the flame as an index scalar amount G, the position of the flame surface of the premixed flame is G = G ₀ = 0.5, and G> G ₀ already燃気side represents a non-equilibrium state defined by a combustion reaction with the G <G ₀ not燃気side. At this time, the index scalar quantity G is expressed by the following equation (22).
... Formula (22)
Here, T _u represents the unburned gas temperature, and T _b represents the burned gas temperature.

Further, the equation representing the movement behavior of the premixed flame front G = G ₀ as G equations are expressed by the following equation (23).
... Formula (23)
Here, [rho _u is the density of the non燃気body, S _L is the speed of moving from the non-燃側to already燃側premixed flame front by the consumption of premixed flame by combustion reaction, represents a so-called laminar burning velocity. Also, the left side second term of equation (23) represents the advection phenomena of the flame front by the flow of the premixed gas, the right side represents the flame propagation phenomenon flame by premixed combustion is moved in a laminar flow combustion speed S _L .

However, in this model premixed flame is present only in a very thin region of G = G _0, but the flame thickness is model defined as very thin, the actual flame with a thickness of a few millimeters the order Yes. Therefore, in the present embodiment, the following equation (24) considering the flame thickness is used as a conservation equation for the index scalar quantity G.
... Formula (24)
Here, C _p is a constant pressure specific heat. Further, a physical quantity S ^* is used instead of the laminar combustion speed S _L. This S ^* is a physical quantity called a local combustion speed having a distribution in the flame thickness, and is represented by the following equation (25).
... Formula (25)

In addition, the first-order approximation model of the index scalar quantity G is expressed by the following equation (26) that can be accurately established for different air-fuel ratios and preheating temperatures.
... Formula (26)

  Further, in the gas turbine combustor to be analyzed in Example 2 to be described later, diffusion combustion and premixed combustion are in a mixed state. Therefore, it is not appropriate to handle the diffusion combustion model according to the equations (1) to (21) and the premixed combustion model according to the equations (22) to (26) independently. Therefore, in this embodiment, a partially premixed combustion model in which two models are combined is used.

For the index scalar quantity G of the premixed combustion model, G = 0 is unburned and G = 1 is the burned parameter, and for the diffusion combustion model, the temperature, density, and chemical species α are related to the distribution of ξ and ξ _c . The mass fraction is given from the chemical reaction condition database 42. In addition, a combination of both unburned and burned states is assumed to be a linear combination with the simplest index scalar quantity G.

From the above, the mass fraction, temperature, and density expressed in the equation (21) by combining the two models are expressed by the following equations (27) to (29) as the harmonic average of the index scalar quantity G. The
... Formula (27)
... Formula (28)
... Formula (29)

  The instantaneous / local physical property value calculation means 9 in the present embodiment acquires the instantaneous and local index scalar quantity G by numerical analysis of the equation (24), which is a conservation equation for the index scalar quantity G, and also includes algebraic expressions (27) to (27) 29) by substituting the instantaneous / local index scalar quantity G and the instantaneous / local stored scalar quantity acquired by the instantaneous / local stored scalar quantity acquisition means 7 into 29), the instantaneous and local temperature, density and other Calculate the necessary physical properties.

  The index scalar quantity is not limited to that based on the above-mentioned G equation. For example, a document (Noboru Oshima, “An extensional formulation for a diffusive solution of the level-set” equation by considering a relation to the scalar conservation equation ”, Mechanical Engineering Letters, Vol. 2 (2016) p. 16-00220, [online], April 21, 2016, The Japan Society of Mechanical Engineers, [2016 Search on May 2, 2009], <URL: https://www.jstage.jst.go.jp/article/mel/2/0/2_16-00220/_article>) May be.

  Next, the combustion flow analysis means 10 numerically analyzes the 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. .

  In this embodiment, a large eddy simulation (LES) 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.

The basic equations of the large eddy simulation method in which the low-Mach number approximation is applied to the mass conservation law and momentum conservation law of the incompressible fluid and the spatial filter is applied are expressed by the following equations (30) and (31). .
... Formula (30)
... Formula (31)
Here, [rho is the density of the mixture, the x _i spatial coordinates in the orthogonal coordinate system (i = 1, 2, 3), the u _i rate of the i direction of the mixture, mu is the viscosity coefficient. The superscript-indicates the spatial average, the superscript-indicates the spatial fable average (also referred to as “density weight average”), and the subscript SGS indicates the sub-grid scale model constant representing the fluctuation effect below the spatial average. Yes.

A standard Smagorinsky model was used as the SGS turbulence model. This model is expressed as the following equation (32).
,
,
... Formula (32)
Here, C _s is a Smagorinsky constant, Δ is a spatial filter width (analysis grid width), and S _ij having superscript “˜” is a strain tensor.

Further, the equation (2), which is a conservation equation of Z representing the mixing fraction of the fuel and the oxidant, is expressed as the following equation (33).
... Formula (33)
Here, σ _{Z and SGS} are parameters corresponding to the turbulent Schmidt number.

Furthermore, the equation (12), which is a conservation equation for the mass fraction Z _C of carbon C contained in the fuel, is expressed as the following equation (34).
... Formula (34)

Further, the equation (24) which is a conservation equation of the index scalar quantity G is expressed as the following equation (35).
... Formula (35)
Here, σ _G is a parameter corresponding to the turbulent Prandtl number when the index scalar quantity G is regarded as a dimensionless temperature.

In the present embodiment, the following equation (36), which is a gradient diffusion model, is used as the second term on the right side of equation (35).
... Formula (36)

Furthermore, the local turbulent combustion speed S ^* of the first term on the right side of the above equation (35) is expressed by the following equation (37) based on the above equation (26).
... Formula (37)
That is, equation (37) takes into account the effect that the actual flame area increases due to the deformation of the SGS in the area of the GS flame surface coarse-grained by the spatial filtering of LES with respect to the SGS turbulent combustion velocity S _SGS . Is for.

In the present embodiment, the following equations (38) and (39) are used as the SGS turbulent combustion velocity model.
,
... Formula (38)
,
... Formula (39)
Further, the limit value of S _SGS / S _L is expressed as the following formula (40).
... Formula (40)

Further, the above formulas (27) to (29) representing the mass fraction, temperature, and density in consideration of the index scalar quantity G are represented as the following formulas (41) to (43).
... Formula (41)
... Formula (42)
... Formula (43)

  The combustion flow analysis means 10 in the present embodiment calculates the flow by numerically analyzing the above equations (30) to (43) based on the large eddy simulation method.

  The combustion flow analysis means 10 is not limited to the one based on the large eddy simulation method, but includes other methods such as the DNS method (Direct Numerical Simulation) for directly solving the Navier-Stokes equations without using a model, and the Reynolds average model. It is possible to appropriately select from a method using the model.

  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 the functional block diagram showing the function of each component shown in FIG. 6 and the flowchart shown in FIG. .

  As shown in FIG. 7, first, the chemical reaction condition database creation means 6 acquires the chemical reaction conditions by numerical analysis using the stored scalar quantity, and stores the chemical reaction conditions 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 quantity setting unit 61 of the chemical reaction condition database creating means 6 includes a mass fraction ξ of the fuel in the gas mixture shown in the equation (1), a normalized enthalpy ξ _{h of} the gas mixture shown in the equation (6), an equation ( Four kinds of stored scalar quantities are set, ie, the ratio of carbon in fuel ξ _c shown in 11) and the ratio of oxygen in oxidant ξ _o shown in equation (16) (step S11). In the present embodiment, a general flame structure can be represented by setting these four types of stored scalar quantities.

Next, the stored scalar quantity combination setting unit 62 sets an arbitrary combination of two types of stored scalar quantity values, that is, the fuel mass fraction ξ in the air-fuel mixture and the carbon ratio ξ _{c in} the fuel (step S12). ). Specifically, as shown in FIG. 3, with dividing the a _n from conceivable a ₁ as the value of the mass fraction xi] of the fuel in the air-fuel mixture based on the combustion conditions, the proportion of carbon in the fuel xi] _c of dividing the a _m from a ₁ assumable as the value is set as a combination thereof.

Next, the chemical reaction condition acquisition unit 63 sets the temperature in the thermal equilibrium state in each combination of the fuel mass fraction ξ and the carbon ratio ξ _c in the fuel mixture set by the storage scalar quantity combination setting unit 62, The chemical reaction conditions including the density and mass burning rate in the thermal equilibrium state are acquired by performing dimensionless reaction calculation based on the equations (1) to (21) (step S13). In this embodiment, since the density and mass combustion rate in the thermal equilibrium state are included as the chemical reaction conditions, it is possible to calculate the index scalar quantity G in the instantaneous / local physical property value calculation means 9.

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 42 for each combination of the fuel mass fraction ξ and the carbon ratio ξ _c in the fuel mixture is completed, the process proceeds to the next step (return).

The instantaneous / locally stored scalar quantity acquisition means 7 combines the conservation equation of the mass fraction ξ of the fuel in the gas mixture and the ratio ξ _c of the carbon in the fuel, and obtains a numerical solution thereof to obtain the instantaneous and local The mass fraction ξ of the fuel in the gas mixture and the carbon fraction ξ _c in the instantaneous and local fuel are obtained (step S2).

Then, as shown in FIG. 6, the instantaneous / local chemical reaction condition calculation means 8 receives the mass fraction ξ of the fuel in the instantaneous and local mixture from the instantaneous / local storage scalar quantity acquisition means 7 and the instantaneous and local fuel. obtains the ratio xi] _c of carbon in the chemical reaction conditions to their instantaneous-local storage scalar combination of the mass fraction xi] and the fuel of the fuel in air-fuel mixture near the the percentage xi] _c carbon combination Are read from the chemical reaction condition database 42, and instantaneous and local chemical reaction conditions are calculated based on the read chemical reaction conditions (step S3).

  Next, the instantaneous / local physical property value calculating means 9 calculates the instantaneous and local index scalar quantity G by numerically analyzing the conservation equation of the index scalar quantity G. In this embodiment, the instantaneous / local index scalar quantity G and the instantaneous / locally stored scalar quantity acquired by the instantaneous / locally stored scalar quantity acquiring unit 7 are substituted into the equations (41) to (43). Thus, instantaneous and local temperature, density and other necessary physical property values are calculated (step S4). Thus, in the present embodiment, the instantaneous / local physical property value can be solved by the time evolution differential equation of the index scalar quantity G.

  As shown in FIG. 6, 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 and the above formulas (30) to (43), the flow with combustion is numerically analyzed by the large eddy 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. By using the index scalar quantity G, it is possible to perform numerical analysis of the combustion flow in which the combustion chemical reaction is in a non-equilibrium state.
2. Since the physical property value can be calculated by solving the time evolution differential equation of the index scalar quantity G without using the theoretical value or the physical property value based on the experiment, the input of the theoretical value and the experiment become unnecessary, and various analyzes are possible. Application to the target becomes easy.
3. The versatility in the invention described in Patent Document 1 can be inherited, and an increase in calculation load and data amount can be suppressed.

  Next, specific examples of the combustion flow numerical analysis program and the combustion flow numerical analysis method according to the present invention will be described. The technical scope of the present invention is not limited to the features shown by the following examples.

  In Example 1, a test analysis was performed on laminar combustion in which fuel is a mixture of methane and hydrogen before the combustion flow numerical analysis program and the combustion flow numerical analysis method according to the present invention are applied to an actual combustor. This numerical analysis was performed mainly for the purpose of confirming the operation of the code that implemented the combustion flow numerical analysis program. Hereinafter, numerical analysis conditions and numerical analysis results in the first embodiment will be described.

<Object of analysis>
As shown in FIG. 9, the analysis region is a combustion flow field having a rectangular plate shape in which the x-axis direction is 400 mm, the y-axis direction is 100 mm, and the z-axis direction is 5 mm. This analysis region is formed of a plurality of analysis lattices each having a hexahedral cubic lattice throughout the analysis region. The total number of elements of the analysis grid is 10,000, and the total number of contacts is 20402.

<Boundary conditions>
Next, boundary conditions of the combustion flow field will be described. As shown in FIG. 9, one end surface of the combustion flow field is an inflow surface (Inlet) into which fuel and oxidant flow, and the other end surface at a symmetrical position of the inflow surface is an outflow surface (Outlet). The other four surfaces are heat insulating wall surfaces that do not allow heat and flow to enter and exit.

  Inflow surface is a system in which gases of different compositions are supplied from multiple inlets, so in order from the bottom, Inlet_Fuel that supplies pure fuel, Inlet_Air1 that supplies dry air as an oxidizer, and fuel and air are mixed in advance Inlet_Premixed for supplying the premixed air and Inlet_Air2 for supplying dry air.

In Example 1, as shown in Table 1 below, numerical analysis was performed based on three inflow conditions.
(Table 1)

Specifically, it is as follows. The percentage (%) indicating the configuration of the supplied gas is a mass flow rate ratio.
Case A supplied 100% hydrogen as fuel from Inlet_Fuel, 100% hydrogen as premixed gas from Inlet_Premixed, and 100% dry air as oxidant from Inlet_Air1 and Inlet_Air2.
Case B supplied 100% methane as fuel from Inlet_Fuel, 100% methane as premixed gas from Inlet_Premixed, and 100% dry air as oxidant from Inlet_Air1 and Inlet_Air2.
Case C supplied 50% methane and 50% hydrogen as fuel from Inlet_Fuel, 100% methane as premixed gas from Inlet_Premixed, and 100% dry air as oxidant from Inlet_Air1 and Inlet_Air2.

In each case, the carbon ratio ξ _c in the fuel calculated based on the equation (11) is ξ _c = 0 in case A, ξ _c = 0.75 in case B, and ξ _c = 0. 35. That is, when ξ _c = 0, the mass ratio of hydrogen represents 100%, and when ξ _c = 0.75, the mass ratio of methane represents 100%.

Therefore, the range of the carbon ratio ξ _c in the fuel is 0 ≦ ξ _c ≦ 0.75 based on the equation (13). Further, since the carbon ratio ξ _c in the fuel is ξ _{c, min} = 0 and ξ _{c, max} = 0.75, based on the equations (14) and (15), when 0> ξ _c , ξ _{When c} = 0 and ξ _c > 0.75, a limit of ξ _c = 0.75 is provided.

  The heat insulating wall surface was set to a so-called slip condition without a thermal gradient and a velocity gradient in order to prevent heat and flow from entering and exiting.

As shown in Table 2 below, the ambient conditions are an ambient pressure of 1.82 MPa, a fuel temperature of 298.15 K, and an oxidant temperature of 723.15 K. The fuel density when the fuel in case A is 100% hydrogen is 0.206 kg / m ³ . Similarly, the fuel density when the fuel of case B is 100% methane is 4.855 kg / m ³ . Further, when the fuel of Kale C is 50% hydrogen and 50% methane, the fuel density is 2.616 kg / m ³ . The density of the oxidizer is 21.14 kg / m ³ .
(Table 2)

<Creation of chemical reaction condition database>
Next, the creation of a chemical reaction condition database in Example 1 will be described.

First, the temperature in the thermal equilibrium state, the density in the thermal equilibrium state, and the laminar flow rate are calculated by numerical analysis as a function of the mixing fraction ξ and the carbon ratio ξ _c . Specifically, using chemical reaction calculation software CHEMKIN-PRO15112 [18] (Reaction Design (currently ANSYS, Inc.)), the dimensionless chemical equilibrium model shown in equations (1) to (21) is obtained. Detailed reaction calculations were performed. At this time, a database GRI-MECH3.0 published by the American Gas Association (GRI) was used for various physical property values in chemical reactions.

As described above, the minimum value of xi] _c is ξ _{c, min} = _0, the maximum value of the xi] _c is ξ _c, max = 0.75. Therefore, the calculation of temperature, density, and laminar burning velocity was made 16 each from 0 to 0.75 with a value of ξ _c in increments of 0.05. For the laminar flow combustion speed, for ease of numerical analysis was carried out numerical analysis as the mass combustion velocity is the product of the laminar flow combustion speed S _L and the non燃密degree [rho _u.

  The numerical analysis results of the temperature in the thermal equilibrium state, the density in the thermal equilibrium state, and the mass combustion rate are shown in FIGS. In addition, as shown in FIG. 13 and FIG. 14, it described with the specific volume which is the reciprocal number about a density.

The chemical reaction condition database in the first embodiment is stored in the storage unit of the computer 1 that performs numerical analysis of the combustion flow described later by approximating a polynomial as a function of ξ and ξ _c . Values between the tables are calculated by selecting data to be interpolated. For example, the value in the case of ξ _c = 0.33 is linearly interpolated by selecting data of ξ _c = 0.30 and ξ _c = 0.35.

<Analysis model of combustion flow>
The finite volume method was used for the numerical analysis of the combustion model. In addition, the flow analysis in Example 1 was performed by the DNS method in which the governing equation of the flow field is directly calculated without using the turbulent flow model in consideration of the low flow laminar flow.

The time increment was 5.0 × 10 ⁻⁴ s, and the Euler implicit method was used for the time integration method. First-order upwind differences were used for the advection term discretization scheme of the equations of motion and the conserved scalar quantities. The SIMPLE method was used for coupling momentum and pressure, and the ICGC method was used for pressure solution.

<Physical properties used for combustion flow analysis>
The laminar Schmidt number σ _z used in the calculation of the conservation equations for the storage scalar quantities Z and Z _c was σ _z = 1.0. The parameter σ _G corresponding to the laminar flow Prandtl number used in the calculation of the conservation equation for the index scalar quantity _G was set to σ _G = 1.0.

For the viscosity coefficient, the following equation (44), which is a simplified transport coefficient model, was used in order to consider temperature dependence.
... Formula (44)
Here, A = 2.58 × 10 ⁻⁵ kg / m / s, γ = 0.7, and T ₀ = 298K.

<Computer used for combustion flow analysis>
In Example 1, HITACHI HA8000-tc / HT210 of Kyushu University Information Technology Research and Development Center was used as a computer for numerical analysis. The computer is a computer that can perform two parallel calculations. In the first embodiment, the calculation time is about 1 hour per 5000 steps.

<Results of combustion flow analysis>
The analysis results shown below are instantaneous values at the number of steps 50000. Further, as shown in FIG. 17, the plot acquisition position of the Z-axis cross section shown in FIGS. 19, 21, 24, and 28 is from the center position with respect to the flow direction of x = 200 mm from y = 0 mm to y = 100 mm. Position.

  The temperature distribution will be described as an analysis result. FIG. 18 shows the temperature distribution obtained by the analysis. Hereinafter, in each distribution diagram, the magnitude of each value is indicated by a color gradation.

  When comparing the case A in which the fuel shown in FIG. 18 is 100% hydrogen and the case B in which the fuel is 100% methane, the case A shows a tendency that the region where the temperature is higher than the case B is wider. That is, Case A shows that the burned region is wider than Case B, which is consistent with the numerical analysis results of the index scalar quantity G shown in FIGS.

  Next, Case C, which is a mixture of 50% hydrogen and 50% methane, shows almost the same distribution tendency as Case A, which is 100% hydrogen, and has a higher temperature than Case B, which is 100% methane. Became wide.

  Looking at the temperature distribution in the Y direction in the Z-axis cross section shown in FIG. 19, Case A with 100% hydrogen and Case C in which 50% hydrogen and 50% methane are mixed show almost the same distribution tendency here. The temperature was higher than 100% Case B.

Next, the relationship between the temperature distribution shown in FIGS. 18 and 19 and the mass fraction ξ of the fuel in the air-fuel mixture and the carbon ratio ξ _c in the fuel will be considered.

As shown in FIGS. 20 and 21, the distribution of the mass fraction ξ of the fuel in the air-fuel mixture was not significantly different among Case A, Case B, and Case C. On the other hand, as shown in FIG. 11, the maximum value of the temperature of the thermal equilibrium state appears to be no significant difference from xi] _{c =} 0 to xi] _{c =} 0.75, as shown in Figure 12 of the chemical reaction condition database, From the enlarged view, it can be seen that the value of the mixing fraction ξ indicating the temperature in the thermal equilibrium state differs depending on the carbon ratio ξ _c in the fuel. Therefore, it is considered that the temperature distribution varies depending on the value of the carbon ratio ξ _{c in} the fuel.

Therefore, the distribution of the carbon ratio ξ _{c in} the fuel was considered. As shown in FIG. 22, in case A where the fuel is 100% hydrogen, ξ _c = 0 over the entire region. On the other hand, in case B where the fuel is 100% methane, ξ _c = 0.75 is obtained in the entire region. Further, as described above, in the case C in which the fuel is a mixture of 50% hydrogen and 50% methane, it can be seen that the fuel gases having different compositions supplied from Inlet_Premixed and Inlet_Fuel are mixed along the flow.

As shown in FIG. 12 of the chemical reaction condition database, even in a place where the value of the mass fraction ξ of the fuel in the same mixture is shown, when the value of the carbon ratio ξ _{c in} the fuel is small and the value of the carbon fraction ξ _{c in} the fuel is small, It can be seen that the temperature of the adiabatic flame is high.

  Next, FIG. 23 and FIG. 24 show the distribution of the index scalar quantity G.

  As shown in FIG. 24, the case A with 100% hydrogen at the center position of the analysis region shows a larger value of the index scalar amount G than the case B with 100% methane, and the burned region is wide. I understand.

  Also, in Case B with 100% methane and Case C with 50% hydrogen and 50% methane, the distribution of index scalar quantity G is larger in Case B up to around y = 70 mm, but the portion where y = 70 mm or more. In the case C, the distribution of the index scalar quantity G is larger. It is considered that this difference in the index scalar amount G causes a difference in burned region distribution and temperature distribution in each case as described above.

Further, as shown in FIG. 25, when the enlarged distribution map of the index scalar quantity G in the vicinity of the inflow surface is seen, the difference between the cases is well understood. For example, in case A with 100% hydrogen, the mass burning rate ρ _u S _L is large, so the combustible length is shorter than in case B with 100% methane. Further, in Case C where hydrogen is 50% and methane is 50%, the length of the flame is shorter as in Case A. From these facts, it can be seen that the hydrogen ratio affects the length of the flame.

FIG. 26 shows the distribution of the mass burning rate ρ _u S _{L in} the z-axis cross section. As shown in FIGS. 15 and 16 of the chemical reaction condition database, the mass burning rate ρ _u S _L has a large difference between ξ _c = 0 and ξ _c = 0.75. _When the fluctuation range of the _c value is small, the value of the mass burning rate ρ _u S _L does not change greatly. In fact, in FIG. 26, when comparing Case A with 100% hydrogen and Case B with 100% methane, there is a large difference in the value of the mass burning rate ρ _u S _L. In addition, the distribution of mass burning rate ρ _u S _L in case C where hydrogen is 50% and methane is 50% is larger than that in case B where methane is 100%.

Therefore, it is considered that the difference in the mass burning rate ρ _u S _L between the cases causes a difference in the distribution of the index scalar quantity G. In addition, the case A with 100% hydrogen has a larger distribution of the value of the mass burning rate ρ _u S _L than the case B with 100% methane, so that the burned region is large and the distribution of the index scalar quantity G is also considered to be large. .

Next, the density distribution will be considered. As shown in FIGS. 13 and 14, the specific volume is larger when ξ _c = 0 of 100% hydrogen. That is, the density is low. Therefore, the density decreases as the value of the carbon ratio ξ _c in the fuel decreases and the ratio of hydrogen increases.

  In fact, as shown in FIGS. 27 and 28, the case A with 100% hydrogen shows a smaller overall density distribution than the case B with 100% methane. Similarly, in case C where hydrogen is 50% and methane is 50%, the density is smaller than in case B where methane is 100%, and the effect of introducing hydrogen can be seen. In addition, the increase in burned area due to the introduction of hydrogen is considered to be a cause of the decrease in density.

  As described above, in the first embodiment, the numerical analysis is performed on the laminar combustion in which the fuel is the methane and hydrogen mixture, and the combustion flow numerical analysis program using the index scalar quantity G is executed to execute the combustion. It can be shown that the chemical reaction can numerically analyze the combustion flow in non-equilibrium state.

  In Example 2, the numerical analysis of the combustion flow for the actual combustion flow field was performed using the code in which the combustion flow numerical analysis program whose operation was confirmed in Example 1 was installed.

<Object of analysis>
In Example 2, the combustor mounted on the 18 MW class gas turbine L20A developed by Kawasaki Heavy Industries, Ltd., the applicant of the present application, was analyzed. As shown in FIG. 29, the analysis region of the combustor is from the swirler of the combustor to the buffer region added to the rear end of the combustor to prevent backflow.

  The analysis grid was a hexahedral grid throughout the combustor. The total number of elements of the analysis grid is 10025904, and the number of contacts is 10181403.

<Boundary conditions>
In the second embodiment, an AFR value of about 42 under actual working conditions is used as the air-fuel ratio. Further, as shown in Table 3 below, the operating conditions were set to the actual operating conditions, and the fuel temperature was 25 ° C., the air temperature was 450 ° C., and the air inflow pressure was about 1.8 MPa.
(Table 3)

  Further, as shown in FIG. 30, premixed gas flows from INLET-MAIN and INLET-PRIMARY, and fuel flows from INLET-PILOT to stabilize the flame. In addition, air flows from INLET-LINER. From INLET-SB, premixed gas with different fuel concentration and composition flows depending on conditions. Since unburned gas flows from any inflow boundary, the index scalar amount G is set to G = 0. In an actual combustor, fuel and air are flowed from separate flow paths before the combustion chamber and mixed in the flow path to the combustion chamber. In this analysis, the flow rate is adjusted from the air inlet in the experiment and the premixed gas is introduced. Each gas was assumed to be a uniform flow.

  In the present Example 2, it analyzed and compared about the case 1 which burns only methane and the case 2 which burns methane and hydrogen as a fuel, respectively.

As shown in Table 4 and Table 5 below, Case 1 and Case 2 both supplied premixed gas of 100% methane (ξ _C = 0.75) to the fuel from INLET-MAIN and INLET-PRIMARY. In addition, 100% methane was supplied as pure fuel from INLET-PILOT. Furthermore, in Case 1, only 100% methane was supplied from INLET-SB. On the other hand, in Case 2, when the flame was sufficiently developed, the fuel was switched to a fuel mixed with a mass fraction of 44% methane and 56% hydrogen (ξ _C = 0.33). Note that dry air (oxygen: nitrogen = 21%: 79%) was used as the oxidizing agent.
(Table 4)
(Table 5)

The ignition procedure is as follows. G = 0, which is unburned in all regions, and a flow field is formed during 2000 steps (cold flow), and then G = 1, which is burnt in the inflow condition INLET-MAIN, is ignited. went. After that, it was judged that the flame was sufficiently developed in 12000 steps, and the value of the index scalar amount G of INLET-MAIN was set to G = 0 of unburned. Subsequently, in case 2 where the number of steps was advanced to stabilize the flame and hydrogen was introduced, ξ _C = 0.33 was set at the inflow boundary INLET-SB at the 19000th step, and hydrogen was supplied.

<Chemical reaction condition database>
The chemical reaction condition database in Example 2 was the same as that created in Example 1.

<Calculation conditions>
In the second embodiment, an unsteady turbulent numerical analysis method combining a combustion calculation based on a plurality of stored scalar quantities and a large eddy simulation method is used. In Example 2, the finite volume method was used.

The standard Smagorinsky model of Equation (32) was adopted as the sub-grid scale model of the large eddy simulation method, and the Smagorinsky constant was C _s = 0.1. The laminar Schmidt number σ _Z used in calculating the conservation equation of Z representing the mixture fraction of fuel and oxidizer and the conservation equation of the mass fraction Z _C of carbon C contained in the fuel is σ _Z = 0.7, The turbulent Schmidt number σ _{Z, SGS} was set to σ _{Z, SGS} = 0.5. The parameters σ _{G and SGS} corresponding to the turbulent Prandtl number used in the calculation of the conservation equation for the index scalar quantity G are set to σ _{G and SGS} = 0.25. In order to consider the temperature dependence of the viscosity coefficient, the Sutherland equation represented by the following equation (45) was used.
... Formula (45)

The parameters were set such that the reference temperature T ₀ = 298.15 K, the reference viscosity coefficient μ ₀ = 1.82 × 10 ⁻⁵ kg / m / s, and the Sutherland coefficient C = 110.4. The Euler implicit method is used for the time integration method, and the conservative equation advection term discretization scheme uses a scheme that linearly combines the second-order accuracy central difference method 95% and the first-order upwind difference method 5%. A quadratic center difference was used for the advection term discretization scheme of the equation. The SIMPLE method was used for coupling momentum and pressure, and the ICCG method was used for pressure release.

<Computer used for combustion flow analysis>
In Example 2, as in Example 1, HITACHI HA8000-tc / HT210 of Kyushu University Information Technology Research and Development Center was used as a computer for numerical analysis. Moreover, in the present Example 2, the parallel number was 128. Furthermore, the calculation time was about 6 hours per 1000 steps.

<Results of combustion flow analysis>
The analysis results are shown below. 32 shows the instantaneous value of the temperature distribution in the z-axis section of the combustor shown in FIG. 31, and FIG. 33 shows the instantaneous value of the temperature distribution in the x-axis section of the combustor outlet shown in FIG. Both Case 1 and Case 2 have a high temperature region in the center of the combustor upstream from the boundary INLET-SB, which is the reheating burner of the combustor, and the temperature is low near the wall. .

  On the other hand, the case 1 using only methane as the fuel and the case 2 using hydrogen were greatly different in temperature distribution downstream from the combustion burner (INLET-SB).

FIG. 34 is an instantaneous value distribution of the mass combustion speed ρ _u S _{L in} the combustor z-axis cross section. In case 1 where only methane is used as fuel, and in case 2 where hydrogen is introduced into the fuel, there is a large difference in distribution downstream from the reheating burner (INLET-SB), but upstream from the reheating burner (INLET-SB). There is no difference in distribution in the part. As can be seen from the distribution of the carbon ratio ξ _c in the fuel in FIG. 35, there is no hydrogen upstream from the reheating burner (INLET-SB), so the mass burning rate is only downstream from the reheating burner where hydrogen is present. It is expected that there was a difference in ρ _u S _L. Since there is no difference in the distribution of the fuel mass fraction ξ in the mixture in both cases 1 and 2, this is due to the difference in the distribution of the carbon fraction ξ _{c in} the fuel due to the introduction of hydrogen. It is thought that. In fact, referring to the graphs of FIG. 15 and FIG. 16 in the chemical reaction condition database, it can be seen that the mass burning rate ρ _u S _L increases as the amount of hydrogen increases and the ξ _c value decreases at the same ξ value. From this, it can be understood that the value of mass burning velocity ρ _u S _L downstream from the reheating burner (INLET-SB) was greatly evaluated by introducing hydrogen.

According to the instantaneous value of the mass burn rate [rho _u S _L in the combustor z-axis cross-section shown in the mass burn rate [rho _u S _L and 34 chemical reactions condition database shown in FIG. 14, as including a large amount of hydrogen xi] _c value is smaller It can be seen that the mass burning rate ρ _u S _L increases and combustion is easy. In other words, in Case 2 in which hydrogen is supplied, the mass combustion rate ρ _u S _L is increased because the ξ _c value decreases and the hydrogen ratio increases in the vicinity of the reheating burner (INLET-SB) and downstream thereof, and combustion is easy. Thus, as shown in FIG. 36, it is considered that the distribution of burned index scalar quantity G is also increased. Moreover, it seems that the region where the temperature is high also spreads due to the spread of the burned G distribution.

  As mentioned above, the numerical analysis of the combustion flow for the actual combustion flow field could be performed using the code equipped with the combustion flow numerical analysis program. Further, as a result of analysis, in the combustor mounted on the 18 MW class gas turbine L20A targeted in the second embodiment, hydrogen fuel is supplied from the reheating burner (INLET-SB), and downstream of the combustor. It was found that the region with high temperature spreads.

The combustion flow numerical analysis program and the combustion flow numerical analysis method according to the present invention are not limited to the above-described embodiments, and can be changed as appropriate. Fuels and oxidants handled by numerical analysis are not limited to hydrogen, methane, and dry air. For example, hydrocarbon fuels are not limited to methane, but polymer fuels such as ethylene (C ₂ H ₄ ), cyclohexane (C ₆ H ₁₂ ), benzene ring systems, and gasoline containing multiple bonds and cyclic structures. It may be. In addition, the fuel is not limited to hydrogen fuel or hydrocarbon fuel, but fuel containing oxygen element O such as methyl alcohol (CH ₃ OH), sulfur such as ammonia (NH ₃ ) and sulfurous acid (SO ₂ ). A fuel containing the element S or the nitrogen element N may be used. Furthermore, the fuel and the oxidant may contain an inert element such as steam (water), carbon monoxide, and argon.

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 quantity 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 section 42 Chemical reaction condition database 61 Stored scalar quantity setting section 62 Stored scalar quantity combination setting section 63 Chemical reaction condition acquisition section 64 Database creation section

Claims (2)

A combustion flow numerical analysis program for numerically analyzing a flow accompanying combustion of fuel and oxidant,
The temperature in the thermal equilibrium state and the density in the thermal equilibrium state using the predetermined storage scalar amount among the plurality of storage scalar amounts set based on the chemical composition in the fuel, the oxidant and the combustion mixture obtained by mixing them. And chemical reaction condition database creation means for acquiring chemical reaction conditions including mass combustion rate by numerical analysis and storing the chemical reaction conditions in the chemical reaction condition database,
Instantaneous / locally stored scalar quantity acquisition means for acquiring the instantaneous / locally stored scalar quantity by numerical analysis using the conservation equation of the stored scalar quantity,
Instantaneous / local chemical reaction condition calculating means 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 quantity;
Instantaneous / local physical property value calculating means for calculating an instantaneous / local physical property value using an equation scalar quantity conservation equation representing a non-equilibrium state of a combustion reaction and the instantaneous / local chemical reaction condition;
Combustion flow numerical analysis for causing a computer to function as a combustion flow analysis means for numerically analyzing the 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 program. A combustion flow numerical analysis method for numerically analyzing a flow accompanied by combustion of a fuel and an oxidant,
The temperature in the thermal equilibrium state and the density in the thermal equilibrium state using the predetermined storage scalar amount among the plurality of storage scalar amounts set based on the chemical composition in the fuel, the oxidant and the combustion mixture obtained by mixing them. And a chemical reaction condition database creation step for acquiring chemical reaction conditions including mass combustion rate by numerical analysis and storing the chemical reaction conditions in the chemical reaction condition database;
Instantaneous / locally stored scalar quantity acquisition step of acquiring the instantaneous / locally stored scalar quantity by numerical analysis using the conservation equation of the stored scalar quantity;
Instantaneous / local chemical reaction condition calculation 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 quantity;
Instantaneous / local physical property value calculating step for calculating an instantaneous / local physical property value using an equation scalar quantity conservation equation representing a non-equilibrium state of a combustion reaction and the instantaneous / local chemical reaction condition;
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.