JP6796395B2 - Combustion flow numerical analysis program and combustion flow numerical analysis method - Google Patents

Description

The present invention relates to a combustion flow numerical analysis program and a combustion flow numerical analysis method for numerically analyzing the flow of fuel and an oxidant accompanied by combustion.

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

In general, the combustion of fuel and oxidizer is composed of multi-step reactions by many molecular species, and the combustion process is mainly governed by the following relationship.
(1) Conservation of mass of all chemical species existing in the chemical reaction process (3) Conservation of momentum of the combustion mixture (4) Conservation of energy of the combustion mixture

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

For example, the chemical reaction elementary process is considered to consist of 9 kinds of chemical substances and 21 kinds of elementary reactions when hydrogen fuel is used. Further, when a hydrocarbon fuel is used, 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 spatial scale and time scale of the chemical reaction are small space and short time reaction, which is about 1/10 of the spatial scale and time scale of the flow, and the numerical analysis of the number of lattice points and the time step in the numerical analysis of the flow. Must be finer than. Therefore, if the numerical analysis of the governing equation is directly performed without using an approximate model for the multi-step reaction by such a large number of molecular species, a huge calculation load is required. Therefore, although the chemical reaction elemental process has been investigated in detail, it has been pointed out that it is difficult to numerically analyze various multi-stage chemical reactions such as combustion flow and the flow at the same time.

To solve this problem, conventionally, by using a storage scalar amount that represents the diffusion mixture of the combustion mixture of fuel and oxidizer, numerical analysis of chemical reaction and numerical analysis of flow are separated in advance and numerical analysis is performed. There is a method called flamelet approach. However, this flamelet approach assumes a combustion reaction state with only one type of stored scalar quantity, lacks versatility for various fuels, or changes in flow and thermal conditions, and is based on the principle of application range and analysis accuracy. Is limited.

Therefore, the inventors of the present application have solved the problems of the applicable 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 amounts. We have proposed an invention related to a flow numerical analysis program and a combustion flow numerical analysis method, and obtained a patent right (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 to it, it is suitable for simulation in such a state, but it is actually burned. It cannot be applied to the numerical analysis of so-called non-equilibrium chemical reactions in which combustion progresses little by little like a flow field.

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

The combustion flow numerical analysis program according to the present invention is a combustion flow numerical analysis program for numerically analyzing the flow of a fuel and an oxidizing agent that accompanies combustion, and is used for each of the fuel, the oxidizing agent, and a combustion mixture in which they are mixed. Among a plurality of stored scalar amounts set based on the chemical composition, 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 using the predetermined stored scalar amount. A means for creating a chemical reaction condition database that stores the chemical reaction conditions in the chemical reaction condition database, and a means for acquiring an instantaneous / locally preserved scalar amount by numerical analysis using the preservation equation of the preserved scalar amount. And the instantaneous / local chemical reaction condition calculation means for calculating the instantaneous / local chemical reaction condition using the chemical reaction condition stored in the chemical reaction condition database and the instantaneous / locally preserved scalar amount, and the non-equilibrium state of the combustion reaction. Instantaneous / local physical property value calculation means for calculating the instantaneous / local physical property value using the conservation equation of the scalar amount and the instantaneous / local chemical reaction condition, the instantaneous / local chemical reaction condition, and the instantaneous / local physical property value. The computer functions as a combustion flow analysis means for numerically analyzing the flow of the fuel, the oxidizing agent, and the combustion mixture with combustion using the above.

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 a fuel and an oxidizing agent, and is used for each of the fuel, the oxidizing agent, and a combustion mixture in which they are mixed. Among a plurality of stored scalar amounts set based on the chemical composition, 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 using the predetermined stored scalar amount. A step of creating a chemical reaction condition database in which the chemical reaction conditions are stored in the chemical reaction condition database, and a step of acquiring an instantaneous / locally preserved scalar amount by numerical analysis using the preservation equation of the preserved scalar amount. And the instantaneous / local chemical reaction condition calculation step for calculating the instantaneous / local chemical reaction condition using the chemical reaction condition stored in the chemical reaction condition database and the instantaneous / locally preserved scalar amount, and the non-equilibrium state of the combustion reaction. The instantaneous / local physical property value calculation step for calculating the instantaneous / local physical property value using the conservation equation of the scalar amount and the instantaneous / local chemical reaction condition, the instantaneous / local chemical reaction condition, and the instantaneous / local physical property value. It has a combustion flow analysis step of numerically analyzing the flow of the fuel, the oxidizing agent, and the combustion mixture with combustion using the above.

According to the present invention, the combustion chemical reaction can be applied to the numerical analysis which is the combustion flow in the non-equilibrium state, and the increase in the calculation load accompanying the combustion can be suppressed.

It is a block diagram which shows one Embodiment of the computer provided with the combustion flow numerical analysis program which concerns on this invention. It is the schematic which shows the range of the value of the combustion field of this embodiment and the assumed fuel composition scalar amount ξ. It is a schematic diagram which shows arbitrary combination of two kinds of preservation scalar amounts set by the preservation scalar amount combination setting part of this embodiment. It is a schematic diagram which shows the calculation example of the instantaneous / local chemical reaction condition in the instantaneous / local chemical reaction condition calculation means of this embodiment. It is a conceptual diagram which shows the premixed combustion using the index scalar amount G in this embodiment. It is a functional block diagram which shows the function of each structure of this embodiment. It is a flowchart which shows the process flow in the combustion flow numerical analysis program and the combustion flow numerical analysis method of this embodiment. It is a flowchart which shows the flow of processing in the chemical reaction condition database creation means of this embodiment. It is a perspective view which shows the rectangular plate-shaped combustion flow field which was analyzed in 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 this Example 1. The three-dimensional graph shown in FIG. 10 is a graph seen xi] _c-axis direction. It is a graph which enlarged a part of FIG. It is a three-dimensional graph which shows the database of the specific volume (reciprocal of density) in the thermal equilibrium state created by the chemical reaction condition database creation means of this Example 1. The three-dimensional graph shown in FIG. 13 is a graph seen xi] _c-axis direction. It is a three-dimensional graph which shows the database of the mass combustion rate created by the chemical reaction condition database creation means of this Example 1. The three-dimensional graph shown in FIG. 15 is a graph seen xi] _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 this Example 1. It is a temperature distribution chart which shows the analysis result of this Example 1. It is a temperature distribution chart at 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 which shows the analysis result of this Example 1. It is a distribution map of the mass fraction ξ of the fuel in the air-fuel mixture at the plot acquisition position of the Z-axis cross section shown in FIG. It is a distribution map of the carbon ratio ξ _c and the carbon mass fraction Z _{c in} the fuel which shows the analysis result of this Example 1. It is a distribution map of the index scalar quantity G which shows the analysis result of this Example 1. It is a distribution map of the index scalar amount G at the plot acquisition position of the Z-axis cross section shown in FIG. It is an enlarged distribution map of the index scalar amount G which shows the analysis result of this Example 1. It is a mass combustion rate distribution map which shows the analysis result of this Example 1. It is a density distribution map which shows the analysis result of this Example 1. It is a density distribution chart at 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 which was analyzed in this Example 2. It is a perspective view which shows the supply place of fuel and oxidant in this Example 2. FIG. It is a schematic diagram which shows the data acquisition position and dimensionless coordinates of the cross-sectional plot in Example 2. FIG. It is a temperature distribution map which shows the analysis result of this Example 2. It is a temperature distribution chart at the data acquisition position of the cross-sectional plot shown in FIG. It is a mass combustion rate distribution map which shows the analysis result of this Example 2. The analysis results of Example 2 is a distribution diagram of the carbon percentage xi] _c in the fuel shown. It is an enlarged distribution map of the index scalar amount G which shows the analysis result of this Example 2.

Hereinafter, an embodiment of the combustion flow numerical analysis program and the 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 according to the present embodiment.

The computer 1 in the present embodiment is mainly composed of an input means 2, a display means 3, a storage means 4, and an arithmetic processing means 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 includes a liquid crystal display, a CRT display, a touch panel, etc. for displaying images and text data, and can display the contents and analysis results input by the input means 2 as a user interface in the combustion flow numerical analysis program 1a. It has become.

The storage means 4 is composed of a ROM (Read Only Memory), a RAM (Random Access Memory), a hard disk, a flash memory, etc., and stores various data and is a working area when the calculation processing means 5 performs a calculation. It functions as.

In the present embodiment, as shown in FIG. 1, the storage means 4 is mainly acquired by the program storage unit 41 that stores the combustion flow numerical analysis program 1a and the chemical reaction condition database creation means 6 of the arithmetic processing means 5 described later. It has a chemical reaction condition database 42 for storing the obtained chemical reaction conditions.

The combustion flow numerical analysis program 1a of the present embodiment is installed in the program storage unit 41. Then, the arithmetic processing means 5 executes the combustion flow numerical analysis program 1a to make the computer 1 and the like function as each component described later.

The usage pattern of the combustion flow numerical analysis program 1a is not limited to the above configuration. For example, the combustion flow numerical analysis program 1a may be stored in a non-temporary recording medium that can be read by the computer 1, such as a CD-ROM or a USB memory, and read directly from this recording medium for execution. .. Further, it may be used by a cloud computing method, an ASP (application service provider) method, or the like from an external server or the like.

The arithmetic processing means 5 is composed of a CPU (Central Processing Unit) and the like, and by executing the combustion flow numerical analysis program 1a installed in the storage means 4, a chemical reaction condition database is created as shown in FIG. The computer 1 is made to function as the means 6, the instantaneous / locally stored scalar amount 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 using a plurality of stored scalar amounts set based on each chemical composition in the fuel, the oxidant, and the combustion mixture in which they are mixed, and obtains the chemical reaction conditions. The conditions are stored in the chemical reaction condition database 42 of the storage means 4.

The chemical reaction condition in the present embodiment is to enable the instantaneous / local physical property value calculating means 9, which will be described later, to calculate the instantaneous and local physical property value in the combustion field based on the index scalar amount G indicating the non-equilibrium state of the combustion reaction. Includes 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 the chemical species fraction and the like, if necessary.

As shown in FIG. 1, the chemical reaction condition database creating means 6 in the present embodiment includes a storage scalar amount setting unit 61, a storage scalar amount combination setting unit 62, a chemical reaction condition acquisition unit 63, and a database creation unit 64. Has.

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 act 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 oxidizing agents, the fuel and oxidizing agent can be distinguished by elements instead of inflow gas. Based on this idea, it is common to use the mass fraction ξ of the fuel in the air-fuel mixture, the normalized enthalpy ξ _h of the mixed gas, the carbon ratio ξ _c in the fuel, and the oxygen ratio ξ _o in the oxidizer. Can represent a flame structure.

Therefore, in the present embodiment, the stored scalar amounts are the mass fraction ξ of the fuel in the air-fuel mixture, the normalized enthalpy ξ _h of the mixed gas, the carbon ratio ξ _c in the fuel, 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 air-fuel mixture is set based on the mass conservation law of carbon C and hydrogen H contained in the fuel, and the mass fraction Z _{C of} carbon C contained in the fuel and the fuel It is expressed by the following equation (1) by the sum of the contained hydrogen H and the mass fraction Z _H.
... Equation (1)
Further, if the mass fraction ξ of the fuel is replaced with ξ = Z _C + Z _H = Z, the conservation equation of the mass fraction ξ of the fuel is expressed by the following (2).
... Equation (2)

At this time, the mass fraction ξ of the fuel in the air-fuel mixture is defined in the range shown in the following equation (3).
0 ≤ ξ ≤ 1 ... Equation (3)
As a result, the mass fraction ξ of the fuel in the air-fuel mixture is limited by the following equations (4) and (5).
When
... Equation (4)
When
... Equation (5)

The normalized enthalpy ξ _h of the mixed gas is represented by the following equation (6), which is dimensionless using the enthalpy reference values h _l and h _h (h _l > h _h ).
... Equation (6)
Further, the simplified conservative equation of enthalpy h is expressed by the following equation (7).
... Equation (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.
ξ _{h, min} ≤ ξ _h ≤ ξ _{h, max} ・ ・ ・ Equation (8)
As a result, the normalized enthalpy ξ _h of the mixed gas is limited to the following equations (9) and (10).
When ξ _h ≤ ξ _{h, min} ξ _h = ξ _{h, min} ・ ・ ・ Equation (9)
When ξ _h ≧ ξ _{h, max} ξ _h ＝ ξ _{h, max} ・ ・ ・ Equation (10)

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

At this time, assuming that the maximum value of the carbon ratio ξ _{c in} the fuel determined by the composition of the fuel is ξ _{c, max} and the minimum value is ξ _{c, min} , the carbon ratio ξ _c in the fuel is shown in the following equation (13). Defined in range.
ξ _{c, min} ≤ ξ _c ≤ ξ _{c, max} ... Equation (13)
As a result, the carbon ratio ξ _c in the fuel is limited by the following equations (14) and (15).
When ξ _c ≤ ξ _{c, min} ξ _c = ξ _{c, min} ・ ・ ・ Equation (14)
When ξ _c ≥ ξ _{c, max} ξ _c = ξ _{c, max} ... Equation (15)

Percentage xi] _o of oxygen in the oxidizing agent, as the ratio of the the sum of the mass fraction of oxygen and nitrogen as an oxidant _{Z O + Z N (= 1} -ξ), and the mass fraction Z _O oxygen, It is expressed by the following equation (16).
... Equation (16)
Further, conservation equations of the oxygen mass fraction Z _O is expressed by the following equation (17).
... Equation (17)

At this time, assuming that the maximum value of the oxygen ratio ξ _O in the oxidant determined by the fuel composition is ξ _{O, max} and the minimum value is ξ _{O, min} , the oxygen ratio ξ _o in the oxidant is given by the following equation (18). ) Is defined.
ξ _{o, min} ≤ ξ _o ≤ ξ _{o, max} ... Equation (18)
As a result, the oxygen ratio ξ _o in the oxidizing agent is limited by the following formulas (19) and (20).
When ξ _o ≤ ξ _{o, min} ξ _o = ξ _{o, min} ... Equation (19)
When ξ _o ≧ ξ _{o, max} ξ _o ＝ ξ _{o, max} ・ ・ ・ Equation (20)

In equations (2), (7), (12) and (17), μ is the viscosity coefficient, and σ _Z is the Schmidt number assuming that the diffusion coefficients of each chemical species are equal. Represents the Prandtl number.

Next, the storage scalar amount combination setting unit 62 is for setting an arbitrary combination according to a predetermined number of storage scalar amount values among the plurality of storage scalar amounts set by the storage scalar amount setting unit 61. is there. In this embodiment, consisting of hydrogen H ₂ and methane CH ₄ Prefecture, fuel of a different composition to flow from the plurality of fuel supply ports, also each of these compositions is assumed adiabatic combustion field time varying. Therefore, the mass fraction ξ of the fuel in the air-fuel mixture and the carbon ratio ξ _c in the fuel, which are set based on each chemical composition of the fuel, are used.

Further, in the storage scalar amount combination setting unit 62, any combination of the storage scalar amounts set in the present embodiment may be the equations (3), (8), and (13) assumed within the range of the combustion conditions. And, it is set within the range of the value of the storage scalar amount 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, it is a _n the range a ₁ of the value of the mass fraction ξ of the fuel in air mixture that is assumed 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 combination of the stored scalar amounts can be a plurality of combinations having mathematically equivalent values, and theoretically, there is no effect on the analysis result. Further, the combination of two types of storage scalar amounts is not limited, and three or more storage scalar amounts may be combined.

The chemical reaction condition acquisition unit 63 acquires the chemical reaction conditions for 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 By performing a dimensionless reaction calculation based on the formulas (1) to (21) for the combination of, the temperature in the thermal equilibrium state, the density in the thermal equilibrium state, and the mass combustion rate, which are the chemical reaction conditions, are obtained.

Then, the database creation unit 64 stores the temperature in the thermal equilibrium state, the density in 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 means 4. It is something that is memorized by.

Next, the instantaneous / locally preserved scalar amount acquisition means 7 uses the conservation equation of the preserved scalar amount, equation (2), equation (7), equation (12) and equation (17) to generate the instantaneous / locally preserved scalar amount. Is obtained by numerical analysis.

In the present embodiment, the equation (2) is a conservation equations of mass fraction xi] in the fuel, the equation (12) is stored equation of motion for the carbon fraction xi] _c in the fuel and form continuous and its numerical solution By obtaining the above, the mass fraction ξ in the instantaneous and local fuel and the carbon ratio ξ _c in the instantaneous and local fuel 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 / locally preserved scalar amount. ..

For example, as shown in FIG. 4, the combination of the instantaneous and local mass fraction ξ of the fuel acquired by the instantaneous and locally preserved scalar amount acquisition means 7 and the carbon ratio ξ _{c in} the instantaneous and local fuel is (ax _). , a case was _x), the combination (a _x, 4 one combination of carbon percentage xi] _c chemical reaction conditions mass fraction xi] and in the fuel of the fuel stored in the database 42 to the vicinity of the _{a x)} (a Obtain the chemical reaction conditions in ( _y , _Az ), ( _ay , _{Az + 1} ), ( _{ay + 1} , _Az ), ( _{ay + 1} , _{Az + 1} ), and the difference between the four combinations and the instantaneous / local combination. The instantaneous and local chemical reaction conditions are calculated from the above.

Thus, the chemical reaction conditions, such as temperature, density and mass fraction, are a function of the instantaneous and local mass fraction ξ of the fuel and the instantaneous and local carbon ratio ξ _{c in} the fuel, according to equation (21) below. Represented by.
,
,
... Equation (21)

The method for calculating the instantaneous / local chemical reaction conditions for the instantaneous / locally preserved scalar amount acquired by the instantaneous / locally preserved scalar amount acquisition means 7 is not limited to the above-mentioned method, and for example, the acquired instantaneous / locally preserved scalar amount acquisition means. The chemical reaction condition in the combination of the stored scalar amount closest to the locally stored scalar amount may be the instantaneous / local chemical condition.

Further, the chemical reaction condition database creation means 6, the instantaneous / locally preserved scalar amount 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 basically the same program code can be applied to the instantaneous / locally preserved 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 amount representing the non-equilibrium state of the combustion reaction and the instantaneous / local chemical reaction condition. The index scalar amount will be described below.

The index scalar amount represents the 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 the index scalar amount G, the position of the flame surface of the premixed flame is G = G ₀ = 0.5, and G> G ₀ . The burnt gas side and G <G ₀ are defined as the unburned gas side to represent the non-equilibrium state of the combustion reaction. At this time, the index scalar amount G is expressed by the following equation (22).
... Equation (22)
Here, T _u represents the gas temperature of the unburned, T _b represents a gas temperature of burned.

Further, the equation expressing the movement phenomenon of the premixed flame surface G = G ₀ is expressed by the following equation (23) as the G equation.
... Equation (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, the premixed flame exists only in the very thin region of G = G ₀ , and the flame thickness is defined as very thin, but the actual flame has a thickness on the order of several millimeters. There is. Therefore, in the present embodiment, the following equation (24) in consideration of the flame thickness is used as the preservation equation of the index scalar quantity G.
... formula (24)
Here, C _p is the constant pressure specific heat. Further, using the physical quantity that S ^* instead of laminar burning velocity S _L. This S ^* is a physical quantity called the local combustion rate having a distribution in the flame thickness, and is expressed by the following equation (25).
... Equation (25)

Further, the first-order approximation model of the index scalar quantity G is represented by the following equation (26), which holds accurately for different air-fuel ratios and preheating temperatures.
... Equation (26)

Further, in the gas turbine combustor analyzed in Example 2 described later, diffusion combustion and premixed combustion are mixed. 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 partial premixed combustion model that combines the two models is used.

Index scalar unburnt the G = 0 for G premixed combustion model, the G = 1 and the parameters of the burned, the temperature with respect to the distribution of the diffusion combustion model xi] and xi] _c, density, chemical species α The mass fraction will be given from the chemical reaction condition database 42. Further, it is assumed that the combination of both unburned and burned states is 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 mean of the index scalar amount G. To.
... Equation (27)
... Equation (28)
... Equation (29)

The instantaneous / local physical property value calculation means 9 in the present embodiment obtains the instantaneous and local index scalar quantity G by numerical analysis of the equation (24) which is a preservation equation of the index scalar quantity G, and algebraic expressions (27) to ( By substituting the instantaneous / local index scalar amount G and the instantaneous / locally preserved scalar amount acquired by the instantaneous / locally preserved scalar amount acquisition means 7 into 29), the instantaneous and local temperature, density and other factors can be obtained. Calculate the required physical property values.

The index scalar amount is not limited to the one based on the above-mentioned G equation. For example, the document reported by the inventor of the present application (Nobuyuki 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, Japan Mechanical Society, [2016 Search on May 2, 2014], <URL: https://www.jstage.jst.go.jp/article/mel/2/0/2_16-00220/_article>) using the so-called level set method, etc. You may.

Next, the combustion flow analysis means 10 numerically analyzes the flow of the fuel, the oxidizing agent, and the combustion mixture with combustion using the instantaneous / local chemical reaction conditions and the instantaneous / local physical property values. ..

In the present embodiment, a large eddy simulation (LES) method is used as an analysis method for analyzing the flow. This large eddy simulation method is a simulation using a turbulent flow model that has been subjected to a process of spatially averaging turbulent vortices.

The basic equations of the large eddy simulation method in which the law of conservation of mass and the law of conservation of momentum are spatially filtered by applying the low Mach number approximation are expressed by the following equations (30) and (31). ..
... formula (30)
... Equation (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-represents the spatial average, the superficial ~ represents the spatial fable average (also called "density weight average"), and the subscript SGS represents the subgrid scale model constant that represents the effect of fluctuations below the spatial average. There is.

A standard Smagorinsky model was used as the SGS turbulence model. This model is expressed by the following equation (32).
,
,
... Equation (32)
Here, C _s is the Smagorinsky constant, Δ is the spatial filter width (analyzed lattice width), and S _ij having the above-mentioned ~ is a strain tensor.

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

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

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

Further, in the present embodiment, the following equation (36), which is a gradient diffusion model, is used for the second term on the right side of the above equation (35).
... Equation (36)

Further, the local turbulent combustion rate 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).
... Equation (37)
That is, the equation (37) considers the effect of increasing the actual flame area due to the deformation of SGS on the area of the GS flame surface coarse-grained by the spatial filtering of LES with respect to the SGS turbulent combustion rate S _SGS . Is for.

In this embodiment, the following equations (38) and (39) are used as the SGS turbulent combustion rate model.
,
... Equation (38)
,
... Equation (39)
_Further, the limit value of _S SGS / _{S L} is expressed by the following equation (40).
... formula (40)

Further, the above equations (27) to (29) expressing the mass fraction, temperature, and density in consideration of the index scalar amount G are expressed as the following equations (41) to (43).
... Equation (41)
... Equation (42)
... Equation (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 large eddy simulation method, and the DNS method (Direct Numerical Simulation) that directly solves the Navier-Stokes equation without using a model, the Reynolds average model, and the like are used. It can be appropriately selected from the method using the model of.

Next, the operation of each configuration and the combustion flow numerical analysis method in the combustion flow numerical analysis program 1a of the present embodiment will be described with reference to a functional block diagram showing the functions of each configuration shown in FIG. 6 and a flowchart shown in FIG. 7. ..

As shown in FIG. 7, first, the chemical reaction condition database creating means 6 acquires the chemical reaction conditions by numerical analysis using the stored scalar amount, stores them in the storage means 4, and creates the chemical reaction condition database 42. (Step S1). Hereinafter, the procedure for creating the chemical reaction condition database 42 by the chemical reaction condition database creating means 6 in the present embodiment will be described with reference to FIG.

The storage scalar amount setting unit 61 of the chemical reaction condition database creating means 6 has a mass fraction ξ of the fuel in the air-fuel mixture represented by the formula (1), a normalized enthalpy ξ _h of the mixed gas represented by the formula (6), and a formula ( Four types of storage scalar amounts are set: the ratio of carbon in the fuel shown in 11) ξ _c and the ratio of oxygen in the oxidizing agent shown in the formula (16) ξ _o (step S11). In the present embodiment, a general flame structure can be represented by setting these four types of storage scalar amounts.

Next, the storage scalar amount combination setting unit 62 sets an arbitrary combination of two types of storage scalar amount values, that is, the mass fraction ξ of the fuel 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 Am} is divided from A ₁ that can be assumed as the value of, and set as a combination thereof.

Next, the chemical reaction condition acquisition unit 63 determines the temperature of the thermal equilibrium state in each combination of the mass fraction ξ of the fuel in the air-fuel mixture and the ratio of carbon in the fuel ξ _c set by the storage scalar amount combination setting unit 62. The chemical reaction conditions including the density of the thermal equilibrium state and the mass combustion rate are obtained by performing a dimensionless reaction calculation based on the formulas (1) to (21) (step S13). In the present embodiment, since the density and mass combustion rate in the thermal equilibrium state are included as the chemical reaction conditions, the index scalar amount G in the instantaneous / local physical property value calculation means 9 can be calculated.

Then, the database creation unit 64 stores 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 means 4 (step S14). After creating the chemical reaction condition database 42 is completed in each combination of the percentage xi] _c carbon mass fraction xi] and in the fuel of the fuel in the air-fuel mixture, the process proceeds to the next step (return).

The instantaneous / locally preserved scalar amount acquisition means 7 instantly and locally obtains a numerical solution by coupling the conservation equations of the mass fraction ξ of the fuel in the air-fuel mixture and the ratio of carbon in the fuel ξ _c. Obtain the mass fraction ξ of the fuel in the air-fuel mixture and the instantaneous and local proportion of carbon in the fuel ξ _c (step S2).

Then, as shown in FIG. 6, the instantaneous / local chemical reaction condition calculation means 8 instantly and locally stores the scalar amount acquisition means 7 and the mass fraction ξ of the fuel in the air-fuel mixture and the instantaneous and local fuel. The chemical reaction conditions of the combination of the mass fraction ξ of the fuel in the air-fuel mixture and the carbon ratio ξ _{c in} the fuel, which are close to the combination of the instantaneous and locally preserved scalar amounts, while obtaining the carbon ratio ξ _c in the fuel. Is read from the chemical reaction condition database 42, and the instantaneous / 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 amount G by numerically analyzing the preservation equation of the index scalar amount G. Then, in the present embodiment, the instantaneous / local index scalar amount G and the instantaneous / locally preserved scalar amount acquired by the instantaneous / locally preserved scalar amount acquisition means 7 are substituted into the equations (41) to (43). Thereby, the instantaneous and local temperature, density and other necessary physical property values are calculated (step S4). As described above, 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.

Then, as shown in FIG. 6, the combustion flow analysis means 10 acquires the instantaneous / local chemical reaction conditions from the instantaneous / local chemical reaction condition calculation means 8 and the instantaneous / local physical properties from the instantaneous / local physical property value calculation means 9. Get the value. Then, using the acquired instantaneous / local chemical reaction conditions and instantaneous / local physical property values and the above equations (30) to (43), the flow accompanied by 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. 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. 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, it is not necessary to input the theoretical value or experiment, and various analyzes are performed. It becomes easy to apply to the object.
3. 3. The versatility of 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 in the following examples.

In Example 1, a test analysis was performed on laminar combustion using a mixture of methane and hydrogen as a fuel before applying the combustion flow numerical analysis program and the combustion flow numerical analysis method according to the present invention to an actual combustor. The main purpose of this numerical analysis was to confirm the operation of the code that implements the combustion flow numerical analysis program. Hereinafter, the numerical analysis conditions and the numerical analysis results in the first embodiment will be described.

<Analysis target>
As shown in FIG. 9, the analysis region is a rectangular plate-shaped combustion flow field having a x-axis direction of 400 mm, a y-axis direction of 100 mm, and a z-axis direction of 5 mm. The entire analysis region of this analysis region is formed by a plurality of analysis grids composed of hexahedral cubic lattices. The total number of elements of the analysis grid is 10,000, and the total number of contacts is 20402.

<Boundary condition>
Next, the 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 an oxidant flow in, and the other end surface at a symmetrical position of the inflow surface is an outlet surface (Outlet). In addition, the other four surfaces are heat insulating walls that do not allow heat and flow to enter and exit.

Since the inflow surface is a system in which gases having different compositions are supplied from multiple inlets, Inlet_Fuel that supplies pure fuel, Inlet_Air1 that supplies dry air as an oxidant, and fuel and air are mixed in advance in order from the bottom. It is composed of Inlet_Premixed that supplies the premixed air mixture and Inlet_Air2 that supplies the 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 composition of the supplied gas is the mass flow rate ratio.
Case A, 100% hydrogen as a fuel from Inlet_Fuel, 100% hydrogen as the burned premixed gas in stoichiometric ratio of dry air as methane and oxidant as fuel from Inlet_Premixed, dry as an oxidizing agent from Inlet_Air1 and Inlet_Air2 100% of air was supplied respectively.
Dry Case B, methane to 100% as the fuel from Inlet_Fuel methane 100% as burned premixed gas in stoichiometric ratio of dry air as methane and oxidant as fuel from Inlet_Premixed, as an oxidizing agent from Inlet_Air1 and Inlet_Air2 100% of air was supplied respectively.
Case C is methane 50% hydrogen 50% as the fuel from Inlet_Fuel methane 100% as burned premixed gas in stoichiometric ratio of dry air as methane and oxidant as fuel from Inlet_Premixed, from Inlet_Air1 and Inlet_Air2 100% dry air was supplied as an oxidizing agent.

In each case, the carbon ratio ξ _c in the fuel calculated based on the formula (11) is ξ _c = 0 in case A, ξ _c = 0.75 in case B, and ξ _c = 0. In case C. It is 375 . 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, 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 set.

Since the heat-insulated wall surface is in a condition where heat and flow do not enter and exit, it is set as a so-called slip condition where there is no heat gradient and velocity gradient.

As shown in Table 2 below, the ambient conditions were set to an ambient air pressure of 1.82 MPa, a fuel temperature of 298.15 K, and an oxidant temperature of 723.15 K (450 ° C.). The gas density was given an approximate value calculated by the prepared chemical reaction database. Assume an ideal gas and the standard state (1 atm, 25 ° C.) when converted to a gas density at the fuel case A is 0.089 kg / ^{m 3} in the case of 100% hydrogen. Similarly, when the fuel of Case B is 100% methane, it is 0.721 kg / m ³ . Further, when the fuel of Case C is 50% hydrogen and 50% methane, it is 0.145 kg / m ³ . And the oxidizing agent is 1.282 kg / m ³ .
(Table 2)

<Creation of chemical reaction condition database>
Next, the creation of the 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 combustion rate are calculated by numerical analysis as functions for the mixing fraction ξ and the carbon ratio ξ _c . Specifically, using the chemical reaction calculation software CHEMKIN-PRO15112 [18] (manufactured by Reaction Design (currently ANSYS, Inc.)), the dimensionless chemical equilibrium model shown in equations (1) to (21) is dimensionless. A detailed reaction calculation was performed. At this time, the database GRI-MECH3.0 published by the American Gas Association (GRI) was used for various physical property values in the chemical reaction.

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, temperature, density, and the calculation of the laminar burning velocity, the value of xi] _c 0 in 0.05 increments until 0.75, were prepared, respectively 16. 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.

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. 10 to 16. As shown in FIGS. 13 and 14, the density is described by the reciprocal of the specific volume.

The chemical reaction condition database in Example 1 is stored in the storage unit of the computer 1 that performs numerical analysis of the combustion flow, which will be described later, by approximating the polynomial as a function of ξ and ξ _c . The values between the tables are calculated by selecting the data to be interpolated. For example, the value when ξ _c = 0.33 is linearly interpolated by selecting the 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. Further, in the flow analysis in the first embodiment, considering that the laminar flow has a low flow velocity, a numerical analysis was performed by the DNS method for directly calculating the governing equation of the flow field without using the turbulent flow model.

The time step was 5.0 × 10 ^-4 s, and the Euler implicit method was used as the time integration method. The first-order windward difference was used for the advection term discretization scheme of the equation of motion and the conservative equation of the conserved scalar quantity. The SIMPLE method was used for the coupling of momentum and pressure, and the ICGC method was used for the pressure solution method.

<Physical property values used for combustion flow analysis>
The laminar Schmidt number σ _z used in the calculation of the conservative equations of the conserved scalar quantities Z and Z _c was set to σ _z = 1.0. The parameter σ _G corresponding to the laminar Prandtl number used in the calculation of the conservation equation of the index scalar amount _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 the 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 Infrastructure Research and Development Center was used as a computer for numerical analysis. The computer is a computer capable of performing two parallel calculations, and in the first embodiment, the calculation time was about 1 hour per 5000 steps.

<Combustion flow analysis results>
The analysis result shown below is an instantaneous value in the number of steps 50,000. 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 y = 0 mm to y = 100 mm, which is the central position with respect to the flow direction. The 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 map, the magnitude of each value is indicated by a color gradation.

Comparing Case A in which the fuel shown in FIG. 18 is 100% hydrogen and Case B in which the fuel is 100% methane, Case A tends to have a wider temperature region than Case B. That is, Case A shows that the burned region is wider than Case B, which is consistent with the numerical analysis result of the index scalar amount G shown in FIGS. 23 and 24.

Next, Case C, in which the fuel is a mixture of 50% hydrogen and 50% methane, shows almost the same distribution tendency as that of Case A of 100% hydrogen, and is in a region where the temperature is higher than that of Case B of 100% methane. Has become wider.

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

Next, the relationship between the temperature distributions 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 did not show a large difference between 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 mixed fraction ξ, which indicates the temperature in the thermal equilibrium state, differs depending on the carbon ratio ξ _c in the fuel. Therefore, it is considered that the difference is caused by the value of the carbon percentage xi] _c in the fuel with respect to the temperature distribution.

Therefore, we discussed with respect to the distribution of the carbon percentage xi] _c in the fuel. As shown in the upper and middle stages of FIG. 22 , in Case A in which the fuel is 100% hydrogen, ξ _c = 0 in the entire area. On the other hand, in case B in which the fuel is 100% methane, ξ _c = 0.75 in the entire area. Further, as shown in the lower part of FIG. 22, in Case C in which 50% hydrogen and 50% methane are mixed as fuel, it can be seen that the mass fraction Z _{C of} carbon C supplied from Inlet_Premixed and Inlet_Fuel is diffused. ..

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 air-fuel mixture is shown, the case where the value of the carbon ratio ξ _{c in} the fuel contains a large amount of hydrogen is smaller. It can be seen that the temperature of the adiabatic flame is high.

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

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

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

Further, as shown in FIG. 25, the difference in each case can be clearly seen by looking at the enlarged distribution map of the index scalar amount G near the inflow surface. For example, since the mass burn rate in hydrogen 100% of the case A ρ _u S _L is large, the length of the combustible is shorter than methane 100% of the case B. Further, in the case C of 50% hydrogen and 50% methane, the length of the flame is shortened as in the case A. From these facts, it can be seen that the hydrogen ratio affects the length of the flame.

Figure 26 shows the distribution of the mass burn rate [rho _u S _L of z-axis slice. As shown in FIGS. 15 and 16 of the chemical reaction condition database, the size of the mass burn rate [rho _u S _L is the xi] _c = 0, although there is a large difference between the ξ _c = 0.75, ξ the value of the mass burn rate [rho _u S _L when the fluctuation width of the _c value is small does not change significantly. In fact, comparing the 100% hydrogen cases A and methane 100% of the case B in FIG. 26, a large difference is seen in the value of the mass burning rate ρ _u S _L. The hydrogen 50%, the distribution of the mass burn rate [rho _u S _L methane 50% of the case C is greater than the case B is methane 100%.

Therefore, the difference in the mass burn rate [rho _u S _L between the case, is considered to have caused a difference in the distribution of indices scalar quantity G. It is also contemplated that the case A of 100% hydrogen increases already燃領zone because a large distribution of values of the mass burn rate [rho _u S _L than case B is 100% methane, becomes greater distribution of indices scalar quantity G ..

Next, the density distribution will be considered. As shown in FIGS. 13 and 14, the specific volume of 100% hydrogen ξ _c = 0 is larger. That is, it indicates that the density is low. Thus, the density as the ratio of the hydrogen value is reduced carbon percentage xi] _c in the fuel is increased is reduced.

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

Based on the above, in the first embodiment, numerical analysis is performed on laminar flow combustion using a mixture of methane and hydrogen as fuel, and combustion is performed by executing a code implementing a combustion flow numerical analysis program using the index scalar amount G. It was shown that the chemical reaction can numerically analyze the combustion flow in the non-equilibrium state.

In the second embodiment, the numerical analysis of the combustion flow for the actual combustion flow field was performed by using the code implementing the combustion flow numerical analysis program whose operation was confirmed in the first embodiment.

<Analysis target>
In the second embodiment, the combustor mounted on the 18 MW class gas turbine L20A developed by the applicant, Kawasaki Heavy Industries, Ltd., was analyzed. As shown in FIG. 29, the analysis area of the combustor is from the swirler (swivel) of the combustor to the buffer area added to the rear end of the combustor to prevent backflow.

As the analytical grid, a hexahedral structured grid was used throughout the interior of the combustor. The total number of elements in the analysis grid is 10025904, and the number of contacts is 10181403.

<Boundary condition>
In Example 2, an AFR value of about 42 under actual working conditions was used as the air-fuel ratio. Further, as shown in Table 3 below, the operating conditions were set to 25 ° C. for the fuel temperature, 450 ° C. for the air temperature, and about 1.8 MPa for the air inflow pressure according to the actual operating conditions.
(Table 3)

Further, as shown in FIG. 30, the premixture flows in from INLET-MAIN and INLET-PRIMARY, and fuel flows in from INLET-PILOT to stabilize the flame. In addition, air flows in from INLET-LINER. A premixture with different fuel concentrations and compositions flows in from INLET-SB depending on the conditions. Since unburned gas flows in from any of the inflow boundaries, the index scalar amount G is set to G = 0. In an actual combustor, fuel and air flow in from separate flow paths in front of the combustion chamber and are mixed in the flow path to the combustion chamber, so an inflow port for that purpose is also provided in the calculation area. In this analysis, the flow rate is adjusted from the air inlet in the experiment and flows in as a premixture. Moreover, each gas was assumed to be a uniform flow.

In the second embodiment, case 1 in which only methane is burned and case 2 in which methane and hydrogen are burned as fuel are analyzed and compared.

As shown in Tables 4 and 5 below, Case 1 and Case 2 both supplied a premixture 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. Further, 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 44% methane and 56% hydrogen (ξ _C = 0.33) in terms of mass fraction and supplied. As the oxidizing agent, dry air (oxygen: nitrogen = 21%: 79%) was used.
(Table 4)
(Table 5)

The ignition procedure is as follows: G = 0, which is unburned in the entire area, a flow field is formed (cold flow) between 2000 steps, and then G = 1, which is burned under the inflow condition INLET-MAIN, is given to ignite. 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 unburned G = 0. Subsequently, the number of steps was advanced to stabilize the flame, and in case 2 in which hydrogen was introduced, ξ _C = 0.33 was set at the inflow boundary INLET-SB at the 19000th step, which was a condition for supplying hydrogen.

<Chemical reaction condition database>
As the chemical reaction condition database in Example 2, the same database as that prepared in Example 1 was used.

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

The standard Smagorinsky model of Eq. (32) was adopted as the subgrit scale model of the large eddy simulation method, and the Smagorinsky constant was set to C _s = 0.1. The laminar Schmidt number σ _Z used when calculating the conservative equation of Z representing the mixed fraction of fuel and oxidizer and the conservative equation of 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. Further, the parameters σ _{G and SGS} corresponding to the number of turbulent Prandtl numbers used in the calculation of the conservation equation of the index scalar amount G were set to σ _{G and SGS} = 0.25. In order to consider the temperature dependence of the viscosity coefficient, Sutherland's formula represented by the following formula (45) was used.
... formula (45)

The parameters were set to reference temperature T ₀ = 298.15K, reference viscosity coefficient μ0 = 1.82 × ^10-5 kg / m / s, and Sutherland coefficient C = 110.4. The Euler implicit method is used for the time integration method, and the scalar combination of the second-order accuracy center difference method 95% and the first-order upwind difference method 5% is used for the translocation term discretization scheme of the conservative equation. A quadratic precision center difference was used for the translocation term discretization scheme of the equation. The SIMPLE method was used for the coupling of 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 the Information Infrastructure Research and Development Center of Kyushu University was used as a computer for numerical analysis. Further, in the second embodiment, the number of parallels was 128. Furthermore, the calculation time was about 6 hours per 1000 steps.

<Combustion flow analysis results>
The analysis results are shown below. FIG. 32 shows the instantaneous value of the temperature distribution in the z-axis cross section of the combustor shown in FIG. 31, and FIG. 33 shows the instantaneous value of the temperature distribution in the x-axis cross section of the combustor outlet shown in FIG. 31. In both cases 1 and 2, it can be seen that a high temperature region is formed in the central part of the combustor upstream of the boundary INLET-SB, which is the reheating burner of the combustor, and the temperature is low near the wall surface. ..

On the other hand, the temperature distributions of Case 1 in which only methane was used as fuel and Case 2 in which hydrogen was introduced were significantly different downstream from the reheating burner (INLET-SB) of the combustor.

Figure 34 is an instantaneous value distribution of the mass burn rate [rho _u S _L in the combustor z-axis slice. There is a large difference in distribution downstream from the reheating burner (INLET-SB) between case 1 using only methane as fuel and case 2 using hydrogen as fuel, but upstream from the reheating burner (INLET-SB). There is no difference in the distribution in the part of. As it can be seen from the distribution of carbon percentage xi] _c in the fuel in FIG. 35, reheating burner for (INLET-SB) there is no hydrogen in the upstream of the mass burning rate only on the downstream side of the reheating burner presence of hydrogen difference in ρ _u S _L is expected to be seen. Since there is no difference in the distribution of the mass fraction ξ of the fuel in the air-fuel mixture in both Case 1 and Case 2, this is due to the difference in the distribution of the carbon ratio ξ _{c in} the fuel due to the introduction of hydrogen. It is thought that it is. In fact, referring to the graph of FIG. 15 and FIG. 16 of the chemical reaction conditions database, in the place indicated the same xi] values it can be seen that the higher the mass burn rate ρ _u S _L ξ _c value includes a large amount of hydrogen is small becomes large. This can be seen that the value of the downstream mass burn rate [rho _u S _L from the fired burners follow by the introduction of hydrogen (INLET-SB) was significantly voted.

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 combustion rate ρ _{u SL} becomes large and it is easy to burn. That is, in Case 2 was fed hydrogen, reheating burner (INLET-SB) around and mass burn rate [rho _u S _L by the downstream in xi] _c value is increased hydrogen ratio decreases increases, easily burn As a result, as shown in FIG. 36, it is considered that the distribution of the burned index scalar amount G has also increased. In addition, it is considered that the region where the temperature is high has expanded due to the expansion of the burned G distribution.

As described above, it was possible to perform numerical analysis of the combustion flow for the actual combustion flow field by using the code disguised as the combustion flow numerical analysis program. In addition, as a result of the 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) in the downstream thereof. It was found that the high temperature region 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. The fuels and oxidants handled by numerical analysis are not limited to hydrogen, methane, and dry air. For example, hydrocarbon-based fuels are not limited to methane, but are polymer fuels such as ethylene (C ₂ H ₄ ) and cyclohexane (C ₆ H ₁₂ ) containing multiple bonds and cyclic structures, benzene rings, and gasoline. It may be. The fuel is not limited to hydrogen fuel and hydrocarbon fuel, but fuel containing oxygen element O such as methyl alcohol (CH ₃ OH) and sulfur such as ammonia (NH ₃ ) and sulfite (SO ₂ ). It may be a fuel containing element S or nitrogen element N. Further, the fuel and the oxidizing agent may contain vapor (water), carbon monoxide, an inert element such as argon, and the like.

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 creation means 7 Instantaneous / locally preserved scalar amount 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 61 Preserved scalar amount setting unit 62 Preserved scalar amount combination setting unit 63 Chemical reaction condition acquisition unit 64 Database creation unit

Claims (2)

A combustion flow numerical analysis program that numerically analyzes the flow of hydrogen fuel and / or hydrocarbon fuel and oxidizer with combustion.
A storage scalar amount setting unit for setting a storage scalar amount consisting of a mass fraction of elements and a normalized enthalpy based on each chemical composition in the fuel, the oxidizing agent, and a combustion mixture in which they are mixed, and a predetermined number of the above. The temperature in the thermal equilibrium state, the density in the thermal equilibrium state, and the mass combustion for each combination of the preserved scalar amount set by the preserved scalar amount combination setting unit for setting the combination with the preserved scalar amount as a variable. A chemical reaction condition database creation means having a chemical reaction condition acquisition unit for acquiring chemical reaction conditions including speed by numerical analysis and a database creation unit for storing the chemical reaction conditions in the chemical reaction condition database.
Instantaneous / locally preserved scalar quantity acquisition means for acquiring instantaneous / locally preserved scalar quantity by numerical analysis using the conservation equation of the preserved scalar quantity, and
Instantaneous / local chemical reaction condition calculation means for calculating instantaneous / local chemical reaction conditions using the chemical reaction conditions stored in the chemical reaction condition database and the instantaneous / locally preserved scalar amount, and
The non-equilibrium state of the combustion reaction is represented by a numerical value based on the rate of change from unburned gas to burned gas, and an index scalar amount indicating the flame plane position as a boundary separating the unburned gas side and the burned gas side. The instantaneous and local index scalar amount is calculated by numerically analyzing the differential equation that approximates the time variation and spatial distribution of, and is calculated as an algebra related to the physical property value expressed as a linearly combined value by the index scalar amount. Instantaneous and local index scalar amount and the calculated instantaneous and local chemical reaction conditions are substituted to calculate the instantaneous and local physical property values, and the instantaneous and local physical property value calculating means.
Numerical combustion flow analysis that makes a computer function as a combustion flow analysis means for numerically analyzing the flow of the fuel, the oxidant, and the combustion mixture with combustion using the instantaneous / local chemical reaction conditions and the instantaneous / local physical property values. program. A combustion flow numerical analysis method for numerically analyzing the flow of hydrogen fuel and / or hydrocarbon fuel and oxidant with combustion.
A storage scalar amount setting step for setting a storage scalar amount consisting of a mass fraction of elements and a normalized enthalpy based on each chemical composition in the fuel, the oxidizing agent, and a combustion mixture in which they are mixed, and a predetermined number of the above. The temperature in the thermal equilibrium state, the density and mass combustion in the thermal equilibrium state for each combination of the preserved scalar amount set by the preservation scalar amount combination setting step for setting the combination in which the preservation scalar amount is a variable and the preservation scalar amount combination setting step. A chemical reaction condition database creation step having a chemical reaction condition acquisition step for acquiring chemical reaction conditions including speed by numerical analysis and a database creation step for storing the chemical reaction conditions in the chemical reaction condition database, and a chemical reaction condition database creation step.
The instantaneous / locally preserved scalar quantity acquisition step of acquiring the instantaneous / locally preserved scalar quantity by numerical analysis using the conservation equation of the preserved scalar quantity, and
The instantaneous / local chemical reaction condition calculation step for calculating the instantaneous / local chemical reaction condition using the chemical reaction condition stored in the chemical reaction condition database and the instantaneous / locally preserved scalar amount, and
The non-equilibrium state of the combustion reaction is represented by a numerical value based on the rate of change from unburned gas to burned gas, and an index scalar amount indicating the flame plane position as a boundary separating the unburned gas side and the burned gas side. The instantaneous and local index scalar amount is calculated by numerically analyzing the differential equation that approximates the time variation and spatial distribution of, and is calculated as an algebra related to the physical property value expressed as a linearly combined value by the index scalar amount. The instantaneous / local physical property value calculation step for calculating the instantaneous / local physical property value by substituting the instantaneous and local index scalar amount and the calculated instantaneous / local chemical reaction condition , and
A combustion flow numerical analysis method including a combustion flow analysis step for numerically analyzing the flow of the fuel, the oxidant, and the combustion mixture with combustion using the instantaneous / local chemical reaction conditions and the instantaneous / local physical property values.