KR101022734B1 - Method for measurementing the richness combustion burning gas - Google Patents

Abstract

The present invention relates to a method for calculating a rich combustion gas, and in particular, an object of the present invention is to predict the non-equilibrium chemical reaction combustion characteristics of a gas generator in which rich combustion proceeds.

The present invention for achieving this characteristic object is the input module 10 receiving the O / F ratio, temperature information and time information, the thermodynamic module 20 for determining the thermodynamic properties for each chemical species, and the PSR code In the rich combustion calculation apparatus 100 is composed of a PSR code module 30 for generating and modifying, an application calculation module 40, and an output module 50 for outputting the rich combustion calculation value so that the user can check. A first step of separating the chemical reaction temperature into a reaction temperature (T _C ) and a reactor temperature (T _HOT ); Calculating a evaporation time according to fuel evaporation; A third step of calculating a mass fraction using the residence time and the initial temperature; And a fourth step of calculating the rich combustion value when the solution converges. Do this.

Complete mixing reactor, gas generator, fuel enrichment, non-equilibrium reaction, evaporation time, residence time, gas properties

Description

Method for calculating rich combustion gas {Method for measurementing the richness combustion burning gas}

 1 is a block diagram showing the configuration of a combustion compound reactor according to an embodiment of the present invention;

2 is an overall flowchart showing a method for calculating the rich combustion gas according to an embodiment of the present invention;

3A is a graph showing a reactor temperature according to a change in reaction temperature according to an embodiment of the present invention;

Figure 3b is a graph showing the residence time according to the change in the reaction temperature according to an embodiment of the present invention,

4 is a graph showing the evaporation time according to the droplet size according to an embodiment of the present invention,

5 is a graph comparing the non-equilibrium combustion temperature according to the comparative example,

Figure 6a is a graph comparing the CO mole fraction according to the comparative example,

6B is a graph comparing the H ₂ mole fraction according to the comparative example,

Figure 6c is a graph comparing the CH ₄ mole fraction according to the comparative example,

6d is a graph comparing the CO ₂ mole fraction according to the comparative example,

6E is a graph comparing the C ₂ H ₄ mole fraction according to the comparative example,

6F is a graph comparing the C ₃ H ₆ mole fractions according to the comparative example,

7 is a graph comparing the combustion gas molecular weight according to a comparative example,

8 is a graph comparing the specific heat ratio of the combustion gas according to the comparative example.

** Description of symbols for the main parts of the drawing **

100: rich combustion calculation device

10: input module 20: thermodynamic module

30: PSR code module 40: applied calculation module

50: output module

The present invention relates to a method for calculating the rich combustion gas, and more particularly, to a method for calculating the rich combustion gas that can predict the non-equilibrium chemical reaction combustion characteristics of a gas generator that is subjected to rich combustion.

A typical gas generator aims to produce high-enthalpy flue gas to drive a turbine connected to a pump in a liquid rocket engine, using some of the main propellant (1-5%). In addition, the gas generator uses rich or lean combustion to reduce the thermal load of the turbine blades and maintains the combustion temperature at 800 ~ 1,200K. However, if the combustion is incomplete and heat concentration occurs near the combustion chamber wall or injector, excessive heat damage may occur, and soot may be generated due to rich combustion, thereby degrading turbine blade performance.

In addition, ramjet engines using ejectors exhibit very similar operating characteristics to gas generators in liquid rockets. In detail, when the solid rocket installed in the ejector is rich in combustion and expands through the nozzle, air flow is sucked into the ejector due to the fast exhaust gas flow rate. Since the air passed through the ejector is mixed with the exhaust gas and is sucked into the main combustion chamber to combust with the secondary fuel injection, it is very important to predict the exhaust gas temperature and the gas properties to predict the performance of the ramjet engine. .

However, as described above, the prediction of the combustion characteristics of the gas generator should be essential for designing the turbopump system and for predicting its performance. However, it was very difficult to predict the combustion characteristics of a gas generator in which the non-equilibrium reaction occurs mainly.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to enable prediction of non-equilibrium combustion chemical reactions using non-normal equations and governing equations.

And, using the PSR code, it is possible to predict the non-peaceful chemical reaction combustion characteristics of the gas generator in which rich combustion proceeds.

In order to realize the technical features as described above, the present invention provides an input module 10 for receiving an O / F ratio, temperature information, and time information, a thermodynamic module 20 for determining thermodynamic properties for each chemical species, The rich combustion calculation apparatus 100 including a PSR code module 30 for generating and modifying a PSR code, an application calculation module 40, and an output module 50 for outputting the rich combustion calculation value to a user. In the first step of separating the chemical reaction temperature by the reaction temperature (T _C ) and the reactor temperature (T _HOT ); Calculating a evaporation time according to fuel evaporation; A third step of calculating a mass fraction using the residence time and the initial temperature; And a fourth step of calculating the rich combustion value when the solution converges. Do this.

Preferably, before the first step, a pre-treatment step of removing impurities so that gaseous fuel and oxidant can be introduced into the reactor; Characterized in further performing.

Also preferably, the second process may include setting a reactor temperature according to a change in reaction temperature; Setting a residence time according to the set reactor temperature; And calculating an evaporation time according to the kerosene component droplet size; Characterized in further performing.

Also preferably, the fourth process is characterized by calculating the rich combustion value using the governing equation.

Also preferably, the fourth process may include calculating an evaporation time when the solution does not converge; And modifying the function value; Characterized in further performing.

And preferably, the fourth process sets the converged solution as an initial estimate and calculates a rich combustion value through a non-normal equation.

The features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings. In the meantime, when it is determined that the detailed description of the known functions and configurations related to the present invention may unnecessarily obscure the subject matter of the present invention, it should be noted that the detailed description is omitted.

For reference, several researchers suggested a kerosene model fuel, but the present invention used a detailed chemical reaction model consisting of 207 species and 1592 reversible reaction schemes proposed by Dagaut, and kerosine was expressed as n by volume. -decane 74%, n-propyl benzene 15%, and n-propylcyclohexane 11% was set.

On the other hand, the calculation for the combustion reaction was complete mixing reactor, was used to modify the code PSR applying the assumption (P erfectly S tirred R eactor hereinafter referred to as 'PSR'). In this case, the complete mixing reactor refers to a virtual reactor in which the fuel and the oxidant are formed and combusted as soon as the gas is introduced into the gas. Therefore there is no temperature gradient over time and no evaporation of the droplet fuel is taken into account. This is the net time that the mixer reacts, since no mixer is produced while the fuel is evaporating, minus the evaporation time required for fuel evaporation from the total residence time.

In addition, in calculating the rich combustion by using the PSR, in a real gas generator, a combustible mixture is formed near the injector, and combustion starts and propagates the combustion to other parts. However, the PSR hypothesis ignores this spatial temperature gradient and has the disadvantage that the calculation using the PSR is not possible for the combustible mixture below a certain O / F (oxygen / fuel) ratio. Therefore, as a method to consider the combustion by the combustor, it was calculated by separating the reactor temperature obtained from the energy equation and the chemical reaction temperature of the Arrenhenius term.

Through the present invention, using the detailed chemical reaction of kerosene proposed by Dagaut and calculating the fuel evaporation time, the mixer residence time was modified in consideration of this. The PSR code was modified by distinguishing the temperature of the theoretical chemical reaction zone in which the flame kernel was present from the temperature of the reactor obtained from the energy equation. The modified code can predict the non-equilibrium chemical reaction combustion characteristics of the gas generator with rich combustion, and the results are compared with the experimental data to verify its performance.

Specifically, Figure 1 is a block diagram showing the configuration of the combustion compound reactor according to an embodiment of the present invention, the rich combustion calculation apparatus 100 input module 10 receiving the O / F ratio, temperature information and time information ), A thermodynamic module 20 for determining thermodynamic properties for each chemical species, a PSR code module 30 for generating and modifying a PSR code, an application calculation module 40, and a rich combustion calculation value. It consists of an output module 50 for outputting to check.

In this case, the temperature information included in the input module 10 is set to include the reactor temperature (T _HOT ), the reaction temperature (T _C ), the time information is set to include the residence time, the evaporation time of the droplets (液滴) However, the present invention is not limited thereto.

On the other hand, the application calculation module 40 performs a function of determining whether the PSR code is converged using the governing equation. Specifically, correction of the residence time is performed in consideration of the droplet evaporation time, and the value of T _HOT which keeps the chemical reaction temperature constant is calculated.

Hereinafter, a calculation method using the rich combustion gas calculating device through the application software having the above-described configuration will be described with reference to FIGS. 2 to 4.

2 is an overall flow chart showing a method for calculating the rich combustion gas according to an embodiment of the present invention, Figure 3a is a graph showing the reactor temperature according to the change in the reaction temperature according to an embodiment of the present invention, Figure 3b 4 is a graph showing the residence time according to the change of the reaction temperature according to an embodiment of the present invention, Figure 4 is a graph showing the evaporation time according to the droplet size according to an embodiment of the present invention.

In this example, the O / F (mixing ratio) of kerosene and oxygen is 0.38, the combustion pressure is 50 atm, the mass flow rate is 16.8 kg / sec, the reactor volume is 5,092.57 cc, and the diameter of the fuel droplets is Although it is set to 50 m, it is set experimentally, it will be obvious that the present invention is not limited to these numerical values.

First, the rich combustion calculation apparatus 100 performs a pretreatment process so that the gaseous fuel and the oxidant may be introduced into the reactor (S2).

That is, the rich combustion calculating device removes impurities in the complete mixing reactor so that the introduced fuel and the oxidant are ideally mixed and reacted.

In this case, it is assumed that the temperature and the gas physical properties are spatially constant, and the mass conservation equation is represented by Equation 1 below.

여기서,

은 질량유동이고,

는 질량분율(mass fraction)이며,

는 화학반응에 의하여 생성되는 단위 부피당 몰 생성량(Molar production rate per unit volume)이고,

는 분자량(Molecular weight of species k)이며,

는 반응기 부피(reactor volume,cm³)를 나타낸다.

here,

Is the mass flow,

Is the mass fraction,

Is the molar production rate per unit volume produced by the chemical reaction,

Is the molecular weight of species k,

Denotes the reactor volume (cm ³ ).

And the energy conservation equation is expressed as Equation 2.

여기서,

은 질량유동이고,

는 질량분율(mass fraction)이며,

는 비 엔탈피(specific enthalpy per unit mass)이고,

는 반응기 열손실(reactor heat loss)을 나타낸다.

here,

Is the mass flow,

Is the mass fraction,

Is specific enthalpy per unit mass,

Denotes reactor heat loss.

Here, the superscript ( ^* ) means the entry condition.

Next, the rich combustion calculating device 100 separates the chemical reaction temperature (S4).

The chemical reaction temperature distinguishes the reaction temperature from the reactor temperature. The reaction temperature is used to distinguish the reaction temperature from the reactor temperature in order to consider the flame nucleus existing inside the gas generator.

This means that the reactor formed near the injector forms a flame nucleus, and the combustion temperature propagates from the flame nucleus to the surrounding so that the reactor temperature and the temperature at which the chemical reaction occurs have different values. In this embodiment, the two temperatures are divided and used in consideration of the temperature difference. Thus, using each of the two temperatures, it is possible to calculate combustion for the rich mixer using a modified PSR code.

The temperature at which the chemical reaction proceeds is the reaction temperature (T _HOT ), which is used separately from the average temperature of the reactor, and the temperature of the reactor is obtained from the solution of the energy equation (T _C ).

Next, the rich combustion calculation apparatus 100 calculates the evaporation time according to the fuel evaporation (S6).

Looking at the step S6 in detail, first, the rich combustion calculation apparatus 100 sets the reactor temperature according to the change in the reaction temperature (S6a).

Referring to Figure 3a, when the reaction temperature is 1,400 and 1,500K reactor temperature is the maximum.

The rich combustion calculation apparatus 100 sets the residence time according to the set reactor temperature (S6b).

At this time, since the minimum residence time is shown at the reaction temperature of 1,500K, the reaction temperature is preferably fixed at 1,500K in the following calculation.

That is, the reactor temperature and residence time obtained when the reaction temperature is changed as shown in Figure 3b can be calculated. In general, when a chemical reaction occurs to form a flame nucleus, the temperature is the same as when the mixer burns. Therefore, the reaction temperature should be selected to maximize the reactor temperature. In addition, since the reactor temperature is the maximum at this time, it can be seen that the residence time of the mixer staying in the reactor is the shortest.

The rich combustion calculating device 100 calculates an evaporation time according to the kerosene component droplet size (S6c).

In this case, kerosene means a petroleum component produced at a higher boiling temperature (150 ~ 300 ㅀ) after gasoline when refining crude oil.

In this embodiment, the evaporation time was calculated using a composite fuel consisting of three components. As shown in Figure 4, Propyl cyclohexane evaporation time is the longest. However, the change of evaporation time according to the temperature of each component is not so large, especially when the droplet diameter is less than 100μm, the change of evaporation time with temperature is negligibly small.

Next, the rich combustion calculating device 100 calculates a mass fraction using the residence time and the initial temperature (S8).

The rich combustion calculation apparatus 100 determines whether the solution converges using a governing equation (S10).

로 표현되고,

와 같이 온도와 질량분율을 나타낸다.First, we use the function vector F to determine whether the solution converges.

Represented by

Temperature and mass fraction are shown as follows.

)을 산출한다(S12).As a result of the determination in step S10, when the solution values converge, the rich combustion calculating apparatus 100 determines the rich combustion value (

) Is calculated (S12).

In other words, as shown above, a fully mixed reactor does not depend on time, but solves an intentional time-dependent problem in the process of inferring and converging a solution and uses that solution as an initial estimate. In this case, the non-transient equation is Is expressed as in Equations 3 and 4.

여기서,

은 질량유동이고,

는 질량분율(mass fraction)이며,

는 화학반응에 의하여 생성되는 단위 부피당 몰 생성량(Molar production rate per unit volume)이고,

는 분자량(Molecular weight of species k)이며,

는 반응기 부피(reactor volume,cm³)이고,

는 비 엔탈피(specific enthalpy per unit mass)이며,

는 반응기 열손실(reactor heat loss)을 나타낸다.

here,

Is the mass flow,

Is the mass fraction,

Is the molar production rate per unit volume produced by the chemical reaction,

Is the molecular weight of species k,

Is the reactor volume (cm ³ ),

Is a specific enthalpy per unit mass,

Denotes reactor heat loss.

 The governing equations consist of K + 1 nonlinear algebraic equations, and the non-normal equations for estimating estimates constitute K + 1 non-linear differential equations.

) 화학종의 순 생성을 의미하며 화학 반응은 다음의 수학식 5와 같이 표현된다.For reference, the species generation term is (

) Refers to the net generation of chemical species and the chemical reaction is expressed as in Equation 5 below.

여기서,

와

는 각각 i번째 반응식에서 k성분 화학종을 포함하는 반응물과 생성물의 이론반응계수(stoichiometric coefficients)이고,

는 k번째 성분의 몰수를 나타낸다.

here,

Wow

Are the stoichiometric coefficients of the reactants and products each containing the k component species in the i scheme,

Denotes the number of moles of the k-th component.

) 은

이고, V_ki는 순 몰수 변화를 나타내고, q_i는 진행변수를 나타낸다. 순 몰수 변화는

이며, 진행변수 q_i는

의 관계식을 갖는 것이 바람직하다. 이때, 진행변수 q_i에서 k_fi는 정반응 상수이고, k_ri는 역반응 상수이며,

는 k번째 성분의 몰수이다.At this time, the following three equations are used to simply express the net generation rate of each species.
Chemical species generation term (

) Is

Where V _ki represents the net mole number change and q _i represents the progression variable. Net forfeiture change

Where the progress variable q _i is

It is preferable to have a relation of. In this case, k _fi is a forward reaction constant, k _ri is a reverse reaction constant in the progress variable q _i ,

Is the number of moles of the kth component.

는 Arrhenius 법칙에 의하여 다음의 수학식 6과 같이 표현된다.The positive reaction constant

Is expressed by Equation 6 below by the Arrhenius law.

The inverse reaction constant may be calculated by using the equilibrium constant calculated through the given temperature and pressure and the above Equation 6, which is expressed by Equation 7 below.

This is used to avoid inverse the function.

On the other hand, when the determination result of the step S10, the solution value does not converge, the rich combustion calculation apparatus 100 calculates the evaporation time (S14).

When a fuel droplet of a constant diameter is introduced into an environment made of an oxidant, the life time of the droplet is expressed by Equation 8 below.

여기서, τ_l은 액적의 증발시간(nominal droplet lifetime, msec)이고, d_o는 초기 액적의 지름(nominal initial droplet diameter, cm)이며, λ는 열전도도(Gas phase thermal conductivity)이고, B는 스팔딩 전달수(Spalding transfer number)이며, c_p는 정압비열(specific heat of gas)이고, ρ_l은 액적의 밀도(liquid density)이다.

Where τ _l is the nominal droplet lifetime (msec), d _o is the nominal initial droplet diameter (cm), λ is the gas phase thermal conductivity, and B is spalding Spald transfer number, c _p is the specific heat of gas, and ρ _l is the liquid density.

로 표현된다.Where B is the Spalding transfer number

It is expressed as

For reference, considering fuel evaporation affects the combustion calculation in two ways: The first is the heat loss of the combustor used for fuel evaporation, and the second is the reduction due to evaporation time at the total residence time since no combustion occurs during fuel evaporation. In order to consider the reduction of the reactor temperature due to evaporation, the temperature T∞ represented in the above-described relation of the Spalding transfer number was taken as the reactor temperature. The evaporation time was assumed to represent the largest value among the model fuel components. Therefore, the modified residence time of the mixer for a given mass flow rate is given by the following equation (9).

However, it represents the minimum reaction time considering evaporation and is established only when evaporation time is smaller than residence time. If the evaporation time is greater than the residence time of the reactor, non-physical phenomena have other effects of promoting evaporation, but this study does not consider combustion in this case.

Next, the rich combustion calculating device 100 modifies the function value by using Equation 10 (S16).

After modifying the function value, the process returns to step S8 to perform an iterative step using Equation 11 until the solution values converge.

Hereinafter, with reference to the experimental example and the accompanying drawings, it looks at the various techniques that were considered in order to calculate the rich combustion gas prediction results of the present invention created by the present invention in sequence and through this the rich combustion gas prediction apparatus Look closely at whether you have

EXAMPLES Experiment]

As an experimental example, a high pressure gas generator was designed based on the prediction of unbalanced combustion temperature. In the experimental example, the combustion pressure was set to 150 atm, the mixing ratio (O / F) to 0.38, the droplet diameter to 50 μm, the mass flow rate to 16.8 kg / s, and the reactor volume to 5,092.57 cm ³ .

At this time, since the combustion pressure of 150 atm is outside the pressure range to which Dagaut's detailed chemical reaction model is applied, the calculation was performed assuming the combustion pressure at 50 atm.

The reactor temperature predicted as shown in FIG. 5 shows the same trend as the temperature gradient with respect to the O / F ratio when compared with the experimental results, but shows a temperature as low as about 60K.

However, when the pressure applied to the present invention is 50 atm, and the pressure applied to the experimental example is 150 atm, it is judged as a possible error.

6A to 6F are results of calculating mole fractions of CO, H ₂ , CH ₄ , CO ₂ , C ₂ H ₄ , and C ₃ H _{6 in} the combustion gas components, and are graphs compared with the experimental results, respectively. As shown in the figure, it can be seen that most components except for CO are well predicted. CO is a component of incomplete combustion, and in non-equilibrium combustion such as gas generators, a large amount is emitted and is closely related to soot generation. However, in the present experimental example, since it does not consider soot generation, it is judged that CO generation cannot be accurately predicted, and the study accordingly should be further progressed.

For reference, at 150 atmospheres, the pressure of the experiment, the droplets are supercritical, resulting in a completely different pattern of droplet evaporation. Therefore, there is a limit to the expression with the current droplet evaporation model.

On the other hand, in addition to the combustion gas components, the average molecular weight of the combustion gas, the specific heat ratio, etc. are very important factors in designing a turbopump or predicting the main combustion performance as in Remjet.

Looking at comparing the molecular weight of the combustion gas with reference to Figure 7, the molecular weight according to the experimental results shows a tendency to decrease as the O / F ratio increases. Compared with the present invention, not only small values but also almost no change appear depending on the O / F ratio change.

Next, referring to FIG. 8, when comparing the specific heat ratio of the combustion gas, the specific heat ratio calculated in the experiment with respect to the increase in the O / F ratio is similar to the prediction of the molecular weight, but the prediction value shows a decreasing tendency.

Comparing the comparative examples as described above, most of the compositions except for CO components are predicted very well, and the molecular weight and specific heat ratio show an error of less than 10% at an O / F ratio of 0.35 or more. However, as described above, since the experiment according to the present comparative example was performed at 150 atm and the calculation was performed at 50 atm, it is obvious that some error may occur.

According to the present invention described above, in order to predict the non-equilibrium chemical reaction of the rich gas generator, by applying the detailed chemical reaction model and the complete reactor (PSR) combustion model of 207 species, 1592 chemical reaction stage developed by Dagaut, Although the instrument does not predict soot, the calculation results have the effect of predicting not only the combustion gas temperature but also the gas properties.

As described above and described with reference to a preferred embodiment for illustrating the technical idea of the present invention, the present invention is not limited to the configuration and operation as shown and described as described above, it is a deviation from the scope of the technical idea It will be understood by those skilled in the art that many modifications and variations can be made to the invention without departing from the scope of the invention. Accordingly, all such suitable changes and modifications and equivalents should be considered to be within the scope of the present invention.

Claims (6)

An input module 10 that receives O / F ratio, temperature information and time information, a thermodynamic module 20 for determining thermodynamic properties for each chemical species, and a PSR code module 30 for generating and modifying a PSR code. In the rich combustion gas calculation method using a rich combustion calculation device comprising an output module 50 for outputting so that the user can check the rich combustion calculation value, the application calculation module 40, A first process of separating a chemical reaction temperature into a reaction temperature (T _C ) and a reactor temperature (T _HOT ); Calculating a evaporation time according to fuel evaporation; A third step of calculating a mass fraction using the residence time and the initial temperature; And A fourth step of calculating the rich combustion value when the solution converges; Rich combustion gas calculation method characterized in that for performing. The method of claim 1, Before the first process, Pretreatment to remove impurities so that gaseous fuel and oxidant may enter the reactor; Rich combustion gas calculation method characterized in that to perform more. The method of claim 1, The second process, Setting a reactor temperature according to a change in reaction temperature; Setting a residence time according to the set reactor temperature; And Calculating evaporation time according to the kerosene component droplet size; Rich combustion gas calculation method characterized in that to perform more. The method of claim 1, The fourth process, A rich combustion gas calculation method comprising calculating a rich combustion value using a governing equation. The method of claim 1, The fourth process, Calculating an evaporation time if the solution does not converge; And Modifying function values; Rich combustion gas calculation method characterized in that to perform more. The method of claim 1, The fourth process, And setting the converged solution as an initial estimate, and calculating a rich combustion value through a non-normal equation.

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