A method for constructing a mixing chamber airflow mixing characteristic map

Abstract

The application is a kind of construction method of mixing chamber airflow mixing characteristic map, belonging to the field of fluid mechanics; based on the test data or CFD simulation data of mixing chamber, combined with the mixing mechanism of mixing chamber, the composite flow ratio and the composite pressure ratio are first constructed to replace the flow ratio and the pressure ratio in the characteristic map, thereby greatly reducing the nonlinearity of the characteristic map. Selecting the specified characteristic data as the reference, using the method of combining the first function and the second function, the characteristic fitting method based on the reference data is established, and the optimization algorithm is used to optimize the proportion coefficient and the exponential coefficient in the composite flow ratio and the composite pressure ratio, so that the explicit high-precision expression of the mixing chamber airflow mixing characteristic map can be realized. The construction method of the mixing chamber airflow mixing characteristic map of the application can construct the high-precision characteristic map representing the key performance of the mixing chamber based on the low-order function with a small amount of sample data, thereby solving the problem of low model precision caused by the modeling assumptions of the traditional mixing chamber theoretical model.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of fluid mechanics, and particularly relates to a method for constructing a gas flow mixing characteristic map of a mixing chamber. BACKGROUND

[0002] Gas flow mixing is a common phenomenon in nature, and mixing chambers for gas flow mixing are widely used in aerospace, vehicles, energy, medicine and other industries. The flow ratio and pressure ratio of gas flow mixing are two key performance parameters of the mixing chamber, and the zero-dimensional high-precision modeling of the performance parameters has been a difficulty in the field of fluid mechanics.

[0003] In the Journal of Aerospace Power, Vol. 38, No. 5, 2023, Performance Modeling and Simulation of Dual-Containment Combined Exhaust Variable Cycle Engine, formula (13)-(15) on page 1116 establishes a zero-dimensional theoretical model of the mixing chamber using the laws of conservation of mass, energy and momentum. The model assumes that the two incoming flows of the mixing chamber are parallel mixing, the static pressure is equal and the outlet flow is uniform. This assumption is only applicable to simple gas flow mixing scenarios and is not suitable for the complex mixing of the new concept engine in the literature. In addition, the area used in the zero-dimensional theoretical model is the aerodynamic area, however, for most mixing scenarios, the profile design of the mixing chamber is complex in order to improve the mixing efficiency, making it difficult to give accurate mixing cross-section and mixing aerodynamic area, and the mixing cross-section and aerodynamic area will also change with the change of aerodynamic parameters. At the same time, the zero-dimensional model cannot consider the influence of the profile design of the mixing chamber on its performance (i.e. the performance parameters calculated by the zero-dimensional model are theoretical parameters), so it cannot reflect the performance difference between different configurations of the mixing chamber. The development of the zero-dimensional model of the fluid mechanics field for the mixing of two gas flows has been insufficient, so most complex mixing scenarios in various industries use the zero-dimensional theoretical model in the above literature. Although some researchers use machine learning and other methods to establish a proxy model of the performance parameters of the mixing chamber, there are generally problems of large data requirement for modeling and low modeling accuracy. Moreover, the proxy model established by using machine learning and other methods pays insufficient attention to the mixing mechanism of the mixing chamber, so that the generalization ability of the model is weak, and the explicit expression form of the proxy model cannot be given.

[0004] In summary, the present application first proposes a method for constructing a gas flow mixing characteristic map of a mixing chamber. SUMMARY

[0005] The technical problem to be solved is:

[0006] In order to avoid the shortcomings of the prior art, the present application provides a mixed chamber airflow mixing characteristic map construction method, which is based on the test data or CFD simulation data of the mixed chamber, combined with the mixing mechanism of the mixed chamber, and first gives the construction method of the explicit expression form of the flow ratio, pressure ratio of the mixed chamber, and the geometric adjustable parameters and aerodynamic parameters of the mixed chamber, and finally forms the airflow mixing characteristic map representing the aerodynamic performance of the mixed chamber. Based on the mixing characteristic map, the key performance parameters of the mixed chamber can be calculated, thereby solving the problem of low model precision caused by the modeling assumptions of the traditional mixed chamber theoretical model.

[0007] The technical scheme of the present application is: a mixed chamber airflow mixing characteristic map construction method, the mixed chamber introduces two airflows from the inlet, and determines the mixing position through the adjustable mechanism installed in the mixed chamber, and the mixed airflow flows out from the outlet of the mixed chamber; characterized in that the specific steps are as follows:

[0008] In the case that the position of the adjustable mechanism of the mixed chamber is fixed, the test data or CFD simulation data of the mixed chamber are arranged into the mixed chamber mixing characteristic map regular format of the flow ratio and the outlet pressure ratio changing with the outlet static pressure / first incoming total pressure ratio under different incoming total pressure ratios of the two airflows;

[0009] The composite flow ratio and the composite pressure ratio are constructed, and the flow ratio and the outlet pressure ratio in the mixed chamber mixing characteristic map regular format are replaced, to obtain the mixed chamber mixing characteristic map reconstruction format;

[0010] Based on the mixed chamber mixing characteristic map reconstruction format, the reference data are selected, and the variation law curve of the composite flow ratio and the composite pressure ratio respectively with the reference data ratio changing with the inlet two-airflow incoming total pressure ratio under different outlet static pressure / first incoming total pressure ratios is calculated;

[0011] The variation law curve is fitted by a first-order function;

[0012] The linear fitting coefficient in the first-order function is fitted by a second-order function according to the variation curve of the linear fitting coefficient changing with the outlet static pressure / first incoming total pressure;

[0013] Based on the reference data, the linear fitting coefficient and the quadratic fitting coefficient, the fitting values of the composite flow ratio and the composite pressure ratio are calculated;

[0014] According to the fitting values of the composite flow ratio and the composite pressure ratio, the fitting values of the flow ratio and the pressure ratio are calculated;

[0015] The proportion coefficient and the exponential coefficient in the composite flow ratio and the composite pressure ratio are optimized, so that the average error between the original value and the fitting value of the flow ratio and the pressure ratio is minimized;

[0016] For different adjustable mechanism positions of the mixed chamber, the above steps are repeated to establish the mixed chamber mixing characteristic map under different adjustable mechanism positions.

[0017] The further technical solution of the present application is that the expression of the flow ratio in the general format of the mixing chamber mixing characteristic map is: The expression of the outlet pressure ratio is Wherein, represents the gas flow, T * represents the total temperature, p * represents the total pressure, p represents the static pressure, and subscripts 1, 2 and out represent the first incoming flow, the second incoming flow and the outlet respectively.

[0018] The further technical solution of the present application is that the composite flow ratio m c and the composite pressure ratio p c The expressions are respectively:

[0019]

[0020]

[0021] In the formula, a1, a2, a3, b1, b2 are proportional coefficients, and k1, k2, n1, n2 are exponential coefficients.

[0022] The further technical solution of the present application is that the initial values of the proportional coefficient and the exponential coefficient are randomly selected in the interval [0.5, 5], and are adjusted to the optimal value through the optimization algorithm.

[0023] The further technical solution of the present application is that the reference data is the composite flow ratio and the composite pressure ratio corresponding to the minimum two gas flow incoming flow total pressure ratio, that is, the reference composite flow ratio and the reference composite pressure ratio;

[0024] The ratio of the composite flow ratio to the reference composite flow ratio is

[0025]

[0026] The ratio of the composite pressure ratio to the reference composite pressure ratio is

[0027]

[0028] The further technical solution of the present application is that the reference data is numerically extended by a quadratic extrapolation method.

[0029] The further technical solution of the present application is that the expression of the one-time function fitting of the change law curve is as follows:

[0030]

[0031]

[0032] In the formula, k m , bm , k p , b p is a linear fitting coefficient.

[0033] A further technical solution of the present application is that the linear fitting coefficient is expressed by a quadratic function as follows:

[0034]

[0035]

[0036]

[0037]

[0038] In the formula, c1-c 12 is a quadratic fitting coefficient.

[0039] A further technical solution of the present application is that the fitting value calculation formula of the composite flow ratio and the composite pressure ratio is as follows:

[0040]

[0041]

[0042] A further technical solution of the present application is that the fitting value calculation formula of the flow ratio and the pressure ratio is as follows:

[0043]

[0044]

[0045] Beneficial effects

[0046] The present application has the beneficial effect that the construction method of the mixed chamber airflow mixing characteristic map can greatly reduce the nonlinearity of the conventional format characteristic map (such as the attached Figure 3 and the attached Figure 5 , so that a high-precision characteristic map representing the key performance of the mixed chamber can be constructed based on a low-order function (a linear function and a quadratic function) with a small amount of sample data. The characteristic map can be used to directly calculate the outlet airflow parameters of the mixed chamber, thereby solving the problem of low model precision caused by the modeling assumptions of the traditional mixed chamber theoretical model. In the embodiments of the present application, the average error of the mixed chamber mixing characteristic map constructed by the method of the present application is less than 0.8%, which can meet the high-precision modeling requirements of the mixed chamber component. The specific advantages are as follows:

[0047] 1. Significantly reduce the nonlinearity of the characteristic map. By constructing the composite flow ratio and the composite pressure ratio, the nonlinearity of the curve in the characteristic map is greatly reduced (such as the attachedFigure 3 With appendix Figure 5 (Comparison). This improvement enables low-order functions (linear and quadratic functions) to fit characteristic curves with high accuracy, thereby reducing the reliance on high-order complex models.

[0048] 2. High-precision modeling with low data requirements. Traditional theoretical models suffer from insufficient accuracy due to simplification assumptions (such as equal static pressure and parallel mixing). This invention, based on experimental or CFD data and combined with the mixing mechanism of the mixing chamber, utilizes a combination of linear and quadratic fitting methods to construct high-precision characteristic maps with only a small amount of sample data. In the examples, the average error is less than 0.8% (Table 1), meeting the high-precision modeling requirements for engineering applications.

[0049] 3. Enhanced Explicit Expression and Generalization Ability. Traditional zero-dimensional models cannot explicitly express the relationship between the performance parameters of the mixing chamber and its geometric and aerodynamic parameters. This invention, however, adjusts the proportional and exponential coefficients through an optimized algorithm to ultimately form an explicit expression. Furthermore, benchmark data extrapolation and step-by-step fitting strategies enhance the model's adaptability to uncovered operating conditions, thereby improving its generalization ability.

[0050] 4. Adaptable to complex configurations and dynamically adjustable mechanisms. Traditional models struggle to reflect the impact of mixing chamber profile design on performance. However, this invention, by repeatedly constructing characteristic maps for different adjustable mechanism positions, can characterize the performance differences of mixing chambers with different configurations, making it suitable for complex mixing scenarios (such as variable cycle engines).

[0051] 5. Improve parameter adaptability by optimizing algorithms. By using optimization algorithms such as gradient descent and genetic algorithms, the proportional coefficient and exponential coefficient in the composite flow ratio and pressure ratio are automatically adjusted to ensure the optimality of model parameters and further reduce errors (e.g., the pressure ratio error is optimized to 0.45% in the example).

[0052] 6. Engineering Applicability and Extensibility. The constructed characteristic diagram can be directly used to calculate the outlet airflow parameters (such as flow rate and total pressure) of the mixing chamber, providing an efficient tool for mixing chamber design, performance simulation, and optimization. Furthermore, this method supports multi-dimensional analysis of geometric parameters (such as the opening of the adjustable mechanism) and aerodynamic parameters (total pressure, total temperature, etc.), demonstrating good extensibility. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of a method for constructing a mixing chamber airflow mixing characteristic diagram, which is optional according to an embodiment of the present invention.

[0054] Figure 2 This is a schematic diagram of two incoming streams mixing.

[0055] Figure 3 They are different Below, the flow ratio along with characteristic map of the variation.

[0056] Figure 4 are different under the pressure ratio with characteristic map of the variation.

[0057] Figure 5 are different under the composite flow ratio m c with characteristic map of the variation.

[0058] Figure 6 are different under the composite pressure ratio p c with characteristic map of the variation.

[0059] Figure 7 are different under the π m with variation law.

[0060] Figure 8 are different under the π p with variation law.

[0061] Figure 9 are linear fitting coefficients k m , b m , k p , b p variation curves of .

[0062] Figure 10 are different c,base under the reference composite flow ratio m characteristic map of the variation.

[0063] Figure 11 are different c,base under the reference composite pressure ratio p characteristic map of the variation. DETAILED DESCRIPTION

[0064] The embodiments described below by reference to the drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0065] In order to solve the problem of low model precision caused by many modeling assumptions of the traditional mixing chamber theory model, the application provides a method for constructing a mixing chamber airflow mixing characteristic diagram, the mixing chamber introduces two airflows from an inlet, and determines a mixing position through an adjustable mechanism installed in the mixing chamber, and the mixed airflow flows out from an outlet of the mixing chamber; the specific construction steps are as follows:

[0066] Step 1: In the case that the position of the adjustable mechanism of the mixing chamber is fixed, the test data or CFD simulation data of the mixing chamber are arranged into a mixing chamber mixing characteristic diagram of a conventional format in which the flow ratio and the outlet pressure ratio change with the outlet static pressure / first airflow total pressure ratio under different airflow total pressure ratios of the two airflows;

[0067] Step 2: composite flow ratios and composite pressure ratios are constructed, and the flow ratio and the outlet pressure ratio in the conventional format of the mixing chamber mixing characteristic diagram are replaced by the composite flow ratios and the composite pressure ratios, to obtain a reconstructed format of the mixing chamber mixing characteristic diagram;

[0068] Step 3: based on the reconstructed format of the mixing chamber mixing characteristic diagram, reference data are selected, and the variation law curves of the composite flow ratio and the composite pressure ratio respectively with the reference data with the inlet airflow total pressure ratio of the two airflows under different outlet static pressure / first airflow total pressure ratios are calculated;

[0069] Step 4: the variation law curves are fitted by a first-order function;

[0070] Step 5: the linear fitting coefficients in the first-order function are fitted by a second-order function according to the variation curve of the linear fitting coefficients with the outlet static pressure / first airflow total pressure;

[0071] Step 6: based on the reference data, the linear fitting coefficients and the second-order fitting coefficients, the fitting values of the composite flow ratio and the composite pressure ratio are calculated;

[0072] Step 7: the fitting values of the flow ratio and the pressure ratio are calculated according to the fitting values of the composite flow ratio and the composite pressure ratio;

[0073] Step 8: the proportion coefficient and the exponential coefficient in the composite flow ratio and the composite pressure ratio are optimized, so that the average error between the original values and the fitting values of the flow ratio and the pressure ratio is minimized;

[0074] Step 9: for different adjustable mechanism positions of the mixing chamber, the above steps are repeated to establish the mixing chamber mixing characteristic diagram under different adjustable mechanism positions.

[0075] The application realizes high-precision, low-data-demand explicit modeling by composite parameter construction, step-by-step fitting optimization and reference data expansion, solves the problems of too many modeling assumptions, insufficient precision and weak generalization ability of the traditional model, and provides a reliable modeling tool for complex mixing scenes in the fields of aviation, aerospace and energy.

[0076] The above technical solutions are further described below in combination with examples and drawings.

[0077] In one embodiment, referring to Figure 2 two incoming flows are mixed, in the construction method of a mixing chamber flow mixing characteristic map in this embodiment, the flow rate, total pressure, static pressure and total temperature of the flow are respectively represented as p * , p and T * , and the subscripts 1, 2 and out respectively represent the first incoming flow, the second incoming flow and the outlet, and the position of the adjustable mechanism is denoted as α. This embodiment includes the following steps:

[0078] Step one, under the condition that the position α of the adjustable mechanism in the mixing chamber is fixed, the test data or CFD simulation data of the mixing chamber are arranged in the conventional format of different flow ratios and pressure ratios varying with . Taking the data used in this embodiment as an example, the conventional format of the mixing characteristic map of the mixing chamber when α = 0° is shown in Figure 3 and Figure 4 .

[0079] Step two, the composite flow ratio m c and the composite pressure ratio p c are constructed according to the following formula, and replace and in the conventional format of the mixing chamber mixing characteristic map, so that the nonlinearity of the characteristic curves in the characteristic map is greatly reduced, as shown in Figure 5 and Figure 6 .

[0080]

[0081]

[0082] In the formula, a1, a2, a3, b1, b2 are proportional coefficients, and k1, k2, n1, n2 are exponential coefficients. The above coefficients usually belong to the interval [0.5, 5], and their initial values can be randomly selected within the interval, and the above coefficients will be optimized and adjusted in step eight.

[0083] In one embodiment, the initial values of a1, a2, a3, k1, k2 are set to 4.0, 4.0, 1.0, 1.0, 1.0 respectively; the initial values of b1, b2, n1, n2 are set to 1.0, 1.0, 2.0, 1.2 respectively. The reconstruction format of the mixing characteristic map of the mixing chamber with m c and p c varying with is shown in Figure 5 andFigure 6 It can be seen that the nonlinearity of the reconstructed characteristic map is lower than that of the original characteristic map, so it is easy to use a low-order function to approximate the characteristic map. Figure 3 It can be seen that the nonlinearity of the reconstructed characteristic map is lower than that of the original characteristic map, so it is easy to use a low-order function to approximate the characteristic map. Figure 4 It can be seen that the nonlinearity of the reconstructed characteristic map is lower than that of the original characteristic map, so it is easy to use a low-order function to approximate the characteristic map.

[0084] Step three, based on the reconstructed format of the mixing chamber mixing characteristic map in step two, select the specified minimum The characteristic data under the reference data is calculated using the following formula: Next, the same The ratio of m c and p c to the reference data is π m and π p :

[0085]

[0086]

[0087] In the formula, m c,base and p c,base represent the reference m c and the reference p c under the minimum If the range of the reference data cannot cover all the data, use the quadratic interpolation method to extend the value.

[0088] In one embodiment, as shown in Figure 5 and Figure 6 , the characteristic line under is selected as the reference and is numerically extended. Different , π m and π p change with as shown in Figure 7 and Figure 8 . It can be seen that under different , π m and π p have a high degree of linear correlation with .

[0089] Step four, linearly fit the change curve of π m and π p with under different , and the fitting relationship is as follows:

[0090]

[0091]

[0092] In the formula, km b m k p b p These are the linear fitting coefficients. For the appendix of this embodiment... Figure 7 and attached Figure 8 k m b m k p b p Follow The change curve is as follows Figure 9 As shown.

[0093] Step 5, for k m b m k p b p Follow The change curve is subjected to a second-order fitting, and the fitting relationship is as follows:

[0094]

[0095]

[0096]

[0097]

[0098] In the formula, c1~c 12 These are the quadratic fitting coefficients.

[0099] In one embodiment, such as Figure 9 As shown, c1~c 12 The values ​​are: -5.028, 5.410, -1.967, 3.097, -3.322, 2.209, -0.413, -2.099, 1.242, -0.094, 2.000, and -0.114.

[0100] Step 6: Based on the baseline characteristics selected in Step 3, calculate m using the fitting relationship established in Steps 4 and 5. c and p c The fitted value m c ′ and p c ′, as shown in the following formula:

[0101]

[0102]

[0103] Step 7, based on m c ′ and p c 'calculate and The fitted value is as follows:

[0104]

[0105]

[0106] Step 8: Use an optimization algorithm to optimize the proportional coefficient and exponential coefficient in Step 2, so that... and The average error between the original value and the fitted value is the smallest.

[0107] In one embodiment, the optimized values ​​of a1, a2, a3, k1, and k2 are 4.5, 3.8, 1.0, 1.0, and 1.0, respectively. The average error between the original and fitted values ​​is 0.74%; the optimized values ​​of b1, b2, n1, and n2 are 1.1, 1.0, 2.0, and 1.3, respectively. The average error between the original value and the fitted value is 0.45%.

[0108] Step nine: For different adjustable mechanism positions α in the mixing chamber, repeat the operations of steps one to eight to establish the mixing characteristics diagram of the mixing chamber under different adjustable mechanism positions.

[0109] In one embodiment, at different adjustable mechanism positions α in the mixing chamber, all are selected Based on the characteristic line, m c,base and p c,base along with The diagram showing the changing mixing characteristics of the mixing chamber is attached. Figure 10 and attached Figure 11 As shown. The calculation can be performed using the baseline data from this characteristic graph and the formula from step seven. and The fitted value. and The average error between the original and fitted values ​​is shown in the table below. It can be seen that the average error of the mixing characteristic map of the mixing chamber constructed using the method of this invention is less than 0.8%, which can meet the high-precision modeling requirements of the mixing chamber components.

[0110] Table 1. Average fitting error (%) at different adjustable mechanism positions

[0111]

[0112] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for constructing a mixing characteristic diagram of an airflow in a mixing chamber, wherein two airflows are introduced into the mixing chamber from the inlet, and the mixing position is determined by an adjustable mechanism installed inside the mixing chamber, and the mixed airflow flows out from the outlet of the mixing chamber; characterized in that... The specific steps are as follows: With the position of the adjustable mechanism in the mixing chamber fixed, the test data or CFD simulation data of the mixing chamber are organized into a conventional format of the mixing characteristics diagram of the mixing chamber under different total pressure ratios of the two airflows, showing the changes in flow ratio and outlet pressure ratio with outlet static pressure / first total pressure. A composite flow rate ratio and composite pressure ratio are constructed and used to replace the flow rate ratio and outlet pressure ratio in the conventional format of the mixing chamber blending characteristic diagram, resulting in a reconstructed format of the mixing chamber blending characteristic diagram; the composite flow rate ratio... and composite pressure ratio The expressions are as follows: In the formula, , , , , All are proportionality coefficients. , , , All are exponential coefficients; Indicates gas flow rate, Indicates the total temperature. Indicates total pressure. The subscripts 1, 2, and out indicate the first inflow, the second inflow, and the outlet, respectively. Based on the reconstruction format of the mixing chamber mixing characteristic diagram, reference data is selected, and the curves showing the variation of the ratios of the composite flow rate ratio and composite pressure ratio to the reference data under different outlet static pressures / first inflow total pressures are calculated as follows: Perform a linear function fitting on the curve of the change pattern; A quadratic function is used to fit the curve of the linear fitting coefficient in the linear function as a function of the outlet static pressure / first incoming total pressure. Based on the aforementioned baseline data, linear fitting coefficients, and quadratic fitting coefficients, the fitted values ​​of the composite flow ratio and composite pressure ratio are calculated. Based on the fitted values ​​of the composite flow ratio and composite pressure ratio, calculate the fitted values ​​of the flow ratio and pressure ratio; Optimize the proportional coefficient and exponential coefficient in the composite flow ratio and composite pressure ratio to minimize the average error between the original values ​​and the fitted values ​​of the flow ratio and pressure ratio; Repeat the above steps for different adjustable mechanism positions in the mixing chamber to establish mixing characteristic diagrams for different adjustable mechanism positions.

2. The method for constructing a mixing chamber airflow mixing characteristic map according to claim 1, characterized in that: The expression for the flow ratio in the conventional format of the mixing chamber blending characteristic diagram is: The expression for the outlet pressure ratio is: .

3. The method for constructing a mixing chamber airflow mixing characteristic map according to claim 1, characterized in that: The initial values ​​of the proportional coefficient and the exponential coefficient are randomly selected within the interval [0.5, 5] and adjusted to the optimal values ​​through an optimization algorithm.

4. The method for constructing a mixing chamber airflow mixing characteristic map according to claim 1, characterized in that: The reference data are the composite flow rate ratio and composite pressure ratio corresponding to the minimum total pressure ratio of the two incoming airflows, i.e., the reference composite flow rate ratio and the reference composite pressure ratio; The ratio of the composite flow rate ratio to the baseline composite flow rate ratio is, The ratio of the composite pressure ratio to the reference composite pressure ratio is, 。 5. The method for constructing a mixing chamber airflow mixing characteristic map according to claim 4, characterized in that: The reference data is extended numerically using a quadratic extrapolation method.

6. The method for constructing a mixing chamber airflow mixing characteristic map according to claim 4, characterized in that: The expression for fitting the curve of the change pattern to a linear function is as follows: In the formula, , , , These are the linear fitting coefficients.

7. The method for constructing a mixing chamber airflow mixing characteristic map according to claim 6, characterized in that: The expression for fitting a quadratic function to the linear fitting coefficients is as follows: In the formula, ~ These are the quadratic fitting coefficients.

8. The method for constructing a mixing chamber airflow mixing characteristic map according to claim 7, characterized in that: The formulas for calculating the fitted values ​​of the composite flow ratio and composite pressure ratio are as follows: 。 9. The method for constructing a mixing chamber airflow mixing characteristic map according to claim 8, characterized in that: The formulas for calculating the fitted values ​​of the flow ratio and pressure ratio are as follows: 。

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