Method for selecting ejector combination to control turbine casing temperature

Abstract

The present invention discloses a method for selecting an ejector combination for regulating the temperature of a turbine casing. This scheme performs iterative calculations based on the metal temperature requirement of the turbine casing, and ultimately selects the ejector combination with the smallest ejection flow rate to achieve mixing and diffusing of the ejected gas, thereby meeting the metal temperature requirement of the turbine casing with the smallest ejection flow rate. Compared with the existing technology, this scheme reduces the air intake volume of the air system to the greatest extent, improves the performance of the aircraft engine, and reduces the fuel consumption rate of the aircraft engine. In addition, the metal temperature of the turbine casing can be actively regulated by actively selecting the ejector combination to ensure that the aircraft engine is in the best working state. This scheme has strong practicality and is suitable for wide promotion and application.

Description

Technical Field

[0001] The present invention relates to the technical field of aero-engines, and in particular to a method for selecting an ejector combination for regulating the temperature of a turbine casing. Background Art

[0002] The air system is the secondary flow system of an aircraft engine, primarily used to ensure efficient and stable engine operation under various operating conditions. Increasing the amount of bleed air in the air system can lead to reduced engine thrust, increased exhaust temperature, increased fuel consumption, a higher oil-to-air ratio, a decrease in the total pressure at the high-pressure compressor outlet, and an increase in the high-pressure compressor kick margin. This is because the bleed air in the air system primarily comes from the compressed gas in the compressor. The compressed gas drawn from the compressor should enter the combustion chamber to mix with the fuel and burn, participating in the engine's thermodynamic cycle and performing external work as the mainstream. However, it is drawn out to meet the functional requirements of the air system, thus losing the opportunity to perform work and causing a decrease in engine performance. Therefore, while meeting reliability and safety requirements, aircraft engines will minimize the amount of bleed air in the air system to reduce the impact on engine performance and lower the engine's fuel consumption.

[0003] An ejector is a device that uses a high-speed fluid to eject another, lower-speed fluid. Its operating principle is that the high-speed fluid expands in a converging nozzle, transferring energy to the ejected fluid, causing the two to mix within a mixing chamber, thereby increasing the pressure and velocity of the ejected fluid. Therefore, by passing a small amount of high-pressure gas through a Rafale nozzle and then ejecting a large flow of low-pressure gas, the ejector can be applied to the air system of aircraft engines. For example, Chinese invention patent application CN115788601A discloses an ejector air bleed device for controlling the tip clearance of aircraft engine turbines. Specifically, the ejector air bleed device comprises two ejectors arranged circumferentially around the engine, each equipped with two bleed air lines and an exhaust line. A partition is installed between the turbine casing and the combustion chamber casing to form an annular chamber. The ejectors mix and expand the two gases drawn into the two bleed air lines, and then discharge the exit fluid. The present invention ensures uniform circumferential temperature of the airflow in the annular chamber that provides the air source for cooling the turbine casing by combining two ejectors. Simultaneously, by optimizing the structural dimensions of the ejectors, the ejection coefficient of the ejectors reaches 1.7, and the expansion ratio of the ejected fluid reaches 1.4, thus meeting the cooling requirements for tip clearance control of high-pressure turbine casings in small and medium-sized aircraft engines with high compression ratios.

[0004] However, although the above-mentioned bleed air device can control the turbine casing tip clearance by regulating the temperature of the turbine casing, it cannot ensure that the bleed air flow of the bleed air device is minimum. Therefore, the bleed air volume of the air system is still relatively large, the performance of the aircraft engine is poor, and the fuel consumption rate is high. Summary of the Invention

[0005] The present invention provides an ejector combination selection method for regulating turbine casing temperature, so as to solve the technical problems that the air system of existing aircraft engines has a relatively large amount of bleed air, the performance of the aircraft engines is poor, and the fuel consumption rate is high.

[0006] According to one aspect of the present invention, a method for selecting an ejector combination for regulating the temperature of a turbine casing is provided, which is characterized in that it includes the following steps: S1, obtaining the gas side temperature and the gas side heat transfer coefficient of the turbine casing according to the metal temperature requirement of the turbine casing and the main state parameters in the engine envelope; S2, obtaining the correlation formula of the cooling air temperature and the cooling air side heat transfer coefficient of the turbine casing according to the gas side temperature and the gas side heat transfer coefficient of the turbine casing and based on the thermodynamic energy balance formula; S3, within the aircraft engine parameter range, obtaining a solution set of the cooling air temperature and the cooling air side heat transfer coefficient of multiple groups of turbine casings through the correlation formula of the cooling air temperature and the cooling air side heat transfer coefficient, obtaining a solution set of the cooling air temperature and the cooling air mass flow according to the maximum and minimum values ​​in the solution sets of the cooling air temperature and the cooling air side heat transfer coefficient of the multiple groups of turbine casings and based on the correlation formula of the cooling air side heat transfer coefficient and the cooling air mass flow, and then The solution set is iteratively calculated with the engine's overall distribution index and heat transfer coefficient requirements to discard the solution set that does not meet the requirements of the cooling air temperature and cooling air mass flow rate, and obtain the solution set that meets the requirements of the cooling air temperature and cooling air mass flow rate; S4, based on the calculation formula of the ejector parameters, the correlation formula between the ejector combination and multiple ejectors is obtained to carry out the calculation of the ejector combination parameters to obtain the solution set of the ejector combination parameters and multiple ejector parameters, and based on the correlation formula between the cooling air temperature and the ejector combination parameters, the solution set of the cooling air temperature and the ejector combination parameters is obtained, and then based on the correlation formula between the cooling air mass flow rate and the ejector combination parameters, the solution set of the cooling air mass flow rate and the ejector combination parameters is obtained; S5, the ejector combination with the smallest ejection flow rate is selected from the solution set of the cooling air temperature and the cooling air mass flow rate, the solution set of the cooling air temperature and the ejector combination parameters, and the solution set of the cooling air mass flow rate and the ejector combination parameters, and the selection of the ejector combination is realized through the electronic control system.

[0007] Furthermore, in step S2, the correlation formula between the cooling air temperature of the turbine casing and the cooling air side heat transfer coefficient is:

[0008]

[0009] Where A is the heat exchange area, Hwg is the heat transfer coefficient of the gas side of the turbine casing, T g is the gas side temperature of the turbine casing, T w1 is the metal temperature requirement of the turbine casing, λ is the metal thermal conductivity of the turbine casing, δ is the thickness of the turbine casing, T w2 is the cold air side temperature of the turbine case, H wc is the heat transfer coefficient of the cooling air side of the turbine casing, T c The air conditioning temperature.

[0010] Furthermore, in step S3, the correlation formula between the cold air side heat transfer coefficient and the cold air mass flow rate is:

[0011]

[0012] R e ∞N u ;

[0013]

[0014] Among them, R e is the cooling air Reynolds number, G is the cooling air flow rate, L is the heat transfer characteristic size of the cooling air side, μ is the viscosity coefficient, A2 is the cooling air side flow area, N u is the cold air Nusselt number, and λ2 is the cold air thermal conductivity.

[0015] Furthermore, in step S4, the calculation formula of the ejector parameters is:

[0016]

[0017] Where α is the ejector area ratio, A p is the ejector nozzle outlet area, A S is the ejector nozzle outlet ejection area, k is the ejector ejection coefficient, G s is the ejected flow rate, G p is the ejector flow rate, c is the ejector specific heat ratio, C ps is the specific heat of the ejected gas at constant pressure, C pp is the specific heat of the constant pressure ejector gas, θ is the total temperature ratio of the ejector, T os is the induced temperature, T op is the ejected gas temperature.

[0018] Furthermore, the ejector combination includes a plurality of ejectors with different ejection coefficients, and the ejectors are connected through a parallel circuit.

[0019] Furthermore, within the ejector combination, the number of ejectors with different ejection coefficients is n1, n2, ... n n .

[0020] Furthermore, in step S4, the correlation formula between the ejector combination and the multiple ejectors is:

[0021] In the ejector combination, the number of ejectors with different ejection coefficients is n1, n2...n n ;

[0022]

[0023] Among them, α 总 is the ejector combined area ratio, k 总 is the ejector combination ejection coefficient, c 总 is the ejector combination specific heat ratio, θ 总 is the total temperature ratio of the ejector combination.

[0024] Furthermore, in step S4, the correlation formula between the cold air temperature and the ejector combination parameter is:

[0025]

[0026] Furthermore, in step S4, the correlation formula between the mass flow rate of cold air and the ejector combination parameter is:

[0027] G=(n1C ps1 +n2C ps2 +……n n C psn )+(n1C pp1 +n2C pp2 +……n n C ppn ).

[0028] Furthermore, in step S1, the main state parameters within the engine envelope include engine inlet flow, compressor aerodynamic pressure at each stage, compressor temperature at each stage, combustion chamber outlet temperature, gas turbine temperature at each stage, gas turbine pressure at each stage, power turbine temperature at each stage, power turbine pressure at each stage and engine speed.

[0029] The present invention has the following beneficial effects:

[0030] The present invention provides an ejector combination selection method for controlling the temperature of a turbine casing. First, the gas side temperature and the gas side heat transfer coefficient of the turbine casing are obtained based on the metal temperature requirement of the turbine casing and the main state parameters in the engine envelope. Then, based on the gas side temperature and the gas side heat transfer coefficient of the turbine casing and the thermodynamic energy balance formula, a correlation formula between the cooling air temperature and the cooling air side heat transfer coefficient of the turbine casing is obtained. Then, within the aircraft engine parameter range, the correlation formula between the cooling air temperature and the cooling air side heat transfer coefficient of the turbine casing is used to obtain a solution set of multiple groups of cooling air temperatures and cooling air side heat transfer coefficients of the turbine casing. According to the maximum and minimum values ​​in the solution sets of the cooling air temperature and cooling air side heat transfer coefficient of multiple groups of turbine casings, and based on the correlation formula of the cooling air side heat transfer coefficient and the cooling air mass flow rate, the solution set of cooling air temperature and cooling air mass flow rate is obtained, and the solution set of cooling air temperature and cooling air mass flow rate is iteratively calculated with the overall distribution index and heat transfer coefficient requirement of the engine to discard the solution set of cooling air temperature and cooling air mass flow rate that does not meet the requirements, and obtain the solution set of cooling air temperature and cooling air mass flow rate that meets the requirements; then, based on the calculation formula of the ejector parameters, the correlation formula between the ejector combination and multiple ejectors is obtained to carry out ejection. The ejector combination parameters are calculated to obtain the solution set of the ejector combination parameters and multiple ejector parameters, and based on the correlation formula between the cold air temperature and the ejector combination parameters, the solution set of the cold air temperature and the ejector combination parameters is obtained, and then based on the correlation formula between the cold air mass flow rate and the ejector combination parameters, the solution set of the cold air mass flow rate and the ejector combination parameters is obtained; finally, the ejector combination with the minimum ejection flow rate is selected from the solution set of the cold air temperature and the cold air mass flow rate, the solution set of the cold air temperature and the ejector combination parameters, and the solution set of the cold air mass flow rate and the ejector combination parameters, and the ejector combination parameter is realized through an electronic control system. Selection of combination: This scheme performs iterative calculations based on the metal temperature requirement of the turbine casing, and ultimately selects the ejector combination with the smallest ejection flow rate to achieve mixing and diffusing of the ejected gas, thereby meeting the metal temperature requirement of the turbine casing with the smallest ejection flow rate. Compared with the existing technology, this scheme minimizes the amount of air bleed in the air system, improves the performance of the aircraft engine, and reduces the fuel consumption rate of the aircraft engine. In addition, the metal temperature of the turbine casing can be actively regulated by actively selecting the ejector combination to ensure that the aircraft engine is in the best working condition. It is highly practical and suitable for wide promotion and application.

[0031] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0033] Figure 1 It is a flowchart of the steps of the method for selecting an ejector combination for regulating the temperature of a turbine casing according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0034] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0035] like Figure 1 As shown, the method for selecting an ejector combination for regulating the temperature of a turbine casing of the present embodiment is characterized in that it includes the following steps: S1, obtaining the gas side temperature and the gas side heat transfer coefficient of the turbine casing according to the metal temperature requirement of the turbine casing and the main state parameters in the engine envelope; S2, obtaining the correlation formula of the cooling air temperature and the cooling air side heat transfer coefficient of the turbine casing according to the gas side temperature and the gas side heat transfer coefficient of the turbine casing and based on the thermodynamic energy balance formula; S3, within the range of aircraft engine parameters, obtaining a solution set of the cooling air temperature and the cooling air side heat transfer coefficient of multiple groups of turbine casings through the correlation formula of the cooling air temperature and the cooling air side heat transfer coefficient of the turbine casing, obtaining a solution set of the cooling air temperature and the cooling air mass flow according to the maximum and minimum values ​​in the solution sets of the cooling air temperature and the cooling air side heat transfer coefficient of multiple groups of turbine casings and based on the correlation formula of the cooling air side heat transfer coefficient and the cooling air mass flow, and then comparing the solution set of the cooling air temperature and the cooling air mass flow with the cooling air temperature. The overall distribution index and heat transfer coefficient requirements of the engine are iteratively calculated to discard the solution set that does not meet the requirements of the cooling air temperature and cooling air mass flow rate, and obtain the solution set of the cooling air temperature and cooling air mass flow rate that meet the requirements; S4, based on the calculation formula of the ejector parameters, the correlation formula between the ejector combination and multiple ejectors is obtained to carry out the calculation of the ejector combination parameters to obtain the solution set of the ejector combination parameters and multiple ejector parameters, and based on the correlation formula between the cooling air temperature and the ejector combination parameters, the solution set of the cooling air temperature and the ejector combination parameters is obtained, and then based on the correlation formula between the cooling air mass flow rate and the ejector combination parameters, the solution set of the cooling air mass flow rate and the ejector combination parameters is obtained; S5, the ejector combination with the smallest ejection flow rate is selected from the solution set of the cooling air temperature and the cooling air mass flow rate, the solution set of the cooling air temperature and the ejector combination parameters, and the solution set of the cooling air mass flow rate and the ejector combination parameters, and the selection of the ejector combination is realized through the electronic control system. This solution performs iterative calculations based on the metal temperature requirement of the turbine casing, and ultimately selects the ejector combination with the smallest ejection flow rate to achieve mixing and diffusing of the ejected gas, thereby meeting the metal temperature requirement of the turbine casing with the smallest ejection flow rate. Compared with existing technologies, this solution minimizes the amount of air bleed from the air system, improves the performance of the aircraft engine, and reduces the fuel consumption rate of the aircraft engine. In addition, the metal temperature of the turbine casing can be actively regulated by actively selecting the ejector combination to ensure that the aircraft engine is in the best working condition. This solution is highly practical and suitable for wide promotion and application.

[0036] It should be understood that in aircraft engines without ejectors, the air system draws air from the compressor and delivers it to the turbine case via external piping for cooling and temperature control. In this embodiment, the air system also draws air from the compressor and enters the ejector via a portion of the air system's external piping. The ejector ejects low-temperature, low-pressure air from the nacelle to cool the turbine case, and actively controls the turbine case metal temperature by iterating with the turbine case metal temperature.

[0037] It should be understood that the amount of air bleed from the air system will directly affect the performance and fuel consumption of the aircraft engine. High-performance aircraft engines require the bleed air volume to be minimized. This embodiment can take into account both small bleed air volume and high-efficiency cooling, and can also control the metal temperature of the turbine casing by selecting an ejector combination.

[0038] It should be understood that the overall engine distribution index and heat transfer coefficient requirements are known parameters in the iterative calculation process.

[0039] It should be understood that by actively regulating the metal temperature of the turbine casing, the turbine tip clearance can be controlled, thereby adjusting the performance of the aircraft engine.

[0040] In this embodiment, in step S2, the correlation formula between the cooling air temperature of the turbine casing and the cooling air side heat transfer coefficient is:

[0041]

[0042] Where A is the heat exchange area, H wg is the heat transfer coefficient of the gas side of the turbine casing, T g is the gas side temperature of the turbine casing, T w1 is the metal temperature requirement of the turbine casing, λ is the metal thermal conductivity of the turbine casing, δ is the thickness of the turbine casing, T w2 is the cold air side temperature of the turbine case, H wc is the heat transfer coefficient of the cooling air side of the turbine casing, T c The air conditioning temperature.

[0043] It should be understood that in the above parameters, T c and T c is an unknown quantity, and the others are known quantities. Therefore, the cooling air temperature and the cooling air side heat transfer coefficient can be obtained through the above-mentioned correlation formula and known quantities, providing data support for the subsequent iterative calculation of the cooling air mass flow rate.

[0044] In this embodiment, in step S3, the correlation formula between the cold air side heat transfer coefficient and the cold air mass flow rate is:

[0045]

[0046] R e ∞N u ;

[0047]

[0048] Among them, R e is the cooling air Reynolds number, G is the cooling air flow rate, L is the heat transfer characteristic size of the cooling air side, μ is the viscosity coefficient, A2 is the cooling air side flow area, N u is the cold air Nusselt number, and λ2 is the cold air thermal conductivity.

[0049] Specifically, since the heat transfer coefficient on the cold air side and the cold air temperature are correlated with each other, the solution set of the cold air temperature and the cold air mass flow rate can be obtained through the above correlation formula.

[0050] It should be understood that, in the above correlation formula, G is an unknown quantity, and the other parameters are known quantities.

[0051] In this embodiment, in step S4, the calculation formula of the ejector parameters is:

[0052]

[0053] Where α is the ejector area ratio, A p is the ejector nozzle outlet area, A S is the ejector nozzle outlet ejection area, k is the ejector ejection coefficient, G s is the ejected flow rate, G p is the ejector flow rate, c is the ejector specific heat ratio, C ps is the specific heat of the ejected gas at constant pressure, C pp is the specific heat of the constant pressure ejector gas, θ is the total temperature ratio of the ejector, T os is the induced temperature, T op is the ejected gas temperature.

[0054] In this embodiment, the ejector assembly includes multiple ejectors with different ejection coefficients, connected in parallel. Specifically, multiple ejectors with different ejection coefficients are connected in parallel to form an ejector assembly. An electronic control system can select different ejector combinations to actively control the metal temperature of the turbine casing.

[0055] In this embodiment, in the ejector combination, the number of ejectors with different ejection coefficients is n1, n2...n n .

[0056] In this embodiment, in step S4, the correlation formula between the ejector combination and the multiple ejectors is:

[0057]

[0058] Among them, α 总 is the ejector combined area ratio, k 总 is the ejector combination ejection coefficient, c 总 is the ejector combination specific heat ratio, θ 总 is the total temperature ratio of the ejector combination.

[0059] Specifically, it can be seen from the above correlation formula that by selecting the number of ejectors with different ejection coefficients through the electronic control system, different ejector combinations can be formed, thereby achieving active control of the metal temperature of the turbine casing.

[0060] In this embodiment, in step S4, the correlation formula between the cold air temperature and the ejector combination parameter is:

[0061]

[0062] In this embodiment, in step S4, the correlation formula between the mass flow rate of cold air and the ejector combination parameter is:

[0063] G=(n1C ps1 +n2C ps2 +……n n C psn )+(n1C pp1 +n2C pp2 +……n n C ppn ).

[0064] In this embodiment, in step S1, the main state parameters within the engine envelope include engine inlet flow, compressor aerodynamic pressure at each stage, compressor temperature at each stage, combustion chamber outlet temperature, gas turbine temperature at each stage, gas turbine pressure at each stage, power turbine temperature at each stage, power turbine pressure at each stage and engine speed.

[0065] The method for selecting an ejector combination for regulating the temperature of the turbine casing of this embodiment has been studied through numerical simulation. It can reduce the air intake volume of the air system by 70% and improve the cooling effect by 40%. The ejector combination is selected by the electronic control system to achieve active regulation of the metal temperature of the turbine casing, and the temperature control range reaches 200K.

[0066] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for selecting an ejector combination for controlling the temperature of a turbine casing, characterized in that: The following steps are involved: S1, based on the metal temperature requirement of the turbine casing and the main state parameters in the engine envelope, obtain the gas side temperature and gas side heat transfer coefficient of the turbine casing; S2, according to the gas side temperature and gas side heat transfer coefficient of the turbine casing and based on the thermodynamic energy balance formula, obtain a correlation formula between the cooling air temperature and the cooling air side heat transfer coefficient of the turbine casing; S3, within the aircraft engine parameter range, obtaining a solution set of multiple sets of turbine case cooling air temperatures and cooling air side heat transfer coefficients using a correlation formula between the turbine case cooling air temperatures and cooling air side heat transfer coefficients; obtaining a solution set of cooling air temperatures and cooling air mass flow rates based on the maximum and minimum values ​​in the solution sets of the multiple sets of turbine case cooling air temperatures and cooling air side heat transfer coefficients, and based on a correlation formula between the cooling air side heat transfer coefficient and cooling air mass flow rates; then iteratively calculating the solution set of cooling air temperatures and cooling air mass flow rates with the overall engine distribution index and heat transfer coefficient requirements, discarding solution sets of cooling air temperatures and cooling air mass flow rates that do not meet the requirements, and obtaining a solution set of cooling air temperatures and cooling air mass flow rates that meet the requirements; S4, based on the calculation formula of the ejector parameters, obtaining a correlation formula between the ejector combination and the multiple ejectors, so as to carry out the calculation of the ejector combination parameters, and obtain a solution set of the ejector combination parameters and the multiple ejector parameters, and based on the correlation formula between the cold air temperature and the ejector combination parameters, obtain a solution set of the cold air temperature and the ejector combination parameters, and then based on the correlation formula between the cold air mass flow rate and the ejector combination parameters, obtain a solution set of the cold air mass flow rate and the ejector combination parameters; S5, select the ejector combination with the smallest ejection flow rate from the solution set of cold air temperature and cold air mass flow rate, the solution set of cold air temperature and ejector combination parameters, and the solution set of cold air mass flow rate and ejector combination parameters, and realize the selection of the ejector combination through the electronic control system.

2. The method for selecting an ejector combination for controlling the temperature of a turbine casing according to claim 1, characterized in that: In step S2, the correlation formula between the cooling air temperature of the turbine casing and the cooling air side heat transfer coefficient is: Where A is the heat exchange area, H wg is the heat transfer coefficient of the gas side of the turbine casing, T g is the gas side temperature of the turbine casing, T w1 is the metal temperature requirement of the turbine casing, λ is the metal thermal conductivity of the turbine casing, δ is the thickness of the turbine casing, T w2 is the cold air side temperature of the turbine case, H wc is the heat transfer coefficient of the cooling air side of the turbine casing, T c The air conditioning temperature.

3. The method for selecting an ejector combination for controlling the temperature of a turbine casing according to claim 1, characterized in that: In step S3, the correlation formula between the heat transfer coefficient on the cold air side and the cold air mass flow rate is: Among them, R e is the cooling air Reynolds number, G is the cooling air flow rate, L is the heat transfer characteristic size of the cooling air side, μ is the viscosity coefficient, A2 is the cooling air side flow area, N u is the cold air Nusselt number, and λ2 is the cold air thermal conductivity.

4. The method for selecting an ejector combination for controlling the temperature of a turbine casing according to any one of claims 1 to 3, characterized in that: In step S4, the calculation formula of the ejector parameters is: Where α is the ejector area ratio, A p is the ejector nozzle outlet area, A S is the ejector nozzle outlet ejection area, k is the ejector ejection coefficient, G s is the ejected flow rate, G p is the ejector flow rate, c is the ejector specific heat ratio, C ps is the specific heat of the ejected gas at constant pressure, C pp is the specific heat of the constant pressure ejector gas, θ is the total temperature ratio of the ejector, T os is the induced temperature, T op is the ejected gas temperature.

5. The method for selecting an ejector combination for controlling the temperature of a turbine casing according to claim 4, characterized in that: In step S4, the ejector assembly includes a plurality of ejectors with different ejection coefficients, and the ejectors are connected via a parallel circuit.

6. The method for selecting an ejector combination for controlling the temperature of a turbine casing according to claim 5, characterized in that: In the ejector combination, the number of ejectors with different ejection coefficients is n1, n2...n n .

7. The method for selecting an ejector combination for controlling the temperature of a turbine casing according to claim 6, characterized in that: In step S4, the correlation formula between the ejector combination and the multiple ejectors is: Among them, α 总 is the ejector combined area ratio, k 总 is the ejector combination ejection coefficient, c 总 is the ejector combination specific heat ratio, θ 总 is the total temperature ratio of the ejector combination.

8. The method for selecting an ejector combination for controlling the temperature of a turbine casing according to claim 7, characterized in that: In step S4, the correlation formula between the cooling air temperature and the ejector combination parameter is:

9. The method for selecting an ejector combination for controlling the temperature of a turbine casing according to claim 7, wherein: In step S4, the correlation formula between the mass flow rate of cold air and the ejector combination parameter is: G=(n1C ps1 +n2C ps2 +……n n C psn )+(n1C pp1 +n2C pp2 +……n n C ppn )。 10. The method for selecting an ejector combination for controlling the temperature of a turbine casing according to any one of claims 1 to 3, characterized in that: In step S1, the main state parameters within the engine envelope include engine inlet flow, compressor aerodynamic pressure at each stage, compressor temperature at each stage, combustor outlet temperature, gas turbine temperature at each stage, gas turbine pressure at each stage, power turbine temperature at each stage, power turbine pressure at each stage, and engine speed.

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