Overall structure design method of micro turbojet engine

Abstract

The invention relates to the technical field of aero-engine design, in particular to an overall structure design method of a micro turbojet engine. According to the technical scheme, thermodynamic parameters and target performance parameters of the turbojet engine and budget parameters of gas flow path design are obtained; a centrifugal compressor structure and a turbine structure are rapidly obtained in the overall design link of the turbojet engine according to the thermodynamic parameters and the budget parameters; and according to the target performance parameters, the design coupling of the centrifugal compressor structure and the turbine structure is verified to obtain a first coupling result of the centrifugal compressor structure and a second coupling result of the turbine structure, and when all the coupling results meet a preset target, the overall structure design result of the turbojet engine is output. According to the technical scheme, the design iteration period of overall and structural designers can be shortened, the overall and structural designers are guided to carry out scheme design, and the matching efficiency and accuracy of the overall structure of the aero-engine and the parts of the aero-engine are improved.

Description

Technical Field

[0001] This invention relates to the technical field of aero-engine design, and specifically to a method for the overall structural design of a micro turbojet engine. Background Technology

[0002] As the pinnacle of high-end equipment manufacturing, aero-engines are hailed as the crown jewel of industry due to their extremely demanding and complex design and manufacturing requirements. The overall design of aero-engines is the top-level design of R&D technology and the soul of aero-engines.

[0003] The performance parameters of an aero-engine are crucial to its overall design, determining its level of sophistication. Based on these parameters, it's essential to estimate the structural dimensions and weight of key components, making it a vital step in the overall aero-engine design process. Current design methods cannot perform overall structure-component matching during the overall design phase, resulting in insufficient design efficiency and accuracy in this stage. Summary of the Invention

[0004] In order to address the technical problem of improving the matching efficiency and accuracy between the overall structure of an aero-engine and its components in the overall design phase, this invention aims to provide a method for the overall structural design of a micro turbojet engine. The specific technical solution adopted is as follows: This invention provides a method for the overall structural design of a micro turbojet engine, the method comprising: Obtain the thermodynamic parameters, target performance parameters, and budget parameters for gas flow path design of the turbojet engine; The structural profile of the turbojet engine is calculated along the airflow direction based on thermodynamic and budget parameters to obtain the centrifugal compressor and turbine structure of the turbojet engine. The design coupling of the centrifugal compressor structure and the turbine structure is verified based on the target performance parameters to obtain the first coupling result of the centrifugal compressor structure and the second coupling result of the turbine structure. If the first or second coupling result does not meet the preset target, update the corresponding parameters, recalculate and verify the design structure of the turbojet engine; When both the first coupling result and the second coupling result meet the preset target, the overall structural design result of the turbojet engine is output.

[0005] In one optional embodiment, structural profile calculations are performed along the airflow direction of the turbojet engine based on thermodynamic and budget parameters to obtain the centrifugal compressor and turbine structures of the turbojet engine, including: Multiple first target data associated with the centrifugal compressor are extracted from thermodynamic parameters and budget parameters, and input into the first processing model to solve the component profile of the centrifugal compressor; Based on the output of the first processing model, the structure of the centrifugal compressor and the first outlet cross-sectional area of ​​the centrifugal compressor are obtained; The first outlet cross-sectional area is input into the second processing model to calculate the component contours of the combustion chamber; Based on the output of the second processing model, the combustion chamber structure and the second outlet cross-sectional area of ​​the combustion chamber are obtained; Multiple second target data related to the turbine are extracted from thermodynamic parameters and budget parameters, and the multiple second target data and the second outlet cross-sectional area are input into the third processing model to solve the component profile of the turbine. The turbine structure is obtained based on the output of the third processing model.

[0006] In one optional embodiment, multiple first target data include the centrifugal compressor's inlet Mach number, outlet Mach number, inlet flow rate, outlet flow rate, total inlet and outlet temperature, total inlet and outlet pressure, inlet and outlet air-fuel ratio, blade-to-hub ratio, inlet and outlet outer diameter ratio, and flow path profile equation coefficients; inputting multiple first target data into a first processing model to perform component profile calculation of the centrifugal compressor includes: The inlet Mach number, outlet Mach number, inlet flow rate, outlet flow rate, total inlet and outlet temperature, total inlet and outlet pressure, and inlet and outlet oil-gas ratio are processed according to the flow continuity equation to obtain the first inlet cross-sectional area and the first outlet cross-sectional area of ​​the centrifugal compressor. Based on the blade-to-hub ratio, the first inlet cross-sectional area, and the inlet-outlet outer diameter ratio, the inlet inner diameter, inlet outer diameter, inlet blade height, outlet diameter, and outlet blade height of the centrifugal compressor are obtained. The impeller flow path profile of the centrifugal compressor is obtained by integrating the flow path profile equation coefficients and the outlet blade height.

[0007] In one optional embodiment, the first outlet cross-sectional area is input into a second processing model to calculate the component contours of the combustion chamber, including: The outer diameter, inner diameter, and height of the combustion chamber are obtained based on the cross-sectional area of ​​the first outlet. The length of the combustion chamber is obtained based on its outer diameter and a preset diameter-to-length ratio.

[0008] In one optional embodiment, multiple second target data include a third incoming Mach number at the turbine inlet, a fourth incoming Mach number at the turbine outlet, and the turbine's hub ratio; inputting the multiple second target data and the second outlet cross-sectional area into a third processing model to calculate the turbine's component profiles includes: The third outlet cross-sectional area of ​​the turbine is obtained based on the third incoming Mach number, the fourth incoming Mach number, and the second outlet cross-sectional area. The inner and outer diameters of the turbine are obtained based on the cross-sectional area of ​​the third outlet and the hub ratio.

[0009] In one optional embodiment, the design coupling of the centrifugal compressor structure and the turbine structure is verified according to the target performance parameters to obtain a first coupling result for the centrifugal compressor structure and a second coupling result for the turbine structure, including: Specific speed and polytropic efficiency are calculated based on the structure of the centrifugal compressor to obtain the first performance results of the centrifugal compressor. Based on the turbine structure, the speed coefficient and load coefficient are calculated to obtain the turbine's second performance result; Based on the positional relationship between the first performance result and the first target region, the first coupling result of the centrifugal compressor structure is obtained. The first target region is the curve region corresponding to the target performance parameters characterizing the centrifugal compressor. Based on the positional relationship between the second performance result and the second target region, the second coupling result of the turbine structure is obtained. The second target region is the curve region corresponding to the target performance parameters characterizing the turbine.

[0010] In one optional embodiment, specific speed and polytropic efficiency calculations are performed based on the centrifugal compressor structure to obtain first performance results for the centrifugal compressor, including: The design speed of the centrifugal compressor is obtained based on the outlet diameter and the preset outlet tip velocity characterized by the centrifugal compressor structure. Based on the first density data of the centrifugal compressor and the component outline volume characterized by the centrifugal compressor structure, the weight of the centrifugal compressor blades, impeller disk, and impeller shroud are obtained. The specific speed and polytropic efficiency of the centrifugal compressor are calculated based on the design speed, blade weight, impeller disk weight, and impeller shroud weight to obtain the first performance results characterizing the first coupling result.

[0011] In one alternative embodiment, a second performance result of the turbine is obtained by calculating the speed coefficient and load coefficient based on the turbine structure, including: The weights of each component of the turbine are obtained based on the turbine's second density data and the component profile volume characterized by the turbine structure. Based on the average linear velocity of the turbine at the mid-diameter of the outlet section and the weight of each component, the turbine's velocity coefficient and load coefficient are calculated to obtain a second performance result characterizing the second coupling result.

[0012] In an alternative embodiment, before obtaining the second performance result, the method further includes: The equivalent thickness of the turbine disk is obtained based on the outer diameter of the turbine disk, the blade root stress, and the material yield stress. Based on the equivalent thickness of the turbine disk and the second density data of the turbine, a fitting curve of the equivalent volume of the turbine disk is obtained. The fitting curve is the curve of the turbine's different external dimensions as a function of strength index. When the structural strength and structural design score of the turbine meet the preset requirements based on the fitted curve, the calculation of the second performance result is performed.

[0013] In one optional embodiment, the overall structural design results of the turbojet engine are output, including: Based on the centrifugal compressor structure, turbine structure, and pre-set design database, the intake duct structure and tail nozzle structure of the turbojet engine are obtained. A longitudinal cross-sectional view characterizing the overall structural design is generated based on the structure of all components of the turbojet engine.

[0014] This invention relates to machine learning and deep learning technologies, and has the following beneficial effects: The technical solution of this invention obtains the thermodynamic parameters, target performance parameters, and budget parameters for gas flow path design of a turbojet engine. Based on the thermodynamic and budget parameters, structural profile calculations are performed along the airflow direction of the turbojet engine, enabling rapid acquisition of the centrifugal compressor and turbine structures during the overall design phase. To further analyze structural performance, the design coupling of the centrifugal compressor and turbine structures is verified based on the target performance parameters, yielding a first coupling result for the centrifugal compressor structure and a second coupling result for the turbine structure. During the overall structural design process, factors such as engine performance, materials, structure, aerodynamics, and strength are comprehensively considered. When both the first and second coupling results meet preset targets, the overall structural design result of the turbojet engine is output. This technical solution shortens the design iteration cycle for overall and structural designers during the overall design of turbojet engines, guides them in scheme design, quickly and accurately estimates the dimensions and weight of each component, and adjusts the matching between components. It provides overall and structural designers with a more intuitive overall structural scheme, facilitating optimization and iteration of the engine structure. Practical application shows that the overall structural design error reaches ±3%, improving the efficiency and accuracy of matching the overall structure of the aero-engine with its components. Attached Figure Description

[0015] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A flowchart illustrating the overall structural design method of a micro turbojet engine provided in one embodiment of the present invention; Figure 2 This is a design flowchart of a centrifugal compressor structure provided in one embodiment of the present invention; Figure 3 A design flowchart of a combustion chamber provided for one embodiment of the present invention; Figure 4 A design flowchart of a turbine provided for one embodiment of the present invention; Figure 5 This is a schematic diagram of a first coupling result provided in one embodiment of the present invention; Figure 6 A fitting curve diagram provided for one embodiment of the present invention; Figure 7 This is a schematic diagram of a second coupling result provided in one embodiment of the present invention; Figure 8 This is a schematic diagram of a longitudinal cross-sectional view provided for one embodiment of the present invention. Detailed Implementation

[0017] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the overall structural design method for a micro turbojet engine proposed according to the present invention, including its specific implementation, structure, features, and effects. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0019] In the overall structural design phase of aero-engines, it is necessary to estimate the dimensions of key components and perform overall structural and component matching of the aero-engine parts to shorten the iteration cycle of the overall aero-engine design and improve design efficiency. Current design methods require complex manual calculations, resulting in insufficient matching efficiency and accuracy in this phase. The following embodiments of the present invention will use a micro turbojet engine as an example to specifically illustrate a specific scheme for the overall structural design method of a micro turbojet engine provided by the present invention.

[0020] Please see Figure 1 , Figure 1This is a flowchart illustrating a method for the overall structural design of a micro turbojet engine according to an embodiment of the present invention. This method can be applied to a turbojet engine design terminal, which can be a computer device or a server device capable of running the design method; no specific limitations are imposed here. The design method includes: S11. Obtain the thermodynamic parameters, target performance parameters, and budget parameters for gas flow path design of the turbojet engine.

[0021] Specifically, thermodynamic parameters characterize the energy state of the airflow at key cross-sections along the airflow direction of the turbojet engine. These key cross-sections include the compressor inlet, compressor outlet, combustion chamber outlet, and turbine outlet, and may also include inlet and outlet temperatures, inlet and outlet enthalpies, and inlet and outlet air-fuel ratios. Thermodynamic parameters include Mach number, inlet and outlet flow rates, total inlet and outlet temperature, and total inlet and outlet pressure at each key cross-section. These parameters can be obtained from engine design manuals or empirical data from previous engine models; alternatively, they can be obtained through thermodynamic simulations using software tools. Budget parameters for gas flow path design determine the initial design values ​​for the geometric profile and matching relationships of the turbojet engine's airflow channels, reflecting aerodynamic constraints. These budget parameters include the compressor inlet / outlet hub ratio, number of blades, inlet / outlet outer diameter ratio, and outlet tip velocity limits. These budget parameters can also be obtained from design manuals or empirical values, or they can be calculated based on the turbojet engine's thrust requirements, compressor outlet parameters, and combustion chamber pressure losses. The target performance parameters are the performance parameters required to be achieved in the design of a turbojet engine, such as the specific speed requirement and the engine efficiency. The target performance parameters are used to verify the performance of the turbojet engine in use.

[0022] S12. Calculate the structural profile along the airflow direction of the turbojet engine based on thermodynamic and budget parameters to obtain the centrifugal compressor and turbine structure of the turbojet engine.

[0023] Specifically, during the operation of a turbojet engine, the airflow flows sequentially through the centrifugal compressor, combustion chamber, and turbine. The constraints of the flow path geometry can be determined using the thermodynamic and budget parameters of each cross-section, gradually deriving the geometric dimensions of each component. For example, by using the flow continuity equation, energy conservation equation, and geometric proportional relationships, the inlet and outlet cross-sectional areas, inner and outer diameters, blade heights, and flow path profiles of the centrifugal compressor can be calculated to obtain the centrifugal compressor structure. Using the centrifugal compressor outlet parameters as boundary conditions for the combustion chamber inlet, the ratio of the combustion chamber's annular cross-section to its length can be derived. Using the combustion chamber outlet parameters as boundary conditions for the turbine inlet, the inner and outer diameters, blade heights, and stage structure of the turbine can be further calculated, ultimately obtaining the overall structural dimensions of the centrifugal compressor and turbine.

[0024] For example, step S12 includes sub-steps S12-1 to S12-6, which are described in detail below: S12-1. Extract multiple first target data related to the centrifugal compressor from the thermodynamic parameters and budget parameters, and input them into the first processing model to calculate the component profiles of the centrifugal compressor. Data items for the first target data can be set, data can be extracted from the thermodynamic parameters and budget parameters, and then the component profiles can be calculated based on the first processing model.

[0025] Please see Figure 2 , Figure 2 This is a design flowchart for a centrifugal compressor structure. For example, when multiple primary target data include the centrifugal compressor's inlet Mach number, outlet Mach number, inlet flow rate, outlet flow rate, total inlet and outlet temperature, total inlet and outlet pressure, inlet and outlet oil-gas ratio, blade-to-hub ratio, inlet and outlet outer diameter ratio, and flow path profile equation coefficients, the centrifugal compressor component profile calculation is performed based on the following three steps.

[0026] The first step is to calculate the inlet Mach number, outlet Mach number, inlet flow rate, outlet flow rate, total inlet and outlet temperature, total inlet and outlet pressure, and inlet and outlet oil-gas ratio based on the flow continuity equation to obtain the first inlet cross-sectional area and the first outlet cross-sectional area of ​​the centrifugal compressor.

[0027] The flow continuity equation can be represented by the following formula: ,in, The inflow rate is expressed in kg / s; p For the total pressure of import and export; T The total inlet and outlet temperatures are denoted by λ; q(λ) represents the dimensionless dense flow. Let K be the cross-sectional area of ​​the first inlet; K is an equation constant, K = k × R. For a given gas coefficient k and heat R, which are constants, K is also a constant. For example, for fuel gas, k = 1.33, R = 287.4 J (kg·K), then K = 0.0397. Since the inlet flow rate is known, the cross-sectional area of ​​the first inlet can be calculated based on the flow continuity equation, thus obtaining the first inlet cross-sectional area. .

[0028] Because the following relationship exists , For traffic; ρ is the gas density, which is a constant; v is the gas velocity, which can be obtained from the inlet Mach number and the outlet Mach number. Let [are] the cross-sectional area. The cross-sectional area of ​​the first entrance is [area]. Calculations have shown that the gas is considered incompressible, and the gas flow enters through the inlet of the centrifugal compressor and exits through the outlet. A quantitative relationship exists between the flow rate and volume, from which the first outlet cross-sectional area can be derived. It should be noted that the ratio between the cross-sectional area of ​​the first exit and the cross-sectional area of ​​the first inlet can be derived from the flow rate relationship, which will not be elaborated further here.

[0029] The second step involves obtaining the centrifugal compressor's inlet inner diameter, inlet outer diameter, inlet blade height, outlet diameter, and outlet blade height based on the blade hub ratio, the first inlet cross-sectional area, and the inlet / outlet outer diameter ratio. This can be done using the formula: Calculate the inlet outer diameter D T HTR blade hub ratio; Pi, with a value of 3.14; This is the first inlet cross-sectional area. Due to the blade hub ratio HTR and the inlet / outlet outer diameter D... T It is known that this can be further explained using the formula: Calculate the inlet inner diameter D H Continue according to the formula: , Obtain the imported mean diameter D M Imported blade height H B Through the inlet inner diameter D H The outlet diameter of the centrifugal compressor is calculated by multiplying the inlet and outlet outer diameter ratio. ; Continue based on the formula: = Calculate the outlet blade height H of the centrifugal compressor. Bo .

[0030] The third step involves integrating the flow path profile equation coefficients and the outlet blade height to obtain the impeller flow path profile of the centrifugal compressor. Due to its structural characteristics, the impeller blade profile of the centrifugal compressor is estimated using an inverse proportional function fitting method. The equations for the inner and outer flow path profiles of the centrifugal impeller are as follows: Where a1, b1, a2, b2, c1, and c2 are the parameters of the contour fitting curve in the geometric model; x1 is the axial distance from the tip of the centrifugal impeller outlet blade to the inlet. x1 represents a point on the inner contour line; x2 represents the axial distance from the outlet blade root to the inlet. Points on the outer contour line.

[0031] The volume of a single blade is obtained by integrating the flow path profile: , ,in, For thickness, For the volume of a single blade, For the number of leaves, Let be the material density of the blade. The outer contour of the centrifugal impeller is taken as the inner contour of the blade. A solid impeller is used, and the volume of the impeller is calculated using cylindrical coordinate volume integrals. .in, This is the maximum outer diameter of the centrifugal compressor. This refers to the height of the inlet blades of the centrifugal compressor.

[0032] S12-2. Based on the output of the first processing model, obtain the centrifugal compressor structure and its first outlet cross-sectional area. The first processing model can be constructed based on the relevant formulas for calculating the centrifugal compressor structure mentioned above. After inputting the corresponding data into the first processing model, the centrifugal compressor structure and its first outlet cross-sectional area can be obtained. It should be noted that the centrifugal compressor structure can be represented by data or by visual drawings, and the corresponding data should be marked on the drawings to improve the readability of the centrifugal compressor structure for designers.

[0033] S12-3. Input the first outlet cross-sectional area into the second processing model to calculate the component contours of the combustion chamber. The combustion chamber inlet is connected to the centrifugal compressor outlet. The length of the combustion chamber consists of multiple parts, specifically including the main combustion zone, auxiliary combustion zone, and dilution zone. The weight of the combustion chamber consists of the weight of the inner and outer casings, the flame tube, and the fuel nozzles. Please refer to [link / reference]. Figure 3 , Figure 3 The design flow chart for the combustion chamber is consistent with the calculation method for the centrifugal compressor structure. Given the incoming Mach number of the main combustion zone and bypass zone of the combustion chamber, the cross-sectional area of ​​the main combustion zone and bypass zone can be calculated. Therefore, the component contour calculation of the combustion chamber can be performed based on the first outlet cross-sectional area.

[0034] For example, given the first incoming Mach number in the main combustion zone of the combustion chamber, the second incoming Mach number in the bypass zone, and the diameter-to-length ratio of the combustion chamber, the first outlet cross-sectional area of ​​the centrifugal compressor can be calculated based on the first and second incoming Mach numbers, thus obtaining the outer diameter, inner diameter, and height of the combustion chamber; the length of the combustion chamber can be obtained by multiplying the outer diameter by the preset diameter-to-length ratio. This is because the maximum reference ring area of ​​the combustion chamber (i.e., the first outlet cross-sectional area)... The sum of the main combustion zone area and the bypass zone area has the following relationship: , The area of ​​the main combustion zone, The area of ​​the bypass zone can be calculated using the following formula: / 4, / 2, calculate the inner and outer diameters and height of the combustion chamber. In the above formula, D o D is the outer diameter of the combustion chamber. i H is the inner diameter of the combustion chamber. BiThe height of the combustion chamber is given. The ratio between the outer and inner diameters of the combustion chamber can be set according to design requirements. Finally, the lengths of the main combustion zone, auxiliary combustion zone, and dilution zone of the combustion chamber are calculated using empirical formulas to obtain the overall length of the combustion chamber, thus yielding the component profile calculation results. Given the material density of the combustion chamber, its weight can be calculated.

[0035] S12-4. Based on the output of the second processing model, obtain the combustion chamber structure and the second outlet cross-sectional area of ​​the combustion chamber. Similarly, the second processing model can be constructed based on the relevant formulas for calculating the combustion chamber structure mentioned above. After inputting the corresponding data into the second processing model, the combustion chamber structure and its second outlet cross-sectional area can be obtained.

[0036] S12-5. Extract multiple second-objective data related to the turbine from the thermodynamic and budget parameters, and input these data and the second outlet cross-sectional area into the third processing model to calculate the turbine component profiles. Please refer to [link to relevant documentation]. Figure 4 Similar to the compressor inlet calculation method, given the Mach number and cross-sectional parameters of the incoming flow at the turbine inlet and outlet, the cross-sectional area of ​​the turbine inlet and outlet can be calculated. Then, given the hub ratio, the inner and outer diameters of the turbine can be calculated using the formula for calculating the inner and outer diameters of the compressor inlet.

[0037] For example, when multiple secondary target data include the third incoming Mach number at the turbine inlet, the fourth incoming Mach number at the turbine outlet, and the turbine hub ratio, the third outlet cross-sectional area of ​​the turbine can be obtained based on the third incoming Mach number, the fourth incoming Mach number, and the second outlet cross-sectional area; and the inner and outer diameters of the turbine can be obtained based on the third outlet cross-sectional area and the hub ratio.

[0038] S12-6. Obtain the turbine structure based on the output of the third processing model. The third processing model can also be constructed based on the relevant calculation formulas of the turbine structure. Through the output of the third processing model, the relevant external contour of the turbine can be determined, and thus the turbine structure can be obtained.

[0039] At this point, the centrifugal compressor structure and turbine junction of the turbojet engine have been obtained, and we proceed to step S13.

[0040] S13. Verify the design coupling of the centrifugal compressor structure and the turbine structure according to the target performance parameters, so as to obtain the first coupling result of the centrifugal compressor structure and the second coupling result of the turbine structure.

[0041] Specifically, in the overall design phase of a turbojet engine, the components are not designed independently. For example, the centrifugal compressor, combustion chamber, and turbine operate coaxially, and airflow, speed, power, and stress all affect each other. Although the methods mentioned above have calculated the geometric dimensions of each component, the resulting dimensions are only reasonable in the airflow dimension. Due to the weight of the components, it is necessary to verify whether the resulting structure meets the performance requirements through coupling checks. The weights of each component of the centrifugal compressor and turbine can be calculated based on the target performance parameters. Under given operating conditions and speeds, the operating boundaries of the turbojet engine are constrained, and the design coupling verification results are obtained.

[0042] For example, step S13 includes sub-steps S13-1 to S13-4, which are described in detail below: S13-1. Calculate the specific speed and polytropic efficiency based on the centrifugal compressor structure to obtain the initial performance results of the centrifugal compressor. Data variables can be set based on the component names of the centrifugal compressor. The initial density data of the centrifugal compressor can be extracted from the database using the variable names of the data variables. The initial density data represents the density of the materials used in the centrifugal compressor. It should be noted that a centrifugal compressor involves multiple components, and the materials used for each component may have the same density. Alternatively, different materials can be selected based on actual design requirements, and the density data corresponding to each component can be extracted and used as the initial density data.

[0043] Since the external contours of the corresponding components can be determined by analyzing the structure of the centrifugal compressor, the volume of each component can be calculated. Based on the product of the volume and the initial density data, the design weight of each component can be obtained. Simulation calculations can then yield the initial performance results of the centrifugal compressor. Please refer to [link / reference]. Figure 5 , Figure 5 This diagram illustrates the first coupling result, containing a first curve representing a high design level and a second curve representing a low design level. These two curves are derived from statistical parameters based on historical design results of the centrifugal compressor. The first coupling result can be obtained by observing the relative positions of the first performance result with the first and second curves. The first performance result represents the specific speed and polytropic efficiency of the centrifugal compressor, with corresponding coordinates in the diagram. If the coordinates fall between the first and second curves, the centrifugal compressor design is considered reasonable; otherwise, a redesign or partial adjustment of the centrifugal compressor structure is necessary.

[0044] The calculation of the first performance results will be explained in detail below. The design speed of the centrifugal compressor can be obtained based on the outlet diameter and the preset outlet tip velocity, as characterized by the centrifugal compressor structure. The weights of the blades, impeller disk, and impeller shroud are obtained based on the first density data and the component outline volumes characterized by the centrifugal compressor structure. The weights of each component can be derived by multiplying the component outline volume by the first density data. Furthermore, the specific speed and polytropic efficiency of the centrifugal compressor are calculated based on the design speed, blade weight, impeller disk weight, and impeller shroud weight to obtain the first performance results.

[0045] Taking the impeller shroud calculation as an example, the outer contour line of the centrifugal impeller flow path needs to be selected as the inner contour line of the impeller shroud, and the inner surface area of ​​the impeller shroud is calculated using the cylindrical coordinate surface integral method: S z Let be the inner surface area of ​​the impeller shroud, and x be the integral variable. Treating the impeller shroud as a uniform rotating body of constant thickness, its weight can be estimated using the following formula: W z For the impeller shroud weight; ρ z For the first density data, t z The impeller shroud thickness is given. Based on the above method, the weight of other components can be calculated, thus determining the overall structural dimensions and weight of the centrifugal compressor. The specific speed of the centrifugal compressor is calculated using the formula: ,in, Where ΔHS is the specific speed, NT is the isentropic enthalpy drop, Q is the design speed, and NT is the volumetric flow rate. The polytropic efficiency is expressed by the formula: The polytropic efficiency was calculated. ,in, The absolute thermal efficiency is given by p, the specific heat ratio is given by δ, and the total pressure ratio of the centrifugal compressor is given by δ. The first performance result is obtained by performing calculations using the above formulas. The structural design of the centrifugal compressor is then analyzed based on the first performance result.

[0046] S13-2. Calculate the speed coefficient and load coefficient based on the turbine structure to obtain the turbine's secondary performance results. Similarly, the density of the materials used in the turbine design can be determined through the turbine's secondary density data. The turbine's performance varies under different densities, which can then verify whether the turbine meets the design requirements.

[0047] In practical applications, the structural strength and geometry of the turbine disk directly determine the reliability of a turbojet engine during overall design. However, relying solely on thermodynamic parameters and flow path geometry lacks precise verification of the turbine disk's structural strength and mass. Therefore, after obtaining the second density data, this method fits the data relationships based on the turbine disk's outer diameter, blade root stress, and material yield stress to derive the equivalent disk thickness. The equivalent disk thickness characterizes the equivalent load-bearing capacity the disk needs to possess under a given stress constraint. Turbine disks are typically made of nickel-based alloys or iron-nickel-based alloys. This method is based on the turbine disk's outer diameter and blade root stress σ obtained from the flow path design. BP and the yield stress σ of the material REF The equivalent thickness of the turbine disk is determined, and its weight is then calculated. Further, based on the equivalent thickness and second density data, a fitted curve of the turbine disk's equivalent volume is obtained. This fitted curve shows the variation of different turbine dimensions with strength indicators. Please refer to [link / reference]. Figure 6 , Figure 6 This is a schematic diagram of the variation curve. The horizontal axis represents the turbine disk load, and the vertical axis represents the equivalent thickness of the turbine disk. This curve reflects the volumetric behavior of different external dimensions as the strength index changes. Furthermore, based on the fitted curve, it can be determined whether the turbine's structural strength and structural design score meet the preset requirements. If the design requirements are met, the calculation of the second performance result is performed.

[0048] Based on the turbine's second density data and turbine structure, the second performance results can be obtained, which are the turbine's speed coefficient and load coefficient. Similarly, the cross-sectional area of ​​the corresponding components can be determined through the turbine structure, and the component volume can be calculated further using the cross-sectional area and component shape. The weight of each component is then obtained by multiplying the component volume by the second density data. After obtaining the turbine structure and component weights, motion simulation of the turbine is performed to obtain the second performance results.

[0049] Furthermore, the second performance result can be obtained by first calculating the weight of each turbine component based on the second density data and the component profile volume characterized by the turbine structure. The weight of each component includes the weight of the blades, the disk, the connecting parts, and the brakes. Then, based on the average linear velocity of the turbine at the mid-diameter of the outlet section and the weight of each component, the turbine's velocity coefficient and load coefficient are calculated to obtain the second performance result.

[0050] The velocity coefficient is a dimensionless parameter in aerodynamics, which can be derived from the ratio of the turbine's design speed to the critical speed of sound, and will not be elaborated further here. The turbine's load factor is denoted as Y. , This formula is used for calculations involving gas turbines. Wherein, The total enthalpy change per unit weight of air is approximately equal to the turbine rim work, and its unit is (J / kg); UM,exit Z represents the average linear velocity at the median diameter of the turbine exit section; Z represents the number of turbine stages; Y represents the average linear velocity at the median diameter of the turbine exit section. The average load factor characterizes the turbine, and its value is generally in the range of 3.0 to 4.5. In the design, the selected Y... Z calculates U M,exit Then, calculate the turbine's AN using the following formula. 2 Value (a parameter characterizing the stress of turbine blades). ,in, ε For stress parameters, A The turbine outlet cross-sectional area is... N This is the engine's design speed. Continuing based on the formula: Calculate the number of leaves , where D T Where A is the inlet outer diameter, AR is the blade aspect ratio, and N is the inlet outer diameter. B Where C is the number of blades, C / S is the density of the foliage, and H is the number of blades. B H is the leaf height of the leaf blade. B It represents the distance from the leaf root to the leaf tip.

[0051] It is understandable that for a single blade, its equivalent volume needs to be calculated first, and then its weight can be calculated based on its density. Given the known blade structural parameters (blade height, aspect ratio), the blade is simplified into a cuboid to calculate its equivalent volume, and the calculation formula is shown below. , where V B Equivalent volume, H B Where is the leaf height; AR is the leaf aspect ratio; K0 is an empirical parameter, determined according to the following rules:

[0052] S13-3. Based on the positional relationship between the first performance result and the first target region, the first coupling result of the centrifugal compressor structure is obtained. The first target region is the curve region corresponding to the target performance parameters characterizing the centrifugal compressor. Please continue reading. Figure 5 The two curves in the figure represent different design levels, and the area between the two curves is the first target area. This target area is the curve area, which represents the target performance required to be achieved by the centrifugal compressor. The first coupling result can be obtained based on the relationship between the calculated first performance result and the first target area.

[0053] S13-4. Based on the positional relationship between the second performance result and the second target region, obtain the second coupling result of the turbine structure. The second target region is the curve region corresponding to the target performance parameters characterizing the turbine. Similarly, please refer to... Figure 7The curves in the figure are the efficiency contour lines (or isentropic efficiency lines) of the turbojet engine. The region with an efficiency greater than 90% can be set as the second target region. This target region is also a curve region, which represents the target performance required to be achieved by the turbine design. The second coupling result is obtained based on the relationship between the second performance result and the second target region.

[0054] At this point, the first coupling result and the second coupling result have been obtained, and we proceed to step S14 or S15.

[0055] S14. If the first coupling result or the second coupling result does not meet the preset target, update the corresponding parameters, recalculate and verify the design structure of the turbojet engine.

[0056] For details, please continue reading. Figure 5 When the first performance result A2 is below the second curve, it indicates that the first coupling result does not meet the preset target. When the first performance result is between the first and second curves, as shown by position A1 in the figure, it indicates that the first coupling result meets the preset target. Similarly, Figure 7 Different curves represent the corresponding engine efficiencies. An efficiency threshold can be set as a preset target for the second coupling result. For example, if the second performance result B2 is within 90%, it indicates that the turbine has high performance, and the second coupling result meets the preset target. If the second performance result B1 is outside 90%, it indicates that the turbine design does not meet the requirements. If either the first or second coupling result fails to meet the corresponding preset target, it indicates that the parameter settings are unreasonable. The corresponding parameters are then reset, the structural calculation is performed, and the results are re-verified until both the first and second coupling results meet the preset targets.

[0057] S15. When both the first coupling result and the second coupling result meet the preset target, output the overall structural design result of the turbojet engine.

[0058] Specifically, the structural designs of the centrifugal compressor, combustion chamber, and turbine are interconnected. If both the first and second coupling results meet the preset targets, it indicates that the geometry, airflow channel distribution, and operational performance of the three components meet the design requirements. Based on the integrated data, a complete overall structural design result for the turbojet engine is output, facilitating further design by the designers. The overall structural design result can be a numerical table summarizing key parameters or a visual structural diagram, which can be used by overall and structural designers for subsequent optimization and detailed design.

[0059] Based on the above scheme, although the structural profiles and coupling verification results of the centrifugal compressor and turbine have been obtained, to complete the structural finalization of the entire engine, the structures of other components still need to be supplemented. However, manual calculations by designers affect design efficiency and accuracy. Therefore, in a specific implementation, the overall structural design results of the turbojet engine are output, including: S15-1. Based on the centrifugal compressor structure, turbine structure, and a pre-defined design database, obtain the inlet structure and exhaust nozzle structure of the turbojet engine. The inlet area can be determined from the outer diameter, flow parameters, and Mach number of the centrifugal compressor inlet. Using empirical formulas in the design database for the diffusion ratio, guide cone angle, and length ratio at different Mach numbers, calculate the variation curves of the inlet's expansion section length and inner diameter; thereby obtaining the structural profile of the inlet and the geometry of the connecting transition section. Similarly, based on the turbine outlet cross-sectional area, exhaust temperature, and flow data, retrieve the optimal contraction ratio and nozzle expansion angle from the design database; calculate the exhaust nozzle throat diameter, outlet diameter, and contraction section length; and output the corresponding parameters of the exhaust nozzle structure.

[0060] S15-2. Generate a longitudinal cross-sectional view characterizing the overall structural design based on the structure of all components of the turbojet engine. (See also...) Figure 8 , Figure 8 This is a longitudinal cross-sectional view of a turbojet engine. The horizontal axis represents the length of the turbojet engine, and the vertical axis represents its width. This view can be directly used as input data for CFD (Computational Fluid Dynamics) simulations and FEA (Finite Element Analysis) strength analyses, further improving the design efficiency of turbojet engines. The longitudinal cross-sectional view allows for visual analysis of whether various parameters are within reasonable ranges. Design verification can be performed using the dimensional parameters of each component, enabling overall and structural designers to intuitively see the flow path of the designed turbojet engine and avoid problems with unreasonable structural design. It also serves as a design reference for component designers during detailed component design.

[0061] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0062] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A method for overall structural design of a micro turbojet engine, characterized in that, The method includes: Obtain the thermodynamic parameters, target performance parameters, and budget parameters for gas flow path design of the turbojet engine; The structural profile of the turbojet engine is calculated along the airflow direction based on the thermodynamic parameters and the budget parameters to obtain the centrifugal compressor structure and turbine structure of the turbojet engine. The design coupling of the centrifugal compressor structure and the turbine structure is verified based on the target performance parameters to obtain a first coupling result of the centrifugal compressor structure and a second coupling result of the turbine structure. If the first coupling result or the second coupling result does not meet the preset target, update the corresponding parameters and recalculate and verify the design structure of the turbojet engine. When both the first coupling result and the second coupling result meet the preset target, the overall structural design result of the turbojet engine is output.

2. The overall structural design method for the micro turbojet engine according to claim 1, characterized in that, The step of calculating the structural profile along the airflow direction of the turbojet engine based on the thermodynamic parameters and the budget parameters to obtain the centrifugal compressor structure and turbine structure of the turbojet engine includes: Multiple first target data associated with the centrifugal compressor are extracted from the thermodynamic parameters and the budget parameters, and input into the first processing model to solve the component contours of the centrifugal compressor; Based on the output of the first processing model, the centrifugal compressor structure and the first outlet cross-sectional area of ​​the centrifugal compressor are obtained; The first outlet cross-sectional area is input into the second processing model to calculate the component contours of the combustion chamber; Based on the output of the second processing model, the combustion chamber structure and the second outlet cross-sectional area of ​​the combustion chamber are obtained; Multiple second target data associated with the turbine are extracted from the thermodynamic parameters and the budget parameters, and the multiple second target data and the second outlet cross-sectional area are input into the third processing model to solve the component profile of the turbine. The turbine structure is obtained based on the output of the third processing model.

3. The overall structural design method for the micro turbojet engine according to claim 2, characterized in that, The multiple first target data include the centrifugal compressor's inlet Mach number, outlet Mach number, inlet flow rate, outlet flow rate, total inlet and outlet temperature, total inlet and outlet pressure, inlet and outlet oil-gas ratio, blade-to-hub ratio, inlet and outlet outer diameter ratio, and flow path profile equation coefficients. Multiple target data points are input into the first processing model to calculate the component profiles of the centrifugal compressor, including: The inlet Mach number, the outlet Mach number, the inlet flow rate, the outlet flow rate, the total inlet and outlet temperature, the total inlet and outlet pressure, and the inlet and outlet oil-gas ratio are processed according to the flow continuity equation to obtain the first inlet cross-sectional area and the first outlet cross-sectional area of ​​the centrifugal compressor. The inlet inner diameter, inlet outer diameter, inlet blade height, outlet diameter, and outlet blade height of the centrifugal compressor are obtained based on the blade hub ratio, the first inlet cross-sectional area, and the inlet / outlet outer diameter ratio. The impeller flow path profile of the centrifugal compressor is obtained by integrating the flow path profile equation coefficients and the outlet blade height.

4. The overall structural design method for the micro turbojet engine according to claim 2, characterized in that, The step of inputting the first outlet cross-sectional area into the second processing model to calculate the component contours of the combustion chamber includes: The outer diameter, inner diameter, and height of the combustion chamber are obtained based on the first outlet cross-sectional area. The length of the combustion chamber is obtained based on its outer diameter and a preset diameter-to-length ratio.

5. The overall structural design method for the micro turbojet engine according to claim 2, characterized in that, The multiple second target data include the third incoming Mach number at the turbine inlet, the fourth incoming Mach number at the turbine outlet, and the turbine's hub ratio; Multiple second target data and the second outlet cross-sectional area are input into a third processing model to calculate the component profiles of the turbine, including: The third outlet cross-sectional area of ​​the turbine is obtained based on the third incoming Mach number, the fourth incoming Mach number, and the second outlet cross-sectional area. The inner and outer diameters of the turbine are obtained based on the third outlet cross-sectional area and the hub ratio.

6. The overall structural design method for the micro turbojet engine according to claim 1, characterized in that, The step of verifying the design coupling of the centrifugal compressor structure and the turbine structure based on the target performance parameters to obtain a first coupling result for the centrifugal compressor structure and a second coupling result for the turbine structure includes: Based on the centrifugal compressor structure, specific speed and polytropic efficiency are calculated to obtain the first performance result of the centrifugal compressor; Based on the turbine structure, the speed coefficient and load coefficient are calculated to obtain the second performance result of the turbine. Based on the positional relationship between the first performance result and the first target region, a first coupling result of the centrifugal compressor structure is obtained, wherein the first target region is the curve region corresponding to the target performance parameters characterizing the centrifugal compressor. Based on the positional relationship between the second performance result and the second target region, a second coupling result of the turbine structure is obtained, wherein the second target region is the curve region corresponding to the target performance parameter of the turbine.

7. The overall structural design method for the micro turbojet engine according to claim 6, characterized in that, Based on the centrifugal compressor structure, specific speed and polytropic efficiency are calculated to obtain the first performance results of the centrifugal compressor, including: The design speed of the centrifugal compressor is obtained based on the outlet diameter and the preset outlet tip velocity characterized by the centrifugal compressor structure. Based on the first density data of the centrifugal compressor and the component outline volume characterized by the structure of the centrifugal compressor, the blade weight, impeller disk weight, and impeller shroud weight of the centrifugal compressor are obtained. The specific speed and variable efficiency of the centrifugal compressor are calculated based on the design speed, the blade weight, the impeller disk weight, and the impeller shroud weight to obtain the first performance result.

8. The overall structural design method for the micro turbojet engine according to claim 6, characterized in that, The calculation of the speed coefficient and load coefficient based on the turbine structure to obtain the second performance result of the turbine includes: The weights of each component of the turbine are obtained based on the second density data of the turbine and the component outline volume characterized by the turbine structure. Based on the average linear velocity of the turbine at the mid-diameter of the outlet section and the weight of each component, the speed coefficient and load coefficient of the turbine are calculated to obtain the second performance result.

9. The overall structural design method for the micro turbojet engine according to claim 6, characterized in that, Before obtaining the second performance result, the method further includes: The equivalent thickness of the turbine disk is obtained based on the outer diameter of the turbine disk, the blade root stress, and the material yield stress. Based on the equivalent thickness of the turbine disk and the second density data of the turbine, a fitting curve of the equivalent volume of the turbine disk is obtained. The fitting curve is a curve showing the change of different external dimensions of the turbine with strength index. When the structural strength and structural design score of the turbine meet the preset requirements based on the fitted curve, the calculation of the second performance result is performed.

10. The overall structural design method for the micro turbojet engine according to claim 1, characterized in that, Output the overall structural design results of the turbojet engine, including: Based on the centrifugal compressor structure, the turbine structure, and the preset design database, the intake duct structure and tail nozzle structure of the turbojet engine are obtained. A longitudinal cross-sectional view characterizing the overall structural design is generated based on the structure of all components of the turbojet engine.

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