Simplified calculation method for aero-engine outer culvert flow resistance

Abstract

The invention belongs to the field of gas turbine engines, and particularly relates to a simplified calculation method for aero-engine outer culvert flow resistance, when the engine outer culvert flow resistance is calculated, a complex outer culvert structure is split, a whole outer culvert simulation model does not need to be established, M * N outer culvert sectors are used for replacement, the size of the simulation model is reduced, and the calculation efficiency is improved. And the maximum grid quantity of simulation calculation is reduced, so that the simulation problem which can only be solved by a computer cluster or supercomputing originally can be solved by a single machine. After the structure of the outer culvert is split, flow resistance data is obtained through parts developed by accessories such as a duct heat exchanger, a borescope and a pipeline in outer culvert sectors, part-level conversion flow-relative resistance loss correlation correction is achieved, and the utilization rate of test data can be improved.

Description

Technical Field

[0001] The present application belongs to the field of gas turbine engines, and in particular relates to a simplified calculation method for flow resistance of an aircraft engine duct. Background Art

[0002] In order to meet the heat dissipation requirements of advanced aircraft engine thermal management, a duct heat exchanger is usually arranged in the engine duct, especially for engines with a second outer duct. The arrangement of accessories such as duct heat exchangers in the duct will increase the flow resistance of the engine outer duct, increase the complexity of the outer duct model, and make it more difficult to evaluate the flow resistance of the engine outer duct. Accurate engine outer duct flow resistance data is required to evaluate the overall performance of the engine. Therefore, it is necessary to establish a simplified calculation method for the flow resistance of the engine outer duct that can solve the outer duct with a large macroscopic structure and the inner duct with complex structural accessories.

[0003] The existing method for evaluating the flow resistance of the culvert is to ignore the accessories in the culvert flow channel. The ignored accessories include the duct heat exchanger, borescope, pipeline, test sensor, adjustment structure and other accessories outside the culvert casing in the culvert flow channel. Only the flow resistance caused by the sudden expansion and contraction along the culvert casing or locally at typical state points is evaluated.

[0004] The advantage of the existing technical solution is that the evaluation model structure is simple and can carry out the flow resistance calculation of the complete outer duct. The disadvantage is that the calculation results of the simplified model cannot truly reflect the outer duct flow resistance generated by the actual structure. When the real model is used, the required calculation grid is too large and requires a computer cluster to carry out. The calculation cost increases and the calculation cycle becomes longer.

[0005] Therefore, how to reflect the external flow resistance generated by the actual structure through a simplified model is a problem that needs to be solved. Summary of the invention

[0006] The purpose of this application is to provide a simplified calculation method for the flow resistance of the external duct of an aircraft engine, so as to solve the problem that the calculation results of the current simplified model cannot truly reflect the flow resistance of the external duct generated by the actual structure.

[0007] The technical solution of the present application is: a simplified calculation method for the flow resistance of the outer duct of an aero-engine, comprising:

[0008] The engine outer duct is divided into blocks, and the outer duct and internal accessories are divided into M sections along the axial direction and N sections evenly along the circumferential direction. The total number of sections is M×N small structural modules, and each structural module is an outer duct sector. The structural parameters and boundary conditions of each outer duct sector are obtained, wherein M and N are positive integers, and the boundary conditions include pressure boundary conditions, symmetric boundary conditions and adiabatic boundary conditions; the structural parameters and boundary conditions of each outer duct sector are obtained, and a three-dimensional flow simulation model is established for each outer duct sector respectively. The accessories contained in the outer duct sector are modeled according to the real structure, and the relative resistance loss △Pr and the converted flow rate Gh of each outer duct sector are set. The flow resistance characteristics of each outer duct sector are calculated through the three-dimensional flow simulation model, and then the converted flow rate-relative resistance loss curve of each outer duct sector is calculated according to the flow resistance characteristics;

[0009] Calculate the converted flow-relative resistance loss curve of the outer duct ring section according to the converted flow-relative resistance loss curve of each outer duct sector section;

[0010] The converted flow-relative resistance loss curves of all culvert segments are fitted through the loss correlation formula to obtain the converted flow-relative resistance loss correlation formula of the complete culvert, and a high-precision culvert flow resistance simulation model is obtained through the converted flow-relative resistance loss correlation formula of the complete culvert.

[0011] Preferably, when segmenting in the axial direction, 6≥M≥1 is used, and uneven segmentation is performed in the axial direction; when segmenting in the circumferential direction, 36≥N≥1 is used, and uniform segmentation is performed in the circumferential direction.

[0012] Preferably, in the three-dimensional flow simulation model, the inlet of the outer duct sector is a pressure boundary condition, the outlet of the outer duct sector is a pressure boundary condition, the left and right sides of the sector are circumferentially periodic symmetrical boundary conditions, and the upper and lower surfaces of the outer duct sector are adiabatic boundary conditions.

[0013] Preferably, when there are completely identical outer duct sector structures in the circumferential direction, the flow resistance characteristic result data of the same structure are used.

[0014] Preferably, the specific calculation method of the flow resistance characteristics is: setting a series of simulation examples according to the boundary conditions of the relative resistance loss △Pr from small to large, each boundary condition is used as a simulation state point, and the inlet and outlet boundary conditions of the outer duct sector corresponding to different simulation examples are calculated respectively, and then the converted flow corresponding to the different outer duct sector is calculated according to the different inlet and outlet boundary conditions of the outer duct sector, and the calculation result data is extracted and sorted to obtain the converted flow-relative resistance loss curve of each outer duct sector.

[0015] Preferably, the maximum relative resistance loss △Pr set in the simulation example is greater than or equal to the maximum value that may occur in actual working conditions; the number of simulation state points carried out for a single outer duct sector is no less than 4, and the relative resistance loss △Pr takes values ​​of 0.2%, 0.5%, 2%, 5%, and 10%.

[0016] Preferably, the specific method for calculating the converted flow-relative resistance loss curve of the outer duct segment is: superimpose the flow resistance characteristics of the N outer duct segments at the first axial position to obtain the flow resistance characteristics of a single outer duct segment; when superimposing, superimpose the converted flow-relative resistance loss curves of multiple outer duct segments, and superimpose the converted flow under the same relative resistance loss between multiple curves to obtain the flow resistance characteristics of the outer duct of the ring segment at the first axial position; repeat this process, and then cyclically process the remaining M-1 outer duct segments according to the same method to obtain the converted flow-relative resistance loss curves of the remaining outer duct segments.

[0017] Preferably, the specific method for obtaining the loss correlation of the converted flow-relative resistance loss curve of each outer ring segment is: fitting the converted flow-relative resistance loss curve of each outer ring segment to obtain the converted flow-relative resistance loss correlation of each outer ring segment; the maximum deviation between the fitted loss correlation and the original data point is not less than 3%; the resistance loss correlation of the first outer ring segment is △Pr=f1(Gh), and the resistance loss correlation of the Mth outer ring segment is △Pr=f M (Gh).

[0018] Preferably, the specific method for obtaining the complete external converted flow-relative resistance loss correlation formula is:

[0019] Starting from the windward side of the culvert, the converted flow-relative resistance loss correlation equations of the first and second culvert segments are superimposed. The total converted flow-relative resistance loss correlation equation of the first two culvert segments is △Pr=F 1～2 (Gh)=f1(Gh)+(1-f1(Gh))×f2(Gh);

[0020] The converted flow-relative resistance loss correlation equations of the first three outer circumference ring sections are superimposed, and the total converted flow-relative resistance loss correlation equation of the first three outer circumference ring sections is △Pr=F 1～3 (Gh)=F 1～2 (Gh)+(1-F 1～2 (Gh))×f3(Gh);

[0021] By analogy, the total converted flow-relative resistance loss relationship of the first M outer circumference ring sections is △Pr=F M (Gh)=F 1～M-1 (Gh)+(1-F 1～M-1 (Gh))×fM (Gh), that is, to obtain the complete external conversion flow-relative resistance loss correlation formula △Pr=F M (Gh).

[0022] The simplified calculation method of the flow resistance of the aero-engine duct in this application has the following gain effects:

[0023] 1. When calculating the flow resistance of the engine duct, the complex duct structure is split. There is no need to build the entire duct simulation model. Instead, it is replaced by M×N duct sectors, which reduces the size of the simulation model and the maximum grid size of the simulation calculation. This allows simulation problems that could only be solved by computer clusters or supercomputers to be solved by a single machine.

[0024] 2. It is easy to correct the flow resistance characteristics of the outer culvert. The calculation of the outer culvert flow resistance simulation model requires correction by test results. If the simulation model of the outer culvert is not split, there are many factors affecting the flow resistance of the outer culvert, and it is impossible to effectively use the test data of a single accessory for correction. After the structure of the outer culvert is split, the flow resistance data obtained from the components of the duct heat exchanger, borescope, pipeline and other accessories installed in the outer culvert sector can be effectively used to realize the component-level conversion flow-relative resistance loss correlation correction, which is conducive to improving the utilization rate of test data.

[0025] 3. Use dimensionless converted flow-relative resistance loss curve and correlation. In actual use, the temperature, pressure, flow, and resistance loss of the engine's outer inlet change with the engine state. Using dimensionless converted flow and relative resistance loss can reduce the number of simulations and improve calculation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solution provided by the present application, the following is a brief introduction to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present application.

[0027] Figure 1 This is a schematic diagram of the overall process of this application;

[0028] Figure 2 This is a schematic diagram of the application's sub-segmentation;

[0029] Figure 3 This is a schematic diagram of the division of attachments within the scope of this application;

[0030] Figure 4 This is a schematic diagram of the boundary conditions of the three-dimensional flow simulation model of this application;

[0031] Figure 5 This is a schematic diagram of the converted flow-relative resistance loss curve of a single ductile fan section in this application;

[0032] Figure 6 This is the converted flow-relative resistance loss curve of a single outer ring segment in this application. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] The current engine duct is an axisymmetric annular channel, which contains a series of accessories, such as duct heat exchanger, borescope, pipeline, test sensor, adjustment structure, etc. In the design stage of the engine, in order to obtain accurate overall performance design results, it is necessary to calculate the flow resistance characteristics of the duct.

[0035] Therefore, a simplified calculation method for the flow resistance of the outer duct of an aircraft engine is designed. Figure 1 As shown, the specific steps include:

[0036] Step S100, as Figure 2 In order to reduce the simulation model size of the entire engine shroud, the engine shroud is divided into blocks. The shroud and internal accessories are divided into M segments along the axial direction and N segments evenly along the circumferential direction. The total number of segments is M×N small structural modules. Each structural module is a shroud sector, and the structural parameters and boundary conditions of each shroud sector are obtained, where M and N are positive integers, and the boundary conditions include pressure boundary conditions, symmetric boundary conditions and adiabatic boundary conditions.

[0037] The requirement for segmentation in the axial direction is M≥1. Uniform segmentation is not required in the axial direction, that is, uniform segmentation or uneven segmentation is possible. The upper limit of the axial segmentation M is 6.

[0038] The requirement for segmentation in the circumferential direction is N ≥ 1, and uniform segmentation is required in the circumferential direction to form a symmetrical circumferential boundary. The upper limit of circumferential segmentation is 36 segments.

[0039] like Figure 3 When performing circumferential segmentation, try to ensure that individual accessories are divided into separate outer culvert sectors, and try to avoid cutting accessories at the sector interface.

[0040] Step S200, obtain the structural parameters and boundary conditions of each duct sector, establish a three-dimensional flow simulation model for each duct sector, model the accessories contained in the duct sector according to the real structure, set the relative resistance loss △Pr and converted flow rate Gh of each duct sector, calculate the flow resistance characteristics of each duct sector through the three-dimensional flow simulation model, and then calculate the converted flow rate-relative resistance loss curve of each duct sector based on the flow resistance characteristics.

[0041] In the three-dimensional flow simulation model, the inlet and outlet of the culvert fan segment are pressure boundary conditions, the left and right sides of the fan segment are circumferentially periodic symmetrical boundary conditions, and the upper and lower surfaces of the culvert fan segment are adiabatic boundary conditions.

[0042] For the setting of boundary conditions of a single outer duct sector, see Figure 4 When there are completely identical outer duct sector structures in the circumferential direction, the flow resistance characteristic result data of the same structure is used to improve efficiency.

[0043] The relative resistance loss △Pr and the converted flow rate Gh are defined as:

[0044] △Pr=1-Pout / Pin (1)

[0045]

[0046] Where: Pout is the total outlet pressure of the culvert fan section, in Pa;

[0047] Pin is the total inlet pressure of the duct fan section, in Pa;

[0048] G is the physical flow rate of the outer fan section, in kg / s;

[0049] Tin is the total inlet air temperature of the outer fan section, in K.

[0050] The specific calculation method of the flow resistance characteristics is as follows: in order to obtain the resistance characteristics of the outer duct sector, a series of simulation examples are set according to the boundary conditions of the relative resistance loss △Pr from small to large. Each boundary condition is used as a simulation state point. The inlet and outlet boundary conditions of the outer duct sector corresponding to different simulation examples are calculated respectively. Then, the converted flow corresponding to different outer duct sectors is calculated according to the different inlet and outlet boundary conditions of the outer duct sector. The calculation result data is extracted and sorted out to obtain the converted flow-relative resistance loss curve of each outer duct sector.

[0051] Preferably, the maximum relative resistance loss ΔPr set in the simulation example is greater than or equal to the maximum value that may occur in actual working conditions.

[0052] Preferably, the number of simulation state points carried out for a single outer duct sector is no less than 4, and the recommended series of relative resistance loss △Pr values ​​are 0.2%, 0.5%, 2%, 5%, and 10%.

[0053] After completing a series of simulation calculations for a single duct sector, extract the calculation result data and draw the converted flow-relative resistance loss curve of a single duct sector. Figure 5 .

[0054] Step S300, calculating the converted flow-relative resistance loss curve of the outer duct segment according to the converted flow-relative resistance loss curve of each outer duct segment

[0055] Specifically, the flow resistance characteristics of the N outer duct sectors at the first axial position are superimposed to obtain the flow resistance characteristics of a single outer duct ring segment. When superimposing, the converted flow-relative resistance loss curves of multiple outer duct sectors are superimposed, and the converted flow under the same relative resistance loss between multiple curves is superimposed to obtain the flow resistance characteristics of the outer duct of the ring segment at the first axial position. Then, the remaining M-1 outer duct ring segments are cyclically processed according to the same method to obtain the converted flow-relative resistance loss curves of the remaining outer duct ring segments.

[0056] Step S400, determining the loss correlation equation of the converted flow-relative resistance loss curve of each outer ring segment;

[0057] like Figure 6 Specifically, the converted flow-relative resistance loss curve of each outer ring segment is fitted to obtain the converted flow-relative resistance loss correlation formula of each outer ring segment. The maximum deviation between the fitted loss correlation formula and the original data point should be no less than 3%. The resistance loss correlation formula of the first outer ring segment is △Pr=f1(Gh), and the resistance loss correlation formula of the Mth outer ring segment is △Pr=f M (Gh).

[0058] Step S500, fitting the converted flow-relative resistance loss curves of all culvert segments through the loss correlation equation to obtain the converted flow-relative resistance loss correlation equation of the complete culvert, and obtaining a high-precision culvert flow resistance simulation model through the converted flow-relative resistance loss correlation equation of the complete culvert.

[0059] Specifically, starting from the windward side of the culvert, the converted flow-relative resistance loss correlation equations of the first and second culvert segments are superimposed. The total converted flow-relative resistance loss correlation equation of the first two culvert segments is △Pr=F 1～2 (Gh)=f1(Gh)+(1-f1(Gh))×f2(Gh).

[0060] The converted flow-relative resistance loss correlation equations of the first three outer circumference ring sections are superimposed, and the total converted flow-relative resistance loss correlation equation of the first three outer circumference ring sections is △Pr=F 1～3 (Gh)=F 1～2 (Gh)+(1-F 1～2 (Gh))×f3(Gh).

[0061] By analogy, the total converted flow-relative resistance loss relationship of the first M outer circumference ring sections is △Pr=F M (Gh)=F 1～M-1 (Gh)+(1-F 1～M-1 (Gh))×f M (Gh), that is, to obtain the complete external conversion flow-relative resistance loss correlation formula △Pr=F M (Gh).

[0062] In summary, the gain effects of this application are as follows:

[0063] 1. When calculating the flow resistance of the engine duct, the complex duct structure is split. There is no need to build the entire duct simulation model. Instead, it is replaced by M×N duct sectors, which reduces the size of the simulation model and the maximum grid size of the simulation calculation. This allows simulation problems that could only be solved by computer clusters or supercomputers to be solved by a single machine.

[0064] 2. It is easy to correct the flow resistance characteristics of the outer culvert. The calculation of the outer culvert flow resistance simulation model requires correction by test results. If the simulation model of the outer culvert is not split, there are many factors affecting the flow resistance of the outer culvert, and it is impossible to effectively use the test data of a single accessory for correction. After the structure of the outer culvert is split, the flow resistance data obtained from the components of the duct heat exchanger, borescope, pipeline and other accessories installed in the outer culvert sector can be effectively used to realize the component-level conversion flow-relative resistance loss correlation correction, which is conducive to improving the utilization rate of test data.

[0065] 3. Use dimensionless converted flow-relative resistance loss curve and correlation. In actual use, the temperature, pressure, flow, and resistance loss of the engine's outer inlet change with the engine state. Using dimensionless converted flow and relative resistance loss can reduce the number of simulations and improve calculation efficiency.

[0066] 4. Establish a modular flow resistance superposition method between culvert sectors. Split the complete culvert into M×N culvert sectors, use the conversion flow-relative resistance loss curve superposition method in the circumferential direction, and use the correlation superposition method in the circumferential direction to establish the correlation between the flow resistance characteristics of the M×N culvert sectors and the flow resistance characteristics of the complete culvert.

[0067] Finally, it should be noted that: the drawings of the embodiments disclosed in the present invention only involve structures related to the embodiments disclosed in the present invention, and other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of the present invention can be combined with each other;

[0068] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A simplified calculation method for the flow resistance of an aircraft engine, characterized in that: include: The engine outer shroud is divided into blocks, the outer shroud and internal accessories are divided into M sections along the axial direction, and N sections are evenly divided into circumferential directions. The total number of sections is M×N small structural modules, each structural module is an outer shroud sector, and the structural parameters and boundary conditions of each outer shroud sector are obtained, where M and N are positive integers, and the boundary conditions include pressure boundary conditions, symmetric boundary conditions and adiabatic boundary conditions; The structural parameters and boundary conditions of each culvert sector are obtained, and a three-dimensional flow simulation model is established for each culvert sector. The accessories contained in the culvert sector are modeled according to the real structure. The relative resistance loss △Pr and the converted flow rate Gh of each culvert sector are set. The flow resistance characteristics of each culvert sector are calculated through the three-dimensional flow simulation model, and then the converted flow rate-relative resistance loss curve of each culvert sector is calculated according to the flow resistance characteristics. Calculate the converted flow-relative resistance loss curve of the outer duct ring section according to the converted flow-relative resistance loss curve of each outer duct sector section; Determine the loss correlation of the converted flow-relative resistance loss curve for each outer ring segment; The converted flow-relative resistance loss curves of all culvert segments are fitted through the loss correlation formula to obtain the converted flow-relative resistance loss correlation formula of the complete culvert, and a high-precision culvert flow resistance simulation model is obtained through the converted flow-relative resistance loss correlation formula of the complete culvert.

2. The simplified calculation method of the flow resistance of the aero-engine duct as claimed in claim 1, characterized in that: When axial segmentation is performed, 6≥M≥1, and uneven segmentation is performed in the axial direction; when circumferential segmentation is performed, 36≥N≥1, and uniform segmentation is performed in the circumferential direction.

3. The simplified calculation method of the flow resistance of the aero-engine duct as claimed in claim 1, characterized in that: In the three-dimensional flow simulation model, the inlet of the duct segment is a pressure boundary condition, the outlet of the duct segment is a pressure boundary condition, the left and right sides of the segment are circumferentially periodic symmetrical boundary conditions, and the upper and lower surfaces of the duct segment are adiabatic boundary conditions.

4. The simplified calculation method of the flow resistance of the aero-engine duct as claimed in claim 1, characterized in that: When there are completely identical outer circumferential sector structures, the flow resistance characteristic result data of the same structure shall be used.

5. The simplified calculation method of the flow resistance of the aero-engine duct as claimed in claim 1, characterized in that: The specific calculation method of the flow resistance characteristics is: a series of simulation examples are set according to the boundary conditions of the relative resistance loss △Pr from small to large, each boundary condition is used as a simulation state point, and the inlet and outlet boundary conditions of the outer duct sector corresponding to different simulation examples are calculated respectively, and then the converted flow corresponding to different outer duct sector is calculated according to the different inlet and outlet boundary conditions of the outer duct sector, and the calculation result data is extracted and sorted to obtain the converted flow-relative resistance loss curve of each outer duct sector.

6. The simplified calculation method of the flow resistance of the aero-engine duct as claimed in claim 5, characterized in that: The maximum relative resistance loss △Pr set in the simulation example is greater than or equal to the maximum value that may occur in actual working conditions; The number of simulation state points carried out for a single duct sector is no less than 4, and the relative resistance loss △Pr is taken as 0.2%, 0.5%, 2%, 5% and 10%.

7. The simplified calculation method of the flow resistance of the aero-engine duct as claimed in claim 1, characterized in that: The specific method for calculating the converted flow-relative resistance loss curve of the outer duct segment is as follows: superimpose the flow resistance characteristics of the N outer duct segments at the first axial position to obtain the flow resistance characteristics of a single outer duct segment; when superimposing, superimpose the converted flow-relative resistance loss curves of multiple outer duct segments, and superimpose the converted flow under the same relative resistance loss between multiple curves to obtain the flow resistance characteristics of the outer duct of the ring segment at the first axial position; repeat this process, and then cyclically process the remaining M-1 outer duct segments according to the same method to obtain the converted flow-relative resistance loss curves of the remaining outer duct segments.

8. The simplified calculation method of the flow resistance of the aero-engine duct as claimed in claim 1, characterized in that: The specific method for obtaining the loss correlation of the converted flow-relative resistance loss curve of each outer ring segment is as follows: fitting the converted flow-relative resistance loss curve of each outer ring segment to obtain the converted flow-relative resistance loss correlation of each outer ring segment; the maximum deviation between the fitted loss correlation and the original data point is not less than 3%; the resistance loss correlation of the first outer ring segment is △Pr=f1(Gh), and the resistance loss correlation of the Mth outer ring segment is △Pr=f M (Gh).

9. The simplified calculation method of the flow resistance of the aero-engine duct as claimed in claim 1, characterized in that: The specific method for obtaining the complete external conversion flow-relative resistance loss correlation formula is: Starting from the windward side of the culvert, the converted flow-relative resistance loss correlation equations of the first and second culvert segments are superimposed. The total converted flow-relative resistance loss correlation equation of the first two culvert segments is △Pr=F 1～2 (Gh)=f1(Gh)+(1-f1(Gh))×f2(Gh); The converted flow-relative resistance loss correlation equations of the first three outer circumference ring sections are superimposed, and the total converted flow-relative resistance loss correlation equation of the first three outer circumference ring sections is △Pr=F 1～3 (Gh)=F 1～2 (Gh)+(1-F 1～2 (Gh))×f3(Gh); By analogy, the total converted flow-relative resistance loss relationship of the first M outer circumference ring sections is △Pr=F M (Gh)=F 1～M-1 (Gh)+(1-F 1～M-1 (Gh))×f M (Gh), that is, to obtain the complete external conversion flow-relative resistance loss correlation formula △Pr=F M (Gh).

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