Disclosure of Invention
In order to solve at least one of the above technical problems, the present application provides a method for designing distributed flight loads of a leading edge flap of a civil aircraft.
The application discloses a method for designing distributed flight loads of leading edge flaps of civil aircrafts, which comprises the following steps:
step one, determining a calculation state of the severe flight load of a leading edge flap;
secondly, performing full-aircraft flight load calculation without considering the influence of structural elastic deformation based on the nonlinear pneumatic pressure distribution data to obtain a full-aircraft flight load calculation result;
setting a typical monitoring profile on the airplane wing, and calculating structural deformation;
reconstructing the three-dimensional shape of the airplane to obtain the deformed three-dimensional shape;
fifthly, performing fluid mechanics calculation on the deformed three-dimensional shape, and extracting a fluid mechanics calculation result of the leading edge flap part;
and step six, according to the severe flight load calculation state of the leading edge flap in the step one, multiplying the hydrodynamics calculation result of the leading edge flap part in the step five by the velocity pressure to obtain the final civil aircraft leading edge flap distributed flight load.
According to at least one embodiment of the application, in the first step, the flight load change rule of the leading edge flap is combed according to the use limit of the airplane and the leading edge flap and the full airplane flight load calculation state, so that the severe flight load calculation state of the leading edge flap is determined.
According to at least one embodiment of the present application, in the second step, the method further includes:
and selecting nonlinear pneumatic pressure distribution data required by calculation according to the severe flight load calculation state.
According to at least one embodiment of the present application, the third step includes:
setting a typical monitoring section on the airplane wing, performing static loading analysis based on a structural finite element model by using the calculation result of the full airplane flight load, and calculating the structural deformation so as to obtain the deformation condition of the monitoring section.
According to at least one embodiment of the application, the structural finite element model is constrained at the center of gravity, and the size and shape of the fuselage frame section and the size and shape of each airfoil profile remain unchanged under the structural finite element model under load.
According to at least one embodiment of the present application, in the fourth step, the three-dimensional shape of the airplane is reconstructed by using a least square method according to the deformation condition at the typical monitoring section.
According to at least one embodiment of the present application, in the fifth step, a computational fluid dynamics model is created from the three-dimensional shapes before and after the deformation, and fluid dynamics calculation is performed.
According to at least one embodiment of the present application, the nonlinear aerodynamic pressure distribution data is pressure measurement wind tunnel test data, wherein a grid closest to a position of a pressure measurement point is selected from the computational fluid dynamics model to obtain an increment of the computational fluid dynamics data before and after deformation.
According to at least one embodiment of the present application, between the step five and the step six, the method further comprises:
and correcting the fluid mechanics calculation result of the leading edge flap part in the flight envelope range of the airplane.
The application has at least the following beneficial technical effects:
according to the method for designing the distributed flight loads of the civil aircraft leading edge flaps, the influence of the elastic deformation of the structure on the flight loads is considered, so that the accuracy of the distributed flight load design of the civil aircraft leading edge flaps is effectively improved, the weight of the aircraft is reduced, and a new idea is provided for the distributed flight load design of the civil aircraft leading edge flaps.
Detailed Description
In order to make the implementation objects, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described in more detail below with reference to the drawings in the embodiments of the present application. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described are some, but not all embodiments of the disclosure. The embodiments described below with reference to the drawings are exemplary and intended to be used for explaining the present application and should not be construed as limiting the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application. Embodiments of the present application will be described in detail below with reference to the accompanying drawings.
In order to realize the accuracy of the civil aircraft leading edge flap distributed flight load design, the application provides a correction principle of aerodynamic pressure distribution data before structure elastic deformation, and the corrected aerodynamic pressure distribution data is used for calculating the civil aircraft leading edge flap distributed flight load.
The method for designing distributed flight loads of leading-edge flaps of civil aircraft according to the present application is described in further detail below with reference to fig. 1 to 6.
The application discloses a method for designing distributed flight loads of leading edge flaps of civil aircrafts, which comprises the following steps:
and step S101, determining the calculation state of the severe flight load of the leading edge flap.
Specifically, because structural strength design usually only requires the use of severe flight loads, the calculation state of the severe flight loads of the leading edge flaps needs to be screened and determined according to the use limit of the aircraft and the leading edge flaps, in combination with the calculation state of the full aircraft flight loads, and the change rule of the flight loads of the leading edge flaps.
And S102, performing full-aircraft flight load calculation without considering the influence of structural elastic deformation based on the nonlinear aerodynamic pressure distribution data to obtain a full-aircraft flight load calculation result.
Specifically, according to the severe flight load calculation state, nonlinear pneumatic pressure distribution data required by calculation are selected, and full-aircraft flight load calculation without considering the influence of elastic deformation of the structure is carried out on the basis of the nonlinear pneumatic pressure distribution data, so that a full-aircraft flight load calculation result is obtained.
And S103, setting a typical monitoring profile on the airplane wing, and calculating structural deformation.
Specifically, a typical monitoring section is arranged on an airplane wing, a full-airplane flight load calculation result is used, static force loading analysis is carried out on the basis of a structure finite element model, and structural deformation is calculated to obtain the deformation condition of the monitoring section. At the moment, the structural finite element model needs to be restrained at the gravity center, and the size and the shape of the section of the frame of the machine body and the size and the shape of each airfoil profile of the structural finite element model are kept unchanged under the loaded condition.
And S104, reconstructing the three-dimensional shape of the airplane to obtain the deformed three-dimensional shape.
Specifically, according to the deformation condition of a typical monitoring section, the three-dimensional shape of the airplane is reconstructed by using a least square method, and the deformed three-dimensional shape is obtained.
And S105, performing fluid mechanics calculation on the deformed three-dimensional shape, and extracting a fluid mechanics calculation result of the leading edge flap part.
Specifically, a computational fluid dynamics model is established according to the three-dimensional shapes before and after deformation, fluid dynamics calculation is carried out, and a fluid dynamics calculation result is obtained. Because the grid density of the computational fluid dynamics model is far greater than the pressure measurement point density of the pressure measurement wind tunnel test data, if the pneumatic pressure distribution data is the pressure measurement wind tunnel test data, the grid closest to the position of the pressure measurement point is selected (in the computational fluid dynamics model) to obtain the increment of the computational fluid dynamics data before and after deformation.
In addition, step S105 may be followed by:
step S1051, in the range of the flight envelope of the airplane, correcting the pneumatic pressure distribution data related to the severe flight load calculation state of the leading edge flap. According to the conventional flight load design experience, if the flight load is calculated by directly using the linear aerodynamic pressure distribution data, the accuracy of the obtained flight load is not high compared with that obtained by using the nonlinear aerodynamic pressure distribution data. Thus, the present application uses nonlinear aerodynamic pressure profile data when calculating severe leading edge flap flight loads. If the nonlinear aerodynamic pressure distribution data are computational fluid mechanics data, establishing a computational fluid mechanics model according to the deformed three-dimensional shape of the airplane, and directly using the obtained computational fluid mechanics data as corrected aerodynamic pressure distribution data; if the nonlinear pneumatic pressure distribution data is pressure measuring wind tunnel test data, subtracting the fluid mechanics calculation results before and after deformation to obtain the increment of the fluid mechanics calculation data before and after deformation, and superposing the increment on the pressure measuring wind tunnel test data to be used as the corrected pneumatic pressure distribution data.
And S106, according to the severe flight load calculation state of the leading edge flap in the step one, multiplying the hydrodynamics calculation result of the leading edge flap part in the step five by the speed pressure to obtain the final distributed flight load of the leading edge flap of the civil aircraft.
Specifically, the modified aerodynamic pressure distribution data may be multiplied by the velocity pressure to obtain the leading edge flap distributed flight load. Distributed flight loads can be divided into chordwise and spanwise distributions. According to the position characteristics of the leading edge flap on the airplane, if the aerodynamic pressure distribution data is pressure measurement wind tunnel test data, the chord direction distribution load of the leading edge flap can be set as follows: on the pressure measurement section, the load of the front edge is the load of the pressure measurement point closest to the front edge, the load of the rear edge is the load of the pressure measurement point closest to the rear edge, and linear interpolation is carried out on the loads between the front edge and the pressure measurement point closest to the front edge, between the rear edge and the pressure measurement point closest to the rear edge and between the pressure measurement points; the spanwise distributed load of the leading edge flap can be set to: the distributed load of the leading edge flap side end surface close to the fuselage is the distributed load of the pressure measuring section closest to the end surface, the distributed load of the leading edge flap side end surface close to the wing tip is the distributed load of the pressure measuring section closest to the end surface, and the distributed loads between the leading edge flap side end surface close to the fuselage and the pressure measuring section closest to the end surface, between the leading edge flap side end surface close to the wing tip and the pressure measuring section closest to the end surface and between the pressure measuring sections are subjected to chord equal proportion linear interpolation. If the aerodynamic pressure distribution data are computational fluid dynamics data, the chord-wise and span-wise distribution loads of the leading edge flap are directly set to be the result of multiplying the aerodynamic pressure distribution data by the velocity pressure due to the fact that the grid density of the computational fluid dynamics model is large enough.
In conclusion, the aerodynamic pressure distribution data are corrected by considering the elastic deformation of the loaded actual structure, and the corrected aerodynamic pressure distribution data are used for calculating the distributed flight load of the leading edge flap of the airplane; the accuracy of the distributed flying load design of the leading edge flap of the civil aircraft is effectively improved, the weight of the aircraft is reduced, and a new idea is provided for the distributed flying load design of the leading edge flap of the civil aircraft.
The method for designing distributed flight loads of leading-edge flaps of civil aircraft according to the invention is further described in the following by way of a specific example:
the example is a distributed flight load design of a leading edge flap of a civil aircraft, and the outline diagram of the civil aircraft is shown in figure 2. According to the civil aircraft leading edge flap distributed flight load design method provided by the invention, the civil aircraft leading edge flap distributed flight load design idea is as follows:
1) According to the use limitation of the airplane and the leading edge flap, combining the flight load calculation state of the whole airplane, combing the flight load change rule of the leading edge flap without considering the influence of the elastic deformation of the structure, screening and determining the severe flight load calculation state of the leading edge flap, wherein the calculation state is shown in table 1;
TABLE 1 leading edge flap Severe flight load calculation State
2) Selecting nonlinear pneumatic pressure distribution data required by calculation according to the calculation state table 1 in the step 1), and performing full-aircraft flight load calculation without considering the influence of structural elastic deformation based on the computational fluid mechanics data to obtain a full-aircraft flight load calculation result;
3) A typical monitoring profile is provided on an aircraft wing, and a schematic diagram of the monitoring profile layout is shown in FIG. 3. Using the calculation result of the full-aircraft flight load in the step 2), carrying out statics loading analysis based on a structural finite element model (a structural finite element model diagram is shown in figure 4), and obtaining the deformation condition of the typical monitoring section of the aircraft under the loading;
4) Reconstructing the three-dimensional shape of the airplane by using a least square method according to the deformation condition at the typical monitoring section, wherein the three-dimensional shape before deformation and the three-dimensional shape after deformation are opposite to each other, and the three-dimensional shape is shown in figure 5;
5) Establishing a computational fluid dynamics model (as shown in figure 6) according to the deformed three-dimensional shape, performing fluid dynamics calculation to obtain a fluid dynamics calculation result, and taking out a leading edge flap part in the calculation result;
6) And (3) multiplying the hydrodynamics calculation result of the leading edge flap part in the step 5) by the speed and pressure according to the calculation state table 1 in the step 1) to obtain the final distributed flight load of the leading edge flap of the civil aircraft.
The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present application should be covered within the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.