Numerical simulation aerodynamic force and torque correction method for ducted fan powered aircraft

Abstract

The invention belongs to the technical field of aircraft design, and particularly relates to a ducted fan power aircraft numerical simulation aerodynamic force and torque correction method. The correction method comprises the following steps: carrying out a ducted fan ground test; converting the ground test data to the sea level; determining a flow boundary condition of the numerical simulation working condition, and converting the numerical simulation working condition to a sea level reference point; performing interpolation to obtain a sea level fan disc thrust coefficient, and converting the sea level fan disc thrust coefficient into a numerical simulation working condition; carrying out numerical simulation aerodynamic force data correction; and carrying out numerical simulation aerodynamic torque data correction. According to the numerical simulation aerodynamic force and torque correction method for the ducted fan power aircraft, the lift force, the resistance and the pitching torque of the ducted fan power aircraft under the low-speed incoming flow condition are corrected on the basis of the fan disc thrust in combination with calculation and testing; the aerodynamic performance of the ducted fan power aircraft under different power working conditions can be evaluated efficiently and precisely, and the method has engineering practical value.

Description

Technical Field

[0001] The present invention belongs to the technical field of aircraft design, and particularly relates to a method for correcting aerodynamic forces and moments in numerical simulation of a ducted fan powered aircraft. Background Technique

[0002] The numerical simulation of the internal and external flow coupling of a ducted fan powered aircraft is a major technical difficulty in the design of ducted fan powered aircraft. According to the differences in computational workload and fidelity, the numerical simulation methods for internal and external flow coupling mainly include the inlet and exhaust boundary method, the body force method, the space-time fitting method, and the full-annulus unsteady Reynolds-averaged Navier-Stokes method (hereinafter referred to as the full-annulus URANS method). The inlet and exhaust boundary method is the simplest, and usually uses pressure inlet and outlet boundaries or flow rate inlet and outlet boundaries to replace the inlet and outlet of the fan disk. However, the inlet and exhaust boundary method cannot simulate the thrust generated by the fan disk. The body force method is a momentum source method, which uses a body force model to replace the functions of the blades such as pressurizing and rotating the flow field. The computational workload is reduced by more than two orders of magnitude compared with the full-annulus URANS method. However, it is difficult to accurately simulate the non-linear characteristics using the body force method, and the problems of computational convergence and stability are prominent. The space-time fitting method regards time and space as a unified four-dimensional continuum (three-dimensional space + time), and directly solves the governing equations in the space-time domain by constructing a space-time discretization format. The space-time fitting method can efficiently handle unsteady flows, and the computational workload is reduced by more than one order of magnitude compared with the full-annulus URANS method. However, the computational workload of the space-time fitting method is still more than 20 times that of the inlet and exhaust boundary method, and it is difficult to implement and cannot be compatible with mainstream CFD software such as Fluent and OpenFOAM. The full-annulus URANS method performs full-annulus solid modeling of the three-dimensional blades of the fan and uses the unsteady Reynolds-averaged Navier-Stokes method for simulation. Theoretically speaking, among the above several methods, the full-annulus URANS method has the highest accuracy, but also the largest computational workload, and can only meet the computational requirements of a few working conditions and cannot meet the computational requirements of large-scale working conditions.

[0003] Currently, there is an urgent need to develop a method for correcting aerodynamic forces and moments in numerical simulation of a ducted fan powered aircraft, which is used to efficiently and accurately evaluate the aerodynamic performance of a ducted fan powered aircraft under different power conditions. Summary of the Invention

[0004] One technical problem to be solved by the present invention is to provide a method for correcting aerodynamic forces and moments in numerical simulation of a ducted fan powered aircraft.

[0005] The method for correcting aerodynamic forces and moments in numerical simulation of the ducted fan powered aircraft of the present invention includes the following steps: S10. Conduct a ground test of the ducted fan; The wing trailing edge of the ducted fan-powered aircraft is arranged with a ducted fan group symmetrically distributed left and right. The ducted fan group includes several juxtaposed ducted fans; conduct ground tests on the ducted fans. The test model is a single ducted fan. A DC power supply is used to supply power to the ducted fan. A five-hole probe is used to measure the total pressure and static pressure of the inlet section and outlet section of the ducted fan, and the velocity and flow rate of the inlet section and outlet section are calculated; Calculate the ground test fan disk thrust of the ducted fan through formula (1) : ; Among them, is the ground test flow rate of the ducted fan; and are the inlet velocity and outlet velocity of the ducted fan respectively; and are the inlet pressure and outlet pressure of the ducted fan respectively, is the far-field pressure; and are the inlet area and outlet area of the ducted fan respectively; S20. Convert the ground test data to sea level; Calculate the converted flow rate and the converted fan disk thrust corresponding to the sea level reference point of the ground test data: ; Among them, and are the total temperature and total pressure of the ground test condition respectively; , are the total temperature and total pressure of the sea level reference point respectively; S30. Determine the flow boundary condition of the numerical simulation condition and convert the numerical simulation condition to the sea level reference point; Determine the ducted fan flow rate of the numerical simulation condition and the total incoming flow temperature and the total incoming flow pressure of the numerical simulation condition, and calculate the converted flow rate corresponding to the sea level reference point of the numerical simulation condition; ; S40. Interpolate to obtain the sea level fan disk thrust coefficient and convert the sea level fan disk thrust coefficient to the numerical simulation condition; Through data fitting, establish the converted flow rate corresponding to the sea level reference point of the ground test data obtained in step S20 The relationship between; the converted flow rate of the sea-level reference point corresponding to the numerical simulation working condition obtained in step S30 , interpolate to obtain the converted fan disk thrust of the sea-level reference point , and continue to convert it to the fan disk thrust corresponding to the numerical simulation working condition ; ; S50. Perform numerical simulation aerodynamic data correction; Use the fan disk thrust corresponding to the numerical simulation working condition obtained in step S40 to correct the aerodynamic data calculated by the numerical simulation: ; Among them, , and are the drag coefficient, lift coefficient, and side force coefficient respectively obtained from the numerical simulation calculation. During the numerical simulation process, the flow outlet boundary corresponds to the inlet boundary of the ducted fan, and the flow inlet boundary corresponds to the outlet boundary of the ducted fan. The flow rate is that in step S30 ; , and are the drag coefficient, lift coefficient, and side force coefficient after correction respectively; is the number of ducted fan disks, is the acceleration due to gravity, is the dynamic pressure, is the angle between the ducted fan thrust line and the fuselage axis, that is, the ducted fan installation angle, is the reference area; is the angle of attack of the ducted fan-powered aircraft, is the sideslip angle of the ducted fan-powered aircraft; S60. Perform numerical simulation aerodynamic moment data correction; The power of the ducted fan groups on both sides of the wing of the ducted fan-powered aircraft is the same. The fan disk thrust has no effect on the yaw moment and roll moment and does not need to be corrected; the pitch moment coefficient is corrected as follows: ; Among them, is the pitch moment coefficient obtained from the numerical simulation calculation, is the pitch moment coefficient after correction, is the acting arm length of the fan disk thrust, is the mean aerodynamic chord length of the ducted fan-powered aircraft.

[0006] The numerical simulation aerodynamic force and torque correction method for ducted fan powered aircraft of the present invention is based on the fan disk thrust of the ducted fan ground test. The aerodynamic data obtained by the intake and exhaust boundary numerical simulation method is corrected and verified by comparing with wind tunnel test data. The results show that this method can efficiently and accurately evaluate the aerodynamic performance of ducted fan powered aircraft under different power conditions, and has practical engineering value. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 The shape of a ducted fan powered aircraft according to an embodiment; Figure 2 The ducted fan of the embodiment is shown in FIG. Figure 3 Boundary conditions for numerical calculation of the inlet and outlet of the ducted fan of the embodiment; Figure 4a This is a comparison curve of the calculated and experimental lift coefficients obtained in the embodiment (flow rate 0.8852 kg / s); Figure 4b This is a comparison curve of the calculated and experimental lift coefficients obtained in the embodiment (flow rate 0.6644 kg / s); Figure 5a This is a comparison curve of the calculated and experimental resistance coefficients obtained in the embodiment (flow rate 0.8852 kg / s); Figure 5b This is a comparison curve of the calculated and experimental resistance coefficients obtained in the embodiment (flow rate 0.6644 kg / s); Figure 6a A comparison curve of the calculated and experimental pitching moment coefficients obtained in the embodiment (flow rate 0.8852 kg / s); Figure 6b This is a comparison curve of the calculated and experimental pitching moment coefficients obtained in the embodiment (flow rate 0.6644 kg / s).

[0008] In the figure, 1. Ducted fan; 101. Rotor; 102. Lip; 103. Stator; 104. Fairing; 105. Casing; C L : lift coefficient; C D : drag coefficient; C m : pitch moment coefficient; Angle: angle of attack of ducted fan powered aircraft . DETAILED DESCRIPTION

[0009] The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0010] Example: The ducted fan powered aircraft of this embodiment is shown in FIG. Figure 1, ducted fans are symmetrically arranged on the trailing edge of the wing of a ducted fan-powered aircraft. The ducted fan group includes several ducted fans arranged in parallel. Taking ducted fan 1 as an example, the structure of ducted fan 1 is shown in Figure 2 . Ducted fan 1 consists of a rotor 101, a lip 102, a stator 103, a fairing 104, and a casing 105. The inner diameter of the casing 105 of ducted fan 1 is 105 mm.

[0011] The ground test data of ducted fan 1 is shown in Table 1. The total pressure and static pressure at the inlet and outlet sections are measured by a five-hole probe. The inlet velocity and outlet velocity can be calculated through the total pressure and static pressure at the inlet and outlet sections, and then the ground test flow rate of ducted fan 1 can be calculated. When calculating the ground test flow rate of ducted fan 1 , the influence of the boundary layer is not considered. According to formula (1), the fan disk thrust under different ground test conditions can be calculated . The total temperature of this ground test condition is 288 K, and the total pressure is 93661 Pa. The ground test flow rate of ducted fan 1 and the fan disk thrust are converted to the sea-level reference point through formula (2) and formula (3). Through the data fitting method, the relationship between the converted fan disk thrust at the sea-level reference point of ducted fan 1 and the converted flow rate is established.

[0012] Table 1 Ground test data of ducted fan

[0013] There are two ducted fan flow rates in the numerical simulation conditions of ducted fan 1 in this embodiment , which are 0.5679 kg / s and 0.4263 kg / s respectively. The total temperature is 262.66 K, the total pressure is 62068 Pa, and the incoming flow velocity is 33 m / s. The above two ducted fan flow rates The converted flow rates at the sea-level reference point calculated through formula (4) are 0.8852 kg / s and 0.6644 kg / s respectively. The sea-level fan disk thrusts in the numerical simulation conditions are interpolated to be 3.17 kg and 1.67 kg respectively. The fan disk thrusts corresponding to the numerical simulation conditions are converted through formula (5) to be 1.94 kg and 1.02 kg respectively. These are the single ducted fan disk thrusts for subsequent correction.

[0014] Adopt as Figure 3Numerical simulation of the aerodynamic performance of a ducted fan powered aircraft is carried out on the shown flow inlet boundary and flow outlet boundary. Taking ducted fan 1 as an example, the inlet of ducted fan 1 is set as the flow outlet boundary, and the outlet of ducted fan 1 is set as the flow inlet boundary. The boundary conditions of the remaining ducted fans are set the same as those of ducted fan 1. After obtaining the aerodynamic data from the numerical simulation, the lift, drag and pitching moment of the ducted fan powered aircraft are corrected using formula (6) and formula (9) respectively to obtain the comparison curve between the wind tunnel test and the calculation results. As Figure 4a , Figure 4b shown, the influence of the fan disk thrust on the lift is small; as Figure 5a , Figure 5b shown, the influence of the fan disk thrust on the drag is obvious; as Figure 6a , Figure 6b shown, the influence of the fan disk thrust on the pitching moment is also obvious. Compared with the uncorrected forces and moments, the corrected data are in better agreement with the wind tunnel test results. Since flow separation occurs in the ducted fan powered aircraft at large angle of attack, resulting in a large error in the calculation results, the error between the corrected data and the test is also large. In addition, generally, the power of the ducted fan groups on both sides of the wing of the ducted fan powered aircraft is the same. Therefore, the fan disk thrust has no influence on the yaw moment and roll moment and does not need to be corrected; at the same time, in this embodiment, the sideslip angle is not considered, so the side force does not need to be corrected either.

[0015] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and embodiments. For those skilled in the art, without departing from the principle of the present invention, all the features disclosed in the present invention, or all the steps in the disclosed methods or processes, except for the mutually exclusive features and / or steps, can be combined in any way. The present invention is not limited to the specific details and the illustrated examples here.

Claims

1. Numerical simulation aerodynamic force and moment correction method for ducted fan powered aircraft, characterized in that, Including the following steps: S10. Conduct ground tests on the ducted fan; S20. Convert the ground test data to sea level; S30. Determine the flow boundary conditions for the numerical simulation conditions and convert the numerical simulation conditions to the sea level reference point; S40. Interpolate to obtain the sea level fan disk thrust coefficient and convert the sea level fan disk thrust coefficient to the numerical simulation conditions; S50. Correct the numerical simulation aerodynamic force data; S60. Correct the numerical simulation aerodynamic moment data.

2. The numerical simulation aerodynamic force and moment correction method for a ducted fan powered aircraft according to claim 1, characterized in that The conduct of the ground tests on the ducted fan in S10 includes the following: Ducted fan groups symmetrically distributed left and right are arranged at the trailing edge of the wing of the ducted fan powered aircraft. The ducted fan group includes a number of juxtaposed ducted fans. Conduct ground tests on the ducted fan. The test model is a single ducted fan. The ducted fan is powered by a DC power supply. A five-hole probe is used to measure the total pressure and static pressure of the inlet section and the outlet section of the ducted fan, and the velocity and flow rate of the inlet section and the outlet section are calculated; Calculate the ground test fan disk thrust of the ducted fan through formula (1). : ； Among them, is the ground test flow rate of the ducted fan; and are the inlet velocity and outlet velocity of the ducted fan respectively; and are the inlet pressure and outlet pressure of the ducted fan respectively, is the far-field pressure; and are the inlet area and outlet area of the ducted fan respectively.

3. The numerical simulation aerodynamic force and moment correction method for a ducted fan powered aircraft according to claim 2, characterized in that, The conversion of the ground test data to sea level in S20 includes the following: Calculate the converted flow rate at the sea-level reference point corresponding to the ground test data and the converted fan disk thrust : ； Wherein, and are the total temperature and total pressure of the ground test condition respectively; , are the total temperature and total pressure of the sea level reference point respectively.

4. The method for correcting aerodynamic force and moment in numerical simulation of a ducted fan-powered aircraft according to claim 3, wherein The determination of the flow boundary conditions for the numerical simulation conditions and the conversion of the numerical simulation conditions to the sea level reference point in S30 include the following: Determine the ducted fan flow rate of the numerical simulation condition and the total inlet temperature and total inlet pressure of the numerical simulation condition, and calculate the converted flow rate at the sea-level reference point corresponding to the numerical simulation condition ; 。 5. The numerical simulation aerodynamic force and moment correction method for a ducted fan powered aircraft according to claim 4, characterized in that The interpolation to obtain the sea level fan disk thrust coefficient and the conversion of the sea level fan disk thrust coefficient to the numerical simulation conditions in S40 include the following: Through data fitting, establish the conversion flow rate of the sea-level reference point corresponding to the ground test data obtained in step S20 and the converted fan disk thrust ; according to the conversion flow rate of the sea-level reference point corresponding to the numerical simulation condition obtained in step S30 , interpolate to obtain the converted fan disk thrust of the sea-level reference point , and continue to convert it to the fan disk thrust corresponding to the numerical simulation condition ; 。 6. The numerical simulation aerodynamic force and moment correction method for a ducted fan powered aircraft according to claim 5, characterized in that The correction of the numerical simulation aerodynamic force data in S50 includes the following: The fan disk thrust corresponding to the numerical simulation condition obtained by adopting Step S40 Correct the aerodynamic force data obtained from the numerical simulation calculation: ； Among them, , and are the drag coefficient, lift coefficient and side force coefficient obtained from numerical simulation calculations respectively. During the numerical simulation process, the flow outlet boundary corresponds to the inlet boundary of the ducted fan, and the flow inlet boundary corresponds to the outlet boundary of the ducted fan. The flow rate is in step S30; , and are the drag coefficient, lift coefficient and side force coefficient after correction respectively; is the number of ducted fan disks, is the acceleration due to gravity, is the dynamic pressure, is the angle between the thrust line of the ducted fan and the fuselage axis, that is, the installation angle of the ducted fan, is the reference area; is the angle of attack of the ducted fan powered aircraft, is the sideslip angle of the ducted fan powered aircraft.

7. The numerical simulation aerodynamic force and moment correction method for a ducted fan powered aircraft according to claim 6, characterized in that, The correction of the numerical simulation aerodynamic moment data in S60 includes the following: The power of the ducted fan groups on both sides of the wing of the ducted fan powered aircraft is the same. The fan disk thrust has no effect on the yaw moment and roll moment and does not need to be corrected. The pitch moment coefficient is corrected as follows: ； Among them, is the pitching moment coefficient obtained from numerical simulation calculations, is the pitching moment coefficient after correction, is the acting arm length of the fan disk thrust, is the mean aerodynamic chord length of the ducted fan powered aircraft.

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