Rotor wing and wing aerodynamic interference calculation method for tilt-rotor aircraft

Abstract

The invention provides a rotor wing and wing aerodynamic interference calculation method for a tilt-rotor aircraft, which comprises the following steps: firstly, establishing a body coordinate system and a propeller hub coordinate system, calculating to obtain a coordinate transformation matrix between the propeller hub coordinate system and the body coordinate system, stipulating a simplified hypothesis of a model, and then obtaining a rotor wing circumferential induced velocity at a wing position; the specific area and position of an overlapping area, namely an interference area, of a wake ellipse and a wing rectangle are calculated according to a system flow, then the wing is divided into a slip flow area influenced by rotor interference and a free flow area not influenced, the total aerodynamic force of the whole wing is obtained, and finally the total aerodynamic force of the whole wing is calculated by calculating the total aerodynamic force of the whole wing in a forward flight state and a side flight state of the sample aircraft. And verifying the rationality of interference region calculation according to the position and area of the wing interference region under the conditions of different speeds and tilting angles. According to the method, the complex aerodynamic interference between the rotor and the wing in the tilting transition process of the tilt-rotor aircraft can be effectively determined, and the calculation precision of the aerodynamic force of the wing is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of helicopter flight mechanics and control, in particular to a method for calculating aerodynamic interference between a rotor and a wing of a tiltrotor aircraft. Background Art

[0002] Tilt-rotors combine the advantages of helicopters and fixed-wing aircraft. They can hover and cruise at high speeds. However, this also significantly increases the aircraft's complexity, one of which is the aerodynamic interference of the rotors on the wings.

[0003] The aerodynamic interference of a tiltrotor's rotor on the wing is caused by the interaction between the rotor wake and the wing. During the rotor's tilting motion, it generates not only an induced velocity perpendicular to the disc plane and along the rotor axis, but also a circumferential induced velocity parallel to the disc plane and in the same direction as the rotor's rotation. These two induced velocities combine to create aerodynamic interference on the wing.

[0004] When the tilt-rotor aircraft is in helicopter mode, the rotor disc plane is almost parallel to the wing plane, and the rotor axial induced velocity is perpendicular to the wing surface, which directly changes the angle of attack distribution of the wing surface and thus changes the wing aerodynamic force. The circumferential induced velocity is parallel to the wing surface and has almost zero effect on the wing angle of attack. Therefore, in helicopter mode, the rotor axial induced velocity is the main cause of rotor / wing aerodynamic interference. When the engine nacelle is tilted forward, such as Figure 1 As shown in the figure, the angle between the rotor's axial induced velocity and the wing surface gradually decreases, while the angle between the circumferential induced velocity and the wing surface gradually increases. When the nacelle tilt angle reaches 90°, the direction of the rotor's axial induced velocity becomes parallel to the wing, making it almost impossible to change the wing's angle of attack. However, at this point, the rotor's circumferential induced velocity is almost perpendicular to the wing surface, significantly changing the wing's angle of attack distribution. Therefore, the role of the rotor's circumferential induced velocity gradually increases in transition mode. When in fixed-wing mode, the rotor's circumferential induced velocity becomes the primary cause of rotor / wing aerodynamic interference.

[0005] A large number of scholars have carried out a lot of research on the interference problem in the process of tilting. Huang Q, He G, Jia J, et al. Numerical simulation on aerodynamic characteristics of transition section of tilt-wing aircraft[J]. Aerospace, 2024, 11(4): 283. adopts CFD method combined with moving mesh to systematically simulate the aerodynamic effect in the process of tilting, and deeply discusses the difference between steady-state and non-steady-state calculation. Yang Yifan, Wang Xiao. Aerodynamic interference research of tilt-rotor aircraft rotor / wing based on improved hybrid vortex particle method[J / OL]. This paper puts forward an improved hybrid vortex particle method, analyzes the flow field change in the process of tilt-rotor aircraft conversion, and discusses the influence of rotor / wing interference on the overall performance of rotor / wing model. However, although the above method can accurately calculate the aerodynamic force of rotor or wing, it can well simulate the aerodynamic interference between rotor and wing, but it needs a large amount of calculation resources, the calculation efficiency is low, and it is difficult to adapt to the demand for rapid prediction and dynamic response in flight mechanics analysis.

[0006] In contrast, the mechanism-based model method can better meet the real-time requirements of flight mechanics analysis. By deeply analyzing the aerodynamic interference mechanism between the rotor and the wing, the mechanism model can simplify the complex flow field calculation process while retaining the key factors affecting the performance of the aircraft. Ferguson, Samuel W. "Development and validation of a simulation for a generic tilt-rotor aircraft." NASA CR 166537 (1989). The blade element theory and vortex method are used to establish a thrust propeller / airfoil aerodynamic interference model, and the rotor wake is simulated by a longitudinal and transverse distributed vortex lattice. The induced velocity of the rotor on the control points of the wing surface is calculated by the Boit-Savart theorem. Bohari B, Borlon Q, Bronz M, et al. Aerodynamic model of propeller–wing interaction for distributed propeller aircraft concept[J]. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, 2020, 234(10): 1688-1705. In the calculation of the rotor-wing downward load of the XV-15 tilt-rotor aircraft, the linear superposition method is used to divide the wing into slipstream and free flow areas for calculation, but it relies on empirical coefficients, limiting its universality. Zhang Z, Chen R. "Tilt-rotor aircraft rotor / airfoil aerodynamic interference theory and experiment." Acta Aeronautica et Astronautica 38.3 (2017): 26-34. The position and area of the interference region are determined by theoretical calculation, and the wing load increment and average angle of attack increment caused by interference are introduced to define the velocity range of interference, but its research does not involve the influence of the circumferential induced velocity of the rotor wake on the wing in the fixed-wing mode. SUMMARY

[0007] The present application provides a rotor and wing aerodynamic interference calculation method for a tilt-rotor aircraft, which can effectively determine the complex aerodynamic interference between the rotor and the wing of the tilt-rotor aircraft during the tilt transition process, and improve the calculation accuracy of the wing aerodynamic force.

[0008] The present application provides a rotor and wing aerodynamic interference calculation method for a tilt-rotor aircraft, which includes the following steps:

[0009] 1) Establish the body coordinate system and the hub coordinate system, calculate the coordinate transformation matrix between the hub coordinate system and the body coordinate system, specify the simplified assumptions of the model, and realize the unified processing of the data in the rotor and wing interference model;

[0010] 2) A rotor model is established using blade element theory and a dynamic inflow model. Based on this, the axial induced velocity generated by the rotor at the wing is obtained. The circumferential induced velocity at the corresponding point of the rotor disc is calculated based on the angular momentum theorem and the rotational kinetic energy theorem, thereby obtaining the rotor circumferential induced velocity at the wing.

[0011] 3) Based on the assumptions and simplified model, the shape and position parameters of the rotor wake, i.e., the projection of the wake ellipse onto the plane of the wing, are calculated. On this basis, the specific area and position of the overlapping area between the wake ellipse and the wing rectangle, i.e., the interference area, are calculated according to the system process.

[0012] 4) Divide the wing into a slipstream region affected by the rotor interference and an unaffected freestream region. Calculate the aerodynamic forces in these two regions separately, and then superimpose the aerodynamic forces of the two parts to obtain the total aerodynamic force of the entire wing.

[0013] 5) Calculate the position and area of ​​the wing interference region for the sample aircraft in forward and side flight at different speeds and tilt angles, and draw corresponding schematic diagrams to verify the rationality of the interference region calculation. At the same time, based on the aerodynamic interference relationship between the rotor and wing of the tiltrotor aircraft obtained in the above steps, further solve the aerodynamic force of the wing under the rotor and wing combination without considering interference, and compare and analyze the difference in aerodynamic performance with and without considering interference to verify the rationality and accuracy of the interference aerodynamic force calculation.

[0014] Further improvement, step 1) the specific construction method of the body coordinate system and the hub coordinate system is: the origin of the body coordinate system is located at the center of mass C of the whole machine, the X axis is in the longitudinal symmetry plane of the whole machine, pointing to the nose, the Y axis is perpendicular to the longitudinal symmetry plane, pointing to the right, the Z axis is in the longitudinal symmetry plane, and its direction is determined by the right-hand rule; the origin of the hub coordinate system is located at the hub center H, its X axis points from 0° to 180° at an azimuth angle, the axis points from 270° of the right-hand rotor to 90°, the axis is perpendicular to the propeller disc plane, parallel to the engine nacelle, and its direction is determined by the right-hand rule. The coordinate conversion matrix T between the hub coordinate system and the body coordinate system Bs for:

[0015]

[0016] In the formula, β N is the nacelle tilt angle, β N =0° represents helicopter mode, β N =90° represents fixed-wing mode.

[0017] Further improvement, the simplified assumptions of the model in step 1) are as follows:

[0018] 1.1) The wing is divided into two parts: the interference zone affected by the rotor wake and the free flow zone outside the wake. The aerodynamic force of the wing is equal to the sum of the aerodynamic forces in the interference zone and the free flow zone.

[0019] 1.2) The rotor is equivalent to a disc plane with a radius of R and a rotor trail radius of R Wk ;

[0020] 1.3) The airflow velocity in the area of ​​rotor interference with the wing can be considered as the superposition of the distant airflow velocity, the rotor axial induced velocity, and the circumferential induced velocity;

[0021] 1.4) The rotor wake as a whole rotates about the rotor axis at a certain angular velocity, which has no effect on the shape of the rotor wake;

[0022] 1.5) The average value of the aerodynamic angle of attack increment caused by the circumferential induced velocity in the rotor-wing interference region is the aerodynamic angle of attack increment at the centroid of the interference region.

[0023] Further improvement, the calculation process of the rotor circumferential induced velocity in step 2) is as follows:

[0024] 2.1) Calculation of rotor axial induced speed:

[0025] 2.11) According to the first-order harmonic Pitt-Peters dynamic inflow method, the distribution of dimensionless induced velocity on the rotor disc plane is obtained:

[0026]

[0027] Where: ν0,ν 1c ,ν 1s are the dimensionless term of rotor uniform inflow, the dimensionless term of first-order cosine inflow and the dimensionless term of first-order sine inflow, respectively. is the blade azimuth, is the spanwise position of the blade, dimensionless;

[0028] 2.12) When hovering, the radius of the rotor trail at the wing is R Wk Based on the rotor radius, the rotor thrust coefficient and the nacelle length are expressed as:

[0029]

[0030] in,

[0031]

[0032] 2.13) At the rotor disc plane, the air flow through the disc plane should be equal to the product of the average axial induced velocity at the disc and the disc area; assuming that the free stream velocity vector is V f , the average axial induced velocity vector at the rotor disc is v ik , then the air flow through the propeller disc plane is πR 2 |v ik +V f |, downstream of the impeller disc, the airflow is constantly accelerating, the wake radius is constantly shrinking, but the air flow rate should remain unchanged, that is, it satisfies the relationship as shown in formula (5), and the incoming flow velocity in the interference zone at the wing can be solved;

[0033] πR 2 |v ik +V f |=πR w 2 |v iWk +V f | (5)

[0034] In formula (5), v iWk is the average axial induced velocity vector of the rotor at the wing, R w is the rotor wake radius at that location;

[0035] 2.2) Calculation of rotor circumferential induced velocity:

[0036] 2.21) Calculate the moment of inertia of the air added to the wake by integrating the mass flow rate of the air passing through the propeller disc. For a radius of R w The uniform tail flow, the mass flow rate of the tail flow per unit time dm / dt = ρ|V|A, where is the wake cross-sectional area;

[0037] 2.21) By integrating the air loop passing through the propeller disk, we can obtain the moment of inertia rate per unit time added to the wake, i.e., dI z / dt, dI z It is understood as the cumulative moment of inertia, which is the following formula:

[0038]

[0039] Where ρ is the air density, |V| is the magnitude of the resultant velocity vector through the disc plane, including the free stream velocity V f and rotor axial induced velocity v ia , rotor trail radius R w Determined by formula (3);

[0040] 2.22) According to the law of angular momentum, the relationship between the air rotational angular velocity increment ΔΩ and the corresponding torque is as follows:

[0041] Mdt=I z ΔΩ(7)

[0042] Where M is the torque acting on the air, which is equal to the rotor counter-torque in magnitude and opposite in sign.

[0043] 2.23) Before the air at infinity passes through the rotor disc, it has no rotational motion and an angular velocity of Ω0 = 0. When it passes through the disc plane, it undergoes rotational motion around the rotor axis under the action of the rotor, and its angular velocity changes to Ω1. When the airflow moves far enough downstream of the rotor, its angular velocity accelerates further and changes to Ω2. Therefore, the above equation has

[0044] ΔΩ=Ω2-Ω0 (8)

[0045] Substituting into equations (6) and (7), we can obtain:

[0046]

[0047] 2.24) The work W done by the rotor torque on the airflow at the disc per unit time dt and the change in the air's rotational kinetic energy ΔP are expressed as follows:

[0048]

[0049] According to the kinetic energy theorem, the work done by the torque on the air should be equal to the change in the kinetic energy of the air, W = ΔP. Considering that Ω0 = 0, we can get:

[0050]

[0051] 2.25) Assume that the corresponding point of a certain infinitesimal element on the wing surface on the rotor disc is (r ψ), then the rotor circumferential induced velocity at this infinitesimal element in the Earth's axis system is:

[0052]

[0053] Where M is the torque acting on the air, which is equal to the rotor counter-torque and opposite in sign; |V| is the magnitude of the resultant velocity vector passing through the rotor disc plane, and R w is the rotor trail radius; Δ = 1 represents right rotation, Δ = -1 represents left rotation, T Bs is the coordinate transformation matrix between the hub coordinate system and the body axis system.

[0054] Further improvement, the calculation process of the interference area between the trail ellipse and the wing rectangle in step 3) is as follows:

[0055] 3.1) Assume X TEK ,X LEKThey represent the displacement of the trail center to the trailing edge and the leading edge of the wing in the X-axis direction, and both are positive in the positive direction of the X-axis; TIPK The displacement of the center of the trail in the lateral (Y-axis direction) direction (relative to the wing tip), with outward displacement being positive, and X TEK ,X LEK 、Y TIPK It is related to the position of the center of the trail of the projected ellipse and is calculated as:

[0056]

[0057] X LEk =c w +X TEk (14)

[0058]

[0059] 3.2) Assume R WXK ,R WYK is the radius of the trail ellipse in the X and Y directions before rotation, δ K R is the angle of rotation of the trail projection circle or ellipse around the trail center. In the case of left-side wind, the projection ellipse rotates counterclockwise, and in the case of right-side wind, it rotates clockwise. WXK ,R WYK , δ K is related to the shape of the projected ellipse, where

[0060]

[0061] 3.3) The above parameters are all calculated by geometric relationships to obtain analytical expressions. Based on the above parameters, the area of ​​the interference region and its centroid position can be calculated:

[0062] F1(C 1k ,C 2k ):

[0063]

[0064] F2(C 1k ,C 2k ):

[0065]

[0066] in,

[0067]

[0068] The interference area calculation process is actually based on the intersection position of the wake projection ellipse and the wing edge, and the calculation is performed from bottom to top and then superimposed to obtain the result. The F1 function is used to calculate the area of the irregular figure with two curved edges, and the F2 function is used to calculate the area of the irregular figure with one curved edge.

[0069] 3.4) The calculation process described above is the position of the wake center to the centroid of the interference area in the X-axis direction and the Y-axis direction, and the positive direction of the X-axis and the Y-axis is positive. By calculating the position of the wake center relative to the aerodynamic center of the wing and the position of the aerodynamic center of the wing relative to the center of gravity, the position of the centroid of the interference area relative to the center of gravity in the body axis system is obtained, and the calculation formula is as formula (22). As a simplification, the aerodynamic center of the wing is placed on the 1 / 4 chord line of the wing:

[0070]

[0071] Further improvement, the total aerodynamic force calculation method of the wing in step 4) is as follows:

[0072] 4.1) Aerodynamic force of the slipstream area:

[0073] According to the solution of the axial and circumferential induced velocity of the rotor model part, the axial induced velocity is uniformly distributed in the interference area, and the circumferential induced velocity is linearly distributed in the interference area. The circumferential induced velocity of the rotor wake projection in the plane of the wing is a function of the distance y (0≤y≤R w ) to the wing tip, and y=0 represents the wing tip. The circumferential induced velocity on the surface of the wing is represented as:

[0074]

[0075] According to the simplified assumption, the average circumferential induced velocity of the interference area is the circumferential induced velocity at the centroid, and the centroid position is:

[0076]

[0077] For the interference area The airflow velocity of the wing in the body axis system is:

[0078]

[0079] Therefore, the angle of attack and the sideslip angle of the wing slipstream area are respectively:

[0080]

[0081] The dynamic pressure of the wing slipstream area is:

[0082]

[0083] From this, we can obtain the lift, drag and pitching moment in the wind axis of the wing slipstream area:

[0084] L iWPk =q iWk S iWk C LWPk

[0085] D iWPk =q iWk S iWk C DWPk

[0086] M iWPk =q iWk S iWk c w C mWP (29);

[0087] 4.2) Aerodynamic forces in the free flow area:

[0088] The calculation process of the aerodynamic force of the wing in the free flow area that is not affected by the rotor wake is similar to that of the wing of a conventional aircraft. The wing area S in the free flow area is WFS is the total wing area S W and the slipstream wing area S iWk Difference:

[0089] S WFS =S W -(S iWR +S iWL ) (30)

[0090] The wing dynamic pressure qWFS in the free flow area is as shown in Equation (21), where b W is the lateral position of the aerodynamic center of the entire wing relative to the center of gravity;

[0091]

[0092] Then, the lift force L under the wind axis of the wing in the free flow area is WPF , resistance D WPF and pitching moment M WPF for:

[0093] L WPF =q WFS S WFS C LWP -q WFS S W C Lδa |δ a |

[0094] D WPF =q WFS S WFS CDWP

[0095] M WPF = q WFS S WFS c w C mWP . (32)

[0096] The present application has the beneficial effects that:

[0097] 1. The present application comprehensively considers the interference influence of the rotor circumferential induced velocity on the wing during the tilt transition process of the tilt-rotor aircraft. Compared with the traditional method considering only the axial induced velocity, the present application can more comprehensively reflect the real physical phenomenon, and the calculation result is closer to the actual situation, meets the engineering needs of real-time analysis of flight mechanics, and has significant engineering practical value.

[0098] 2. The present application can accurately calculate the area and position parameters of the rotor / wing interference region of the tilt-rotor aircraft in various flight states (such as forward flight, side flight, etc.). This method not only can quantify the specific range of the interference region, but also can provide reliable basis for qualitative analysis of flight state, and is helpful for optimizing the design and performance of the aircraft.

[0099] 3. The interference calculation method of the present application has good universality. In theory, this method is not only suitable for the rotor / wing combination of the tilt-rotor aircraft, but also can be extended to other types of rotor / wing combination aircraft (such as interference analysis of rotor on flat tail). The applicability of different configurations only needs to adjust the relative position parameters of the rotor and the wing, which shows strong adaptability and wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0100] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0101] Figure 1 is a schematic diagram of rotor wake and wing when the nacelle angle is large and the forward angle is large;

[0102] Figure 2 is a schematic diagram of the calculation coordinate system;

[0103] Figure 3 is a calculation diagram of the rotor aerodynamic model;

[0104] Figure 4 is a schematic diagram of the rotor circumferential induced velocity;

[0105] Figure 5The wing interference area and the aerodynamic center calculation flow chart;

[0106] Figure 6 The wing interference area and the aerodynamic center calculation flow chart;

[0107] Figure 7 The wing slipstream area changes with the forward flight speed in the helicopter mode;

[0108] Figure 8 The wing slipstream area changes with the forward flight speed in the short nacelle tilt angle 15° mode;

[0109] Figure 9 The wing slipstream area changes with the forward flight speed in the short nacelle tilt angle 30° mode;

[0110] Figure 10 The wing slipstream area changes with the side wind speed in the helicopter mode (V X = 0);

[0111] Figure 11 The wing slipstream area changes with the side wind speed in the helicopter mode (V X = 20 m / s);

[0112] Figure 12 The wing slipstream area changes with the side wind speed in the short nacelle tilt angle 15° (V X = 0);

[0113] Figure 13 The wing slipstream area changes with the side wind speed in the short nacelle tilt angle 15° (V X = 20 m / s);

[0114] Figure 14 The wing lift ratio changes in the helicopter mode in the trim state;

[0115] Figure 15 The wing aerodynamic interference increment changes in the transition mode;

[0116] Figure 16 The wing aerodynamic performance chart with or without the rotor aerodynamic interference. DETAILED DESCRIPTION

[0117] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0118] The application provides a rotor / airfoil aerodynamic interference calculation method for a tilt-rotor aircraft.

[0119] I. Coordinate system and basic assumptions

[0120] 1.1. Explanation of the calculation coordinate system

[0121] The application involves two right-hand coordinate systems, i.e. a body coordinate system and a hub coordinate system, as shown in the calculation coordinate diagram. Figure 2 The body coordinate system has its origin at the center of gravity C of the whole aircraft, the X axis is in the longitudinal symmetry plane of the whole aircraft and points to the nose, the Y axis is perpendicular to the longitudinal symmetry plane and points to the right, and the Z axis is in the longitudinal symmetry plane and its direction is determined according to the right-hand rule. The hub coordinate system has its origin at the center H of the hub, the X axis points from 0° to 180°, the Y axis points from 270° to 90° of the right-rotating rotor, and the Z axis is perpendicular to the rotor disc plane and parallel to the engine nacelle, and its direction is also determined according to the right-hand rule. The coordinate transformation matrix T between the hub coordinate system and the body coordinate system is: Bs

[0122]

[0123] In the formula, β N is the nacelle tilt angle, and in this document, β N = 0° represents the helicopter mode, and β N = 90° represents the fixed-wing mode.

[0124] 1.2. Basic assumptions

[0125] 1) The wing is divided into an interference region affected by the rotor wake and a free flow region outside the wake region, and the wing aerodynamic force is equal to the sum of the aerodynamic forces of the interference region and the free flow region

[10] ;

[0126] 2) The rotor is equivalent to a rotor disc plane, the radius of which is R, and the rotor wake radius is R Wk ;

[0127] 3) The air flow velocity in the interference region of the rotor and the wing can be regarded as the superposition of the far-field flow velocity, the axial induced velocity of the rotor and the circumferential induced velocity.

[0128] 4) The whole rotor wake rotates around the rotor axis at an angular velocity, and the angular velocity has no effect on the shape of the rotor wake.

[0129] 5) In the interference region of the rotor and the wing, the average value of the aerodynamic angle of attack increment caused by the circumferential induced velocity is the aerodynamic angle of attack increment at the center of the interference region.

[0130] II. Rotor model

[0131] ​The aerodynamic force of each blade is calculated by using blade element theory and then summed up to obtain the total aerodynamic force of the whole rotor. The induced velocity, rotor flapping motion and aerodynamic force are interrelated in the rotor model. The solution process is referenced to the flow chart of Figure 3 The axial induced velocity generated by the rotor is calculated by using dynamic inflow method. The circumferential induced velocity is derived based on angular momentum theorem and rotational kinetic energy theorem. The induced velocity at the wing is obtained.

[0132] 2.1 Calculation of the axial induced velocity of the rotor

[0133] According to the first-order harmonic Pitt-Peters dynamic inflow method, the distribution of the non-dimensional induced velocity in the rotor disc plane can be obtained as follows:

[0134]

[0135] wherein v0, v 1c and v 1s are the non-dimensional items of uniform inflow, first-order cosine inflow and first-order sine inflow respectively, is the azimuth angle of the blade, is the non-dimensional position of the blade spanwise.

[0136] At hover, the contraction radius R Wk of the rotor wake at the wing can be expressed as follows according to the rotor radius, rotor thrust coefficient and nacelle length:

[0137]

[0138] wherein,

[0139]

[0140] At the rotor disc plane, the air flow through the disc plane should be equal to the product of the average axial induced velocity at the disc and the disc area. Assuming that the free inflow velocity vector is V f and the average axial induced velocity vector at the rotor disc is v ik , the air flow through the disc plane is πR 2 |v ik + V f |. Downstream of the disc, the air flow is continuously accelerated and the wake zone radius is continuously reduced, but the air flow should remain unchanged, i.e. the relationship of formula (5) is satisfied, so as to solve the inflow velocity at the wing.

[0141] πR 2 |v ik + V f | = πR w 2 |v iWk + Vf | (5)

[0142] v iWk is the average axial induced velocity vector of the rotor at the wing, R w is the rotor wake radius at the wing.

[0143] 2.2 Calculation of the Circumferential Induced Velocity of the Rotor:

[0144] During the rotation of the rotor, the air around the rotor will generate a torque around the rotor axis to hinder the rotation of the rotor. According to Newton's third law, the rotor will also generate a torque of equal size and opposite direction to the air, so that the air around the rotor will generate a rotational motion around the rotor axis in the same direction as the rotation of the rotor, which generates the circumferential induced velocity of the rotor.

[0145] When calculating the rate of rotational inertia of the air added to the wake, the mass flow rate of the air passing through the rotor disk is integrated. For a uniform wake with a radius of R w , the mass flow rate added to the wake per unit time is dm / dt = p|V|A, where is the cross-sectional area of the wake. By integrating the air ring passing through the rotor disk, the rate of rotational inertia (i.e. dI z / dt) added to the wake per unit time can be obtained. dI z is understood as the cumulative rotational inertia, i.e. the following formula:

[0146]

[0147] where p is the air density, |V| is the velocity vector size passing through the rotor disk plane, including the free flow velocity V f and the axial induced velocity of the rotor v ia , and the rotor wake radius R w is determined by formula (3).

[0148] According to the angular momentum theorem, the relationship between the air rotational angular velocity increment ΔΩ and the corresponding torque is as follows:

[0149] Mdt = I z ΔΩ (7)

[0150] where M is the torque acting on the air, which is equal in size to the counter-torque of the rotor, and the sign is opposite.

[0151] As shown in Figure 4 , the air at infinity has no rotational motion before passing through the rotor disk, its angular velocity Ω0=0, when it passes through the rotor disk plane, it generates rotational motion around the rotor axis under the action of the rotor, its angular velocity changes to Ω1, when the airflow moves far enough downstream of the rotor, its angular velocity further accelerates, changes to Ω2. Therefore, in the above formula,

[0152] ΔΩ = Ω2- Ω0 (8)

[0153] Substitute (6) (7) into (8), we have:

[0154]

[0155] The work W done by the rotor torque on the air flow at the rotor disc and the change of the air rotational kinetic energy ΔP in a unit time dt can be expressed as:

[0156]

[0157] According to the kinetic energy theorem, the work done by the rotor torque on the air flow should be equal to the change of the air rotational kinetic energy W = ΔP, and considering Ω0= 0, we have:

[0158]

[0159] Assuming that the corresponding point of a microelement on the rotor disc is (r ψ), the circumferential induced velocity of the microelement in the ground axis system is:

[0160]

[0161] where M is the torque acting on the air, which is equal in magnitude to the rotor counter-torque, and the sign is opposite; |V| is the magnitude of the resultant velocity vector through the rotor disc plane, R w is the rotor wake radius; Δ = 1 represents right rotation, and Δ = -1 represents left rotation. Bs T

[0162] III. Rotor / airfoil interference area calculation:

[0163] Based on the above assumptions and the vortex tube model, the geometric shape of the rotor wake in space is a slanting cylinder, and the airfoil is a two-dimensional plane. The area of the airfoil immersed in the rotor wake area is actually equivalent to the area of the region surrounded by the cross section (wake ellipse) of the slanting cylinder and the airfoil rectangle. The shape of this region is relatively complex and can be calculated using the following calculation process. Figure 5 is a schematic diagram of the projection of the rotor wake on the plane where the airfoil is located and the wake parameters are labeled under the front side wind inflow.

[0164] Figure 5 Among the wake parameters shown, X TEK ,X LEK and Y TIPK are related to the position of the wake center of the projected ellipse. Among them, X TEK ,X LEKdenote the displacement of the wake center to the trailing edge and leading edge of the wing in the X-axis direction, respectively, both positive in the positive X-axis direction. TIPK denote the displacement of the wake center to the trailing edge and leading edge of the wing in the X-axis direction, respectively, both positive in the positive X-axis direction.

[0165]

[0166] X LEk = c w + X TEk (14)

[0167]

[0168] where d is the nacelle length, c w is the wing chord, e w is the distance from the nacelle rotation point to the trailing edge of the wing, and U Wk , V Wk , W Wk are the air flow velocities at the wing in the body axis system.

[0169] R WXK , R WYK , and δ K are related to the shape of the projected ellipse. R WXK , R WYK are the axis radii of the wake ellipse in the X-axis and Y-axis directions (before rotation). δ K is the angle of rotation of the wake projection (ellipse) around the wake center, with the projected ellipse rotating counterclockwise in the case of left wind and clockwise in the case of right wind.

[0170]

[0171] The above parameters can be calculated to obtain analytical expressions by geometric relationships. According to the above parameters, the interference area and its centroid position can be calculated, Figure 6 is a calculation flowchart.

[0172] F1(C 1k ,C 2k ):

[0173]

[0174] F2(C 1k ,C 2k ):

[0175]

[0176] where,

[0177]

[0178] The interference area calculation flow is actually based on the intersection position of the wake projection ellipse and the wing edge, and the calculation is carried out from bottom to top and then superimposed to obtain the result. The F1 function is used to calculate the area of the irregular figure of two curved edges, and the F2 function is used to calculate the area of the irregular figure of one curved edge.

[0179] The calculation flow above obtains The positions of the wake center to the centroid of the interference area in the X-axis direction and the Y-axis direction are denoted as positive directions of the X-axis and the Y-axis. In order to obtain the position of the centroid of the interference area relative to the barycenter in the body axis system, the position of the wake center relative to the aerodynamic center of the wing and the position of the aerodynamic center of the wing relative to the barycenter need to be calculated first. The calculation formula is as formula (22). As a simplification, the aerodynamic center of the wing is placed on the 1 / 4 chord line of the wing.

[0180]

[0181] Four, wing aerodynamic force calculation:

[0182] This part divides the wing into a slipstream area affected by the rotor interference and a free flow area not affected, and superimposes the aerodynamic forces of the two parts of the wing to obtain the aerodynamic force of the entire wing.

[0183] 4.1 Aerodynamic force of slipstream area:

[0184] The interference area of the rotor on the wing is affected by the axial induced velocity and the circumferential induced velocity of the rotor respectively. According to the solution of the axial / circumferential induced velocity in the rotor model part, the axial induced velocity is uniformly distributed in the interference area, and the circumferential induced velocity is linearly distributed in the interference area. The circumferential induced velocity of the rotor wake in the projection interference area on the plane where the wing is located is a function of the distance y (0≤y≤R w ) to the wing tip, and y=0 represents at the wing tip. The circumferential induced velocity on the surface of the wing can be represented as:

[0185]

[0186] According to the basic assumption (5) of 1.2, the average circumferential induced velocity of the interference area is the circumferential induced velocity at the centroid, where the centroid position

[0187]

[0188] For the interference area, there is The airflow velocity of the wing in the body axis system is:

[0189]

[0190] Then, the angle of attack and the sideslip angle of the wing slipstream area can be represented as:

[0191]

[0192] The dynamic pressure of the wing in the slipstream region is:

[0193]

[0194] The lift, drag and pitching moment of the wing in the slipstream region about the wind axis are:

[0195] L iWPk = q iWk S iWk C LWPk

[0196] D iWPk = q iWk S iWk C DWPk

[0197] M iWPk = q iWk S iWk c w C mWP (29) 4.2 Aerodynamic forces in free-stream region:

[0198] The calculation of the aerodynamic forces of the wing in the free-stream region is similar to that of the wing of a conventional aircraft, which is not affected by the rotor wake. The wing area in the free-stream region S WFS is the difference between the total wing area S W and the wing area in the slipstream region S iWk :

[0199] S WFS = S W - (S iWR + S iWL ) (30)

[0200] The dynamic pressure of the wing in the free-stream region qWFSis given by equation (21), where b W is the lateral position of the aerodynamic center of the wing relative to the center of gravity.

[0201]

[0202] The lift L WPF (considering the effect of the ailerons), drag D WPF and pitching moment M WPF of the wing in the free-stream region about the wind axis are:

[0203] L WPF = q WFS S WFS C LWP - q WFS S W CLδa |δ a |

[0204] D WPF =q WFS S WFS C DWP

[0205] M WPF =q WFS S WFS c w C mWP (32)

[0206] Five, wing aerodynamic interference area analysis:

[0207] 5.1 Forward flight state:

[0208] The projection of the rotor wake in the plane of the wing (wake ellipse) and the rectangular wing overlap to form the rotor wake on the upper surface of the wing interference area (slipstream area). XV-15 as a model calculation example, analysis of the wing aerodynamic interference area changes at different speeds and nacelle tilt angle in forward flight and side flight state.

[0209] In the helicopter mode, the area changes with the forward flight speed as shown in Figure 7 , where the solid small circle represents the nacelle tilt point of the wing. At this time, the projection of the rotor wake in the plane of the wing is circular (R WX =R WY =R W ). And with the increase of forward flight speed, the position of the wake projection gradually moves back, the slipstream area gradually decreases, and when the speed is 30 m / s, the wake completely deviates from the wing, but the wake projection does not occur. Deformation.

[0210] When the nacelle begins to tilt, as the forward flight speed increases, the position of the rotor wake projection in the plane of the wing gradually moves back, the slipstream area gradually decreases, and at the same time the wake projection begins to appear. Distortion in the X-axis direction (R WX gradually increases, R WY =R W does not change). At this time, the distortion is not the distortion of the rotor wake, but due to the tilt of the rotor disc, its projection in the plane of the wing is distorted, from a circle to an ellipse, and as the forward flight speed increases, the major axis of the ellipse also increases.

[0211] Figure 8The projected area of the rotor wake on the plane of the wing and the interference area of the rotor wake with the wing as a function of forward flight speed for the nacelle tilted 15°. Considering the increase of forward flight speed, the rotor induced velocity decreases, the rotor wake tilt angle increases, which leads to the projected ellipse of the rotor wake on the plane of the wing to have a larger long axis radius and to be more rearward. At 40 m / s, the rotor wake is completely offset from the wing.

[0212] As Figure 9 The projected area of the rotor wake on the plane of the wing and the interference area of the rotor wake with the wing as a function of forward flight speed for the nacelle tilted 30°. The results are similar to the case of the nacelle tilted 15°, and at 30 m / s, the rotor wake is completely offset from the wing.

[0213] 5.2 Sideslip state:

[0214] Since the left and right wing structures are symmetrical, when the crosswind speed is negative, it represents the left rotor wake projected on the plane of the left wing under the right crosswind; when the crosswind speed is positive, it represents the right rotor wake projected on the plane of the right wing under the right crosswind. However, the interference of the left and right rotor wakes with the wing is not symmetrical under crosswind, so the projected area of the left and right rotor wakes on the plane of the wing and the interference area of the rotor wake with the wing are drawn separately.

[0215] Figure 10 The projected area of the rotor wake on the plane of the wing and the interference area of the rotor wake with the wing as a function of right crosswind speed for the XV-15 tiltrotor in helicopter mode. It can be seen that in helicopter mode, when the forward speed is 0, as the right crosswind speed increases, the rotor wake tilts to the left, and the projection of the rotor wake on the plane of the wing also gradually moves to the left, but the projection does not deform (R WX = R WY = R W ). When the forward speed increases, the rotor wake ellipse also does not deform but is offset to the rear relative to the case when the forward speed is 0, as shown in Figure 11 .

[0216] If the nacelle is tilted and the forward speed is 0, as the right crosswind speed increases, the rotor wake is offset to the left, and the projected rotor wake ellipse on the plane of the wing is also distorted, R WY gradually increases (R WX > R W and does not change), and the projected ellipse rotates counterclockwise around the center of the rotor wake. Since the radii of the projected ellipse in the X and Y directions are close, the distortion and rotation are not easy to see, and the corresponding shape parameters can be referred to, and the corresponding schematic diagram is Figure 12 .

[0217] Table 1 Shape parameters of the rotor wake projected on the plane of the wing for the nacelle tilted 15°

[0218]

[0219] As shown in Table 1, R W is the rotor wake contraction radius, R WX and R WY respectively represent the radius of the wake projection in the X, Y direction in the plane of the wing, δ K represents the angle of rotation of the projection ellipse around the wake center. It can be seen that due to the nacelle forward tilt, the rotor induced velocity has a component in the X direction, making R WX > R W and remains unchanged; as the right wind speed increases, the wake lateral tilt angle starts from 0, making the radius in the Y direction also increase (right wing); the wake is longitudinally and laterally tilted at the same time, resulting in a rotating ellipse in the plane of the wing, and as the right wind speed increases, the angle of counterclockwise rotation also increases (right wing).

[0220] The above-described situation is more obvious when the forward flight speed is large. When the forward flight speed is 20 m / s, due to the wake tilt caused by the forward speed, the wake projection position at the wing position is shifted backward as a whole relative to the case with only crosswind, and the long axis (R WX ) is deformed more obviously. There is also a case where the forward flight speed is zero, the projection ellipse R WY increases and the projection ellipse rotates, as shown in Figure 13 .

[0221] Six, analysis of wing aerodynamic interference calculation results:

[0222] The present application takes XV-15 as a model calculation example, and the rotor / airfoil interference mechanism model is incorporated into the existing flight mechanics model to trim in forward flight state, and the following wing aerodynamic performance results are obtained.

[0223] In helicopter mode and airplane mode, the axial and circumferential induced velocities of the rotor play a major role in rotor / airfoil interference. In helicopter mode, as shown in Figure 14 is the ratio of wing lift to rotor lift of XV-15 tiltrotor in helicopter mode when considering rotor / airfoil aerodynamic interference and not considering aerodynamic interference. The downwash flow of the rotor makes the wing produce a downward force, but as the forward flight speed increases, the rotor wake gradually deviates from the wing, and the interference effect gradually decreases, until about 30 m / s completely disappears. It can be seen that after adding the rotor / airfoil aerodynamic interference model, the ratio of wing lift to rotor lift is closer to the result calculated by the GTRS model.

[0224] Figure 15The figure of the change of the increment of the wing aerodynamic interference ratio to the total lift of the wing in the state of the nacelle tilt angle of 45°, 60°, 75° and the airplane mode of 90°(rotor descent speed) is shown. When the tilt angle is 45°, the axial induced velocity still plays a dominant role, and the wing lift increment is negative, but with the increase of the tilt angle, the circumferential induced velocity gradually plays a significant role in the wing. In the airplane mode, the aerodynamic interference can reach about 10% of the wing lift. It can be seen that the circumferential induced velocity cannot be ignored for the rotor / wing aerodynamic interference.

[0225] In order to further analyze the aerodynamic performance of the wing in the transition mode, a suitable simulation condition in the tilt corridor is selected, as shown in Table 2. In the calculation process, the total pitch of the rotor, the angle of attack of the wing and the deflection angle of the rudder are all the values of the trim state under the working condition.

[0226] Table 2 Simulation conditions of transition mode

[0227]

[0228] Figure 16 The aerodynamic performance of the interference wing and the isolated wing without considering interference is compared. Among them, (a) is the lift and drag, (b) is the lift coefficient, (c) is the drag coefficient, and (d) is the lift-drag ratio. In hovering, the rotor axial induced velocity plays a dominant role in the interference, and the wing lift increment is negative. When the tilt angle is in the range of 10° to 30°, the rotor wake is deviated from the wing in the corresponding forward flight speed, the wing interference area is 0, so the interference effect is also zero.

[0229] With the increase of the tilt angle, the circumferential induced velocity gradually plays a significant role in the middle and late stages, and the rotor interference starts to have a lift-increasing effect on the wing. This is because the circumferential induced velocity changes the angle of attack distribution of the wing, and the lift coefficient also increases. At the same time, it is observed that the lift-drag ratio of the interference wing relative to the isolated wing also increases at about 45° to 75°.

[0230] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device embodiment, the above is only a preferred embodiment of the present invention. Since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment. The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited to this. Any technical personnel familiar with this technical field is within the technical scope disclosed by the present invention. For ordinary technical personnel in this technical field, changes or replacements that can be easily thought of should be covered within the protection scope of the present invention without departing from the principle of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for calculating the aerodynamic interference between the rotor and wing of a tiltrotor aircraft, characterized in that The following steps are involved: 1) Establish the body coordinate system and the hub coordinate system, calculate the coordinate transformation matrix between the hub coordinate system and the body coordinate system, specify the simplified assumptions of the model, and realize the unified processing of the data in the rotor and wing interference model; 2) A rotor model is established using blade element theory and a dynamic inflow model. Based on this, the axial induced velocity generated by the rotor at the wing is obtained. The circumferential induced velocity at the corresponding point of the rotor disc is calculated based on the angular momentum theorem and the rotational kinetic energy theorem, thereby obtaining the rotor circumferential induced velocity at the wing. 3) Based on the assumptions and simplified model, the shape and position parameters of the rotor wake, i.e., the projection of the wake ellipse onto the plane of the wing, are calculated. On this basis, the specific area and position of the overlapping area between the wake ellipse and the wing rectangle, i.e., the interference area, are calculated according to the system process. 4) Divide the wing into a slipstream region affected by the rotor interference and an unaffected freestream region. Calculate the aerodynamic forces in these two regions separately, and then superimpose the aerodynamic forces of the two parts to obtain the total aerodynamic force of the entire wing. 5) Calculate the position and area of ​​the wing interference region for the sample aircraft in forward and side flight at different speeds and tilt angles, and draw corresponding schematic diagrams to verify the rationality of the interference region calculation. At the same time, based on the aerodynamic interference relationship between the rotor and wing of the tiltrotor aircraft obtained in the above steps, further solve the aerodynamic force of the wing under the rotor and wing combination without considering interference, and compare and analyze the difference in aerodynamic performance with and without considering interference to verify the rationality and accuracy of the interference aerodynamic force calculation.

2. The method for calculating aerodynamic interference between rotors and wings of a tiltrotor aircraft according to claim 1, characterized in that: Step 1) The specific construction method of the body coordinate system and the hub coordinate system is as follows: the origin of the body coordinate system is located at the center of mass C of the entire aircraft, the X-axis is in the longitudinal symmetry plane of the entire aircraft, pointing to the nose, the Y-axis is perpendicular to the longitudinal symmetry plane, pointing to the right, and the Z-axis is in the longitudinal symmetry plane, and its direction is determined by the right-hand rule; the origin of the hub coordinate system is located at the hub center H, its X-axis points from an azimuth angle of 0° to 180°, the axis points from 270° of the right-hand rotor to 90°, the axis is perpendicular to the propeller disc plane, and is parallel to the engine nacelle, and its direction is determined by the right-hand rule.

3. The method for calculating aerodynamic interference between rotors and wings of a tiltrotor aircraft according to claim 2, characterized in that: Step 1) The coordinate transformation matrix T between the hub coordinate system and the body coordinate system Bs for: In the formula, β N is the nacelle tilt angle, β N =0° represents helicopter mode, β N =90° represents fixed-wing mode.

4. The method for calculating aerodynamic interference between rotors and wings of a tiltrotor aircraft according to claim 1, wherein: The simplified assumptions of the model in step 1) are as follows: 1.1) The wing is divided into two parts: the interference zone affected by the rotor wake and the free flow zone outside the wake. The aerodynamic force of the wing is equal to the sum of the aerodynamic forces in the interference zone and the free flow zone. 1.2) The rotor is equivalent to a disc plane with a radius of R and a rotor trail radius of R Wk ; 1.3) The airflow velocity in the area of ​​rotor interference with the wing can be considered as the superposition of the distant airflow velocity, the rotor axial induced velocity, and the circumferential induced velocity; 1.4) The rotor wake as a whole rotates about the rotor axis at a certain angular velocity, which has no effect on the shape of the rotor wake; 1.5) The average value of the aerodynamic angle of attack increment caused by the circumferential induced velocity in the rotor-wing interference region is the aerodynamic angle of attack increment at the centroid of the interference region.

5. The method for calculating aerodynamic interference between rotors and wings of a tiltrotor aircraft according to claim 1, characterized in that: Step 2) The rotor circumferential induced velocity calculation process is as follows: 2.1) Calculation of rotor axial induced speed: 2.11) According to the first-order harmonic Pitt-Peters dynamic inflow method, the distribution of dimensionless induced velocity on the rotor disc plane is obtained: Where: ν0,ν 1c ,ν 1s are the dimensionless term of rotor uniform inflow, the dimensionless term of first-order cosine inflow and the dimensionless term of first-order sine inflow, respectively. is the blade azimuth, is the spanwise position of the blade, dimensionless; 2.12) When hovering, the radius of the rotor trail at the wing is R Wk Based on the rotor radius, the rotor thrust coefficient and the nacelle length are expressed as: in, 2.13) At the rotor disc plane, the air flow through the disc plane should be equal to the product of the average axial induced velocity at the disc and the disc area; assuming that the free stream velocity vector is V f , the average axial induced velocity vector at the rotor disc is v ik , then the air flow through the propeller disc plane is πR 2 |v ik +V f |, downstream of the impeller disc, the airflow is constantly accelerating, the wake radius is constantly shrinking, but the air flow rate should remain unchanged, that is, it satisfies the relationship as shown in formula (5), and the incoming flow velocity in the interference zone at the wing can be solved; πR 2 |v ik +V f |=πR w 2 |v iWk +V f | (5) In formula (5), v iWk is the average axial induced velocity vector of the rotor at the wing, R w is the rotor wake radius at that location; 2.2) Calculation of rotor circumferential induced velocity: 2.21) Calculate the moment of inertia of the air added to the wake by integrating the mass flow rate of the air passing through the propeller disc. For a radius of R w The uniform tail flow, the mass flow rate of the tail flow per unit time dm / dt = ρ|V|A, where is the wake cross-sectional area; 2.21) By integrating the air loop passing through the propeller disk, we can obtain the moment of inertia rate per unit time added to the wake, i.e., dI z / dt, dI z It is understood as the cumulative moment of inertia, which is the following formula: Where ρ is the air density, |V| is the magnitude of the resultant velocity vector through the disc plane, including the free stream velocity V f and rotor axial induced velocity v ia , rotor wake radius R w Determined by formula (3); 2.22) According to the law of angular momentum, the relationship between the air rotational angular velocity increment ΔΩ and the corresponding torque is as follows: Mdt=I z DO(7) Where M is the torque acting on the air, which is equal to the rotor counter-torque in magnitude and opposite in sign. 2.23) Before the air at infinity passes through the rotor disc, it has no rotational motion and an angular velocity of Ω0 = 0. When it passes through the disc plane, it undergoes rotational motion around the rotor axis under the action of the rotor, and its angular velocity changes to Ω1. When the airflow moves far enough downstream of the rotor, its angular velocity accelerates further and changes to Ω2. Therefore, the above equation has ΔΩ=Ω2-Ω0 (8) Substituting into equations (6) and (7), we can obtain: 2.24) The work W done by the rotor torque on the airflow at the disc per unit time dt and the change in the air's rotational kinetic energy ΔP are expressed as follows: According to the kinetic energy theorem, the work done by the torque on the air should be equal to the change in the kinetic energy of the air, W = ΔP. Considering that Ω0 = 0, we can get: 2.25) Assume that the corresponding point of a certain infinitesimal element on the wing surface on the rotor disc is (r ψ), then the rotor circumferential induced velocity at this infinitesimal element in the Earth's axis system is: Where M is the torque acting on the air, which is equal to the rotor counter-torque and opposite in sign; |V| is the magnitude of the resultant velocity vector passing through the rotor disc plane, and R w is the rotor trail radius; Δ = 1 represents right rotation, Δ = -1 represents left rotation, T Bs is the coordinate transformation matrix between the hub coordinate system and the body axis system.

6. The method for calculating aerodynamic interference between rotors and wings of a tiltrotor aircraft according to claim 1, characterized in that: Step 3) The calculation process of the interference area between the trail ellipse and the wing rectangle is as follows: 3.1) Assume X TEK ,X LEK They represent the displacement of the trail center to the trailing edge and the leading edge of the wing in the X-axis direction, and both are positive in the positive direction of the X-axis; Y TIPK The displacement of the center of the trail in the lateral (Y-axis direction) direction (relative to the wing tip), with outward displacement being positive, and X TEK ,X LEK 、Y TIPK It is related to the position of the center of the projected ellipse and is calculated as: X LEk =c w +X TEk (14) 3.2) Assume R WXK ,R WYK is the radius of the trail ellipse in the X and Y directions before rotation, δ K R is the angle of rotation of the trail projection circle or ellipse around the trail center. In the case of left-side wind, the projection ellipse rotates counterclockwise, and in the case of right-side wind, it rotates clockwise. WXK ,R WYK , δ K is related to the shape of the projected ellipse, where 3.3) The above parameters are all calculated by geometric relationships to obtain analytical expressions. Based on the above parameters, the area of ​​the interference region and its centroid position can be calculated: F1(C 1k ,C 2k ): F2(C 1k ,C 2k ): in, The interference area calculation process is actually based on the intersection of the trail projection ellipse and the wing edge, which is partitioned from bottom to top and then superimposed. The F1 function is used to calculate the area of ​​an irregular figure with two curved edges, and the F2 function is used to calculate the area of ​​an irregular figure with one curved edge. 3.4) The above calculation process obtains is the position from the center of the wake to the centroid of the interference area in the X-axis and Y-axis directions, with the positive direction of the X-axis and Y-axis being positive. By calculating the position of the center of the wake relative to the aerodynamic center of the wing and the position of the aerodynamic center of the wing relative to the center of gravity, the position of the centroid of the interference area relative to the center of gravity in the body axis coordinate system is obtained. The calculation formula is as shown in Equation (22), where, for simplification, the aerodynamic center of the wing is placed on the 1 / 4 chord line of the wing:

7. The method for calculating aerodynamic interference between rotors and wings of a tiltrotor aircraft according to claim 1, characterized in that: Step 4) The total aerodynamic force of the wing is calculated as follows: 4.1) Aerodynamic force in the slipstream region: According to the solution of the axial and circumferential induced velocities of the rotor model, the axial induced velocity is uniformly distributed in the interference area, the circumferential induced velocity is linearly distributed in the interference area, and the circumferential induced velocity of the interference area of ​​the projection of the rotor wake on the plane where the wing is located is the distance y to the wing tip (0≤y≤R w ), y = 0 represents the wing tip, and the circumferential induced velocity on the wing surface is expressed as: According to the simplified assumption, the average circumferential induced velocity in the interference area is the circumferential induced velocity at the centroid, where Centroid location: For interference areas, The airflow velocity of the wing under the body axis is: Then, the angle of attack and sideslip angle of the wing slipstream region are expressed as: The dynamic pressure in the slipstream region of the wing is: From this, we can obtain the lift, drag and pitching moment in the wind axis of the wing slipstream area: L iWPk =q iWk S iWk C LWPk D iWPk =q iWk S iWk C DWPk M iWPk =q iWk S iWk c w C mWP (29); 4.2) Aerodynamic forces in the free flow area: The calculation process of the aerodynamic force of the wing in the free flow area that is not affected by the rotor wake is similar to that of the wing of a conventional aircraft. The wing area S in the free flow area is WFS is the total wing area S W and the slipstream wing area S iWk Difference: S WFS =S W -(S iWR +S iWL ) (30) The wing dynamic pressure qWFS in the free flow area is as shown in Equation (21), where b W is the lateral position of the aerodynamic center of the entire wing relative to the center of gravity; Then, the lift force L under the wind axis of the wing in the free flow area is WPF , resistance D WPF and pitching moment M WPF for: L WPF =q WFS S WFS C LWP -q WFS S W C Lδa |δ a | D WPF =q WFS S WFS C DWP M WPF =q WFS S WFS c w C mWP (32)。

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