Downwash weight gain parameterization method for tilt-rotor aircraft
By constructing a partitioned parameterized model of the tiltrotor aircraft, the aerodynamic interference of the rotor on the fuselage was solved, enabling rapid and accurate estimation of downwash weight gain and improving the efficiency of aircraft performance analysis.
Patent Information
- Application Number
- CN202510505669.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-22
- Publication Date
- 2026-02-10
AI Technical Summary
In hovering and low-speed flight, tiltrotor aircraft experience severe aerodynamic interference from the rotor on the wings and fuselage, leading to increased weight during downwash. Existing modeling methods are complex and have long calculation cycles, which affects the performance of the aircraft.
The tiltrotor aircraft is parameterized using a partitioning method, including the left nacelle, right nacelle, left wing, right wing, and fuselage. The aerodynamic characteristics of the rotor downwash are utilized, and parameterization is achieved through shape factor, load function, and weighting coefficient, simplifying the calculation process.
It can quickly obtain downwash weight gain estimation data, improve the accuracy of flight mechanics models, simplify the calculation process, and has great engineering application value.
Smart Images
Figure CN121502902A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of aircraft aerodynamic design and analysis, and relates to a parameterization method for weight gain during downwashing of tiltrotor aircraft. Background Technology
[0002] Tiltrotor aircraft, combining the vertical takeoff and landing (VTOL) and hovering capabilities of helicopters with the cruise capabilities of fixed-wing aircraft, are widely used in military and civilian air transport. The unique configuration of tiltrotor aircraft brings the combined performance advantages of helicopters and fixed-wing aircraft. However, in hovering and low-speed flight, the rotors cause significant aerodynamic interference to the wings and fuselage, resulting in substantial weight gain and affecting the performance of the tiltrotor aircraft. In helicopter mode, the two rotors are located above the wings. The rotors generate a strong downwash (rotor wake). This downwash flows downwards through the nacelle and wings, and then converges above the fuselage before continuing upwards, forming a circulation-like region above the fuselage. This airflow motion generates downward loads on the wings and fuselage, known as downwash weight gain. Downwash weight gain in tiltrotor aircraft is typically obtained through flow field simulation using full-aircraft CFD analysis and modeling, or by combining rotor wake with wing aerodynamic modeling. The modeling process is complex and computationally intensive. Summary of the Invention
[0003] Purpose of the invention: This invention proposes a parameterization method for the underwash weight gain of tiltrotor aircraft, which can quickly obtain estimated data on the underwash weight gain of tiltrotor aircraft and can be integrated into the analysis of flight mechanics models to improve the accuracy of the models.
[0004] Technical solution: A parameterization method for weight gain during downwashing in tiltrotor aircraft is provided, including: Based on the overall configuration characteristics of tiltrotor aircraft, the different aerodynamic characteristics of the fuselage shape through which the rotor downwash airflow passes are utilized. The parameterization is carried out using a partitioning method, and then integrated to achieve parameterization of downwash weight gain.
[0005] Furthermore, based on the overall configuration characteristics of the tiltrotor aircraft, and utilizing the different aerodynamic characteristics of the fuselage shape through which the rotor downwash airflow passes, a zonal method is used for parameterization, followed by synthesis, to achieve parameterization of downwash weight gain, including: The tiltrotor aircraft is divided into regions encompassing the entire area through which the rotor downwash flows; these regions include: the left nacelle, the right nacelle, the left wing, the right wing, and the fuselage; Based on the geometric characteristics of each parameterized partition, the downwash weight gain Wi of each parameterized partition is parameterized separately; among them, the left and right nacelles are parameterized using cylinders, the left and right wings are parameterized using discrete wing sections, and the fuselage is parameterized using cuboids.
[0006] Furthermore, the specific steps for parameterizing the left and right nacelles using cylinders include: The shape factor Ai in the parameterization of the underwash weight gain Wi of the left and right nacelles is parameterized in the following form: A1 or A2 = CF * (l / d); Among them, the geometric parameter l is defined by the nacelle length, and the geometric parameter d is defined by the widest dimension of the nacelle along the wing span direction; The load function fti for the downwash weight gain parameterization of both left nacelle 1 and right nacelle 2 adopts the following parameterization form: ft1 or ft2 = kt * ts; Among them, the characteristic parameter kt of the nacelle is determined linearly based on the vertical distance between rotor a and the left or right wing, and the thrust function ts of rotor a is determined by its aerodynamic design characteristics. The smoothness of the nacelle shape determines the ki parameter in the downwash weight gain Wi parameterization of left nacelle 1 and right nacelle 2.
[0007] Furthermore, the CF of the nacelle is set between 0.3 and 0.5 based on the similarity between the nacelle's shape and the cylinder, the kt of the nacelle is set between 0.4 and 0.5, the ts is set between 660 and 1100, and the ki of the nacelle is set between 0.9 and 1.1.
[0008] Furthermore, the specific steps for parameterizing the left and right wings using discrete wing segments include: Determine the parameterization form of the underwash weight gain Wi parameter for the left and right wings; The underwash weight gain Wi of the left and right wings is obtained by summing the weight gain of all discrete segments: ; In this configuration, a single wing is uniformly discrete into n segments, where n>10. The parameter l is the length of each discrete wing segment, the parameter C is the geometric chord length of the wing, and the parameter Xj is the distance from the j-th wing segment to the wingtip.
[0009] In the parameterization of the underwash weight gain Wi of each discrete wing segment of the left and right wings, the shape factor Ai is set to a constant parameter. The load function ftj, parameterized by Wi for the underwash weight gain of the left and right wings, first increases from the outer edge of the wing inwards and then remains constant. The maximum position is located at a distance of 0.35 times the rotor diameter D from the outer edge of the wing. Before the maximum position, it increases linearly with a slope k.
[0010] ftj=kt*(k*Xj +ts0)Xj<0.35D; ftj=kt*ts1Xj≥0.35D; Among them, the characteristic parameter kt takes the same range as the left nacelle and the right nacelle, and the initial thrust function value ts0, the constant thrust function value ts1 and the slope k at the outer end of the wing are determined by the aerodynamic design characteristics of rotor a.
[0011] In the parameterization of the weight gain Wi of the left and right wings, ki is determined by the smoothness of the wing surface.
[0012] Furthermore, the ki value of the wing ranges from 0.95 to 1.05; The Ai of the wing is linearly interpolated between 0.9 and 0.6 based on the deflection angle of the flaperon b. For the wing, a ts0 value between 150 and 200 has a better effect, a ts1 value between 800 and 1200, and a k value between 160 and 230.
[0013] Furthermore, the specific steps for parameterizing the fuselage using a cuboid shape include: The parameter l for the weight gain Wi under the fuselage is the length of the fuselage influence area, the parameter w is the fuselage width, and the parameter h is the fuselage height. The shape factor Ai is characterized by being parameterized in the following form: A5 = CF * (w / h); The load function fti of the fuselage underwash weight gain parameter Wi adopts constant parameters, with a value of ft5=kt*ts1, where the characteristic parameter value kt and the tension function value ts1 are the same as those of the left wing and the right wing; In the parameterization of the weight gain during underwashing of the machine body, ki is determined by the smoothness of the machine body surface.
[0014] Furthermore, the value of ki for the fuselage ranges from 0.95 to 1.05; the influence coefficient CF is taken from 0.5 to 0.8 depending on the size of the chamfer of the fuselage cross section.
[0015] Beneficial Effects: This invention proposes a parameterized method for underwash weight gain in tiltrotor aircraft, which can quickly obtain estimated underwash weight gain data and integrate it into flight dynamics model analysis, improving model accuracy. Compared to CFD analysis techniques, this invention does not require the precise geometry of the tiltrotor aircraft and can quickly provide underwash weight gain results, thus having greater engineering application value. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the parameterized components of a tiltrotor aircraft.
[0017] Figure 2 A schematic diagram illustrating the parameterization of weight gain during the washout of a tiltrotor aircraft.
[0018] Figure 3 This is a schematic diagram of the parameterization of nacelle 1.
[0019] Figure 4 This is a schematic diagram of the parametric configuration of wing 2.
[0020] Figure 5 This is a schematic diagram showing the change of the tension function ts along the wing aspect ratio.
[0021] Figure 6 This is a schematic diagram of the fuselage with four parameters. Detailed Implementation
[0022] This invention proposes a parameterization method for downwash weight gain in tiltrotor aircraft. Based on the overall configuration characteristics of the tiltrotor aircraft, the method utilizes the different aerodynamic characteristics of the fuselage shape through which the rotor downwash airflow passes, employs a partitioning method to construct parameters, and then synthesizes them to achieve parameterization of downwash weight gain.
[0023] 1. For example Figure 1-2 As shown, the parameterized partitioning of the downwash weight gain of the tiltrotor aircraft consists of the left nacelle 1, the right nacelle 2, the left wing 3, the right wing 4, and the fuselage 5, which can cover the entire flow area of the rotor downwash.
[0024] 2. Based on the geometric characteristics of each parameterized partition, the downwash and weighting Wi of each parameterized partition is parameterized separately, such as... Figure 3 As shown, the left nacelle 1 and the right nacelle 2 are parameterized using cylinders, as follows: Figure 4 As shown, the left wing 3 and the right wing 4 are parameterized using discrete wing segments, as follows: Figure 6 As shown, the fuselage 5 is parameterized using a cuboid. The total underwash weight gain W is summed over the zone weight gain.
[0025]
[0026] 3. The weight gain Wi of each zone is parameterized using the shape factor Ai, the zone projected area Si, the load function fti of the rotor 8, and the weighting coefficient ki, and adopts the following unified form.
[0027] Wi=ki*Ai*Si* fti 4. The shape factor Ai in the parameterization of the left nacelle 1 and right nacelle 2 underwash weight gain Wi is characterized by being parameterized in the following form. Wherein, the geometric parameter l is defined by the nacelle length, the geometric parameter d is defined by the widest dimension of the nacelle along the wing span, and the influence coefficient CF is optimally set between 0.3 and 0.5 based on the similarity between the nacelle shape and a cylinder.
[0028] A1 or A2 = CF * (l / d) 5. The load function fti for the downwash weight gain Wi parameterization of both left nacelle 1 and right nacelle 2 adopts the following parameterization form. Among them, the characteristic parameter kt is determined linearly based on the vertical distance between rotor a and the left wing 3 or right wing 4, with a value between 0.4 and 0.5 showing better results. The rotor a thrust function ts is determined by its aerodynamic design characteristics, with a value between 660 and 1100 showing better results. Figure 5 As shown.
[0029] ft1 or ft2 = kt * ts 6. In the parameterization of the weight gain Wi parameterization for left nacelle 1 and right nacelle 2, ki is determined by the smoothness of the nacelle's shape, and a value between 0.9 and 1.1 has the best effect.
[0030] 7. The parameterized form of the underwash weight gain Wi for the left wing 3 and the right wing 4 is as follows: Each wing is uniformly discretized into n segments (n>10), where parameter l is the length of each discrete wing segment, parameter C is the geometric chord length of the wing, and parameter Xj is the distance from the wingtip to the j-th wing segment. The underwash weight gain Wi for the left wing 3 and the right wing 4 is obtained by summing the weight gain of all discrete segments.
[0031]
[0032] 8. In the parameterization of the left wing 3 and right wing 4 underwash weight gain Wi, the shape factor Ai is a constant parameter for all discrete wing segments. According to the linear interpolation of the deflection angle of the flap and aileron b between 0.9 and 0.6, it has a better effect.
[0033] 9. The parameterized load function ftj for the downwash weight gain Wi of the left wing (3) and right wing (4) first increases from the outer edge of the wing inwards and then remains constant, with the maximum position at a distance of 0.35 times the rotor diameter D from the outer edge of the wing. Before the maximum position, it increases linearly with a slope k. Among them, the characteristic parameter kt has the same value range as the left nacelle 1 and right nacelle 2. The initial thrust function value ts0, the constant thrust function value ts1, and the slope k at the outer edge of the wing are determined by the aerodynamic design characteristics of rotor a. A value of ts0 between 150 and 200 has a better effect, a value of ts1 between 800 and 1200 has a better effect, and a value of k between 160 and 230 has a better effect.
[0034] ftj=kt*(k*Xj +ts0)Xj<0.35D ftj=kt*ts1Xj≥0.35D 10. In the parameterization of the weight gain Wi parameterization for the left wing 3 and the right wing 4, ki is determined by the smoothness of the wing surface, and a value between 0.95 and 1.05 has the best effect.
[0035] 11. The parameter l for the weight gain Wi of the lower washing of the fuselage is the length of the fuselage influence area, the parameter w is the width of the fuselage, and the parameter h is the height of the fuselage. The shape factor Ai is characterized by being parameterized in the following form. Among them, the influence coefficient CF is optimally set between 0.5 and 0.8 based on the size of the chamfer of the fuselage cross-section.
[0036] A5 = CF * (w / h) 12. The load function fti of the fuselage 5 underwash weight increase Wi parameterization adopts constant parameters, with the value ft5=kt*ts1, where the characteristic parameter value kt and the tension function value ts1 are the same as those of the left wing 3 and the right wing 4.
[0037] 13. The ki parameter in the Wi parameterization of the weight gain of the machine body under 5 washes is determined by the smoothness of the machine body surface. A value between 0.95 and 1.05 has the best effect.
[0038] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. 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 described embodiments are only some, not all, of the embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.
[0039] In the description of this invention, it should be understood that the terms "center", "axial", "vertical", "upper", "lower", "upper end", "bottom end", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention.
[0040] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the following claims.
[0041] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A parameterization method for weight gain during descent in tiltrotor aircraft, characterized in that, include: Based on the overall configuration characteristics of tiltrotor aircraft, the different aerodynamic characteristics of the fuselage shape through which the rotor downwash airflow passes are utilized. The parameterization is carried out using a partitioning method, and then integrated to achieve parameterization of downwash weight gain.
2. The method according to claim 1, characterized in that, Based on the overall configuration characteristics of tiltrotor aircraft, and utilizing the different aerodynamic characteristics of the fuselage shape through which the rotor downwash airflow passes, a zonal method is used for parameterization, followed by synthesis, to achieve parameterization of downwash weight gain, including: The tiltrotor aircraft is divided into regions encompassing the entire area through which the rotor downwash flows; these regions include: the left nacelle, the right nacelle, the left wing, the right wing, and the fuselage; Based on the geometric characteristics of each parameterized partition, the downwash weight gain Wi of each parameterized partition is parameterized separately; among them, the left and right nacelles are parameterized using cylinders, the left and right wings are parameterized using discrete wing sections, and the fuselage is parameterized using cuboids.
3. The method according to claim 2, characterized in that, The specific steps for parameterizing the left and right nacelles using cylinders include: The shape factor Ai in the parameterization of the underwash weight gain Wi of the left and right nacelles is parameterized in the following form: A1 or A2 = CF * (l / d); Among them, the geometric parameter l is defined by the nacelle length, and the geometric parameter d is defined by the widest dimension of the nacelle along the wing span direction; The load function fti for the downwash weight gain parameterization of both left nacelle 1 and right nacelle 2 adopts the following parameterization form: ft1 or ft2 = kt * ts; Among them, the characteristic parameter kt of the nacelle is determined linearly based on the vertical distance between rotor a and the left or right wing, and the thrust function ts of rotor a is determined by its aerodynamic design characteristics. The smoothness of the nacelle shape determines the ki parameter in the downwash weight gain Wi parameterization of left nacelle 1 and right nacelle 2.
4. The method according to claim 2, characterized in that, The CF of the nacelle is taken between 0.3 and 0.5 depending on the similarity between the nacelle's shape and the cylinder. The kt value of the nacelle is between 0.4 and 0.
5. The ts value is between 660 and 1100. The ki value of the nacelle is between 0.9 and 1.
1.
5. The method according to claim 1, characterized in that, The specific steps for parameterizing the left and right wings using discrete wing segments include: Determine the parameterization form of the underwash weight gain Wi parameter for the left and right wings; The underwash weight gain Wi of the left and right wings is obtained by summing the weight gain of all discrete segments: ； In this configuration, a single wing is uniformly discrete into n segments, where n>10. The parameter l is the length of each discrete wing segment, the parameter C is the geometric chord length of the wing, and the parameter Xj is the distance from the j-th wing segment to the wingtip. In the parameterization of the underwash weight gain Wi of each discrete wing segment of the left and right wings, the shape factor Ai is set to a constant parameter. The load function ftj, parameterized by Wi for the underwash weight gain of the left and right wings, first increases from the outer edge of the wing inwards and then remains constant. The maximum position is located at a distance of 0.35 times the rotor diameter D from the outer edge of the wing. Before the maximum position, it increases linearly with a slope k. ftj=kt*(k*Xj +ts0)Xj<0.35D; ftj=kt*ts1Xj≥0.35D; Among them, the characteristic parameter kt takes the same range as the left nacelle and the right nacelle, and the initial thrust function value ts0, the constant thrust function value ts1 and the slope k at the outer end of the wing are determined by the aerodynamic design characteristics of rotor a. In the parameterization of the weight gain Wi of the left and right wings, ki is determined by the smoothness of the wing surface.
6. The method according to claim 5, characterized in that, The ki value of the wing ranges from 0.95 to 1.05; The Ai of the wing is linearly interpolated between 0.9 and 0.6 based on the deflection angle of the flaperon b. For the wing, a ts0 value between 150 and 200 has a better effect, a ts1 value between 800 and 1200, and a k value between 160 and 230.
7. The method according to claim 1, characterized in that, The specific steps for parameterizing the fuselage using a cuboid shape include: The parameter l for the weight gain Wi under the fuselage is the length of the fuselage influence area, the parameter w is the fuselage width, and the parameter h is the fuselage height. The shape factor Ai is characterized by being parameterized in the following form: A5 = CF * (w / h); The load function fti of the fuselage underwash weight gain parameter Wi adopts constant parameters, with a value of ft5=kt*ts1, where the characteristic parameter value kt and the tension function value ts1 are the same as those of the left wing and the right wing; In the parameterization of the weight gain during underwashing of the machine body, ki is determined by the smoothness of the machine body surface.
8. The method according to claim 7, characterized in that, The value of ki for the fuselage ranges from 0.95 to 1.05; the influence coefficient CF is taken from 0.5 to 0.8 depending on the size of the chamfer of the fuselage cross section.
9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method as described in any one of claims 1-8.