A helicopter main reducer fairing aerodynamic shape design method and aerodynamic shape

Abstract

The application belongs to the technical field of helicopter aerodynamic design, and particularly relates to a helicopter main speed reducer fairing aerodynamic shape design method and aerodynamic shape, comprising the following steps: S1, determining the installation position of the main speed reducer fairing, and the position and size parameters of the oil cooler inlet on the main speed reducer fairing and the channel mouth of the main hub and its accessories; S2, designing the two-dimensional top view shape of the upper surface of the main speed reducer fairing as a spindle shape, and determining the shape parameters of the spindle shape; S3, designing the three-dimensional shape of the main speed reducer fairing based on the two-dimensional spindle shape, and determining the shape parameters of the three-dimensional shape, and taking the finally obtained three-dimensional shape as the fairing aerodynamic shape.

Description

Technical Field

[0001] This invention belongs to the field of helicopter aerodynamic design technology, and particularly relates to a method for aerodynamic shape design and aerodynamic shape of a helicopter main gearbox fairing. Background Technology

[0002] The main gearbox fairing of a helicopter houses the main gearbox and its accessories, oil cooler, and other components. Therefore, its shape is generally designed to be relatively large. In addition, it is also affected by the wake of the main rotor hub, etc. The airflow near the main gearbox fairing is easily separated, which not only increases the fuselage drag, but also causes unstable tail shedding vortices to act on the tail aerodynamic surface, resulting in tail sieving and affecting the comfort and safety of the helicopter.

[0003] The aerodynamic design of the main gearbox fairing focuses on optimizing its aerodynamic shape while meeting the requirements of internal component layout and structural design. This is achieved by reducing the frontal area and weakening flow separation to reduce fuselage aerodynamic drag, while also minimizing tail vibration issues, thereby improving the helicopter's flight performance and quality. This is especially crucial for heavy helicopters, whose main rotor hub and main gearbox platform are larger, potentially leading to increased drag and a greater likelihood of tail vibration. Therefore, the aerodynamic design methodology of the main gearbox fairing for heavy helicopters is of paramount importance. Summary of the Invention

[0004] This invention proposes an aerodynamic shape design method for a helicopter main gearbox fairing, which enables passive control of the airflow at the tail of the main gearbox fairing, reduces the aerodynamic drag of the helicopter fuselage, weakens the aerodynamic interference to the horizontal and vertical tail and other aerodynamic surfaces, and can meet the internal space arrangement requirements of the main gearbox fairing and achieve good integration with the overall shape of the fuselage. It is used to solve the problem that for heavy helicopters, the main rotor hub and main gearbox platform are larger, which may lead to greater drag and a greater likelihood of tail vibration.

[0005] To achieve the above objectives, the present invention employs the following technical solution.

[0006] A method for aerodynamic design of a helicopter main gearbox fairing, wherein the overall shape of the main gearbox fairing is symmetrically distributed about the longitudinal direction of the fuselage, the method comprising:

[0007] S1, Determine the installation position of the main reducer fairing, as well as the position and size parameters of the oil cooler inlet and the main propeller hub and its accessory passage on the main reducer fairing;

[0008] S2, design the top two-dimensional shape of the main reducer fairing as a spindle shape, and determine the shape parameters of the spindle shape;

[0009] S3, based on the two-dimensional shape of the spindle, designs the three-dimensional shape of the main reducer fairing and determines the shape parameters of the three-dimensional shape, and uses the final three-dimensional shape as the aerodynamic shape of the fairing.

[0010] Furthermore, in S1, the installation position of the main reducer fairing is determined, specifically as follows:

[0011] The main gearbox fairing is located on the upper part of the fuselage, with the main propeller hub and its accessories passing through from above. The front of the main gearbox fairing is connected to the engine compartment fairing, and the rear of the main gearbox fairing is connected to the fuselage transition section.

[0012] Furthermore, in S1, the specific location and dimensional parameters of the oil cooler inlet on the main reducer fairing and the main propeller hub and its accessory passage openings are as follows:

[0013] The front end of the main reducer fairing is provided with an oil radiator inlet. The plane where the oil radiator inlet is located makes an angle of 45° with the horizontal plane. The oil radiator inlet is elliptical with a major axis diameter of 1.0m and a minor axis diameter of 0.72m. The upper surface of the main reducer fairing is provided with a channel for the main propeller hub and its accessories, which is used to connect the main reducer to the main propeller hub and its accessories. The radius of the channel is 0.95m.

[0014] Furthermore, in S2, the dimensions of the spindle shape satisfy the following constraints:

[0015] The spindle-shaped long axis length L1≤7m, the center of the circular channel opening used to connect the main propeller hub is located at 1 / 3 of the long axis, where the short axis of the spindle-shaped is the longest, and the distance between the circular channel opening and the upper and lower sides of the spindle-shaped is L2≥0.1m, and the longest short axis L3≥2.1m;

[0016] Based on the above constraints, the parameters L1 and L2 of the spindle shape and the quadratic or quartic polynomial fitting curve equations are designed and optimized. CFD methods are used to evaluate the aerodynamic characteristics of the spindle shape to achieve the optimization goal of minimizing aerodynamic drag.

[0017] Furthermore, CFD was used to evaluate the aerodynamic characteristics of the spindle shape to achieve the optimization goal of minimizing aerodynamic drag. The optimized spindle parameters were obtained as L1 = 6.7m, L2 = 0.12m, and L3 = 2.14m.

[0018] With the center of the circular passage opening as the origin:

[0019] The equation of the first half of the spindle-shaped curve is: y = -0.15166x 2 +0.11178x+1.08417

[0020] Equation of the second half of the spindle-shaped curve:

[0021] y = -0.00132x4 +0.00256x 3 -0.03041x 2 -0.00489x+1.06293.

[0022] Furthermore, based on the spindle-shaped two-dimensional shape, the three-dimensional shape of the main reducer fairing is designed as follows:

[0023] Based on the determined spindle shape, draw the two-dimensional shape of the vertical section corresponding to the maximum point of the short axis on the upper surface of the spindle shape of the main reducer fairing. The vertical section is generally hyperbolic in shape. The upper part of the side of the vertical section is composed of arc 1. The lower part of the side of the section is tangent to the upper arc, resulting in tangent 2. Tangent 2 is connected downward to the middle fuselage.

[0024] The middle and rear parts of both sides of the main reducer fairing gradually taper towards the longitudinal symmetry plane in a hyperbolic shape, and intersect with spline lines at the tail of the main reducer fairing. The upper surface of the main reducer fairing takes the rear intersection point of the major axis and the circular channel opening as the starting point, and replaces the major axis of the middle and rear parts with an arc-shaped axis 3. The rear half of the upper surface of the main reducer fairing bends downward along the arc-shaped axis and transitions to the side of the fairing at the tail of the main reducer fairing. On the longitudinal symmetry plane of the fuselage, the tail of the fairing is composed of two arc lines 4, which are tangent to the lower part and connect with the transition section of the fuselage. The sides and tail of the fairing present a shape similar to a brim.

[0025] Furthermore, in S3, the shape parameters of the three-dimensional shape are determined, specifically as follows:

[0026] The angles and radii of the arc 1, the tangent of the arc 2, the arc axis 3, and the tail arc 4 are optimized and evaluated using CFD methods. The optimization goal is to suppress flow separation at the tail of the main reducer fairing.

[0027] The final optimized parameters are as follows:

[0028] The radius of arc 1 is 0.52m, and the central angle is 50°;

[0029] The angle between the tangent of the arc 2 and the longitudinal symmetry plane of the fuselage is 30°.

[0030] The radius of the arc-shaped axis 3 is 10m, and the central angle is 20°.

[0031] The tail arc 4 has a central angle of 20° and a radius of 0.4m for the upper arc and a central angle of 115° and a radius of 0.05m for the lower arc.

[0032] Furthermore, the method also includes: in S3,

[0033] The upper surface of the fairing is connected to the sides and tail of the fairing with a rounded corner of 0.07m, and then transitioned to the inlet of the lubricating oil radiator at the front.

[0034] Furthermore, after S3, the method further includes:

[0035] S4, add a deflector plate to the three-dimensional shape of the main reducer fairing:

[0036] The guide vanes are located on the rounded corners on both sides of the circular channel opening of the main propeller hub. The height of the guide vanes should be 0.4m lower than the distance between the fairing and the main propeller hub support arm. The longitudinal distance between the centerline of the guide vanes and the center of the circular channel opening of the main propeller hub is 0.16m.

[0037] The present invention also provides an aerodynamic shape for a helicopter main gearbox fairing, wherein the aerodynamic shape is as follows:

[0038] The main reducer fairing is spindle-shaped when viewed from above, and has a brim shape on both sides and at the rear.

[0039] This invention will achieve passive control of the wake near the main reducer by using an aerodynamic design method for a visor-type main reducer fairing suitable for heavy helicopters, thereby suppressing the separation vortex at the rear of the main reducer fairing, reducing exhaust drag, and reducing the aerodynamic interference of the detached vortex at the rear of the main reducer fairing on the horizontal and vertical tails. Attached Figure Description

[0040] Figure 1 The above-view two-dimensional shape of the helicopter main gearbox involved in this invention;

[0041] Figure 2 This invention relates to a cross-sectional view (BB) of the helicopter main gearbox fairing.

[0042] Figure 3 This invention relates to the upper surface of the helicopter main gearbox fairing;

[0043] Figure 4 This invention relates to the tail section of the helicopter main gearbox fairing;

[0044] Figure 5 The present invention relates to a three-view diagram of the helicopter main gearbox fairing;

[0045] Figure 6 The present invention relates to a flow field streamline diagram of the tail section of the helicopter main gearbox fairing;

[0046] Figure 7 The present invention relates to a helicopter main gearbox fairing guide plate. Detailed Implementation

[0047] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0048] This invention provides an aerodynamic shape design method for a helicopter main gearbox fairing. The fairing's upper surface, when viewed from above, is spindle-shaped, while the sides and tail section resemble a brim. The upper surface has deflectors on both sides. The design method is as follows:

[0049] Define the location and limitations of the main reducer fairing.

[0050] (Location) The main gearbox fairing is located on the upper part of the mid-fuselage. The main propeller hub, automatic swashplate and other components can pass through from above. It is connected to the engine compartment fairing in front and to the fuselage transition section in the rear.

[0051] (Restriction) The overall shape of the main gearbox fairing is symmetrically distributed about the longitudinal plane of the fuselage. Inside the main gearbox fairing, the lubricating oil radiator is located at the front end of the main gearbox. Therefore, the lubricating oil radiator inlet is located at the very front of the fairing. The plane where the inlet is located makes an angle of 45° with the horizontal plane. On this inclined plane, the inlet is elliptical with a major axis diameter of 1.0m and a minor axis diameter of 0.72m. The upper surface of the main gearbox fairing needs to be provided with a channel for the main gearbox to connect with the main propeller hub, automatic swashplate, and other components. The channel is circular with a radius of 0.95m.

[0052] Top-down 2D shape design and optimization

[0053] The top-view two-dimensional shape of the upper surface of the main reducer fairing is designed. The preliminary design of this two-dimensional shape is spindle-shaped, symmetrical about the longitudinal symmetry plane (AA) of the fuselage, as shown below. Figure 1 As shown, this airfoil-like shape design can effectively reduce aerodynamic drag.

[0054] Based on the location and constraints of the main reducer fairing, the length of the spindle's major axis, L1, is ≤ 7m. The center of the circular channel opening used to connect to the main propeller hub is located at 1 / 3 of the major axis, where the spindle's minor axis is longest. Furthermore, the distance between the circular channel opening and the upper and lower sides of the spindle, L2, is ≥ 0.1m, meaning the longest minor axis, L3, is ≥ 2.1m. Based on these constraints, the parameters L1 and L2 of the spindle, as well as the quadratic or quartic polynomial fitting curve equations, are designed and optimized. CFD methods are then used for evaluation to achieve the optimization objective of minimizing aerodynamic drag.

[0055] The final parameters of the spindle body were determined as L1 = 6.7m, L2 = 0.12m, and L3 = 2.14m, as well as the fitted curve equation. The drag coefficient of this shape was reduced by 20% compared with that before optimization.

[0056] With the center of the circular passage opening as the origin:

[0057] The first half: y = -0.15166x 2 +0.11178x+1.08417

[0058] The second half: y = -0.00132x 4 +0.00256x 3 -0.03041x 2 -0.00489x+1.06293

[0059] Optimization of 3D shape design (curved surfaces on both sides and brim at the rear)

[0060] The overall three-dimensional shape is symmetrically distributed about the longitudinal plane of symmetry (AA) of the fuselage. Based on the determined shape of the upper surface, the two-dimensional shape of the vertical section (BB) corresponding to the maximum minor axis of the upper surface is drawn. The upper part of the side of the vertical section is formed by an arc 1, and the lower part of the side of the section is tangent to the upper arc 2, and transitions downward to the mid-fuselage. The vertical section (BB) as a whole has a hyperbolic shape, as shown in the figure. Figure 2 As shown.

[0061] The middle and rear portions of both sides of the main reducer fairing gradually taper towards the longitudinal plane of symmetry in a hyperbolic shape, transitioning at the tail end with intersecting splines. The upper surface of the main reducer fairing, starting from the rear intersection point of its major axis and the circular channel opening, replaces the major axis of the middle and rear portions with an arc-shaped axis 3 (both located on the longitudinal plane of symmetry and of the same length). The rear half of the upper surface of the main reducer fairing bends downward along this arc-shaped axis and transitions to the fairing side at the tail end, as shown below. Figure 3 As shown; on the longitudinal symmetry plane of the fuselage, the tail section of the fairing is composed of two arcs 4, which tangent downwards to the fuselage transition section. The sides and tail of the fairing together resemble the shape of a hat brim. Figure 4 As shown.

[0062] Using the above-mentioned shape as the initial shape, the angles and radii of the arc line 1, the tangent of the arc line 2, the arc axis 3, and the tail arc line 4 are optimized, and evaluated using CFD methods. The optimization goal is to suppress flow separation at the tail of the main reducer fairing and reduce the aerodynamic interference of fairing shedding vortices on the horizontal and vertical tails.

[0063] The final optimized parameters yielded the following: Arc 1 has a radius of 0.52m and a central angle of 50°; the tangent 2 of Arc 2 forms an angle of 30° with the longitudinal symmetry plane of the fuselage; Arc axis 3 has a radius of 10m and a central angle of 20°; and the tail Arc 4 has an upper arc with a central angle of 20° and a radius of 0.4m, and a lower arc with a central angle of 115° and a radius of 0.05m. Finally, the upper surface of the fairing is connected to the sides and tail of the fairing with a fillet of 0.07m, and then seamlessly connected to the front oil cooler inlet. The final aerodynamic layout three-view drawing of the main reducer fairing is shown below. Figure 5As shown, CFD analysis indicates that this aerodynamic layout can achieve the goal of passive flow control, suppressing flow separation at the tail of the main reducer fairing, thereby reducing aerodynamic drag and weakening the aerodynamic interference of fairing shedding vortices on the tail aerodynamic surfaces, such as... Figure 6 As shown.

[0064] Optimization of the main reducer fairing guide plate design

[0065] To further reduce aerodynamic drag, guide vanes were added to the main gearbox fairing. The guide vanes are located on the rounded corners of the circular passage opening on both sides of the main rotor hub, such as... Figure 7 As shown, the height of the deflector should be 0.4m lower than the distance between the fairing and the main rotor hub arm. Based on the above constraints, the height (5), length (6), and position of the deflector were optimized, and CFD methods were used for evaluation to achieve the most significant reduction in fuselage aerodynamic drag.

[0066] The final optimized design yielded a guide vane with a length of 2.3m and a height of 0.3m. The longitudinal distance between the centerline of the guide vane and the center of the circular passage opening of the main propeller hub was 0.16m. CFD calculations and evaluations showed that this design reduced the fuselage drag coefficient by 3% compared to the original fuselage design.

[0067] The main reducer fairing designed in this invention adopts a top-view spindle shape, with brim-shaped sides and tail, and an aerodynamic layout with guide vanes installed on both sides of the upper surface. It incorporates passive flow control technology, causing the airflow on the surface of the main reducer fairing to deflect upwards along the brim shape on both sides and tail, thus reducing flow separation. Figure 7 As shown, this not only suppresses the generation of large separation vortices in the blunt body and reduces aerodynamic drag, but also, to a certain extent, avoids the main gearbox fairing wake directly acting on the horizontal and vertical tails, thereby weakening the interference of the main gearbox fairing shedding vortices on the tail aerodynamic surfaces and minimizing the occurrence of tail-end sieving. This main gearbox fairing aerodynamic design method, while meeting the requirements of internal space layout and structural design, possesses good aerodynamic characteristics and is suitable for heavy helicopters with large dimensions and severe airflow separation at the rear of the main gearbox.

[0068] The present invention proposes an aerodynamic design method for a helicopter main gearbox fairing, which can passively control the airflow at the tail of the main gearbox fairing, causing the airflow to deflect upward along the sides and the shape of the tail brim and reducing flow separation. This suppresses the generation of large separation vortices at the rear body, thereby reducing aerodynamic drag and weakening the aerodynamic interference of the shedding vortex at the tail of the main gearbox fairing on the tail aerodynamic surface, thus effectively improving the flight performance and quality of the helicopter.

Claims

1. A method for designing the aerodynamic shape of a helicopter main gearbox fairing, characterized in that, The overall shape of the main reducer fairing is symmetrically distributed about the longitudinal direction of the fuselage, and the method includes: S1, Determine the installation position of the main reducer fairing, as well as the position and size parameters of the oil cooler inlet and the main propeller hub and its accessory passage on the main reducer fairing; S2, design the top two-dimensional shape of the main reducer fairing as a spindle shape, and determine the shape parameters of the spindle shape; S3, based on the two-dimensional shape of the spindle, designs the three-dimensional shape of the main reducer fairing and determines the shape parameters of the three-dimensional shape, and uses the final three-dimensional shape as the aerodynamic shape of the fairing.

2. The aerodynamic shape design method for a helicopter main gearbox fairing according to claim 1, characterized in that, In S1, the installation position of the main reducer shroud is determined, specifically as follows: The main gearbox fairing is located on the upper part of the fuselage, with the main propeller hub and its accessories passing through from above. The front of the main gearbox fairing is connected to the engine compartment fairing, and the rear of the main gearbox fairing is connected to the fuselage transition section.

3. The aerodynamic shape design method for a helicopter main gearbox fairing according to claim 1, characterized in that, In S1, the specific positions and dimensions of the oil cooler inlet on the main reducer fairing and the main propeller hub and its accessory passages are as follows: The front end of the main reducer fairing is provided with an oil radiator inlet. The plane where the oil radiator inlet is located makes an angle of 45° with the horizontal plane. The oil radiator inlet is elliptical with a major axis diameter of 1.0m and a minor axis diameter of 0.72m. The upper surface of the main reducer fairing is provided with a channel for the main propeller hub and its accessories, which is used to connect the main reducer to the main propeller hub and its accessories. The radius of the channel is 0.95m.

4. The aerodynamic shape design method for a helicopter main gearbox fairing according to claim 1, characterized in that, In S2, the dimensions of the spindle shape satisfy the following constraints: The spindle-shaped long axis length L1≤7m, the center of the circular channel opening used to connect the main propeller hub is located at 1 / 3 of the long axis, where the short axis of the spindle-shaped is the longest, and the distance between the circular channel opening and the upper and lower sides of the spindle-shaped is L2≥0.1m, and the longest short axis L3≥2.1m; Based on the above constraints, the parameters L1 and L2 of the spindle shape and the quadratic or quartic polynomial fitting curve equations are designed and optimized. CFD methods are used to evaluate the aerodynamic characteristics of the spindle shape to achieve the optimization goal of minimizing aerodynamic drag.

5. The aerodynamic shape design method for a helicopter main gearbox fairing according to claim 4, characterized in that, The aerodynamic characteristics of the spindle shape were evaluated using CFD to achieve the optimization goal of minimizing aerodynamic drag. The optimized parameters of the spindle were obtained as L1 = 6.7m, L2 = 0.12m, and L3 = 2.14m. With the center of the circular passage opening as the origin: The equation of the first half of the spindle-shaped curve is: y = -0.15166x 2 +0.11178x+1.08417 Equation of the second half of the spindle-shaped curve: y=-0.00132x 4 +0.00256x 3 -0.03041x 2 -0.00489x+1.06293。 6. The aerodynamic shape design method for a helicopter main gearbox fairing according to claim 5, characterized in that, S3, based on the two-dimensional shape of a spindle, designs the three-dimensional shape of the main reducer fairing, specifically as follows: Based on the determined spindle shape, draw the two-dimensional shape of the vertical section corresponding to the maximum point of the short axis on the upper surface of the spindle shape of the main reducer fairing. The vertical section is generally hyperbolic in shape. The upper part of the side of the vertical section is composed of arc 1. The lower part of the side of the section is tangent to the upper arc, resulting in tangent 2. Tangent 2 is connected downward to the middle fuselage. The middle and rear parts of both sides of the main reducer fairing gradually taper towards the longitudinal symmetry plane in a hyperbolic shape, and intersect with spline lines at the tail of the main reducer fairing. The upper surface of the main reducer fairing takes the rear intersection point of the major axis and the circular channel opening as the starting point, and replaces the major axis of the middle and rear parts with an arc-shaped axis 3. The rear half of the upper surface of the main reducer fairing bends downward along the arc-shaped axis and transitions to the side of the fairing at the tail of the main reducer fairing. On the longitudinal symmetry plane of the fuselage, the tail of the fairing is composed of two arc lines 4, which are tangent to the lower part and connect with the transition section of the fuselage. The sides and tail of the fairing present a shape similar to a brim.

7. The aerodynamic shape design method for a helicopter main gearbox fairing according to claim 6, characterized in that, In S3, the shape parameters of the three-dimensional shape are determined, specifically: The angles and radii of the arc 1, the tangent of the arc 2, the arc axis 3, and the tail arc 4 are optimized and evaluated using CFD methods. The optimization goal is to suppress flow separation at the tail of the main reducer fairing. The final optimized parameters are as follows: The radius of arc 1 is 0.52m, and the central angle is 50°; The angle between the tangent of the arc 2 and the longitudinal symmetry plane of the fuselage is 30°. The radius of the arc-shaped axis 3 is 10m, and the central angle is 20°. The tail arc 4 has a central angle of 20° and a radius of 0.4m for the upper arc and a central angle of 115° and a radius of 0.05m for the lower arc.

8. The aerodynamic shape design method for a helicopter main gearbox fairing according to claim 6, characterized in that, The method further includes: in S3, The upper surface of the fairing is connected to the sides and tail of the fairing with a rounded corner of 0.07m, and then transitioned to the inlet of the lubricating oil radiator at the front.

9. The aerodynamic shape design method for a helicopter main gearbox fairing according to claim 1, characterized in that, Following S3, the method further includes: S4, add a deflector plate to the three-dimensional shape of the main reducer fairing: The guide vanes are located on the rounded corners on both sides of the circular channel opening of the main propeller hub. The height of the guide vanes should be 0.4m lower than the distance between the fairing and the main propeller hub support arm. The longitudinal distance between the centerline of the guide vanes and the center of the circular channel opening of the main propeller hub is 0.16m.

10. An aerodynamic shape for a helicopter main gearbox fairing, characterized in that, The aerodynamic shape is obtained by the method described in any one of claims 1-9, and the aerodynamic shape is as follows: The main reducer fairing is spindle-shaped when viewed from above, and has a brim shape on both sides and at the rear.

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