Special-shaped air inlet channel lip for on-wing integrated distributed propulsion short cabin unit

Abstract

The invention relates to the technical field of aircraft propulsion systems, in particular to a special-shaped air inlet lip for an on-wing integrated distributed propulsion short cabin unit. The lip is located at the starting part of the air inlet section and is defined by an upper lip, a lower lip, a left lip and a right lip; the inner surface of the upper lip is arc-shaped; the inner surface of the lower lip is linear and is smoothly fused with the upper surface of the wing; the inner surfaces of the left and right lips are curved surfaces with curved sweep characteristics, and the lower half parts of the left and right lips are in an inward-contracting shape; the length of the air inlet channel is defined as the axial distance from the foremost edge of the upper lip to the section of the inlet of the ducted fan and is not greater than the fan diameter D; a first rectification area and a second rectification area are arranged in the air inlet channel to optimize a flow field. Through the fusion design of the special-shaped lip and the wing and the compact air inlet channel, the requirement for compact integrated layout on the wing is met, meanwhile, the additional resistance of the nacelle is effectively reduced, the total pressure recovery coefficient not lower than 0.9 and the flow coefficient larger than 0.8 are guaranteed, and uniform and stable high-quality air inlet is provided for the ducted fan.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aircraft propulsion system, more particularly, to a special-shaped inlet lip for wing-integrated distributed propulsion nacelle unit. The wing-integrated distributed propulsion nacelle unit is composed of a plurality of nacelle units arranged along the wing span and assembled on the upper surface of the wing. Each nacelle unit has its own inlet, and the inlet part is called the lip. The lip of each nacelle unit is specially shaped, i.e. the special-shaped inlet lip. The lower edge of the special-shaped inlet lip is tangent to the upper surface of the wing at the installation position, i.e. the two profiles are smoothly connected and seamlessly integrated to form a continuous aerodynamic surface. BACKGROUND

[0002] Due to the global energy industry reform and the demand for green development, as well as the development of new energy power technology, all-electric propulsion regional aircraft is becoming possible. Compared with traditional fuel aircraft, electric propulsion aircraft directly drives fan (or propeller) and other propulsion devices through electric motor to generate thrust, which has the characteristics of simple structure and flexible arrangement. Among them, distributed propulsion is a high-efficiency power device layout form, which uses a plurality of small power devices arranged along the wing span to form an array, and generates forward propulsion by accelerating air to the rear. The corresponding power device of the distributed electric propulsion layout in the current aviation technology is mainly electric ducted fan.

[0003] When the ducted fan array is arranged close to the wing or fuselage, the boundary layer suction effect will be generated, which helps to improve the propulsion efficiency. However, the airflow on the surface of the wing or fuselage and the inlet and exhaust of the ducted fan will also produce strong aerodynamic coupling and interference. In order to ensure that the power system has excellent aerodynamic performance in various flight conditions, it is necessary to provide high-quality fairing for the inlet of the power device through the power nacelle. However, the nacelle obtained by the traditional design method rarely considers the flow coupling problem between the nacelle and the wing, resulting in that it cannot achieve good compatibility between the nacelle inlet performance and the overall aerodynamic characteristics.

[0004] In summary, the existing technology has the following specific technical problems: the traditional nacelle inlet lip design is difficult to achieve low additional resistance, high total pressure recovery coefficient and high-quality inlet under the compact arrangement required by the distributed propulsion system, so as to meet the comprehensive aerodynamic performance requirements of the wing-integrated distributed electric propulsion system. SUMMARY

[0005] Therefore, the application provides a special-shaped air inlet lip for an on-wing integrated distributed propulsion nacelle unit, aiming to solve the nacelle air inlet quality problem of the distributed propulsion nacelle unit under the condition of compact on-wing integration, reduce the nacelle additional resistance, guarantee a high air inlet total pressure recovery coefficient and provide a uniform and stable high-quality air inlet for a ducted fan power device on the basis of fully considering the wing-distributed propulsion nacelle coupling flow characteristics.

[0006] In order to achieve the above-mentioned purpose, the application adopts the following technical scheme: In a first aspect, the application provides a special-shaped air inlet lip for an on-wing integrated distributed propulsion nacelle unit, which is located at the starting part of an air inlet section 1 and is jointly enclosed by an upper lip 11, a lower lip 13 and left and right lips 12 connecting the two; The inner shape surface of the upper lip 11 is in a circular arc shape; The inner shape surface of the lower lip 13 is in a straight line shape, and is configured to be smoothly connected with the upper surface of a wing 8; The inner shape surface of the left and right lips 12 is a curved surface with a sweep feature in the fan axial direction, and the inner shape surface of the lower half part is in a converging shape, wherein the converging shape refers to that the concave surface of the part of the curved surface faces the main flow direction of the airflow in the air inlet; The special-shaped air inlet lip and a ducted fan inlet cross section 14 form an air inlet, the length of the air inlet is defined as the axial distance from the leading edge of the upper lip 11 to the ducted fan inlet cross section 14, and the length of the air inlet is not greater than the diameter D of the ducted fan.

[0007] In a specific implementable scheme, the length of the air inlet is 0.4D to 0.8D.

[0008] In a specific implementable scheme, for a ducted fan with a diameter D not less than 300 mm, the curvature radius of the circular arc inner shape surface of the upper lip 11 is 0.6D to 0.8D.

[0009] In a specific implementable scheme, the air inlet includes a first flow straightening area 16 and a second flow straightening area 17 arranged in sequence along the airflow direction, the first flow straightening area 16 is located between the lip leading edge and a transition cross section 15, and the second flow straightening area 17 is located between the transition cross section 15 and the ducted fan inlet cross section 14.

[0010] In a specific implementable scheme, the profile of the first flow straightening area 16 is configured to complete the transition from the special-shaped air inlet lip cross section to a circular cross section and realize air inlet diffusing.

[0011] In a specific implementable scheme, the profile of the second flow straightening area 17 is configured to further homogenize the airflow from the first flow straightening area 16.

[0012] In a second aspect, the present invention provides an aircraft including a wing 8 and at least one distributed propulsion nacelle unit 9, the distributed propulsion nacelle unit 9 being disposed on the upper surface of the wing 8, and the air intake of the distributed propulsion nacelle unit 9 adopting the irregularly shaped air intake lip as described in the first aspect of the present invention.

[0013] Compared with existing technologies, the irregularly shaped inlet lip for an on-wing integrated distributed propulsion nacelle unit described in this invention effectively solves the technical challenge of achieving efficient aerodynamic transition under compact on-wing integrated layout conditions by adopting an irregularly shaped lip combination with a rounded upper surface, a square lower surface, and inwardly tapering sidewalls, along with an inlet design with a low length-to-diameter ratio. While meeting the requirements of an extremely compact layout, this invention achieves better results in reducing nacelle-related drag and ensuring a high total pressure recovery coefficient and a uniform inlet airflow field, providing high-quality airflow assurance for distributed electric propulsion systems, and has the following beneficial effects: 1. This invention achieves an aerodynamic transition from an irregular shape to a circular shape by strictly controlling the length of the air intake within a low length-to-diameter ratio range of 0.4D to 0.8D, and matching it with an upper lip arc and a lower lip that blends with the wing. This design suppresses the growth of the boundary layer in the flow channel within the lip, reduces total pressure loss, and enables high-quality air intake with a total pressure recovery coefficient of not less than 0.9, as described in the specific embodiment, directly ensuring the efficiency and thrust of the power unit.

[0014] 2. The inward-curving surface design of the lower half of the left and right side lips adopted in this invention can actively guide the boundary layer airflow on the sidewalls towards the center of the flow channel. This, combined with the upper round and lower inlet shape, effectively avoids the formation of low-speed separation zones (or "triangular zones") at the four corners of the inlet lips. This effect optimizes the rectification effect and improves the uniformity of airflow, which is key to reducing the additional drag of the nacelle and achieving a balance between airflow quality and low drag in a compact layout. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0016] Figure 1 This is a longitudinal cross-sectional view of the wing-integrated distributed propulsion nacelle unit described in this invention in its installed state.

[0017] Figure 2 This is a schematic diagram of the installation and arrangement of the wing-integrated distributed propulsion nacelle unit described in this invention on an aircraft.

[0018] Figure 3 This is an isometric schematic diagram of the irregularly shaped air intake lip described in this invention.

[0019] Figure 4 This is a front view of the irregularly shaped air intake lip described in this invention.

[0020] Figure 5 This is a side view of the irregularly shaped air intake lip described in this invention.

[0021] Explanation of reference numerals in the attached drawings: 1 is the air intake section, 2 is the ducted fan casing section, 3 is the exhaust section, 4 is the exhaust rectification section, 5 is the ducted fan rotor, 6 is the ducted fan stator, 7 is the ducted fan center body, 8 is the wing, 9 is the distributed propulsion nacelle unit, 10 is the fuselage, 11 is the upper lip, 12 is the left and right lips, 13 is the lower lip, 14 is the ducted fan inlet section, 15 is the transition section (between the first and second rectification sections), 16 is the first rectification section, 17 is the second rectification section, and 18 is the nacelle outer surface. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The present invention discloses an irregularly shaped air intake lip for an on-wing integrated distributed propulsion nacelle unit, applicable to an on-wing integrated distributed propulsion layout aircraft, and is a key aerodynamic component of the distributed propulsion nacelle unit. The external contour of the distributed propulsion nacelle unit 9 is defined by its nacelle outer surface 18, which is a smoothly curved surface with aerodynamic optimization design, used to meet the internal flow channel layout while smoothly connecting with the upper surface of the wing 8 and the outer shape of adjacent nacelle units, so as to minimize the external aerodynamic drag of the entire aircraft.

[0024] like Figure 2 As shown, several distributed propulsion nacelle units 9 with the aforementioned irregularly shaped air intake lips are closely juxtaposed (closely arranged side by side) along the span of the wing 8; the bottom of each distributed propulsion nacelle unit is integrated with the wing 8; the sidewalls of the distributed propulsion nacelle units near the fuselage 10 are integrated with the fuselage 10; the integration refers to forming an integrated connection with a continuous aerodynamic shape to ensure a smooth transition of flow between the two, which can be achieved through conventional structural connection methods in the art, such as: connecting through a common fairing structure, or fixing through a bracket and then covering with a fairing skin to form a smooth surface; like Figure 1As shown, the distributed propulsion nacelle unit is divided into the following sections along the airflow direction (axial direction): intake section 1, ducted fan casing section 2, exhaust section 3, and exhaust post-rectifier section 4; the ducted fan (including ducted fan rotor 5, ducted fan stator 6, and ducted fan center body 7) is installed inside the ducted fan casing section 2; the ducted fan is the core power component that generates thrust, and the ducted fan casing section 2 is an outer shell structure used to house, position, and protect the ducted fan, and to assist in airflow control; Understandably, although there are slight differences in the outer flow surface between the distributed propulsion nacelle units extending outward (the side furthest from the fuselage 10) and the innermost (the side closest to the fuselage 10) along the wing 8, the inner flow surface of all distributed propulsion nacelle units, including the intake section 1, the ducted fan casing section 2, and the exhaust section 3, should maintain structural consistency.

[0025] Inlet section 1 is the structural section at the foremost point along the axial direction of the distributed propulsion nacelle unit. The interior of inlet section 1 is a dedicated airflow channel, also known as the air intake duct. The air intake duct refers to the internal channel enclosed by the wall through which the airflow flows from the air intake duct lip to the duct fan inlet section 14. The irregularly shaped air intake lip described in this invention is located at the beginning of the air intake, such as... Figure 5 As shown, the air intake design combines an irregularly shaped lip with a low length-to-diameter ratio, and is formed by the upper lip 11, the lower lip 13, and the left and right lips 12; as Figure 3 , Figure 4 , Figure 5 As shown, specifically: Upper lip 11: Located at the top of the air intake, its leading edge is arc-shaped. For ducted fans with a diameter D of not less than 300 mm, the radius of curvature of this arc is designed to range from 0.6D to 0.8D. The arc-shaped upper lip 11 smoothly guides the free flow from above the distributed propulsion nacelle unit and is the starting part of the transition of the air intake's internal profile from the irregular inlet cross-section to the circular ducted fan inlet cross-section 14. Its function is to avoid the formation of a large flow separation zone at the top of the air intake, ensuring the air intake quality in this area.

[0026] Lower lip 13: Located at the bottom of the air intake, its leading edge is straight. When the distributed propulsion nacelle unit is integrated into the wing, the inner surface of the lower lip of the air intake of the distributed propulsion nacelle unit smoothly merges with the upper surface of the wing 8. This design achieves seamless aerodynamic integration between the nacelle and the wing, minimizing the additional drag and weight caused by adding a separate lower lip structure, and meeting the requirements of the distributed propulsion system for a compact integrated layout.

[0027] Left and right lips 12: Located on the left and right sides of the inlet, respectively, connecting the upper lip 11 and the lower lip 13. Their leading edges are curved surfaces with a sweeping characteristic in the fan axis. In particular, the leading edges of the lower half of the left and right lips 12 adopt an inward-curving design, that is, the concave surface of this part of the curved surface faces the mainstream direction of the airflow in the inlet. The swept-out design adapts to the narrow lateral space constraints when multiple distributed propulsion nacelle units are placed side by side. The inward-curving design is used to actively regulate the boundary layer development on this leading edge, guiding the airflow near the sidewall to fill the central area of ​​the flow channel more effectively, thereby reducing the total pressure loss on both sides of the ducted fan inlet section 14. It also works in conjunction with the upper and lower lips to efficiently complete the aerodynamic transition from the irregular inlet to the ducted fan inlet section 14, avoiding the formation of large low-speed separation zones (or "triangular zones") at the four corners of the lips during the transition from the irregular inlet to the circular channel.

[0028] To ensure aerodynamic performance, the length of the intake duct is strictly controlled. The intake duct length is defined as the axial distance from the leading edge of the upper lip 11 to the inlet section 14 of the ducted fan, and it is not greater than the diameter D of the ducted fan. In a preferred embodiment, this length is further limited to the range of 0.4D to 0.8D.

[0029] Within such a limited axial length, for efficient tissue flow, such as Figure 5 As shown, the air intake is functionally divided into two continuous areas: front and rear. The first rectification zone 16, starting from the leading edge of the lip and extending to the transition section 15, completes the square-to-round transition of the leading edge of the intake duct and the intake diffusion process. The second rectification zone 17, between the transition section 15 and the ducted fan inlet section 14, has the main function of further smoothing and homogenizing the intake airflow field to ensure that the airflow enters the ducted fan in a uniform and stable state.

[0030] When implementing this invention, the following design process can be followed: First, determine the external envelope dimensions of the distributed propulsion nacelle unit based on the dimensions of the ducted fan, and clarify its maximum structural width and height; Secondly, based on the flow requirements of the ducted fan, the nacelle lip-fan flow matching design is carried out through engineering estimation methods to determine the lip inlet cross-sectional area and ensure that the inlet flow coefficient is greater than 0.8. For ducted fans with a diameter of not less than 300 mm, the inlet length should be controlled within the range of 0.4D-0.8D, and an arc with a radius of 0.6D-0.8D should be used as the upper lip control line. When the inlet length is less than 0.4D, the airflow uniformity of the inlet section 14 of the ducted fan is less than 85%, which does not meet the design requirements. When the inlet length is greater than 0.8D, the boundary layer thickness at the leading edge of the inlet exceeds 0.03D, which will cause the total pressure recovery coefficient to be less than 0.9, which also does not meet the design requirements. Considering the suction effect of the ducted fan on the boundary layer of the upper surface of the wing, an inward-curving design is adopted in the lower half of the left and right lips (i.e. the concave direction of the lip curve is consistent with the main flow direction of the airflow inside the lip). By adjusting the boundary layer distribution at the leading edge of the lip, this design can actively guide the airflow near the sidewall to fill the center of the channel, thereby suppressing the boundary layer thickening, optimizing the flow field, and ensuring that the total pressure recovery coefficient of the ducted fan inlet section 14 is not less than 0.9. Finally, based on the results of numerical simulation analysis, the design of the irregular air intake lip is iteratively optimized. Taking into account the total pressure recovery coefficient, total pressure distortion index and structural manufacturing cost, the optimal solution that meets the overall design requirements of the aircraft and the performance requirements of the engine is selected.

[0031] It should be noted that the suboptimal design, in contrast, is to use an extended air intake (more than 1D in length). While this design provides a longer flow recovery space and improves airflow uniformity, it leads to a thicker boundary layer at the leading edge of the air intake, which adversely affects the flow velocity at the ducted fan inlet section 14. Ultimately, this results in a decrease in the total pressure recovery coefficient, which is detrimental to the range performance of the electric aircraft.

[0032] The performance indicators of this solution can be tested in a low-speed wind tunnel (such as an open-type recirculation wind tunnel). The testing steps are as follows: 1. Fix the lip and the distributed propulsion nacelle unit model (including the ducted fan simulator) to the wind tunnel test section, and adjust the model attitude so that the angle between the lip reference plane and the wind tunnel airflow direction is the target angle of attack (-2° to 8°). 2. Adjust the wind tunnel speed to achieve a Mach number of 0.3-0.6 at the inlet lip, and control the wind tunnel static pressure to the standard sea-level atmospheric pressure condition of 101.3 kPa; 3. Measure the total pressure and static pressure at the inlet section 14 of the ducted fan using a pressure sensor, and calculate the total pressure recovery coefficient; measure the intake flow rate using a flow sensor, and calculate the flow coefficient based on the lip intake cross-sectional area.

[0033] The various embodiments described in this specification are presented in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An irregularly shaped air inlet lip for an on-wing integrated distributed propulsion nacelle unit, characterized in that, The irregularly shaped air intake lip is located at the beginning of the air intake section (1) and is formed by the upper lip (11), the lower lip (13) and the left and right lip (12) connecting the two. The inner surface of the upper lip (11) is arc-shaped; The inner surface of the lower lip (13) is straight, and its inner surface is constructed to be smoothly integrated with the upper surface of the wing (8). The inner surface of the left and right lips (12) is a curved surface with a sweeping feature in the fan axis, and the inner surface of the lower half of it is concave. The concave shape means that the concave surface of this part of the curved surface faces the mainstream direction of the airflow in the intake duct. An air intake duct is formed between the shaped air intake lip and the duct fan inlet section (14). The length of the air intake duct is defined as the axial distance from the leading edge of the upper lip (11) to the duct fan inlet section (14), and the length of the air intake duct is not greater than the diameter D of the duct fan.

2. The irregularly shaped air intake lip according to claim 1, characterized in that, The length of the air intake is 0.4D to 0.8D.

3. The irregularly shaped air intake lip according to claim 1, characterized in that, For a ducted fan with a diameter D of not less than 300 mm, the radius of curvature of the arc-shaped inner surface of the upper lip (11) is 0.6D to 0.8D.

4. The irregularly shaped air intake lip according to claim 1, characterized in that, The air intake includes a first rectification zone (16) and a second rectification zone (17) arranged sequentially along the airflow direction. The first rectification zone (16) is located between the leading edge of the lip and the transition section (15), and the second rectification zone (17) is located between the transition section (15) and the duct fan inlet section (14).

5. The irregularly shaped air intake lip according to claim 4, characterized in that, The profile of the first rectifier region (16) is configured to complete the transition from the irregular intake lip section to the circular section and achieve intake diffusion.

6. The irregularly shaped air intake lip according to claim 4, characterized in that, The profile of the second rectification zone (17) is configured to further homogenize the airflow from the first rectification zone (16).

7. An aircraft, characterized in that, It includes a wing (8) and at least one distributed propulsion nacelle unit (9), the distributed propulsion nacelle unit (9) being disposed on the upper surface of the wing (8), and the air intake of the distributed propulsion nacelle unit (9) adopting an irregularly shaped air intake lip as described in any one of claims 1 to 6.

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