An intake system for a radial intake engine

Abstract

This invention relates to the field of air intake design and discloses an air intake system for a radial intake engine, including an air intake duct, an intake volute, and an engine intake casing. The air intake duct, along the airflow direction, sequentially comprises an intake duct lip, a transition section, an expansion section, and a 90° bend. The outlet of the 90° bend connects to the inlet of the intake volute. The transition section first contracts and then expands to reduce intake losses. The 90° bend in the air intake duct, in conjunction with the engine intake casing, can convert the airflow from radial to axial intake. The intake volute redistributes the airflow into circumferential intake, improving the intake quality of the radial intake engine and ensuring its aerodynamic performance and efficient, stable operation.

Description

Technical Field

[0001] This invention relates to the field of air intake design technology, and more specifically, to an air intake system for a radial intake engine. Background Technology

[0002] The performance of the intake system directly affects the operating characteristics of the engine. If the performance of the intake system is too poor, it may cause engine surge or even engine stall.

[0003] When a medium-to-high altitude long-endurance UAV uses an axial-intake engine, the conventional S-curve air intake can well meet the engine's air intake requirements. However, when it uses a radial-intake engine, the outlet airflow direction of the conventional S-curve air intake does not match the engine's air intake direction, which reduces the air supply quality of the air intake and consequently leads to a decrease in the engine's aerodynamic performance, and may even affect the normal operation of the engine.

[0004] In summary, how to provide an intake system suitable for radial intake engines is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an intake system for a radial intake engine, which utilizes a 90° bend in conjunction with the engine intake casing to achieve axial intake of the incoming flow, and utilizes the intake volute to distribute the airflow into full circumferential intake, thereby improving the intake quality of the radial intake engine and ensuring the aerodynamic performance and efficient and stable operation of the engine.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] An intake system for a radial intake engine includes an intake duct, an intake volute, and an engine intake casing. The intake duct is provided with an intake duct lip, a transition section, an expansion section, and a 90° bend in sequence along the airflow direction. The outlet of the 90° bend is connected to the inlet of the intake volute. The transition section first contracts and then expands to reduce the intake loss of the intake duct.

[0008] Preferably, the thickness of the inner lip of the air intake lip is greater than the thickness of the outer lip of the air intake lip.

[0009] Preferably, the cross-section of the inner lip and the cross-section of the outer lip are both 1 / 4 ellipse, and the short side of the inner lip is adjacent to the long side of the outer lip.

[0010] Preferably, the ratio of the length of the transition section to the equivalent diameter of the inlet section of the air intake is 0.5-1.5.

[0011] Preferably, the radius R of the 90° bend bEquivalent diameter D of the starting point section of the 90° bend b The ratio R b / D b ≥1.3.

[0012] Preferably, the intake volute has a baffle at one end relatively far from the intake duct, the baffle being used to block the airflow to prevent the airflow from forming a vortex structure under a large sideslip angle.

[0013] Preferably, the partition extends to the interface between the intake volute and the engine intake casing.

[0014] After the airflow enters the intake duct, the airflow direction undergoes a first 90° turn at the 90° bend of the intake duct, and then enters the engine intake casing through the intake volute. The airflow direction undergoes a second 90° turn inside the engine intake casing and is redistributed as full-circumferential intake.

[0015] The intake system of the radial intake engine provided by this invention has a 90° bend in the intake duct that can work with the engine intake casing to change the airflow from radial intake to axial intake. The intake volute redistributes the airflow to full circumferential intake, which improves the intake quality of the radial intake engine and ensures the aerodynamic performance and efficient and stable operation of the engine. Attached Figure Description

[0016] 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.

[0017] Figure 1 This is a cross-sectional schematic diagram of the intake system of the radial intake engine provided by the present invention in the main viewing direction;

[0018] Figure 2 for Figure 1 Front view diagram;

[0019] Figure 3 for Figure 1 A top-down view;

[0020] Figure 4 for Figure 1 A side view diagram;

[0021] Figure 5 This is a magnified view of a portion of region A.

[0022] Figure 6 This is a three-dimensional flow field diagram of the intake system of a radial intake engine.

[0023] Figures 1-6 middle:

[0024] 1 is the air intake duct, 11 is the air intake duct lip, 12 is the transition section, 2 is the air intake volute, 21 is the baffle, 3 is the engine air intake casing, R b The radius of the 90° bend, D b The equivalent diameter of the starting section of the 90° bend. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0026] The core of this invention is to provide an intake system for a radial intake engine. It utilizes a 90° bend in conjunction with the engine intake casing to achieve axial air intake of the incoming flow, and uses the intake volute to distribute the airflow into full circumferential air intake, thereby improving the intake quality of the radial intake engine and ensuring the engine's aerodynamic performance and efficient and stable operation.

[0027] The intake system of the radial intake engine provided by the present invention includes an intake duct 1, an intake volute 2, and an engine intake casing 3. The intake duct 1 is provided with an intake duct lip 11, a transition section 12, an expansion section, and a 90° bend in sequence along the airflow direction. The outlet of the 90° bend is connected to the inlet of the intake volute 2. The transition section 12 first contracts and then expands to reduce the intake loss of the intake duct 1.

[0028] Among them, the engine intake casing 3 is provided with several guide plates evenly arranged along the circumference to guide the airflow. The structure, shape and size of the engine intake casing 3 are designed and determined by the engine manufacturer and manufactured and provided by the engine manufacturer.

[0029] The structure, shape, and size of the intake duct 1 and the intake volute 2 are determined by design calculation based on design parameters such as the total pressure recovery coefficient of the intake system and factors such as the size of the engine intake casing 3.

[0030] The shape of the inlet cross section of the air intake 1 is not limited and can be set to any regular or irregular shape such as circle, rectangle, semicircle, ellipse, triangle, etc. In order to better integrate the air intake system with the fuselage shape and reduce aerodynamic drag, the air intake is usually set to a semicircle.

[0031] The inlet area A1 of intake duct 1 is determined based on the design flow rate W of the matched engine. a,cThe design calculations are performed based on the design operating conditions and the total pressure recovery coefficient requirements under those conditions. Assuming the aircraft's cruise Mach number is Ma0 and the total pressure recovery coefficient is σ, then A1 = (εσW) a,c ) / [242q(Ma0)φ];

[0032] Where q(M) is the flow function expressed in terms of Mach number, and q(Ma0) is the value of q(M) when M = Ma0;

[0033] The flow coefficient φ = [ε(Ma1)V1] / [ε(Ma0)V0], where V0 is the cruising speed of the aircraft, V1 is the airflow velocity at the inlet section of the air intake, Ma1 is the Mach number of the incoming flow at the inlet section of the air intake, ε(M) is the aerodynamic function expressed in terms of Mach number, and ε(Ma1) and ε(Ma0) are the values ​​of ε(M) when M = Ma1 and M = Ma0, respectively.

[0034] The degree of curvature of the centerline of the intake duct 1 affects the deflection of the airflow within the channel. Therefore, the shape of the centerline of the intake duct 1 directly affects its aerodynamic performance. In order to reduce the flow loss caused by airflow deflection, the inner bend of the 90° bend should be made gentle to avoid factors such as channel expansion and curvature that exacerbate the flow separation at the intake inlet.

[0035] An air intake lip 11 is provided at the inlet of the air intake duct 1. The air intake lip 11 is used to reduce the distortion of the airflow field caused by ground vortices, fuselage boundary layer, etc. According to the relative thickness relationship between the inner lip and the outer lip, the air intake lip 11 can adopt an inner and outer equal thickness design, an inner thick and outer thin design, or an inner thin and outer thick design.

[0036] Preferably, the thickness of the inner lip of the intake duct lip 11 can be set to be greater than the thickness of the outer lip of the intake duct lip 11. The intake duct lip design with the inner thickness and outer thickness can reduce the airflow deflection rate on the inner side of the lip under high flow conditions and suppress downstream flow separation.

[0037] Please refer to Figure 5 The cross-sections of the inner and outer lips of the intake duct lip 11 are both 1 / 4 ellipses, with the short side of the inner lip adjacent to the long side of the outer lip. The ratio of the major and minor axes of the two ellipses is usually set to 2-3. For example, in one embodiment, the ratio of the major and minor axes of the outer lip of the intake duct lip 11 is 2.

[0038] It should be noted that the ratio of the major and minor axes of the ellipse of the inner and outer lips is not limited to the range of 2-3, and can be adjusted according to factors such as the design conditions of the actual matching engine. For example, in one embodiment, the ratio of the major and minor axes of the ellipse of the inner lip of the intake duct lip 11 is 1.444.

[0039] Please refer to Figure 3 The transition section 12 first contracts and then expands. The flow channel area of ​​the front section of the transition section 12 continuously decreases, which can reduce the airflow deflection angle under large sideslip angle, increase the airflow separation angle of attack to delay airflow separation and improve the crosswind resistance, and facilitate the continuity of the wall curvature with the inlet lip 11.

[0040] The flow area of ​​the rear section of the transition section 12 is continuously increased to avoid uneven airflow in the intake duct 1 and to suppress flow separation at the intake duct inlet under large sideslip angle conditions.

[0041] Preferably, the ratio of the length of the transition section 12 to the equivalent diameter of the inlet section of the intake duct 1 can be set to 0.5-1.5. In one embodiment, the length of the transition section 12 is 150 mm, the ratio of the length of the contraction channel to the length of the expansion channel of the transition section 12 is 1:2, the contraction ratio of the contraction channel is 1.058, and the expansion ratio of the expansion channel is 1.058.

[0042] In order to guide the airflow from axial flow to radial flow, the air intake duct 1 is provided with a 90° bend. The shape of the 90° bend constrains the airflow direction and guides the airflow to change direction.

[0043] To suppress flow separation inside the flow channel, it is preferable to set the radius R of the 90° bend. b Equivalent diameter D of the starting section of the 90° bend b The ratio R b / D b ≥1.3, the specific value of which is determined with reference to factors such as the centerline shape of intake 1 and the diffusion ratio of intake 1.

[0044] For example, in one embodiment, the engine intake casing 3 is relatively large, resulting in a large diffusion ratio of the intake duct 1, approximately 2.18, and the curvature diameter of its 90° bend is greater than R. b / D b =1.39.

[0045] To ensure the continuity of the wall curvature between the transition section 12 and the 90° bend, an expansion section is provided between the transition section 12 and the 90° bend. The expansion is used to reduce the degree of curvature change of the centerline of the front section of the intake duct 1 and guide the airflow to turn more smoothly.

[0046] The expansion section is designed after the transition section 12 and the 90° bend are designed. Its length is determined based on the length of the intake duct 1, the length of the transition section 12 and the length of the 90° bend. The shape of the expansion section is designed to be smooth, continuous and streamlined.

[0047] The intake volute 2 connects the intake manifold 1 and the engine intake casing 3. The outlet of the intake volute 2 is connected to the inlet of the engine intake casing 3. Therefore, the shape and size of the outlet of the intake volute 2 are consistent with the shape and size of the outlet of the matching engine intake casing 3.

[0048] Since the intake volute 2 is mounted on the engine intake casing 3 via the power turbine shaft, the axial length of the intake volute 2 should not be too large and is limited by factors such as the engine compartment structure and engine disassembly and assembly requirements. The minimum radial dimension of the intake volute 2 is determined according to the principle of minimum outer envelope, while the maximum radial dimension is determined according to the engine compartment structure and disassembly and assembly requirements.

[0049] The profile of the intake volute 2 is designed to be smooth, continuous, and streamlined, and the total pressure loss and flow field distortion caused by the intake volute 2 should meet the engine performance requirements.

[0050] To suppress the formation of a high-pressure zone below the intake volute 2, the airflow velocity distribution characteristics inside the intake volute 2 can be obtained through numerical simulation calculations. The flow channel area in the region with a large airflow velocity can be increased to reduce the velocity of the airflow when it impacts the symmetrical plane, thereby alleviating the problem of directional migration of low-energy flow near the wall.

[0051] Due to the limited installation position of the intake volute 2, the airflow impact speed on the symmetrical surface is reduced by increasing the rear end surface area of ​​the intake volute 2.

[0052] It should be noted that, in order to integrate the air intake duct 1 and the air intake volute 2, numerical simulation calculations can be used to iteratively optimize the flow channel profile to obtain a more continuous and smooth flow channel profile.

[0053] Once the lengths and other dimensions of the intake duct 1 and the intake volute 2 are determined, the flow field characteristics such as pressure distribution and streamlines within the flow duct can be obtained through numerical simulation calculations, such as... Figure 6 The three-dimensional flow field diagram shown analyzes the above flow field characteristics, determines the starting point and separation zone of airflow separation, and uses quadratic curves and rule curves to optimize the curvature of the 90° bend profile of the intake duct and the inlet profile of the intake volute, so as to enhance the curvature continuity, make the flow channel profile of the intake system more continuous and smooth, and facilitate airflow turning.

[0054] Please refer to Figure 1 After the airflow flows into the intake duct 1, the airflow direction undergoes a first 90° turn at the 90° bend of the intake duct 1, and then enters the engine intake casing 3 through the intake volute 2. The airflow direction undergoes a second 90° turn within the engine intake casing 3 and is redistributed as full-circumferential intake.

[0055] In this embodiment, the 90° bend of the intake duct 1 can work with the engine intake casing 3 to change the airflow from radial intake to axial intake, and the intake volute 2 redistributes the airflow to full circumferential intake, which improves the intake quality of the radial intake engine and ensures the aerodynamic performance and efficient and stable operation of the engine.

[0056] Based on the above embodiments, the intake volute 2 can be provided with a baffle 21 at one end that is relatively far away from the intake duct 1. The baffle 21 is used to block the airflow so as to prevent the airflow from forming a vortex structure under a large sideslip angle.

[0057] Please refer to Figure 1 The baffle 21 is located directly below the intake volute 2 and is connected to the inner wall of the intake volute 2. The baffle 21 can prevent airflow from flowing from one side of the baffle 21 to the other side, thereby preventing the airflow from forming a vortex structure under a large sideslip angle.

[0058] Considering the need for protection against sand and ice, a protective cover is usually installed around the engine intake casing 3 in the circumferential direction. The protective cover will affect the position and connection method of the partition 21. At this time, the height of the partition 21 is not fixed, and its specific height can be determined according to the actual structure and design conditions of the engine intake casing 3 and the intake volute 2.

[0059] Preferably, the baffle 21 can be provided to extend to the interface between the intake volute 2 and the engine intake casing 3. In this case, the baffle 21 can completely separate the airflow on both sides, effectively preventing the formation of a vortex structure when the airflow flows in the circumferential direction, and greatly reducing the flow loss caused by the vortex.

[0060] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0061] The intake system of the radial intake engine provided by this invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. An air intake system for a radial engine, characterized in that, The application relates to an air inlet channel (1), an air inlet volute (2) and an engine air inlet casing (3), wherein the air inlet channel (1) is sequentially provided with an air inlet channel lip (11), a transition section (12), an expansion section and a 90-degree elbow along the airflow direction, the outlet of the 90-degree elbow is connected with the inlet of the air inlet volute (2), the transition section (12) is first contracted and then expanded, so that the air inlet loss of the air inlet channel (1) is reduced; the thickness of the inner side lip of the air inlet channel lip (11) is greater than that of the outer side lip of the air inlet channel lip (11); the cross section of the inner side lip and the cross section of the outer side lip are both 1 / 4 ellipse, the short side of the inner side lip is adjacent to the long side of the outer side lip; the ratio of the length of the transition section (12) to the equivalent diameter of the inlet section of the air inlet channel (1) is 0.5-1.5; the ratio Rb / Db of the radius Rb of the 90-degree elbow to the equivalent diameter Db of the starting point section of the 90-degree elbow is greater than or equal to 1.3; the air inlet volute (2) is provided with a partition plate (21) at the end far from the air inlet channel (1), the partition plate (21) is used for blocking the airflow, so that vortex structure is avoided in the large side slip angle state.

2. The intake system of a radial engine according to claim 1, characterized in that, the partition plate (21) extends to the joint surface of the air inlet volute (2) and the engine air inlet casing (3).

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