A non-centrosymmetric, axisymmetric, lobed engine primary nozzle and design method

Abstract

The application provides a non-central axis symmetrical wave lobe engine main nozzle and a design method, which comprises a wave lobe curved surface (1) and an expanding cylindrical curved surface (2), the wave lobe curved surface (1) is arranged on the outer surface of the expanding cylindrical curved surface (2) and protrudes towards the central axis (3) of the expanding cylindrical curved surface (2); the area ratio of a wave lobe outlet (8) to a wave lobe inlet (9) is between 0.12 and 0.25; the application can solve the problem of local over-temperature of a power cabin, the additional loss of engine power caused by the application is 15%-20% of that of a traditional treatment method, and the manufacturing process is simple, time-saving, low in cost and convenient for field installation.

Description

Technical Field

[0001] This invention belongs to the field of aerodynamics and aerodynamic design, and specifically relates to a non-central axisymmetric lobe-type engine main nozzle and its design method. Background Technology

[0002] Most modern helicopters employ an "ejector-type" engine compartment ventilation and cooling system. This system utilizes the high-temperature exhaust gas from the engine to create a localized low-pressure zone at the ejector gap within the engine compartment. This zone carries the hot air from the engine compartment into the outside atmosphere, while cooler air from the outside environment enters the engine compartment through specially designed vents, creating a loop of hot and cold air to achieve ventilation and cooling. However, due to the asymmetrical arrangement of engine components and piping, and limitations imposed by the engine compartment platform, the airflow distribution within the engine compartment is uneven. This results in some areas having temperatures exceeding the limits while others are below them with significant temperature margins. This problem is particularly pronounced for high-heat-generating, high-power engines with high ventilation and cooling requirements.

[0003] Conventional methods for addressing engine compartment overheating typically involve indiscriminately increasing overall ventilation and heat dissipation, thereby increasing engine exhaust kinetic energy and lowering the overall temperature within the compartment. This leads to even lower temperatures in previously unaffected low-temperature areas. However, the greater the loss of exhaust kinetic energy, the greater the engine power loss, potentially even causing insufficient payload capacity for the helicopter. A non-centrally axisymmetric engine main nozzle, on the other hand, can only locally alter the engine exhaust velocity, significantly reducing the loss of exhaust kinetic energy, and specifically enhancing ventilation and heat dissipation in high-temperature areas of the engine compartment, thus resolving the overheating problem. Summary of the Invention

[0004] This invention provides a non-central axisymmetric lobe-type engine main nozzle and its design method. Targeting local overheating areas in the engine compartment, a non-central axisymmetric lobe-type main nozzle is formed through a special pleated curved surface configuration design. This achieves directional and positional ventilation and heat dissipation capabilities with less exhaust kinetic energy consumption, solves the overheating problem in the engine compartment, and improves the engine's operating environment.

[0005] The first aspect of this invention provides a design method for a non-central axisymmetric lobe-type engine main nozzle. The lobe-type engine main nozzle includes: a lobe surface 1 and an expanding quasi-cylindrical surface 2. The lobe surface 1 is disposed on the outer surface of the expanding quasi-cylindrical surface 2 and protrudes towards the central axis 3 of the expanding quasi-cylindrical surface 2. The ratio of the area of ​​the lobe outlet 8 to the area of ​​the lobe inlet 9 is between 0.12 and 0.25. The method includes:

[0006] Step S1: Calculate and analyze the flow field inside the helicopter engine compartment under typical operating conditions, including both fault and non-fault states, using numerical simulation methods. Identify at least one local overheating region where the temperature inside the helicopter engine compartment exceeds the limit, and obtain the flow field characteristics of each local overheating region. Typical operating conditions include: helicopter cruise flight, hovering with ground effect, hovering without ground effect, near-ground maneuvering, takeoff, and landing. Flow field characteristics include: temperature field and flow field distribution patterns.

[0007] Step S2: Based on the location of each local overheated region on the helicopter power nacelle, determine the installation position of the lobe surface 1 on the expanded cylindrical surface 2, so that the orientation of the lobe surface 1 on the circumference corresponds to the orientation of the local overheated region on the circumference; based on the flow field characteristics of each local overheated region, obtain the total air velocity required to reduce the temperature of each local overheated region to within the limit value; calculate the dynamic pressure increment required at the outlet of the lobe engine main nozzle based on the total air velocity and the air dynamic pressure calculation formula; calculate the area of ​​each lobe outlet 8 based on the dynamic pressure increment at the outlet of the lobe engine main nozzle and the area of ​​the engine exhaust port.

[0008] Step S3: Calculate the area of ​​the lobe entrance 9 based on the area of ​​the lobe exit 8.

[0009] Optionally, the lobe surface 1 achieves a smooth transition with the expanded cylindrical surface 2 by rounding the corners.

[0010] Optionally, the fillet radius is between 10mm and 25mm.

[0011] Optionally, the inlet diameter of the expanding cylindrical surface 2 is smaller than the outlet diameter, and the outward expansion angle 5 is between 2.5° and 7.5°.

[0012] Optionally, the plane containing the beam exit 8 is perpendicular to the central axis 3.

[0013] Optionally, the inner expansion angle 4 of the lobe surface 1 convex toward the central axis 3 is between 35° and 45°, and the ratio of the inner expansion angle 4 to the outer expansion angle 5 is between 5 and 20.

[0014] Optionally, the beam exit 8 is U-shaped, with the ratio of U-shape depth to width between 8 and 10.

[0015] Optionally, the plane on which the main nozzle 14 of the lobed engine is located is the same as the plane on which the lobed outlet 8 is located, and the ratio of the area of ​​the main nozzle outlet 14 to the area of ​​the inlet 13 is between 1 and 1.25.

[0016] Optionally, after step S3, the method further includes:

[0017] Step S4: Based on the designed lobe-type engine main nozzle, use numerical simulation to calculate and analyze the flow field inside the helicopter engine compartment under typical operating conditions to determine whether the temperature inside the helicopter engine compartment does not exceed the limit; if not, increase the area of ​​the lobe outlet 9 until the temperature inside the helicopter engine compartment does not exceed the limit.

[0018] The second aspect of the present invention provides a lobe-type engine main nozzle, which is designed using the non-central axisymmetric lobe-type engine main nozzle design method as described in any one of the first aspects.

[0019] This invention provides a non-central axisymmetric lobe-shaped engine main nozzle and its design method. Targeting localized overheating areas within the engine compartment, a special pleated surface configuration is used to create a non-central axisymmetric lobe-shaped main nozzle. This achieves directional and localized improved ventilation and heat dissipation capabilities with minimal exhaust kinetic energy expenditure, resolving the overheating problem within the engine compartment and improving the engine's operating environment. Numerical simulations and helicopter flight tests both demonstrate that this invention can directionally solve the overheating problem in localized areas of the engine compartment, resulting in an additional engine power loss of only 15%–20% compared to traditional methods. Furthermore, the manufacturing process is simple, time-efficient, low-cost, and easy to install in the field. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the main nozzle of this application;

[0021] Figure 2 This is a side view of the lobe surface of this application;

[0022] Figure 3 This is a schematic diagram of the lobe exit point of this application;

[0023] Figure 4 This is a schematic diagram of the lobe surface entry point for this application;

[0024] Figure 5 This is a schematic diagram of a cylindrical surface of the type described in this application;

[0025] Explanation of reference numerals in the attached figures:

[0026] 1-Lobe surface; 2-Expanding cylindrical surface; 3-Central axis and direction; 4-Inner expansion angle; 5-Outer expansion angle; 6-Lobe exit height; 7-Lobe exit width; 8-Lobe exit; 9-Lobe exit; 10-Lobe central angle; 11-Lobe mounting surface; 12-Lobe exit lower boundary; 13-Main nozzle inlet; 14-Main nozzle outlet. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0028] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0029] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0031] like Figure 1-5 As shown, this invention mainly consists of two parts: a wavelobe surface 1 and an expanded cylindrical surface 2. Figure 1 The lobe surface bulges outwards along the central axis 3 and is composed of geometric features such as the lobe inlet 9, lobe outlet 8, lobe outlet height 6, lobe outlet height 7, inner expansion angle 4, outer expansion angle 5, and lobe central angle 10. This expanding quasi-cylindrical surface is cylindrical in shape overall, gradually increasing in size along the central axis according to the trend of the outer expansion angle 5. The number of lobe surfaces and the size of the lobe central angle 10 will be determined according to subsequent design methods. The connection between lobe surface 1, lobe mounting surface 11, and the expanding quasi-cylindrical surface 2 must ensure continuous curvature without abrupt changes.

[0032] The key points of this invention mainly consist of the following:

[0033] a) Lobe inlet and outlet: The ratio of the area of ​​lobe outlet 8 to the area of ​​lobe inlet 9 is between 0.12 and 0.25. The lobe inlet 9 and the lobe mounting surface 11 are transitioned by a rounded corner with a radius between 10mm and 25mm. The plane containing lobe outlet 8 is perpendicular to the central axis 3. See Figure 3 and Figure 4 ;

[0034] b) Inner and outer expansion angles: The inner expansion angle 4 is between 35° and 45°, and the outer expansion angle 5 is between 2.5° and 7.5°. The ratio of the inner expansion angle 4 to the outer expansion angle 5 is between 5 and 20. See [reference needed]. Figure 2 ;

[0035] c) Beam exit height and width: The ratio of beam exit height 6 to beam exit width 7 is between 8 and 10. The lower boundary 12 of beam exit 8 is a semi-circular arc with beam exit width 7 as its diameter. See Figure 3 ;

[0036] d) Expanding cylindrical surface: The cross-sectional area gradually increases along the central axis according to the trend of outward expansion angle 5. The profile curve must be the same as the profile curve of the lobe mounting surface 11, see Figure 2 and Figure 5 ;

[0037] e) Main nozzle exit and inlet: The plane where the main nozzle exit 14 is located is the same as the plane where the beam exit 8 is located. The ratio of the area of ​​the main nozzle exit 14 to the area of ​​the inlet 13 is between 1 and 1.25. See Figure 1 .

[0038] This invention provides a design method for a non-central axisymmetric lobe-type engine main nozzle, the method comprising the following steps:

[0039] Step S1: Use numerical simulation to calculate and analyze the flow field inside the helicopter engine compartment under typical operating conditions to reproduce the fault state; and combine the flow field characteristics inside the engine compartment under common operating conditions such as helicopter cruise flight, hovering with ground effect, hovering without ground effect, near-ground maneuvering, takeoff, and landing to determine the local area where the temperature exceeds the limit, and analyze the flow field characteristics such as the temperature field and flow field distribution law in this area.

[0040] Step S2: Based on the position determined in Step S1, determine the installation position of the lobe surface 1, aligning it with the local overheated region along the central axis 3. Based on the local flow field characteristics determined in Step S1, estimate the local air velocity required to reduce the temperature in this region to within the limit value. Calculate the required dynamic pressure increment at the main nozzle outlet using this velocity and the air dynamic pressure calculation formula. Based on the dynamic pressure increment at the main nozzle outlet and the engine exhaust port area, calculate the size of the lobe outlet 8 and its percentage within the total area of ​​the main nozzle outlet 14.

[0041] Step S3: Based on the area of ​​the lobe exit 8 obtained in Step S2, calculate the area of ​​the lobe inlet 9 and the size of the lobe central angle 10, and initially construct the lobe surface 1. The lobe surface 1 achieves a smooth transition with the lobe mounting surface 11 by rounding the corners. Using the curvature at the boundary of the lobe mounting surface 11 and the outer expansion angle 5 of the lobe surface as standards, and combined with the structural constraints of the engine main nozzle mounting interface, construct an expanding quasi-cylindrical surface 2. Create the boundary curves of the surface lobe mounting surface 11 and the expanding quasi-cylindrical surface 2 using the multi-section surface method, ensuring the curvature continuity at the surface connection, and finally forming a preliminary non-central axisymmetric lobe-type engine main nozzle surface shape.

[0042] Step S4: Based on the main nozzle surface shape determined in Step S3, use the same numerical simulation method as in Step S1 to calculate the flow field distribution inside the helicopter engine compartment under typical operating conditions, and analyze the theoretical effect of the design scheme. If the temperature inside the engine compartment reaches the design requirements, the design process ends.

[0043] Step S5: If the design requirements are not met, adjust the area of ​​the lobe outlet 8 corresponding to the overheated area according to the principle of proximity, and adaptively adjust the geometric features such as the area of ​​the lobe inlet 9, the lobe outlet height 6, the lobe outlet height 7, the inner expansion angle 4, the outer expansion angle 5, the lobe central angle 10, and the number of lobe surfaces; or add lobe surfaces near the already determined lobe surfaces according to the principle of proximity, and then adaptively adjust the geometric features such as the area of ​​the lobe outlet 8, the area of ​​the lobe inlet 9, the lobe outlet height 6, the lobe outlet height 7, the inner expansion angle 4, the outer expansion angle 5, the lobe central angle 10, and the number of lobe surfaces, and restart steps S2 to S4.

[0044] It is understandable that while adjusting the area of ​​the lobe exit 8, the geometric features such as the area of ​​the lobe inlet 9, the lobe exit height 6, the lobe exit height 7, the inner expansion angle 4, the outer expansion angle 5, the lobe central angle 10, and the number of lobe surfaces can also be adjusted adaptively.

[0045] The above description is merely a further embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope disclosed in the present invention, based on the technical solution and concept of the present invention, shall fall within the scope of protection of the present invention.

Claims

1. A design method for a non-central axisymmetric lobe-type engine main nozzle, characterized in that, The main nozzle of the lobe-type engine includes: a lobe surface (1) and an expanding cylindrical surface (2), wherein the lobe surface (1) is disposed on the outer surface of the expanding cylindrical surface (2) and protrudes toward the central axis (3) of the expanding cylindrical surface (2); the ratio of the area of ​​the lobe outlet (8) to the area of ​​the lobe inlet (9) is between 0.12 and 0.25; the method includes: Step S1: Calculate and analyze the flow field inside the helicopter engine compartment under typical operating conditions, including both fault and non-fault states, using numerical simulation methods. Identify at least one local overheating region where the temperature inside the helicopter engine compartment exceeds the limit, and obtain the flow field characteristics of each local overheating region. Typical operating conditions include: helicopter cruise flight, hovering with ground effect, hovering without ground effect, near-ground maneuvering, takeoff, and landing. Flow field characteristics include: temperature field and flow field distribution patterns. Step S2: Based on the location of each local overheated region on the helicopter power nacelle, determine the installation position of the lobe surface (1) on the expanded cylindrical surface (2), so that the orientation of the lobe surface (1) on the circumference corresponds to the orientation of the local overheated region on the circumference; based on the flow field characteristics of each local overheated region, obtain the total air velocity required to reduce the temperature of each local overheated region to within the limit value; calculate the dynamic pressure increment required at the outlet of the lobe engine main nozzle based on the total air velocity and the air dynamic pressure calculation formula; calculate the area of ​​each lobe outlet (8) based on the dynamic pressure increment at the outlet of the lobe engine main nozzle and the engine exhaust port area. Step S3: Calculate the area of ​​the lobe entrance (9) based on the area of ​​the lobe exit (8).

2. The method according to claim 1, characterized in that, The wave-shaped surface (1) achieves a smooth transition with the expanded cylindrical surface (2) by rounding the corners.

3. The method according to claim 2, characterized in that, The radius of the rounded corner is between 10mm and 25mm.

4. The method according to claim 1, characterized in that, The inlet diameter of the expansion-type cylindrical surface (2) is smaller than the outlet diameter, and the outer expansion angle (5) is between 2.5° and 7.5°.

5. The method according to claim 1, characterized in that, The plane where the beam exit (8) is located is perpendicular to the central axis (3).

6. The method according to claim 4, characterized in that, The inner expansion angle (4) of the wave lobe surface (1) convex toward the central axis (3) is between 35° and 45°, and the ratio of the inner expansion angle (4) to the outer expansion angle (5) is between 5 and 20.

7. The method according to claim 1, characterized in that, The beam exit (8) is U-shaped, and the ratio of the depth to the width of the U-shape is between 8 and 10.

8. The method according to claim 1, characterized in that, The plane where the main nozzle (14) of the lobed engine is located is the same as the plane where the lobed outlet (8) is located. The ratio of the area of ​​the main nozzle outlet (14) to the area of ​​the inlet (13) is between 1 and 1.

25.

9. The method according to claim 1, characterized in that, After step S3, the method further includes: Step S4: Based on the designed lobe-type engine main nozzle, use numerical simulation to calculate and analyze the flow field inside the helicopter engine compartment under typical operating conditions to determine whether the temperature inside the helicopter engine compartment does not exceed the limit; if not, increase the area of ​​the lobe outlet (9) until the temperature inside the helicopter engine compartment does not exceed the limit.

10. A lobe-type engine main nozzle, characterized in that, The main nozzle of the engine is designed using the non-central axisymmetric lobe-type design method as described in any one of claims 1-9.

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