A helicopter infrared suppressor fairing and a method for aerothermodynamic optimization thereof

Abstract

The present application belongs to the technical field of helicopter overall aerodynamic design, and particularly relates to a kind of helicopter infrared suppressor fairing and its gas-thermal optimization design method.The fairing includes: fairing body, louver inlet, square protective net inlet, two-stage exhaust pipe, first-stage mixed exhaust pipe;The front view of the fairing body is half of an ellipse cut along the long axis;The front part of the fairing body is provided with the louver inlet, and the louver plane shape is crescent-shaped;The front of the top of the fairing body is provided with the square protective net inlet;The rear of the top of the fairing body is provided with the elliptical two-stage exhaust pipe to further cool the high-temperature exhaust gas with the help of the downwash airflow of the rotor;The two-stage exhaust pipe is sleeved with the first-stage mixed exhaust pipe;The first-stage mixed exhaust pipe is connected with the transmitter outlet.The present application solves the problem that aerodynamic and thermal performance are difficult to be considered in the traditional design method, realizes the comprehensive optimization of the aerodynamic and thermal performance of the fairing, and forms the aerodynamic design scheme of the infrared suppressor fairing.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of overall aerodynamic design of helicopters, and particularly relates to a helicopter infrared suppressor fairing and a gas-thermal optimization design method thereof. BACKGROUND

[0002] The infrared suppressor is a key equipment for reducing the infrared target radiation characteristics of a helicopter and improving the stealth performance. The fairing, as an important component of the infrared suppressor, directly affects the overall performance of the infrared suppressor in terms of aerodynamic shape and thermal characteristics. The traditional fairing design method often separates the aerodynamic design and the thermal design, and it is difficult to comprehensively optimize the aerodynamic and thermal performance. The traditional fairing design method often focuses on the structural strength and thermal protection performance, but the optimization of the aerodynamic performance is insufficient, which leads to a large aerodynamic resistance of the fairing during flight or an adverse interference of the fairing shedding vortex on the tail surface, thereby affecting the overall performance of the helicopter and limiting the use of the infrared suppressor. SUMMARY

[0003] The application aims to provide a helicopter infrared suppressor fairing and a gas-thermal optimization design method thereof, and solve the problem that the aerodynamic and thermal performance cannot be considered in the traditional design method, so as to comprehensively optimize the aerodynamic and thermal performance of the fairing and form an aerodynamic design scheme of the infrared suppressor fairing.

[0004] TECHNICAL SCHEME

[0005] In a first aspect, a helicopter infrared suppressor fairing is provided, which comprises a fairing body, a louver inlet, a square protective net inlet, a secondary exhaust pipe and a primary mixed exhaust pipe.

[0006] The front view of the fairing body is a half of an ellipse cut along a long axis; the half of the ellipse is composed of two different upper 1 / 4 ellipse and lower 1 / 4 ellipse.

[0007] The front part of the fairing body is provided with the louver inlet, and the plane shape of the louver is in the shape of a crescent moon; the included angle between the plane of the louver and the longitudinal symmetry plane is 35°-40°; the louver blade is in the shape of an L, the included angle between the outer edge of the blade and the horizontal plane is 18°-20°, and the included angle between the inner edge of the blade and the horizontal plane is 45°-47°.

[0008] The top front part of the fairing body is provided with the square protective net inlet.

[0009] The top rear part of the fairing body is provided with an oval-shaped secondary exhaust pipe for further cooling of high-temperature exhaust gas by means of the downwash airflow of the rotor; the secondary exhaust pipe is sleeved with the primary mixed exhaust pipe; the primary mixed exhaust pipe is connected with the transmitter outlet; the included angle between the axis of the secondary exhaust pipe and the horizontal plane is 45°-50°; the gap between the secondary exhaust pipe and the primary mixed exhaust pipe is 40-45 mm, and the overlap amount of the secondary exhaust pipe and the primary mixed exhaust pipe is 50 mm-150 mm.

[0010] The rear part of the fairing body is designed with a streamlined tail cone, the shape of which is spliced by two parabolas, and the side surface is gradually transitioned from an ellipse to a hyperbola; a gap exists between the tail cone and the fuselage skin, which facilitates the discharge of gas in the fairing cabin of the infrared suppressor and the entry of external cold air, and reduces the temperature in the cabin; the length-height ratio γ of the tail cone is 1-1.5;

[0011] The airflow enters from the louver air inlet and the square protective net air inlet, and is discharged from the gap between the first-stage mixed exhaust pipe and the second-stage exhaust pipe through the high-speed airflow injection effect of the first-stage mixed exhaust pipe; the fairing body does not directly contact the first-stage mixed exhaust pipe, and the distance between the fairing body and the first-stage mixed exhaust pipe is maintained at 150-200 mm.

[0012] In the second aspect, a method for optimizing the aerothermodynamics of a fairing of an infrared suppressor of a helicopter is provided, comprising:

[0013] The leading edge of the fairing of the infrared suppressor is designed to be convex outward to increase the windward area, form a wind-breaking effect, and improve the air intake efficiency;

[0014] The trailing edge of the fairing is designed to be tapered to reduce the aerodynamic drag;

[0015] The side surface of the fairing is designed to be spliced by multiple curved surfaces, and the curvature of each curved surface is optimized according to the flow field distribution;

[0016] An internal airflow channel is designed between the fairing of the infrared suppressor and the first-stage mixed exhaust pipe, which is used to guide the cooling airflow into the first-stage mixed exhaust pipe for mixing;

[0017] A louver air inlet and a square protective net air inlet are designed on the fairing of the infrared suppressor, so that the airflow enters from the louver air inlet and the square protective net air inlet, and is discharged from the gap between the first-stage mixed exhaust pipe and the second-stage exhaust pipe through the high-speed airflow injection effect of the first-stage mixed exhaust pipe.

[0018] Further, the design method is implemented by the following ways:

[0019] According to the exhaust port of the helicopter engine and the internal structure size of the infrared suppressor, a parameterized model of the fairing of the infrared suppressor is established, and the parameters of the parameterized model include the major axis and the minor axis of the elliptical curve of the side surface of the fairing and the length-height ratio of the tail cone;

[0020] The optimization objective of the model is determined to be reducing the aerodynamic drag coefficient of the fairing, weakening the aerodynamic interference of the fairing on the tail plane, and reducing the surface temperature of the fairing and the average temperature of the tail exhaust;

[0021] Based on the internal and external flow fields and the parameterized model by the CFD method, a simulation analysis model is established which comprehensively considers the fuselage and the engine exhaust system.

[0022] The aerodynamic simulation calculation is carried out on the simulation analysis model by using a non-structural tetrahedral mesh, and the mesh is encrypted in the area where the curvature of the simulation analysis model geometry changes greatly and the flow field changes greatly, so as to improve the flow field capture accuracy; wherein, the momentum source method is used to simulate the rotor downwash flow field; the rotor downwash flow field is part of the outer flow field; the ROE flux difference splitting format is used for the spatial discretization of the simulation calculation, the Realizable model is used for the turbulence model used in the simulation calculation, and the DO model is used for the thermal radiation used in the simulation calculation; wherein, the outer flow field adopts the velocity inlet and pressure outlet boundary conditions, the engine exhaust port adopts the inner flow field flow inlet boundary, and the surface adopts the no-slip boundary;

[0023] Based on the aerodynamic simulation calculation results, including the flow field velocity and temperature field distribution, the aerodynamic and thermal characteristics of the infrared suppressor fairing are analyzed.

[0024] Further, the aerodynamic and thermal characteristics of the infrared suppressor fairing are analyzed, including:

[0025] From the optimization of the three-dimensional shape of the fairing side and trailing edge, the fairing rear body airflow is smoothed, the airflow separation is reduced, and the fairing outer contour is as small as possible to reduce the resistance and weaken the adverse interference on the tail aerodynamic surface;

[0026] From the aspect of improving the injection effect, the surface temperature of the infrared suppressor fairing is reduced, and the gap and overlap amount of the primary mixed exhaust pipe and the secondary exhaust pipe are optimized;

[0027] The influence of the shape of the infrared suppressor fairing on the aerodynamic performance and thermal characteristics is comprehensively considered, and the aerodynamic scheme of the infrared suppressor fairing is determined.

[0028] Beneficial effects:

[0029] The helicopter infrared suppressor fairing aerothermal optimization design method provided by the application can comprehensively optimize the aerodynamic and thermal performance of the infrared suppressor fairing, and the aerodynamic resistance of the whole machine is reduced by 5% after the optimization of the shape and internal passage of the fairing, the fuel consumption of the helicopter during cruising flight is reduced, and the range is increased; the aerodynamic efficiency of the tail plane is improved by 30%, which is beneficial to reducing the nose-down angle of the helicopter body attitude during flat flying at high speed; the surface temperature of the infrared suppressor fairing is reduced by 15℃, and the infrared stealth performance of the helicopter is improved. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The side view of the infrared suppressor fairing related to the application.

[0031] Figure 2 The front view of the infrared suppressor fairing related to the application. ​

[0032] Figure 3 The figure is a top view of the infrared suppressor fairing involved in the present application.

[0033] Figure 4 The figure is a schematic diagram of the interference of the infrared suppressor fairing involved in the present application with the tail surface.

[0034] Figure 5 The figure is a schematic diagram of the temperature field of the internal and external flow field of the infrared suppressor fairing involved in the present application. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the embodiments of the present application will be described in more detail below with reference to the drawings in the embodiments of the present application. In the drawings, the same or similar notations represent the same or similar elements or elements with the same or similar functions throughout. The described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation on the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. The embodiments of the present application will be described in detail below with reference to the drawings.

[0036] In the description of the present application, it should be understood that the terms "center", "axial", "vertical", "upper", "lower", "upper end", "bottom end", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the scope of protection of the present application.

[0037] The present application proposes a helicopter infrared suppressor fairing aerothermal optimization design method, which realizes control of the internal and external flow of the infrared suppressor fairing, reduces the aerodynamic resistance, weakens the aerodynamic interference on the tail surface, and can meet the requirements of the infrared suppressor for ejecting and mixing ambient cold air to reduce the exhaust temperature, shielding the high-temperature components of the exhaust system, and good integration with the overall shape of the fuselage.

[0038] Design principle of infrared suppressor fairing

[0039] The front edge of the infrared suppressor fairing is convex outward to increase the windward area, form a wind scooping effect, and improve the air intake efficiency; the rear edge of the fairing is tapered to reduce the aerodynamic resistance; the side surface of the fairing is spliced by multiple curved surfaces, and the curvature of each curved surface is optimized according to the flow field distribution to weaken the separation phenomenon of the airflow flowing on the surface of the fairing.

[0040] The internal airflow passage is formed between the infrared suppressor fairing and the first mixed exhaust pipe, which is used to guide the cooling airflow into the first mixed exhaust pipe for mixing, to reduce the exhaust temperature, and to pass through the inside of the fairing to reduce the surface temperature of the fairing. The airflow enters from the louver air inlet 1 and the square protective net air inlet 2, and is discharged from the gap between the first mixed exhaust pipe and the second exhaust pipe by the high-speed airflow ejection of the first mixed exhaust pipe.

[0041] Design scheme of the infrared suppressor fairing

[0042] The infrared suppressor fairing comprises a fairing body, a louver air inlet 1, a square protective net air inlet 2, a second exhaust pipe 3, and a first mixed exhaust pipe 5.

[0043] The front view of the fairing body is a half of an ellipse cut along the long axis, which can increase the gap between the first mixed exhaust pipe and the fairing, weaken the heat radiation of the high-temperature exhaust pipe to the fairing, reduce the airflow separation of the fairing, and reduce the vertical resistance of the fairing caused by the downwash of the rotor;

[0044] The front part of the fairing body is provided with a louver air inlet, and the plane shape of the louver is in the shape of a crescent. The louver can shield the high-temperature first mixed exhaust pipe and other components to reduce the infrared radiation characteristics. The oblique crescent-shaped air inlet can increase the windbreak effect and reduce the front flight air resistance.

[0045] The square protective net air inlet is arranged at the top front of the fairing body, which can directly use the airflow speed of the downwash of the rotor to fill the air in the cabin of the fairing, increase the air inlet flow in the hovering or low-speed flight state, reduce the temperature in the cabin of the fairing, and reduce the infrared radiation.

[0046] The second exhaust pipe in the shape of an ellipse is arranged at the top rear of the fairing body, which can further cool the high-temperature exhaust by means of the airflow of the downwash of the rotor. The first mixed exhaust pipe is sleeved in the second exhaust pipe, which can use the ejection effect of the gap between the second exhaust pipe and the first mixed exhaust pipe to inject the cold air into the high-temperature exhaust of the first mixed exhaust pipe for mixing, to reduce the temperature of the exhaust. The first mixed exhaust pipe is connected with the transmitter outlet.

[0047] The fairing body is designed with a streamlined tail cone 4, which is formed by splicing two parabolas. The side surface is gradually transitioned from an elliptical shape to a hyperbolic shape, which can make the airflow on, under and beside the fairing smoothly converge at the tail of the fairing, so as to reduce the airflow separation, reduce the resistance of the fairing, and weaken the adverse interference of the fairing separation vortex to the aerodynamic surface of the tail of the helicopter. The gap between the tail cone and the fuselage skin is used for the discharge of the gas in the cabin of the infrared suppressor fairing and the entry of the external cold air, to reduce the temperature in the cabin.

[0048] The air flow enters from the louver air inlet and the square guard net air inlet, and is discharged from the gap between the first mixed exhaust pipe and the second exhaust pipe by the high-speed air flow injection of the first mixed exhaust pipe.

[0049] The half-ellipse is composed of two different upper 1 / 4 ellipse and lower 1 / 4 ellipse, the long axis of the upper ellipse is in the transverse direction to ensure sufficient arrangement space of the first mixed exhaust pipe and the fairing, and the long axis of the lower ellipse is in the vertical direction to reduce the airflow separation at the lower end of the fairing.

[0050] The angle between the louver plane and the longitudinal symmetry plane is 35°-40°, which is the result of comprehensive trade-off between the louver plane oblique direction to reduce the forward flight resistance and the forward direction to increase the air intake; the louver blades are L-shaped, the angle between the outer edge of the blade and the horizontal plane is 18°-20°, and the angle between the inner edge of the blade and the horizontal plane is 45°-47°, so that the louver can shield high-temperature components, and the airflow entering the fairing cabin forms a swirling flow to increase the mixing effect, while ensuring that the air intake resistance will not increase too much.

[0051] The angle between the second exhaust pipe axis and the horizontal plane is 45°-50°, and the upward oblique exhaust gas and the downward washing airflow intersect up and down to more fully mix the cold air.

[0052] The gap between the second exhaust pipe and the first mixed exhaust pipe is 40-45mm, and the overlap amount of the second exhaust pipe and the first mixed exhaust pipe is 50mm-150mm, which can make the injection capacity of the second exhaust pipe more optimal.

[0053] The length-height ratio γ of the tail cone is 1-1.5, which is the result of comprehensive trade-off between the drag reduction effect of the tail cone and the structural weight cost.

[0054] The fairing body does not directly contact the first mixed exhaust pipe, and the distance between the fairing body and the first mixed exhaust pipe is maintained at 150mm-200m, which can weaken the heat radiation of the high-temperature first mixed exhaust pipe on the fairing, while limiting the reduction of the fairing outer contour size to reduce the resistance.

[0055] As shown in Figure 2 , the front view of the infrared suppressor fairing is a half-ellipse cut in the side, and the half-ellipse is divided into an upper half quarter-ellipse with a long axis a1 and a short axis b1, and a lower half quarter-ellipse with a long axis a2 and a short axis b2.

[0056] As shown in Figure 1 , 3As shown, the infrared suppressor fairing has a louvered air inlet 1 along the forward direction. The louvered plane 31 is crescent-shaped with an angle of 35°~40° with the longitudinal symmetry plane. The louvered blades are L-shaped, with the outer edge 11 having an angle of 18°~20° with the horizontal plane and the inner edge 12 having an angle of 45°~47° with the horizontal plane. The L-shape can pre-swirl the cooling airflow to improve mixing efficiency, while also effectively shielding the high-temperature components of the exhaust system.

[0057] A square protective mesh air inlet 2 is located at the front of the top of the infrared suppressor fairing to increase airflow during hovering. An elliptical secondary exhaust pipe 3 is located at the rear of the top, with its axis at an angle of 45°~50° to the horizontal plane, to further cool the high-temperature exhaust gas with the help of the rotor downwash airflow. The primary mixing exhaust pipe 5 can pass through the secondary exhaust pipe 3, with a gap of 40~45mm and an overlap of 50mm~150mm, to utilize the ejection effect of the high-speed exhaust gas to reduce the temperature inside the infrared suppressor fairing.

[0058] The infrared suppressor fairing features a streamlined tail cone 4 at its rear, with a length-to-height ratio γ of 1~1.5. This tail cone is composed of two parabolic sections joined together. Figure 1 The tail cone is formed by the combination of red and green curves, and the side profile gradually transitions from an elliptical shape to a hyperbolic shape. A gap exists between the tail cone and the fuselage skin to facilitate the exhaust of gases from the infrared suppressor fairing and the entry of cool external air, thus reducing the cabin temperature.

[0059] The distance between the infrared suppressor radome and the primary mixing exhaust pipe 5 is maintained at 150mm~200mm. In order to reduce the heat radiation from the primary mixing exhaust pipe to the infrared suppressor radome, heat insulation materials are required in local areas where the distance between the two cannot be guaranteed due to structural limitations.

[0060] Infrared Suppressor Fairing Optimization Design Method

[0061] Based on the dimensions of the helicopter engine exhaust port and the internal structure of the infrared suppressor, a parametric model of the infrared suppressor fairing is established, including geometric parameters such as the major and minor axes of the side elliptical curves of the fairing and the length-to-height ratio of the tail cone. The optimization objectives are to reduce the aerodynamic drag coefficient of the fairing, weaken the aerodynamic interference of the fairing on the horizontal stabilizer, and reduce the surface temperature of the fairing and the average temperature of the exhaust.

[0062] Internal and external flow fields based on CFD methods Figure 5 A comprehensive simulation analysis model considering the fuselage and engine exhaust system was established using a parameterized model. Unstructured tetrahedral meshes were used for aerodynamic simulation calculations, and mesh refinement was performed in areas with large changes in geometric curvature and drastic changes in flow field to improve flow field capture accuracy. The total number of meshes was 20 million to 25 million.

[0063] The momentum source method is used to simulate the downwash flow field (part of the external flow field) of the rotor; the spatial discretization of the simulation calculation adopts the flux difference split format of ROE, the turbulence model adopts the two-equation Realizable model, and the thermal radiation adopts the DO model. The external flow field adopts the velocity inlet and pressure outlet boundary conditions, the engine exhaust adopts the internal flow field flow inlet boundary, and the physical surface adopts the non-slip boundary.

[0064] Based on the CFD calculation results, including the flow field velocity and temperature field distribution, the aerodynamic and thermal characteristics of the infrared suppressor fairing are analyzed, as shown in formulas (1) and (2); from the aspects of optimizing the three-dimensional shape of the fairing side and trailing edge, smoothing the fairing rear body airflow, reducing airflow separation, and minimizing the fairing outer contour, etc., to reduce resistance and weaken the adverse interference on the tail aerodynamic surface, the three-dimensional shape of the fairing side and trailing edge is optimized. Figure 4 Figure 5 From the aspects of improving the ejecting effect, reducing the surface temperature of the infrared suppressor fairing, optimizing the gap and overlap amount of the first-stage mixed exhaust pipe 5 and the second-stage exhaust pipe 3, and comprehensively balancing the influence of the infrared suppressor fairing shape on the aerodynamic performance and thermal characteristics, the aerodynamic scheme of the infrared suppressor fairing is determined.

[0065] The present application analyzes the influence of the infrared suppressor fairing on the aerodynamic characteristics of the fuselage based on the CFD method, optimizes the segmented curvature of the fairing aerodynamic shape to reduce aerodynamic resistance, and weakens the interference of the fairing shedding vortex on the tail aerodynamic surface.

[0066] The present application optimizes the side shape of the infrared suppressor fairing by using the momentum source method to simulate the downwash flow field of the rotor, so as to ensure that the downwash will not cause the high-temperature tail exhaust to directly act on the fairing skin, causing the temperature of the outer surface of the fairing to be too high and affecting the effectiveness of the infrared suppressor.

[0067] The rear part of the infrared suppressor fairing of the present application adopts a streamlined tail cone 4 to reduce aerodynamic resistance; there is a gap between the tail cone and the fuselage skin, which facilitates the discharge of gas in the cabin of the infrared suppressor fairing and reduces the temperature in the cabin.

[0068] The present application sets up a flow guide vane inside the fairing as needed, and the shape and angle of the flow guide vane are optimized and designed according to the flow field distribution to ensure smooth flow and the absence of flow dead zones, thereby avoiding local overheating of the fairing.

[0069] The present application analyzes the temperature field of the internal and external flow fields of the infrared suppressor fairing, realizes the comprehensive optimization of aerodynamic performance and thermal characteristics, and obtains an optimal aerodynamic scheme of the infrared suppressor fairing.

[0070] ​Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the features disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.

[0071] It should be understood that the present disclosure is not limited to the precise structures as herein described and illustrated in the drawings, and that various modifications and changes can be made without departing from its scope. The scope of the present disclosure is limited only by the claims that follow.

Claims

1. A helicopter infrared suppressor fairing, characterized in that, include: fairing body, louvered air inlet, square protective mesh air inlet, secondary exhaust pipe, primary mixing exhaust pipe; The fairing body is viewed as a half-ellipse tangent along its major axis; the half-ellipse is composed of two different upper 1 / 4 ellipses and lower 1 / 4 ellipses. The fairing body has a louvered air intake at the front, and the louvered plane is crescent-shaped; the angle between the louvered plane and the longitudinal symmetry plane is 35°~40°; the louvered blades are L-shaped, the outer edge of the blade is at an angle of 18°~20° with the horizontal plane, and the inner edge of the blade is at an angle of 45°~47° with the horizontal plane. A square protective mesh air inlet is located at the front top of the fairing body; An elliptical secondary exhaust pipe is provided at the rear top of the fairing body to further cool the high-temperature exhaust gas with the help of the rotor downwash airflow; a primary mixing exhaust pipe is sleeved inside the secondary exhaust pipe; the primary mixing exhaust pipe is connected to the generator outlet; the angle between the axis of the secondary exhaust pipe and the horizontal plane is 45°~50°; the gap between the secondary exhaust pipe and the primary mixing exhaust pipe is 40~45mm, and the overlap between the secondary exhaust pipe and the primary mixing exhaust pipe is 50mm~150mm; The rear of the fairing body is designed with a streamlined tail cone. The shape of the streamlined tail cone is formed by splicing two parabolas. The side gradually transitions from an elliptical shape to a hyperbolic shape. There is a gap between the tail cone and the fuselage skin to facilitate the exhaust of gas in the infrared suppressor fairing compartment and the entry of external cold air to reduce the temperature inside the compartment. The length-to-height ratio of the tail cone is 1~1.

5. Airflow enters through the louvered air inlet and the square protective mesh air inlet, and is discharged from the gap between the primary mixing exhaust pipe and the secondary exhaust pipe through the high-speed airflow ejection effect of the primary mixing exhaust pipe. The fairing body does not directly contact the primary mixing exhaust pipe, and the distance between the fairing body and the primary mixing exhaust pipe is maintained at 150mm~200mm.

2. A method for optimizing the aero-thermal design of a helicopter infrared suppressor fairing as described in claim 1, characterized in that, include: The infrared suppressor fairing adopts a leading edge convex design to increase the frontal area, create a scooping effect, and improve air intake efficiency; The trailing edge of the fairing is tapered to reduce aerodynamic drag; The fairing side adopts a multi-segment curved surface splicing design, and the curvature of each segment is optimized according to the flow field distribution; An internal airflow channel is designed between the infrared suppressor shroud and the primary mixing exhaust pipe. The internal airflow channel is used to guide the cooling airflow into the primary mixing exhaust pipe for mixing. A louvered air inlet and a square protective mesh air inlet are designed on the infrared suppressor shroud so that the airflow enters through the louvered air inlet and the square protective mesh air inlet, and is discharged from the gap between the primary mixing exhaust pipe and the secondary exhaust pipe through the high-speed airflow ejection effect of the primary mixing exhaust pipe.

3. The method for optimizing the aero-thermal design of a helicopter infrared suppressor fairing according to claim 2, characterized in that, The design method is implemented in the following way: Based on the dimensions of the helicopter engine exhaust port and the internal structure of the infrared suppressor, a parametric model of the infrared suppressor fairing is established. The parameters of the parametric model include the major and minor axes of the side elliptical curves of the fairing and the length-to-height ratio of the tail cone. The purpose of model optimization is to reduce the aerodynamic drag coefficient of the fairing, weaken the aerodynamic interference of the fairing on the horizontal stabilizer, and reduce the surface temperature of the fairing and the average temperature of the exhaust. Based on the internal and external flow fields and parameterized models using CFD methods, a simulation analysis model that comprehensively considers the fuselage and engine exhaust system is established. Unstructured tetrahedral meshes were used for aerodynamic simulation calculations of the simulation analysis model. Mesh refinement was applied to regions with large variations in geometric curvature and drastic flow field changes to improve flow field capture accuracy. The momentum source method was employed to simulate the rotor downwash flow field, which is a component of the external flow field. The spatial discretization of the simulation calculations used the flux difference splitting scheme of the ROE, and a two-equation turbulence model was adopted for the simulation calculations. The Realizable model is used for the thermal radiation simulation calculations, and the DO model is used for the simulation calculations. The external flow field adopts velocity inlet and pressure outlet boundary conditions, the engine exhaust port adopts internal flow field flow inlet boundary conditions, and the surface adopts no-slip boundary conditions. Based on the aerodynamic simulation results, including the flow field velocity and temperature field distribution, we conducted an aerodynamic and thermal characteristic analysis of the infrared suppressor fairing.

4. The method for optimizing the aero-thermal design of a helicopter infrared suppressor fairing according to claim 3, characterized in that, Conduct aerodynamic and thermal characteristic analysis of the infrared suppressor fairing, including: By optimizing the three-dimensional shape of the fairing's sides and trailing edge, smoothing the airflow behind the fairing, reducing airflow separation, and minimizing the fairing's outer contour as much as possible, drag can be reduced and adverse interference to the tail aerodynamic surfaces can be weakened. To improve the ejection effect, the surface temperature of the infrared suppressor shroud is reduced, and the gap and overlap between the primary and secondary exhaust pipes are optimized. Taking into account the impact of the infrared suppressor fairing shape on aerodynamic performance and thermal characteristics, the aerodynamic scheme of the infrared suppressor fairing was determined.

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