Integrated S-curve nozzle design method and nozzle for blended wing-body aircraft

Abstract

This invention discloses an integrated S-curve nozzle design method and nozzle for aircraft with a blended wing-body layout, belonging to the field of aero-engines. The method comprises the following steps: obtaining the external surface of the blended wing-body aircraft and the position and size parameters of the engine exit; establishing a model of the S-curve section of the nozzle; obtaining and modifying the upper expansion surface at the nozzle exit; designing the centerline of the nozzle's aft deck using Lee curves; designing the double sidewalls of the nozzle's aft deck using Lee curves; obtaining the aft deck profile of the nozzle based on the centerline and double sidewalls determined in steps 3 and 4; and obtaining the sidewall profile of the nozzle exit. This invention solves the problems of limited space layout, large drop between the nozzle exit and the aircraft's tail edge, and maintaining the streamline of the aircraft's external surface after nozzle installation when designing an integrated S-curve nozzle in a blended wing-body layout.

Description

Technical Field

[0001] This invention belongs to the field of aero-engines, specifically relating to an integrated S-curve nozzle design method and nozzle for aircraft with blended wing-body layout. Background Technology

[0002] Based on the higher requirements of next-generation fighter jets for aerodynamics, stealth, and flight time, the blended wing-body configuration, with its outstanding performance advantages, has become an inevitable trend in fighter jet development. The integrated optimization design of the engine and aircraft systems becomes prominent under the blended wing-body configuration, including the issue of matching the engine intake / exhaust design with the aircraft's aerodynamic shape. The nozzle, as a crucial component of the aero-engine, directly affects its thrust performance; it is also a vital part of the aircraft, directly related to the aircraft's aft body shape. Existing engines mainly use axisymmetric nozzles with good internal flow characteristics, but due to their structural and layout limitations, their stealth performance is poor. S-curve nozzles, as an effective means of improving fighter jet stealth capabilities, have received widespread attention. However, the design and installation of the nozzle inevitably interact with the overall aircraft configuration, and designing large-curvature S-curve nozzles within the flat, confined space of a blended wing-body fighter jet presents even greater challenges.

[0003] Existing S-curve nozzle design methods can achieve the requirements of high aerodynamic performance and high stealth performance, but they do not fully consider the integration of the S-curve nozzle with the aircraft's external surface during the design process. Only some nozzles have been modified based on the exit, but the limited space layout and large nozzle exit offset have not been further considered in light of the wing-body blended configuration. Therefore, it is necessary to carry out integrated design research on S-curve nozzles in combination with the wing-body blended configuration.

[0004] Currently, both domestic and international research has been conducted on blended wing-body aircraft and S-shaped nozzles. While foreign countries have already implemented blended wing-body fighter jets equipped with S-shaped nozzles, strict technological embargoes exist. Therefore, this invention proposes an integrated S-shaped nozzle for blended wing-body aircraft and its design method. Summary of the Invention

[0005] The technical problem to be solved:

[0006] To avoid the shortcomings of existing technologies, this invention provides an integrated S-curve nozzle for aircraft with a blended wing-body layout and its design method, in order to solve the problems of limited space layout, large drop between nozzle exit and aircraft tail edge, and maintaining the streamline of the aircraft's outer surface after nozzle installation when designing an integrated S-curve nozzle in a blended wing-body layout.

[0007] The technical solution of this invention is: a design method for an integrated S-curve nozzle based on a blended wing-body aircraft, the specific steps of which are as follows:

[0008] Step 1: Obtain the external surface and engine exit position and size parameters of the blended wing-body aircraft, and establish a model of the nozzle S-curve;

[0009] Step 2: Obtain the expansion surface at the nozzle exit and modify its shape;

[0010] Step 3: Use the Lee curve to complete the design of the centerline of the aft deck of the nozzle;

[0011] Step 4: Use Lee curves to complete the design of the double-sided edge line of the aft deck of the nozzle;

[0012] Step 5: Obtain the nozzle aft deck profile based on the centerline and double sidelines determined in Steps 3 and 4;

[0013] Step 6: Obtain the profile of the nozzle exit sidewall.

[0014] A further technical solution of the present invention is: in step 1, with the engine outlet center x0 as the coordinate center point, the longitudinal height distribution inside the fuselage from the engine outlet to the tail edge of the aircraft is measured, and the outer surface y of the upper back of the fuselage is measured. up =F1(x,z), the external shape of the lower abdomen of the body y down =F2(x,z), where the engine outlet diameter is D0.

[0015] A further technical solution of the present invention is: in step 1, the design constraints of the nozzle S-bend section are obtained based on the acquired parameters, including the nozzle inlet position x. in Nozzle inlet diameter D in Nozzle exit area A ex The nozzle S-curve inlet is located at the engine's low-pressure turbine outlet, i.e., x in =x0; The inlet diameter of the nozzle S-bend is the same as the engine outlet size, i.e., D in =D0; The nozzle exit area is calculated from engine performance parameters using the following formula:

[0016]

[0017] In the formula, P is the gas flow rate at the nozzle inlet. * For total pressure, T * σ is the total temperature, and σ is the nozzle total pressure recovery coefficient;

[0018] Construct the S-curve profile according to the centerline and friction section design method, and ensure that the lowest point a of the S-curve is not lower than the outer surface m at the same axial position, and the highest point b of the S-curve outlet is not higher than the outer surface n at the same axial position, thus completing the modeling of the nozzle S-curve.

[0019] A further technical solution of the present invention is: in step 2, the upper wall surface of the extended nozzle S-bend intersects with the outer edge of the aircraft's outer surface at c, and the upper expansion surface is modified while ensuring the integrity of the curvature of the aircraft's outer surface.

[0020] A further technical solution of the present invention is: in step 3, the front end point d of the center line of the nozzle aft deck is tangent to the lower wall of the nozzle S-curve to ensure continuous curvature, and the downward tilt angle of the end point e of the center line is in the range of -15° to 0°. Adjusting the curve parameters can change the curvature variation law of the center line.

[0021] A further technical solution of the present invention is: the aft deck centerline configuration with the centerline curvature distribution law includes three types, the mathematical expressions of which are as follows:

[0022]

[0023] or

[0024] or In the formula, y0 is the ordinate of the starting point of the aft deck centerline, ΔY is the longitudinal offset of the aft deck centerline, and L is the axial length of the aft deck centerline.

[0025] A further technical solution of the present invention is: in step 4, the front end of the side edge line of the nozzle aft deck is tangent to the lower wall of the nozzle S-curve to ensure continuous curvature, and the downward tilt angle of the end point is in the range of -15° to 0°. Adjusting the curve parameters can change the curvature variation law of the side edge line.

[0026] A further technical solution of the present invention is: in step 5, the center line and double side lines obtained in steps 3 and 4 are used to construct the nozzle aft deck profile that connects the lower wall outlet of the nozzle S-curve section with the tail edge of the aircraft outer surface.

[0027] A further technical solution of the present invention is: in step 6, a side wall is constructed starting from the double side lines of the aft deck of the nozzle, and the exit side wall is modified to ensure the integrity of the curvature of the aircraft's outer surface.

[0028] An integrated S-curve nozzle based on a blended wing-body aircraft is divided into an S-curve section and an integrated design section along the axial direction. The inlet of the S-curve section is connected to the turbine outlet of the aero-engine, and the outlet is connected to the inlet of the integrated design section. The outlet of the integrated design section is constrained by the outer surface of the blended wing-body aircraft.

[0029] The integrated design section includes an upper expansion surface, a rear deck, and two side walls. The upper expansion surface is connected to the upper wall of the S-bend section, and the rear deck is connected to the lower wall of the S-bend section. The two side walls are symmetrically arranged on both sides of the upper expansion surface and the rear deck, forming an integrated structure.

[0030] Beneficial effects

[0031] The beneficial effects of this invention are as follows: Applying the integrated S-curve nozzle based on a blended wing-body aircraft allows for the integrated design of a large-curvature S-curve nozzle within the confined space of the flat rear body of the blended wing-body aircraft, resolving the contradiction between the limited space of the flat layout and the large longitudinal offset of the S-curve nozzle; the S-curve nozzle possesses strong infrared and radar stealth capabilities, and the integration of the blended wing-body layout and the S-curve nozzle further enhances the aircraft's stealth effect and improves its battlefield survivability; the integrated design and segment modification ensure the nozzle exit blends seamlessly with the aircraft's external surface, guaranteeing the smoothness of the aircraft's external surface and resulting in superior stealth performance; the curved design of the aft deck can be adjusted by modifying the Lee curve parameters to change the centerline curvature variation, helping to guide exhaust flow and reduce turbulence, minimizing drag and jet thrust deflection. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the overall structure of an integrated S-curve nozzle for an aircraft based on a blended wing-body layout, which is an optional embodiment of the present invention.

[0033] Figure 2 This is a schematic diagram of the nozzle structure of an integrated S-curve nozzle for an aircraft with a blended wing-body layout, which is an optional embodiment of the present invention.

[0034] Figure 3 This is a transverse cross-sectional view of an integrated S-curve nozzle for an aircraft with a blended wing-body layout, which is an optional feature according to an embodiment of the present invention.

[0035] Figure 4 This is a top view of the upper expansion surface of the outlet of an integrated S-curve nozzle for an aircraft with a blended wing-body layout, which is an optional embodiment of the present invention.

[0036] Figure 5 This is a partial enlarged view of the aft deck centerline of an integrated S-curve nozzle for an aircraft with a blended wing-body layout, which is an optional embodiment of the present invention.

[0037] Figure 6 This is a partial enlarged view of the aft deck profile of an integrated S-curve nozzle for an aircraft with a blended wing-body layout, which is an optional embodiment of the present invention.

[0038] Figure 7 This is an embodiment of the present invention, which shows the internal / external streamlines and wall static pressure diagram of an integrated S-curve nozzle for an aircraft with a blended wing-body layout after adjusting the curvature parameters of the aft deck.

[0039] Explanation of reference numerals in the attached diagram: 1. Aircraft outer surface; 2. S-curve; 3. Exit upper expansion surface; 4. Aft deck; 5. Exit sidewall; 6. Integrated design section; a. Lowest point of the S-curve; b. Highest point of the S-curve exit; c. Intersection of the upper expansion surface and the aircraft outer surface; d. Front end point of the centerline; e. End point of the centerline; m. Adjacent point of the outer surface at the same axial position as point a; n. Adjacent point of the outer surface at the same axial position as point b. Detailed Implementation

[0040] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0041] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0042] This invention provides an integrated S-curve nozzle for a blended wing-body aircraft and its design method, to solve the problems of limited space layout, large drop between nozzle exit and aircraft tail edge, and maintaining the streamline of the aircraft's outer surface after nozzle installation when designing an integrated S-curve nozzle in a blended wing-body configuration.

[0043] This embodiment describes an integrated S-curve nozzle for a blended wing-body aircraft, comprising an S-curve section 2, an upper expansion surface, a rear deck, and two sidewalls forming an integrated design segment. The inlet of the S-curve section is connected to the turbine outlet of the aero-engine, and the outlet is connected to the inlet of the integrated design segment. The outlet of the integrated design segment is constrained by the external shape of the blended wing-body aircraft. The upper expansion surface is connected to the upper wall of the S-curve section, and the rear deck is connected to the lower wall of the S-curve section. The two sidewalls are symmetrically arranged on both sides of the upper expansion surface and the rear deck, forming an integrated structure.

[0044] The lowest point a of the S-curve is not lower than point m of the aircraft's outer surface at the same axial position, and the highest point b of the S-curve exit is not higher than point n of the aircraft's outer surface at the same axial position. The integrated design section modifies the upper expansion surface, the aft deck, and the two side walls according to the low drag design requirements of the outer surface. The upper expansion surface is an irregular horizontal surface, the side walls are irregular vertical surfaces, and the aft deck is a streamlined curved surface.

[0045] The specific steps of the design method in this embodiment are as follows:

[0046] Step one: Analyze the characteristics of the aircraft's external surface 1 (blended wing-body configuration) and the engine outlet location and type. (For...) Figure 1 The analysis focuses on the confined space of the flat fuselage under the blended wing-body configuration shown. Using the engine outlet center x0 as the coordinate center point, the longitudinal height distribution within the fuselage from the engine outlet to the aircraft's tail edge is measured. The outer surface y on the upper back of the fuselage is also analyzed. up =F1(x,z), the external shape of the lower abdomen of the body y down =F2(x,z). Analysis of the engine dimensions and performance parameters is performed, with the engine outlet diameter being D0 and the engine outlet gas flow rate being... Total pressure P * Total temperature T * .

[0047] The nozzle inlet is located at the low-pressure turbine outlet of the engine, and the nozzle diameter is the same as the engine outlet size; the nozzle outlet area is calculated based on engine performance parameters, and the gas flow rate from the nozzle inlet is... Total pressure P * Total temperature T * And from the total pressure recovery coefficient σ of the nozzle, the nozzle exit area can be obtained, that is:

[0048]

[0049] Step 2: Establish the nozzle S-curve 2 model. Based on the longitudinal height distribution of the aircraft's external surface and relevant engine parameters obtained in Step 1, obtain the design constraints for the nozzle S-curve, including the nozzle inlet position x. in Nozzle inlet diameter D in Nozzle exit area A ex The nozzle S-curve inlet is located at the engine's low-pressure turbine outlet, i.e., x in =x0; The inlet diameter of the nozzle S-bend is the same as the engine outlet size, i.e., D in =D0; The nozzle exit area is calculated from engine performance parameters, based on the gas flow rate. Total pressure P * Total temperature T * And from the total pressure recovery coefficient σ of the nozzle, the nozzle exit area can be obtained, that is:

[0050] The S-curve profile was constructed using the centerline and friction section design method. Based on design constraints, the parameters for the S-curve model were determined, including the nozzle length-to-diameter ratio, the ratio of the two bend lengths, the longitudinal offset, and the exit aspect ratio. Considering both nozzle aerodynamic performance and design constraints, the length-to-diameter ratio was selected within the range of 2.5 to 3.0. The nozzle length was less than the axial distance from the nozzle inlet to the aircraft tail edge. The ratio of the two bend lengths ranged from 2:3 to 1:1, and the longitudinal offset of both bends was less than the corresponding longitudinal height. A rectangular exit section was chosen for easier integration with the aircraft's external surface, with an exit aspect ratio ranging from 4 to 6. The S-shaped centerline is constructed using the Lee curve combined with the aspect ratio, the ratio of the two bend lengths, and the longitudinal offset parameters. The inlet circular cross-section and the outlet rectangular cross-section are designed based on the nozzle inlet diameter, outlet area, and outlet width-to-height ratio. A friction section is designed along the centerline to achieve the transition from circular to rectangular. During the design process, it is necessary to ensure that the lowest point a of the S-bend is not longitudinally lower than point m on the outer surface at the same axial position, and the highest point b at the S-bend outlet is not longitudinally higher than point n on the outer surface at the same axial position. This completes the modeling of nozzle S-bend 2. Figure 2 The S-curve of the nozzle is shown.

[0051] Step 3: Obtain the modified shape of the expansion surface 3 at the nozzle exit. (For example...) Figure 3 The upper wall of the extended nozzle S-bend 2 intersects with the aircraft's outer surface 1 (i.e., at point c). While ensuring the integrity of the curvature of the aircraft's outer surface 1, the upper expansion surface 3 is modified, resulting in the modified upper expansion surface as shown below. Figure 4 As shown. Different longitudinal deflection angles of the upper expansion surface 3 can also be designed to make the jet expand to different degrees on the upper side.

[0052] Step four: Use the Lee curve to complete the design of the centerline of the aft deck 4 of the nozzle. For example... Figure 3 The point d at the front end of the aft deck centerline is tangent to the wall of the nozzle S-bend 2 to ensure curvature continuity. The recommended angle range for the end point e of the centerline is -15° to 0°. The longitudinal offset of the Lee curve is given based on the drop between the nozzle exit position and the tail of the aircraft with a blended wing-body layout. Adjusting the Lee curve parameters can change the curvature variation of the centerline, and the curvature distribution is designed based on the jet separation deflection and the mixing of internal and external flows. Figure 5 As shown, three configurations of the aft deck centerline with different curvature distributions are presented, and their corresponding mathematical expressions are as follows:

[0053] ①

[0054] ②

[0055] ③ Where y0 is the ordinate of the starting point of the aft deck centerline, ΔY is the longitudinal offset of the aft deck centerline, and L is the axial length of the aft deck centerline.

[0056] Step 5: Use the Lee curve to complete the design of the double side lines of the nozzle aft deck 4. The front end of the side line is tangent to the wall of the nozzle S-bend 2 to ensure continuous curvature. The recommended range for the end point angle is -15° to 0°. Adjusting the curve parameters can change the curvature variation of the side line. The control method is consistent with the center line control method in Step 4.

[0057] Step Six: Obtain the nozzle aft deck 4 profile. Controlled by the centerline and double sidelines obtained in Steps Four and Five, construct the nozzle aft deck 4 profile connecting the lower wall outlet of the nozzle S-bend 2 to the tail edge of the aircraft outer surface 1, as shown below. Figure 6 As shown.

[0058] Step 7: Obtain the nozzle exit sidewall 5 profile. Construct the sidewall profile starting from the double side lines of the nozzle aft deck 4, and modify the exit sidewall 5 profile while ensuring the integrity of the curvature of the aircraft's outer surface 1.

[0059] The design of the aft deck centerline and double sidelines, as described in steps four and five, can be achieved by adjusting the Lee curve parameters based on aerodynamic principles to alter the centerline curvature. This helps guide exhaust flow and reduce turbulence, minimizing aft drag and improving aircraft performance, resulting in less jet stream separation deflection and superior thrust performance. Figure 7 The paper presents the internal / external streamlines and wall static pressure diagrams of an integrated S-curve nozzle for an aircraft with a blended wing-body layout. By adjusting the curvature parameters of the aft deck, the jet separation deflection is small and the thrust performance is excellent.

[0060] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A design method for an integrated S-curve nozzle based on a blended wing-body aircraft, characterized in that... The specific steps are as follows: Step 1: Obtain the external surface and engine exit position and size parameters of the blended wing-body aircraft, and establish a model of the nozzle S-curve; Based on the acquired parameters, the design constraints for the nozzle S-bend section are obtained, including the nozzle inlet position. x in nozzle inlet diameter D in Nozzle exit area A ex The nozzle S-curve inlet is located at the engine's low-pressure turbine outlet, i.e. x in = x 0, where, x 0 represents the center of the engine exit circle; the inlet diameter of the S-bend section of the nozzle is the same as the engine exit size, i.e. D in = D 0, where, D 0 represents the engine outlet diameter; the nozzle outlet area is calculated from engine performance parameters using the following formula: In the formula, This refers to the gas flow rate at the nozzle inlet. P * For total pressure, T * σ is the total temperature, and σ is the nozzle total pressure recovery coefficient; Construct the S-curve profile according to the centerline and friction section design method, and ensure that the lowest point a of the S-curve is not lower than the outer surface m at the same axial position in the longitudinal direction, and the highest point b of the S-curve outlet is not higher than the outer surface n at the same axial position in the longitudinal direction, and complete the modeling of the nozzle S-curve. Step 2: Obtain the expansion surface at the nozzle exit and modify its shape; Step 3: Use the Lee curve to complete the design of the centerline of the aft deck of the nozzle; the front end point d of the centerline of the aft deck of the nozzle is tangent to the lower wall of the S-bend of the nozzle to ensure the continuity of curvature. The downward tilt angle of the end point e of the centerline is in the range of -15° to 0°. Adjusting the curve parameters can change the curvature variation law of the centerline. The aft deck centerline configuration with the aforementioned centerline curvature distribution pattern includes three types, whose mathematical expressions are as follows: In the formula, y 0 is the ordinate of the starting point of the centerline of the aft deck. Y The longitudinal offset of the aft deck centerline. L This is the axial length of the centerline of the aft deck. Step 4: Use Lee curves to complete the design of the double-sided edge line of the aft deck of the nozzle; Step 5: Obtain the nozzle aft deck profile based on the centerline and double sidelines determined in Steps 3 and 4; Step 6: Obtain the profile of the nozzle exit sidewall.

2. The design method for an integrated S-curve nozzle based on a blended wing-body aircraft according to claim 1, characterized in that: In step 1, with the engine outlet center as the reference point... x 0 is the center point of the coordinate system. The longitudinal height distribution inside the fuselage from the engine outlet to the tail edge is measured, along the y-axis of the upper back of the fuselage. up = F1(x, z), the external shape of the lower abdomen of the body y down = F2(x, z), engine outlet diameter is D 0.

3. The design method for an integrated S-curve nozzle based on a blended wing-body aircraft according to claim 2, characterized in that: In step 2, the upper wall of the extended nozzle S-curve intersects with the outer edge of the aircraft's outer surface at point c. The upper expansion surface is then modified while ensuring the integrity of the aircraft's outer surface curvature.

4. The design method for an integrated S-curve nozzle based on a blended wing-body aircraft according to claim 3, characterized in that: In step 4, the front end of the side line of the nozzle aft deck is tangent to the lower wall of the nozzle S-curve to ensure continuous curvature. The downward tilt angle of the end point is in the range of -15° to 0°. Adjusting the curve parameters can change the curvature variation law of the side line.

5. The design method for an integrated S-curve nozzle based on a blended wing-body aircraft according to claim 4, characterized in that: In step 5, the center line and double side lines obtained in steps 3 and 4 are used to construct the nozzle aft deck profile that connects the lower wall outlet of the nozzle S-curve section with the tail edge of the aircraft's outer surface.

6. The design method for an integrated S-curve nozzle based on a blended wing-body aircraft according to claim 5, characterized in that: In step 6, the sidewall is constructed starting from the double side lines of the aft deck of the nozzle, and the exit sidewall is modified to ensure the integrity of the curvature of the aircraft's outer surface.

7. An integrated S-curve nozzle for an aircraft with a blended wing-body layout, obtained using the design method described in any one of claims 1-6; characterized in that: The structure is divided into an S-curve section and an integrated design section along the axial direction. The entrance of the S-curve section is connected to the turbine outlet of the aero-engine, and the outlet is connected to the inlet of the integrated design section. The outlet of the integrated design section is constrained by the outer surface of the aircraft with a blended wing-body layout. The integrated design section includes an upper expansion surface, a rear deck, and two side walls. The upper expansion surface is connected to the upper wall of the S-bend section, and the rear deck is connected to the lower wall of the S-bend section. The two side walls are symmetrically arranged on both sides of the upper expansion surface and the rear deck, forming an integrated structure.

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