Variable-cycle afterburner and variable-cycle engine thereof

Abstract

The invention provides a variable-cycle afterburner and a variable-cycle engine thereof. An inner culvert channel is located in the center area of the afterburner and used for guiding low-pressure turbine inner culvert airflow; the outer culvert channel surrounds the outer side of the afterburner and is used for guiding fan outer culvert airflow, and the outer culvert channel and the afterburner converge in a mixing area located in the rear middle section of the afterburner. The supporting plate assembly is arranged in an inner channel of the mixing area, and a concave cavity-step combined structure is arranged at the joint of the lower portion of the supporting plate assembly and the center cone and used for preliminarily inducing airflow to change a track to generate a vortex system and breaking the layering phenomenon. The mixing reinforcing structure is a lobe array, is arranged at the shunting ring of the outer culvert and is positioned at the downstream of the supporting plate, the inner side edge of a lobe is connected with the outer wall surface of the inner culvert, and the outer side edge of the lobe is connected with the inner wall surface of the outer culvert to form a transition structure for communicating the inner culvert and the outer culvert; and single / double external culvert mode switching is realized, so that the mixing efficiency is dynamically optimized, and the overall thermal mixing performance is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of engines, in particular to a variable cycle afterburner and a variable cycle engine. BACKGROUND

[0002] As an important development direction of new generation of aviation power technology, the variable cycle engine successfully combines the subsonic low fuel consumption characteristics of the large bypass ratio turbofan engine and the supersonic high thrust characteristics of the turbojet engine by dynamically adjusting the thermodynamic cycle parameters through adjustable components, and shows great application potential in military and civil aviation fields. As a key component for realizing thrust enhancement of the variable cycle engine, the mixing efficiency of the mixing area of the afterburner directly determines the thrust enhancement capability and energy efficiency of the engine, so the optimization design of the mixing area has always been a technical difficulty and research hotspot in this field.

[0003] In the prior art, the mixing area of the variable cycle engine afterburner mainly relies on the rear bypass variable area ejector (RVABI) to realize the mixing of the inner and outer bypass airflow. The traditional area adjustment methods mainly include two technical routes of translational adjustment and rotational adjustment. However, these traditional technical solutions have serious performance defects in actual application. The thermal mixing efficiency of the translational adjustment scheme is only 0.2-0.3, and it is difficult to break through the efficiency upper limit of 0.3 even at the best operating condition; the thermal mixing efficiency of the rotational adjustment scheme is slightly improved in some specific modes and can reach 0.2-0.4, but the overall performance improvement is limited and still in the low efficiency range. More seriously, both of these two traditional adjustment methods have obvious airflow stratification phenomenon, which leads to poor uniformity of the mixing area flow field, seriously affects the combustion stability of the afterburner, and further limits the improvement space of the overall performance of the engine.

[0004] The root cause of the above problems lies in the fact that the traditional mixing area structure lacks effective vortex generation and regulation mechanism. The translational and rotational adjusters can only realize simple area adjustment function and cannot generate vortex structures with sufficient strength to promote the mass, momentum and energy exchange of the inner and outer bypass airflow during the airflow mixing process. In addition, the existing technology has poor adaptability under different flight modes, and it is difficult to realize efficient switching between the single outer bypass mode and the double outer bypass mode, which cannot meet the demand of high efficient operation of the variable cycle engine under all operating conditions.

[0005] In view of this, the present application is proposed. SUMMARY

[0006] The present application discloses a variable cycle afterburner and a variable cycle engine, which aims to solve the problem of low mixing efficiency of inner and outer bypass airflow in the mixing area of the variable cycle afterburner, which limits the combustion stability and engine performance.

[0007] The first embodiment of the present application provides a variable cycle afterburner, comprising an inner duct, an outer duct, a strut assembly, a mixing enhancement structure and a flow regulating device; The inner duct is located in the central region of the afterburner and is composed of an inner duct upper wall, an inner duct lower wall and a center cone, and is used for guiding the low-pressure turbine inner duct airflow; The outer duct is located outside the inner duct and is composed of an inner duct outer wall and an outer duct inner wall, and is used for guiding the fan outer duct airflow; The inner duct and the outer duct converge at a mixing area, and the mixing area is located in the middle and rear section of the afterburner; The strut assembly is arranged in the inner duct of the mixing area and comprises a plurality of struts uniformly distributed in the circumferential direction, the upper and lower ends of the struts are fixedly connected with the inner duct upper wall and the inner duct lower wall respectively, and a cavity-step combined structure is arranged at the connection position of the lower part of the strut and the center cone; The mixing enhancement structure is a lobed array, which is arranged at the outer duct split ring and located downstream of the struts, the inner side edge of the lobed array is connected with the inner duct outer wall, and the outer side edge is connected with the outer duct inner wall, thereby forming a transition structure connecting the inner and outer ducts; The flow regulating device is a translational area regulator, which is arranged at the same axial position of the lobed array, coaxially distributed with the lobed array and located in the gap between the lobed arrays, and the outlet area of the outer duct is changed by translational movement along the axial direction.

[0008] Preferably, the leading edge of each strut is located at the inlet of the inner duct and adopts an airfoil design, and the tail of the strut is perpendicular to the airflow direction; Preferably, the number of struts is 18, and the included angle between adjacent struts is 20°.

[0009] Preferably, the cavity-step combined structure comprises a cavity and a first step and a second step connected with the lower side of the cavity in sequence, the first step and the second step are perpendicular to the normal direction of the center cone, and the step side surface is parallel to the strut side surface.

[0010] Preferably, the cavity-step combined structure is used to generate a backflow area to drive the inner duct airflow to deviate to the center cone.

[0011] Preferably, the cross section of the lobed array is wavy, and the lobed array structures with two different heights are staggered, the height ratio of the lobed array is H1 / H2=β, the value range of β is 0.5-2.0, and the lobed array structures at adjacent positions are the same.

[0012] Preferably, the number and the circumferential distribution angle of the translational area adjuster are matched with the lobes, each adjuster is located radially outside the corresponding lobe, the side of the adjuster is triangular, and the radial height of the adjuster is 0.8-1.2 mm lower than the lobe, so that the variable flow area can be formed with the lobe when moving axially.

[0013] Preferably, the bottom of the translational area adjuster adopts a curved suture design and is in sliding fit with the inner wall surface of the outer channel, when the adjuster moves axially to the left to the limit position, the triangular side of the adjuster completely blocks the flow area between the lobe and the outer channel, so that the area of the outer channel outlet is minimized to realize the single outer channel mode; when the adjuster moves axially to the right to the limit position, the adjuster completely exits the lobe area, the outer channel outlet is fully open, and the double outer channel mode is realized.

[0014] The second embodiment of the present application provides a variable cycle engine comprising the variable cycle afterburner according to any one of the preceding embodiments.

[0015] Based on the variable cycle afterburner and the variable cycle engine provided by the present application, the inner channel is located in the central region of the afterburner and is composed of an upper inner wall surface, a lower inner wall surface and a center cone for guiding the low-pressure turbine inner channel airflow, and the outer channel is arranged outside the inner channel and is composed of an inner wall surface and an outer wall surface to form an annular flow passage for guiding the fan outer channel airflow, and the two are combined in a mixing area located in the middle and rear section of the afterburner; the strut assembly is arranged in the inner channel of the mixing area and comprises a plurality of struts uniformly distributed in the circumferential direction, the upper and lower ends of the struts are fixedly connected with the upper and lower inner wall surfaces respectively, and a cavity-step combined structure is arranged at the connection between the lower end of the strut and the center cone for preliminarily inducing airflow to change the trajectory to generate vortex system and break the stratification phenomenon; the mixing enhancement structure is a lobe array arranged at the outer channel splitter ring and located downstream of the struts, the inner edge of the lobe is connected with the inner wall surface, and the outer edge is connected with the outer wall surface to form a transition structure connecting the inner and outer channels and further strengthening large-scale disturbance and mass exchange; the flow adjusting device is a translational area adjuster arranged at the same axial position of the lobe array, coaxially distributed with the lobes and located in the gap between the lobes, and the outlet area of the outer channel is changed by translational movement in the axial direction to realize single / double outer channel mode switching, thereby dynamically optimizing the mixing efficiency and improving the overall thermal mixing performance. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 and Figure 2 is a structural schematic diagram of a variable cycle afterburner provided by the first embodiment of the present application.

[0017] Figure 3 is a schematic diagram of the area adjustment mode of LAR, BAR and RAR; Figure 4 is a schematic diagram of the mixing efficiency contrast curve; Figure 5 is a schematic diagram of the mixing efficiency distribution of the double-annular mode under different lobe height ratios (β). DETAILED DESCRIPTION

[0018] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the scope of protection of the present application. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0019] The specific embodiments of the present application will be described in detail below with reference to the drawings.

[0020] The present application discloses a variable cycle afterburner and a variable cycle engine thereof, aiming to solve the problem of low mixing efficiency of the inner-annular and outer-annular air flow in the mixing area of the variable cycle afterburner, which limits the combustion stability and engine performance.

[0021] Please refer to Figure 1 and Figure 2 , the first embodiment of the present application provides a variable cycle afterburner, comprising an inner-annular passage 1, an outer-annular passage 2, a strut assembly 3, a mixing enhancement structure 4 and a flow regulating device 5. The inner-annular passage 1 is located in the central area of the afterburner, which is composed of an inner-annular upper wall, an inner-annular lower wall and a center cone, and is used to guide the inner-annular air flow of the low-pressure turbine. The strut assembly 3 is arranged in the inner-annular passage 1 of the mixing area, which comprises a plurality of struts uniformly distributed in the circumferential direction, the upper and lower ends of the struts are fixedly connected with the inner-annular upper wall and the inner-annular lower wall respectively, and a cavity-step combined structure 6 is arranged at the connection between the lower part of the strut and the center cone. It should be noted that the inner-annular passage 1 is located in the central area of the afterburner, which is composed of an inner-annular upper wall, an inner-annular lower wall and a center cone. The center cone, as the inner boundary of the inner-annular passage 1, extends along the engine axis direction.

[0022] The support plate assembly 3 arranged in the inner channel 1 can include 18 support plates which are evenly distributed in the circumferential direction, and the included angle between adjacent support plates is controlled to be 20° to ensure the uniformity of air flow distribution. The leading edge of each support plate is located at the inlet of the inner channel 1 and adopts an airfoil design to minimize the blocking loss of the air flow. The support plate extends in the radial direction from the inner side to the outer side of the inner channel 1, and the upper and lower ends thereof are fixedly connected with the inner channel upper wall and the inner channel lower wall respectively by high-temperature welding process, which can withstand the thermal stress and mechanical stress during engine operation. The tail of the support plate adopts a truncated design perpendicular to the direction of air flow to ensure that the air flow can form a clear separation line when leaving the support plate, thereby avoiding unnecessary wake vortex loss.

[0023] A cavity-step combination structure 6 is arranged at the area below each support plate and connected with the center cone. The cavity-step combination structure 6 is a key component for enhancing air flow mixing. The cavity is first formed on the outer surface of the center cone by machining, and the depth of the cavity is 8-12 mm, and the width of the cavity matches the chordal width of the support plate at this position. The front and rear edges of the cavity adopt a circular arc transition to avoid flow separation caused by sharp edges. A first step 62 and a second step 63 are sequentially arranged downstream of the cavity 61, and the height of the first step and the height of the second step are 10 mm. The bottom surfaces of the two steps are perpendicular to the normal direction of the center cone at this position, and the side surfaces of the steps are parallel to the side surfaces of the support plates to ensure geometric consistency. The cavity-step combination structure 6 plays an important role when the air flow passes through. Specifically, when the inner channel air flow passes through the step structure, flow separation will occur behind the step due to geometric mutation, forming a low-speed backflow area. The low-pressure area in the backflow area will produce a suction effect on the upstream inner channel air flow, causing the air flow originally flowing along the center line of the inner channel 1 to deflect towards the center cone surface, thereby changing the original trajectory of the air flow. It should be noted that the deflection movement towards the center cone not only enhances the disturbance mixing of the inner channel air flow, but also creates more favorable initial conditions for air flow exchange in the downstream mixing area, so that the inner and outer channel air flows can be more fully contacted and mixed.

[0024] The outer channel 2 surrounds the outer side of the inner channel 1 and is composed of an inner channel outer wall and an outer channel inner wall to guide the fan outer channel air flow; The inner channel 1 and the outer channel 2 converge in the mixing area, and the mixing area is located in the middle and rear section of the afterburner; It should be noted that the radial height of the outer channel 2 is determined according to the design requirements of the bypass ratio of the variable cycle engine to ensure that the fan outer bypass airflow has sufficient flow area. The inner wall surface of the outer channel is designed in a smooth streamline shape to avoid unnecessary resistance loss to the outer bypass airflow. The inner wall surface of the outer channel is also designed in a streamline shape, and the material is selected from a nickel-based alloy or a titanium alloy that can withstand the working pressure and temperature load of the outer bypass airflow. The cross-sectional area of the outer channel 2 changes along the axial direction: the cross-sectional area remains relatively constant in the upstream section to ensure that the outer bypass airflow from the fan can be evenly distributed and smoothly flow, and the geometry gradually adjusts in the area close to the mixing area to prepare for the subsequent airflow convergence.

[0025] The inner channel 1 and the outer channel 2 converge at the mixing area, which is located in the middle and rear section of the afterburner and can be at an axial position 60%-75% away from the afterburner inlet. The design of the mixing area is a key area of the entire afterburner, which provides sufficient mixing space and time for the two airflows with different temperatures and speeds. At the inlet cross section of the mixing area, the inner and outer channel airflows still maintain a relatively independent flow state, but as the axial distance increases, the two airflows begin to exchange mass, momentum and energy strongly, so that the high-temperature and high-speed inner channel airflow and the relatively low-temperature outer channel airflow can penetrate and entrain each other under the action of pressure gradient, and finally form a mixed airflow with relatively uniform temperature and speed distribution at the outlet of the mixing area.

[0026] The mixing enhancement structure 4 is a lobed array, which is arranged at the outer channel splitter ring and located downstream of the strut, the inner edge of the lobe is connected to the outer wall of the inner channel, and the outer edge is connected to the inner wall of the outer channel, forming a transition structure connecting the inner and outer channels. It should be noted that the mixing enhancement structure 4 adopts a lobed array form, which is arranged at the outer channel splitter ring and located 5-15 mm downstream of the strut assembly 3, ensuring that the inner and outer channel airflows are mixed deeply after being disturbed by the strut. The lobed array contains 18 lobes, which are uniformly distributed along the circumference of the combustion chamber, and the included angle between adjacent lobes is 20°, which is staggered by 10° in the circumferential position with the strut. This staggered arrangement can avoid the direct interference of the strut wake on the lobe inlet flow field, while ensuring that the airflow obtains sufficient circumferential diffusion before entering the lobe. The inner edge of each lobe is smoothly connected to the outer wall of the inner channel, and the outer edge is smoothly connected to the inner wall of the outer channel through a curvature surface, forming a fluid channel connecting the inner and outer channels. The axial length of the lobe is 100 mm, and the thickness of the thinnest right end is only 1 mm. This gradually changing thickness design not only ensures the structural strength, but also maximizes the reduction of the blocking effect on the airflow.

[0027] The cross section of the lobes presents a unique wavy profile, which induces large-scale streamwise vortices by changing the flow path of the gas flow, significantly enhancing the momentum and energy exchange between the inner and outer annulus flows. To further optimize the mixing performance under different operating conditions, the lobe array adopts an innovative asymmetric height design, specifically, two different height wavy structures are staggered, the first lobe has a wave peak height of H1, and the second lobe has a wave peak height of H2, the height ratio β = H1 / H2 is adjustable within the range of 0.5 to 2.0, and the lobes one position apart adopt the same height configuration, i.e. the first, third, fifth, etc. odd positions adopt the lobe with height H1, and the second, fourth, sixth, etc. even positions adopt the lobe with height H2. Test data show that when β = 2, i.e. the height of the high lobe is twice that of the low lobe, the optimal thermal mixing efficiency can be obtained in the double-outer-annulus mode, and the mixing efficiency can reach 0.9; while when β = 0.5, although the mixing efficiency at the lobe outlet is slightly lower, better flow field uniformity is shown at the downstream cross section.

[0028] The flow regulating device 5 is a translational area regulator, which is arranged at the same axial position of the lobe array, distributed coaxially with the lobes and located in the gap between the lobes, and changes the outlet area of the outer annulus passage 2 by translational movement along the axial direction.

[0029] It should be noted that the flow regulating device 5 adopts a translational area regulator design, and the regulator assembly is arranged at the same axial position of the lobe array, forming a coordinated regulating system with the lobes. The translational area regulator contains 18 independent regulating units, which are uniformly distributed circumferentially and arranged coaxially with the lobe array, each regulator is precisely positioned in the gap between two adjacent lobes, and the included angle between adjacent regulators is 20°, which makes the regulators and lobes present an alternating distribution pattern in the circumferential direction, making full use of the annular space and avoiding structural interference. The regulator moves smoothly along the axial direction through a precise guide rail mechanism, and the maximum moving stroke is designed to be 80mm according to the operating mode requirements of the engine. Within the entire stroke range, the regulator always maintains a motion trajectory parallel to the center axis of the combustion chamber, ensuring the stability and reliability of the regulating process.

[0030] Each translational area regulator has an exact geometric matching relationship with the corresponding lobe in structural design. The regulator is located radially outside the lobe, and the side thereof is designed in a triangular cross-section. The apex angle of the wedge-shaped structure is optimized to 30-45°, which can smoothly change the flow passage area during axial movement. The radial height of the regulator is precisely calculated and set to be 0.8-1.2 mm lower than the maximum height of the adjacent lobe, and the preferred value in the embodiment is 1 mm. The setting of the height difference has important fluid dynamics significance, which ensures that the regulator can effectively control the flow distribution of the outer flow during the full stroke movement, and will not produce mechanical contact or excessive airflow obstruction with the lobe. The axial length of the regulator is 180 mm, of which the front half is 80 mm, from thin to thick, matching the lobe space, and used for adjusting the size of the outer channel outlet area when moving left and right; the rear half is 100 mm, from thick to thin, reducing the wake loss.

[0031] The bottom of the regulator adopts an innovative curved suture design, and the curvature radius of the curved surface is completely consistent with that of the inner wall surface of the outer channel 2, which ensures the fitting accuracy therebetween. The bottom surface of the regulator is precisely machined and surface treated, and cooperates with a special high-temperature-resistant sealing material to form a low-friction sliding fit with the inner wall surface of the outer channel, and the cooperation gap is controlled within the range of 0.1-0.2 mm, which not only ensures the sealing performance, but also realizes smooth sliding movement. During the working process, when the variable cycle engine needs to switch to the single outer channel mode, the control system drives the regulator to move axially to the left, and as the regulator gradually enters the lobe area, the triangular side thereof begins to block the annular flow passage between the outer side of the lobe and the outer channel 2. When the regulator moves to the left limit position, the triangular side completely closes the flow passage of the outer side of the lobe. At this time, all the outer flow is forced to change the flow path and pass through the wave-shaped passage inside the lobe. Under the action of forced flow guiding, the outer flow and the inner flow produce strong mixing inside the lobe, and the thermal mixing efficiency can reach 0.7-0.8. At the same time, the effective flow passage area of the outer channel outlet is reduced to the minimum value, realizing the working characteristics of the single outer channel mode.

[0032] Conversely, when the engine needs to switch to the dual-bypass mode to obtain greater thrust or better economy, the area regulator is moved rightward along the axis under the drive of the servo mechanism, gradually exiting the lobe area, and as the area regulator retreats, the flow passage outside the lobe is gradually opened, and the outer bypass airflow obtains more flow passage options. When the area regulator is completely moved to the right limit position, the area regulator completely exits the lobe influence area, at this time, the outer bypass airflow can pass through the wave-shaped passage inside the lobe and the annular passage outside the lobe at the same time, the flow area reaches the maximum value, and the full-open state of the dual-bypass mode is realized. In this working state, although the forced mixing effect is weakened, due to the flow direction vortex induced by the lobe and the larger flow area, the overall mass flow is significantly increased, and when the lobe height ratio β is optimized to 2, even in the dual-bypass mode, the thermal mixing efficiency can still be kept at a high level of 0.8-0.9, fully embodying the superiority of the design of the application. Through the continuous adjustment of the area regulator between the two limit positions, stepless change of the bypass ratio from 0.3 to 1.5 can be realized, and the thrust demand and fuel economy requirement in different flight states can be accurately matched, thereby providing a flexible and efficient flow control scheme for the variable cycle engine.

[0033] The working process of the variable cycle afterburner is briefly described as follows: The fan outer bypass airflow enters from the outer bypass inlet, and the low-pressure turbine inner bypass airflow enters from the inner bypass inlet, and both flow into the mixing area, When the airflow flows through the strut, the airflow is forced to change the original trajectory by the concave-step combination structure 6 below the strut, the concave and the first step and the second step, to form an initial flow direction vortex, effectively breaking the stratification phenomenon of the inner and outer bypass airflows, and the airflow continues to flow to the lobe area, and the lobe structure induces large-scale flow direction vortexes to be generated through the wave-shaped cross section and the height ratio design, to promote the cross-bypass entrainment and mixing of the outer and inner bypass airflows, and significantly enhance the mass, momentum and energy exchange.

[0034] The area regulator changes the outer bypass outlet area by translation, when moved to the left limit position, the outer bypass outlet area is the smallest, and the single-bypass mode is entered, and when moved to the right limit position, the outer bypass outlet is fully opened, and the dual-bypass mode is entered, so as to dynamically adjust the bypass ratio, and in combination with the optimization of the lobe height ratio, the efficient mixing demand in different flight modes is met.

[0035] Please refer to the accompanying drawings Figures 3 to 5 :

[0036] The second embodiment of the application provides a variable cycle engine comprising the variable cycle afterburner according to any one of the preceding embodiments.

[0037] Based on the variable cycle afterburner and the variable cycle engine provided by the application, the inner channel is located in the central region of the afterburner and is composed of an upper inner channel wall, a lower inner channel wall and a central cone for guiding the low-pressure turbine inner channel airflow, the outer channel is located outside the inner channel and is composed of an inner outer channel wall and an outer outer channel wall to form an annular flow passage for guiding the fan outer channel airflow, the two are combined in a mixing area located in the middle and rear section of the afterburner, the strut assembly is arranged in the inner channel of the mixing area and includes a plurality of struts uniformly distributed in the circumferential direction, the upper and lower ends of the struts are fixedly connected with the upper inner channel wall and the lower inner channel wall respectively, a cavity-step combined structure is arranged at the connection position of the lower struts and the central cone to preliminarily induce airflow change trajectory to generate vortex system and break the stratification phenomenon, the mixing enhancement structure is a lobed array arranged at the outer channel splitter ring and located downstream of the struts, the inner side edge of the lobed array is connected with the inner outer channel wall and the outer side edge is connected with the outer outer channel wall to form a transition structure connecting the inner and outer channels and further strengthening large-scale disturbance and mass exchange, and the flow regulating device is a translational area regulator arranged at the same axial position of the lobed array, coaxially distributed with the lobed array and located in the gap between the lobed arrays, the outlet area of the outer channel is changed by axial translation to realize single / dual outer channel mode switching, thereby dynamically optimizing the mixing efficiency and improving the overall thermal mixing performance.

[0038] The above is only the preferred embodiment of the application, and the protection scope of the application is not limited to the above-mentioned embodiments, and any technical solution falling within the idea of the application belongs to the protection scope of the application.

Claims

1. A variable cycle afterburner, characterized by, The variable cycle afterburner comprises an inner bypass channel, an outer bypass channel, a strut assembly, a mixing enhancement structure and a flow regulating device. The inner bypass channel is located in the central region of the afterburner and is composed of an inner bypass upper wall, an inner bypass lower wall and a center cone, and is used for guiding the low-pressure turbine inner bypass airflow. The outer bypass channel is located outside the inner bypass channel and is composed of an inner bypass outer wall and an outer bypass inner wall, and is used for guiding the fan outer bypass airflow. The inner bypass channel and the outer bypass channel are combined in a mixing area, and the mixing area is located in the middle and rear section of the afterburner. The strut assembly is arranged in the inner bypass channel of the mixing area and comprises a plurality of struts which are uniformly distributed in the circumferential direction, and the upper and lower ends of the struts are fixedly connected with the inner bypass upper wall and the inner bypass lower wall respectively, and a cavity-step combined structure is arranged at the connection position between the lower end of the strut and the center cone. The mixing enhancement structure is a lobed array, is arranged at the outer bypass split ring and is located downstream of the struts, the inner side edge of the lobed array is connected with the inner bypass outer wall, and the outer side edge is connected with the outer bypass inner wall, thereby forming a transition structure which connects the inner bypass channel and the outer bypass channel. The flow regulating device is a translational area regulator, is arranged at the same axial position of the lobed array, is coaxially distributed with the lobed array and is located in the gap between the lobed arrays, and the translational area regulator changes the outlet area of the outer bypass channel by moving along the axial direction.

2. A variable cycle afterburner as claimed in claim 1, wherein The leading edge of each strut is located at the inlet of the inner bypass channel and adopts an airfoil design, and the tail of the strut is perpendicular to the airflow direction. The number of the struts is 18, and the included angle between adjacent struts is 20°.

3. A variable cycle afterburner as set forth in claim 1 wherein, The cavity-step combined structure comprises a cavity and a first step and a second step which are sequentially connected with the lower side of the cavity, and the first step and the second step are perpendicular to the normal direction of the center cone, and the step side surface is parallel to the strut side surface.

4. A variable cycle afterburner as set forth in claim 1 wherein, The cavity-step combined structure is used for generating a backflow area to drive the inner bypass airflow to deviate to the center cone.

5. A variable cycle afterburner as set forth in claim 1 wherein, The cross section of the lobed array is in a wave shape, and lobed structures with two different wave heights are staggered, and the height ratio of the lobed structures is H1 / H2=β, and the value range of β is 0.5-2.0, and the lobed structures at positions which are separated by one position are the same.

6. A variable cycle afterburner as set forth in claim 1 wherein, The number and circumferential distribution angle of the translational area regulators are matched with the lobed array, each regulator is located at the outer side of the corresponding lobed array in the radial direction, the side surface of the regulator is triangular, the radial height of the regulator is lower than that of the lobed array by 0.8-1.2 mm, so that the translational area regulator can form a variable flow area with the lobed array when moving axially.

7. A variable cycle afterburner as set forth in claim 1 wherein, The bottom of the translational area regulator adopts a curved suture design and is in sliding fit with the inner wall of the outer bypass channel, when the translational area regulator moves to the limit position along the axial direction, the triangular side surface of the translational area regulator completely blocks the flow area between the lobed array and the outer bypass channel, so that the outlet area of the outer bypass channel is minimized, and the single outer bypass mode is realized, and when the translational area regulator moves to the limit position along the axial direction, the translational area regulator completely exits the lobed array area, the outer bypass outlet is fully opened, and the double outer bypass mode is realized.

8. A variable cycle engine characterized by, The variable cycle afterburner comprises an inner bypass channel, an outer bypass channel, a strut assembly, a mixing enhancement structure and a flow regulating device.

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