Lobe-type rear duct ejector with modal adjustment and mixing enhancement functions

Abstract

The present invention discloses a lobe-type rear duct ejector with modal adjustment and mixing enhancement functions, comprising a variable geometry lobe, a hydraulic actuator, a transmission mechanism, an outer casing, an intermediate casing, and a central cone. The variable geometry lobe is composed of a fixed crest and an adjustable trough, and the lobe sidewalls are a foldable structure that can adjust the flow area of ​​the duct outlet according to the ejection requirements of the outer duct airflow. The sidewall receiving cavity on the outer casing can reduce the limitation of the adjustable trough's outward deflection, helping the variable geometry lobe to further reduce the lower limit of the bypass ratio adjustment, thereby better leveraging the high-speed performance of the near-turbojet mode. During the transition to the turbofan mode, as the folded sidewalls unfold, the leeward side of the sidewalls can induce the jet wake to generate large-scale flow vortices, thereby enhancing mixing and increasing the thrust gain of the mixed jet. The present invention can meet the performance requirements of ejectors of different modes, enabling the rear duct ejector to maintain excellent thrust performance under all operating conditions.

Description

Technical Field

[0001] The present invention relates to a lobe-type rear duct ejector with modal adjustment and mixing enhancement functions, belonging to the technical field of aviation power devices. Background Art

[0002] With the advancement of aviation technology and evolving military requirements, fighter aircraft are being assigned an increasing number of missions. Today's advanced fighters are capable of performing nearly all combat missions, with the exception of strategic bombing and some support missions. The next generation of fighter aircraft will further expand the boundaries of functionality and performance, designating four standard features: super maneuverability, ultra-stealth, beyond-visual-range strike, and supersonic cruise. Ensuring that aircraft possess both the ability to rapidly penetrate and reach the battlefield while maintaining exceptionally long airborne loiter capacity presents a pressing challenge for the next generation of fighter powertrains. In this application context, conventional aircraft engines are increasingly unable to meet the dual performance requirements of advanced fighter aircraft: high specific thrust and low cruise fuel consumption. Therefore, the development of variable-cycle turbofan engines with adjustable bypass ratios has become an inevitable trend.

[0003] The variable cycle engine introduces a new external duct and, through multiple variable geometry components such as the rear duct ejector, front duct ejector, and mode selector valve, allows for a wider range of adjustment of thermodynamic cycle parameters (such as flow rate, pressure ratio, and bypass ratio). This enables the engine to operate in both turbofan and turbojet modes to meet the requirements of different flight missions. The rear duct ejector, as the core component for internal flow mode regulation, can independently control the low-pressure rotor speed to a certain extent. Furthermore, the rear duct ejector is also a structurally adjustable mixer. Therefore, it must balance the performance of both internal flow regulation and jet mixing. Among them, internal flow regulation can be regarded as the ability of the rear duct ejector to regulate the duct back pressure to a certain extent, and the duct throttling and ejection performance of the regulating mechanism need to be considered; and the demand for mixing performance is usually under a large bypass ratio state. At this time, the outer duct has more working fluid to absorb the residual velocity and waste heat energy of the turbine exhaust. After sufficient mixing, this part of energy can be converted into useful work, further improving the mass addition effect and the thrust increase effect brought by the mixed exhaust, thereby giving full play to the advantage of the high modal thermal efficiency of the turbofan.

[0004] Currently, most proposed rear ducted ejector solutions, both domestically and internationally, involve either a linearly moving rigid valve body or an axisymmetric adjustment mechanism similar to an adjustable nozzle. The former's profile is difficult to optimize for the transitional flow pattern, resulting in significant flow field distortion and airflow deflection angles, and high aerodynamic losses. The latter's adjustment mechanism is complex, and the jet wake vortex induced by the annular trailing edge is overly simple, resulting in poor mixing performance and difficulty meeting the requirements for increased mixed-displacement thrust at high bypass ratios. Therefore, within a wide range of bypass ratios, the flow field organization and mixing enhancement issues of the rear ducted ejector at both the design and non-design points urgently need to be addressed. Summary of the Invention

[0005] This invention provides a lobe-type rear ducted ejector with modal adjustment and mixing enhancement capabilities. This technology involves a single-degree-of-freedom internal flow modal adjustment technique that achieves efficient ejection and thrust increase by varying the ejector's trailing edge configuration. This technique can be applied to variable-cycle and adaptive engines. Its purpose is to maintain superior thrust performance across all operating conditions and effectively address the issues mentioned in the background art regarding the complex ejector adjustment mechanism, poor flow field organization, and low mixing efficiency at high bypass ratios.

[0006] To achieve the above objectives, the present invention employs a technical solution: a lobe-type rear duct ejector with modal adjustment and mixing enhancement capabilities, comprising a variable-geometry lobe, a hydraulic actuator, a transmission mechanism, an outer casing, an intermediate casing, and a central cone. The intermediate casing is positioned between the outer casing and the central cone, while the transmission mechanism and hydraulic actuator are located outside the outer casing. The variable-geometry lobe is located at the rear of the intermediate casing, where the turbine exhaust and the outer duct flow meet. It consists of fixed crests and adjustable troughs, with the lobe sidewalls being a foldable structure. The ejector's trailing edge configuration and duct outlet area can be adjusted by deflecting the adjustable troughs.

[0007] The variable-geometry lobes enhance the mixing effect of the lobe-induced streamwise vortices based on the variable-cycle engine's injection requirements, improving mixed-displacement thrust performance at high bypass ratios, maximizing the turbofan's high propulsion efficiency, and achieving lower subsonic cruise fuel consumption. At low bypass ratios, the adjustable troughs deflect outward, reducing the lobe expansion angle and curbing the development of the streamwise vortices. This significantly reduces viscous dissipation and mechanical energy losses in the jet, thereby ensuring high-speed internal flow power output.

[0008] The tail of the fixed wave crest is a tortuous periodic "П"-shaped structure, the side walls of which overlap with the adjustable trough to form the side walls of the variable geometry lobe. In addition to increasing the expansion angle of the lobe and expanding the adjustment range of the ejector bypass ratio, the wave crest sidewall structure can also share the circumferential load of the adjustable trough, reduce the design requirements of the adjustable trough expansion angle, and effectively reduce the situation where the adjustable trough sidewall protrudes from the wave crest during the internal flow mode adjustment process, widening the bypass ratio range for the formation of the wave crest-induced flow vortex, and ensuring that the convective mixing effect of the lobe-induced vortex is fully utilized under the large bypass ratio state with a high mixing level. Rectangular slots are evenly arranged between the periodic "П"-shaped structures of the fixed wave crest, and the slot width is consistent with the width of the adjustable trough. A hinged joint is provided on the front end side wall of the slot for installing the adjustable trough.

[0009] The adjustable trough is a trough-shaped structure, mounted on the hinged joint of the fixed crest via a hinge pin. A hinged lug is provided at the front end of the trough, near the outer casing, to connect to the transmission mechanism. The fixed crest top, overlapping sidewalls, and adjustable trough bottom together form the trailing edge configuration. Driven by a hydraulic actuator, the adjustable trough rotates about the hinge pin, thereby changing the expansion angle of the variable geometry lobe and adjusting the flow area of ​​the duct and turbine outlet. As the sidewalls expand, the low-pressure area on the leeward side gradually expands, enhancing the convection effect of the resulting large-scale streamwise vortex, thereby drawing more of the outer duct airflow into the mixing process.

[0010] Preferably, define α lp 、 α lv are the expansion angles of the fixed crest and adjustable trough sidewalls, respectively, and the expansion angles satisfy: 0.4≤ α lv / ( α lp + α lv )≤0.6.

[0011] Furthermore, when the variable geometry lobe is at its minimum opening, the bottom surface of the adjustable trough is flush with the top surface of the fixed crest, forming a nearly annular ejector trailing edge. Based on this position, the deflection angle of the adjustable trough ranges from 0° to 50°.

[0012] Furthermore, the adjustable trough corners can be appropriately rounded or chamfered to alleviate thermal stress concentration in the corners. Therefore, the cross-sectional shape of the chute is at least one of the following: rectangular, rounded rectangular, or chamfered rectangular.

[0013] The hydraulic actuator serves as a power device, outputting power to the variable geometry lobe through the transmission mechanism, thereby driving the adjustable lobe to rotate with a single degree of freedom.

[0014] The transmission mechanism comprises a connecting rod, a transmission pin, a transmission slider, a sealing cover, and a synchronizer ring. The connecting rod connects the adjustable trough to the transmission pin embedded in the transmission slider. The transmission slider is equipped with front and rear bosses that, together with the sealing cover, form a labyrinthine seal to prevent ducted airflow from escaping during variable geometry adjustment. The multiple transmission sliders are mounted on the synchronizer ring and driven by a hydraulic cylinder for synchronized axial translation, ensuring synchronized response of the variable geometry and preventing jamming.

[0015] According to the above technical solution, the outer casing wall is provided with a narrow cavity to accommodate the adjustable trough sidewall. This structure can effectively reduce the lower limit of the bypass ratio of the internal flow mode adjustment. The internal configuration of the narrow cavity is designed to fit the adjustable trough sidewall at its minimum opening.

[0016] Preferably, define th lv ,thslit are the widths of the adjustable trough sidewall and the narrow cavity, respectively. The width of the narrow cavity satisfies: 1.5≤th slit / th lv ≤3.

[0017] The intermediate casing tail is connected to the fixed crest of the variable geometry lobe.

[0018] The central cone configuration is at least one of the following: a straight-wall full cone, a straight-wall truncated cone, a curved-wall full cone, and a curved-wall truncated cone.

[0019] Compared with the prior art, the advantages of the present invention are:

[0020] 1) In the present invention, the superimposed sidewall structure composed of fixed wave crests and adjustable wave troughs can effectively expand the execution range of the variable geometry mechanism of the rear culvert ejector and increase the upper limit of the bypass ratio adjustment. The three-dimensional vortex system induced by the lobe-shaped trailing edge can significantly improve the mixing performance of the jet. As the superimposed sidewalls unfold, the flow area of ​​the outer culvert outlet gradually increases. While the ejection volume continues to increase, the range of the low-pressure area on the leeward side of the sidewall also continues to expand, and the suction and convection effects of the streamwise vortex evolved thereby are enhanced. The large-scale streamwise vortex can well promote the energy exchange between the two airflows, compensate for the increase in the mixing level caused by the increase in the bypass ratio, and further exert the advantage of the high propulsion efficiency of the large bypass ratio internal flow mode. In addition, the addition of the fixed sidewall reduces the occurrence of the vortex induced by the wave crest that is hindered by the adjustable sidewall, solving the problem of low thrust gain in the transition state.

[0021] 2) In the present invention, the sidewall receiving cavity of the outer casing can reduce the limitation of the adjustable trough from deflecting outward, helping the adjustable trough to further reduce the outer duct outlet area, thereby lowering the lower limit of the bypass ratio adjustment. In the near-vortex jet mode where the mixing performance requirements are not high, the inclusion of the adjustable trough structure can suppress the formation of complex wake vortices and reduce the mechanical energy loss of the jet to meet the aerodynamic requirements of the high-speed jet. In summary, the present invention can improve the adaptability of the rear duct ejector to wide bypass ratio conditions and greatly expand the performance matching expectations of the variable cycle.

[0022] 3) In the present invention, the actuating device is located outside the casing, and the transmission mechanism matched therewith has a simple structure and a compact form, which causes little interference to the airflow in the channel; the actuating method of the adjustable component of the ejector is simple and reliable, which facilitates the switching of the internal flow mode of the rear duct ejector and improves the maneuverability of the bypass ratio adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the overall structure diagram of the single-degree-of-freedom adjustable lobe type rear ducted ejector of the present invention.

[0024] Figure 2 It is a structural schematic diagram of the variable geometry lobe of the present invention.

[0025] Figure 3 It is a structural schematic diagram of the variable geometry lobe of the present invention when it is at its maximum opening.

[0026] Figure 4 It is a structural schematic diagram of the variable geometry lobe of the present invention when it is at an intermediate opening.

[0027] Figure 5 It is a structural schematic diagram of the variable geometry lobe of the present invention when it is at its minimum opening.

[0028] Figure 6 It is a schematic diagram of the evolution of the variable geometry lobe flow vortex of the present invention (large opening).

[0029] Figure 7 It is a schematic structural diagram of the outer casing of the present invention.

[0030] Figure 8 It is a schematic diagram of the outer casing and transmission mechanism of the present invention (small opening).

[0031] Explanation of the reference numerals: 1-variable geometry lobe; 101-fixed crest; 102-adjustable trough; 103-hinge pin; 104-slot; 105-hinge lug; 2-transmission mechanism; 201-connecting rod; 202-transmission pin; 203-transmission slider; 204-sealing cover; 205-synchronizing ring; 3-hydraulic actuator; 4-outer casing; 401-lobe side wall receiving chamber; 402-transmission window; 403-slide; 5-intermediate casing; 6-center cone. DETAILED DESCRIPTION

[0032] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0033] like Figure 1 As shown, a lobe-type rear duct ejector with modal adjustment and mixing enhancement functions includes a variable geometry lobe 1, a transmission mechanism 2, a hydraulic actuator 3, an outer casing 4, an intermediate casing 5, and a central cone 6. The variable geometry lobe 1 consists of a fixed crest 101 and an adjustable trough 102. It is located at the end of the intermediate casing 5. The structure is shown in FIG. Figure 2 The adjustable troughs 102 are rectangular troughs, 16 in number, and are mounted on the fixed crests 101 via hinge pins 103 .

[0034] The fixed crest 101 is circumferentially uniformly provided with slots 104, a number corresponding to the number of adjustable troughs 102. The slots 104 are sized to match the adjustable troughs 102, preventing circumferential vibration and gap leakage in the adjustable component. A hinged lug 105 at the front end of the adjustable trough 102 is connected to the transmission mechanism 2. Under the power output of the hydraulic jack 3, the adjustable trough 102 can deflect about the hinge pin 103, thereby changing the ejector trailing edge configuration, adjusting the outer duct outlet area and back pressure, and adjusting the low-pressure rotor speed and bypass ratio.

[0035] like Figure 3-Figure 5 As shown, the sidewalls of the fixed wave crest 101 and the adjustable wave trough 102 overlap each other and are foldable. In the turbofan mode, the adjustable wave trough 102 deflects inwards, and the lobe expansion angle reaches a maximum value.

[0036] like Figure 6 As shown in the figure, when the variable geometry lobe 1 is in a wide-open state, a local low-pressure area will form on the leeward side of the side wall. Under the combined effect of the circumferential pressure gradient near the peak / trough and the inertial force of the airflow, the secondary flow in the channel jumps over the back of the lobe side wall, causing the accumulation of low-energy fluid. The secondary flow gradually escapes the influence of the leeward side and reattaches under the action of the radial pressure gradient, forming a closed separation structure. It is driven by the mainstream and migrates, forming a stable vortex tube in the discharge trough. Subsequently, it develops into a flow vortex with a suction effect in the wake, forcing energy exchange between the cold and hot air flows, thereby accelerating the jet mixing within the shortest possible mixing length with minimal total pressure loss.

[0037] Furthermore, while maintaining the initial projected area of ​​the mixing process, the profiled trailing edge of the variable geometry lobe 1 increases the contact area between the hot and cold airflows, further enhancing the mixing performance of the ejector. Consequently, in turbofan mode, the present invention enables the energy in the turbine exhaust to be more fully transferred to the entrained airflow, thereby reducing exhaust residual velocity and heat losses, increasing the thrust gain of the ejector, and improving the variable cycle engine's propulsion efficiency and air retention capability during subsonic cruise. Furthermore, the reduced proportion of low-temperature airflow provides favorable flame stabilization conditions for the downstream afterburner.

[0038] At the same lobe height, the addition of the sidewall of the fixed peak 101 can reduce the expansion angle of the adjustable trough 102 α lv Design requirements. Figure 4 As shown, in the transition state of modal regulation, since the expansion angle satisfies: 0.4≤ α lv / ( α lp + α lv)≤0.6, and the sidewalls of the fixed crest 101 and the adjustable trough 102 essentially overlap. This prevents the sidewalls of the adjustable trough 102 from protruding beyond the crest boundary, hindering the development of the secondary flow at the tip of the valve into a crest streamwise vortex. This ensures that large-scale convective vortices can still be induced in the transitional jet wake to enhance mixing, solving the problem of poor thrust-increasing performance in the intermediate bypass ratio state.

[0039] Because the ideal mixed-emission thrust gain decreases with decreasing bypass ratio, and when a variable-cycle engine enters a near-turbojet mode with a bypass ratio below 0.2, the only low-temperature airflow in the outer shroud must be distributed to the insulation channel to cool the afterburner wall. Therefore, in the near-turbojet state, the ejector's outer shroud throttling performance should be given more attention than the jet mixing performance.

[0040] like Figure 7 As shown, a slit-shaped lobe sidewall receiving cavity 401 is provided on the wall of the outer casing 4. When the adjustable trough 102 deflects outward until the bottom surface of the groove is flush with the top surface of the fixed crest 101, part of the sidewall can be inserted into the receiving cavity 401 (as shown in FIG. Figure 8 ), thereby greatly reducing the restriction of the throttling channel on the structure of the adjustable lobe 102. With the assistance of the receiving cavity 401, the variable geometry lobe 1 can further reduce the outer duct outlet area, increase the duct back pressure, and expand the lower limit of the bypass ratio adjustment.

[0041] In order to prevent the side wall from being unable to be inserted due to tooling deviation, the width of the lobe side wall receiving cavity 401 satisfies: 1.5≤th slit / th lv ≤3. When the rear duct ejector is at its minimum opening, the annular trailing edge formed by the bottom surface of the adjustable wave 102 valley and the top surface of the fixed wave crest 101 forms the interface between the cold and hot fluids. There is no structure to induce directional flow. The spanwise vortex caused by KH instability becomes the main component of the wake turbulence, and the viscous dissipation effect of the shear layer is weakened, reducing the energy loss of the jet and ensuring the power output of the variable cycle engine for supersonic cruise.

[0042] like Figure 8 As shown, the transmission mechanism 2 and the hydraulic actuator 3 are mounted on the outer casing 4. The synchronizer ring 205 in the transmission mechanism 2 is threadedly connected to the hydraulic actuator 3 and the 16 transmission sliders 203, respectively, to maintain synchronous response to geometric adjustment. The transmission sliders 203 are constrained in the slideway 403 and can only move axially. The transmission sliders 203 are provided with front and rear bosses, which form a labyrinth seal structure with the sealing cover 204 to prevent airflow leakage during geometric adjustment. The transmission pin 201 is nested in the transmission slider 203 and connected to the connecting rod 201 through the transmission window 402. The other side of the connecting rod 201 is connected to the hinged lug on the adjustable trough 102.

[0043] Thus, the linear reciprocating motion of the hydraulic ram 3 can be converted into single-degree-of-freedom rotational motion of the adjustable trough 102. The adjustable mechanism is simple and compact, with only the connecting rod 201 and a portion of the transmission pin 201 exposed to the relatively low-temperature, low-velocity external airflow. This reduces the mechanism's interference with the flow field and lowers the material's temperature resistance requirements.

[0044] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solutions and concepts of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A lobe-type rear ducted ejector with modal adjustment and mixing enhancement functions, comprising a variable geometry lobe, a hydraulic actuator, a transmission mechanism, an outer casing, an intermediate casing, and a central cone. The intermediate casing is disposed between the outer casing and the central cone, and the transmission mechanism and hydraulic actuator are disposed externally of the outer casing. The variable geometry lobe is located at the rear of the intermediate casing and consists of fixed crests and adjustable troughs. The following features are present: The adjustable trough is a groove-shaped structure, which is installed between the grooves of the fixed wave crest through a hinge pin. The lobe sidewalls formed by this structure are a foldable structure. The transmission mechanism on the outer casing converts the linear reciprocating motion of the hydraulic actuator into the rotational motion of the adjustable trough around the hinge pin. By deflecting the adjustable trough to change the lobe trailing edge configuration, the duct outlet back pressure, duct airflow injection volume and mixing performance can be adjusted; The tail of the fixed wave crest is a zigzag periodic "П"-shaped structure, whose side walls overlap with the adjustable trough to form the side walls of the variable geometry lobe; rectangular slots are evenly arranged between the "П"-shaped structures, and the slot width is consistent with the width of the adjustable trough. A hinged joint is provided on the front side wall of the slot for mounting the adjustable trough; The cross-sectional configuration of the adjustable trough is coordinated with the fixed wave crest groove position and is at least one of the following: rectangular, rounded rectangular or chamfered rectangular; based on the minimum opening, the adjustable trough rotation adjustment range is 0°-50°; definition α lp 、 α lv are the expansion angles of the fixed crest and adjustable trough sidewalls, respectively, and the expansion angles satisfy: 0.4≤ α lv / ( α lp + α lv )≤0.6; The outer casing is provided with a narrow cavity for accommodating the adjustable trough side wall, and the internal configuration of the narrow cavity is designed to just fit into the adjustable trough side wall at the minimum opening; define th lv ,th slit are the widths of the adjustable trough sidewall and the narrow cavity, respectively. The width of the narrow cavity satisfies: 1.5≤th slit / th lv ≤3; The transmission mechanism includes a connecting rod, a transmission pin, a transmission slider, a sealing cover, and a synchronizer ring, wherein the connecting rod connects the adjustable trough with the transmission pin embedded in the transmission slider; the transmission slider is provided with front and rear bosses, forming a labyrinth seal structure with the sealing cover; multiple transmission sliders are mounted on the synchronizer ring; The outer casing is provided with a slideway and a transmission window of the transmission slider. The slideway limits the transmission slider to only axial translation. The transmission window provides a channel for the transmission mechanism provided outside the casing, and converts the translation of the transmission slider into rotation of the adjustable trough through the connecting rod mechanism.

2. The lobe-type rear ducted ejector with modal adjustment and mixing enhancement functions according to claim 1, characterized in that: A hinged lug is provided on the outer side of the front end of the adjustable trough and is connected to the transmission mechanism.

3. The lobe-type rear ducted ejector with modal adjustment and mixing enhancement functions according to claim 1, characterized in that: The central cone configuration is at least one of the following: a straight-wall full cone, a straight-wall truncated cone, a curved-wall full cone, and a curved-wall truncated cone.

4. The lobe-type rear ducted ejector with modal adjustment and mixing enhancement functions according to any one of claims 1 to 3, characterized in that: The internal flow control method of the rear duct ejector specifically includes the following steps: 1) Turbofan mode: The adjustable trough is deflected inward to the maximum lobe expansion angle position to increase the outer shroud outlet area and use the turbine's high-energy exhaust to draw more outer shroud airflow. At the same time, the local low-pressure area on the back of the sidewall induces large-scale flow-directed vortices, enhancing jet mixing. Based on the mass addition effect, the mixed-emission thrust gain is further improved, achieving lower subsonic cruise fuel consumption. 2) Near-turbojet mode: The adjustable trough deflects outward to the minimum opening of the variable geometry lobe, and the bottom surface of the adjustable trough is flush with the top surface of the fixed crest, forming a nearly annular interface between cold and hot airflows to reduce the formation of complex vortex systems in the wake, avoid excessive energy loss, and ensure the power output of the variable cycle engine for supersonic cruise.

Images