Integrated design method and structure of afterburner chamber for variable cycle engine

Abstract

The present invention discloses an integrated design method and structure for a variable cycle engine afterburner combustion chamber, including establishing a first correspondence between the number of lobes of a rear duct ejector and the number of flame-stabilizing support plates, and establishing a second correspondence between the number of lobes of a rear duct ejector and the number of series-connected trapped vortex cavities; obtaining the number of flame-stabilizing support plates based on the first correspondence; constructing a flame-stabilizing groove at the trailing edge of each integrated flame-stabilizing support plate; and calculating the relative thickness of the integrated flame-stabilizing support plate airfoil and the depth of the flame-stabilizing groove based on the chord length of the flame-stabilizing support plate. The flame-stabilizing support plate is a conformal design based on a symmetrical airfoil and is arranged downstream of the crest discharge. It can fully utilize the high-temperature exhaust gas of the turbine to induce backflow at the rear of the support plate to capture the oil-gas mixture and organize reaction combustion, while minimizing flow resistance loss and flow field interference, thereby reducing the blockage ratio.

Description

Technical Field

[0001] The present invention relates to the technical field of engine afterburner chambers, and in particular to an integrated design method and structure of a variable cycle engine afterburner chamber. Background Art

[0002] Variable cycle engines can balance low fuel consumption in subsonic cruise with high maneuverability and high thrust in supersonic flight by adjusting the bypass ratio, and are an important direction for the development of next-generation engines. The ducted ejector is a key component for variable cycle engines to achieve a variable bypass ratio. Among them, the rear ducted ejector is one of the core components of modal adjustment and can be regarded as a structurally adjustable mixer. In engineering practice, the lobe mixer structure has good application prospects in the rear ducted ejector because it can effectively enhance mixing and has a relatively simple configuration. The modal adjustment function of the ducted ejector can assist the variable cycle power to adapt to various flight conditions and combat missions, but the variable working modes and the need to adapt to the upstream lobe mixer also bring more challenges to the design of the afterburner.

[0003] Due to the shortcomings of traditional afterburner combustion chambers, such as complex component composition, high blockage ratio, bulky structure, and poor flow pattern adaptability, they are increasingly unable to meet the growing performance requirements of advanced propulsion systems. For the bearing support plate and flame stabilizer components in the afterburning system, the blunt body backflow they generate will inevitably interact with the jet, causing additional aerodynamic losses. However, within the flight envelope, the duration of afterburner engagement is much shorter than the duration of normal operation of the mixed-flow ejector system. Therefore, the design of the afterburning flame stabilizer components should avoid optimizing at the expense of the normal aerodynamic performance of the rear duct ejector. Consideration should be given to integrating the bearing support plate and flame stabilizer components to simplify the mixed-flow / afterburning system structure and reduce flow resistance.

[0004] Secondly, the variable cycle power afterburning system has a large range of variation in the ratio of internal and external flow, radial direction, temperature, and oxygen content distribution. These harsh operating conditions have an adverse impact on efficiency improvement, significantly increasing the design difficulty of the variable cycle power mixed exhaust / afterburning system (especially the turbofan mode). During the design process, the layout of the flame stabilizer must match the flow pattern of the typical mode, and the respective combustion-supporting advantages of the two jets must be rationally utilized to organize the flame for efficient combustion in different zones, minimizing the restrictions on the use of afterburner in the variable cycle mission profile. Therefore, an integrated design method and structure for the afterburner combustion chamber of a variable cycle engine is proposed. Summary of the Invention

[0005] The technical problem solved by the present invention is that the traditional afterburner has the disadvantages of complex component composition, high blockage ratio, bulky structure and poor flow pattern adaptability, and is increasingly unable to meet the growing performance requirements of advanced power.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for integrated design of a variable cycle engine afterburner combustion chamber, comprising establishing a first correspondence between the number of lobes of the rear duct ejector and the number of flame stabilizing support plates, and establishing a second correspondence between the number of lobes of the rear duct ejector and the number of series-connected trapped vortex cavities; obtaining the number of flame stabilizing support plates according to the first correspondence; constructing a flame stabilizing groove at the trailing edge of each integrated flame stabilizing support plate; calculating the relative thickness of the integrated flame stabilizing support plate airfoil and the relative depth of the flame stabilizing groove according to the chord length of the flame stabilizing support plate; and obtaining the number of series-connected trapped vortex cavities according to the second correspondence.

[0007] As a preferred solution of the integrated design method of the variable cycle engine afterburner chamber according to the present invention, the first corresponding relationship includes one of the following: the number of flame stabilizing support plates is the same as the number of lobes of the rear duct ejector, or the number of flame stabilizing support plates is a factor of the number of lobes of the rear duct ejector.

[0008] As a preferred solution of the integrated design method of the variable cycle engine afterburner chamber according to the present invention, the flame stabilizing groove is constructed at the trailing edge of each integrated flame stabilizing support plate, including:

[0009] The middle of the trailing edge of the integrated flame stabilizing support plate is taken as point O, and an ellipse with a major axis of 2a and a minor axis of 2b is generated with point O as the center. The trailing edge of the integrated flame stabilizing support plate is trimmed to form a flame stabilizing groove with a width of w and a depth of d.

[0010] As a preferred solution of the integrated design method of the variable cycle engine afterburner chamber according to the present invention, the relative thickness of the integrated flame stabilizing support plate airfoil is calculated based on the chord length of the flame stabilizing support plate, and the calculation expression is:

[0011] θ=t / l

[0012] Wherein, θ represents the relative thickness of the integrated flame stabilizing support plate airfoil, t represents the maximum thickness of the support plate, and l represents the chord length of the flame stabilizing support plate.

[0013] As a preferred solution of the integrated design method of the variable cycle engine afterburner chamber according to the present invention, the relative depth of the flame stabilizing groove is calculated according to the chord length of the flame stabilizing support plate, and the calculation expression is:

[0014] β=d / l

[0015] Wherein, β represents the depth of the flame stabilizing groove, and d represents the depth of the groove behind the flame stabilizing support plate.

[0016] As a preferred solution of the integrated design method of the variable cycle engine afterburner chamber according to the present invention, the second corresponding relationship includes one of the following: the number of lobes of the rear duct ejector is the same as the number of series trapped vortex cavities or the number of series trapped vortex cavities is a factor of the number of lobes of the rear duct ejector.

[0017] As a preferred solution of the integrated design method of the variable cycle engine afterburner chamber according to the present invention, the series trapped vortex cavity includes a front trapped vortex cavity and a rear trapped vortex cavity, the height of the partition between the front trapped vortex cavity and the rear trapped vortex cavity is H, and the height of the partition in front of the front trapped vortex cavity is 0.5H.

[0018] As a preferred solution for the integrated structure of the afterburner combustion chamber of the variable cycle engine described in the present invention, it includes a flame stabilizing support plate, the top of which is fixedly connected to the outer casing, the cross-section of the integrated flame stabilizing support plate is a NACA airfoil, and a groove is provided at the trailing edge of the airfoil, which serves as a gas reflux area.

[0019] As a preferred solution for the integrated structure of the afterburner combustion chamber of the variable cycle engine described in the present invention, the flame stabilizing support plates are evenly arranged circumferentially downstream of the rear duct ejector, and the circumferential position of the flame stabilizing support plates is opposite to the peak discharge of the lobe of the rear duct ejector.

[0020] The beneficial effects of the present invention are as follows: the flame stabilizing support plate is conformally designed on the basis of the symmetrical airfoil, and is arranged downstream of the wave crest discharge. It can make full use of the high-temperature exhaust gas of the turbine to induce backflow at the tail of the support plate to capture the oil-gas mixture and organize reaction combustion, under the premise of minimizing the flow resistance loss and reducing the flow field interference, which is beneficial to reducing the blockage ratio. For low-temperature bypass airflow with different pitch angles (especially in the large bypass ratio state), the residence time of the oil and gas components in the partition is increased and the accumulation of ignition energy is improved by arranging an integrated series trapped vortex cavity on the heat shield of the outer ring partition. In this way, the problems of diversified internal flow modes of the variable cycle mixed afterburner system at different bypass ratios, the inability of the traditional flame stabilizer to always match the flow pattern, and the difficulty in organizing the combustion of the external bypass airflow at a large bypass ratio are specifically solved, thereby meeting the growing performance requirements of advanced power. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of the basic flow of an integrated design method and structure for a variable cycle engine afterburner chamber provided by one embodiment of the present invention.

[0022] Figure 2 A schematic diagram of the integrated structure of a variable cycle afterburner combustion chamber in a variable cycle engine afterburner combustion chamber integrated design method and structure provided in one embodiment of the present invention.

[0023] Figure 3A schematic diagram of a flame stabilizing support plate for an integrated design method and structure of an afterburner combustion chamber of a variable cycle engine provided by one embodiment of the present invention.

[0024] Figure 4 A schematic diagram of the flame front distribution of a flame stabilizing support plate of an integrated design method and structure for a variable cycle engine afterburner provided in one embodiment of the present invention.

[0025] Figure 5 A schematic diagram of a series trapped vortex cavity of an integrated design method and structure for a variable cycle engine afterburner provided by one embodiment of the present invention.

[0026] Figure 6 A schematic diagram of the fire front distribution of a series trapped vortex cavity in an integrated design method and structure for a variable cycle engine afterburner provided by one embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings. It is obvious that the described embodiments are only part of the embodiments of the present invention, but not all of the embodiments.

[0028] Example 1, with reference to Figure 1-6 , as one embodiment of the present invention, provides a method for integrated design of a variable cycle engine afterburner chamber, comprising:

[0029] Step S1, establishing a first correspondence between the number of lobes of the rear duct ejector and the number of flame stabilizing support plates, and establishing a second correspondence between the number of lobes of the rear duct ejector and the number of series-connected trapped vortex cavities;

[0030] The first corresponding relationship includes one of the following: the number of flame stabilizing support plates is the same as the number of lobes of the rear duct ejector, or the number of flame stabilizing support plates is a factor of the number of lobes of the rear duct ejector.

[0031] The second corresponding relationship includes one of the following: the number of lobes of the rear duct ejector is the same as the number of the series trapped vortex cavities, or the number of the series trapped vortex cavities is a factor of the number of lobes of the rear duct ejector.

[0032] Step S2, obtaining the number of flame stabilizing support plates according to the first corresponding relationship;

[0033] The first corresponding relationship includes one of the following: the number of flame stabilizing support plates is the same as the number of lobes of the rear duct ejector, or the number of flame stabilizing support plates is a factor of the number of lobes of the rear duct ejector.

[0034] Step S3, constructing a flame stabilizing groove at the trailing edge of each integrated flame stabilizing support plate;

[0035] The flame stabilizing grooves constructed at the trailing edge of each integrated flame stabilizing support plate include:

[0036] The middle of the trailing edge of the integrated flame stabilizing support plate is taken as point O, and an ellipse with a major axis of 2a and a minor axis of 2b is generated with point O as the center. The trailing edge of the integrated flame stabilizing support plate is trimmed to form a flame stabilizing groove with a width of w and a depth of d.

[0037] Step S4, calculating the relative thickness of the integrated flame stabilizing support plate airfoil and the relative depth of the flame stabilizing groove according to the chord length of the flame stabilizing support plate;

[0038] The relative thickness of the integrated flame stabilizing support plate airfoil is calculated based on the chord length of the flame stabilizing support plate, and the calculation expression is:

[0039] θ=t / l

[0040] Wherein, θ represents the relative thickness of the integrated flame stabilizing support plate airfoil, t represents the maximum thickness of the support plate, and l represents the chord length of the flame stabilizing support plate.

[0041] Increasing the relative thickness (t / l) of the flame stabilization plate has a relatively greater impact on the mixing efficiency in the turbojet mode. This is because thickening the flame stabilization plate also blocks the inlet space of the heat shield, hindering the intake of the cooling channel. This blockage has a greater impact on the amount of cooling air that remains unmixed in the turbojet mode. Furthermore, the annular shape of the intermediate casing trailing edge in the turbojet mode weakens the mixing capacity of the ejector, making mixing efficiency more sensitive to changes in relative thickness. Regarding combustion efficiency, a decrease in t / l limits the development of the flame stabilization zone behind the column, hindering flame propagation and diffusion and hindering the release of reaction energy. In the turbofan mode, combustion efficiency decreases dramatically. While increasing t / l may improve combustion organization, it also exacerbates the degradation of airflow energy quality. Increasing the thickness of the flame stabilization plate not only causes expansion of the near-wall flow, increasing friction with the solid wall, but also increases turbulence in the recirculation zone wake, enhancing the interaction between the wake and the jet vortex system and increasing viscous dissipation. This phenomenon is particularly prominent in the turbofan mode with a complex vortex system.

[0042] Because the strength and extent of the recirculation zone determine the flame-stabilizing groove's ability to capture the oil-gas mixture and compensate for the consumption of reactive components, using a flame-stabilizing plate configuration with too small a thickness will reduce the efficiency of the lateral mass-energy exchange in the reaction zone. However, as the t / l of the flame-stabilizing plate increases, the expansion of the recirculation zone gradually slows, and its positive effect on flame stabilization is offset by increasing friction and resistance losses. Therefore, under reasonable oil-gas organization, appropriately increasing the relative thickness of the flame-stabilizing plate can more effectively promote combustion.

[0043] The depth of the flame stabilizing groove is calculated according to the chord length of the flame stabilizing support plate, and the calculation expression is:

[0044] β=d / l

[0045] Wherein, β represents the depth of the flame stabilizing groove, and d represents the depth of the groove behind the flame stabilizing support plate.

[0046] When afterburner is activated and the profile of the leeward surface of the flame-stabilizing support plate is concave, the turbulent effect in the near-wall area will be weakened. Since the time-averaged velocity and turbulent energy of the fluid in this area are both at low levels, this area is described as a stagnation zone of flow. Furthermore, as the relative depth d / l of the flame-stabilizing groove of the flame-stabilizing support plate increases, the scope and proportion of the stagnation zone in the recirculation will gradually expand. At the end of the recirculation, there is also an area of ​​turbulent energy accumulation with flow characteristics opposite to those of the stagnation zone. When d / l is less than 0.1, the influence range of this turbulent zone will continue to expand as d / l increases. When d / l exceeds 0.1 and the groove depth continues to increase, the turbulent accumulation area will be affected by the adjacent continuously expanding stagnation zone and will no longer expand.

[0047] like Figure 4 As shown in the figure, after the flame stabilization zone is formed on the flame stabilization support plate, the flame will propagate downstream separately based on the oil and gas distribution on both sides of the flame stabilization support plate. During this process, the supply of components from the backflow to the reaction core gradually weakens, and the reaction zone narrows at the flame bifurcation point. When d / l increases from 0.0 to 0.15, the contraction amplitude gradually decreases with the increase in d / l. This indicates that flame propagation capability is enhanced as the turbulence intensity at the end of the backflow increases. The relative depth d / l of the groove at the tail of the flame stabilization support plate should be between 0.06 and 0.15.

[0048] Step S5: Obtain the number of series-connected trapped vortex cavities according to the second corresponding relationship.

[0049] The second corresponding relationship includes one of the following: the number of lobes of the rear duct ejector is the same as the number of the series trapped vortex cavities, or the number of the series trapped vortex cavities is a factor of the number of lobes of the rear duct ejector.

[0050] The series trapped vortex cavity comprises a front trapped vortex cavity and a rear trapped vortex cavity, a height of a partition between the front trapped vortex cavity and the rear trapped vortex cavity is H, and a height of a partition in front of the front trapped vortex cavity is 0.5H.

[0051] The flame stabilizing support plate is a conformal design based on the symmetrical airfoil. It is arranged downstream of the wave crest discharge. It can fully utilize the high-temperature exhaust gas of the turbine to induce backflow at the tail of the support plate to capture the oil-gas mixture and organize reaction combustion, while minimizing the flow resistance loss and reducing the flow field interference. For low-temperature bypass airflow with different pitch angles (especially in the case of large bypass ratio), the integrated series trapped vortex cavity is arranged on the heat shield of the outer ring partition to increase the residence time of the oil and gas components in the partition and improve the accumulation of ignition energy. In this way, the problems of diversified internal flow modes of the variable cycle mixed afterburner system at different bypass ratios, the inability of traditional flame stabilizers to always match the flow pattern, and the difficulty in organizing the combustion of the external bypass airflow at large bypass ratio are specifically solved.

[0052] Example 2, reference Figure 2-5 , which is another embodiment of the present invention. This embodiment is different from the first embodiment in that it provides an integrated structure of a variable cycle engine afterburner combustion chamber including a flame stabilizing support plate. The top of the flame stabilizing support plate is fixedly connected to the outer casing. The cross-section of the integrated flame stabilizing support plate is a NACA airfoil. A groove is provided at the trailing edge of the airfoil, and the groove serves as a gas recirculation area.

[0053] The flame stabilizing support plates are evenly arranged circumferentially downstream of the rear duct ejector, and the circumferential position of the flame stabilizing support plates is opposite to the crest discharge flow of the rear duct ejector lobe.

[0054] Reference Figure 2-4 The flame-stabilizing support plate, integrated with the coupling support plate and flame stabilizer, is located downstream of the aft duct ejector lobe. Its shape is an airfoil, with a groove on the trailing edge serving as a gas recirculation zone. The number of flame-stabilizing support plates is equal to or a multiple of the number of aft duct ejector lobes. These flame-stabilizing support plates are evenly spaced circumferentially downstream of the aft duct ejector lobe, aligning with the crest discharge flow of the upstream aft duct ejector lobe.

[0055] Reference Figure 2 and 5 A coupled heat shield and series-connected trapped vortex cavities are located downstream of the aft duct ejector lobes. The number of series-connected trapped vortex cavities is equal to or a multiple of the number of aft duct ejector lobes. The cavities are evenly spaced circumferentially downstream of the aft duct ejector. The circumferential position of the trapped vortex cavities is limited by the flame-stabilizing support plate, and the trough discharge is directed directly toward the upstream lobe.

[0056] It should be appreciated that embodiments of the present invention can be implemented or practiced by a combination of computer hardware and software, or by computer instructions stored in a non-transitory computer-readable memory. The methods can be implemented in a computer program using standard programming techniques, including a non-transitory computer-readable storage medium configured with a computer program, wherein the storage medium so configured causes the computer to operate in a specific and predefined manner, according to the methods and figures described in the specific embodiments. Each program can be implemented in a high-level procedural or object-oriented programming language to communicate with the computer system. However, if desired, the program can be implemented in assembly or machine language. In any case, the language can be a compiled or interpreted language. In addition, the program can be run on a programmed application-specific integrated circuit for this purpose.

[0057] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for integrated design of a variable cycle engine afterburner chamber, characterized in that: The flame stabilizing support plates are evenly arranged circumferentially downstream of the rear duct ejector, and the circumferential position of the flame stabilizing support plates is directly opposite to the crest discharge of the rear duct ejector lobe. An integrated series trapped vortex cavity is arranged on the heat shield of the outer ring partition, including: Step S1, establishing a first correspondence between the number of lobes of the rear duct ejector and the number of flame stabilizing support plates, and establishing a second correspondence between the number of lobes of the rear duct ejector and the number of series-connected trapped vortex cavities; Step S2, obtaining the number of flame stabilizing support plates according to the first corresponding relationship; Step S3, constructing a flame stabilizing groove at the trailing edge of each integrated flame stabilizing support plate; Step S4, calculating the relative thickness of the integrated flame stabilizing support plate airfoil and the relative depth of the flame stabilizing groove according to the chord length of the flame stabilizing support plate; Step S5, obtaining the number of series-connected trapped vortex cavities according to the second corresponding relationship; The first corresponding relationship includes one of the following: the number of flame stabilizing support plates is the same as the number of lobes of the rear duct ejector, or the number of flame stabilizing support plates is a factor of the number of lobes of the rear duct ejector; The relative thickness of the integrated flame stabilizing support plate airfoil is calculated based on the chord length of the flame stabilizing support plate, and the calculation expression is: θ = t / l, where θ represents the relative thickness of the integrated flame stabilizing support plate airfoil, t represents the maximum thickness of the support plate, and l represents the chord length of the flame stabilizing support plate; The relative depth of the flame stabilizing groove is calculated based on the chord length of the flame stabilizing support plate. The calculation expression is: β = d / l, where β represents the depth of the flame stabilizing groove, and d represents the depth of the groove at the rear of the flame stabilizing support plate. The relative depth d / l of the groove at the rear of the flame stabilizing support plate should be 0.06 to 0.15; The second corresponding relationship includes one of the following: the number of lobes of the rear ducted ejector is the same as the number of the series-connected trapped vortex cavities, or the number of the series-connected trapped vortex cavities is a factor of the number of lobes of the rear ducted ejector; The series trapped vortex cavity comprises a front trapped vortex cavity and a rear trapped vortex cavity, a height of a partition between the front trapped vortex cavity and the rear trapped vortex cavity is H, and a height of a partition in front of the front trapped vortex cavity is 0.5H.

2. The method for integrated design of a variable cycle engine afterburner chamber according to claim 1, characterized in that: Constructing a flame-stabilizing groove at the trailing edge of each integrated flame-stabilizing support plate includes: taking the middle of the trailing edge of the integrated flame-stabilizing support plate as point O, generating an ellipse with a major axis of 2a and a minor axis of 2b with point O as the center, and trimming the trailing edge of the integrated flame-stabilizing support plate to form a flame-stabilizing groove with a width of w and a depth of d.

3. A variable cycle engine afterburner integrated structure, using the variable cycle engine afterburner integrated design method according to any one of claims 1-2, characterized in that: It comprises a flame stabilizing support plate, the top of which is fixedly connected to the outer casing. The cross section of the integrated flame stabilizing support plate is a NACA airfoil. A groove is provided on the trailing edge of the airfoil, and the groove serves as a gas reflow zone.

Images