A multi-dimensional variable geometry cross-section support plate and its design method

Abstract

This invention relates to the field of ramjet engine fuel injection and discloses a multi-dimensional variable geometry cross-section support plate and its design method, including: S1, determining the length of the cross-sectional area at the connection root of the fuel injection support plate and the positioning boss as a, the thickness as b, the length of the cross-sectional area at the top of the fuel injection support plate as c, the thickness as d, and the insertion depth of the fuel injection support plate as h; S2, under the action of external force F in the combustion chamber, the thickness b should satisfy:; S3, based on the known b in S2, the thickness d should satisfy:; S4, setting the inclination angle between the windward and leeward sides of the fuel injection support plate and the base as: i To meet the requirements of the corresponding combustion chamber size, c should satisfy the following conditions. Based on the dimensional constraints of a, b, c, d, and h obtained above, the external structure of the fuel injection support plate space is obtained. The fuel injection support plate of the present invention, through a multi-dimensional variable cross-section design method, makes the fuel injection support plate more suitable for injecting fuel into large-sized combustion chambers. At the same time, the structural strength of the support plate is improved, effectively resisting the instantaneous impact of high-speed airflow.

Description

Technical Field

[0001] This invention relates to the field of ramjet engine fuel injection, and particularly to a multi-dimensional variable geometry cross-section support plate and its design method. Background Technology

[0002] In the field of ramjet engine fuel injection, the fuel injector plate is one of the important components. Currently, there are two common fuel injection methods for ramjet engines: fuel injector plate injection and wall injection. Fuel injector plate injection refers to a method where a fuel injection channel is pre-set at the corresponding position in the combustion zone, and a cavity matching the fuel injector plate is set. The fuel injector plate is inserted into the cavity, and fuel is injected into the combustion zone near the center through the internal fuel passages of the fuel injector plate and the nozzles on its surface. Wall injection refers to a method where nozzles are opened on the inner wall surface at the injection position in the combustion zone, and fuel is injected from the nozzles into the combustion zone near the inner wall surface.

[0003] Generally, wall-mounted injection is simpler, as it eliminates the need to consider flow resistance. However, the injected fuel, under the influence of the incoming flow, mostly remains near the inner wall, resulting in incomplete fuel mixing and a smaller diffusion range. It is generally suitable for smaller combustion chambers. Support plate injection, on the other hand, penetrates deeper into the combustion chamber, especially for large combustion chambers. The fuel is injected from the center of the flow field into the mainstream through a support plate. This results in more thorough mixing and a wider diffusion range, meeting the uniformity requirements of the downstream combustion flow field. However, the larger the combustion chamber diameter, the longer the support plate penetrates into the combustion chamber. Since the support plate itself is a cantilever structure, the injection process, due to unpredictable factors such as the incoming flow and fuel combustion instability, can negatively impact the structural strength, potentially causing unpredictable consequences for the ramjet engine. Therefore, support plate injection for large combustion chambers places greater demands on the structural strength of the support plate.

[0004] Existing fuel injection support structures lack corresponding designs for combustion chambers of different sizes. Typically, fuel injection support plates are rectangular structures, with adjustments made to lengthen or shorten them to accommodate different combustion chamber sizes. However, while lengthening the support plate, its thickness must be increased to ensure structural strength and stability. This increases material costs. Even with the support plate thickened to the maximum thickness required for the specified blockage ratio in larger combustion chambers, the strength requirements are still not met. Therefore, designing a three-dimensional structure for the support plate is a problem that urgently needs to be solved in the current technology. Summary of the Invention

[0005] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0006] To achieve these objectives and other advantages of the present invention, a support plate design method is provided, comprising:

[0007] S1. The cross-sectional length of the connection root of the oil spray support plate and the positioning boss is a, the thickness is b, the cross-sectional length of the top of the oil spray support plate is c, the thickness is d, and the insertion depth of the oil spray support plate is h.

[0008] Wherein, dimension a equals the combustion chamber installation opening size, and depth h satisfies... D is the diameter of the combustion chamber;

[0009] S2. Under the action of external force F in the combustion chamber, the stress at the connection root of the fuel injection support plate must meet the allowable stress of the fuel injection support plate material. Then the thickness b should satisfy: ;

[0010] S3. Based on the known value of b in S2, and assuming the fuel injection support plate satisfies the set blockage ratio i, the thickness d should satisfy: ;

[0011] In the above formula, n is the number of fuel injection support plates, and S is the aerodynamic cross-sectional area of ​​the combustion zone;

[0012] S4. Set the tilt angle between the front and rear sides of the paint spray support plate and the base as follows: θ c should satisfy Based on the dimensional constraints of a, b, c, d and h obtained above, the external shape structure of the fuel injection support plate space is obtained.

[0013] Preferably, the stress at the connection root of the fuel injection support plate is F. a F a = F1 + F2 At the same time, F a ≤ Tensile stress F1 Characterized as The bending stress F2 is characterized as .

[0014] Preferably, in S4, θ The range of values ​​is .

[0015] A multi-dimensional variable geometry cross-section support plate, used in the aforementioned support plate design method, includes: a base for supporting the fuel injection support plate, wherein the base is provided with a positioning boss that matches the external combustion chamber cavity, the fuel injection support plate is disposed above the positioning boss, and the fuel injection support plate, the positioning boss and the base are integrally formed.

[0016] The oil spray support plate has a gradually tapering shape from bottom to top, and the oil spray support plate has a diagonal wedge shape in space. The windward and leeward sides of the oil spray support plate have a rounded streamline shape. Multiple oil supply lines are arranged inside the oil spray support plate along the height direction. Multiple oil spray holes connected to each oil supply line are opened on both sides of the oil spray support plate.

[0017] Preferably, the base has an internal oil supply channel that communicates with each oil supply circuit, and the surface of the base located on one side of the oil injection support plate has an oil inlet that communicates with each oil supply channel.

[0018] The combustion chamber has an oil inlet channel on its side wall that mates with the base, which is connected to the oil inlet.

[0019] Preferably, the base and the combustion chamber are provided with multiple connection holes on their side walls, and the base and the combustion chamber are detachably connected by connecting bolts passing through the connection holes.

[0020] Preferably, the cross-section of the windward side and the cross-section of the side side of the spray plate are both isosceles trapezoids in space.

[0021] The present invention has at least the following beneficial effects: 1. The fuel injection support plate adopts a multi-dimensional variable cross-section design method, which can significantly reduce the blockage ratio under the same strength requirements, and is more conducive to reducing flow resistance and improving combustion effect;

[0022] 2. The gradually tapering support plate structure significantly improves structural strength, effectively resists the instantaneous impact of high-speed airflow, and avoids structural damage caused by pressure fluctuations that may occur during unstable fuel combustion in the test. It is more suitable for injecting fuel into large-size combustion chambers.

[0023] 3. The leading edge of the support plate is designed in a wedge shape so that the fuel and oxidant can be mixed rapidly on a macroscopic scale during fuel injection, while the aerodynamic drag and total pressure loss are kept sufficiently small. The large-scale structure and the shock wave at the leading edge of the support plate also help to enhance mixing.

[0024] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the assembly of the fuel injection support plate and the combustion chamber of the present invention;

[0026] Figure 2 This is an exploded view of the fuel injection support plate and combustion chamber assembly of the present invention;

[0027] Figure 3 This is a schematic diagram of the internal structure of the paint spray support plate;

[0028] Figure 4 This is a schematic diagram of the internal structure of the combustion chamber;

[0029] Figure 5 This is a top view of the paint spray support plate;

[0030] Figure 6 Left view of the paint spray support plate;

[0031] Figure 7 The front view and partial sectional view of the paint spray support plate;

[0032] Figure 8 This is a schematic diagram of the cross-section of the spray nozzle support plate at point AA.

[0033] Figure 9 This is a schematic diagram of the cross-section of the spray nozzle support plate at point BB.

[0034] Figure 10 This is a schematic diagram of the forces acting on the spray nozzle support plate.

[0035] Reference numerals: 1. Combustion chamber, 2. Injection support plate, 3. Base, 4. Positioning boss, 5. Fuel supply line, 6. Injection hole, 7. Fuel supply channel, 8. Fuel inlet, 9. Fuel inlet channel, 10. Sealing groove I, 11. Sealing groove II, 12. Sealing groove III, 13. O-ring seal, 14. Connecting hole, 15. Connecting bolt, 16. Annular boss, 17. Combustion chamber cavity. Detailed Implementation

[0036] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0037] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0038] It should be noted that in the description of this invention, the orientation or positional relationship indicated by the terms is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. It does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0039] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installed", "equipped", "sleeved / connected", "connected", etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0040] Furthermore, in this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Moreover, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0041] A support plate design method of the present invention includes:

[0042] S1. The cross-sectional length of the connection root of the oil spray support plate 2 and the positioning boss 4 is a, the thickness is b, the cross-sectional length of the top of the oil spray support plate 2 is c, the thickness is d, and the insertion depth of the oil spray support plate 2 is h.

[0043] Wherein, dimension a equals the installation opening dimension of combustion chamber 1, and depth h satisfies D is the diameter of combustion chamber 1;

[0044] S2. Under the action of external force F in combustion chamber 1, the stress on the connection root of fuel injection support plate 2 must meet the allowable stress of fuel injection support plate 2 material. Then the thickness b should satisfy: ;

[0045] S3. Based on the known value of b in S2, and given that the fuel injection support plate 2 satisfies the set blockage ratio i, the thickness d should satisfy: ;

[0046] In the above formula, n is the number of spray nozzles 2;

[0047] S4. Set the tilt angle between the front and back surfaces of the spray nozzle 2 and the base 3 as follows: θ , c Should meet Based on the dimensional constraints of a, b, c, d and h obtained above, the external shape structure of the space of the oil spray support plate 2 is obtained.

[0048] Working principle:

[0049] S1, the depth h of the support plate inserted into combustion chamber 1, the geometric dimensions a and thickness b of the upper section AA, and the geometric dimensions c and thickness d of the lower section BB. An isosceles trapezoid is proposed with upper base d, lower base b, and height h as the insertion depth. The force on the windward side is F, and the aerodynamic cross-sectional area of ​​the combustion zone is S.

[0050] S2. According to the stress analysis of the support plate, the stress at the lower section is the greatest. Determine the geometric dimensions of the lower section BB of the support plate. The stress σ at the lower section BB is related to the material, cross-sectional shape, and external force F of the support plate. The cross-section of the lower section BB is roughly rectangular with an area of ​​a×b. According to the material mechanical strength design conditions, the stress at the lower section BB satisfies F / (a×b)+(F / 2h) / (ab). 2 / 6)≤[σ]. The length a is determined based on the installation opening size of combustion chamber 1. The insertion depth h is related to the diameter of combustion chamber 1, and the insertion depth h = D / 2 - 10. The allowable stress [σ] is a physical property of the material, and its value is determined under certain working conditions. Therefore, the thickness b should satisfy ah[σ] b 2 -Fhb-3F≤0;

[0051] S3. In order to obtain a smaller flow resistance into combustion chamber 1 and meet the structural strength safety factor of the support plate, i is subject to certain restrictions, usually i≤12%; according to the above steps, i=n(d+b)h / 2S, the thickness d should satisfy: d≤0.24S / nh-b;

[0052] S4. Given that the geometric dimension 'a' is determined based on the installation opening size of combustion chamber 1, and to meet the requirements for bracket installation and fuel injection, 50° ≤ θ ≤80° θ The tilt angles of the spray plate 2 (facing and leeward sides) relative to the base 3 can be further derived. ;

[0053] Geometric dimension a is determined by the opening size of the support plate at its mounting location in combustion chamber 1, and geometric dimensions b, c, and d respectively satisfy... , and This is to ensure that the structural strength of the fuel injection support plate 2 meets the operating requirements of combustion chambers 1 of different sizes.

[0054] Figures 1-10 A multi-dimensional variable geometry cross-section support plate is shown and used in the support plate design method, including: a base 3 for supporting the fuel injection support plate 2, the base 3 is provided with a positioning boss 4 that matches the external combustion chamber cavity 17, and the fuel injection support plate 2 is positioned above the positioning boss 4.

[0055] The oil spray support plate 2 has a gradually tapering shape from bottom to top, and the windward and leeward sides of the oil spray support plate 2 have a rounded streamline shape. Multiple oil supply lines 5 are arranged inside the oil spray support plate 2 along the height direction, and multiple oil spray holes 6 are opened on both sides of the oil spray support plate 2, which are connected to each oil supply line 5.

[0056] Working principle:

[0057] The fuel injection support plate 2 is installed and positioned by the positioning boss 4 on the base 3 and the combustion chamber cavity 17, so that the fuel injection support plate 2 is inserted into the combustion chamber 1. At the same time, the gradual contraction structure from the bottom surface to the top surface of the fuel injection support plate 2 and the arc-shaped streamline shape of the windward and leeward sides, combined with the insertion depth designed according to the diameter of the combustion chamber 1, can reduce the incoming flow resistance and adapt to the airflow characteristics under different working conditions. Meanwhile, multiple fuel supply lines 5 arranged along the height direction inside deliver fuel to multiple fuel injection holes 6 on both sides of the support plate to complete the injection. Each fuel supply line 5 is not a standard circular channel, but a fuel channel with a similar expansion trend as the support plate, extending to the top of the positioning boss 4. The fuel passes through the corresponding fuel supply line 5 inside the support plate and is then sprayed out from the injection hole into the combustion chamber 1 to complete the subsequent mixing and combustion process.

[0058] In the above scheme, the base 3 has an oil supply channel 7 that is connected to each oil supply line 5 inside, and the surface of the base 3 located on the side of the oil injection support plate 2 has an oil inlet 8 that is connected to each oil supply channel 7.

[0059] In this invention, an oil inlet channel 9 communicating with the oil inlet 8 is provided on the side wall of the combustion chamber 1 where it mates with the base 3. Traditionally, the oil inlet channel 9 is located at the bottom of the injection support plate 2. When the injection system is damaged, the external oil inlet pipe and support plate must be removed to remove the injection support plate 2 and replace it, making the replacement process very cumbersome. In this invention, the oil inlet channel 9 is located on the side wall of the combustion chamber 1. A sealing groove I10 is provided at the point where the surface of the combustion chamber cavity 17 mates with the positioning boss 4. A sealing groove II11 is provided on the surface of the side wall of the combustion chamber 1 where it mates with the base 3. A sealing groove III12 is provided at the point where the side wall of the combustion chamber 1 mates with the oil inlet 8. Each of the 8 oil inlets is equipped with an annular boss 16 that extends into the sealing groove Ⅲ12. Each sealing groove Ⅰ10, sealing groove Ⅱ11 and sealing groove Ⅲ12 is equipped with an O-ring 13. At the same time, the connection between the support plate and the combustion chamber 1 is ensured by the connection hole 14 and the connecting bolt 15 between the base 3 and the combustion chamber 1. The connecting bolt 15 presses the O-ring 13, so that the support plate and the combustion chamber 1 achieve a three-level seal, ensuring the sealing effect during oil supply. In addition, if the support plate is damaged, it can be replaced without removing the oil supply line, which speeds up the replacement speed and improves the efficiency of the work.

[0060] In the above technical solution, the frontal and side cross-sections of the fuel injection support plate 2 are both isosceles trapezoids in space. This design, with the two sides of the isosceles trapezoid symmetrically inclined, can further optimize the guiding path of the incoming airflow, avoiding airflow deflection or local vortices caused by cross-sectional asymmetry, and significantly reducing aerodynamic drag. The side isosceles trapezoid, through the difference in size between the upper and lower bases, creates a uniform inclined transition on the side of the support plate. This provides a stable base for the arrangement of the fuel injection holes 6 on both sides, ensuring that the injection direction of the fuel injection holes 6 at different heights matches the airflow direction of the combustion chamber 1, improving fuel atomization and mixing efficiency, and also enhances the mechanical stability of the trapezoidal structure.

[0061] The fuel injection support plate 2 has a positioning surface below it that matches the shape of the combustion chamber cavity 17. The positioning surface on the fuel injection support plate 2 ensures that the support plate can be inserted smoothly, and at the same time makes the connection between the fuel injection support plate 2 and the combustion chamber cavity 17 more stable.

[0062] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A design method for a multi-dimensional variable geometry cross-section support plate, characterized in that, The multi-dimensional variable geometry cross-section support plate comprises a base for supporting an oil injection support plate, wherein a positioning boss matched with an external combustion chamber cavity is arranged on the base, and the oil injection support plate is arranged above the positioning boss, and the oil injection support plate, the positioning boss and the base are integrally arranged. The oil injection support plate is gradually tapered from a bottom surface to a top surface, so that the oil injection support plate is in a space oblique wedge shape, the windward and leeward surfaces of the oil injection support plate are in a circular arc streamline shape, a plurality of oil supply oil paths are arranged in the oil injection support plate along a height direction, and a plurality of oil injection holes in communication with the oil supply oil paths are arranged on both side surfaces of the oil injection support plate. The multi-dimensional variable geometry cross-section support plate design method comprises the following steps: S1, the connecting root cross-section length of the oil injection support plate and the positioning boss is a, the thickness is b, the top cross-section length of the oil injection support plate is c, the thickness is d, and the oil injection support plate insertion depth is h; wherein the dimension a is equal to the size of the combustion chamber mounting opening, and the depth h is such that D is the diameter of the combustion chamber. S2, under the action of the external force F, the stress borne by the connecting root of the oil injection branch plate needs to meet the allowable stress of the oil injection branch plate material Therefore, the thickness b should meet: ; S3, by S2 known b, while the oil spray branch plate meet set blockage ratio i, thickness d should meet: ; In the above formula, n is the number of oil injection support plates, S is the aerodynamic profile cross-sectional area of the combustion zone, and θ is the angle between the oil injection support plate and the positioning boss. S4, set the inclination angle of the windward and leeward surface of the oil injection branch plate and the base to be The bottom surface of the oil injection support plate is in a circular arc shape, and the top surface of the oil injection support plate is in a circular arc shape. , the length c is obtained by , based on the size constraints of a, b, c, d and h obtained by the above method, the shape structure of the oil injection branch plate space is obtained.

2. The multi-dimension variable geometry strake design method according to claim 1, wherein, In S2, the stress of the connecting root of the oil injection branch plate is F a , F a = F1 + F2 , F a ≤ , the tensile stress F1 is represented as , and the bending stress F2 is represented as .

3. The multi-dimension variable geometry strake design method according to claim 1, wherein, In S4, A plurality of oil supply channels in communication with the oil supply oil paths are arranged in the base, and an oil inlet in communication with the oil supply channels is arranged on the surface of the base on one side of the oil injection support plate. the value range of .

4. The multi-dimension variable geometry strake design method according to claim 1, wherein, The side wall of the combustion chamber matched with the base is provided with an oil inlet channel in communication with the oil inlet. A plurality of connecting holes are arranged on the side wall of the base and the combustion chamber, and the base and the combustion chamber are detachably connected through connecting bolts penetrating the connecting holes.

5. The multi-dimension variable geometry strake design method according to claim 1, wherein, The windward surface cross-section and the side surface cross-section of the oil injection support plate are isosceles trapezoidal in space.

6. The multi-dimension variable geometry strake design method according to claim 1, wherein, ​

Images