A nozzle structure with variable expansion ratio and a solid rocket motor

Abstract

This invention provides a nozzle structure with a variable expansion ratio, including a nozzle section and multiple expansion sections. The nozzle section and expansion sections, as well as adjacent expansion sections, are connected by a detachable connection mechanism. The detachable connection mechanism includes a fixing member and a propellant. The fixing member is connected to two corresponding structural components at both ends. The propellant is located on the gas injection path at the nozzle section outlet. The propellant is used to burn and melt the fixing member, generating high-temperature gas that separates the two structural components connected by the fixing member. This invention designs multiple expansion sections and uses a detachable connection mechanism to allow each expansion section to separate at a preset time, thereby changing the nozzle outlet size and thus the nozzle expansion ratio. This ensures that each stage of the multi-stage high-thrust engine operates under optimal expansion ratio conditions, maximizing energy utilization.

Description

Technical Field

[0001] This invention belongs to the field of solid rocket technology, specifically relating to a nozzle structure with a variable expansion ratio and a solid rocket engine. Background Technology

[0002] To meet tactical requirements, solid rocket motors for air-to-air and air-to-ground missiles often employ a high thrust-to-weight ratio internal trajectory design. The conventional approach for these engines is a multi-stage engine sharing a common nozzle. As the working principle of solid rocket motors shows, for a multi-stage, high-thrust-ratio engine to achieve maximum efficiency, each stage must fully expand during operation. Therefore, each stage has a different optimal expansion ratio. However, the expansion ratio (the ratio of the nozzle exit area to the throat area) of a conventional nozzle is a fixed value. Conventional nozzle structures can only guarantee that one stage in a multi-stage, high-thrust-ratio engine reaches full expansion during operation, inevitably resulting in energy loss. The higher the thrust ratio of each stage, the more severe the energy loss.

[0003] In order to ensure that each stage of a multi-stage high thrust ratio engine operates under the optimal expansion ratio condition, according to the formula definition of expansion ratio, it can be achieved through the following methods: (1) fix the throat diameter and change the nozzle exit size by moving or ablating part of the expansion section; (2) fix the nozzle exit and adjust the nozzle throat diameter to change the expansion ratio.

[0004] For fixed-throat nozzles, the moving expansion section nozzle design has the following problems: (a) The auxiliary system is complex and occupies a large space; completing the movement of the expansion section requires a complete set of complex auxiliary devices, including energy systems, electronic control systems, actuation systems, and fixed auxiliary structures. Therefore, the nozzle area requires a large space, making it unsuitable for small solid rocket engines. (b) High sealing requirements and limited application; to ensure the mobility of the expansion section and the sealing of the structure, the moving expansion section can only use sheet-like high-temperature resistant alloys with good ductility (such as niobium alloys), which are stacked layer by layer using a hinged method. Currently, the allowable temperature of commonly used high-temperature alloys does not exceed 1500℃, while the gas temperature in the expansion section area of ​​a typical solid rocket engine is between 1800℃ and 2200℃. Therefore, this method is currently only applicable to liquid engines and cannot be applied to solid rocket engines with higher gas temperatures. (c) Due to the molding process and the mechanical properties of the materials themselves, conventional insulation materials cannot be made into hinged thin sheet structures. Therefore, when using conventional insulation materials to prepare the moving expansion section, the continuity of the internal surface cannot be guaranteed, resulting in energy loss.

[0005] For a fixed throat diameter, the ablation expansion section nozzle design has the following problems: (a) The expansion ratio change time cannot be precisely controlled; the degree of melting and morphology of the material are greatly affected by the engine operating conditions, so the time required for the ablation expansion section to go from the start of ablation to complete melting is inconsistent, with many uncertainties, which is not conducive to system control. (b) Poor thrust output consistency; due to the uncertainty of the material melting process, the expansion section profile is uncertain, which leads to uncertainty in the direction and magnitude of the engine's output thrust, causing control difficulties and energy waste, and more seriously, it can lead to missile malfunction.

[0006] The following problems exist with variable throat diameter nozzle schemes: (a) The research and application of throat plug type variable throat diameter is relatively mature, but the throat plug structure and its servo mechanism determine that this method is only applicable to engines with internal hole propellant loading structure, and the engine length should not be too long, thus limiting the scope of application; (b) Fluid throat variable throat diameter is still in the prototype research stage and has not yet been applied to solid rocket engines. Summary of the Invention

[0007] The purpose of this invention is to provide a nozzle structure with a variable expansion ratio, which can at least solve some of the defects existing in the prior art.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A nozzle structure with a variable expansion ratio includes a nozzle section and a multi-stage expansion section connected sequentially along the gas injection direction at the outlet of the nozzle section; the nozzle section and the expansion sections, as well as adjacent expansion sections, are connected by a separable connection mechanism.

[0010] The separable connection mechanism includes a fastener and a combustion agent. The two ends of the fastener are respectively connected to two corresponding structural components. The combustion agent is located on the gas injection path at the outlet of the nozzle section. The combustion agent is used to burn and melt the fastener and generate high-temperature gas to separate the two structural components connected by the fastener.

[0011] Furthermore, the combustion agent includes a delay agent assembly and a separation actuation agent assembly. One end of the delay agent assembly is located on the gas injection path at the outlet of the nozzle section, and the other end is in contact with the separation actuation agent assembly. The fastener passes through the separation actuation agent assembly.

[0012] Furthermore, the delay agent assembly includes a delay agent column and a coating layer covering the outer surface of the delay agent column.

[0013] Furthermore, the separation actuation agent assembly includes a medicine box, a gas-generating drug tablet, and a fusible drug tablet. Both the gas-generating drug tablet and the fusible drug tablet are disposed in the medicine box. One end of the fusible drug tablet is in contact with the delay agent assembly, and the other end of the fusible drug tablet is in contact with the gas-generating drug tablet. The fusible drug tablet is provided with a through hole for the fastener to pass through.

[0014] Furthermore, the combustion temperature of the fusible tablet is greater than the melting point of the material used in the fastener, and the gas produced by the combustion of the fusible tablet generates a gas pressure less than the separation force between the two structural components connected to the fastener; the combustion rate of the gas-generating tablet is not less than the rate at which the gas-generating tablet is completely burned within a preset separation action time, and the gas produced by the combustion of the gas-generating tablet generates a gas pressure greater than the separation force between the two structural components connected to the fastener.

[0015] Furthermore, the gas inlet end face of the expansion section is provided with an annular groove of depth H1, and the nozzle section or the gas outlet end face of the adjacent expansion section connected to the gas inlet end face of this stage of the expansion section is provided with a boss of height H, and H1 is greater than H. The boss is assembled in the annular groove to form an installation cavity for accommodating the separation actuation agent assembly, and the two ends of the fastener are respectively connected to the corresponding annular groove and the boss.

[0016] Furthermore, a dynamic sealing putty layer is provided between the contact surfaces of the separation actuation agent assembly and the nozzle section and the expansion section, as well as between the gas inlet end face of the expansion section and the gas outlet end face of the nozzle section or the adjacent first-stage expansion section.

[0017] Furthermore, the inner surface of the expansion section is provided with a plurality of ignition holes for accommodating the delay agent assembly. The ignition holes extend radially along the expansion section and are at least partially connected to the annular groove.

[0018] Furthermore, an adhesive layer is provided between the mating contact surface of the delay agent component and the ignition hole.

[0019] In addition, the present invention also provides a solid rocket motor, including a combustion chamber and the above-mentioned variable expansion ratio nozzle structure, wherein the gas outlet of the combustion chamber is connected to the inlet of the nozzle section.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] (1) The variable expansion ratio nozzle structure provided by the present invention is designed with multiple expansion sections, and each expansion section is separated according to a preset time by designing a separable connection mechanism to change the nozzle outlet size, thereby changing the nozzle expansion ratio, ensuring that each stage of the multi-stage high thrust ratio engine works under the optimal expansion ratio condition, and maximizing energy utilization.

[0022] (2) The variable expansion ratio nozzle structure provided by the present invention does not require a complex auxiliary system, and the action mechanism is located inside the nozzle, without encroaching on the external space of the nozzle. It has no special requirements on the engine structure size and the type of propellant, so it can be applied to large, medium and small solid rocket engines and has a wide range of applications.

[0023] (3) In the variable expansion ratio nozzle structure provided by the present invention, the separation and starting energy of the expansion section is provided by the engine itself, so no additional excitation device is required, and the dependence on and influence on systems other than the engine is small.

[0024] (4) In the variable expansion ratio nozzle structure provided by the present invention, the separation of the expansion section is completed instantaneously, and the outlet size of each expansion section is designed in advance according to the requirements, which can effectively ensure the stable output thrust of the engine.

[0025] (5) In the variable expansion ratio nozzle structure provided by the present invention, the separation action of the expansion section mainly relies on the delayed propellant, the fusible propellant and the gas-generating propellant. The required amount of each agent is small. The negative mass required to achieve separation is negligible compared with the mass of the nozzle itself. Therefore, the present invention will not add extra negative mass to the solid rocket motor. Moreover, by designing the burning rate and size of the delayed propellant, the fusible propellant and the gas-generating propellant, the timing of the separation of the expansion section can be controlled to adapt to different separation requirements.

[0026] (6) In the variable expansion ratio nozzle structure provided by the present invention, the expansion section is jettisoned after the function is completed, which can reduce the negative mass of the missile to a certain extent; the more engine stages, the greater the thrust ratio, and the larger the engine size, the more significant the effect.

[0027] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the nozzle structure with variable expansion ratio for a two-stage thrust engine in this invention.

[0029] Figure 2 yes Figure 1 Enlarged view of the middle section (I);

[0030] Figure 3 This is a front view of the detachable actuating agent assembly in this invention;

[0031] Figure 4 This is a cross-sectional view of the separation actuation agent component in this invention;

[0032] Figure 5 yes Figure 4 Enlarged view of section A in the middle;

[0033] Figure 6 This is a cross-sectional view of the time-delaying agent component in this invention;

[0034] Figure 7 This is a schematic diagram of the nozzle section outlet end face in this invention;

[0035] Figure 8 This is a cross-sectional view of the nozzle section in this invention;

[0036] Figure 9 yes Figure 8 Enlarged view of section B;

[0037] Figure 10 This is a cross-sectional view of the expansion section in this invention;

[0038] Figure 11 This is a schematic diagram of the gas inlet end face of the expansion section in this invention;

[0039] Figure 12 This is a schematic diagram of the seal between the separable connecting mechanism, the nozzle section, and the expansion section in this invention;

[0040] Figure 13 This is a thrust-time curve diagram of an engine using the nozzle structure of the present invention and a conventional nozzle structure in an embodiment of the present invention.

[0041] Explanation of reference numerals in the attached drawings: 1. Nozzle section; 2. Expansion section; 3. Propellant cartridge; 4. Gas-generating tablet; 5. Fusible tablet; 6. Fastener; 7. Coating layer; 8. Delayed propellant column; 9. Through hole; 10. Boss; 11. Blind hole; 12. Annular groove; 13. Ignition hole; 14. Dynamic sealing putty layer; 15. Epoxy structural adhesive; 16. Adhesive layer. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0044] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation", "connection", and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, an abutting connection, or an integral connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0045] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0046] like Figure 1 and Figure 2 As shown, this embodiment provides a nozzle structure with a variable expansion ratio, including a nozzle section 1 and multiple expansion sections 2 connected sequentially along the gas injection direction at the outlet of the nozzle section 1; the nozzle section 1 and the expansion sections 2, as well as adjacent expansion sections 2, are connected by a separable connection mechanism; the separable connection mechanism includes a fastener 6 and a combustion agent, the two ends of the fastener 6 are respectively connected to two corresponding structural components, that is, the two ends of the fastener 6 are respectively connected to the nozzle section 1 and the expansion section 2, or adjacent expansion sections 2; the combustion agent is located on the gas injection path at the outlet of the nozzle section 1, the fastener 6 is at least partially placed in the combustion agent, the combustion agent is used to burn and melt the fastener 6, and generate high-temperature gas to push the nozzle section 1 and the expansion section 2, or adjacent expansion sections 2, to separate. In this embodiment, the throat area of ​​nozzle section 1 is fixed, and the exit area of ​​each stage expansion section 2 is determined according to the different optimal expansion ratios corresponding to each stage of the multi-stage high thrust ratio engine. During operation, after the first stage of the multi-stage high thrust ratio engine is completed, the separable connection mechanism melts the connecting piece 6 of the two expansion sections 2 corresponding to this stage and the next stage through the combustion of the propellant, so that the expansion section 2 corresponding to this stage is thrown away, while the expansion section 2 corresponding to the next stage of the engine is left as the nozzle exit end. Thus, when the next stage of the engine is working, it can still work at its corresponding optimal expansion ratio, thereby maximizing energy utilization.

[0047] As a specific implementation method, such as Figure 2As shown, the combustion agent includes a time-delay agent assembly and a separation actuation agent assembly. The time-delay agent assembly can control the separation time of the corresponding expansion section 2 according to the engine's corresponding stage operating time. The separation actuation agent assembly is used to fuse the fixing member 6 and generate the power to push the expansion section 2 apart. One end of the time-delay agent assembly is located on the gas injection path at the nozzle section 1 outlet, and the other end is in contact with the separation actuation agent assembly. The fixing member 6 passes through the separation actuation agent assembly. The gas injected from the nozzle section 1 outlet first ignites the time-delay agent assembly. After the time-delay agent assembly burns out, it ignites the separation actuation agent assembly. During the combustion of the time-delay agent assembly, the fixing member 6 is not fused. The fixing member 6 is fused only when the separation actuation agent assembly burns, thereby causing the corresponding expansion section 2 to separate. Therefore, by controlling the combustion rate and size of the time-delay agent assembly and the separation actuation agent assembly, the separation time of the expansion section 2 can be controlled to adapt to different separation requirements and achieve the purpose of changing the expansion ratio.

[0048] In some embodiments, such as Figure 6 As shown, the delay propellant assembly includes a delay propellant grain 8 and a coating layer 7 covering the outer surface of the delay propellant grain 8. The delay propellant grain 8 uses a low-sensitivity propellant with a corresponding burn rate based on the engine's first-stage operating time. The coating layer 7 is made of a rubber material that is easily burned and has good compatibility with the delay propellant grain 8, and covers all outer surfaces of the delay propellant grain 8 except for the area in contact with the separation actuation propellant assembly.

[0049] In some embodiments, such as Figure 3 , Figure 4 and Figure 5As shown, the separation actuation agent assembly includes a medicine box 3, a gas-generating drug tablet 4, and a fusible drug tablet 5. The gas-generating drug tablet 4 and the fusible drug tablet 5 are both disposed in the medicine box 3. One end of the fusible drug tablet 5 is in contact with the delay agent assembly, and the other end of the fusible drug tablet 5 is in contact with the gas-generating drug tablet 4. The fusible drug tablet 5 is provided with a through hole 9 for the fastener 6 to pass through. The fusible detonator 5 is made of a high-heat-generating, low-gas-production propellant. Its function is to generate high temperature during combustion to fuse the fastener 6 or reduce the mechanical properties of the fastener, so as to facilitate subsequent separation. Specifically, the combustion temperature of the fusible detonator 5 must be much higher than the melting point of the material used in the fastener 6, generally recommended to be above 2000K. At the same time, the gas production from the combustion of the fusible detonator 5 should not be greater than the leakage from the ignition hole 13, so as to ensure that the pressure in the mounting cavity of the separation actuation agent assembly does not increase, or the pressure increase in the mounting cavity is insufficient for the expansion section 2 to overcome the friction with the nozzle section 1 or the adjacent expansion section 2. The gas-generating propellant 4 is made of a high-burning-rate, high-gas-production propellant or gunpowder. Its function is to generate a large amount of gas through combustion, creating instantaneous high pressure that forces the corresponding expansion section 2 to be ejected. Specifically, the burning rate of the gas-generating propellant 4 must ensure that it burns completely within the specified separation actuation time. Simultaneously, the gas production from the combustion of the propellant 4 must be much greater than the leakage from the ignition port 13, thereby generating sufficient pressure within the installation cavity of the separation actuation agent assembly to push the expansion section 2 to overcome the friction with the nozzle section 1 or adjacent expansion sections 2, thus achieving smooth separation. The cartridge 3 is made of an easily ablated material, such as celluloid. After the delayed-action agent component has finished burning, the fusible detonator 5 is ignited first. The fusible detonator 5 releases a large amount of heat as it burns. When the fusible detonator 5 burns to or beyond the area of ​​the fixed member 6, the high-temperature gas generated continues to heat the fixed member 6, so as to melt the fixed member 6 or reduce the mechanical properties of the fixed member 6. At this time, the nozzle section 1 and the expansion section 2, or the two-stage expansion section 2, which were originally connected by the fixed member 6, are still in a connected state. After the fusible detonator 5 finishes burning, the gas-generating detonator 4 is ignited. The gas-generating detonator 4 burns and generates a large amount of high-temperature gas, forming an instantaneous high pressure that forces the nozzle section 1 and the expansion section 2, or the two-stage expansion section 2, to separate.

[0050] Optionally, the fastener 6 may be a fastening rod made of a low-melting-point metal (such as aluminum alloy), and the fastening rod must be located within the area of ​​the melt-off tablet 5.

[0051] Regarding the specific connection method between the delayed-action agent assembly and the separation-actuated agent assembly in the nozzle section 1 and the expansion section 2, or between the two-stage expansion sections 2, in some embodiments, such as... Figures 7 to 11As shown, an annular groove 12 with a depth of H1 can be designed on the gas inlet end face of the expansion section 2. At the same time, a boss 10 with a height of H is provided on the gas outlet end face of the nozzle section 1 or the gas outlet end face of the adjacent first-level expansion section 2 that is connected to the gas inlet end face of this stage expansion section 2, and H1 is greater than H. In this way, when the gas outlet end face of the nozzle section 1 or the gas outlet end face of the adjacent first-level expansion section 2 is connected to the gas inlet end face of the subsequent stage expansion section 2, the boss 10 can be assembled in the annular groove 12 to form an installation cavity, and the separation actuation agent assembly is accommodated in this installation cavity. Meanwhile, in order to fix the fixing member 6, blind holes 11 are provided at corresponding positions in the annular groove 12 and on the end face of the boss 10. After the fixing member 6 passes through the through hole 9 in the area of ​​the fused tablet 5, the two ends of the fixing member 6 pass through the blind holes 11 on the annular groove 12 and the end face of the boss 10, respectively, to ensure a reliable connection between the nozzle section 1 and the expansion section 2, or between the two expansion sections 2. Among them, multiple blind holes 11 can be provided and are arranged at equal intervals along the circumference of the annular groove 12 / the end face of the boss 10. The blind holes 11 on the annular groove 12 and the end face of the boss 10 correspond one-to-one. Correspondingly, multiple fasteners 6 are also provided to further ensure the reliability of the connection between the nozzle section 1 and the expansion section 2, or between the two expansion sections 2.

[0052] For the installation of delayed-action drug components, such as Figure 10 As shown, a plurality of ignition holes 13 are formed on the inner surface of the expansion section 2. The ignition holes 13 are arranged at equal intervals along the circumference of the inner surface of the expansion section 2. Each ignition hole 13 extends radially along the expansion section 2, and at least part of the ignition hole 13 is connected to the annular groove 12. The delay agent component is filled in the ignition hole 13. The distance between the ignition hole 13 and the gas inlet end face of the expansion section 2 is L. After the delayed-action agent component has burned in the ignition hole 13, since the ignition hole 13 is connected to the annular groove 12, the separation actuation agent component in the annular groove 12 can be ignited. When the amount of gas generated by the combustion of the fused piece 5 of the separation actuation agent component is small, it can be discharged through the ignition hole 13 to ensure that the pressure in the installation cavity is in a low state. At this time, the nozzle section 1 and the expansion section 2, or the two-stage expansion sections 2, are still reliably connected. After the fused piece 5 has burned, the gas-generating piece 4 is ignited. Since the gas-generating piece 4 generates a large amount of high-temperature gas in a short time, its gas production is much greater than the discharge of the ignition hole 13. This causes the pressure in the installation cavity to rise rapidly, causing the nozzle section 1 and the expansion section 2, or the two-stage expansion sections 2, to separate.

[0053] To ensure a reliable connection between nozzle section 1 and expansion section 2, or between two stages of expansion section 2, in some embodiments, such as Figure 12As shown, a dynamic sealing putty layer 14 is provided between the mating contact surfaces of the separation actuation agent assembly and the nozzle section 1 and the expansion section 2, and between the gas inlet end face of the expansion section 2 and the gas outlet end face of the nozzle section 1 or the adjacent expansion section 2. This ensures reliable sealing and adhesion of the assembly gap without providing excessive adhesive force that could affect the normal separation between the nozzle section 1 and the expansion section 2, or between two stages of expansion sections 2. Epoxy structural adhesive 15 is applied to the mating surfaces of the fastener 6 and the nozzle section 1 and expansion section 2 connected to it, while no adhesive is applied between the fastener 6 and the separation actuation agent assembly, ensuring a reliable connection between the two sections connected by the fastener 6. An adhesive layer 16 is provided between the mating contact surface of the delayed-action agent component and the ignition hole 13. This adhesive layer 16 uses a special adhesive selected according to the characteristics of the coating layer 7 of the delayed-action agent component to ensure that the delayed-action agent component can be reliably fixed. At the same time, no sealant is applied between the delayed-action agent component and the separation actuation agent component to prevent the delayed-action agent component from failing to ignite the agent in the separation actuation agent component. In this embodiment, the nozzle structure adopts conventional static sealing, so the structural sealing difficulty is small and it is easier to achieve efficient and reliable sealing.

[0054] The following uses the conical nozzle structure of a two-stage thrust engine as an example to illustrate the working process of the variable expansion ratio nozzle structure of the present invention. In this case, the nozzle structure includes nozzle section 1 and expansion section 2. The exit area of ​​expansion section 2 can meet the optimal expansion ratio when the engine is operating in the first stage, and the exit area of ​​nozzle section 1 can meet the optimal expansion ratio when the engine is operating in the second stage. The specific working process is as follows:

[0055] S1. When the engine is operating in the first stage, the high-temperature gas flows through the expansion section 2, burning the coating layer 7 on the oblique section of the delay propellant 8 and igniting the delay propellant 8; the working time of the delay propellant 8 is t1. At this time, the expansion section 2 is still firmly connected to the nozzle section 1, and the nozzle expansion ratio ε1 is the optimal expansion ratio when the engine is operating in the first stage.

[0056] S2. After the delayed-action propellant 8 has finished burning, the fusible pellet 5 in the separation actuation agent assembly is ignited. When the fusible pellet 5 is working, it releases a large amount of heat. At the same time, the generated gas is discharged through the ignition hole 13 on the expansion section 1, ensuring that the pressure in the installation cavity of the separation actuation agent assembly is in a low state. At this time, the expansion section 2 and the nozzle section 1 are still reliably connected.

[0057] S3. When the fused tablet 5 burns to or beyond the area of ​​the fixed member 6, the generated high-temperature gas continuously heats the fixed member 6. Before the fused tablet 5 finishes working, the fixed member 6 is melted or its strength is reduced to a certain threshold. However, at this time, the expansion section 2 and the nozzle section 1 are still reliably connected under the action of some adhesive. At this time, the nozzle expansion ratio is still ε1.

[0058] S4. After the fusible tablet 5 finishes working, the gas-generating tablet 4 is ignited. The gas-generating tablet 4 generates a large amount of high-temperature gas in a short time. The high-temperature gas further heats the fastener 6. At the same time, the gas generation of the gas-generating tablet 4 is much greater than the amount discharged from the ignition hole 13 on the expansion section 2, causing the pressure in the installation cavity of the separation actuation agent assembly to rise rapidly.

[0059] S5. Under the high pressure in the installation cavity of the separation actuating agent assembly, the adhesive force provided by the dynamic sealing putty layer 14 is insufficient to resist the separation force generated by the high pressure. The expansion section 2 separates from the nozzle section 1. At this time, the first stage of the engine is completed and the second stage of the engine begins to work. The optimal expansion ratio required for the second stage of the engine to work is exactly the nozzle expansion ratio ε2.

[0060] S6. The nozzle maintains an expansion ratio of ε2 until the engine's second stage operation ends.

[0061] Since conventional nozzles have a fixed expansion ratio, considering overall energy utilization, the expansion ratio ε2 is designed according to the engine's two-stage full expansion in most cases. In this case, the engine's first stage operates in a state of underexpansion, which reduces the engine's energy utilization efficiency. The higher the engine thrust ratio, the more severe the energy loss and the lower the efficiency.

[0062] Taking a single-chamber dual-thrust engine as an example, the efficiency difference between the present invention and conventional nozzle structures is illustrated below. The thrust-time curves of engines using the two nozzle types are shown in the figure. Figure 13 As shown in Table 1, the engine performance parameters are as follows.

[0063] Table 1: Comparison of Engine Total Stroke

[0064]

[0065] As shown in the table above, the total stroke of the first stage using the nozzle structure of the present invention can be increased by 15.6%, and the total stroke of the engine as a whole can be increased by 5.3%. Compared with the conventional nozzle structure, the nozzle structure of the present invention can maximize the energy utilization of the two-stage propellant, significantly improve the total stroke of the engine, and enhance engine performance.

[0066] Of course, this invention is not limited to two-stage thrust engines; it can also be applied to three-stage or even multi-stage engines. At the same time, the nozzle type is not limited to a conical nozzle.

[0067] In addition, this embodiment also provides a solid rocket engine, including a combustion chamber and the above-mentioned variable expansion ratio nozzle structure, wherein the gas outlet of the combustion chamber is connected to the inlet of the nozzle section.

[0068] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A nozzle structure with a variable expansion ratio, characterized in that: It includes a nozzle section and a multi-stage expansion section connected sequentially along the gas injection direction at the outlet of the nozzle section; the nozzle section and the expansion section are connected by a detachable connection mechanism, as are two adjacent stages of the expansion section. The separable connection mechanism includes a fastener and a propellant. The fastener is connected to two corresponding structural components at both ends. The propellant is located on the gas injection path at the nozzle section outlet. The propellant is used to burn and melt the fastener and generate high-temperature gas to separate the two structural components connected by the fastener. The propellant includes a delay propellant assembly and a separation actuation propellant assembly. One end of the delay propellant assembly is located on the gas injection path at the nozzle section outlet, and the other end is in contact with the separation actuation propellant assembly. The fastener passes through the separation actuation propellant assembly.

2. The nozzle structure with variable expansion ratio as described in claim 1, characterized in that: The delay agent assembly includes a delay agent column and a coating layer covering the outer surface of the delay agent column.

3. The nozzle structure with variable expansion ratio as described in claim 1, characterized in that: The separation actuation agent assembly includes a cartridge, a gas-generating tablet, and a fusible tablet. Both the gas-generating tablet and the fusible tablet are disposed in the cartridge. One end of the fusible tablet is in contact with the delay agent assembly, and the other end of the fusible tablet is in contact with the gas-generating tablet. The fusible tablet has a through hole for the fastener to pass through.

4. The nozzle structure with variable expansion ratio as described in claim 3, characterized in that: The combustion temperature of the fusible tablet is greater than the melting point of the material used in the fastener, and the gas produced by the combustion of the fusible tablet generates a gas pressure less than the separation force between the two structural components connected to the fastener; the combustion rate of the gas-generating tablet is not less than the rate at which the gas-generating tablet is completely burned within a preset separation action time, and the gas produced by the combustion of the gas-generating tablet generates a gas pressure greater than the separation force between the two structural components connected to the fastener.

5. The nozzle structure with variable expansion ratio as described in claim 1, characterized in that: The gas inlet end face of the expansion section is provided with an annular groove of depth H1. The nozzle section or the gas outlet end face of the adjacent expansion section connected to the gas inlet end face of this stage of the expansion section is provided with a boss of height H, and H1 is greater than H. The boss is assembled in the annular groove to form an installation cavity for accommodating the separation actuation agent assembly. The two ends of the fastener are respectively connected to the corresponding annular groove and the boss.

6. The nozzle structure with variable expansion ratio as described in claim 5, characterized in that: A dynamic sealing putty layer is provided between the contact surfaces of the separation actuation agent assembly and the nozzle section and the expansion section, as well as between the gas inlet end face of the expansion section and the gas outlet end face of the nozzle section or the adjacent first-stage expansion section.

7. The nozzle structure with variable expansion ratio as described in claim 5, characterized in that: The expansion section has multiple ignition holes on its inner surface for accommodating the delay agent assembly. The ignition holes extend radially along the expansion section and are at least partially connected to the annular groove.

8. The nozzle structure with variable expansion ratio as described in claim 7, characterized in that: An adhesive layer is provided between the mating contact surfaces of the delay agent component and the ignition hole.

9. A solid rocket motor, characterized in that: The system includes a combustion chamber and a nozzle structure with a variable expansion ratio as described in any one of claims 1 to 8, wherein the gas outlet of the combustion chamber is connected to the inlet of the nozzle section.

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