Solid engine for environment-friendly remote fire-fighting rocket projectile and preparation method of solid engine

Abstract

The invention relates to the technical field of fire extinguishing equipment in urban public facilities, in particular to a solid engine for an environment-friendly remote fire-fighting rocket projectile and a preparation method of the solid engine. The engine is composed of an engine front end socket, a front end socket sealing ring, an engine shell, an engine grain, an engine igniter assembly and the like; an engine shell is formed by 7075 aluminum alloy in a hot extrusion mode, a grain is a double-cobalt double-base grain and adopts a free filling mode, a spray pipe is made of phenolic aldehyde cloth rod materials, a 45 # steel throat lining is embedded in the spray pipe, and an igniter is of a cage type structure. The preparation method comprises the steps of shell processing, grain forming, spray pipe manufacturing, igniter manufacturing and assembly assembling and testing. According to the solid engine for the environment-friendly remote fire-fighting rocket projectile, the problems of poor environmental protection property, short firing range and the like in the prior art are solved, the waste shell can be recycled, 5 kilograms of fire extinguishing working media can be pushed out of 5 kilometers, the mass ratio is close to 0.7, the maintainability is good, the solid engine is suitable for batch production, the cost is low, and the blank of domestic related products is filled.

Description

Technical Field

[0001] This invention relates to the field of fire extinguishing equipment technology in urban public facilities, specifically to an environmentally friendly long-range fire-fighting rocket solid engine and its preparation method. Background Technology

[0002] Firefighting rockets are a new type of firefighting tool that can be launched from ground vehicles or drones to rapidly deliver extinguishing agents to fire sites that are difficult for firefighters to access, such as warehouses, chemical and oil storage areas, shopping malls, residential buildings, factories, and forests, in order to reduce the damage caused by fires. They use a solid-fuel engine to provide thrust, delivering the extinguishing agent in the rocket to the predetermined target location. The extinguishing agent is then released by a fuse, isolating oxygen from the fire source to extinguish the fire. Research and development of long-range firefighting rockets has been carried out abroad. South Korea has developed a vehicle-mounted forest firefighting rocket, and Russia has developed the GAZ-5903 forest firefighting rocket launcher with 22 launch tubes. Many domestic units have also developed vehicle-mounted and drone-borne firefighting rockets, but the rocket range is relatively short, making it difficult to meet the needs of long-distance firefighting. Therefore, there is an urgent need to develop long-range and environmentally friendly firefighting rocket engines.

[0003] Solid-fuel engines are a key component of fire-fighting rockets, and their performance directly impacts rocket range, operational efficiency, effective dispersal of extinguishing agents, and environmental impact. Currently, only a few units in the aerospace and defense industries in China are developing such engines, resulting in numerous shortcomings. Fire-fighting rocket engines have a low mass-to-weight ratio, mostly using high-strength steel casings, generally less than 0.6. Furthermore, their performance is low, with small propellant charges and low energy, limiting their range to mostly a few hundred meters, which cannot meet the fire-fighting requirements of large-scale fire scenes. The engine casing materials are mostly high-strength steel and fiberglass / epoxy resin. Steel casings, due to their high density, result in a large mass, reducing the rocket's performance. Fiberglass / epoxy resin materials do not degrade in the natural environment, posing significant environmental problems. Moreover, the fiberglass / epoxy resin casings used by Zhongtian Rocket Company are wrapped with propellant grains as the core mold. The winding process involves the thermal expansion and deformation of the propellant grain during molding, which can cause the shell to bend. To meet the requirements for launch within the orbit, the outer cylindrical surface of the shell needs to be machined, which can easily lead to uneven shell wall thickness, resulting in a decrease in the shell's pressure-bearing capacity and engine reliability. At the same time, this type of engine, which is formed by winding fibers on the outer surface of the propellant grain, has poor maintainability of the shell and propellant grain. Problems with the propellant grain or shell often lead to the scrapping of the entire engine, increasing manufacturing costs. Engine insulation and other processes are complex and costly. Some engine igniters use materials such as aluminum alloys, which are complex in structure and heavy in weight. In addition, there are very few specifications of fire-fighting rocket engines in China, with only a few types and short ranges, which limits the overall selection of fire-fighting rocket units. Therefore, in view of the above situation, there is an urgent need to develop an environmentally friendly long-range fire-fighting rocket solid engine and its preparation method to overcome the shortcomings in current practical applications. Summary of the Invention

[0004] The purpose of this invention is to provide an environmentally friendly solid rocket motor for long-range firefighting rockets and its preparation method, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] An environmentally friendly long-range fire-fighting rocket solid engine includes an engine front end cap, a front end cap sealing ring, an engine housing, an engine propellant grain, an engine igniter assembly, an engine rear end cap, a rear end cap sealing ring, an engine nozzle, a nozzle steel throat liner, and a nozzle plug.

[0007] The engine front end cap is threadedly connected to the engine housing, and a front end cap sealing ring is fitted at the connection point.

[0008] The engine propellant is filled into the engine housing and positioned by engaging with the engine rear end cap through the external thread on the outer circumference of the engine propellant.

[0009] One end of the engine rear end cap is threaded to the engine housing, and a rear end cap sealing ring is fitted at the connection. The other end is threaded to the engine nozzle.

[0010] The nozzle steel throat liner is embedded in the throat of the engine nozzle, and the nozzle plug is sealed and assembled at the outlet end of the engine nozzle.

[0011] The engine igniter assembly is threaded to the front end cap of the engine, with the ignition end facing the engine propellant column.

[0012] As a further aspect of the present invention: both the front end cap and the rear end cap of the engine are made of 7075 aluminum alloy;

[0013] The engine housing is made of 7075 aluminum alloy, the engine propellant is a double cobalt double base propellant, and the engine igniter assembly is a cage structure.

[0014] As a further aspect of the present invention: the engine housing is manufactured by hot extrusion molding after being treated by the T6 heat treatment process, and the inner surface of the engine housing is coated with heat-insulating coating.

[0015] As a further aspect of the present invention: the inner core of the engine propellant grain is an 8-star-shaped inner surface, the outer surface is covered with a nylon base tape insulation layer with a thickness of 0.3mm, and the insulation layer is coated with a flame-restricting layer with a thickness of 0.2mm.

[0016] As a further aspect of the present invention: the engine nozzle is a Laval nozzle, made of phenolic fabric rods, with a convergence angle of 90° and an expansion angle of 30°.

[0017] As a further aspect of the present invention: the nozzle steel throat liner is made of No. 45 carbon steel and is embedded in the throat of the engine nozzle by epoxy resin bonding.

[0018] As a further embodiment of the present invention: the engine igniter assembly includes an igniter connector, a wiring screw, an ignition head, a coating layer, a cage-type propellant box, ignition propellant, and a plug;

[0019] The igniter connector, cage-type powder box, and plug are made of ABS plastic, with an aluminum foil covering layer, and the ignition powder is a mixture of HY-2 and HY-5 black powder;

[0020] The ignition head is fixed inside the cage-type powder box and in contact with the ignition powder. The cage-type powder box is wrapped with a coating layer and is assembled into the internal cavity of the igniter connector.

[0021] The wiring screw is threaded to the igniter connector, and one end is connected to the electrode of the igniter.

[0022] The plug is fixed to the end of the igniter connector away from the engine propellant column;

[0023] The engine igniter assembly adopts a constant current ignition method with an ignition current of not less than 2A and a duration of 20ms, and uses a redundant ignition scheme with two ignition elements.

[0024] As a further aspect of the present invention, both the front end cap sealing ring and the rear end cap sealing ring are made of silicone rubber.

[0025] A method for preparing an environmentally friendly long-range fire-fighting rocket solid-propellant engine, comprising the following steps:

[0026] Step 1: Engine housing processing: After solution treatment of 7075 aluminum alloy under T6 heat treatment regime, it is cut into blanks, hot extruded into the prototype of engine housing, after aging treatment, it is precision machined, and finally the inner surface is sprayed with heat insulation coating.

[0027] Step 2: Engine propellant grain forming: The raw material of the double cobalt double base propellant grain is extruded and formed by a screw press, and after being cut, it is covered with a nylon base tape heat insulation layer and coated with a flame-restricting layer.

[0028] Step 3: Nozzle manufacturing: The Laval nozzle shell is manufactured by phenolic cloth rod machining, and the 45# carbon steel is processed into a nozzle steel throat liner, which is then bonded to the nozzle throat with epoxy resin and the nozzle plug is assembled.

[0029] Step 4: Igniter fabrication: Machining the various parts of the igniter, assembling the ignition head and ignition powder into the cage-type powder box, wrapping it with a protective layer, and then assembling it together with the wiring screws and plugs into the igniter connector.

[0030] Step 5: Component assembly: Fill the engine propellant into the engine housing, connect the engine front end cap, engine igniter assembly, engine rear end cap and engine nozzle in sequence, and assemble the corresponding sealing rings.

[0031] Step 6: Testing and Inspection: Conduct a casing hydrostatic test and a ground ignition test on the assembled engine.

[0032] As a further aspect of the present invention: in step 1, the aging treatment temperature is 200°C and the treatment time is 3 hours; the heat insulation coating is GT-401 heat insulation coating with a coating thickness of 0.1 mm.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] This invention has achieved its design technical specifications through shell hydrostatic burst test, engine ground ignition test and rocket flight test, and fully meets the design requirements of market customers. It has become the highest total stroke and best performance solid rocket engine for fire-fighting rockets in China, which can push 5 kg of fire-fighting propellant to a fire operation area 5 km away.

[0035] Compared to the non-degradable and environmentally unfriendly issues of fiberglass / epoxy resin engine casings, 7075 aluminum alloy casings can be recycled and reused after rocket operation, causing no pollution to the environment. If widely promoted and used nationwide, hundreds of thousands of waste fiberglass / epoxy resin casings can be reduced every year, significantly reducing environmental pollution. At the same time, a large amount of aluminum alloy raw materials can be recycled, and the manufacturing process of engine aluminum alloy casings is more environmentally friendly than that of non-metallic casings such as fiberglass.

[0036] The engine of this invention uses a dual cobalt propellant grain and a large propellant loading coefficient. Due to the high geometric accuracy of the aluminum alloy shell, such as cylindricity, a large diameter propellant grain can be loaded under the condition of the same engine outer diameter. The engine mass ratio is close to 0.7, and the total stroke and other performance are greatly improved, reaching 5862 N·s. This can increase the rocket's flight path and greatly improve the range and efficiency of fire fighting operations.

[0037] The engine propellant loading adopts a free loading method, and the pressure bearing capacity of the shell can be tested and measured, which improves the reliability of the engine. Furthermore, the shell and propellant are well maintainable and replaceable, avoiding the problem of deformation of the composite material shell causing the propellant and shell to be scrapped together, thus reducing quality costs and improving economic efficiency.

[0038] The engine has low production site costs and low safety risks. Compared with non-metallic casings, the current domestic non-metallic casing manufacturing requires winding fibers onto the propellant grains and must be carried out in explosion-proof workshops. In contrast, the 7075 aluminum alloy casing can be processed and manufactured in non-explosion-proof workshops and facilities, reducing the investment in production facilities.

[0039] Because the aluminum alloy shell is manufactured using a hot extrusion process, tubing can be continuously produced and cut to size. The propellant grains can also be continuously formed and then cut to size using a screw press. Therefore, this engine is particularly suitable for batch production. Its batch production cost is about 10% lower than that of composite material shells, which can significantly reduce production costs and is suitable for civilian use.

[0040] The engine of this invention expands the specifications of fire-fighting rocket engines, providing more options for fire-fighting rockets for different purposes; the igniter structural components are made of non-metallic materials, which are lighter than the aluminum alloy structural components widely used in China, further improving engine performance. Attached Figure Description

[0041] Figure 1 This is an assembly structure diagram of the solid rocket motor for environmentally friendly long-range firefighting rockets in an embodiment of the present invention.

[0042] Figure 2 This is a structural diagram of the engine housing in an embodiment of the present invention.

[0043] Figure 3 This is a front view schematic diagram of the engine propellant grain in an embodiment of the present invention.

[0044] Figure 4 This is a side view of the propellant grain of the engine in an embodiment of the present invention.

[0045] Figure 5 This is a structural diagram of the engine nozzle in an embodiment of the present invention.

[0046] Figure 6 This is a structural diagram of the engine igniter in an embodiment of the present invention.

[0047] Figure 7 This is a predicted curve of the internal ballistic pressure of the engine at -30℃ in an embodiment of the present invention.

[0048] Figure 8 This is a predicted ballistic thrust curve for the engine at -30℃ in an embodiment of the present invention.

[0049] Figure 9 This is a predicted curve of the internal ballistic pressure of the engine at +20°C in an embodiment of the present invention.

[0050] Figure 10 This is a predicted trajectory thrust curve for the engine at +20°C in an embodiment of the present invention.

[0051] Figure 11 This is a predicted curve of the internal ballistic pressure of the engine at +50°C in an embodiment of the present invention.

[0052] Figure 12 This is a predicted trajectory thrust curve for the engine at +50°C in an embodiment of the present invention.

[0053] Figure 13 This is a cloud diagram showing the stress distribution of the engine casing in an embodiment of the present invention.

[0054] Figure 14 This is a stress distribution cloud diagram of the engine front end cap in an embodiment of the present invention.

[0055] Figure 15 This is a cloud diagram showing the stress distribution of the engine nozzle in an embodiment of the present invention.

[0056] Figure 16 This is a schematic diagram of the pressure-thrust curve of the C1 engine during ground ignition test in an embodiment of the present invention.

[0057] Figure 17 This is a schematic diagram of the pressure-thrust curve of the C2 engine ground ignition test in an embodiment of the present invention.

[0058] In the diagram: 1-Engine front end cap, 2-Front end cap sealing ring, 3-Engine housing, 4-Engine propellant, 5-Engine igniter assembly, 6-Engine rear end cap, 7-Rear end cap sealing ring, 8-Engine nozzle, 9-Nozzle steel throat liner, 10-Nozzle plug, 11-Igniter connector, 12-Wiring screw, 13-Ignition head, 14-Covering layer, 15-Cage-type propellant box, 16-Ignition powder, 17-Plug. Detailed Implementation

[0059] 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.

[0060] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0061] Please see Figures 1-17 The present invention provides an environmentally friendly long-range fire-fighting rocket solid engine and its preparation method. The environmentally friendly long-range fire-fighting rocket solid engine is composed of an engine front end cap 1, a front end cap sealing ring 2, an engine housing 3, an engine propellant grain 4, an engine igniter assembly 5, an engine rear end cap 6, a rear end cap sealing ring 7, an engine nozzle 8, a nozzle steel throat liner 9, and a nozzle plug 10.

[0062] The engine igniter assembly 5 includes an igniter connector 11, a wiring screw 12, an ignition head 13, a covering layer 14, a cage-type powder box 15, an ignition powder 16, and a plug 17.

[0063] The front end cap 1 of the engine is connected to the engine housing 3 by threads, and the connection is sealed with the front end cap sealing ring 2. The engine propellant 4 is filled into the engine housing 3. The external thread M84×1.5 on the outer surface of the engine propellant 4 is engaged with the corresponding thread inside the engine rear end cap 6, which not only realizes the positioning connection between the propellant 4 and the rear end cap, but also ensures the coaxiality of the propellant 4 in the engine housing 3, and avoids thrust eccentricity during combustion.

[0064] The engine ignition assembly 5 is threadedly connected to the engine front end cap 1; the engine rear end cap 6 is threadedly connected to the engine nozzle 8, with the external thread on the engine nozzle 8 screwed into the internal thread on the engine rear end cap 6 to achieve the connection, and sealant is applied to the connection point. The function of the sealant is to prevent leakage of high-temperature and high-pressure gas and to ensure stable pressure when the engine is working; the engine rear end cap 6 is threadedly connected to the engine housing 3, with the internal thread on the housing 3 connecting to the external thread on the engine rear end cap 6, and a rear end cap sealing ring 7 is added in the middle to ensure sealing when the engine is working;

[0065] The nozzle steel throat liner 9 is bonded to the engine nozzle 8; the nozzle plug 10 is bonded to the inner conical surface of the engine nozzle 8. The function of the nozzle plug 10 is to seal the nozzle outlet during engine storage and transportation to prevent impurities from entering the nozzle and affecting its performance. After the engine is ignited, the nozzle plug 10 automatically falls off under the pressure of the gas, without affecting the normal ejection of gas.

[0066] The overall structure is compact and the components are reliably connected, providing a stable foundation for the performance of the engine and fully meeting the needs of remote fire fighting operations. The distance from the engine rear end face 6 to the nozzle outlet is 60mm.

[0067] In one embodiment of the present invention, the engine housing 3, the front end cap 1, and the rear end cap 6 are all made of 7075 aluminum alloy. After being treated by the T6 heat treatment process, the cylinder of the engine housing 3 is made by advanced hot extrusion molding process.

[0068] The engine housing 3 has an outer diameter of Φ100mm and a wall thickness of 2.5mm. Internal threads are machined into the inner holes at both ends of the housing 3 for connection with other components. The engine housing 3 is heat-insulated using a zirconium oxide spraying process, and the inner surface of the housing is coated with GT-401 heat-insulating coating with a coating thickness of 0.1mm.

[0069] The specific preparation steps are as follows:

[0070] ① After the 7075 aluminum alloy material is solution treated by the T6 heat treatment system, it is cut into blanks according to the preset size, and then expanded and formed by pressure processing using a press. With the help of internal core molds and other tooling, the dimensions and positional accuracy of the formed shell 3 are made to a high level. The thickness of the tube is 5mm, the inner diameter tolerance is ±0.05mm, and the straightness of the shell 3 is 0.3mm.

[0071] ② The formed workpiece is subjected to aging treatment at 200℃ for 3 hours to obtain high-strength mechanical properties. After treatment, the tensile strength of the material is >550MPa, the yield strength is ≥495MPa, and the elongation is ≥6%.

[0072] ③ The outer circle and both ends of the housing 3 are precision machined with threads and sealing surfaces for connection with the engine nozzle 8 and engine ignition assembly 5.

[0073] ④ Spray GT-401 heat insulation coating on the inner surface of the shell 3 to ensure that the coating thickness is 0.1mm.

[0074] In summary, 7075 aluminum alloy has a density of only 2.7 g / cm³, and after T6 heat treatment, its tensile strength reaches as high as 560 MPa. It also has good plasticity, replacing traditional glass fiber / epoxy resin materials. Its waste shell can be recycled and reused, effectively overcoming the problems of non-degradability and environmental unfriendliness of glass fiber / epoxy resin shells. At the same time, compared with traditional steel shells, 7075 aluminum alloy shells significantly reduce their own weight, significantly improving the engine's weight-to-weight ratio.

[0075] The engine casing 3, manufactured using a hot extrusion molding process, has higher geometric accuracy than composite material casings, uniform wall thickness, cylindricity up to 0.1 mm, and high internal hole precision requiring no additional machining. It can accommodate engine propellant grains 4 with larger diameters, improving the propellant loading coefficient and thus enhancing engine performance. Furthermore, this manufacturing process enables continuous production, requiring only dimensional cutting, facilitating batch production and reducing manufacturing costs. Batch production costs are approximately 10% lower than those of composite material casings.

[0076] The design pressure of shell 3 is 12MPa, and the design safety factor is 1.3. After hydrostatic testing, it fully meets the pressure requirements of the engine during operation, ensuring the reliability of the engine. In the shell strength calculation, the maximum stress of the combustion chamber shell is 338.28MPa and the residual strength coefficient is 1.48. The maximum stress of the front and rear end caps is 388.61MPa and the residual strength coefficient is 1.29, all of which meet the design requirements.

[0077] In one embodiment of the present invention, the engine propellant grain 4 uses a cobalt-based propellant grain, replacing the widely used lead-based propellant grain. The process employs a threaded extrusion forming process, and the theoretical specific gravity of the propellant grain is 1.61 ± 0.02 g / cm³. 3 Explosive heat ≥3525J / g.

[0078] The inner core of the engine propellant grain 4 is designed with an 8-star internal surface. The outer diameter of propellant grain 4 is Φ92mm, and its length is 311mm. The outer cylindrical surface of propellant grain 4 is machined with an M84×1.5 external thread. The outer surface is covered with a 0.3mm thick nylon base tape to form an insulation layer. Furthermore, a 0.2mm thick flame-retardant layer is coated on the outside of propellant grain 4 to ensure that the outer surface of propellant grain 4 does not participate in combustion during engine operation. The initial combustion surface area is 627.5482cm². 2 The maximum burning surface area is 874.333 cm². 2 .

[0079] The specific preparation steps are as follows:

[0080] ① The raw material of the double cobalt double base drug column is extruded and formed by a screw press, and then cut into preset dimensions;

[0081] ② Processing is carried out using specially designed forming and extrusion dies to ensure the product consistency of engine propellant grain 4;

[0082] ③ The outer surface of the formed engine propellant grain 4 is covered with nylon base tape to form an insulation layer;

[0083] ④ Coat the outer surface of the engine propellant grain 4 with a 0.2mm thick flame-limiting layer.

[0084] In summary, compared with traditional double-lead propellant, dual-cobalt dual-base propellant has the advantages of high total stroke performance and low cost; its 8-star internal surface design can effectively control the combustion area, with an initial combustion surface area of ​​627.5482 cm² and a maximum combustion surface area of ​​874.333 cm², which can generate sufficient thrust to meet the requirements of long-range engine flight.

[0085] The external thread design on the outer surface of the propellant grain 4 facilitates connection with the engine rear end cap 6 and serves as a centering element; the nylon base insulation layer and the flame-retardant coating on the outer surface effectively ensure the stability of the combustion of the propellant grain 4 during engine operation, prevent the outer surface from participating in combustion and affecting engine performance, and further improve the overall working efficiency of the engine.

[0086] In one embodiment of the present invention, the engine nozzle 8 is a Laval nozzle, the nozzle 8 housing is machined from phenolic cloth rod 3721GB / T7819-2001, the nozzle 8 throat diameter is Φ16mm, the convergence angle is 90°, and the expansion angle is 30°.

[0087] To address the issue of high ablation rate in the nozzle throat liner, a nozzle throat liner inlay steel sleeve design technology is adopted. The nozzle steel throat liner 9 is made of No. 45 carbon steel and is inlaid into the throat of the nozzle 8 by epoxy resin bonding.

[0088] The specific preparation steps are as follows:

[0089] ① Phenolic cloth rod 3721GB / T7819-200 was selected as raw material and manufactured into nozzle 8 shell through machining process to ensure that the throat diameter, convergence angle and expansion angle of nozzle 8 meet the design requirements.

[0090] ②The No. 45 carbon steel is processed into a nozzle steel throat liner 9 of the preset size;

[0091] ③ Using epoxy resin as an adhesive, the nozzle steel throat liner 9 is bonded and embedded into the throat of the nozzle 8 to form a complete nozzle throat structure, thus completing the nozzle assembly preparation.

[0092] In summary, phenolic resin rods have low density and good strength. The nozzle 8 housing made of this material effectively reduces the weight of the nozzle 8, thereby improving the overall performance of the engine. The nozzle throat liner 9 made of 45 carbon steel significantly reduces the ablation rate of the nozzle throat, solving the technical problem of high ablation rate of traditional nozzle throat liners, while ensuring that the nozzle 8 is lightweight and meets the working requirements of the engine well.

[0093] In one embodiment of the present invention, the engine igniter assembly 5 adopts a cage structure and consists of an igniter connector 11, a wiring screw 12, an ignition head 13, a covering layer 14, a cage-type propellant box 15, an ignition propellant 16, and a plug 17.

[0094] The igniter connector 11, the cage-type powder box 15, and the plug 17 are made of ABS plastic, and the covering layer 14 is aluminum foil, conforming to the BBT0030-2004 standard. The ignition powder 16 adopts the MHY-D (0.80~2.24) and MHY-D (0.25~0.4) / T-CSTM00361-2021 standards, with dosages of 4.5g and 2.5g respectively.

[0095] The wiring screw 12 is threaded into the pre-threaded hole of the igniter connector 11 to lead out the power line and realize the electrical connection with the onboard ignition control. The connector model is A950 / 20KB4SHN. The ignition head 13 is fixedly installed in the center of the cage-type propellant box 15 and is in direct contact with the ignition powder 16 to ensure that the ignition energy is effectively transferred to the ignition powder 16. The cage-type propellant box 15 is used to contain and fix the ignition powder 16 to ensure stable combustion of the ignition powder 16 and uniform transfer of ignition energy to the engine propellant 4. The covering layer 14 tightly wraps the outside of the cage-type propellant box 15 to provide heat insulation and protection for the ignition powder 16. The plug 17 is fixed to the end of the igniter connector 11 away from the engine propellant 4 by snap-fit ​​or adhesive, sealing the internal space of the igniter assembly to prevent impurities from entering and affecting the ignition reliability.

[0096] The engine ignition assembly 5 uses constant current electric ignition and is connected to the missile ignition control via a connector. The connector model is A950 / 20KB4SHN, the ignition voltage is 24V, the ignition current is not less than 2A, the duration is 20ms, and a redundant ignition scheme with two ignition elements is adopted, with an ignition delay time of <50ms.

[0097] The specific preparation steps are as follows:

[0098] ① Manufacture the igniter connector 11, wiring screw 12, ignition head 13, cage-type medicine box 15, and plug 17 according to the design dimensions and conventional processing technology;

[0099] ② Fix the ignition head 13 in the preset position inside the cage-type powder box 15, then mix HY-2 and HY-5 black powder evenly in proportion and put them into the cage-type powder box 15 to ensure that the ignition head 13 is in full contact with the ignition powder 16.

[0100] ③ Evenly attach the covering layer 14 to the outer surface of the cage-type medicine box 15 to ensure complete coverage;

[0101] ④ Insert the cage-shaped powder box 15, which is equipped with an igniter head 13, igniter powder 16 and a coating layer 14, into the internal cavity of the igniter connector 11, and screw the wiring screw 12 into the threaded hole of the igniter connector 11 so that one end of the wiring screw 12 is connected to the electrode of the igniter head 13.

[0102] ⑤ Install the plug 17 at the open end of the igniter connector 11 to complete the assembly of the engine igniter assembly 5.

[0103] In summary, using ABS plastic and phenolic cloth rods as the structural materials for engine igniter assembly 5 results in low manufacturing costs and a lighter weight compared to aluminum alloy structural components widely used in China, effectively improving engine performance. The cage-like structure design simplifies the igniter structure and facilitates assembly.

[0104] The ignition propellant 16 with a specific formula and dosage has been tested and verified to have the advantages of good ignition response performance and short ignition delay time, with an ignition delay of less than 50ms, which can meet the peak ignition pressure requirements of rocket projectiles; the redundant ignition scheme of two ignition elements further ensures the reliability of ignition and ensures that the engine can ignite and operate stably in a timely manner after receiving the launch command.

[0105] In one embodiment of the present invention, the connection between the engine housing 3 and the engine front end cap 1 and the engine rear end cap 6 is made of O-rings, and the material is silicone rubber, namely the front end cap sealing ring 2 and the rear end cap sealing ring 7.

[0106] Silicone rubber material has excellent sealing and heat resistance, which can meet the sealing requirements of various connections in the engine, prevent air leakage during engine operation, ensure stable engine operating pressure, and also has a certain degree of heat insulation, further improving the reliability and operational stability of the engine.

[0107] In one embodiment of the present invention, the engine assembly and testing scheme is as follows:

[0108] (1) Assembly scheme

[0109] ① The engine propellant 4, which is covered with a heat insulation layer and coated with a flame-restricting layer, is freely filled into the engine housing 3, and is initially positioned by the external thread of the outer circle of the propellant 4 and the internal thread of the engine rear end cap 6.

[0110] ② The front end of the engine housing 3 is connected to the front end of the engine head 1 by a thread. The front end sealing ring 2 is installed at the connection to seal it. Then the engine igniter assembly 5 is connected to the front end of the engine head 1 by a thread, ensuring that the ignition end of the igniter assembly 5 faces the front end of the engine propellant 4, so that the ignition energy can be effectively transferred to the propellant 4.

[0111] ③ The rear end of the engine housing 3 is connected to the engine rear end cap 6 by a thread. The rear end cap sealing ring 7 is installed at the connection to seal it. Then the engine nozzle 8 is connected to the engine rear end cap 6 by a thread. The connection is coated with sealant to ensure a reliable seal.

[0112] ④ Inspect the assembled engine, including weighing and recording, checking the center of gravity and calibrating it; the wiring screw 12 of the engine front igniter assembly 5 can be connected to the power copper wire. When the engine is stored, the two copper wires need to be short-circuited to ensure that the engine is in a safe state. When the engine is assembled onto the rocket, these two power wires are connected to the rocket power wire.

[0113] After the engine is assembled, the thrust line geometric deviation is ≤5', the geometric lateral displacement is ≤0.2mm, the average thrust relative deviation is ±3%, the operating temperature range is -30~50℃, the maximum normal overload is 3g, and the maximum lateral overload is 20g.

[0114] (2) Test plan

[0115] ① Shell 3 pressure test: The machined engine shell 3 is subjected to a water pressure test with a test pressure of 14MPa. The tensile strength of the shell 3 material after heat treatment is >550MPa. The working pressure of the shell 3 is 11MPa, the design pressure is 12MPa, and the burst pressure is 15MPa.

[0116] ② Internal ballistic performance simulation: Based on the overall performance requirements, internal ballistic performance simulation calculations are performed on the engine at -30℃, +20℃, and +50℃.

[0117] The results are as follows: at -30℃, the working time is 3.541s, the maximum pressure is 6.2MPa, the average pressure is 4.73MPa, the maximum thrust is 2098N, and the average thrust is 1442N; at +20℃, the working time is 3.125s, the maximum pressure is 8.85MPa, the average pressure is 6.65MPa, the maximum thrust is 2998N, and the average thrust is 2004N; at +50℃, the working time is 3.003s, the maximum pressure is 10.04MPa, the average pressure is 7.232MPa, the maximum thrust is 3349N, and the average thrust is 2213N.

[0118] ③ Ground ignition test: Conduct a high-temperature ground ignition test on the engine to verify whether the engine performance meets the design requirements.

[0119] Among them, the C1 engine (test temperature 18℃) has a total impulse of 5862 N·s, an operating time of 3.00 s, and an average thrust of 1843 N; the C2 engine (test temperature 18℃) has a total impulse of 5850 N·s, an operating time of 3.01 s, and an average thrust of 1821 N.

[0120] In summary, the engine adopts a loading assembly structure, which makes the engine propellant 4 and engine housing 3 have good maintainability and replaceability. It overcomes the problem of simultaneous scrapping of the housing and propellant due to heating deformation during the glass fiber / epoxy resin housing winding process, avoids scrapping the entire engine due to defects in the propellant or housing, reduces quality costs, and improves economic efficiency.

[0121] Rigorous hydrostatic testing of the casing 3 verified that its strength meets design requirements, with a design safety factor of 1.3, ensuring structural safety during engine operation. Internal ballistic performance simulation results show that the engine's operating time, maximum pressure, average pressure, maximum thrust, and average thrust under different temperature environments all meet design requirements. Ground ignition tests show that the engine's total impulse reaches 5862 N·s, with an average thrust exceeding 1800 N and a mass ratio close to 0.7. This allows it to propel 5 kg of extinguishing propellant to a fire zone 5 km away, fulfilling long-range flight requirements and filling a gap in domestic long-range fire-fighting rocket engines. Furthermore, the manufacturing processes for the loading engine and its components facilitate continuous production, making it particularly suitable for batch production, significantly reducing production costs and facilitating civilian application.

[0122] It should be noted that, in this invention, unless otherwise explicitly specified and limited, the terms "sliding," "rotating," "fixed," and "equipped" should be interpreted broadly. For example, they can refer to welded connections, bolted connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0123] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A solid-propellant engine for an environmentally friendly long-range firefighting rocket, characterized in that, Includes engine front end cap (1), front end cap sealing ring (2), engine housing (3), engine propellant (4), engine igniter assembly (5), engine rear end cap (6), rear end cap sealing ring (7), engine nozzle (8), nozzle steel throat liner (9), and nozzle plug (10). The engine front end cap (1) is threadedly connected to the engine housing (3), and a front end cap sealing ring (2) is fitted at the connection. The engine propellant (4) is filled into the engine housing (3) and is positioned by the external thread of the outer circle of the engine propellant (4) engaging with the engine rear end cap (6); One end of the engine rear end cap (6) is threaded to the engine housing (3), and a rear end cap sealing ring (7) is fitted at the connection. The other end is threaded to the engine nozzle (8). The nozzle steel throat liner (9) is embedded in the throat of the engine nozzle (8), and the nozzle plug (10) is sealed and assembled at the outlet end of the engine nozzle (8). The engine igniter assembly (5) is threaded to the engine front end cap (1), and the ignition end faces the engine propellant column (4).

2. The solid rocket motor for the environmentally friendly long-range fire-fighting rocket according to claim 1, characterized in that, The engine front end cap (1) and engine rear end cap (6) are both made of 7075 aluminum alloy; The engine housing (3) is made of 7075 aluminum alloy, the engine propellant (4) is a double cobalt double base propellant, and the engine igniter assembly (5) is a cage structure.

3. The solid rocket motor for the environmentally friendly long-range firefighting rocket according to claim 2, characterized in that, The engine housing (3) is manufactured by hot extrusion molding after being treated by the T6 heat treatment system, and the inner surface of the engine housing (3) is coated with heat insulation coating.

4. The solid rocket motor for the environmentally friendly long-range fire-fighting rocket according to claim 1, characterized in that, The inner core of the engine propellant grain (4) is an 8-star-shaped inner surface, and the outer surface is covered with a nylon base tape insulation layer with a thickness of 0.3mm, and the insulation layer is coated with a flame-limiting layer with a thickness of 0.2mm.

5. The solid rocket motor for the environmentally friendly long-range fire-fighting rocket according to claim 1, characterized in that, The engine nozzle (8) is a Laval nozzle, made of phenolic cloth rod, with a convergence angle of 90° and an expansion angle of 30°.

6. The solid rocket motor for the environmentally friendly long-range fire-fighting rocket according to claim 5, characterized in that, The nozzle steel throat liner (9) is made of No. 45 carbon steel and is embedded in the throat of the engine nozzle (8) by epoxy resin bonding.

7. The solid rocket motor for the environmentally friendly long-range firefighting rocket according to claim 1, characterized in that, The engine igniter assembly (5) includes an igniter connector (11), a wiring screw (12), an ignition head (13), a covering layer (14), a cage-type propellant box (15), an ignition propellant (16), and a plug (17). The igniter connector (11), cage-type powder box (15) and plug (17) are made of ABS plastic, the covering layer (14) is aluminum foil, and the ignition powder (16) is a mixture of HY-2 and HY-5 black powder; The ignition head (13) is fixed inside the cage-type medicine box (15) and in contact with the ignition powder (16). The cage-type medicine box (15) is wrapped with a covering layer (14) and is assembled into the internal cavity of the igniter connector (11). The wiring screw (12) is threaded to the igniter connector (11), and one end is connected to the electrode of the igniter head (13); The plug (17) is fixed to the end of the igniter connector (11) away from the engine propellant (4); The engine igniter assembly (5) adopts a constant current ignition method, with an ignition current of not less than 2A and a duration of 20ms, and adopts a redundant ignition scheme with two ignition elements.

8. The solid rocket motor for the environmentally friendly long-range firefighting rocket according to claim 1, characterized in that, Both the front end cap sealing ring (2) and the rear end cap sealing ring (7) are made of silicone rubber.

9. A method for preparing a solid-propellant engine for an environmentally friendly long-range firefighting rocket, used to prepare the solid-propellant engine for the environmentally friendly long-range firefighting rocket according to any one of claims 1-8, characterized in that, Includes the following steps: Step 1: Engine housing processing: After solution treatment of 7075 aluminum alloy under T6 heat treatment system, it is cut into blanks, hot extruded into the prototype of engine housing (3), after aging treatment, it is precision machined, and finally the inner surface is sprayed with heat insulation coating. Step 2: Engine propellant grain forming: The raw material of the double cobalt double base propellant grain is extruded and formed by a screw press, and after being cut, it is covered with a nylon base tape heat insulation layer and coated with a flame-restricting layer. Step 3: Nozzle manufacturing: The Laval nozzle shell is manufactured by phenolic cloth rod machining, and the No. 45 carbon steel is processed into a nozzle steel throat liner (9), which is then bonded to the nozzle throat with epoxy resin and the nozzle plug (10) is assembled. Step 4: Igniter fabrication: Process the various parts of the igniter, assemble the ignition head (13) and ignition powder (16) into the cage-type powder box (15), wrap the covering layer (14) and then assemble it together with the wiring screw (12) and the plug (17) into the igniter connector (11). Step 5: Component assembly: Fill the engine propellant (4) into the engine housing (3), connect the engine front end cap (1), engine igniter assembly (5), engine rear end cap (6) and engine nozzle (8) in sequence, and assemble the corresponding sealing rings; Step 6: Testing and Inspection: Conduct a casing hydrostatic test and a ground ignition test on the assembled engine.

10. The method for preparing a solid rocket motor for an environmentally friendly long-range firefighting rocket according to claim 9, characterized in that, In step 1, the aging treatment temperature is 200℃ and the treatment time is 3 hours; the heat insulation coating is GT-401 heat insulation coating with a coating thickness of 0.1mm.

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