An experimental bench for studying the effects of acceleration on the linear burning rate of solid rocket propellants.

Abstract

The subject of the present invention is an experimental bench for studying the effect of acceleration on the linear burning rate of solid rocket propellants. The experimental bench for studying the effect of acceleration on the linear burning rate of solid rocket propellants according to the present invention comprises a DC electric motor with an encoder, an energy storage module, a power supply system for an ignition device, an electronic pressure measurement system in a combustion chamber, and a rocket micromotor. The electric motor is connected to the encoder and is connected to a main shaft by a bellows-type connection, on which the energy storage module is arranged. Opposite the body of the rocket micromotor arranged on the main shaft by a fastening device, the power supply system for the ignition device is arranged, mounted on the main shaft, and comprises a sleeve of the power supply system, on which a conductive ring and an insulating ring are arranged, the sleeve being terminated by a closing ring, and carbon brushes. The electronic pressure measurement system in the combustion chamber comprises a pressure sensor arranged in a pressure sensor socket, the socket being connected to the body of the solid rocket micromotor by a pressure measurement port. Further, the threaded end of the main shaft is provided with an attachment portion for a main body portion of a rocket micromotor including the combustion chamber having an internal recovery groove portion, the pressure measurement port, a safety valve port having a safety valve, and an outlet socket arranged on the side of the main body portion of the rocket micromotor.

Description

[Technical field]

[0001] The subject of this invention is an experimental platform for studying the effects of acceleration on the linear burning rate of solid rocket propellants. [Background technology]

[0002] As of now, no solution has been found in the country by reviewing the available literature to study the effect of acceleration (rotational motion) on the linear burning rate of solid rocket propellants.

[0003] JB Anderson and RE Reichenbach, "An Investigation of the Effect of Acceleration on the Burning Rate of Composite Propellants", AIAA Journal Vol.6 No.2,Feb 1968; Melvin John Bulman, "The effect of Acceleration on the Burning Rate of Double Base Rocket Propellants", Ph.D.Thesis,USNaval Postgraduate School,1968; Soe Hlaing Tun and Xiang Hong Jun, "Star Grain Regression Under Spin Induced Acceleration Effect", Applied Mechanics and Materials,Vols.110-116,pp 451-456,2011 doi:10.4028 / www.scientific.net / AMM.110-116.451, and the publication by David R. Greatrix, "Assessing the Influence of Orientation Angle on Acceleration-Augmented Burning in Solid Rockets", AIAA, 2018, provide the results of ongoing experimental and computer simulation studies of the effect of acceleration on the burning rate of solid rocket propellants, but the details of the test bench design have not been disclosed. Summary of the Invention [Means for solving the problem]

[0004] The experimental bench for studying the effect of acceleration on the linear burning rate of solid rocket propellants according to the present invention comprises a DC electric motor with an encoder, an energy storage module, a power supply system for an ignition device, an electronic pressure measurement system in a combustion chamber, and a rocket micromotor. The electric motor is connected to the encoder and is connected to a main shaft by a bellows-type connection, on which the energy storage module is arranged. On the opposite side of the body of the rocket micromotor arranged on the main shaft by a fastening device, the power supply system for the ignition device is arranged, which is mounted on the main shaft, and which comprises a power supply system sleeve, on which a conductive ring and an insulating ring are arranged, which is terminated by a closing ring, and carbon brushes. The electronic pressure measurement system in the combustion chamber includes a pressure sensor arranged in a pressure sensor socket, which is connected to the body of the solid rocket micromotor by a pressure measurement port. Further, the threaded end of the main shaft is provided with an attachment portion for a main body portion of the rocket micromotor including the combustion chamber, the pressure measurement port, a safety valve port having a safety valve, and an outlet socket arranged on the side of the main body portion of the rocket micromotor, the attachment portion having an internal recovery groove portion.

[0005] The front portion of the electric motor is preferably connected to a mounting portion of the electric motor.

[0006] The main shaft is preferably supported on a first bearing unit and a second bearing unit.

[0007] The first bearing unit preferably includes a double row angular contact ball bearing housed in a housing attached to the laboratory bench base.

[0008] The second bearing unit preferably comprises a double row angular contact ball bearing secured within a housing by two internal spring loaded circlips.

[0009] Preferably, two lithium polymer batteries are symmetrically arranged on either side of the main shaft.

[0010] The power system sleeve preferably includes four conductive rings and three insulating rings.

[0011] Preferably, the carbon brush is disposed within the socket in contact with the conductive ring by a spring fastening system disposed within the socket.

[0012] The socket is preferably located in the base of the power system.

[0013] The rocket micromotor body is preferably connected to the body mounts by six threaded rods with nuts.

[0014] The pressure sensor socket preferably has a cavity for a pressure sensor insert, a filter, and a distal sleeve closed by a tightening nut.

[0015] The safety valve preferably comprises a safety membrane.

[0016] The outlet socket preferably includes a nozzle insert (31).

[0017] Preferably, a membrane is disposed between the nozzle insert and the outlet socket.

[0018] The power supply system for the ignition device preferably includes an electric detonator and a disk-shaped diamond-shaped explosive contained within a housing sealed by an O-ring.

[0019] The present experimental bench allows to carry out experimental tests to determine the effect of acceleration acting on the solid propellant placed in the combustion chamber of a solid rocket micromotor on the relationship between the linear burning rate and the pressure in the combustion chamber. Furthermore, the change in the performance of the test motor resulting from the pressure change in the combustion chamber due to centrifugal acceleration can be determined. This is an important issue from the point of view of the application of rocket motors, regardless of whether they are main drive motors, auxiliary motors or control motors. During flight, rocket missiles are subjected to large g-value accelerations (related to the acceleration of gravity). During the accelerated or rotating flight of an object equipped with a solid propellant motor, the burning rate of the grains of the solid propellant changes depending on the value of this acceleration. Since the linear burning rate is a fundamental parameter that describes the characteristics of solid rocket propellants, knowing the effect of acceleration on the linear burning rate value allows to determine the limit of safe operation of the combustion chamber (maximum operating pressure), the change in the thrust profile of the motor over time and, as a result, the change in the flight range or altitude of an object powered by a solid propellant rocket motor.

[0020] The following technical solutions were used: Experimental solid rocket micromotor: mounted on the end of a drive shaft, it makes it possible to carry out experimental combustion of test samples to determine the linear burning rate of solid rocket propellants under conditions where the acceleration acting on the propellant grains is of known value. An electric drive in the form of a DC electric motor (with an encoder for measuring the rotational speed), the purpose of which is to generate an appropriate value of acceleration by centrifugal acceleration (obtained by setting the rotational speed of the micromotor under test to an appropriate value). A system for measuring the pressure in the combustion chamber using a pressure sensor, an amplification system and data recorded on a memory card. This system allows to measure the pressure at a frequency of 2 kHz during the action of accelerations affecting the grains of solid rocket propellant. Ignition system control system and measurement of electrical parameters during operation. Measurement cards and dedicated software for measurement data acquisition.

[0021] In the design of the test bench, several component systems can be distinguished. Drive module: an electric motor with an encoder that rotates the solid rocket micromotor via the main shaft. Two bearing supports for the main shaft (one of the supports allows compensation of shaft assembly errors). Energy storage module (for supplying the combustion chamber pressure measurement system). A three-channel ignition power supply system consisting of an ignition unit and a pyrotechnic ignition device. An experimental solid rocket micromotor, and the necessary mechanical interface attached to the end of the shaft.

[0022] The following steps are performed during operation of the lab bench: Installation of the correct nozzle membrane (nozzle plug) and safety membrane. Start-up of the electronic measuring system (measuring card, combustion chamber pressure measuring system). The tested propellant sample was placed in the combustion chamber. Place the igniter into the corresponding socket on the body of the rocket micromotor. Setting the desired acceleration (setting the appropriate rotation speed of the driving DC electric motor by controlling the power supply voltage value). Start the measurement system and the data acquisition program (press the READY button in the data acquisition program to go to standby state) and start the ignition system (unlock the safety button). Carrying out the experiment (automatically starting the drive electric motor using the measuring card, then after a few seconds the ignition start system is activated and after a pre-programmed time all measurement data except the pressure in the combustion chamber is automatically recorded in the computer). Stopping the ignition start system (pressing the safety button and the STOP button in the data collection program) and transferring the measurement data of the pressure in the combustion chamber from the memory card to the computer memory. Performing operating procedures (disassembling the ignition device, cleaning the combustion chamber, cleaning the outlet nozzle, replacing the nozzle membrane). [Brief description of the drawings]

[0023] The object of the invention is illustrated in the drawings as an embodiment. [Figure 1] FIG. 1 shows an axonometric 3 / 4 view with a cutaway internal view of a quarter of the body. [Diagram 2] Figure 2 shows a detailed (exploded) view of the experimental solid rocket micromotor. [Diagram 3] FIG. 3 shows a detailed diagram of the power supply system for the ignition device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The subject of the invention is an experimental bench for studying the effect of acceleration on the linear burning rate and the pressure in the combustion chamber of a solid rocket propellant sample, which makes it possible to determine the effect of acceleration on the nature of the relationship between the burning rate and the pressure in the combustion chamber (constant, linear, etc.), as well as on the changes in the performance of the rocket motor under test resulting from the pressure changes in the combustion chamber due to centrifugal acceleration.

[0025] The experimental bench for studying the effect of acceleration on the linear burning rate of solid rocket propellants according to the present invention is designed to determine the effect of acceleration on the nature of the relationship between the linear burning rate and the pressure in the combustion chamber, and the effect of acceleration on the changes in performance of a solid rocket micromotor under test resulting from pressure changes in the combustion chamber due to centrifugal acceleration (created by the rotational motion of the rocket micromotor).

[0026] The invention includes several basic components, including an electric drive module, a two-bearing shaft support, an energy storage module, a power supply system for the ignition device, an electronic pressure measurement system in the combustion chamber, and an experimental solid rocket micromotor (with an appropriate mechanical interface connected to the end of the main shaft of the main laboratory stand).

[0027] The electric drive module includes an electric motor (1) supplied with a constant voltage in the range of 6-27 V and an associated encoder (2) for determining the rotational speed of the electric motor. The front of the electric motor (1) is connected to the motor's angle mount (3) by four hexagon socket head bolts. The electric motor mount (3) is fixed to the lab bench base (42) by four hexagon socket head screws (Allen screws). Four handles (43) are also bolted to the lab bench base (42) to facilitate handling of the assembled bench. The key component of the drive module is the main shaft (5), which is connected to the electric motor (1) by a (wobble-free) bellows-type connection (4), which compensates for possible shaft misalignment errors and damps vibrations caused by uneven weight distribution in the rotating system.

[0028] The main shaft is supported at two points by a first bearing unit (6) and a second bearing unit (7). The first bearing unit (6) includes a double row angular contact ball bearing arranged with play in a mounting part arranged in a housing that also serves as a component for mounting the first bearing unit to the lab bench base (42). The second bearing unit (7) is an almost identical set, the only difference being that the bearings are fixed in the mounting part by two internal spring-loaded circlips. The bearings employed are arranged so that the bearings of the first bearing unit have play and the bearings of the second bearing unit are fixed.

[0029] Another component installed on the main shaft (5) is an energy storage module (8) that is used to power the electronic pressure measurement system in the combustion chamber (44). The energy storage module (8) is contained within a housing and includes two lithium polymer batteries that are symmetrically positioned on either side of the main shaft (5).

[0030] The energy storage module (8) is seated on the shaft and is prevented from rotation relative to the shaft axis by a parallel key and from longitudinal movement by an external circlip. The supply lines between the energy storage module (8) and the pressure measurement system are routed through specially provided holes inside the shaft. This cabling allows the drive shaft to rotate freely.

[0031] The three-channel igniter power supply system (B) (see FIG. 3) includes a power supply sleeve (9) on which four conductive (slip) rings (10) and three insulating rings (11) are arranged in alternating fashion and terminated in a closed ring (12). Three conductive rings (10) are used to carry three independent positive power channels, and the fourth conductive ring (10) is the common ground for the power channels. This arrangement makes it possible to power up to three independent igniter modules.

[0032] The components of the ignition power supply system (B) are seated on the shaft (5), rotation is prevented by a parallel key and longitudinal movement is prevented by an external circlip. The elements that transmit power to the three-channel ignition power supply system (B) are four carbon brushes (16) arranged in sockets (15) and in contact with the conductive rings (10). The sockets for the carbon brushes are mounted in the base (14) of the power supply system, through which pins (13) fixed on both sides of the base (14) pass, allowing them to move transversely to the axis of the shaft (5). The system of pressing the carbon brushes against the conductive ring is based on the use of a spring arranged in the socket (15), the entire carbon brushes being pressed by a ball set screw (17) screwed into the corresponding wall of the base (14), where the ball surface of the set screw is in contact with the housing of the sockets for the carbon brushes. The base (14) of the power supply system is secured to the lab bench base (42) with two hexagon socket head bolts. Electrical wires are soldered to the inner surface of each conductive ring (10), and the resulting wiring bundle is routed through holes in the inner surface of the closure ring (12), through holes in the shaft extending transversely to the shaft axis, and through holes in the shaft face, near the end face of the shaft (5).

[0033] The electronic pressure measurement system (44) in the combustion chamber includes a pressure sensor (36) placed in a socket (35) connected to the body part (21) of the solid rocket micromotor (A) through a special port (33), a circuit for normalizing and amplifying the measurement signal to a standard 0-10 V analog voltage, and a circuit for supplying power to said measurement sensor. The entire system is built on a circular common PCB with a hole in the center and placed in a sealed state in a housing. The housing of the measurement system is attached to the shaft by a keyed connection and an external circlip.

[0034] At the threaded end of the shaft (5) is placed the prismatic keyed mounting (20) of the solid rocket micromotor body and bearing fixing washer MB3 (18), and the whole is fastened with a bearing fixing nut (19). At the center of the experimental solid rocket micromotor body (detailed in Figure 2), the rocket micromotor (A) body (21) is connected to the mounting (20) by six threaded rods and fastened with nuts. Such a number of rods ensures adequate strength of the structural connection.

[0035] The combustion chamber (22) is placed in said body with the grains of solid rocket propellant. The use of a "basket" shaped combustion chamber (22) terminating in an integral grate and having three tapped holes (M3 metric thread) in the side wall used for pressurized screwing of the set screws (29) ensures that the central position of the propellant grains (23) is maintained at the beginning of the experiment and facilitates the ignition process over the entire available surface of the grains. The use of a grate with a number of through holes appropriately selected according to the cross section of the critical diameter of the nozzle prevents the dangerous phenomenon of clogging of the outlet nozzle with detached grain fragments and the resulting damage of the experimental platform. Furthermore, the combustion chamber (22) comprises an external collection channel (30) for collecting exhaust gases and transferring them to the main body (21) of the rocket micromotor, a pressure measurement port (33), a safety valve port (24) and an exhaust gas dispersion tip (26).

[0036] The body (21) of the solid rocket micromotor (A) is equipped with a threaded pressure measurement port (33) into which a pressure sensor socket (35) with a cavity for a special insert (34) and a filter (45) is screwed. This port serves to reduce the flow of solid particles of the combustion products impinging on the surface of the sensor membrane (36) while maintaining the appropriate conditions for a reliable measurement of the pressure in the combustion chamber. The pressure sensor (36), a distal sleeve (37) made of polyamide, is placed in the socket (35) and the whole is closed by a tightening nut (38). The sleeve (37) prevents the pressure sensor socket (35) from moving along its axis. The shape of the insert (34) corresponds to the manufacturer's recommendations for the assembly of the pressure sensor used.

[0037] The body also includes a safety valve (26) with a replaceable safety membrane (25), which screws into the safety valve port (24). If a specified allowable pressure is exceeded, a plate located on the safety valve breaks, essentially opening an additional vent to reduce pressure in the combustion chamber. This bleed system eliminates the possibility of destroying the test bench.

[0038] On one side of the body (21) of the solid rocket micromotor (A), the outlet nozzle socket (27) is attached by sliding movement to a threaded rod, which is screwed into the body (21) of the solid rocket micromotor (A) and further fastened with a nut. The replaceable nozzle insert (31) is attached to a special clamp (32) and sealed with a Viton® O-ring. The nozzle part thus prepared is screwed into the outlet nozzle socket (27). The space between the nozzle insert (31) and the nozzle socket (27) provides a mounting surface for the membrane (28) which acts as a nozzle plug. The purpose of this plug is to maintain the correct pressure value in the combustion chamber at the beginning of the combustion process, which greatly simplifies the starting of the combustion chamber and improves the accuracy of the measurement of the combustion time. The plug (28) allows the starting of the solid rocket micromotor (A) when the pressure in the combustion chamber is low. The proper selection of the nozzle plug can reduce the pressure rise time in the motor chamber (22) and improve ignition characteristics, which in turn has a significant effect on the subsequent combustion process and rocket motor performance.

[0039] On the opposite side of the body part (21) of the solid rocket micromotor (A) is the igniter part, which serves to start the combustion process in the shortest possible time and in a manner that is reproducible in subsequent experiments. According to the invention, to start the ignition, an electric detonator (40) and a black powder bed (41) in the form of a disk-like diamond, placed in the housing (39), are used (the design of the igniter has been developed so that black powder in the crushed state can also be used). The igniter thus prepared is equipped with a male metric thread, a Viton® O-ring seal and a hexagonal head for easy fastening, and is attached to the body part (21) of the solid rocket micromotor (A). The use of an exchangeable igniter housing (39) allows the use of several types of igniters (40) with different geometric dimensions.

[0040] The tightness of the connections between the main components of the experimental solid rocket micromotor (A) (the ignition device, the nozzle, the pressure reduction device in the combustion chamber, and the pressure measurement device) is achieved by using Viton® O-ring seals. [Explanation of symbols]

[0041] A Solid Rocket Micromotor B. Ignition power supply system 1 DC electric motor 2 Encoder 3 Electric motor mounting part 4 Bellows type (no rattle) connection 5 Main shaft 6 First bearing unit 7 Second bearing unit 8 Energy storage module (battery) 9 Power System Sleeve 10 Conductive Ring 11 Insulation ring 12 Closure Ring 13-pin 14 Power System Base 15 Carbon Brush Socket 16 Carbon Brush 17 Ball set screw 18 Bearing fixing washer MB3 19 Bearing fixing nut KM3 20 Main body attachment part 21 Solid-state micromotor body 22 Combustion chamber with grate (basket-shaped) 23 grains (propellant) 24 Safety valve port 25 Safety membrane 26 Safety valve 27 Outlet nozzle socket 28 Nozzle membrane 29 Setscrew 30 Collection groove 31 Nozzle insert 32 Clamp for outlet nozzle 33 Pressure measurement port 34 Pressure sensor insert 35 Pressure sensor socket 36 Pressure Sensor 37 Distal Sleeve 38 Pressure sensor tightening nut 39 Ignition housing 40 Electric detonator 41 Diamond-shaped explosives 42 Experimental bench base 43 Handle 44 Electronic pressure measurement system in the combustion chamber 45 Filters

Claims

1. 1. An experimental platform for studying the effect of acceleration on the linear burning rate of solid rocket propellants, comprising: The invention comprises a DC electric motor (1) having an encoder (2), an energy storage module (8), a power supply system (B) for an ignition device, an electronic pressure measurement system (44) in a combustion chamber (22), and a solid rocket micromotor (A), the electric motor (1) is connected to the encoder (2) and to a main shaft (5) by a bellows-type connection (4), the energy storage module (8) being disposed on the main shaft (5); On the opposite side of the body (21) of the solid rocket micromotor (A) arranged on the main shaft (5) by a fastening device (20), there is arranged a power supply system (B) for the ignition device mounted on the main shaft (5), the power supply system (B) for the ignition device comprising a power supply system sleeve (9) on which a conductive ring (10) and an insulating ring (11) are arranged and which is terminated by a closing ring (12), the power supply system sleeve (9) and carbon brushes (16); the electronic pressure measurement system (44) in the combustion chamber (22) includes a pressure sensor (36) disposed in a socket (35) for the pressure sensor (36), the socket (35) being connected to the body (21) of the solid rocket micromotor (A) by a pressure measurement port (33); Further, the threaded end of the main shaft (5) is provided with an internal recovery groove (30) for mounting the main body (21) of the solid rocket micromotor (A) including the combustion chamber (22), the pressure measurement port (33), a safety valve port (24) having a safety valve (26), and an outlet socket (27) arranged on the side of the main body (21) of the solid rocket micromotor (A). Guinea pig.

2. 2. The laboratory bench according to claim 1, characterized in that the front part of the electric motor (1) is connected to a mounting part (3) of the electric motor (1).

3. 2. The laboratory bench according to claim 1, characterized in that the main shaft (5) is supported on a first bearing unit (6) and a second bearing unit (7).

4. 4. The laboratory bench according to claim 3, wherein the first bearing unit (6) comprises a double row angular contact ball bearing housed in a housing attached to a laboratory bench base (42).

5. 5. The laboratory bench according to claim 3 or 4, characterized in that the second bearing unit (7) comprises a double row angular contact ball bearing fixed in a housing by two internal spring-loaded circlips.

6. 2. The laboratory bench according to claim 1, characterized in that it comprises two lithium polymer batteries arranged symmetrically on either side of the main shaft (5).

7. 2. A laboratory bench according to claim 1, characterized in that the sleeve (9) of the power supply system comprises four conductive rings (10) and three insulating rings (11).

8. 8. The laboratory bench according to claim 1 or 7, characterized in that the carbon brush (16) is arranged in the socket (15) in contact with the conductive ring (10) by a spring fastening system arranged in the socket (15).

9. 9. A laboratory bench according to claim 1 or 8, characterized in that the socket (15) is arranged at the base of the power supply system.

10. 2. The experimental bench according to claim 1, characterized in that the body part (21) of the solid rocket micromotor (A) is connected to the mounting part (20) of the body part (21) by six threaded rods with nuts.

11. 2. The laboratory bench according to claim 1, characterized in that the socket (35) for the pressure sensor (36) has a cavity for an insert (34) for the pressure sensor (36), a filter (45) and a distal sleeve (37) closed by a tightening nut (38).

12. 2. The laboratory bench according to claim 1, characterized in that the safety valve (26) comprises a safety membrane (25).

13. 2. The laboratory bench according to claim 1, characterized in that the outlet socket (27) includes a nozzle insert (31) disposed in a clamp (32).

14. 2. The laboratory bench according to claim 1, characterized in that a membrane (28) is arranged between the nozzle insert (31) and the outlet socket (27).

15. 2. The test bench according to claim 1, wherein the power supply system (B) for the ignition device includes an electric detonator (40) and a disk-shaped diamond-shaped explosive (41) housed in a housing (39) sealed with an O-ring.

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