Accurate collection device for solid propellant condensed phase particles and collection method thereof

Abstract

The invention discloses an accurate collection device and method for solid propellant condensed phase particles, and the device comprises a combustion chamber which is a hollow cylinder, and the top of the hollow cylinder is provided with an upper sealing cover; the upper sealing cover is connected with an actuating device, and a push rod of the actuating device is movably and hermetically connected with the upper sealing cover; the bottom end of the push rod is used for mounting a solid propellant; a sleeve is arranged on the periphery of the solid propellant; a collecting cavity is formed in the bottom of the combustion chamber, and quenching liquid is contained in the collecting cavity; the sleeve is arranged on the periphery of the solid propellant, it can be guaranteed that combustion of the solid propellant is completed in the space of the sleeve, that is, the combustion range of the solid propellant is limited through the sleeve, the combustion environment tends to be consistent with a real combustion chamber, and the experiment accuracy is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid propellant condensed phase particle collection, and particularly relates to a precise collection device for solid propellant condensed phase particles and a collection method thereof. Background Art

[0002] Condensed phase product collection is a test method in which propellant is burned in a constant volume combustion chamber, and the generated condensed phase particles are quenched and cooled by liquid or gas to obtain the condensed phase products generated by the combustion of aluminum particles in the propellant. By analyzing the condensed phase products, the physical and chemical properties such as the particle size, composition, and morphology of the aggregates during the combustion process of the propellant can be obtained. Therefore, this method is widely used to study the aluminum agglomeration on the burning surface of the propellant and the combustion of aluminum particles in the engine environment.

[0003] However, when collecting the condensed phase products, due to the different combustion environments between the constant volume combustion chamber and the actual combustion chamber, the collected condensed phase products are different from the actually generated condensed phase products, which brings certain errors to the subsequent analysis process. Summary of the Invention

[0004] The purpose of the present invention is to provide a precise collection device for solid propellant condensed phase particles and a collection method thereof, so that the combustion environment of the combustion test is more consistent with the actual combustion chamber.

[0005] The present invention adopts the following technical solutions: A precise collection device for solid propellant condensed phase particles, including a combustion chamber, the combustion chamber is a hollow cylinder, and the top of the hollow cylinder has an upper cover;

[0006] The upper cover is connected with an actuating device, and the push rod of the actuating device is movably and hermetically connected with the upper cover;

[0007] The bottom end of the push rod is used for installing solid propellant;

[0008] A sleeve is arranged on the periphery of the solid propellant;

[0009] A collection chamber is arranged at the bottom of the combustion chamber, and there is quenching liquid in the collection chamber.

[0010] Further, the inner wall surface of the sleeve has the same shape as the outer peripheral surface of the solid propellant.

[0011] Further, the sleeve is installed in the combustion chamber through a clamp seat.

[0012] Further, the inner circumference of the clamp seat is fixedly connected with the outer wall of the sleeve, and the outer ring of the clamp seat is fixedly installed between the upper cover and the combustion chamber.

[0013] Further, the collection chamber is a housing with an open top;

[0014] There is a tube body with both ends open in the housing, and the bottom end of the tube body is fixedly connected with the inner bottom surface of the collection chamber;

[0015] The cross-section of the tube body is the same as the cross-sectional shape of the solid propellant.

[0016] Furthermore, the height of the tube body is the same as the height of the collection chamber.

[0017] Furthermore, the top of the tube body has a movable baffle plate.

[0018] Furthermore, the actuating device is installed on the upper bracket; wherein, the actuating device can drive the upper cover to move up and down through its push rod.

[0019] Furthermore, the combustion chamber is installed on a laterally arranged guide rail; wherein, the guide rail is used to drive the combustion chamber to move laterally.

[0020] Another technical solution of the present invention: A method for precisely collecting solid propellant condensed phase particles, using the above-mentioned solid propellant condensed phase particle precise collection device, specifically including the following steps:

[0021] Determine the starting time of the actuating device according to the ignition time of the solid propellant.

[0022] The beneficial effect of the present invention is that by arranging a sleeve around the solid propellant, it can ensure that the solid propellant burns within the sleeve space, that is, the combustion range of the solid propellant is limited by the sleeve, making the combustion environment closer to that of a real combustion chamber and improving the experimental accuracy. Brief Description of the Drawings

[0023] Figure 1 It is a schematic structural diagram of a solid propellant condensed phase particle precise collection device according to an embodiment of the present invention;

[0024] Figure 2 It is a schematic internal structure diagram of the combustion chamber in an embodiment of the present invention;

[0025] Figure 3 It is a schematic diagram of the principle of the actuating device control system in an embodiment of the present invention;

[0026] Figure 4 It is a schematic diagram of the combustion chamber pressure and the input signal of the exhaust solenoid valve in an embodiment of the present invention;

[0027] Figure 5 It is a schematic diagram of the combustion chamber pressure and the output signal of the ignition power supply in an embodiment of the present invention;

[0028] Figure 6 It is a test result diagram of the ignition delay repeatability measurement test in an embodiment of the present invention;

[0029] Figure 7 It is a schematic diagram of the control timing of the system in an embodiment of the present invention;

[0030] Figure 8 Schematic diagram of the test system in the embodiment of the present invention;

[0031] Figure 9 SEM image and particle size distribution diagram of the CCPs collected in the embodiment of the present invention;

[0032] Figure 10 SEM image, combustion efficiency and particle size distribution diagram of CCPs at different quenching distances in the embodiment of the present invention;

[0033] Figure 11 Particle size distribution diagram of CCPs at different quenching distances and collection regions in the embodiment of the present invention;

[0034] Figure 12 Combustion efficiency diagram of CCPs of LP propellant at different quenching distances and collection regions in the embodiment of the present invention;

[0035] Figure 13 SEM images of CCPs in the central regions of (a) LP180-C and (b) LP180-T at different collection times in the embodiment of the present invention;

[0036] Figure 14 Combustion efficiency diagram of CCPs of LP180 at different collection times in the embodiment of the present invention;

[0037] Figure 15 Particle size distribution diagram of CCPs at different collection times in the embodiment of the present invention;

[0038] Figure 16 SEM images of CCPs of propellants with diameters of (A) 20mm (B) 15mm (C) 10mm (D) 5mm in the embodiment of the present invention;

[0039] Figure 17 Particle size distribution diagram of CCPs collected at different burning surfaces in the embodiment of the present invention;

[0040] Figure 18 Variation trend diagram of the combustion efficiency of CCPs with the burning surface diameter of the propellant in the embodiment of the present invention;

[0041] Figure 19 Temperature distribution diagram in the sleeve at the 1s moment of propellants with burning surface diameters of (A) 20mm, (B) 15mm, (C) 10mm, (D) 5mm in the embodiment of the present invention;

[0042] Figure 20 XRD analysis diagram of the propellant CCPs in the embodiment of the present invention.

[0043] Wherein: 10. Actuating device; 11. Push rod;

[0044] 20. Combustion chamber; 21. Clamping seat; 22. Sleeve; 23. Collection chamber;

[0045] 30. Upper bracket; 40. Guide rail; 50. Lower bracket; 60. Solid propellant. Detailed implementation manner

[0046] The present invention will be described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0047] Analysis of the current research status reveals that there are two defects in the existing methods for collecting condensed-phase products: Firstly, the factor of the recession of the propellant burning surface on the quenching distance is not considered during the collection process. The quenching distance between the propellant burning surface and the collection liquid surface determines the combustion travel of the condensed-phase particles after leaving the burning surface. The shorter the quenching distance, the shorter the combustion time of the condensed-phase particles, and the closer the collected condensed-phase products are to the initial state on the burning surface. However, as the propellant burns, the recession of the burning surface causes the quenching distance to gradually increase. When the propellant size is much larger than the initial quenching distance (2 - 5 mm), the influence of propellant combustion on the quenching distance cannot be ignored. Secondly, during the test, the propellant size is small, and there is a heat and mass transfer process between the generated gas and the surrounding cold air flow, resulting in a difference between the combustion environment of the aluminum particles and the real engine combustion chamber. In order to characterize the combustion evolution process of aluminum particles in the engine combustion chamber, the test conditions need to be close to the engine combustion chamber environment.

[0048] The present invention discloses a precise collection device for solid propellant condensed-phase particles, as Figure 1 and Figure 2 shown, which includes a combustion chamber 20. The combustion chamber 20 is a hollow cylinder with an upper cover at the top of the hollow cylinder; the upper cover is connected with an actuating device 10, and the push rod 11 of the actuating device 10 is movably and hermetically connected to the upper cover; the bottom end of the push rod 11 is used to install the solid propellant 60; a sleeve 22 is arranged on the periphery of the solid propellant 60; a collection chamber 23 is arranged at the bottom of the combustion chamber 20, and there is quenching liquid in the collection chamber 23.

[0049] The present invention can ensure that the solid propellant 60 burns within the sleeve space by arranging a sleeve on the periphery of the solid propellant 60, that is, the combustion range of the solid propellant 60 is limited by the sleeve, making the combustion environment tend to be consistent with the real combustion chamber, and improving the experimental accuracy.

[0050] In one embodiment, the inner wall surface of the sleeve 22 has the same shape as the outer peripheral surface of the solid propellant 60, and moreover, the gap between the inner wall surface of the sleeve 22 and the outer peripheral surface of the solid propellant 60 is uniform, so as to ensure the uniform temperature within the entire sleeve 22.

[0051] Specifically, the sleeve 22 is installed in the combustion chamber 20 through the clamping seat 21. The inner circumference of the clamping seat 21 is fixedly connected to the outer wall of the sleeve 23, and the outer ring of the clamping seat 21 is fixedly installed between the upper cover and the combustion chamber 20. The inner circumference of the clamping seat 21 can be a ring body, which is fixedly connected to the sleeve. The outer circumference of the clamping seat can be processed into a flange shape, and the outer circumference of the clamping seat is arranged between the connecting flanges of the upper cover and the combustion chamber like a gasket, so as to facilitate installation.

[0052] The collection chamber 23 is a housing with an open top; there is a tube body with both ends open inside the housing, and the bottom end of the tube body is fixedly connected to the inner bottom surface of the collection chamber 23; the cross-section of the tube body is the same as the cross-section shape of the solid propellant 60. By setting the tube body, the collection chamber 23 can be divided into an intermediate region and a peripheral region.

[0053] More specifically, the height of the tube body is the same as the height of the collection chamber 23, and the top of the tube body has a movable baffle plate. The baffle plate can be operated by other power devices. For example, the baffle plate is installed on the output shaft of the motor, and the motor can be installed inside or outside the combustion chamber. When installed inside the combustion chamber, its installation position needs to be considered to ensure that its operation is not affected by the combustion of the solid propellant 60 and does not affect the movement of the condensed-phase products. When installed outside the combustion chamber, attention needs to be paid to the sealing problem between the motor shaft and the combustion chamber housing. Through the power output of the motor, the baffle plate can block or open the top opening of the tube body.

[0054] The actuating device 10 is installed on the upper bracket 30; wherein, the actuating device 10 can drive the upper cover to move up and down through its push rod 11. Through the design of the upper bracket 30, the upper cover of the combustion chamber 20 can be opened by the actuating device 10, reducing manual work.

[0055] Based on the same principle, the combustion chamber 20 is installed on the laterally arranged guide rail 40; wherein, the guide rail 40 is used to drive the combustion chamber 20 to move laterally. The guide rail 40 is installed on the lower bracket 50. Through the setting of the guide rail 40, the lateral movement of the combustion chamber 20 can be facilitated, and it can be moved out of the range of the upper bracket 30, facilitating the installation of the collection chamber 23 and the solid propellant 60.

[0056] The device of the present invention can not only realize the function that the quenching distance of the condensed-phase products is always constant during the whole collection process, but also make the combustion environment of the aluminum particles close to that of a real engine. On this basis, the influence of the quenching distance and the combustion environment on the condensed-phase products is verified by using the subsequent method for collecting the condensed-phase products, and the rationality of this method is further tested by the variation law of the condensed-phase products with pressure.

[0057] In one embodiment, the solid propellant 60 is a cylindrical grain with a diameter and height of 30 mm, and one end of it is adhered to the end face of the push rod 11 with a diameter of 30 mm. A dynamic seal is provided between the push rod 11 and the upper cover through two O-ring seals. Four optical windows are opened circumferentially along the combustion chamber 20 to facilitate the observation of the propellant burning surface position. At the same time, these optical windows can also be used for the propellant burning surface agglomeration photography test. The inner diameter of the sleeve 22 is 32 mm, and the material is stainless steel. Its inner wall is covered with a 2-mm-thick ethylene propylene diene monomer (EPDM) thermal insulation layer. This thermal insulation layer can reduce the heat loss during the propellant combustion process, making the combustion environment of the aluminum particles close to that of a real engine.

[0058] To fix the sleeve and facilitate the installation and disassembly before and after the test, a clamp seat 21 is added between the upper cover and the combustion chamber housing. The clamp seat can be connected to the sleeve through threads. In addition, by changing the length of the sleeve 22, solid propellant condensed phase products with different combustion distances can be obtained. The collection chamber 23 is filled with quenching liquid. There are pads at the bottom of the collection chamber 23 and the bottom of the combustion chamber 20. The height of the pads is changed to ensure the initial quenching distance between the quenching liquid level and the propellant burning surface.

[0059] The exhaust joint is connected to the throttle hole and the exhaust solenoid valve in sequence through pipelines. The intake joint is connected to the intake solenoid valve, the compressor, and the gas source in sequence through pipelines.

[0060] During the working process, under the action of the actuating device 10, the push rod 11 pushes the propellant to move uniformly downward in the sleeve 22, thus ensuring a constant quenching distance between the burning surface and the collection liquid level.

[0061] The actuating device can use a servo electric cylinder, which mainly consists of a servo motor, a planetary reducer, a lead screw, a reciprocating nut, and a guide rod. During the working process, the servo electric cylinder can convert the rotational motion of the motor into the linear motion of the guide rod and has the characteristics of precise speed, position, and thrust control. Based on the above advantages, the servo electric cylinder is adopted for the actuating device of the test system. The servo electric cylinder selects an AC servo motor (MSMF302L1H6M) produced by Panasonic Corporation of Japan. The input of this servo motor is three-phase alternating current with 124V and 18.1A, the rated power is 3KW, the rated speed is 3000r / min, and it can provide a constant torque of 9.55N·m during the working process. The lead of the lead screw is 4mm, and the reduction ratio of the planetary reducer is 5. The rated thrust and speed output by the servo electric cylinder are 37.5KN and 40mm / s respectively. The test device is designed according to the maximum working pressure of 15MPa. The upward thrust received by the push rod 11 under the maximum working pressure is 10.6KN. Due to the mechanical loss during the working process, the actual downward thrust output by the servo electric cylinder is about 85% of the rated thrust, that is, 31.9KN, and the safety factor of the actuating device is calculated to be 3. The diameter of the guide rod is 60mm, and the stroke is 150mm. During the working process, this actuating device can provide an actual thrust in the range of 0 - 31.9KN, a movement speed in the range of 0 - 40mm / s, and a movement stroke in the range of 0 - 150mm.

[0062] To facilitate the installation and disassembly of the test system, a bench structure is adopted to connect the actuating device 10 and the combustion chamber 20. The actuating device 10 is fixed on the upper bracket 30 by bolts, the combustion chamber 20 is connected to the backing plate of the guide rail / slider system on the lower bracket 50 by bolts, and the guide rod of the actuating device 10 is connected to the push rod of the combustion chamber by a flange. The slider / guide rail system consists of a guide rail, a slider, a motor, a lead screw, and a backing plate. During the installation and disassembly of the test system, the slider / guide rail system drives the combustion chamber housing to move horizontally along the upper support bench, while the actuating device drives the push rod and the upper cover to move vertically along the upper support bench. To improve the installation efficiency of the test device, a horizontal positioning device for the combustion chamber housing and a vertical positioning device for the upper cover are designed for the system.

[0063] When installing the test system, first install the collection chamber, the splint, and the sleeve inside the combustion chamber, and install the propellant on the push rod. Then manually control the slider / guide rail system to drive the combustion chamber housing to move into the support bench. When the horizontal positioning device gives an alarm, it means that the combustion chamber housing has moved horizontally to the appropriate position, and at this time, the slider / guide rail system is closed. Then manually control the actuating device to make the guide rod drive the upper cover to move slowly downward. During this process, pay attention that the bolt holes of the combustion chamber housing and the upper cover must be aligned. When the vertical positioning device gives an alarm during the movement, it means that the upper cover has moved vertically to the appropriate position, and at this time, the installation of the combustion chamber housing and the upper cover is completed.

[0064] The control system of the actuating device mainly consists of a servo driver, a programmable logic controller (PLC), a serial server, a DC power supply, a contactor, and a fuse. The servo motor of the actuating device adopts a speed control mode, and the control system principle is as shown in Figure 3 Figure 1. The tester inputs control commands (rod speed, working time, and delay time) through the upper computer. The upper computer transmits the control commands to the programmable logic controller (Xinjie Electric Co., Ltd., XDME-30T4) through the serial server (YouRen Internet of Things Co., Ltd., USR-TCP232-306). The programmable logic controller converts the control commands into control signals and transmits them to the servo driver (Panasonic Co., Ltd., MFDLNA3SG011). The servo driver converts the control signals into analog signals and transmits them to the servo motor to control the operation of the servo motor. The photoelectric encoder in the servo motor detects the speed of the motor rotor in real time and feeds the result back to the servo controller through the encoder. The servo driver compares the feedback value with the target value, adjusts the rotation speed of the rotor, forms a closed loop, and thus realizes the precise control of the servo motor. The DC power supply (Mean Well Co., Ltd., EDR-150-24) is used to provide 24V DC power to the programmable logic controller and the servo controller. The contactor (Delixi Co., Ltd., F4-31) is used to control the shutdown and operation states of the motor. The fuse (CHNT Co., Ltd., RT28N-32X) is used for the circuit protection of the control system to prevent overcurrent and short-circuit phenomena.

[0065] The pressure regulation system mainly consists of a pressure sensor, a constant pressure controller, a throttle orifice, pipelines, and a solenoid valve. During the test process, in order to ensure the stable pressure in the combustion chamber, a closed-loop control method is adopted to regulate the pressure inside the combustion chamber. The pressure sensor measures the pressure in the combustion chamber and transmits the signal to the constant pressure controller. The chip on the constant pressure controller compares the transmitted voltage signal with the preset value. When the pressure in the combustion chamber is greater than the preset value, the relay on the constant pressure controller controls the solenoid valve to open, and the combustion chamber exhausts gas, and the pressure drops. When the pressure in the combustion chamber is less than the preset value, the relay controls the solenoid valve to close, the combustion chamber stops exhausting gas, and the pressure rises.

[0066] In order to reduce the interference of external clutter on the pressure signal, a current-type pressure sensor is adopted, and after converting the output current signal into a voltage signal, it is input into the constant pressure controller. There is a mechanical delay during the opening and closing process of the solenoid valve, which will cause the pressure in the combustion chamber to fluctuate too much near the preset value. Therefore, a throttle orifice is installed at the inlet of the exhaust solenoid valve, and the aperture of the throttle orifice is calculated according to the following formula:

[0067]

[0068] where ρ p is the propellant density, r is the propellant burning rate, ρ gThe density of the gas generated by the propellant combustion is obtained from the thermodynamic calculation of the propellant, C d is the orifice flow coefficient, which is calculated as C in this embodiment d = 0.675. ΔP is the pressure difference inside and outside the combustion chamber, D p is the propellant diameter, ρ m is the density of the discharged medium, which is approximately taken as ρ during the calculation in this embodiment m = ρ g .

[0069] During the test process, the combustion chamber pressure and the exhaust solenoid valve signal were measured, and the results are as Figure 4 shown. Before the test, nitrogen gas at about 6 MPa was filled into the combustion chamber to establish the initial pressure. After the start of the propellant combustion process, the pressure curve rose rapidly. When it reached 7 MPa, the exhaust solenoid valve opened automatically for the first time, as shown at the t1 moment in the figure. The entire combustion process lasted for 4.8 s, during which the exhaust solenoid valve underwent 7 automatic opening and closing processes. At the initial stage of the propellant combustion, there was a small pressure peak in the combustion chamber, with a value of 7.3 MPa, and the final pressure balanced at about 7.1 MPa. After the propellant combustion ended, the combustion chamber pressure rapidly dropped to less than 7 MPa. At this time, the exhaust solenoid valve automatically closed, and the combustion chamber stopped exhausting, as shown at the t2 moment in the figure. Under the action of the heat dissipation of the gas to the outside and the condensation of water vapor, the combustion chamber pressure slowly dropped and finally stabilized at about 5 MPa. At this pressure, wait for 30 min to allow the condensed phase particles in the combustion chamber to fully precipitate, and then manually open the exhaust solenoid valve to relieve the pressure

[0070] The present invention also discloses a method for precisely collecting solid propellant condensed phase particles, using the above-mentioned device for precisely collecting solid propellant condensed phase particles, which specifically includes the following steps: determining the starting time of the actuating device 10 according to the ignition time of the solid propellant 60. By designing the ignition time and the time of the actuating device 10, the distance accuracy between the burning surface of the solid propellant 60 and the quenching liquid surface can be guaranteed, so that this distance can be stably maintained within a predetermined range value or a predetermined range, thereby providing more real condensed phase products for subsequent analysis

[0071] The asynchronous start of the propellant combustion and the actuating device will cause the quenching distance to be unable to be maintained constant during the test process. To solve the above problems, the ignition delay time of the propellant and the response time of the servo motor need to be considered during the system control process. The ignition delay time of the propellant depends on the ignition method. The test uses a YT ignition head produced by Chongqing Yukong Aerospace Technology Company to ignite the propellant. This ignition head is mainly composed of a thermosensitive drug and a thermal resistance wire, with a drug head diameter of 3.5 mm. Inputting 24V DC voltage can generate high-temperature gas with an instantaneous temperature of about 1200 °C, as Figure 5 shown Figure 5The measured combustion chamber pressure and the output signal of the ignition power supply during the test process are given. The ignition trigger time is t i . When the ignition power supply is turned on, a voltage of 24 V is output. The pressure in the combustion chamber at the end of the ignition process, that is, the ignition cut-off pressure Pc in the figure, is calculated by the following formula:

[0072] P c = 0.1P e + 0.9P i

[0073] where P i is the combustion chamber pressure corresponding to the ignition trigger time, and P e is the equilibrium pressure inside the combustion chamber.

[0074] The abscissa corresponding to the ignition cut-off pressure Pc is the ignition cut-off time t c . Define the time interval between the ignition trigger time t i and the ignition cut-off time t e as the ignition delay time T i , that is:

[0075] T i = t c - t i ,

[0076] Before collecting the test, first measure the ignition delay time of the propellant, and conduct three repeated tests for each propellant. As Figure 6 shown, take the arithmetic mean of the measurement results as the ignition delay time of the propellant. Figure 6 The repeated measurement results of the ignition delay time of the propellant used are 596 ms, 532 ms, and 572 ms respectively. During the collection process of the condensed phase products, the average value of 567 ms is taken as the ignition delay time of this propellant. The response time of the servo motor is the time required for the servo motor to move from the stationary state to the rated speed. According to the product technical parameters, the response time of the Panasonic servo motor is about 20 ms. It can be seen that the response time of the servo motor is much less than the ignition delay time of the propellant, so it is ignored during system control.

[0077] During the test process, the control timing sequence of the system is as Figure 7 shown. At time 0, press the power switch, the propellant starts to ignite, and at the same time the control system starts timing. At time T i , the actuator control module in the control system controls the actuator to start. As the combustion chamber pressure increases, the constant pressure control module in the control system controls the first opening time of the exhaust solenoid valve. At time T c , the constant pressure control module controls the exhaust solenoid valve to close, and at this time the propellant combustion ends. After 30 minutes, manually open the exhaust solenoid valve to open it again for pressure relief. At time T iis the ignition delay time of the propellant and is input into the control system in advance as a control parameter. T c is the combustion time of the propellant, which is calculated by the system based on the input propellant burning rate and the grain height.

[0078] The control actions at the start and end of the test are completed manually. The opening and closing of the actuator are controlled by the actuator control module according to the system parameters, while the opening and closing of the exhaust solenoid valve are automatically completed by the constant pressure control module according to the monitored combustion chamber system status. To improve the integration of the control system, the control timing, including the constant pressure control module, manual control, and the upper computer of the actuator control module, is integrated in a control box.

[0079] The schematic diagram of the test method for collecting condensed phase products of solid propellant with a constant quenching distance is as Figure 8 shown, and the test procedure is as follows:

[0080] 1) Assemble the combustion chamber. Place the collection chamber filled with quenching medium inside the combustion chamber. At the same time, attach the propellant to the end face of the push rod. The guide rail slider system and the servo electric cylinder drive the combustion chamber and the upper cover to fixed positions respectively, and then connect the upper cover and the combustion chamber with bolts.

[0081] 2) Open the vacuum pump to evacuate the combustion chamber. After exhausting the internal air, manually close the stop valve.

[0082] 3) Open the compressor and the inflation solenoid valve in sequence to fill the combustion chamber with nitrogen at about 6 MPa.

[0083] 4) Determine the initial position of the propellant in the vertical direction inside the sleeve according to the sleeve length and the required quenching distance of the test. Then switch the servo motor controller to the touch screen control mode and manually control the servo electric cylinder to push the grain to the corresponding position.

[0084] 5) Set the start delay time, movement speed, and movement distance of the servo electric cylinder, and then connect the ignition wire.

[0085] 6) Press the start button on the control box to start the test system. At this time, the propellant starts to burn, and the servo electric cylinder starts to push the propellant to move downward at a constant speed. The control board controls the exhaust solenoid valve to exhaust according to the combustion chamber pressure signal monitored by the pressure sensor.

[0086] 7) After the propellant combustion ends, wait for 30 min. When the condensed phase particles in the combustion chamber are fully settled, manually open the exhaust solenoid valve to relieve the pressure.

[0087] 8) Take out the collection chamber, and perform cleaning, precipitation, centrifugation, and drying treatments on the collected liquid in sequence to obtain the condensed phase products of the propellant, and then conduct subsequent physical and chemical analyses on them.

[0088] It should be noted that the propellants used in the experiments of the present invention are all cylindrical grains with a diameter and height of 30 mm. In order to ensure end combustion, the sides of the propellants are coated multiple times. The coating agent is prepared from polyvinyl butyral (PVB) and ethanol (C2H6O) in a mass ratio of 15:85. Since ethanol has a good cooling effect and does not react with aluminum particles, ethanol is used as the quenching medium in the experiments.

[0089] In one embodiment, the propellant is cut into cylindrical grains with a diameter of 20 mm and a length of 25 mm by an annular knife die, and the mass of each is about 15 g. Polyvinyl butyral flame retardant is applied to the side of the propellant grain. After each application, wait for 1 - 2 h to cure and then apply again. Repeating more than 5 times gives a better flame retardant effect, enabling the propellant to maintain end combustion. It is fixed on a stainless - steel pill - loading piece with threads using a two - component epoxy resin adhesive. After attaching the igniter head, the mounting piece is finally thread - mounted on the push rod connected to the vertical actuation motor. After installing the pill - loading piece, seal the combustor, set the quenching distance, the moving speed of the vertical actuation motor, and the time series for collection. Zero the vertical actuation motor and the timing control system according to the set burning rate and distance. Open the intake valve, fill nitrogen through the compressor to a stable working pressure, then close the intake valve. After the pressure stabilizes, press the ignition button to ignite the igniter head, and at the same time trigger the timing control system and the vertical actuation motor. After the propellant burns out and stands for 30 minutes, take out the suspension mixed with CCPs in the quenching box in the combustor. Pour the suspension into a beaker, filter it through a vacuum pump and a filtering flask to obtain the condensed - phase particles, and then put them into an oven to dry to obtain the finally dried CCPs. The above experimental steps are repeated three times for each working condition.

[0090] Table 1

[0091]

[0092] The test parameters are shown in Table 2 above.

[0093] In a real combustor, the temperature is usually higher than 3000K. The high - temperature environment can ensure the full reaction of Al particles. When the collection experiment of the propellant is carried out, the CCPs quickly enter the surrounding nitrogen cold - flow environment after leaving the combustion surface, which is different from the situation in the actual engine combustor. The heat loss is large, resulting in low combustion efficiency. Therefore, adding an adiabatic graphite sleeve around the propellant can provide a high - fidelity high - temperature environment for the propellant combustion.

[0094] To verify the effect of the adiabatic graphite sleeve, the condensed-phase combustion products of propellants P0 and P1 without and with the graphite sleeve were collected at a quenching distance of 65 mm, and the combustion process of the particles was completely carried out inside the graphite sleeve. The SEM images and particle size distributions of the CCPs collected from the combustion of P0 and P1 are as Figure 9 shown.

[0095] In the SEM images of the CCPs collected without the sleeve, many large particles with sizes exceeding 100 μm can be seen ( Figure 9 (a1, a2) in Figure 9 ), and significantly smaller and more uniform particle sizes can be found in the SEM images of the CCPs collected after adding the sleeve ( Figure 9 (b1, b2) in

[0096] Table 2

[0097]

[0098] Figure 10 shows the SEM images, combustion efficiency, and particle size distribution of the CCPs at different quenching distances, as well as different collection regions of the low burning rate propellant. It can be seen from the SEM images ( Figure 10 (a1)-(a4) in Figure 10 ) that the CCPs in the central region are more likely to produce particles with sizes larger than 100 μm, and the particle surfaces are rougher, but the CCPs in the outer region have smaller particle sizes. Therefore, the present invention proposes that the spatial distribution and particle size distribution of the propellant CCPs are as

[0099] shown in Figure 11 (a5), where the SEM image is from sample LP45. Due to the difference in particle fluidity, small-sized aggregates and alumina soot (SOPs) are more likely to diffuse to the outer region, while large-sized aggregates are more likely to concentrate in the central region, which also increases the content of unburned aluminum in the central region to a certain extent.

[0099] From Figure 11 it can be observed that the average particle size in the central region is about 150 μm, and the average particle size in the outer region is close to 50 μm, because 50-μm particles are more susceptible to the influence of the gas-phase flow field than 150-μm particles.

[0100] Meanwhile, Figure 11It is shown that the particle size distribution is multimodal. The particle size distribution of CCPs has three modes: 1 - 3 μm, 10 - 30 μm, and 100 - 300 μm. In this embodiment, the three - peak particle size distribution suggests that the 1 - 3 μm particles are smoke oxide particles formed by the oxidation of aluminum vapor. The 10 - 30 μm particles are considered to be oxide particles generated by the combustion of 29 μm Al powder in the propellant. The 100 - 300 μm particles are large agglomerates produced by the collision of molten aluminum droplets during combustion. There are more smoke oxide particles in the outer region of CCPs and more large agglomerates in the central region, thus resulting in the particle size in the central region being much larger than that in the outer region. In addition, Figure 11 It is also shown that at all three quenching distances, the combustion efficiency of CCPs in the outer region is higher than that in the central region, which further verifies that the content of unburned Al in the large agglomerates in the central region is higher.

[0101] According to Figure 10 and Figure 11 findings, the quenching distance has no significant effect on the particle size of CCPs in the central region, but the size of CCPs in the outer region gradually increases with the increase of the quenching distance, probably because a longer quenching distance will cause more large agglomerates to enter the outer region. Figure 12 It is shown that the combustion efficiency of CCPs in the central region is positively correlated with the quenching distance. At a quenching distance of 5 mm, the combustion efficiency of CCPs in the central region is only 85.39%, which is 7.2% lower than that of CCPs in the outer region (92.07%). When the quenching distance is 45 mm, the difference in the combustion efficiency between CCPs in the central region and the outer region is 3.5%, and when the quenching distance is 180 mm, it is only 1.7%. However, the quenching distance has little effect on the combustion efficiency of CCPs in the outer region, and the average value of the combustion efficiency at the three quenching distances is 92.47%. It can be seen that under solid - propellant conditions, the combustion law of Al agglomerate droplets is composed of the D 2 law and can be simplified as follows:

[0102]

[0103] where D is the particle diameter and t is the combustion time.

[0104] In addition, through calculation, the velocity of 100-μm agglomerates is less than 1.5 m / s, and the combustion distance of 600-μm agglomerate particles is less than 45 mm. Therefore, it can be seen that at quenching distances of 5 mm and 45 mm, the difference in the unburned Al content in the central region CCPs is 5%, while the difference between quenching distances of 45 mm and 180 mm is only 1.5%. In summary, the influence of the quenching distance on the combustion efficiency gradually decreases as the quenching distance increases. When the quenching distance reaches 180 mm, it approaches the condition of complete combustion of the propellant. Beyond a quenching distance of 180 mm, the effect is very weak. Therefore, it can be considered that the difference in combustion efficiency caused by the quenching distance mainly comes from the CCPs in the central region, that is, large-sized agglomerates.

[0105] Generally, the combustion of solid propellants has three stages: the initial ignition stage, the steady working stage, and the trailing section. The total impulse of the engine is mainly provided by the middle section, i.e., the steady working section, accounting for more than 70% of the total impulse. By setting the collected time series, the CCPs in the hot or cold central region can be accurately collected. According to the CFD calculation in the previous text, under the propellant combustion conditions, the average temperature of the 180-mm graphite sleeve approaches the adiabatic combustion temperature after 1.2 s, which is the change from the cold state to the hot state.

[0106] The baffle in the central collection area is opened at t = 0 and closed at t = 1.2 s, corresponding to collecting the CCPs in the cold central region during the combustion time of t = 0 - 1.2 s, denoted as LP180-C. The baffle in the central region is closed at t = 0, opened at t = 1.2 s, and closed at t = 2.4 s, corresponding to collecting the CCPs in the hot central region during the combustion time of t = 1.2 - 2.4 s, denoted as LP180-L. Figure 13 Figures (a) and (b) are SEM images of the CCPs collected in the central regions of samples LP180-C and LP180-T. Both of these samples have spherical large agglomerates with sizes larger than 150 μm and other large-sized agglomerates with irregular shapes. Figure 14 Shows the combustion efficiency of the CCPs under cold-state collection and hot-state collection with a quenching distance of 180 mm. It can be seen from the figure that the combustion efficiency of the CCPs in the central region of LP180-C is 90.85%, while the combustion efficiency of the CCPs in the central region of LP180-T reaches 93.60%. The hot state is 2.75% higher than the cold state, and even higher than the combustion efficiency (92.44%) of the CCPs collected in the outer region at this quenching distance.

[0107] Figure 14 and Figure 15Shows the particle size distribution of CCPs under two different collection time series. It can be seen from the figure that the average particle sizes (D43 = 184.5 μm and 195.3 μm) of CCPs in the central regions of samples LP180-C and LP180-T are larger than the average particle sizes (D43 = 667.5 μm, 108.0 μm) of the corresponding CCPs in the outer regions. This indicates that the collection time series has less influence on the particle size of CCPs in the central region, and the CCPs collected under the condition of more complete combustion with a combustion time of t = 1.2 s - 2.4 s still exhibit a larger particle size distribution than that in the outer region. Therefore, the collection time is a very important issue when collecting propellant CCPs in the future, especially under laboratory conditions, where propellants with a smaller mass require a longer quenching distance and a longer time when the collection environment changes from cold to hot.

[0108] There are certain differences in the condensed-phase combustion products of the propellant in the cold and hot states in the sleeve. Therefore, it is considered that the influence of heat loss cannot be ignored, and the influence of heat loss in the collection method should be further analyzed. In all experiments, N0 propellant was used, and it was cut into cylindrical grains with diameters of 20 mm, 15 mm, 10 mm, 5 mm and a height of 25 mm using a mold. The condensed-phase combustion products with a quenching distance of 180 mm were collected under the condition of being equipped with a graphite sleeve. Figure 16 SEM images of CCPs collected for propellants with four burning surfaces at a quenching distance of 180 mm. From the overall size of the particles, it can be seen that with the decrease of the burning surface, large-size agglomerates are more likely to appear. From Figure 17 The particle size distribution in also shows this point. With the decrease of the burning surface, both the peak size and mass content of large-size agglomerates increase significantly, and the micron-sized alumina soot decreases significantly. The three particle size aggregation peaks all shift to the right with the decrease of the propellant burning surface size, that is, the sizes of alumina soot, small-size agglomerates and large-size agglomerates all increase.

[0109] The experimental results of the combustion efficiency test also show a conclusion consistent with the particle size distribution, such as Figure 18As shown, as the burning surface diameter of the propellant gradually increases, the combustion efficiency increases from 75.67% (±0.88%) to 96.84% (±0.16%). However, this law is not linear. It can be seen that as the burning surface gradually increases, the improvement effect of the combustion efficiency gradually weakens. When the burning surface diameter increases from 5 mm to 10 mm, the combustion efficiency increases by 11.67%. However, when the burning surface diameter increases from 15 mm to 20 mm, the combustion efficiency only increases by 2.12%. This shows that under the experimental conditions, after the burning surface of the propellant reaches 15 mm, the influence of the burning surface on the combustion efficiency of the propellant decreases. It also shows that the CCPs collected from the propellant columns with a diameter of 15 mm and above in this device are closer to the combustion environment of the real engine and have less heat loss. At the same time, it can be seen that as the burning surface diameter of the propellant increases, the deviation of multiple combustion efficiency tests also decreases, and the results have better repeatability.

[0110] Use Fluent to simulate the flow of the propellant gas in the sleeve. Assuming that the incident gas flow is 3000 K, the ambient pressure is 7 MPa, and the mass flow rate is the mass flow rate calculated from the real experiment, the transient calculation is carried out to obtain the temperature distribution map in the sleeve at 1 s as shown in Figure 19 As shown. It can be found from the figure that when the propellant with a diameter of 20 mm burns for 1 s, the average temperature in the sleeve reaches above 2500 K, and there is almost no cold flow state. When the propellant with a diameter of 15 mm burns for 1 s, the central area in the sleeve exceeds 2500 K, with a length of about 10 cm. However, the temperature in other areas is between 1500 K and 2000 K, and the temperature has dropped to about 1000 K when it reaches the sleeve outlet. In contrast, when the propellants with burning surface diameters of 10 mm and 5 mm burn for 1 s, the temperature increase in the sleeve is very small. The propellant with a diameter of 10 mm can only make the temperature in the sleeve reach below 1000 K, and only the area close to the axis (<2 mm) is in a high-temperature environment, with a length of no more than 5 cm. The combustion of the propellant with a diameter of 5 mm for 1 s has almost no influence on the temperature distribution in the sleeve, and only a very small area near the burning surface has a high temperature. This also verifies that the heat loss is small when the burning surface diameter of the propellant is above 15 mm in the experiment, and the combustion of aluminum particles is more complete.

[0111] At the same time, XRD analysis was also carried out on the sample with a burning surface of 15 mm as shown in Figure 20As shown, it is found that it not only contains Al and Al2O3, but also a certain content of AlN, which can be produced by the high-temperature combustion of Al in a nitrogen environment. For this micron, an oxygen-nitrogen-hydrogen analyzer was used to test the nitrogen content of the sample, and it was found that it contained 3.05% mass content of N element, and the mass content of AlN was calculated to be 11.11%. The active aluminum content obtained by chemical titration was 5.28%, indicating that only 83.61% of it was Al2O3. By comparing the formation enthalpies of AlN and Al2O3, it was found that the formation enthalpy of AlN was 6.235 kJ / g, and the production enthalpy of Al2O3 was 16.428 kJ / g. Calculating according to all reactions being Al2O3 as the total energy release, the current energy release rate was only 87.83%.

[0112] Based on the research on the influence of the above collection methods on the condensed-phase combustion products, the present invention summarizes a more comprehensive and scientific fine collection method and processing and analysis process for condensed-phase combustion products. The collection method mainly includes the setting of ignition delay time, combustion rate, working pressure, sleeve length, and collection time series. First, the ignition delay time of the propellant is obtained by a high-speed camera, and the delay time of synchronous triggering is set. The combustion rate of the propellant under the working pressure is measured to set the moving speed of the vertical push rod to ensure that the distance between the burning surface and the cooling liquid surface is constant. The residence time of particles in the rocket engine combustion chamber is obtained through two-phase flow calculation, and the length of the adiabatic graphite coating is determined. The working stage of the propellant is determined, and the time when the graphite sleeve reaches the thermal state is calculated by CFD to set the collection time series. The experiment uses a cylindrical propellant grain with a diameter of more than 15 mm, and the condensed-phase combustion products are collected through a high-temperature and constant quenching distance and constant pressure collection system. The alcohol suspension containing the condensed-phase combustion products is collected, and the dry condensed-phase product particles are obtained through ultrasonic dispersion, vacuum filtration through a filter membrane, and freeze-drying (or drying). The particles are characterized by various means such as sieving, particle size analysis, chemical titration, and scanning electron microscopy.

[0113] In summary, in the collection method of the present invention, the graphite sleeve, quenching distance, collection area, collection time sequence, propellant burning surface, and sieving all have an impact on the particle size and combustion efficiency of the condensed-phase combustion products.

[0114] The addition of the adiabatic graphite sleeve can effectively reduce the average particle size of CCPs and the content of unburned Al. Compared with the case without a graphite sleeve, its combustion efficiency is increased by 2.44%. At the same time, it is found that the particle size distribution and combustion efficiency of the CCPs collected in the central area are usually lower than those in the outer area, which is related to the differences in fluidity and combustion efficiency caused by particle size.

[0115] The increase in the quenching distance significantly improves the combustion efficiency of CCPs in the core region of low-burning-rate propellants, but this is only limited to the near-burning surface and the mid-distance burning surface. When far from the burning surface, the particles have basically burned out completely, and the ambient temperature is relatively low, resulting in the termination of combustion. The collection timing has a significant impact on the characteristics of CCPs. The combustion efficiency of CCPs in the hot state (t = 1.2 - 2.4 s) is 2.75% higher than that in the cold state (t = 0 - 1.2 s).

[0116] In this device, the burning surface of the propellant has an impact on both the particle size distribution and the combustion efficiency of CCPs. When the burning surface diameter of the propellant is less than 15 mm, the heat loss in the burner is relatively large. Particle agglomeration is obvious and it is difficult to burn completely. When the burning surface diameter of the propellant is greater than 15 mm, the propellant is less affected by heat loss and burns basically completely.

[0117] Therefore, the present invention provides a more comprehensive and scientific method for the fine collection of condensed-phase combustion products and a processing and analysis process. By combining various experimental means and simulation means, including the setting methods of ignition delay time, combustion rate, working pressure, sleeve length, and collection time series, the collection method becomes more refined, and the working conditions corresponding to the condensed-phase combustion products are closer to those of a real engine.

Claims

1. An accurate collection device for solid propellant condensed-phase particles, characterized in that, It includes a combustion chamber (20), the combustion chamber (20) being a hollow cylinder with an upper cover at the top of the hollow cylinder; The upper cover is connected with an actuating device (10), and a push rod (11) of the actuating device (10) is movably and sealingly connected with the upper cover; The bottom end of the push rod (11) is used for installing a solid propellant (60); A sleeve (22) is arranged around the solid propellant (60); A collection chamber (23) is arranged at the bottom of the combustion chamber (20), and there is quenching liquid in the collection chamber (23).

2. The precise collection device for solid propellant condensed phase particles according to claim 1, characterized in that, The inner wall surface of the sleeve (22) has the same shape as the outer peripheral surface of the solid propellant (60).

3. The precise collection device for solid propellant condensed-phase particles according to claim 2, characterized in that, The sleeve (22) is installed in the combustion chamber (20) through a clamping seat (21).

4. The precise collection device for solid propellant condensed-phase particles according to claim 3, characterized in that, The inner circumference of the clamping seat (21) is fixedly connected with the outer wall of the sleeve (23), and the outer ring of the clamping seat (21) is fixedly installed between the upper cover and the combustion chamber (20).

5. A precise collection device for solid propellant condensed-phase particles according to any one of claims 2-4, characterized in that, The collection chamber (23) is a shell with an open top; There is a tube body with both ends open in the shell, and the bottom end of the tube body is fixedly connected with the inner bottom surface of the collection chamber (23); The cross section of the tube body is the same as the cross section shape of the solid propellant (60).

6. The precise collection device for solid propellant condensed phase particles according to claim 5, characterized in that, The height of the tube body is the same as the height of the collection chamber (23).

7. The precise collection device for solid propellant condensed-phase particles according to claim 6, wherein, The top of the tube body has a movable baffle plate.

8. The precise collection device for solid propellant condensed phase particles according to claim 7, characterized in that, The actuating device (10) is installed on an upper bracket (30); wherein, the actuating device (10) can drive the upper cover to move up and down through its push rod (11).

9. A method for precisely collecting condensed-phase particles of a solid propellant according to claim 8, characterized in that, The combustion chamber (20) is installed on a laterally arranged guide rail (40); wherein, the guide rail (40) is used for driving the combustion chamber (20) to move laterally.

10. A method for precisely collecting condensed-phase particles of a solid propellant, characterized in that, Using a precise collection device for solid propellant condensed phase particles according to any one of claims 1-9, specifically including the following steps: Determine the starting time of the actuating device according to the ignition time of the solid propellant (60).

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