Experimental engine with simultaneous measurement of transient burning rate and collection of condensed phase products under overloading

Abstract

The experimental engine disclosed by the application can measure the transient burning rate and collect condensed phase products under overload, and belongs to the field of solid rocket engine overload experiment. The application simulates the engine overload environment through a rotating overload platform cantilever; and collects the condensed phase products staying on the solid propellant combustion surface through a collecting device B. The condensed phase products are collected through a collecting device A by using the inertia difference between the gas and the condensed phase products. The high-precision and high-efficiency measurement of the transient burning rate is realized by establishing a solid propellant transient burning rate calculation model. The condensed phase products flowing with the gas are collected by the collecting device A, and then the two-phase flow law in the combustion chamber under the action of the overload force and the morphology, particle size and composition of the condensed phase products are analyzed. The structure layout of the jet device and the combustion chamber shell is perpendicular, the overload experiment is carried out at an arbitrary angle θ between the overload direction and the combustion surface retreat direction, and the engine experiment under different overloads is carried out by changing the rotating speed of the overload platform cantilever.

Description

Technical Field

[0001] This invention relates to an experimental engine that can measure transient burning rate and collect condensation products under overload conditions, belonging to the field of solid rocket engine overload experiments. Background Technology

[0002] Solid rocket engines inevitably experience overload conditions during operation, such as during takeoff acceleration and high-maneuverability maneuvers, especially in advanced missile propulsion systems. To increase energy, most propellants incorporate readily available and inexpensive aluminum powder, which increases the propellant's acceleration sensitivity. When there is acceleration or acceleration component in the same direction as the burner surface retreat, some condensed products generated during combustion will remain on the burner surface under the combined action of acceleration and aerodynamic forces, forming a "thermal short circuit" between the flame and the burner surface. This alters the propellant's transient burning rate, leading to increased combustion chamber pressure, shortened combustion time, and changes in internal ballistic performance and thrust. It can even pose a threat to missile flight safety. When there is acceleration or acceleration component in the opposite direction to the burner surface retreat, condensed products generated during combustion will leave the burner surface under the action of overload and aerodynamic forces. This affects the solid rocket engine's specific impulse, ablation of the insulation layer and nozzle, combustion stability, slag deposition, and energy release.

[0003] Therefore, it is necessary to conduct overload solid rocket engine ignition experiments to provide guidance for solid rocket engine design.

[0004] Using a passive test stand, the overload test engine is fixed on the cantilever of the overload test stand. A variable-speed motor and actuation mechanism drive the cantilever to rotate, simulating the overload environment during missile flight. This ground-based overload simulation significantly reduces experimental costs. By simulating acceleration or acceleration components in the same direction as the burner surface retreat, condensed phase products remaining on the burner surface and those carried away by the exhaust gas are collected. The transient burning rate of the propellant is measured, and the relationship between the condensed phase products remaining on the burner surface and the transient burning rate of the propellant, as well as the relationship between the particle size of the condensed phase products carried away by the exhaust gas and the theoretical "critical diameter," are analyzed. Similarly, by simulating acceleration or acceleration components in the opposite direction to the burner surface retreat, condensed phase products carried away by the exhaust gas are collected, and their morphology, composition, and particle size are obtained. This has significant theoretical and engineering application value for improving the processing technology of solid propellants and enhancing the performance of solid rocket motors.

[0005] To do a good job, one must first have the right tools. However, existing overload experimental engines, such as the one described in the paper "Research Progress on Combustion Chamber Particle Characteristics and Insulation Layer Ablation under Overload," present a particle collection experimental device that uses convergence to aggregate particles, and for the first time experimentally tested the collection and analysis of particles in a simulated engine combustion chamber under overload. However, its large and cumbersome size, along with the collection liquid in the collection tank, limits its experimental use on an overload platform. The collected condensed phase products are not subjected to real overload forces, remaining in the simulation stage, and can only collect condensed phase particles within the combustion chamber (i.e., condensed phase particles carried away by the combustion gas). It cannot collect condensed phase products that remain on the propellant combustion surface due to real overload. Furthermore, it lacks the function of measuring the transient burning rate of the propellant. Summary of the Invention

[0006] To provide a more realistic evaluation of the performance of solid rocket motors under overload, the main objective of this invention is to provide an experimental engine capable of measuring transient burning rates and collecting condensed phase products under overload conditions. This experimental engine is placed on the cantilever of an overload platform, and the overload environment of the engine is simulated by rotating the cantilever. The following experimental functions are achieved: (i) When the overload force on the condensed phase products generated by the combustion of the solid propellant is greater than the aerodynamic force on the condensed phase products, the condensed phase products remaining on the solid propellant burning surface are collected by collection device B. (ii) Collection device A is positioned directly opposite the solid propellant burning surface, along the engine axis, with the jetting device perpendicular to the combustion chamber shell. The propellant burning surface generates axial gas and condensed phase products. Utilizing the difference in inertia between the gas and the condensed phase products, the gas is discharged through the jetting device, while the condensed phase products, due to inertia, enter the collection device A, thus collecting the condensed phase products. (III) By analyzing combustion chamber pressure, propellant performance, and engine parameters, a transient burning rate calculation model for solid propellants is established. This model enables high-precision and efficient measurement of transient burning rate, facilitating the analysis of the propellant's transient characteristics. (IV) Collection device A is divided into four areas, allowing for the separate collection of condensed phase products carried away by the combustion gas flow. This enables the analysis of the two-phase flow pattern within the combustion chamber under overload conditions and the morphology, particle size, and composition of the condensed phase products. (V) The design employs a vertical layout between the jet device and the combustion chamber shell, with identical end caps on both sides of the engine. This allows for overload experiments with an arbitrary angle θ (0≤θ≤π) between the overload direction and the combustion surface retreat direction. By changing the angular velocity of the overload platform cantilever, engine experiments under different overload magnitudes can be conducted. In other words, this invention can measure the transient burning rate of the propellant and collect condensed phase products under arbitrary angle θ (0≤θ≤π) between the overload direction and the combustion surface retreat direction and under different overload magnitudes. This invention contributes to improving the processing technology of solid propellants and enhancing the performance of solid rocket motors.

[0007] The objective of this invention is achieved through the following technical solution.

[0008] The present invention discloses an experimental engine capable of measuring transient combustion rate and collecting condensation products under overload conditions, comprising an experimental engine capable of measuring transient combustion rate and collecting condensation products, a fixed fixture, and an overload stage. The experimental engine capable of measuring transient combustion rate and collecting condensation products is fixed on the cantilever of the overload stage by the fixed fixture, and the overload stage cantilever is rotated to simulate the engine overload environment.

[0009] The experimental engine, which combines the functions of measuring transient combustion rate and collecting condensed products, includes an end cap, combustion chamber shell, outer gasket, plug, bottom cover of collection device B, O-ring seal, PTFE gasket, inner gasket, collection device B box, solid propellant, insulation sleeve, ignition charge, cover of collection device A, collection device A box, igniter base, igniter seal, pressure sensor base, pressure relief valve base, rupture plug, pressure relief valve end cap, nozzle base, nozzle end cap, nozzle bushing, nozzle throat sleeve, and nozzle.

[0010] The solid propellant has a coating layer and is pre-cast into the collection device B box. The experimental engine is placed on an overload platform cantilever, and by rotating the overload platform cantilever, the overload environment during missile flight is simulated. That is, when the overload force on the condensed phase products generated by the combustion of the solid propellant is greater than the aerodynamic force on the condensed phase products in the same direction as the burner surface retreat, the condensed phase products will remain on the burner surface and be directly collected by the collection device B.

[0011] The combustion chamber shell is a hollow cylinder; collection device B and collection device A are located at the left and right ends of the shell respectively, facing each other; the jet device is perpendicular to the combustion chamber shell; the gas generated by the propellant combustion surface and the condensed phase products flowing with the gas will move along the engine axis. When they reach the inlet of the jet device, due to the difference in inertia between the gas and the condensed phase products, the gas is discharged through the jet device, and the condensed phase products will continue to move along the axis and enter the collection device.

[0012] Preferably, the initial distance between the propellant combustion surface and the collection device A is only 100mm, and the distance between the central axis of the jet device and the collection device A is only 30mm, which is conducive to the entry of condensed products into the collection device A.

[0013] The sensor base is used to install a high-frequency (acquisition frequency greater than 150kHz) pressure sensor to measure the pressure inside the burner. By analyzing the combustion chamber pressure, propellant performance, and engine parameters, a transient burning rate calculation model for solid propellants is established. The transient burning rate calculation model for solid propellants is used to achieve high-precision and efficient measurement of transient burning rate, thereby facilitating the analysis of the transient characteristics of the propellant.

[0014] The collection device A includes four areas: collection area 1 is the inner liner, collection area 2 is along the direction of gravitational acceleration, collection area 3 is along the direction of Coriolis acceleration, and there is also a collection area 4; then, the effects of gravity and Coriolis acceleration on the two-phase flow law and the morphology, particle size and composition of condensed products in the combustion chamber under overload are analyzed.

[0015] Unlike traditional engines where the jetting device is arranged axially along the engine casing, this experimental engine employs a vertical arrangement between the jetting device and the combustion chamber casing. Even when the angle θ between the overload direction and the combustion surface retreat direction is ≥90°, the high-temperature exhaust gas ejected by the jetting device will not damage the mounting device and the overload platform. This allows for overload experiments with any angle θ (0≤θ≤π) between the overload direction and the combustion surface retreat direction. Furthermore, the identical end caps on both sides of the engine facilitate interchangeability on the overload platform. By changing the angular velocity ω of the overload platform cantilever, different overload environments can be simulated. Therefore, this invention can measure the transient burning rate of the propellant and collect condensation products under any angle θ (0≤θ≤π) between the overload direction and the combustion surface retreat direction and under different overload conditions.

[0016] This invention allows the engine to be placed symmetrically along both cantilever arms, enabling experiments to be conducted under two different operating conditions at once, significantly reducing experimental costs.

[0017] The inner diameter of the solid collection device A is larger than the inner diameter of the middle part of the combustion chamber shell, which is beneficial for the collection of condensed products; the outer diameter of the solid collection device A is smaller than the inner diameter of the right side part of the combustion chamber shell, which is beneficial for removing the collection device A.

[0018] Preferably, when the overload direction forms an angle θ = 0° with the combustion surface retreat direction, the collection method of the collection device B is as follows.

[0019] The experimental engine is clamped on the cantilever of the overload test platform and rotates counterclockwise with the cantilever at a constant angular velocity ω. e The speed is v e The vector distance from the condensed product to the center of the moving overload stage is r, and the relative velocity between the condensed product and the experimental engine is v. g The condensed product is subjected to its own downward vertical acceleration of 1g, and the centrifugal overload acceleration vector form is: The vector form of the Coriolis acceleration is: a c =2·ω e ×v g The acceleration vector form generated by the movement of the condensed products relative to the experimental engine is: The acceleration vector form generated by aerodynamic force is: Where F DLet be the aerodynamic force acting on the condensed product, which is generated by the pressure difference caused by the velocity difference on the surface of the condensed product. Let m be the mass of the condensed product. When a... e +a r ≥a D At this time, the condensed products will migrate along with the combustion surface and be collected by collection device B. When a e +a r <a D At that time, the condensed products will leave the combustion surface along with the combustion gas. Since the jet device is perpendicular to the shell and there is an inertial difference between the condensed products and the gas, the gas will be discharged from the jet device, and the condensed products will be collected in the collection device A.

[0020] As a preferred method, the transient combustion rate under overload is as follows:

[0021] Step 1: Determine the change in the amount of fuel gas stored in the free volume of the combustion chamber.

[0022] Taking the free volume of the entire combustion chamber as the control volume and based on the principle of mass conservation, the mass formation rate of the propellant burning surface is... It is divided into two parts: one part is discharged through the nozzle, i.e., the nozzle mass flow rate. The other part is the change in the amount of gas stored in the free volume of the combustion chamber. Right now The expression is:

[0023]

[0024] Step Two: [Regarding...] The expression is transformed.

[0025] The amount of fuel gas stored in the free volume of the combustion chamber is equal to the fuel gas density in the free volume of the combustion chamber multiplied by the free volume of the combustion chamber. The change in this value is the derivative with respect to time, i.e.:

[0026]

[0027] Quality production rate of burning surface This refers to the mass of solid propellant burned per unit time.

[0028]

[0029] The nozzle mass flow rate is:

[0030]

[0031] Combining equations (2), (3), and (4), equation (1) can be modified as follows:

[0032]

[0033] In the formula: ρ c V is the density of the gas; c ρ is the free volume of the combustion chamber; t is time; p For propellant density; A b r is the surface area of ​​the burning surface. at For transient combustion rate; C D A is the flow rate coefficient; t Γ is the cross-sectional area of ​​the nozzle throat; Γ is a function of the specific heat ratio k; R is the gas constant of the combustion gas; T c The temperature of the gas inside the combustion chamber;

[0034] Step 3: Determine the transient combustion rate r at The expression:

[0035] In order to calculate equation of state Taking the derivative with respect to time, and considering that the temperature and composition of the gas remain constant, RT c Since it is a constant, we get:

[0036]

[0037] The increase in free volume within the combustion chamber should equal the volume freed up by the reduction in propellant volume due to propellant combustion.

[0038]

[0039] The expression for the specific heat ratio k as a function Γ is:

[0040]

[0041] Substituting (6)(7)(8) into formula (5) yields the transient combustion rate r. at The expression is:

[0042]

[0043] In the formula: r at V0 is the transient burning rate of the solid propellant; V0 is the initial volume of the combustion chamber; R is the gas constant of the combustion gas; T0 is the transient burning rate of the solid propellant. c P represents the temperature of the combustion chamber gas. c The transient pressure in the combustion chamber was collected by a high-frequency pressure sensor (sampling frequency greater than 150kHz) installed on the experimental engine; A t R is the cross-sectional area of ​​the nozzle throat; R is the gas constant of the combustion gas; T c The combustion chamber gas temperature is represented by k; the specific heat ratio is represented by A. b ρ is the surface area of ​​the burning surface; p For propellant density;

[0044] The collecting device B includes a bottom cover, a PTFE gasket, an inner pad, and a box. The box is a hollow cylindrical structure with an open top. The PTFE gasket acts as a seal to prevent high-temperature gas from entering the collecting device B from the bottom. The propellant charge has a coating to prevent the high-temperature gas from corroding the collecting device B during combustion. The inner and outer pads act as buffers, jointly protecting the base of the collecting device B.

[0045] The sensor base is used to install a high-frequency (acquisition frequency greater than 150kHz) pressure sensor to measure the transient pressure inside the burner, thereby obtaining the transient combustion rate.

[0046] Preferably, the jetting device is fixedly welded to the side wall of the combustion chamber cavity.

[0047] An ignition charge is placed inside the cavity.

[0048] The nozzle throat has a diameter of 2mm and serves a positioning function. The actual diameter can be drilled according to test requirements to conduct overload tests under different pressures.

[0049] The present invention adopts an outer end cap design to provide a placement position and space for the dual collection device.

[0050] This invention provides an insulation jacket and nozzle bushing to protect the exposed internal parts of the experimental engine from corrosion by high-temperature, high-pressure gases. Furthermore, the entire structure is detachable and can be reused repeatedly.

[0051] Beneficial effects:

[0052] 1. This invention discloses an experimental engine capable of measuring transient burning rate and collecting condensed phase products under overload conditions. It combines the functions of measuring dynamic burning rate and collecting condensed phase products under overload conditions, and employs a dual collection device. Collection device B can collect condensed phase products that remain on the burning surface due to the overload force perpendicular to the burning surface being greater than the aerodynamic force, while simultaneously measuring the transient burning rate and analyzing the influence of condensed phase products remaining on the burning surface on the transient burning rate of solid propellants. This provides important guidance for studying the transient characteristics of aluminum-containing composite propellant combustion under overload conditions. Collection device A can collect condensed phase products that are carried away by the combustion gas flow when the aerodynamic drag is greater than the overload force perpendicular to the burning surface, enabling analysis of the relationship between aerodynamic force, the overload force perpendicular to the burning surface, and the particle size of the condensed phase products.

[0053] 2. The experimental engine disclosed in this invention, which combines the measurement of transient combustion rate and the collection of condensed phase products under overload conditions, has a collection device A divided into four regions: collection region 1 is the inner liner, collection region 2 is along the direction of gravitational acceleration, collection region 3 is along the direction of Coriolis acceleration, and there is also a collection region 4. This allows for the analysis of the effects of gravity and Coriolis acceleration on the two-phase flow pattern and the morphology, particle size, and composition of condensed phase products in the combustion chamber under overload conditions.

[0054] 3. The experimental engine disclosed in this invention, which combines the measurement of transient combustion rate and the collection of condensation products under overload conditions, employs a design with two identical outer end caps. This not only provides a location for the dual collection devices but also allows for free interchange of their orientation on the overload platform cantilever. Furthermore, the structural layout of the jet device perpendicular to the engine shaft enables overload experiments at any angle θ (0≤θ≤π). By changing the angular velocity of the overload platform cantilever beam, overload experiments of any magnitude can be conducted.

[0055] 4. The experimental engine disclosed in this invention, which combines the measurement of transient burning rate and the collection of condensation products under overload conditions, helps to improve the processing technology of solid propellants and enhance the performance of solid propellant engines, based on achieving the above-mentioned beneficial effects 1, 2, and 3. Attached Figure Description

[0056] Figure 1 is a schematic diagram of the engine used in this overload test; Figure a is a front view sectional view; Figure (b) is a left view sectional view along the nozzle axis of the overload test engine.

[0057] Figure 2 This is a schematic diagram showing the overload direction and the combustion surface retraction direction at an angle of θ (0°≤θ≤90°) in the implementation case.

[0058] Figure 3 This is a schematic diagram showing the overload direction and the combustion surface retraction direction at an angle of θ (90°≤θ≤180°) in the implementation case.

[0059] Figure 4 The acceleration analysis diagram of the condensed products generated by combustion when θ = 0°.

[0060] Figure 5 This is a scanning electron microscope image of the condensed products collected by collection device B under a 30g overload.

[0061] Figure 6 The transient combustion rate was obtained when the angle θ = 0° and the overload was 50g.

[0062] Among them: 1-Experimental engine, 2-Fixed device, 3-Overload platform, 1.1-End cover, 1.2-Combustion chamber shell, 1.3-Outer gasket, 1.4-Plug, 1.5-Bottom cover of collection device B, 1.6-O-ring seal, 1.7-PTFE gasket, 1.8-Inner gasket, 1.9-Collection device B box, 1.10-Solid propellant, 1.11-Insulating jacket, 1.12-Ignition charge, 1 1.13-Collection device A cover, 1.14-Collection device A box, 1.15-Igniter base, 1.16-Igniter seal, 1.17-Pressure sensor base, 1.18-Pressure relief valve base, 1.19-Burning plug, 1.20-Pressure relief valve head, 1.21-Nozzle base, 1.22-Nozzle head, 1.23-Nozzle bushing, 1.24-Nozzle throat sleeve, 1.25-Nozzle. Detailed Implementation

[0063] To better illustrate the purpose and advantages of the present invention, the present invention will be further described below with reference to the figures and specific embodiments.

[0064] As shown in Figure 1, the experimental engine disclosed in this embodiment, which combines the measurement of transient combustion rate and the collection of condensation products under overload conditions, includes an end cap 1.1, a combustion chamber shell 1.2, an outer gasket 1.3, a plug 1.4, a bottom cover of the collection device B 1.5, an O-ring seal 1.6, a PTFE gasket 1.7, an inner gasket 1.8, a box for the collection device B 1.9, a solid propellant 1.10, an insulating sleeve 1.11, an ignition charge 1.12, a cover for the collection device A 1.13, a box for the collection device A 1.14, an igniter base 1.15, an igniter seal 1.16, a pressure sensor base 1.17, a pressure relief valve base 1.18, a burst plug 1.19, a pressure relief valve end cap 1.20, a nozzle base 1.21, a nozzle end cap 1.22, a nozzle bushing 1.23, a nozzle throat sleeve 1.24, and a nozzle 1.25.

[0065] The assembly sequence is as follows: the nozzle base 1.21, pressure relief valve base 1.18, and pressure sensor base 1.17 are welded together with the housing 1.2. The insulation sleeve 1.11 is placed in the middle of the housing 1.2 and positioned by the nozzle bushing 1.23, with the bottom of the nozzle bushing 1.23 flush with the inner diameter of the insulation sleeve 1.11; note that the holes on the insulation sleeve 1.11 correspond one-to-one with the holes on the housing 1.2 in position and size. The ignition charge 1.12 is placed inside the insulation sleeve 1.11.

[0066] The collecting device A is placed on the right side of the combustion chamber housing 1.2. The right end cap 1.1 is connected to the housing 1.2 by threads and sealed by an O-ring 1.6. The ignition wire passes through the right end cap 1.1 and the collecting device A and is connected to the ignition charge 1.12, sealed by the igniter seal 1.16. The igniter base 1.15 is fixed to the right end cap 1.1 by threads.

[0067] Place the rupture plug 1.19 with its boss facing upwards on the pressure relief valve base 1.18; the pressure relief valve head 1.20 is connected to the pressure relief valve base 1.18 by a threaded connection, and the rupture plug 1.19 serves as a limit and seal.

[0068] The propellant charge 1.10 is pre-poured into the collection device B box 1.9. The bottom cover 1.5, PTFE gasket 1.7, and inner gasket 1.8 of the collection device B are fixed to the collection device B box 1.9 with hexagon socket screws. The collection device B is placed with the propellant charge side facing inward on the left side of the combustion chamber shell, followed by the outer gasket 1.3. The left end cover 1.1 is connected to the combustion chamber shell by threads and sealed with an O-ring 1.6. The plug 1.4 is connected to the left end cover 1.1 by threads.

[0069] The nozzle end cap 1.22 is connected to the nozzle base 1.21 by threads, fixing the nozzle 1.25 and nozzle throat sleeve 1.24 inside the nozzle base 1.21, and sealing the end face with a copper gasket. The required throat diameter is drilled according to the test requirements.

[0070] The operating method of the experimental engine that combines the measurement of transient combustion rate and the collection of condensation products under overload conditions disclosed in this embodiment is as follows:

[0071] The experimental engine 1 was assembled in the correct order.

[0072] The assembled overload test engine 1 is installed at the required angle according to the test requirements, i.e., the combustion surface retraction direction and the overload direction form a certain angle θ, as shown below. Figure 2 As shown (0°≤θ≤90°) or Figure 3 As shown (90°≤θ≤180°), it is fixed to the cantilever of the overload test platform 3 by fixing device 2. The distance l from the center of the nozzle 1.25 of the overload test engine 1 to the central axis of the overload test platform 3 is measured. According to the installation position of the charge 1.10, the distance L from the burning surface of the charge 1.10 to the central axis of the overload test platform 3 is calculated. The calibrated high-frequency pressure sensor is installed on the pressure sensor base 1.17 and connected to the data acquisition system. The ignition system is connected to the overload test engine.

[0073] The rotational speed of the overload test bench 3 is calculated based on the acceleration required for the test.

[0074] Turn on the overload test bench 3 and start rotating. After the rotation is stable, turn on the data acquisition system. Then, ignite the overload test engine 1 and measure and collect the transient pressure in the combustion chamber under overload.

[0075] After shutting down the data acquisition system and overload stage 3 and stopping rotation, remove the overload test engine 1, disassemble the overload test engine 1, and collect the condensed products in collection device A and collection device B.

[0076] Clean and disassemble the overload test engine 1, reassemble it, and conduct the next test.

[0077] The transient combustion rate is obtained by taking the transient pressure in the combustion chamber as collected through the following steps:

[0078] Step 1: Perform forward differencing on the collected transient pressure (pressure-time) data, i.e.:

[0079]

[0080] In the formula: P c The transient pressure is denoted as Δt, which is the time difference between two consecutive data collections from the high-frequency pressure sensor.

[0081] Step 2: Determine the parameters of experimental engine 1, including the initial combustion chamber volume V0 and the nozzle throat cross-sectional area A. t ;

[0082] Step 3: Determine the parameters of the experimental solid propellant charge 1.10, including the gas constant R of the combustion gas and the combustion chamber temperature T. c (With an insulating jacket and nozzle bushing, it can be assumed that there is no heat loss in the combustion chamber; that is, the adiabatic combustion temperature of the propellant can be used as the gas temperature T) c ), specific heat ratio k, combustion surface area A b Propellant density ρ p .

[0083] Step 4: Substitute the results from the first three steps into the transient burning rate calculation model (9) to obtain the transient burning rate of the solid propellant under overload. For example... Figure 6 The figure shows the transient combustion rate-time curve obtained when the overload direction forms an angle θ = 0° with the combustion surface retraction direction and the overload magnitude is 50g.

[0084] The collected condensed products were analyzed by scanning electron microscopy to determine their microstructure (see reference). Figure 5 ), composition, particle size and other parameters.

[0085] This embodiment can collect the condensed phase products generated by the combustion of solid propellant and carried away by the gas flow, as well as the condensed phase products remaining on the combustion surface, under different overloads and at any angle between the overload direction and the direction of combustion surface retreat. At the same time, it can obtain the combustion chamber pressure of the experimental engine and the transient burning rate of the propellant, which is of great significance for evaluating propellant formulation and predicting the performance of solid rocket engines.

[0086] The above description further details the purpose, technical solution, and advantages of the present invention. It should be understood that the above description is only a specific implementation method of the present invention and is used to explain the present invention. It is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An experimental engine capable of measuring transient combustion rate and collecting condensation products under overload conditions, characterized in that: The experimental engine (1) that combines the measurement of transient burning rate and the collection of condensed products, the fixed fixture (2), and the overload stage (3) are included. The experimental engine (1) that combines the measurement of transient burning rate and the collection of condensed products is fixed on the cantilever of the overload stage (3) by the fixed fixture (2), and the overload environment of the engine is simulated by rotating the cantilever of the overload stage. The experimental engine (1), which combines the functions of measuring transient combustion rate and collecting condensed products, is referred to as the experimental engine (1). It includes an end cap (1.1), a combustion chamber shell (1.2), an outer gasket (1.3), a plug (1.4), a bottom cover of the collection device B (1.5), an O-ring seal (1.6), a gasket (1.7), an inner gasket (1.8), a collection device B box (1.9), solid propellant (1.10), an insulating jacket (1.11), and an ignition charge (1). .12) Collection device A cover (1.13), Collection device A box (1.14), Igniter base (1.15), Igniter seal (1.16), Pressure sensor base (1.17), Pressure relief valve base (1.18), Bursting plug (1.19), Pressure relief valve head (1.20), Nozzle base (1.21), Nozzle head (1.22), Nozzle bushing (1.23), Nozzle throat sleeve (1.24), Nozzle (1.25); The solid propellant (1.10) has a coating layer and is pre-cast into the collection device B box (1.9); the experimental engine (1) is placed on the overload platform (3) cantilever, and the overload environment during missile flight is simulated by rotating the overload platform (3) cantilever; that is, when the overload force on the condensed products generated by the combustion of the solid propellant charge (1.10) is greater than the aerodynamic force on the condensed products, the condensed products will remain on the combustion surface and be directly collected by the collection device B; The combustion chamber shell (1.2) is a hollow cylinder; Collection device B and collection device A are located at the left and right ends of the casing (1.2) respectively, facing each other; the jet device is perpendicular to the combustion chamber casing (1.2); the gas generated by the propellant (1.10) combustion surface and the condensed products flowing with the gas will move along the axial direction of the engine (1). When it reaches the inlet of the jet device, due to the difference in inertia between the gas and the condensed products, the gas will slip away through the jet device, and the condensed products will continue to move along the axial direction and enter the collection device A; The collecting device B includes a bottom cover (1.5), a gasket (1.7), an inner gasket (1.8), and a box (1.9). The box (1.9) is a hollow cylindrical structure with an open top. The gasket (1.7) acts as a seal to prevent high-temperature gas from entering the collecting device B from the bottom. At the same time, the explosive charge (1.10) has a coating layer to prevent high-temperature gas from corroding the collecting device B during combustion. The inner gasket (1.8) and the outer gasket (1.3) act as a buffer to protect the bottom cover (1.5) of the collecting device B.

2. The experimental engine for measuring transient combustion rate and collecting condensation products under overload conditions as described in claim 1, characterized in that: The sensor base (1.17) is used to install a high-frequency pressure sensor to measure the pressure inside the burner. By analyzing the combustion chamber pressure, propellant performance, and engine parameters, a transient burning rate calculation model for solid propellants is established. The transient burning rate calculation model for solid propellants is used to achieve high-precision and efficient measurement of transient burning rate, which facilitates the analysis of the transient characteristics of the propellant.

3. The experimental engine for measuring transient combustion rate and collecting condensation products under overload conditions as described in claim 2, characterized in that: The collection device A includes four areas: collection area 1 is the inner liner, collection area 2 is along the direction of gravitational acceleration, collection area 3 is along the direction of Coriolis acceleration, and there is also a collection area 4; then, the effects of gravity and Coriolis acceleration on the two-phase flow law and the morphology, particle size and composition of condensed products in the combustion chamber under overload are analyzed.

4. The experimental engine for measuring transient combustion rate and collecting condensation products under overload conditions as described in claim 3, characterized in that: The structure is designed with the jet device and the combustion chamber shell (1.2) perpendicular to each other. Even if the angle θ between the overload direction and the combustion surface retreat direction is ≥90°, the high-temperature gas ejected by the jet device will not damage the fixing device (2) and the overload platform (3). That is, it is possible to conduct overload experiments with the overload direction at any angle θ (0≤θ≤π) between the overload direction and the combustion surface retreat direction. At the same time, the end caps (1.1) on both sides of the engine are the same, which makes it convenient to switch their positions on the overload platform (3). By changing the angular velocity ω of the overload platform (3) cantilever, different overload environments can be simulated. That is, the present invention can measure the transient burning rate of the propellant and collect condensed products under different overload conditions with the overload direction at any angle θ (0≤θ≤π) between the overload direction and the combustion surface retreat direction.

5. The experimental engine for measuring transient combustion rate and collecting condensation products under overload conditions as described in claim 4, characterized in that: By placing the engine symmetrically along both cantilever arms, two operating conditions can be tested at once, significantly reducing experimental costs.

6. The experimental engine for measuring transient combustion rate and collecting condensation products under overload conditions as described in claim 5, characterized in that: The inner diameter of the collecting device A is larger than the inner diameter of the middle part of the combustion chamber shell (1.2), which is beneficial for the collection of condensed products; the outer diameter of the collecting device A is smaller than the inner diameter of the right side part of the combustion chamber shell (1.2), which is beneficial for removing the collecting device A.

7. The experimental engine for measuring transient combustion rate and collecting condensation products under overload conditions as described in claim 6, characterized in that: The initial distance between the propellant (1.10) combustion surface and the collection device A is only 100mm, and the distance between the central axis of the jet device and the collection device A is only 30mm, which is conducive to the entry of condensed products into the collection device A.

8. The experimental engine for measuring transient combustion rate and collecting condensation products under overload conditions as described in claim 6, characterized in that: When the overload direction forms an angle θ=0° with the combustion surface retreat direction, the collection method for collection device B is as follows: The experimental engine (1) is clamped on the cantilever of the overload platform (3) and rotates counterclockwise with the cantilever. The angular velocity of the rotation is constant. The speed is The vector distance from the condensed product to the center of the overload stage (3) is The relative velocity between the condensed products and the experimental engine (1) is ; The condensed product is subjected to its own downward vertical acceleration of 1g, and the centrifugal overload acceleration vector form is: The Coriolis acceleration vector form is: The acceleration vector generated by the movement of the condensed products relative to the experimental engine (1) is in the form of: The acceleration vector form generated by aerodynamic force is: F D Let be the aerodynamic force acting on the condensed product, which is generated by the pressure difference caused by the velocity difference on the surface of the condensed product; m is the mass of the condensed product; when At that time, the condensed phase products will migrate along with the burning surface; Thus it is collected by collecting device B; when At that time, the condensed products will leave the combustion surface along with the combustion gas. Since the jet device is perpendicular to the combustion chamber shell (1.2) and there is an inertial difference between the condensed products and the gas, the gas will slip away from the jet device, and the condensed products will be collected in the collection device A.

9. The experimental engine for measuring transient combustion rate and collecting condensation products under overload conditions as described in claim 6, characterized in that: The method for collecting transient combustion rate under overload is as follows: Step 1: Determine the change in the amount of fuel gas stored in the free volume of the combustion chamber. ; Taking the free volume of the entire combustion chamber as the control volume and based on the principle of mass conservation, the mass formation rate of the propellant burning surface is... It is divided into two parts: one part is discharged through the nozzle, i.e., the nozzle mass flow rate. The other part is the change in the amount of gas stored in the free volume of the combustion chamber. ;Right now The expression is: Step Two: [Regarding...] Transform the expression; The amount of fuel gas stored in the free volume of the combustion chamber is equal to the fuel gas density in the free volume of the combustion chamber multiplied by the free volume of the combustion chamber. The change in this value is the derivative with respect to time, i.e.: Quality production rate of burning surface The mass of solid propellant burned per unit time; that is The nozzle mass flow rate is: Combined The formula Change to: In the formula: The density of the gas; t represents the free volume of the combustion chamber; t represents time. For propellant density; The surface area of ​​the burning surface; Transient combustion rate; The flow rate coefficient; This represents the cross-sectional area of ​​the nozzle throat. is a function of the specific heat ratio k; R is the gas constant of the fuel gas; The temperature of the gas inside the combustion chamber; Step 3: Determine the transient combustion rate The expression: In order to calculate , the state equation Taking the derivative with respect to time, and assuming that the temperature and composition of the gas remain constant, It is a constant; have to: The increase in free volume within the combustion chamber should equal the volume freed up by the reduction in propellant volume due to propellant combustion. Function of specific heat ratio k The expression is: Will Substitute into the formula Obtain transient combustion rate The expression is: In the formula: The transient burning rate of the solid propellant; R is the initial volume of the combustion chamber; R is the gas constant of the combustion gas. The temperature of the gas inside the combustion chamber; The transient pressure in the combustion chamber was collected by a high-frequency pressure sensor installed on the experimental engine. R is the cross-sectional area of ​​the nozzle throat; R is the gas constant of the combustion gas. The combustion chamber gas temperature is represented by k; k is the specific heat ratio. The surface area of ​​the burning surface; This refers to the propellant density.

10. The experimental engine for measuring transient combustion rate and collecting condensation products under overload conditions as described in claim 6, characterized in that: The sensor base (1.17) is used to install a high-frequency pressure sensor to measure the transient pressure inside the burner and thus obtain the transient combustion rate; The jetting device is fixedly welded to the side wall of the combustion chamber cavity; An ignition charge (1.12) is placed inside the cavity. The nozzle (1.25) has a throat diameter of 2mm, which serves as a positioning tool. The actual diameter is drilled according to the test requirements to conduct overload tests under different pressures. The design of the outer end cap (1.1) provides a place and space for the dual collection device; The heat insulation jacket (1.11) and nozzle bushing (1.23) protect the exposed parts inside the experimental engine (1) from high temperature and high pressure gas corrosion; and the whole structure is easy to disassemble and can be reused.

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