A dynamic measurement system and method for dynamic ablation rate of a solid rocket engine thermal protection layer

Abstract

The application provides a solid rocket engine heat insulation layer dynamic ablation rate dynamic measurement system and method based on a spiral gradient thermocouple array. The system arranges the thermal gradient thermocouple sensors in a spiral shape along the vertical direction of the heat insulation layer surface, and arranges 10-20 sensors on the thickness of the heat insulation layer to meet the measurement requirements. The normal distance between each sensor increases along the gradient, the ablation serious area is arranged more densely, and the ablation weak position is arranged sparsely to save the measurement cost. The thermocouples are connected to the multi-core aviation plug of the front head through the wires embedded between the heat insulation layer and the engine shell, the aviation plug is embedded in the top cover of the front head through screw connection and is sealed by using sealing glue, the other end of the multi-core aviation plug is connected with the data acquisition system, the high-frequency sampling module, the differential amplification circuit and the temperature compensation module are arranged in the data acquisition system, the continuous ablation depth and ablation rate curves can be obtained, and accurate measurement is realized.

Description

Technical Field

[0001] This invention belongs to the field of aerospace thermal protection ablation testing technology, specifically relating to a dynamic measurement system and method for the dynamic ablation rate of the insulation layer of a solid rocket engine based on a helical gradient thermocouple array, used to test the dynamic ablation process of the insulation layer and thermal protection structure of a solid rocket engine during operation. Background Technology

[0002] During the operation of solid rocket motors, high temperature (3500K), high pressure (up to 10MPa), and multiphase combustion gases (aluminum particles in liquid and solid phases) continuously ablate the insulation layer exposed to the harsh environment, posing a significant challenge to the engine's thermal protection design. Dynamic ablation monitoring technology for the insulation layer is a key technology for accurately assessing the thermal structural safety of the engine, and accurate measurement of the ablation rate is crucial for ensuring normal engine operation. Traditional methods for measuring insulation ablation involve dissecting the engine after ignition testing and directly measuring the remaining thickness of the insulation layer in key areas to infer the ablation thickness and obtain the average ablation rate of the insulation layer during operation. This method lacks real-time testing capabilities, cannot obtain the relationship between the ablation rate and time during engine operation, and the self-sustaining combustion of the insulation layer after engine operation also affects measurement accuracy. Accurate dynamic ablation measurement of the insulation layer is of significant engineering importance and practical value for obtaining the dynamic ablation rate of the insulation layer, optimizing insulation design schemes, and selecting reliable insulation materials. Summary of the Invention

[0003] (a) Technical problems to be solved

[0004] This invention proposes a dynamic measurement system and method for the dynamic ablation rate of the insulation layer of a solid rocket motor based on a helical gradient thermocouple array, in order to solve the technical problem of how to accurately measure the dynamic ablation rate of the insulation layer of a solid rocket motor.

[0005] (II) Technical Solution

[0006] To address the aforementioned technical problems, this invention proposes a dynamic ablation rate measurement system for the insulation layer of a solid rocket motor. This system includes a helical rubber support frame and thermocouple sensor assembly, pre-embedded wires, an aviation connector, and a data acquisition system.

[0007] The spiral rubber support frame and thermocouple sensor assembly are embedded in the insulation layer of the engine casing of the engine under test, and are used to dynamically measure the ablation of the insulation layer.

[0008] The pre-embedded wire is installed inside the engine, with one end connected to the thermocouple sensor assembly and the other end connected to the data acquisition system via an aviation connector;

[0009] The aviation plug serves as an electrical connector between the inside and outside of the engine. Its inner side connects to the wires of the thermocouple sensor assembly, and its outer side connects to the data acquisition system. It is used to transmit electrical signals from the thermocouple sensor assembly to the data acquisition system, supply power to the thermocouple sensor assembly, and seal the engine.

[0010] The data acquisition system is located outside the engine and is used to collect discrete temperature data of the thermocouple sensor assembly and obtain continuous dynamic ablation rate results through the ablation inversion model.

[0011] Furthermore, the spiral rubber support frame and thermocouple sensor assembly includes a thermocouple sensor and a spiral rubber support frame; wherein, multiple thermocouple sensors are mounted on the spiral rubber support frame; when the ablation surface ablates and contacts the thermocouple sensor from the bottom up, the temperature of the thermocouple sensor rises instantaneously to the upper limit of measurement, and then the thermocouple sensor is exposed, burns and fails, and the signal disappears.

[0012] Furthermore, the spiral rubber support frame has sensor mounting holes of the same outer diameter as the thermocouple sensor evenly arranged in four quadrants. The thermocouple sensor is installed on the spiral support frame along the four quadrants and arranged spirally along the longitudinal depth.

[0013] Furthermore, the density of thermocouple sensors in the ablation zone of the insulation layer is greater than that in the heat transfer and heating zone of the insulation layer; a thermocouple sensor is placed in the constant temperature zone at the edge of the insulation layer, and the measurement error caused by environmental temperature drift is automatically corrected by comparing the differences with other thermocouple signals.

[0014] Furthermore, the thermocouple sensor uses a miniature probe thermocouple with a temperature probe at the front end for measuring temperature, and the measurement range is from room temperature to 1200℃.

[0015] Furthermore, the material of the spiral rubber support frame is the same as that of the insulation layer.

[0016] Furthermore, the pre-embedded wires are arranged between the engine casing and the insulation layer; the aviation plug is fixed to the front end cap plate at the front end of the engine casing by threads and sealed with sealant, and the inner side of the aviation plug is provided with an insulation layer.

[0017] Furthermore, the data acquisition system includes a high-frequency sampling module, a differential amplifier circuit, and a temperature compensation module; wherein, the high-frequency sampling module is used to acquire the voltage signal of the thermocouple sensor; the differential amplifier adopts a low-temperature drift instrumentation amplifier to suppress common-mode noise signals; the temperature compensation module monitors the ambient temperature through a built-in constant-temperature thermocouple to correct drift in real time.

[0018] Furthermore, this invention proposes a dynamic measurement method for the ablation rate of the insulation layer in a solid rocket engine. Employing the aforementioned dynamic ablation rate measurement system, the method includes the following steps: At the start of the test, high-temperature, high-pressure gas inside the engine continuously ablates the insulation layer, exposing the uppermost thermocouple sensor. When the measured value reaches the upper limit, it is considered that the insulation layer has ablated to that position. Subsequently, the insulation layer further ablates downwards to the next thermocouple sensor. The data acquisition system collects discrete temperature data from the thermocouple sensor assembly and obtains the continuous dynamic ablation rate result through an ablation inversion model.

[0019] Furthermore, the ablation inversion model is as follows:

[0020]

[0021] Where T is the temperature collected by the thermocouple sensor; t is time; x i denoted as , where is the depth of the thermocouple sensor from the ablation interface; i is the thermocouple sensor number; s(t) is the ablation depth, s(t)' = ds / dt is the ablation rate; α is the thermal diffusivity, α = k / ρC. p ρ is the material density, C p K is the specific heat capacity, and k is the thermal conductivity.

[0022] The boundary conditions of the ablation inversion model are expressed as follows:

[0023] Ablated surface, x = 0: T(0,t) = 1200℃;

[0024] Insulation layer and shell interface x = L:

[0025]

[0026] Where L is the thickness of the insulation layer.

[0027] (III) Beneficial Effects

[0028] This invention proposes a dynamic measurement system and method for the ablation rate of a solid rocket motor insulation layer based on a spiral gradient thermocouple array. The system uses a spiral arrangement of thermocouple sensors along the vertical direction of the insulation layer surface. Ten to twenty sensors are evenly distributed across the insulation layer thickness to meet measurement requirements. The normal distance between each sensor increases along a gradient, with denser sensors in severely ablated areas and sparser sensors in weakly ablated areas to save measurement costs. The thermocouples are connected to a multi-core aviation connector on the front end cap via wires embedded between the insulation layer and the engine casing. The aviation connector is embedded in the top cover of the front end cap via a threaded connection and sealed with sealant. The other end of the multi-core aviation connector is connected to a data acquisition system. The data acquisition system includes a high-frequency sampling module, a differential amplifier circuit, and a temperature compensation module, enabling the acquisition of continuous ablation depth and ablation rate curves for accurate measurement.

[0029] This invention uses the sudden temperature rise observed when thermocouples are exposed during the ablation process of the insulation layer to determine when ablation has reached that layer. Simultaneously, the thermocouples, arranged in a gradually sparse spiral pattern from the outside to the inside along the ablation direction, can acquire discrete data on the ablation depth. Through a data acquisition system and an ablation inversion model, continuous ablation depth and ablation rate curves are obtained. This breakthrough overcomes the limitations of parameter monitoring and quantitative ablation assessment techniques during the ablation process, establishing a complete dynamic ablation performance monitoring system. This invention has the advantages of simple principle, high adaptability, and accurate measurement, and shows promising application prospects for measuring the ablation rate of insulation layers and engine thermal protection design.

[0030] Compared with existing insulation layer measurement methods, the present invention has the following advantages:

[0031] 1. The thermocouple sensor array proposed in this invention can accurately capture the position of the ablation surface in real time, and has the characteristics of accuracy and effectiveness.

[0032] 2. The spiral arrangement scheme and pre-installed rubber spiral frame proposed in this invention arrange the thermocouple sensor array along the spiral in the depth direction, which can avoid the influence of the pre-embedded thermocouple sensor cavity on the ablation rate measurement.

[0033] 3. The gradient arrangement scheme along the depth direction proposed in this invention can optimize the arrangement of thermocouple sensors, save measurement resources, and reduce measurement costs.

[0034] 4. The data acquisition system proposed in this invention includes a high-frequency sampling module, a differential amplifier circuit, and a temperature compensation module. The thermocouples arranged in the constant temperature zone can automatically correct measurement errors caused by environmental temperature drift.

[0035] 5. The ablation inversion model proposed in this invention can calculate the continuous ablation process and ablation rate results by using the inversion model to obtain discrete ablation data. Attached Figure Description

[0036] Figure 1 This is a schematic diagram illustrating the composition and working principle of the dynamic ablation rate measurement system for the thermal insulation layer of a solid rocket engine according to the present invention.

[0037] Figure 2 This is an assembly diagram of the spiral rubber support frame and thermocouple sensor assembly in this invention (one quadrant does not have thermocouple sensors arranged to show the mounting holes);

[0038] Figure 3 This is a schematic diagram of the thermocouple sensor structure in this invention;

[0039] Figure 4 This is the data acquisition system architecture in this invention.

[0040] In the diagram: 1-Engine housing; 2-Engine insulation layer; 3-Spiral rubber support frame and thermocouple sensor assembly; 4-Embedded wire; 5-Aerospace connector; 6-Data acquisition system; 7-Thermocouple sensor; 8-Spiral rubber support frame. Detailed Implementation

[0041] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0042] This embodiment proposes a dynamic measurement system for the ablation rate of the insulation layer of a solid rocket motor based on a helical gradient thermocouple array. Its composition and working principle are as follows: Figure 1 As shown, it mainly includes a spiral rubber support frame and thermocouple sensor assembly 3, pre-embedded wires 4, aviation plug 5, and data acquisition system 6.

[0043] The spiral rubber support frame and thermocouple sensor assembly 3 are embedded in the insulation layer 2 of the engine casing 1 of the engine under test, for dynamic measurement of the ablation condition of the insulation layer 2. Figure 2As shown, the spiral rubber support frame and thermocouple sensor assembly 3 includes a thermocouple sensor 7 and a spiral rubber support frame 8. The spiral rubber support frame 8 has sensor mounting holes of the same outer diameter as the thermocouple sensor 7 evenly distributed in four quadrants. The thermocouple sensor 7 is mounted on the spiral support frame 8 along the four quadrants, with its probe extending into the mounting hole and facing outwards. The spacing between the thermocouple sensors 7 is gradient-arranged as needed. Based on previous ablation experience, the ablation zone of the insulation layer 2 can be roughly divided into an ablation zone, a heat transfer and heating zone, and an edge isothermal zone. Based on the gradient arrangement method, the thermocouple sensors 7 are densely arranged in the ablation zone, with an interval of 1 mm between adjacent thermocouple sensors 7; and sparsely arranged in the heat transfer and heating zone, with an interval of 2 mm between adjacent thermocouple sensors 7. This gradient arrangement effectively reduces measurement costs without affecting measurement accuracy. A thermocouple sensor 7 is arranged in the edge constant temperature zone. The thermocouple sensor 7 in the constant temperature zone mainly corrects the measurement error caused by the ambient temperature drift (outdoor test temperature range of -40 to +55℃) by comparing the differences of other thermocouple signals.

[0044] Thermocouple sensor 7 uses a miniature probe thermocouple, such as Figure 3 As shown, its front end is a temperature probe for measuring temperature, with a measurement range from room temperature to 1200℃. The moment when the temperature of the thermocouple sensor 7 reaches the upper limit of measurement (1200℃) is defined as the standard when the insulation layer ablates to that position. When the ablated surface contacts the thermocouple sensor 7 from the bottom up, the temperature of the thermocouple sensor 7 rises instantaneously to the upper limit of measurement, and then the thermocouple sensor 7 is exposed, burns out, and loses its signal.

[0045] At the start of the test, the high-temperature and high-pressure gas inside the engine continuously ablates the insulation layer 2, exposing the thermocouple sensor 7 located at the top. When the measured value reaches the upper limit, it is considered that the insulation layer 2 has ablated to that position. Subsequently, the insulation layer 2 ablates further downward to the next thermocouple sensor 7, and so on.

[0046] To avoid the upper thermocouple sensor 7 burning out the reserved inner cavity and accelerating the ablation rate at that longitudinal position when the thermocouple sensor 7 is arranged in a straight line along the depth, thus causing a superimposed effect that affects the accuracy of ablation measurement, the thermocouple sensor 7 is arranged spirally along the longitudinal depth. By arranging the sensors spirally along the thickness direction of the insulation layer, the superimposed effect caused by the upper sensor burning out the reserved inner cavity and accelerating the ablation rate when the sensors are arranged in a straight line is avoided, thereby improving the measurement accuracy.

[0047] Thermocouple sensors 7, arranged on the spiral rubber support frame 8, are pre-positioned before the EPDM insulation layer 2 is cured and formed, achieving a spiral distribution within the insulation layer 2. Meanwhile, the material of the spiral rubber support frame 8 is the same as that of the insulation layer 2—EPDM rubber—so it does not affect the ablation resistance of the insulation layer 2.

[0048] The multi-core aviation connector 5 serves as an electrical connector between the engine's internal and external systems. Its inner side connects to the wires of the thermocouple sensor 7, while its outer side connects to the data acquisition system 6. It transmits electrical signals from the thermocouple sensor 7 to the data acquisition system 6, supplies power to the thermocouple sensor 7, and seals the engine. The aviation connector 5 is threaded onto the front end cap plate at the front of the engine housing 1 and sealed with sealant to meet the engine's sealing and pressure requirements. The aviation connector 5 possesses high-pressure resistance characteristics, ensuring it meets the engine's sealing requirements. An insulation layer is arranged on the inner side of the aviation connector 5 to prevent erosion damage from the thermal environment during engine operation.

[0049] The pre-embedded wire 4 is installed inside the engine, with one end connected to the thermocouple sensor 7 and the other end connected to the data acquisition system 6 via the aviation connector 5. The pre-embedded wire 4 is arranged between the engine casing 1 and the insulation layer 2 to avoid the problem of wire burn-out failure due to high temperature erosion.

[0050] The data acquisition system 6 is located outside the engine and is used to collect discrete temperature data from each thermocouple sensor 7. For example... Figure 4 As shown, the data acquisition system includes a high-frequency sampling module, a differential amplifier circuit, and a temperature compensation module. The high-frequency sampling module acquires the voltage signal of the thermocouple sensor 7 at a frequency of 1 kHz, with a resolution of 0.1℃. The differential amplifier uses a low-temperature drift instrumentation amplifier to suppress common-mode noise signals. The temperature compensation module monitors the ambient temperature through a built-in constant-temperature thermocouple to correct drift in real time.

[0051] The experimental procedure for dynamic measurement of the insulation layer ablation rate is as follows: During engine processing and assembly, the spiral rubber support frame, thermocouple sensor assembly 3, pre-embedded wire 2, and aviation connector 5 are arranged in the designed positions; before the test begins, the data acquisition system 6 is connected to the aviation connector 5, and the measurement power is turned on; at the start of the test, the engine operates, and the measurement system records the test data in real time; after the test, the measurement data is used to obtain the continuous dynamic ablation rate result through the ablation inversion model. The test accuracy can be verified by conventional post-testing methods.

[0052] After the data acquisition system 6 acquires the discrete temperature data of each thermocouple sensor 7, the continuous ablation process and ablation rate are obtained through the ablation inversion model. The ablation inversion model is as follows:

[0053]

[0054] Where T is the temperature collected by the thermocouple sensor; t is time; x i denoted as , where is the depth of the thermocouple sensor from the ablation interface; i is the thermocouple sensor number; s(t) is the ablation depth, and s(t)' = ds / dt is the ablation rate.

[0055] The boundary conditions of the ablation inversion model are expressed as follows:

[0056] Ablated surface, x = 0: T(0,t) = 1200℃;

[0057] Insulation layer and shell interface x = L:

[0058]

[0059] Where L is the thickness of the insulation layer.

[0060] This model is a generalization based on one-dimensional unsteady heat conduction and mass migration caused by ablation:

[0061]

[0062] Where ρ is the material density, C p ρ is the specific heat capacity, k is the thermal conductivity, and the thermal properties of the material are constant, i.e., ρ and C. p With k constant, the thermal diffusivity α = k / ρC p The inversion ablation model can be solved by partial differential discretization, and the ablation depth and ablation rate are expressed by s(t) and s(t)'.

[0063] The design features of this invention are as follows:

[0064] 1. This invention establishes a complete dynamic ablation measurement system for the insulation layer of a solid rocket engine, including a thermocouple sensor array, a measurement and control system, a cable layout scheme, and an ablation inversion model. The measurement scheme can provide effective and accurate data for the ablation of the insulation layer.

[0065] 2. This invention uses a miniature probe thermocouple to measure the position of the ablation surface. When the ablation surface ablates downwards and contacts the thermocouple, the moment when the thermocouple temperature rises instantaneously to the upper limit of measurement is defined as the moment when the insulation layer ablates to that position. Subsequently, the thermocouple is exposed and burns out, and the signal disappears.

[0066] 3. The present invention arranges thermocouples in a spiral shape using a spiral rubber support frame to achieve a spiral distribution within the insulation layer. The support frame material is the same as the insulation layer material, so it does not affect the influence of the support frame material on the ablation resistance of the insulation layer.

[0067] 4. In this invention, the thermocouple sensor array is arranged spirally along the depth direction, avoiding the accelerated ablation rate caused by the superposition effect of the embedded cavity when the sensor is arranged in a straight line along the depth direction. Therefore, the spiral arrangement of the thermocouples along the depth direction reduces the superposition effect of the embedded cavity, ensuring measurement accuracy.

[0068] 5. The present invention adopts a gradient-based thermocouple arrangement method, in which thermocouples are densely arranged in the ablation zone, sparsely arranged in the heat transfer and heating zone, and a temperature drift comparison thermocouple is arranged in the constant temperature zone.

[0069] 6. This invention connects the internal and external circuit signals of the engine through a multi-core aviation connector, ensuring the engine's airtightness.

[0070] 7. The data acquisition system of the present invention is divided into a high-frequency sampling module, a differential amplifier circuit, and a temperature compensation module, wherein the temperature compensation module is used to correct the ambient temperature and improve the measurement accuracy.

[0071] 8. After obtaining discrete ablation data, the present invention calculates the continuous ablation process and ablation rate through an ablation inversion model.

[0072] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A dynamic measurement system for the ablation rate of the insulation layer of a solid rocket motor, characterized in that, The dynamic ablation rate measurement system includes a spiral rubber support frame and thermocouple sensor assembly, pre-embedded wires, an aviation connector, and a data acquisition system; wherein... The spiral rubber support frame and thermocouple sensor assembly are embedded in the insulation layer of the engine casing of the engine under test, and are used to dynamically measure the ablation of the insulation layer. The pre-embedded wire is installed inside the engine, with one end connected to the thermocouple sensor assembly and the other end connected to the data acquisition system via an aviation plug; The aviation plug serves as an electrical connector between the inside and outside of the engine. Its inner side is connected to the wires of the thermocouple sensor assembly, and its outer side is connected to the data acquisition system. It is used to transmit electrical signals from the thermocouple sensor assembly to the data acquisition system, supply power to the thermocouple sensor assembly, and seal the engine. The data acquisition system is located outside the engine and is used to collect discrete temperature data of the thermocouple sensor assembly and obtain continuous dynamic ablation rate results through the ablation inversion model. The spiral rubber support frame and thermocouple sensor assembly includes thermocouple sensors and a spiral rubber support frame; multiple thermocouple sensors are mounted on the spiral rubber support frame; when the ablation surface contacts the thermocouple sensor from the bottom up, the temperature of the thermocouple sensor rises instantaneously to the upper limit of measurement, and then the thermocouple sensor is exposed, burns out and fails, and the signal disappears; the spiral rubber support frame has sensor mounting holes of the same outer diameter as the thermocouple sensors evenly arranged in four quadrants, and the thermocouple sensors are installed on the spiral support frame along the four quadrants and arranged spirally along the longitudinal depth; the arrangement density of thermocouple sensors in the ablation zone of the insulation layer is greater than the arrangement density in the heat transfer and heating zone of the insulation layer; a thermocouple sensor is arranged in the constant temperature zone at the edge of the insulation layer, and the measurement error caused by environmental temperature drift is automatically corrected by comparing the differences of other thermocouple signals; the thermocouple sensor adopts a miniature probe thermocouple, with a temperature measuring probe at the front end for measuring temperature, and the measurement range is from room temperature to 1200℃; the material of the spiral rubber support frame is the same as that of the insulation layer. The pre-embedded wires are arranged between the engine housing and the insulation layer; the aviation plug is fixed to the front end cap plate at the front end of the engine housing by threads and sealed with sealant, and an insulation layer is arranged on the inner side of the aviation plug. The data acquisition system includes a high-frequency sampling module, a differential amplifier circuit, and a temperature compensation module. The high-frequency sampling module is used to acquire the voltage signal of the thermocouple sensor. The differential amplifier is a low-temperature drift instrumentation amplifier used to suppress common-mode noise signals. The temperature compensation module monitors the ambient temperature through a built-in constant-temperature thermocouple to correct drift in real time.

2. A method for dynamically measuring the ablation rate of the insulation layer of a solid rocket motor, characterized in that, The dynamic ablation rate measurement system according to claim 1 includes the following steps: At the start of the test, the high-temperature and high-pressure gas inside the engine continuously ablates the insulation layer, exposing the uppermost thermocouple sensor. When the measured value reaches the upper limit, it is considered that the insulation layer has ablated to the uppermost thermocouple sensor, and then the insulation layer further ablates downward to the next thermocouple sensor; the data acquisition system collects the discrete temperature data of the thermocouple sensor assembly and obtains the continuous dynamic ablation rate result through the ablation inversion model; The ablation inversion model is as follows: in, T The temperature collected by the thermocouple sensor; t For time; x i The depth of the thermocouple sensor from the ablation interface; i This is the serial number of the thermocouple sensor; s ( t () represents the ablation depth. s ( t )'= ds / dt The ablation rate; α For thermal diffusivity, α = k / ρC p , ρ For material density, C p For specific heat capacity, k Thermal conductivity; The boundary conditions of the ablation inversion model are expressed as follows: Surface ablation x =0: ; Insulation layer and shell interface x = L : in, L This refers to the thickness of the insulation layer.

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