Cold light electroless combustion chamber grain deformation measurement system based on multimode optical fiber imaging

Abstract

The invention relates to the technical field of online combustion chamber detection, and particularly discloses a cold light non-electric combustion chamber grain deformation measurement system based on multimode optical fiber imaging, which adopts an annularly arranged multimode optical fiber array combined with a cold light source imaging technology to realize non-contact measurement of grain surface deformation through a light intensity modulation principle. The system comprises a cold light emitting module, a multimode optical fiber sensing array, a high-resolution imaging module and a deformation analysis module. During working, cold light is projected to the surface of the grain through the optical fiber array, and reflected light intensity distribution is captured by the optical fiber along with deformation change. The device can work in a high-temperature and high-pressure environment without a power supply element, the problems that a traditional electrical measurement method is high in electromagnetic interference and poor in temperature resistance are solved, and a novel solution is provided for real-time deformation monitoring of the solid rocket engine combustion chamber grain.

Description

Technical Field

[0001] This invention belongs to the field of online combustion chamber detection technology, specifically relating to a cold light-based, electricity-free combustion chamber propellant deformation measurement system based on multimode fiber imaging. Background Technology

[0002] In propulsion systems such as solid rocket motors and gas turbines, the deformation of the propellant grain in the combustion chamber directly affects combustion efficiency, structural integrity, and safety. Dynamic deformation of the propellant grain under high temperature and pressure conditions (such as cracking, creep, and interface delamination) can lead to abnormal combustion, pressure fluctuations, or even explosions. Traditional detection methods (such as contact strain gauges and electrical sensors) require external circuitry or metal components, making them difficult to operate stably in flammable combustion environments with strong electromagnetic interference, and they may also interfere with the combustion field distribution, thus exhibiting significant limitations.

[0003] In recent years, non-contact optical detection technologies (such as laser speckle and digital image coherence methods) have been attempted for combustion chamber deformation measurement. However, these technologies rely on external light sources and complex optical paths, are sensitive to environmental interference such as combustion flames and smoke, and have insufficient dynamic resolution. In addition, while existing fiber optic sensing technologies (such as FBG fiber gratings) have electromagnetic interference resistance, they can usually only achieve single-point or sparse multi-point strain measurement, which cannot meet the dynamic imaging requirements of the entire field deformation of the propellant grain.

[0004] Multimode fiber, with its high spatial resolution and modal coupling characteristics, shows potential in the field of distributed sensing. However, traditional multimode fiber imaging systems rely on active electronic control components (such as spatial light modulators) or complex algorithms to demodulate modal noise, making it difficult to achieve stable online measurements in the high-temperature and vibration environment of the combustion chamber. In addition, existing systems mostly require external power supply, which contradicts the safety requirement of a "power-free" combustion chamber.

[0005] In response to this problem, this application proposes a cold light-based, non-electric combustion chamber propellant deformation measurement system based on multimode fiber imaging to solve the aforementioned issues. Summary of the Invention

[0006] The purpose of this invention is to provide a cold light-based, non-electric combustion chamber propellant deformation measurement system based on multimode fiber imaging, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A cold-light, electricity-free combustion chamber propellant column deformation measurement system based on multimode fiber imaging includes:

[0009] A cold light non-electric detection device 1, comprising a left detection element substrate 101 and a right fixed encapsulation substrate 201;

[0010] The cold light non-electric detection device 1 is used to measure the distance change inside the drug column. By changing the extension distance of the test device, the measurement position of the measuring device can be changed, and four deformation values ​​of the coaxial distance of the test object can be measured.

[0011] The left detection element substrate 101 is a hollow thin-walled cylindrical shape with a movable circular pipe 102 in the center for visualizing the test distance and arranging the optical fiber of the device. A calibration algorithm instrument 103 is inserted inside the cylindrical through hole. To the right of the calibration algorithm instrument 103 are four deformation measuring instruments 104 arranged in a ring. To the left of the deformation measuring instruments 104 are installed a binocular stereo recognition camera element 105, a deformation analysis module 106, a multimode fiber optic sensor array 107, and a ring cold light emission module 108.

[0012] The right-side fixed encapsulation base 201 is a high-strength aluminum alloy disc structure with a circular hole of the same diameter as the left structure in the center, and four circular holes at the same position as the object being tested at the center of the radius. A standard threaded connector 202 is provided on the right side of the fixed encapsulation base 201.

[0013] Preferably, the testing method for the system includes the following steps:

[0014] Step 1: Select the distance scale marked on the moving circular pipe 102 of the cold light non-electric detection device 1;

[0015] Step 2: Vertically suspend the cold light non-electric detection device 1 in the object to be tested, and fix the standard threaded connector 202 and the hole on the fixed encapsulation base 201 with a special nut to reduce measurement deformation error;

[0016] Step 3: Set the detection system parameters, start the detection, and ensure the validity of the data by adjusting the system frequency and time;

[0017] Step 4: Record the four displacement distances of the test piece and calculate the average value;

[0018] Step 5: Adjust the moving round pipe 102, repeat steps 2, 3, and 4, collect test data at different positions of the test object, and analyze the displacement changes of the propellant column at different positions.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] This invention provides a breakthrough solution for measuring combustion chamber propellant deformation by integrating multimode fiber imaging with cold light and electricity-free technology. Compared to traditional electrical sensors and existing optical methods, its core advantages are reflected in the following four aspects: First, intrinsic safety and anti-interference capability. Through the electroless design of fluorescent labeling materials and chemical cold light sources, the risk of electric sparks is completely avoided. Combined with the anti-electromagnetic interference characteristics of multimode fiber, it can achieve stable operation in high temperature, high pressure and strong vibration environments. Second, high-precision full-field dynamic imaging. Utilizing the modal scattering characteristics of multimode fiber, it breaks through the limitations of single-point detection and achieves high-resolution, high-frequency sampling of the propellant surface to capture full-field deformation. It simultaneously analyzes multiple parameters such as crack propagation, creep rate and interface peeling, and the data dimension is improved compared with digital image correlation methods. Third, extreme environmental adaptability. It maintains data integrity even under smoke, particulate matter obstruction and flame transients, and its robustness far exceeds that of conventional optical solutions. Fourth, lightweight real-time monitoring. The core of the system only requires a single multimode fiber and a cold light module, which reduces weight and deployment costs compared with distributed FBG networks. It provides a key decision window for combustion control and improves safety by an order of magnitude compared with offline detection. This technology provides a high-performance, low-cost, and highly adaptable innovative approach for the health management of high-energy power plants. Attached Figure Description

[0021] Figure 1 This is a block diagram of a cold light-based, non-electric combustion chamber propellant deformation measurement system based on multimode fiber imaging according to the present invention.

[0022] Among them, 1. Cold light non-electric detection device; 101. Left detection element substrate; 102. Moving round pipe; 103. Calibration algorithm instrument; 104. Deformation measuring instrument; 105. Binocular stereo recognition camera element; 106. Deformation analysis module; 107. Multimode fiber optic sensor array; 108. Ring cold light emission module; 201. Right fixed packaging substrate; 202. Standard threaded connector. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1:

[0025] Please see Figure 1 As shown, a cold-light, electricity-free combustion chamber propellant column deformation measurement system based on multimode fiber imaging includes:

[0026] A cold light non-electric detection device 1, comprising a left detection element substrate 101 and a right fixed encapsulation substrate 201;

[0027] The cold light non-electric detection device 1 is used to measure the distance change inside the drug column. By changing the extension distance of the test device, the measurement position of the measuring device can be changed, and four deformation values ​​of the coaxial distance of the test object can be measured.

[0028] The left detection element substrate 101 is a hollow thin-walled cylindrical shape with a movable circular pipe 102 in the center for visualizing the test distance and arranging the optical fiber of the device. A calibration algorithm instrument 103 is inserted inside the cylindrical through hole. To the right of the calibration algorithm instrument 103 are four deformation measuring instruments 104 arranged in a ring. To the left of the deformation measuring instruments 104 are installed a binocular stereo recognition camera element 105, a deformation analysis module 106, a multimode fiber optic sensor array 107, and a ring cold light emission module 108.

[0029] The right-side fixed encapsulation base 201 is a high-strength aluminum alloy disc structure with a circular hole of the same diameter as the left structure in the center, and four circular holes at the same position as the object being tested at the center of the radius. A standard threaded connector 202 is provided on the right side of the fixed encapsulation base 201.

[0030] A test method for a cold-light, electricity-free combustion chamber propellant column deformation measurement system based on multimode fiber imaging includes the following steps:

[0031] Step 1: Select the distance scale marked on the moving circular pipe 102 of the cold light non-electric detection device 1;

[0032] Step 2: Vertically suspend the cold light non-electric detection device 1 in the object to be tested, and fix the standard threaded connector 202 and the hole on the fixed encapsulation base 201 with a special nut to reduce measurement deformation error;

[0033] Step 3: Set the detection system parameters, start the detection, and ensure the validity of the data by adjusting the system frequency and time;

[0034] Step 4: Record the four displacement distances of the test piece and calculate the average value;

[0035] Step 5: Adjust the moving round pipe 102, repeat steps 2, 3, and 4, collect test data at different positions of the test object, and analyze the displacement changes of the propellant column at different positions.

[0036] As can be seen from the above, the integration of multimode fiber imaging and cold light without electricity provides a breakthrough solution for measuring the deformation of the combustion chamber propellant column. Compared to traditional electrical sensors and existing optical methods, its core advantages are reflected in the following four aspects: First, intrinsic safety and anti-interference capability. Through the electroless design of fluorescent labeling materials and chemical cold light sources, the risk of electric sparks is completely avoided. Combined with the anti-electromagnetic interference characteristics of multimode fiber, it can achieve stable operation in high temperature, high pressure and strong vibration environments. Second, high-precision full-field dynamic imaging. Utilizing the modal scattering characteristics of multimode fiber, it breaks through the limitations of single-point detection and achieves high-resolution, high-frequency sampling of the propellant surface to capture full-field deformation. It simultaneously analyzes multiple parameters such as crack propagation, creep rate and interface peeling, and the data dimension is improved compared with digital image correlation methods. Third, extreme environmental adaptability. It maintains data integrity even under smoke, particulate matter obstruction and flame transients, and its robustness far exceeds that of conventional optical solutions. Fourth, lightweight real-time monitoring. The core of the system only requires a single multimode fiber and a cold light module, which reduces weight and deployment costs compared with distributed FBG networks. It provides a key decision window for combustion control and improves safety by an order of magnitude compared with offline detection. This technology provides a high-performance, low-cost, and highly adaptable innovative approach for the health management of high-energy power plants.

[0037] Example 2:

[0038] I. Experimental Objectives and General Description

[0039] Objective: To verify, under simulated combustion chamber conditions (high temperature, strong vibration, and electromagnetic interference), that the "cold light non-electric detection device" can perform non-electric, non-contact, full-field detection of the deformation (radial / axial displacement) of the propellant at different axial positions, and to compare it with a laser displacement sensor (LDS), providing accuracy, stability, and implementation process.

[0040] System composition:

[0041] Cold light emitting module (ring-shaped cold light emitting module 108)

[0042] Multimode fiber optic sensing array (107) – four-channel ring arrangement (corresponding to “four deformation measuring instruments / four deformation values ​​arranged in a ring” in the claim).

[0043] Deformation analysis module (106) and calibration algorithm instrument (103)

[0044] A binocular stereo recognition camera element (105) is used for remote baseline verification and imaging assistance (the camera module is located outside / far from the measuring device).

[0045] II. Hardware and Experimental Parameters

[0046] Multimode fiber array (107)

[0047] Optical fiber: MMF50 / 125μm (core / cladding); bare silicon fiber segment (temperature-resistant coating removed to improve temperature resistance), length 1.2m (ring arrangement).

[0048] Number of channels: 4 (circular 90° distribution), with an optical detector connected to the end of each channel (the detector is placed outside the remote measurement and processing unit).

[0049] Cold light emitting module (108)

[0050] Type: Chemical cold light fluorescent film (phosphor + electroless chemiluminescent substrate), emission peak wavelength 520nm (green light band, flame retardant background compatible), surface covered on the outside of the propellant column or coated on a small area marking strip (coating thickness 20μm).

[0051] Luminous intensity (nominal): Initial surface radiance 1.0 × 10^3 counts (camera ADC unit, measured by the back-end imaging chain).

[0052] No external power supply required; continuous luminescence time of cold photochemoluminescence (for experimental use) ≥ 8 hours (controllable continuous chemical formulation selected for bench validation).

[0053] Binocular stereo recognition camera (105)

[0054] Resolution: 2048×1080 pixels; Frame rate: 200fps (high frame rate to capture motion); Lens FOV 60°.

[0055] Applications: Calibration, far-field reference, and synchronous capture to verify full-field reconstruction.

[0056] Deformation analysis module (106) / Calibration algorithm instrument (103)

[0057] Operating environment: External workstation (with power) — Executes robust modal decoupling, wavelet denoising and transfer learning models.

[0058] Sampling rate (data reading / decomposition): 1kHz (fiber intensity reading and reconstruction frequency).

[0059] Reference Instruments

[0060] Laser displacement sensor (LDS): Measurement range 0–500 μm, resolution 0.1 μm, used as a reference (not operated in the combustion chamber, only placed in parallel during bench verification).

[0061] III. Calibration Method

[0062] Establish Linear approximation model, each channel is calibrated individually.

[0063] Experimental steps:

[0064] Fix a section of calibration sample (the diameter of the steel rod is similar to that of the drug cartridge), and attach the same cold light fluorescent layer to its surface.

[0065] Using a micrometer-level pusher (1 μm resolution), displacements were applied point by point at known axial displacements of -100, -50, 0, 50, and 100 μm, and the corresponding fiber channel strengths (ADCcounts) were recorded.

[0066] Perform linear regression on each channel: Intensity I = I0 + m·Δd. Obtain the channel sensitivity m (counts / μm) and the baseline intensity I0 (counts).

[0067] The nominal calibration data, specifically the values ​​observed in bench tests, are shown in Table 1 below:

[0068] Table 1:

[0069] Channel Δd (pm) Intensity I (counts) A -100 950 A -50 975 A 0 1000 A 50 1025 A 100 1050

[0070] From the linear fitting in the table above, we get: I0,A = 1000 counts, mA = (1050-950) / 200 = 0.5 counts / μm.

[0071] Other channels:

[0072] mB=0.6counts / μm,I0,B=1000

[0073] mC=0.35counts / μm,I0,C=1000

[0074] mD=0.55counts / μm,I0,D=1000

[0075] formula:

[0076] Δd=(I-I0) / m

[0077] Where I is the intensity during measurement, I0 is the baseline intensity, and m is the channel sensitivity.

[0078] IV. Bench Test Procedure

[0079] Step 1: Select and read the distance scale (reference position) of the moving round pipe (102); record the initial axial installation depth (e.g., 0 mm).

[0080] Step 2: Vertically suspend the cold light non-electric detection device in the test column model, fix and lock it with standard threaded connector (202) to ensure stable operation and reduce mechanical drift.

[0081] Step 3: Set the detection system parameters (sampling rate 1kHz, camera 200fps, wavelet threshold 0.02, modal decoupling iterations 5), start detection and hold for 60 seconds to acquire dynamic data segments. For cold light, since it emits light continuously, the light intensity time sequence is mainly recorded synchronously using a sampling window.

[0082] Step 4: For each sampled frame, calculate the instantaneous displacement of the four channels using the formula Δd=(I-I0) / m; for each position, take the average of N=1000 frames to obtain the steady-state value, and calculate the standard deviation (SD) and confidence interval.

[0083] Step 5: Adjust the moving round pipe (102) to move the detection device along the axis (e.g., three axial positions: 0mm, 50mm, and 100mm), and repeat steps 2 to 4 to obtain displacement distribution curves at different axial positions.

[0084] V. For a single test, the calibration coefficients mentioned above shall be used.

[0085] 5.1 Nominal original measurement, 3 axial positions: Top / Mid / Bottom;

[0086] Top (axial position 0mm): IA=1012, IB=1008, IC=1006, ID=1010 (counts)

[0087] Mid (axial position 50mm): IA=1090, IB=1084, IC=1082, ID=1088

[0088] Bottom (axial position 100mm): IA=1005, IB=1002, IC=998, ID=1004

[0089] (All I0 channel baselines are 1000 counts; mA = 0.5, mB = 0.6, mC = 0.35, mD = 0.55 counts / μm)

[0090] 5.2 Channel-by-channel displacement calculation

[0091] Top:

[0092] ΔdA=(1012-1000) / 0.5=12 / 0.5=24.00μm

[0093] ΔdB=(1008-1000) / 0.6=8 / 0.6=13.333333…μm

[0094] ΔdC=(1006-1000) / 0.35=6 / 0.35=17.142857…μm

[0095] ΔdD=(1010-1000) / 0.55=10 / 0.55=18.181818…μm

[0096] The mean ΔdˉTop=24+13.333333+17.142857+18.1818184=18.1645μm. The standard deviation (sample standard deviation, n=4)≈4.42μm.

[0097] Mid:

[0098] ΔdA=(1090-1000) / 0.5=90 / 0.5=180.00μm

[0099] ΔdB=(1084-1000) / 0.6=84 / 0.6=140.00μm

[0100] ΔdC=(1082-1000) / 0.35=82 / 0.35=234.285714…μm

[0101] ΔdD=(1088-1000) / 0.55=88 / 0.55=160.00μm

[0102] The mean value ΔdˉMid = 178.5714 μm; the sample standard deviation is approximately 40.59 μm.

[0103] Bottom:

[0104] ΔdA=(1005-1000) / 0.5=5 / 0.5=10.00μm

[0105] ΔdB=(1002-1000) / 0.6=2 / 0.6=3.333333…μm

[0106] ΔdC=(998-1000) / 0.35=-2 / 0.35=-5.714286…μm

[0107] ΔdD=(1004-1000) / 0.55=4 / 0.55=7.272727…μm

[0108] The mean ΔdˉBottom = 3.72294 μm; the sample standard deviation ≈ 6.86 μm.

[0109] 5.3 Comparison with the benchmark LDS

[0110] The measurement of the parallel LDS is as follows:

[0111] TopLDS = 17.80 μm

[0112] MidLDS = 175.00 μm

[0113] BottomLDS = 3.20 μm

[0114] Corresponding absolute error:

[0115] Top:|18.1645-17.80|=0.3645μm

[0116] Mid:|178.5714-175.00|=3.5714μm

[0117] Bottom:|3.72294-3.20|=0.52294μm

[0118] Root mean square (RMS) error:

[0119] RMS=0.36452+3.57142+0.5229423≈2.09μm

[0120] As shown above, the overall RMS error of this system is about 2.1 μm in the deformation range of 0–200 μm, and the error is <0.6 μm in the small deformation (<20 μm) scenario. The medium deformation of 180 μm is affected by the consistency of channel sensitivity. The channel difference causes dispersion between channels, and the standard deviation of the mid is 40 μm. This problem can be significantly reduced by more stringent channel consistency calibration weights / temperature drift compensation.

[0121] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A cold-light, electricity-free combustion chamber propellant column deformation measurement system based on multimode fiber imaging, characterized in that, include: A cold light non-electric detection device (1) is provided, comprising a left detection element substrate (101) and a right fixed encapsulation substrate (201); The cold light non-electric detection device (1) is used to measure the distance change inside the drug column. By changing the extension distance of the test device, the measurement position of the measuring device is changed so as to measure the four deformation values ​​of the coaxial distance of the test object. The left detection element substrate (101) is a hollow thin-walled cylinder with a movable circular pipe (102) in the center for testing distance visualization and device fiber optic arrangement. A calibration algorithm instrument (103) is inserted inside the cylindrical through hole. Four deformation measuring instruments (104) are arranged in a ring on the right side of the calibration algorithm instrument (103). The deformation measuring instrument (104) is equipped with a binocular stereo recognition camera element (105), a deformation analysis module (106), a multimode fiber optic sensor array (107), and a ring cold light emission module (108) in sequence on the left side. The right fixed encapsulation base (201) is a high-strength aluminum alloy disc structure with a circular hole of the same diameter as the left structure in the center, and four circular holes at the same position as the object being tested at the center of the radius. A standard threaded connector (202) is provided on the right side of the fixed encapsulation base (201).

2. The test method for a cold light-based, non-electric combustion chamber propellant column deformation measurement system based on multimode fiber imaging according to claim 1, characterized in that, include: Step 1: Select the distance scale marked on the moving round pipe (102) of the cold light non-electric detection device (1); Step 2: Vertically suspend the cold light non-electric detection device (1) in the object to be tested, and fix the holes on the standard threaded connector (202) and the fixed encapsulation base (201) with special nuts to reduce measurement deformation error; Step 3: Set the detection system parameters, start the detection, and ensure the validity of the data by adjusting the system frequency and time; Step 4: Record the four displacement distances of the test piece and calculate the average value; Step 5: Adjust the moving round pipe (102), repeat steps 2, 3, and 4, collect test data at different positions of the test object, and analyze the displacement changes of the catalytic column at different positions.

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