A time-domain modulation-based gunpowder combustion smoke transmittance testing device and method

Abstract

The application discloses a gunpowder combustion smoke transmittance testing device and method based on time domain modulation. In the device, a surface light source is subjected to time domain modulation by a light chopper. In the data processing method, the modulation information of the image gray scale in the time domain is utilized to realize smoke field transmittance testing, and the spatial resolution of the transmittance testing result is ensured. The application is suitable for solid propellant and gunpowder combustion flow field smoke transmittance testing.

Description

Technical Field

[0001] This invention relates to a device and method for testing the smoke transmittance of gunpowder combustion based on time-domain modulation, which is applicable to testing the smoke transmittance distribution of solid propellants and propellants combustion flow fields. Background Technology

[0002] Smoke transmittance is a crucial parameter in the combustion characteristics of propellants and propellant charges. Smoke can interfere with secondary aiming in guidance systems, necessitating evaluation using smoke transmittance. Current propellant combustion diagnostic techniques typically employ light source modulation to reduce the impact of environmental noise on transmittance testing in closed combustion chambers; however, this method suffers from low spatial resolution. Alternatively, a surface light source can be designed with a striped or checkerboard spatial distribution, utilizing the spatial distribution characteristics of the light intensity to reduce stray light and flame effects. This approach, however, sacrifices some spatial resolution of the image sensor in exchange for improved accuracy in transmittance test results. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a time-domain modulated gunpowder combustion smoke transmission rate testing device and method, applicable to the testing of smoke transmission rate and temperature field distribution in the combustion flow field of solid propellants and propellants.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] A time-domain modulated gunpowder combustion smoke transmittance testing device includes a sealed combustion chamber, a surface light source, a chopper, a high-speed camera, and a computer;

[0006] The sealed combustion chamber is equipped with a pair of observation windows;

[0007] The surface light source is located on one side of the observation window of the sealed combustion chamber. The surface light source has high luminous intensity and uniform luminous intensity in the luminous area.

[0008] The chopper is located between the surface light source and the observation window at one end of the sealed combustion chamber;

[0009] The high-speed camera is located on one side of the observation window at the other end of the sealed combustion chamber, opposite to the surface light source, and is connected to a computer.

[0010] The present invention also includes the following technical features:

[0011] Specifically, the pressure adjustment range of the sealed combustion chamber is 0.1-15MPa, and its DC power ignition module can complete the ignition of the test sample.

[0012] Specifically, the emission spectrum of the surface light source includes the response spectrum of the high-speed camera.

[0013] Specifically, the spectral band of the high-speed camera is the near-infrared band or the visible band.

[0014] A method for testing the smoke transmittance of gunpowder combustion based on time-domain modulation, implemented using the aforementioned gunpowder smoke transmittance testing device based on time-domain modulation, includes the following steps:

[0015] Step 1: Weigh the gunpowder test sample, place it in a sealed combustion chamber, adjust the pressure in the sealed combustion chamber to the set value, and connect the ignition power supply.

[0016] Step 2: Adjust the brightness of the surface light source to the highest level, set the modulation frequency f1 of the chopper, and adjust the imaging range of the high-speed camera; set the acquisition frame rate f2 of the high-speed camera to ensure that f2≥4f1;

[0017] Step 3: Use a computer-controlled high-speed camera to start image acquisition, and ignite the test sample in the sealed combustion chamber 1 second later.

[0018] Step 4: After the test sample has finished burning, stop the high-speed camera's image acquisition, save the images acquired by the high-speed camera to the computer, and clean the inside of the sealed combustion chamber and its observation window;

[0019] Step 5: Process the images captured by the high-speed camera:

[0020] Step 5.1, Image preprocessing: Crop the portion outside the light-transmitting window of the chopper from the image sequence to form the image sequence S of the chopper window;

[0021] Step 5.2: For any point in the image, use the temporal modulation features to establish mixed grayscale temporal data G1 and flame grayscale temporal data G2;

[0022] Step 5.2 includes:

[0023] Step 5.2.1: For any point in the image, read the gray-level change time series data G(n) of that point from the image sequence S, where n = 1, 2, 3, ..., N; N is the number of images in the image sequence S;

[0024] Step 5.2.2: Extract mixed grayscale time series data G1 = G(k1 + n*f2 / f1) from G(n), where n = 0, 1, 2, 3, ..., N*f1 / f2; K1 is a constant, and the sequence number is determined by observing the peak value of G(n) at the initial end;

[0025] Step 5.2.3: Extract flame grayscale time series data G2 = G(k1 + n*f2 / f1 + 0.5*f2 / f1) from G(n), where n = 0, 1, 2, 3, ..., N*f1 / f2;

[0026] Step 5.3: Based on the mixed grayscale time series data G1 and the flame grayscale time series data G2, calculate the smoke transmittance τ at this point:

[0027]

[0028] In G1, the average value within the first 1 second is used as the grayscale reference G0, and τ(k1+n*f2 / f1) represents the smoke transmittance of that point in the (k1+n*f2 / f1)th frame image, where n=0,1,2,3…,N*f1 / f2.

[0029] Compared with the prior art, the present invention has the following technical effects:

[0030] (1) The present invention utilizes the fact that the spatial resolution of the smoke field in the processing result is the same as the image resolution of the high-speed camera, and has a high spatial resolution.

[0031] (2) The device of the present invention greatly suppresses the interference of ambient noise light on the smoke transmittance test results by processing the modulation information, and has high accuracy. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the testing device;

[0033] Figure 2 This is a flowchart of test data processing;

[0034] Figure 3 It is a portion of the original image sequence;

[0035] Figure 4 It is the gray-time change curve of a point in an image sequence;

[0036] Figure 5 These are the mixed gray-time curve and the flame gray-time curve for that point in the image sequence;

[0037] Figure 6 It is the transmittance-time curve at a certain point in the test results.

[0038] The meanings of the labels in the diagram are as follows:

[0039] 1-Sealed combustion chamber, 2-Surface light source, 3-Cutter, 4-High-speed camera, 5-Notebook. Detailed Implementation

[0040] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0041] Example 1:

[0042] like Figure 1 As shown, this embodiment provides a gunpowder combustion smoke transmittance testing device based on time-domain modulation, including: a sealed combustion chamber 1, a surface light source 2, a chopper 3, a high-speed camera 4, and a computer 5;

[0043] The sealed combustion chamber 1 is equipped with a pair of observation windows for pressure regulation, sample ignition, exhaust, etc. Specifically, the pressure regulation range of the sealed combustion chamber is 0.1-15MPa, and its DC power ignition module can complete the test sample ignition function.

[0044] The surface light source 2 is located on one side of the observation window of the sealed combustion chamber 1. The surface light source 2 has high luminous intensity and uniform luminous intensity in the luminous area. The main emission spectrum of the surface light source 2 should include the response spectrum of the high-speed camera 4. Specifically, the luminous size of the rectangular surface light source is 200mm×200mm, and it is white.

[0045] The chopper 3 is located between the surface light source 2 and the observation window of the sealed combustion chamber 1; specifically, the chopper is the Model 197 LightChopper from SignalRecovery.

[0046] The high-speed camera 4 is located on one side of the observation window at the other end of the sealed combustion chamber 1, opposite the surface light source 2. The camera 4 is connected to the computer 5. The high-speed camera operates in the near-infrared or visible light spectrum. Specifically, it uses the Photron FASTCAM high-speed camera. The maximum frame rate is 5400 at full resolution.

[0047] Example 2:

[0048] This embodiment provides a method for testing the smoke transmittance of gunpowder combustion based on time-domain modulation, such as... Figure 2 As shown, it includes the following steps:

[0049] Step 1: Weigh the gunpowder test sample, place it in a sealed combustion chamber, adjust the pressure in the sealed combustion chamber to the set value, and connect the ignition power supply.

[0050] Step 2: Adjust the brightness of the surface light source to the maximum, set the modulation frequency f1 of the chopper (in this embodiment, the modulation frequency f1 = 1000), and adjust the imaging range of the high-speed camera; set the acquisition frame rate f2 of the high-speed camera (in this embodiment, the acquisition frame rate f2 = 4000) to ensure that f2 ≥ 4f1;

[0051] Step 3: Use a computer-controlled high-speed camera to start image acquisition, and ignite the test sample in the sealed combustion chamber 1 second later.

[0052] Step 4: After the test sample has finished burning, stop the high-speed camera's image acquisition, save the images acquired by the high-speed camera to the computer, and clean the inside of the sealed combustion chamber and its observation window;

[0053] Step 5: Process the images captured by the high-speed camera:

[0054] Step 5.1, Image preprocessing: Crop the portion outside the light-transmitting window of the chopper from the image sequence to form the image sequence S of the chopper window;

[0055] Step 5.2: For any point in the image, use the temporal modulation features to establish mixed grayscale temporal data G1 and flame grayscale temporal data G2;

[0056] Step 5.2 includes:

[0057] Step 5.2.1: For any point in the image, read the gray-level change time-series data G(n) of that point from the image sequence S, where n = 1, 2, 3, ..., N; (N is the number of images in the image sequence S); for example... Figure 4 As shown.

[0058] Step 5.2.2: Extract the mixed grayscale time series data G1 = G(k1 + n*f2 / f1) from G(n), where n = 0, 1, 2, 3, ..., N*f1 / f2. K1 is a constant, and the sequence number is determined by observing the peak value of G(n) at the initial end;

[0059] Step 5.2.3: Extract the flame grayscale time series data G2 = G(k1 + n*f2 / f1 + 0.5*f2 / f1) from G(n), where n = 0, 1, 2, 3, ..., N*f1 / f2; For example... Figure 5 As shown.

[0060] Step 5.3, as follows Figure 6 As shown, based on the mixed grayscale time series data G1 and the flame grayscale time series data G2, the smoke transmittance τ at this point is calculated:

[0061]

[0062] In G1, the average value within the first 1 second is used as the grayscale reference G0, and τ(k1+n*f2 / f1) represents the smoke transmittance of that point in the (k1+n*f2 / f1)th frame image, where n=0,1,2,3…,N*f1 / f2.

Claims

1. A method for testing the smoke transmittance of gunpowder combustion based on time-domain modulation, characterized in that, This is achieved through a gunpowder combustion smoke transmission rate testing device based on time-domain modulation; the gunpowder combustion smoke transmission rate testing device based on time-domain modulation includes a sealed combustion chamber (1), a surface light source (2), a chopper (3), a high-speed camera (4), and a computer (5). The sealed combustion chamber (1) is equipped with a pair of observation windows; The surface light source (2) is located on one side of the observation window of the sealed combustion chamber (1). The surface light source (2) has high luminous intensity and uniform luminous intensity in the luminous area. The chopper (3) is located between the surface light source (2) and the observation window at one end of the sealed combustion chamber (1); The high-speed camera (4) is located on the other side of the observation window of the sealed combustion chamber (1) opposite to the surface light source (2), and the camera (4) is connected to the computer (5); The pressure adjustment range of the sealed combustion chamber (1) is 0.1-15MPa, and its DC power ignition module can complete the ignition of the test sample. The emission spectrum of the surface light source (2) includes the response spectrum of the high-speed camera (4); The high-speed camera (4) has a spectral band of near-infrared or visible. Includes the following steps: Step 1: Weigh the gunpowder test sample, place it in a sealed combustion chamber, adjust the pressure in the sealed combustion chamber to the set value, and connect the ignition power supply. Step 2: Adjust the brightness of the surface light source to the highest level and set the modulation frequency of the chopper. f 1. Adjust the imaging range of the high-speed camera; set the acquisition frame rate of the high-speed camera. f 2. Guarantee f 2≥4 f 1; Step 3: Use a computer-controlled high-speed camera to start image acquisition, and ignite the test sample in the sealed combustion chamber 1 second later. Step 4: After the test sample has finished burning, stop the high-speed camera's image acquisition, save the images acquired by the high-speed camera to the computer, and clean the inside of the sealed combustion chamber and its observation window; Step 5: Process the images captured by the high-speed camera: Step 5.1, Image preprocessing: Crop the portion outside the light-transmitting window of the chopper from the image sequence to form the image sequence S of the chopper window; Step 5.2: For any point in the image, use the temporal modulation features to establish mixed grayscale temporal data G1 and flame grayscale temporal data G2; Step 5.2 includes: Step 5.2.1: For any point in the image, read the grayscale change time series data of that point from the image sequence S. G ( n ), where n = 1, 2, 3, ..., N; N is the number of images in the image sequence S; Step 5.2.2, from G ( n Extracting mixed grayscale time series data G 1=G ( k 1 +n f 2 / f 1), where n = 0, 1, 2, 3, ..., N f 1 / f 2; k1 is a constant, observed G (n) The peak value at the initial end determines the sequence number; N is the number of images in the image sequence S; f 1 represents the modulation frequency of the chopper; f 2 represents the frame rate of the high-speed camera; Step 5.2.3, from G ( n Extracting flame grayscale time series data G 2=G ( k 1 +n f 2 / f 1+0.5 f 2 / f 1), where n = 0, 1, 2, 3, ..., N f 1 / f 2; N is the number of images in the image sequence S; f 1 represents the modulation frequency of the chopper; f 2 represents the frame rate of the high-speed camera; Step 5.3, based on the mixed grayscale time series data G 1 and flame grayscale time series data G 2. Calculate the smoke transmittance τ at that point: Among them, the average value of G1 in the first 1 second is used as the grayscale reference. G 0, Represents the (k1+n)th The smoke transmittance at this point in the f2 / f1 frame image, where n = 0, 1, 2, 3, ..., N. f 1 / f 2; N is the number of images in the image sequence S; f 1 represents the modulation frequency of the chopper; f 2 represents the frame rate of the high-speed camera.

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