System and method for diagnosing dynamic process of cavitation in one-dimensional direction by using rolling shutter camera

Abstract

The application discloses a diagnosis system and method for realizing a dynamic process of a cavity in a one-dimensional direction by using a rolling shutter camera, and the system comprises a laser emission unit, a cavity generation unit, a cavity signal acquisition system and a signal processing unit; the laser emission unit is used for irradiating a cavity generated by the cavity generation unit by using a sheet light source formed by modulating a laser beam emitted by a first laser by a beam modulation element, so that a one-dimensional cavity signal is generated; the cavity generation unit is used for generating a cavity to be measured by irradiating deionized water in a water tank by using a laser beam emitted by a second laser; the cavity signal acquisition unit is used for imaging the generated one-dimensional cavity signal on each row of pixels according to delay time intervals of rolling shutter exposure of each row of pixels; and the signal processing unit is used for converting the received cavity signal, so that a measurement value is obtained after computer processing in a data form. The application can detect the dynamic process of the cavity in the one-dimensional direction, and has the advantages of simple optical structure and low implementation cost.

Description

Technical Field

[0001] This invention relates to the field of gas-liquid two-phase flow measurement, and more specifically to a diagnostic system and method for realizing the one-dimensional dynamic process of cavitation using a rolling shutter camera. Background Technology

[0002] Cavitation and its processes are widespread gas-liquid two-phase flow phenomena in industries such as shipbuilding, energy, power, and machinery. For example, the jet shock waves generated by cavitation and the high-temperature effects are used in pipeline cleaning. Accurate diagnosis of the dynamic processes of cavitation helps people understand the complex mechanisms of gas-liquid two-phase flow, thereby guiding industrial optimization design and manufacturing.

[0003] Researchers have invented and applied several methods for measuring cavitation, which can be mainly divided into beam deflection, high-speed photography, and shadow methods. Traditional beam deflection methods can only measure the evolution of spherically symmetric cavitation shapes, but cannot measure the evolution of 2D asymmetric cavitation shapes. While high-speed photography can perform measurements, its experimental system is complex and expensive, and it requires high repeatability in the generation and development of the object being measured. Although the shadow method has a simple optical path, it requires phase correction, fabrication, and adjustment of optical components in practice, making the actual measurement very complex.

[0004] A rolling shutter camera is a CMOS camera with a rolling shutter mode. The rolling shutter controls the exposure time by rotating the shutter at certain intervals. The exposure time depends on the size of the shutter opening and the speed of the shutter movement. By taking advantage of the fact that each row of pixels in a rolling shutter camera has a very short time interval for acquiring signals, a one-dimensional cavitation image similar to that captured by a high-speed camera can be obtained during a complete full-frame scan of the shutter from top to bottom. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of current cavitation measurement methods being too complex and expensive, and to provide a diagnostic system and method for realizing the one-dimensional dynamic process of cavitation using a rolling shutter camera.

[0006] The technical solution to achieve the purpose of this invention is: a diagnostic system for realizing the one-dimensional dynamic process of cavitation using a rolling shutter camera, comprising four parts: a laser emitting unit, a cavitation generation unit, a cavitation signal acquisition system, and a signal processing unit;

[0007] The laser emitting unit includes a first laser and a beam modulation element. The laser beam emitted by the first laser is modulated into a sheet light source by the beam modulation element to irradiate the cavitation generated by the cavitation generating unit and generate a one-dimensional cavitation signal.

[0008] The cavitation generation unit includes a second laser, and the laser beam emitted by the second laser irradiates the deionized water in the water tank to generate the cavitation to be tested.

[0009] The cavitation signal acquisition unit is used to separate the generated one-dimensional cavitation signal and image it onto each row of pixels according to the delay time interval of each row of pixels during the exposure of the rolling shutter.

[0010] The signal processing unit is used to convert the received cavitation signal into data and process it by a computer to obtain the measurement value.

[0011] Furthermore, the beam modulation element includes a plano-convex cylindrical lens and a plano-concave cylindrical lens, used to modulate the emitted laser beam into a sheet light source.

[0012] Furthermore, the first laser and the second laser are pulsed lasers.

[0013] Furthermore, the cavitation signal acquisition unit includes, in sequence, an imaging lens, a slit aperture, a vertical plano-convex cylindrical lens, and a rolling shutter camera. The imaging lens is provided with a slit aperture to eliminate stray light and control the size of the field of view. The vertically placed plano-convex cylindrical lens is provided with the slit aperture to stretch the imaging width of the cavitation signal on the rolling shutter camera. The rolling shutter camera has a rolling shutter and the exposure mode is linear exposure.

[0014] Furthermore, the signal processing unit includes a computer, which is connected to and synchronously controls the second laser and the rolling shutter camera via a digital pulse delay unit, including controlling the switching of the second laser and the frequency of the pulse light and the rolling shutter camera.

[0015] The present invention also provides a diagnostic method for realizing the one-dimensional dynamic process of cavitation using a rolling shutter camera, based on the system described in the first aspect, the method comprising the following steps:

[0016] The first laser is turned on, and the second laser and the rolling shutter camera are turned on by a computer using a digital pulse delay device. The pulse light generated by the second laser is synchronized with the frequency of the rolling shutter camera.

[0017] The laser beam emitted by the first laser is transmitted through a beam modulation element and illuminates a cross-sectional measurement area of ​​a cavitation bubble generated by the second laser in the water tank in the form of a sheet light source, thereby generating a one-dimensional cavitation bubble signal.

[0018] The one-dimensional cavitation signal passes through the imaging lens and then through the vertical slit aperture to eliminate stray light. After passing through the vertical plano-convex cylindrical lens, it is stretched from a line into a surface.

[0019] One-dimensional cavitation signals are received by a camera operating in rolling shutter mode. Different rows of pixels acquire cavitation signals at the same extremely short delay interval but at different times according to the speed of the rolling shutter and output images to a computer to complete the detection.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention provides a polarized sheet light source by a laser emitting unit, which illuminates the measurement area generated by the cavitation emitting unit to generate a one-dimensional cavitation signal. After the cavitation signal passes through the optical system unit, the pixels of different rows on the rolling shutter camera sensor collect the one-dimensional cavitation signal at different times, thereby collecting multiple sets of one-dimensional cavitation signal data in a period of time at once. After the collected signal is transmitted to the computer and processed, the dynamic change process of the cavitation in a one-dimensional direction in a period of time can be obtained. (2) The experimental optical path of the present invention is simple and convenient to build, the required components are inexpensive, and the dynamic process of the cavitation in a one-dimensional direction can be accurately detected. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the optical path structure of a diagnostic system that utilizes a rolling shutter camera to realize the dynamic process of cavitation in one dimension.

[0022] Figure 2 This is a schematic diagram illustrating the dynamic changes of cavitation in one dimension on the pixel surface of a rolling shutter camera sensor.

[0023] Among them, 1. First laser, 2. Plano-convex cylindrical lens, 3. Plano-concave cylindrical lens, 4. Second laser, 5. Cavitation, 6. Imaging convex lens, 7. Slit stop, 8. Vertical plano-convex cylindrical lens, 9. Rolling shutter camera, 10. Digital time delay, 11. Computer, 12. Second laser, 13. Cavitation, 14. Water tank, 15. Roller shutter on the rolling shutter camera sensor, 16. Imaging image of the rolling shutter camera sensor. Detailed Implementation

[0024] This invention discloses a diagnostic system for the one-dimensional dynamic process of cavitation using a rolling shutter camera. The system includes a laser emitting unit and a cavitation generation unit, comprising a laser 1, a beam modulation element, and a laser 2. The laser beam emitted by laser 1 is modulated into a polarizer light source by the beam modulation element and illuminates the cavitation measurement area generated by laser 2, forming a one-dimensional cavitation signal. The beam modulation element includes a plano-convex cylindrical lens and a plano-concave cylindrical lens. The cavitation signal acquisition unit sequentially includes an imaging lens, a slit aperture, a vertical plano-convex cylindrical lens, and a rolling shutter camera, used to eliminate stray light from the one-dimensional cavitation signal and control... The field of view is adjusted, and the imaging width of the one-dimensional cavitation signal is stretched. The one-dimensional cavitation signal is ultimately received and detected by the sensor of a rolling shutter camera operating in rolling shutter mode. Multiple cavitation signals at different times are sequentially imaged onto different rows of pixels in the camera. The time interval between multiple cavitation signals can be controlled by changing the exposure time of each row of pixels in the rolling shutter camera. The signal processing unit controls the switching of laser 2 and the rolling shutter camera, synchronizing the pulse light of laser 2 with the frequency of the rolling shutter camera, and processes the received cavitation signals as data by a computer to obtain the measurement value. This invention can detect the dynamic process of cavitation in one dimension and has the advantages of simple optical structure and low implementation cost.

[0025] like Figure 1 and Figure 2 As shown, the present invention provides a diagnostic system for realizing the one-dimensional dynamic process of cavitation using a rolling shutter camera, comprising four parts: a laser emitting unit, a cavitation generation unit, a cavitation signal acquisition system, and a signal processing unit;

[0026] The laser emitting unit consists of a laser beam emitted by the first laser, which is modulated into a sheet light source to irradiate the cavitation generated by the cavitation generating unit, thereby generating a one-dimensional cavitation signal.

[0027] The cavitation generation unit generates the cavitation bubbles to be tested by irradiating the deionized water in the water tank with a laser beam emitted by the second laser.

[0028] A cavitation signal acquisition system is used to separate and image the generated one-dimensional cavitation signal onto each row of pixels according to the delay time interval of each row of pixels during the exposure of the rolling shutter.

[0029] The signal processing unit is used to convert the received cavitation signal into data, which is then processed by the computer 11 to obtain the measurement value.

[0030] The present invention also provides a diagnostic method using the above system, comprising the following steps:

[0031] Step 1: Turn on the first laser 1. The laser beam emitted by the first laser passes through the plano-convex cylindrical mirror 2 and the plano-concave cylindrical mirror 3 and is irradiated by the second laser 12 in the water tank 14 as a polarizer light source, forming a one-dimensional cavitation signal.

[0032] Step 2: The one-dimensional cavitation signal is collected by the imaging convex lens 6 and converges and propagates backward. After passing through the vertical slit aperture 7, the size of the field of view is controlled and ambient stray light is filtered out to obtain a clear and stable one-dimensional cavitation signal. Then, it passes through the vertical plano-convex cylindrical lens 8 to stretch the signal from a line to a surface so that it can be imaged on a whole row of pixels. The cavitation signals at different times in the measurement area are imaged separately on different rows of pixels of the rolling shutter camera 9. The interval of the cavitation signals is equal to the delay time of the exposure of each row of pixels by the rolling shutter camera 15. The movement changes of the cavitation in the one-dimensional direction at different times are represented in the camera as the imaging results 16 obtained by different rows of pixels.

[0033] Step 3: Control the laser 2 and the rolling shutter camera 9 through the digital delay unit 10 so that the laser pulse that generates cavitation is synchronized with the frequency of the rolling shutter camera. The data obtained by the camera is processed by the computer 11 to obtain the measurement value.

Claims

1. A diagnostic system for the dynamic process of cavitation in one-dimensional direction using a rolling shutter camera, characterized by, It comprises a laser emitting unit, a cavitation generating unit, a cavitation signal collecting system and a signal processing unit; The laser emitting unit comprises a first laser and a beam modulation element, and the laser beam emitted by the first laser is modulated into a sheet light source by the beam modulation element, which is used for irradiating the cavitation generated by the cavitation generating unit to generate a one-dimensional cavitation signal. The cavitation generating unit comprises a second laser, and the laser beam emitted by the second laser is used for irradiating the deionized water in a water tank to generate the cavitation to be measured. The cavitation signal collecting unit is used for separating the generated one-dimensional cavitation signal into images on each row of pixels according to the delay time interval of the rolling exposure of each row of pixels. The signal processing unit is used for converting the received cavitation signal into a measurement value after computer processing in the form of data.

2. The diagnostic system for realizing a dynamic process of a cavity in one-dimensional direction using a rolling shutter camera according to claim 1, characterized in that, The beam modulation element comprises a plano-convex cylindrical lens and a plano-concave cylindrical lens in sequence, which is used for modulating the outgoing laser beam into a sheet light source. 3.The system for diagnosing dynamic process of cavitation in one-dimensional direction using a rolling shutter camera according to claim 1, wherein, The first laser and the second laser are pulse lasers.

4. The diagnostic system for realizing dynamic process of cavitation in one-dimensional direction using a rolling shutter camera according to claim 1, characterized in that, The cavitation signal collecting unit comprises an imaging lens, a slit diaphragm, a vertical plano-convex cylindrical lens and a rolling shutter camera arranged in sequence, the slit diaphragm is arranged behind the imaging lens and is used for eliminating stray light and controlling the size of the field of view, the vertical plano-convex cylindrical lens is arranged behind the slit diaphragm and is used for stretching the imaging width of the cavitation signal on the rolling shutter camera, and the rolling shutter camera has a rolling shutter and adopts line exposure.

5. The diagnostic system for dynamic process of cavitation in one-dimensional direction using a rolling shutter camera according to claim 1, wherein The signal processing unit comprises a computer, the computer is connected to and synchronously controls the second laser and the rolling shutter camera through a digital pulse delay timer, and includes controlling the switching of the second laser and the frequency of the pulse light and the rolling shutter camera.

6. A diagnostic method for a diagnostic system for realizing a dynamic process of a cavity in one-dimensional direction using a rolling shutter camera according to claim 1, characterized by, The method comprises the following steps: The first laser is turned on, the second laser and the rolling shutter camera are turned on through the computer by using the digital pulse delay timer, and the frequency of the pulse light generated by the second laser is docked and synchronized with the rolling shutter camera; The laser beam emitted by the first laser is irradiated to the cavitation measurement area generated by the second laser in the form of a sheet light source through the beam modulation element to generate a one-dimensional cavitation signal; The one-dimensional cavitation signal is eliminated of stray light through the vertical slit diaphragm after the imaging lens and is stretched from a line to a plane through the vertical plano-convex cylindrical lens; The one-dimensional cavitation signal is received by the camera working in the rolling shutter mode, different rows of pixels collect the cavitation signals with the same extremely short delay interval but at different time points according to the speed of the rolling exposure and output images to the computer to complete detection.

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