Gas detection system with high-sensitivity H-type photoacoustic cell
By designing an H-type photoacoustic cell system, using a Porro prism to extend the laser path and combining two sets of cylinder components for multiple gas separations, the problems of large space and low detection accuracy of traditional photoacoustic cell devices are solved, achieving high sensitivity and high accuracy gas detection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DALIAN SHIYOU POWER TECH CO LTD
- Filing Date
- 2025-12-26
- Publication Date
- 2026-05-05
AI Technical Summary
Traditional photoacoustic cell gas detection devices occupy a large space and cannot accurately detect mixed gases after multiple separations, resulting in deviations in the detection results.
Design an H-type photoacoustic cell system, comprising a photoacoustic cell assembly, a first cylinder assembly, and a second cylinder assembly. Utilize a Porro prism to extend the laser path and achieve mixed detection after multiple gas separations through the two cylinder assemblies to ensure detection accuracy.
Achieving high sensitivity and high precision gas detection in a smaller space, resulting in more accurate detection results, and featuring a simple structure and low cost.
Smart Images
Figure CN121978015A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of power equipment testing, and in particular to a gas detection system with a highly sensitive H-type photoacoustic cell. Background Technology
[0002] The insulation condition of high-voltage electrical equipment on locomotives (such as traction transformers and oil-immersed reactors) is crucial for ensuring railway transportation safety. Currently, fault diagnosis by analyzing the characteristic gases dissolved in insulating oil (such as H2, CO, CH4, C2H2, C2H4, and C2H6) has become an industry-recognized and effective method.
[0003] Traditional fault characteristic gas detection processes often employ detection techniques based on photoacoustic spectroscopy, namely photoacoustic cell detection technology. This technology quantifies faults by detecting the acoustic signal generated after a gas absorbs modulated light, and it boasts high selectivity, no consumable parts, and good stability.
[0004] However, this detection method based on photoacoustic spectroscopy achieves higher detection accuracy with a longer laser path. Therefore, to achieve high-precision detection, the photoacoustic cell needs to be made relatively large (long), requiring a significant amount of space. Furthermore, traditional photoacoustic cell fault gas detection devices directly input the primary separated gas from the oil into the photoacoustic cell for detection. However, in reality, the oil can undergo secondary, tertiary, and other separation operations. The content of fault characteristic gases in each separated gas may differ. The traditional method (directly detecting the primary separated gas) has significant deviations and cannot achieve accurate measurement.
[0005] Therefore, a method or apparatus is needed to solve the above problems. Summary of the Invention
[0006] The present invention addresses the aforementioned shortcomings of existing technologies by proposing a gas detection system with a high-sensitivity H-type photoacoustic cell. This system features a simple structure, ingenious design, and reasonable layout, enabling unified detection of mixed gases after multiple separations to ensure accurate detection results. It also boasts a compact size.
[0007] The technical solution of this invention is: a gas detection system with a high-sensitivity H-type photoacoustic cell, characterized in that: the detection system comprises three parts: a photoacoustic cell assembly, a first cylinder assembly, and a second cylinder assembly. The photoacoustic cell assembly includes a housing 1. A first protrusion is provided on side A of the housing 1, and a laser 2 is disposed within the first protrusion. A first lens 3 is positioned in the emission direction of the laser 2. Similarly, a second protrusion is also provided on side A of the housing 1, and a second lens 4, a third lens 5, a reference cell 6, and a pyramid 7 are disposed within the second protrusion. A Porro prism 8 is disposed on side B inside the housing 1. Sides A and B are two opposite sides. The Porro prism 8 can reflect the laser emitted from the laser 2 into the second protrusion. A photoacoustic cell 9 is also disposed in the middle of the housing 1. The first cylinder assembly includes a first stepper motor 10, the working end of which is connected to a first screw 11. A nut seat is threaded onto the first screw 11, and the nut seat is connected to the piston rod in the first cylinder 12. A first exhaust pipe 13 is connected to the top of the first cylinder 12. A solenoid valve 14 and a level switch housing 15 are sequentially arranged on the first exhaust pipe 13. A level sensor is installed inside the level switch housing 15, and an exhaust gas discharge pipe 16 is also provided on the level switch housing 15. The second cylinder assembly includes a second stepper motor 17, the working end of which is connected to a second screw 18. A nut seat is threaded onto the second screw 18, and the nut seat is connected to the piston rod in the second cylinder 19. A second exhaust pipe 20 is connected to the top of the second cylinder 19. The first exhaust pipe 13 and the second exhaust pipe 20 are respectively connected to two passages of the two-position three-way valve 21, and the other passage of the two-position three-way valve 12 is connected to the air intake pipe of the photoacoustic cell assembly. An air intake valve 22 is also provided on the air intake pipe. The first cylinder 12 is connected to an oil passage 23, which is connected to an oil inlet pipe 25 and an oil return pipe 26 via a three-way connector 24. Oil valves are provided on both the oil inlet pipe 25 and the oil return pipe 26.
[0008] The first cylinder assembly also includes a first photoelectric switch 27, a second photoelectric switch 28, and a third photoelectric switch 29. A first trigger plate 30 is provided on the nut seat to trigger the three photoelectric switches respectively. When the piston in the first cylinder 12 is in two extreme positions, the first trigger plate 30 triggers the first photoelectric switch 27 and the third photoelectric switch 29 respectively. When the first cylinder 12 has absorbed a sufficient amount of oil that can be used for detection, the first trigger plate 30 triggers the second photoelectric switch 28.
[0009] The second cylinder assembly also includes a fourth photoelectric switch 31 and a fifth photoelectric switch 32. A second trigger plate 33 is provided on the nut seat, which can trigger the two photoelectric switches respectively. When the piston in the second cylinder 16 is in two extreme positions, the second trigger plate 33 triggers the fourth photoelectric switch 31 and the fifth photoelectric switch 32 respectively.
[0010] Compared with the prior art, the present invention has the following advantages: This gas detection system with a high-sensitivity H-type photoacoustic cell features a simple structure, ingenious design, and rational layout. It addresses the problems of traditional photoacoustic spectroscopy-based detection devices, such as the inability to balance space requirements and detection accuracy, and the inability to accurately obtain mixed gas samples, leading to biased results. A unique structure is designed to address these issues. It includes a laser and a reference cell located on the same side. A Porro prism on opposite sides reflects the laser beam into the reference cell. By superimposing a pyramid, the laser's path is extended fourfold, achieving a longer laser travel distance within a relatively small footprint, thus enabling high-sensitivity and high-precision gas detection. Simultaneously, the photoacoustic cell assembly is equipped with two cylinder assemblies. One cylinder assembly draws in oil and separates the target gas multiple times, while the other cylinder temporarily stores and mixes each separated gas. This means that the final gas sample input to the photoacoustic cell assembly for detection is a mixture of multiple separated gases, resulting in more representative and accurate detection results.
[0011] At the same time, this gas detection system has a simple manufacturing process and low manufacturing cost, so it can be said that it has many advantages and is particularly suitable for promotion and application in this field, with a very broad market prospect. Attached Figure Description
[0012] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the present invention. Detailed Implementation
[0013] Specific embodiments of the present invention will now be described in conjunction with the accompanying drawings. Figure 1 As shown: A gas detection system with a high-sensitivity H-type photoacoustic cell, comprising three parts: a photoacoustic cell assembly, a first cylinder assembly, and a second cylinder assembly. The photoacoustic cell assembly includes a housing 1. A first protrusion is provided on side A of the housing 1, and a laser 2 is disposed within the first protrusion. A first lens 3 is positioned in the emission direction of the laser 2. Similarly, a second protrusion is also provided on side A of the housing 1, and a second lens 4, a third lens 5, a reference cell 6, and a pyramid 7 are disposed within the second protrusion. A Porro prism 8 is disposed on side B inside the housing 1. Sides A and B are two opposite sides. The Porro prism 8 can reflect the laser emitted from the laser 2 into the second protrusion. A photoacoustic cell 9 is also disposed in the middle of the housing 1. The first cylinder assembly includes a first stepper motor 10, the working end of which is connected to a first screw 11. A nut seat is threaded onto the first screw 11, and the nut seat is connected to the piston rod in the first cylinder 12. A first exhaust pipe 13 is connected to the top of the first cylinder 12. A solenoid valve 14 and a level switch housing 15 are sequentially arranged on the first exhaust pipe 13. A level sensor is installed inside the level switch housing 15, and an exhaust gas discharge pipe 16 is also provided on the level switch housing 15. The second cylinder assembly includes a second stepper motor 17, the working end of which is connected to a second screw 18. A nut seat is threaded onto the second screw 18, and the nut seat is connected to the piston rod in the second cylinder 19. A second exhaust pipe 20 is connected to the top of the second cylinder 19. The first exhaust pipe 13 and the second exhaust pipe 20 are respectively connected to two passages of the two-position three-way valve 21, and the other passage of the two-position three-way valve 12 is connected to the air intake pipe of the photoacoustic cell assembly. An air intake valve 22 is also provided on the air intake pipe. The first cylinder 12 is connected to an oil passage 23, which is connected to an oil inlet pipe 25 and an oil return pipe 26 via a three-way connector 24. Oil valves are provided on both the oil inlet pipe 25 and the oil return pipe 26.
[0014] The first cylinder assembly also includes a first photoelectric switch 27, a second photoelectric switch 28, and a third photoelectric switch 29. A first trigger plate 30 is provided on the nut seat to trigger the three photoelectric switches respectively. When the piston in the first cylinder 12 is in two extreme positions, the first trigger plate 30 triggers the first photoelectric switch 27 and the third photoelectric switch 29 respectively. When the first cylinder 12 has absorbed a sufficient amount of oil that can be used for detection, the first trigger plate 30 triggers the second photoelectric switch 28.
[0015] The second cylinder assembly also includes a fourth photoelectric switch 31 and a fifth photoelectric switch 32. A second trigger plate 33 is provided on the nut seat, which can trigger the two photoelectric switches respectively. When the piston in the second cylinder 16 is in two extreme positions, the second trigger plate 33 triggers the fourth photoelectric switch 31 and the fifth photoelectric switch 32 respectively.
[0016] The working process of the gas detection system with a high-sensitivity H-type photoacoustic cell in this invention embodiment is as follows: The first cylinder assembly draws in oil and creates a vacuum environment in its piston chamber, allowing the gas in the oil to separate out. Then, the first cylinder assembly and the second cylinder assembly work together to input the gas separated after one separation operation into the second cylinder assembly. This operation is repeated multiple times, and all the gas after multiple separation operations is input into the second cylinder assembly to form a mixed gas sample. By controlling the valves on each connecting pipeline through the control system, the connecting gas path of the first cylinder assembly is disconnected, and the second cylinder assembly is connected to the photoacoustic cell assembly. The mixed gas sample is then input into the photoacoustic cell assembly. Due to the special structure of the photoacoustic cell assembly, long-stroke laser irradiation can be achieved in a relatively small volume. In other words, the detection accuracy of this photoacoustic cell assembly is higher under the same space requirements.
[0017] First, the control system opens the oil valve on the oil inlet pipe 25 and closes the oil valve on the oil return pipe 26. Then, it controls the first stepper motor 10 to work, driving the first screw 11 to rotate. The movement of the first screw 11 drives the piston rod of the nut seat and the first cylinder 12 to move together, realizing the precise movement of the piston in the first cylinder 12. During the above movement, the first trigger plate 30 connected to the nut seat moves accordingly. When the first trigger plate 30 triggers the second photoelectric switch 28, it indicates that the first cylinder 12 has drawn in enough oil. At this time, the control system closes the oil valve on the oil inlet pipe 25, and the first cylinder assembly stops drawing in oil. Then, the first stepper motor 10 continues to work, and the piston continues to move, creating a vacuum environment in the first cylinder 12. Under the vacuum environment, the gas dissolved in the oil is released and separated from the oil (this is the first separation). When the first trigger plate 30 triggers the third photoelectric switch 29, it indicates that the piston has reached its maximum stroke. The control system controls the first stepper motor 10 to drive the first screw 11 to rotate in the opposite direction, and the piston also moves in the opposite direction, discharging the gas sample separated in the first separation operation through the first exhaust pipe 13 (the solenoid valve 14 on the first exhaust pipe 13 is open). At this time, under the action of the two-position three-way valve 21, the gas sample can directly enter the second cylinder 19 in the second cylinder assembly (the piston in the second cylinder 19 will retract under the action of the control system). The above operation is repeated for the secondary separation, tertiary separation, etc. of the gas in the oil, until the set number of separations is reached and then it stops. At this time, the gas sample in the second cylinder 19 is a mixture of the gases separated multiple times. During the above process, after the gas in the first cylinder 12 is purged, the oil will enter the liquid level switch housing 15 under pressure. When the liquid level sensor is triggered by the oil, the control system issues a command, and the first stepper motor 10 stops working, which can prevent the oil from entering the second cylinder 19. After obtaining the required mixed gas sample, the control system controls the two-position three-way valve 21 to operate, the second cylinder 19 connects with the housing 1 in the photoacoustic cell assembly, and then the second stepper motor 17 operates, the piston in the second cylinder 19 moves, and pushes the mixed gas sample into the housing 1. The working process of the photoacoustic cell assembly is as follows: The laser emitted by the laser 2 passes through the first lens 3 and then shines on the opposite Porro prism 8. Under the reflection of the Porro prism, the light becomes parallel to the initial light but in the opposite direction. After passing through the second lens 4 and the third lens 5, it enters the second protrusion. The inner cavity of the second protrusion is isolated from the inner cavity of the housing 1. It is pre-filled with reference gas. After the light shines on the corner cone 7, it will be reflected by the corner cone, turn 180° and return along the incident direction, and finally return to the first lens 3. That is to say, the light will move back and forth along the "U" shaped trajectory in the housing 1, thereby extending the light path and improving the sensitivity and accuracy of detection. After the mixed gas sample enters the inner cavity of the shell 1, it absorbs light energy and de-excites by releasing heat energy. The released energy causes the surrounding medium to be periodically heated according to the modulation frequency of the light, which in turn causes the medium to produce periodic fluctuations. These pressure fluctuations can be detected by a microphone and amplified to obtain a photoacoustic signal. Then, based on the photoacoustic signal, it can be determined which gas components are contained in the mixed gas sample and the content of these gas components.
[0018] After a test is completed, the first oil draining operation is performed on the first cylinder 12. During the oil draining operation, the solenoid valve 14 is closed, the oil valve on the oil inlet line 25 is closed, and the oil valve on the oil return line 26 is opened. The piston moves forward under the action of the first stepper motor 10, and the residual oil is discharged through the oil return line 26. Then, the exhaust operation is performed. First, the two-position three-way valve 21 is switched to the state where the housing 1 and the first cylinder 12 are connected. The intake valve 22 and the solenoid valve 14 are opened, and all oil valves are closed. The control system controls the first stepper motor 10 to move, driving the piston to move backward in the first cylinder 12. All the residual gas in the housing 1 and each pipeline is sucked into the inner cavity of the first cylinder 12. Then, the gas valve set on the exhaust gas discharge pipeline 16 is opened, and the piston moves in the opposite direction, expelling all the gas in the first cylinder 12 through the exhaust gas discharge pipeline 16, so that the next operation can be performed.
Claims
1. A gas detection system with a high-sensitivity H-type photoacoustic cell, characterized in that: The detection system comprises three parts: a photoacoustic cell assembly, a first cylinder assembly, and a second cylinder assembly. The photoacoustic cell assembly includes a housing (1), a first protrusion is provided on side A of the housing (1), a laser (2) is provided inside the first protrusion, a first lens (3) is provided in the emission direction of the laser (2), a second protrusion is also provided on side A of the housing (1), a second lens (4), a third lens (5), a reference cell (6) and a pyramid (7) are provided inside the second protrusion, a Porro prism (8) is provided on side B inside the housing (1), side A and side B are two opposite sides, and the Porro prism (8) can reflect the laser emitted from the laser (2) into the second protrusion, and a photoacoustic cell (9) is also provided in the middle of the housing (1). The first cylinder assembly includes a first stepper motor (10), the working end of which is connected to a first screw (11). A nut seat is threaded onto the first screw (11), and the nut seat is connected to the piston rod in the first cylinder (12). A first exhaust pipe (13) is connected to the top of the first cylinder (12). A solenoid valve (14) and a liquid level switch housing (15) are sequentially arranged on the first exhaust pipe (13). A liquid level sensor is arranged inside the liquid level switch housing (15), and an exhaust gas discharge pipe (16) with a gas valve is also arranged on the liquid level switch housing (15). The second cylinder assembly includes a second stepper motor (17), the working end of which is connected to a second screw (18), a nut seat is threaded onto the second screw (18), the nut seat is connected to the piston rod in the second cylinder (19), and a second exhaust pipe (20) is connected to the top of the second cylinder (19). The first exhaust pipe (13) and the second exhaust pipe (20) are respectively connected to the two passages of the two-position three-way valve (21), and the other passage of the two-position three-way valve (12) is connected to the air intake pipe of the photoacoustic cell assembly. An air intake valve (22) is also provided on the air intake pipe. The first cylinder (12) is connected to an oil passage (23), which is connected to the oil inlet pipe (25) and the oil return pipe (26) respectively through a three-way connector (24). Oil valves are provided on both the oil inlet pipe (25) and the oil return pipe (26).
2. The gas detection system with a high-sensitivity H-type photoacoustic cell according to claim 1, characterized in that: The first cylinder assembly also includes a first photoelectric switch (27), a second photoelectric switch (28) and a third photoelectric switch (29). A first trigger plate (30) is provided on the nut seat to trigger the three photoelectric switches respectively. When the piston in the first cylinder (12) is in two extreme positions, the first trigger plate (30) triggers the first photoelectric switch (27) and the third photoelectric switch (29) respectively. When the first cylinder (12) has absorbed a sufficient amount of oil that can be used for detection, the first trigger plate (30) triggers the second photoelectric switch (28).
3. The gas detection system with a high-sensitivity H-type photoacoustic cell according to claim 1, characterized in that: The second cylinder assembly also includes a fourth photoelectric switch (31) and a fifth photoelectric switch (32). A second trigger plate (33) is provided on the nut seat to trigger the two photoelectric switches respectively. When the piston in the second cylinder (16) is in two extreme positions respectively, the second trigger plate (33) triggers the fourth photoelectric switch (31) and the fifth photoelectric switch (32) respectively.