On-vehicle cruise gas leakage monitoring device and monitoring method based on QCLAS

Abstract

The present invention discloses a vehicle-mounted cruise gas leakage monitoring device and monitoring method based on QCLAS, and relates to the field of gas leakage monitoring. The vehicle-mounted cruise gas leakage monitoring method based on QCLAS, when the inspection vehicle is cruising, the laser control module obtains the temperature value at each time point in real time, and performs temperature modulation processing and current wavelength modulation processing respectively, and emits laser after modulation processing; the laser emitted by the laser control module is received by the detector receiving module; the laser emitted by the laser control module received by the detector receiving module is analyzed for gas leakage by the signal processing module. The present invention uses real-time temperature modulation and current wavelength modulation processing, and the monitoring method can quickly and accurately adjust the laser parameters to adapt to environmental changes and the characteristics of the target gas, which not only improves the response speed of the system, but also enhances the measurement accuracy, so that gas leakage can be effectively monitored even under the condition of high-speed vehicle movement.

Description

Technical Field

[0001] This invention relates to the field of gas leak monitoring, specifically to a vehicle-mounted cruise gas leak monitoring device and monitoring method based on QCLAS. Background Technology

[0002] Gas leak monitoring is a crucial area of ​​safety and environmental protection, involving personnel safety, asset protection, and environmental conservation. This is particularly true in sectors such as urban gas, petrochemicals, and gas pipelines, where early detection and timely handling of leaks are essential for preventing accidents and reducing pollution. However, traditional leak monitoring technologies often suffer from low sensitivity, long response times, or the inability to provide real-time monitoring, especially in mobile and expansive outdoor environments.

[0003] Quantum cascade laser absorption spectroscopy (QCLAS) is an advanced spectroscopic analysis technique that has been developed in recent years. It utilizes the characteristics of quantum cascade lasers (QCLs) to generate lasers of specific wavelengths in the mid-infrared region. This characteristic makes QCLAS highly specific and sensitive in detecting the absorption peaks of specific chemical substances, making it very suitable for the detection of gas molecules, such as hydrocarbon gases like methane and ethane.

[0004] The vehicle-mounted cruise gas leak monitoring system utilizes the high sensitivity and specificity of QCLAS. By being installed on a mobile vehicle, it can conduct real-time and continuous gas monitoring on city streets or along pipelines. Compared with traditional fixed monitoring stations or handheld detection devices, this system can cover a wider area, provide more continuous and systematic data, and greatly improve monitoring efficiency and timeliness.

[0005] With the maturation of quantum cascade laser technology and the reduction in cost, the vehicle-mounted cruise gas leak detection method based on QCLAS is expected to be widely used in many fields, especially in situations requiring high sensitivity and large-scale continuous monitoring. This technology can not only improve the efficiency and accuracy of leak detection, but also support intelligent urban management and emergency response systems through timely data analysis and processing.

[0006] In the current technology, most vehicle-mounted cruise gas leak detectors based on laser spectral absorption technology are pump-suction type. Their limitations include at least the following problems: First, pump-suction devices separate the absorption tank and sampling device, requiring a flexible pipe to connect the sampling device, absorption tank, and pump. The longer pipe increases the gas path volume, thus reducing the gas exchange rate of the absorption tank, increasing the device's response speed, and causing a certain degree of lag. Second, the sampling device can only be fixed at a single point on the vehicle, and the air inlet is small, making it difficult to capture leaked gas when the vehicle is traveling at high speed or in strong winds. Third, to improve the device's response speed, a high-flow-rate pump is usually used; however, excessive gas flow can impact the reflector of the absorption tank, resulting in high-frequency optical noise and affecting the device's detection accuracy. Fourth, vehicle-mounted cruise devices are usually powered by a vehicle-mounted mobile power supply; using a high-flow-rate pump significantly increases the device's power consumption and reduces its cruise time. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a vehicle-mounted cruise gas leak monitoring device and method based on QCLAS. It solves several problems associated with pump-suction devices, which require separate absorption tanks and sampling devices, necessitating connections between the sampling device, absorption tank, and air pump via flexible pipes. Longer pipes increase gas path volume, reducing the gas exchange rate of the absorption tank and increasing device response speed, resulting in lag. Furthermore, the sampling device can only be fixed at a single point on the vehicle, and the air inlet is small, making it difficult to capture leaked gas at high speeds or in strong winds. Additionally, while high-flow-rate air pumps are typically used to improve response speed, excessive gas flow can impact the reflector in the absorption tank, causing high-frequency optical noise and affecting detection accuracy. Finally, vehicle-mounted cruise devices are usually powered by a vehicle-mounted mobile power supply; using a high-flow-rate air pump significantly increases device power and reduces cruise time.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a vehicle-mounted cruise gas leak monitoring device based on QCLAS, comprising: a fixed bracket mounted on the front bumper of a patrol vehicle, and a monitoring component mounted on the fixed bracket. The monitoring component includes a laser control module for emitting laser light during patrol vehicle operation. A small open-circuit optical path module is provided on one side wall of the laser control module. One end of the small open-circuit optical path module is connected to a detector receiving module for receiving the laser light emitted by the laser control module during patrol vehicle operation. A signal processing module is provided on one side wall of the detector receiving module for analyzing gas leaks from the laser light emitted by the laser control module received by the detector receiving module during patrol vehicle operation.

[0009] Furthermore, the monitoring component also includes a wireless communication module disposed on one side wall of the laser control module, which is used to send the gas leak analysis results of the signal processing module to the PC tablet terminal inside the inspection vehicle.

[0010] The vehicle-mounted cruise gas leak monitoring method based on QCLAS includes the following steps: During the patrol vehicle's cruise, the laser control module acquires the temperature value at each time point in real time and performs temperature modulation processing respectively; after temperature modulation processing, the wavelength at each time point is subjected to current wavelength modulation processing, and laser is emitted after current wavelength modulation processing; the laser emitted by the laser control module is received by the detector receiving module; the signal processing module performs gas leak analysis on the laser emitted by the laser control module received by the detector receiving module, and sends the analysis results to the PC tablet terminal inside the patrol vehicle.

[0011] Furthermore, the specific steps for temperature modulation processing of the temperature value at each time point are as follows: obtain the preset temperature threshold; perform difference analysis between the temperature value at each time point and the temperature threshold, and input the difference analysis results into the PID modulation model to obtain the modulated temperature value at each time point.

[0012] Furthermore, the specific formula for calculating the modulation temperature value at each time point is as follows:

[0013]

[0014] Where Wz(t) is the modulation temperature value at time t, Wy is the preset temperature threshold, Wd(t) is the temperature value at time t, and K p For proportional gain, K i For integral gain, K d Let t = 1, 2, 3, ..., t0, where t0 is the number of time points acquired.

[0015] Furthermore, the specific steps for performing current wavelength modulation processing on the wavelength at each time point are as follows: obtain the initial wavelength value, the modulation depth of the gas to be analyzed, the first modulation frequency, and the modulation phase; for each time point, perform comprehensive analysis on the initial wavelength value, the modulation depth of the gas to be analyzed, the first modulation frequency, and the modulation phase to obtain the current modulation wavelength value at each time point.

[0016] Furthermore, the specific formula for calculating the current modulation wavelength value at each time point is as follows: λ(t)=λ0+Δλ′*sin(2*π*f1*t+φ); where λ(t) is the current modulation wavelength value at the t-th time point, λ0 is the initial wavelength value, Δλ′ is the modulation depth of the gas to be analyzed, π is pi, f1 is the first modulation frequency of the gas to be analyzed, φ is the modulation phase of the gas to be analyzed, t=1,2,3,…,t0, and t0 is the number of time points obtained.

[0017] Furthermore, the specific steps for analyzing gas leaks using the laser emitted by the laser control module and received by the detector receiving module via the signal processing module are as follows: For each time point, the detector receiving module converts the laser signal emitted by the laser control module into an electrical signal; the signal processing module amplifies and filters the converted electrical signal at each time point, and demodulates it using a lock-in amplifier to obtain the second harmonic signal of the gas to be analyzed at each time point; the second harmonic signal of the gas to be analyzed at each time point is input into the analysis model to obtain the concentration value of the gas to be analyzed at each time point; the concentration value of the gas to be analyzed at each time point is compared with a preset concentration threshold, and if there is a time point where the concentration value of the gas to be analyzed is higher than the preset concentration threshold, it is marked as a gas leak.

[0018] Furthermore, the specific formula for calculating the concentration of the gas to be analyzed at each time point is as follows: V′(t)=A*cos(2*f2*t+θ)*e -2[ε*L*C] Where V′(t) is the amplitude value of the second harmonic signal of the gas to be analyzed at the t-th time point, A is the initial amplitude value, f2 is the second modulation frequency, θ is the phase offset, e is the natural constant, ε is the wavelength absorption coefficient, L is the optical path length, C is the gas concentration, t = 1, 2, 3, ..., t0, and t0 is the number of time points acquired.

[0019] The present invention has the following beneficial effects:

[0020] (1) The vehicle-mounted cruise gas leak monitoring method based on QCLAS can quickly and accurately adjust the laser parameters to adapt to environmental changes and the characteristics of the target gas through real-time temperature modulation and current wavelength modulation processing. This not only improves the system's response speed but also enhances the measurement accuracy, enabling effective monitoring of gas leaks even when the vehicle is moving at high speed.

[0021] (2) The vehicle-mounted cruise gas leak monitoring method based on QCLAS ensures the stability of the laser system during the measurement process by continuously monitoring and dynamically adjusting the laser wavelength, thereby reducing the impact of environmental factors on the monitoring results.

[0022] (3) The vehicle-mounted cruise gas leak monitoring method based on QCLAS can detect the excessive gas concentration in a timely manner by comparing it with the preset concentration threshold, thereby realizing early warning of potential gas leaks. This not only helps to prevent possible safety accidents, such as explosions or fires, but also enables timely emergency response measures to be initiated in emergency situations, effectively reducing possible casualties and property losses.

[0023] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0024] Figure 1 This is a top view of the vehicle-mounted cruise gas leak monitoring device based on QCLAS according to the present invention.

[0025] Figure 2 This is a schematic diagram of the monitoring component structure in the vehicle-mounted cruise gas leak monitoring device based on QCLAS of the present invention.

[0026] Figure 3 This is a schematic diagram illustrating the principle of vehicle-mounted cruise gas leak monitoring based on QCLAS in this invention.

[0027] Figure 4 This is a flowchart of the vehicle-mounted cruise gas leak monitoring method based on QCLAS according to the present invention.

[0028] Figure 5 This is a flowchart illustrating the specific steps involved in temperature modulation processing of the temperature value at each time point in the QCLAS-based vehicle cruise gas leak monitoring method of the present invention. Detailed Implementation

[0029] This application's embodiments, through a vehicle-mounted cruise gas leak monitoring device and method based on QCLAS, solve the problems of pump-suction devices where the absorption pool and sampling device are separated, requiring a flexible pipe to connect the sampling device, absorption pool, and air pump. The longer pipe increases the gas path volume, thereby reducing the gas exchange rate of the absorption pool, increasing the device's response speed, and causing a certain degree of lag. Secondly, the sampling device can only be fixed at a single point on the vehicle, and the air inlet is small, making it difficult to capture leaked gas when the vehicle is traveling at high speed or in strong winds. Furthermore, to improve the device's response speed, a high-flow air pump is usually used; however, excessive gas flow can impact the reflector of the absorption pool, resulting in high-frequency optical noise and affecting the device's detection accuracy. Finally, vehicle-mounted cruise devices typically use a vehicle-mounted mobile power supply; using a high-flow air pump would significantly increase the device's power consumption and reduce its cruise time.

[0030] The problem addressed in this application's embodiments can be summarized as follows:

[0031] During the patrol vehicle's operation, the temperature at each time point is first acquired and modulated in real time. Then, current wavelength modulation is performed to ensure precise adjustment of the laser wavelength, adapting to changes in ambient temperature and the detection requirements of specific gases. After modulation, the laser control module 201 emits a laser, which is captured by the detector receiving module 203 after reflection or scattering. The laser signal received by the detector is converted into an electrical signal, which is then amplified and filtered. A lock-in amplifier is used to demodulate the processed signal, obtaining the second harmonic signal of the gas to be analyzed. These second harmonic signals are input into the analysis model to calculate the gas concentration at each time point, which is then compared with a preset threshold to determine if a gas leak exists.

[0032] Please see Figure 1-3 This invention provides a technical solution: a vehicle-mounted cruise gas leak monitoring device based on QCLAS, comprising: a fixed bracket 1 mounted on the front bumper of a patrol vehicle, and a monitoring component 2 mounted on the fixed bracket 1. The monitoring component 2 includes a laser control module 201 for emitting a specific wavelength laser during patrol vehicle operation. A small open-circuit optical path module 202 is provided on one side wall of the laser control module 201. One end of the small open-circuit optical path module 202 is connected to a detector receiving module 203 for receiving the specific wavelength laser emitted by the laser control module 201 during patrol vehicle operation. A signal processing module 204 is provided on one side wall of the detector receiving module 203 for performing gas leak analysis on the specific wavelength laser emitted by the laser control module 201 received by the detector receiving module 203 during patrol vehicle operation.

[0033] The monitoring component 2 also includes a wireless communication module 205 disposed on one side wall of the laser control module 201. The wireless communication module 205 is used to transmit the gas leak analysis results of the signal processing module 204 to the PC tablet terminal inside the inspection vehicle via WiFi.

[0034] Its working principle is as follows: When the vehicle is cruising, the monitoring component 2 reports the concentrations of methane and ethane in the air along the vehicle's patrol path in real time to a handheld PC tablet terminal inside the vehicle via WiFi. Simultaneously, the data is also sent to a cloud server in real time for remote viewing. The monitoring component 2 consists of a laser control module 201, a small open-circuit optical path module 202, a detector receiving module 203, a signal processing module 204, and a wireless communication module 205. The laser control module 201 drives the QCL (Quantum Cascaded Laser) laser, including temperature control (TEC) and modulation current (LD) control. Temperature control enables… A PID controller is constructed using the MAX1978 chip, which integrates an ultra-low drift chopper-type operational amplifier and an integrator amplifier. By optimizing the proportional, integral, and derivative gain coefficients of the PID parameters, high temperature stability is maintained. The modulation current signal uses a low-frequency sawtooth scanning signal and a high-frequency sinusoidal modulation signal, which are simultaneously applied to the laser drive current using an adder circuit. By modulating the laser wavelength through the current signal, the laser can be scanned within a specific wavelength range. The small open-circuit optical path module 202 is designed with an optical path of 50cm, and a collimating lens assembly is used to adjust the divergence of the light emitted from the laser control module 201. The angle and spot size make the spot at the detector receiving module 203 three times the size of the detector array. The shorter optical path and larger spot size are to ensure that the laser emitted by the monitoring component 2 during the vehicle's high-speed movement can still be received by the detector receiving module 203, thereby improving equipment stability. Simultaneously, a beam shaping element is used to adjust the spot shape, ensuring its energy follows a standard normal distribution to reduce optical interference from the optical path module and improve equipment sensitivity. The generated laser signal is absorbed by the gas medium in the small open-circuit optical path module 202, and then detected by the detector in the detector receiving module 203. The detector used is an InAs / InAsSb mid-infrared detector developed by VIGO. It employs 2TE cooling to control the temperature of the detector receiving module 203 to -40℃ to improve the detector response. The detector converts the optical signal into an electrical signal, which is then amplified and filtered by the signal processing module 204. After demodulation by the lock-in amplifier, the second harmonic signal is obtained. The gas concentration can then be measured based on the relationship between the second harmonic signal and the gas concentration. After calibration, the monitoring component 2 transmits the detected gas concentration to the PC tablet terminal inside the vehicle via WiFi through the wireless communication module 205.

[0035] Another approach is to use a near-infrared light source with multiple reflections to improve detection sensitivity by increasing the absorption optical path. However, the disadvantage is that the multiple reflection spot is a point light source, and slight deformation of the optical path structure in the multiple reflection form can cause a large shift in the optical path, resulting in the system failing to work and having poor stability.

[0036] Please see Figure 4The vehicle-mounted cruise gas leak monitoring method based on QCLAS includes the following steps: During the patrol vehicle's patrol, the laser control module 201 acquires the temperature value at each time point in real time and performs temperature modulation processing respectively; after temperature modulation processing, the wavelength at each time point is subjected to current wavelength modulation processing, and laser is emitted after current wavelength modulation processing; the laser emitted by the laser control module 201 is received by the detector receiving module 203; the signal processing module 204 performs gas leak analysis on the laser emitted by the laser control module 201 received by the detector receiving module 203, and sends the analysis results to the PC tablet terminal inside the patrol vehicle, while notifying relevant personnel.

[0037] Specifically, such as Figure 5 As shown, the specific steps for temperature modulation processing of the temperature value at each time point are as follows: obtain the preset temperature threshold; perform difference analysis between the temperature value at each time point and the temperature threshold, and input the difference analysis results into the PID modulation model to obtain the modulated temperature value at each time point.

[0038] The specific formula for calculating the modulation temperature value at each time point is as follows:

[0039] Where Wz(t) is the modulation temperature value at time t, Wy is the preset temperature threshold, Wd(t) is the temperature value at time t, and K... p For proportional gain, K i For integral gain, K d Let t = 1, 2, 3, ..., t0, where t0 is the number of time points acquired.

[0040] K p K i K d Specifically, this can be obtained through experimental Ziegler-Nichols tuning analysis, which has two main regulation rules:

[0041] Open-loop method: Record the system's open-loop response from steady state to a certain control input (such as a step input), find the response delay time and time constant from the response curve, and then calculate the gain.

[0042] Closed-loop method: Set the proportional gain and derivative gain to 0, increase the integral gain until the system exhibits stable periodic oscillations (critical gain), record the critical oscillation period, and use the critical oscillation to analyze the gain.

[0043] In this implementation scheme, the Ziegler-Nichols tuning method provides a fast and effective means of setting PID controller parameters, especially when deploying new systems or adjusting existing systems. This method allows for rapid achievement of a reasonable control effect without tedious manual adjustments. Rapid parameter setting enables the system to operate stably in a short time, which is particularly important for vehicle systems, as they often operate in changing external environments and need to quickly adapt to new operating conditions. Optimized PID parameters improve the system's dynamic response, enabling more accurate tracking of temperature setpoint changes, thus ensuring laser modulation accuracy. The enhanced system responsiveness not only improves monitoring accuracy but also allows for faster detection of gas leaks. Rapid response is crucial for preventing potential safety incidents. PID parameters adjusted using the Ziegler-Nichols method can effectively reduce system overshoot and oscillation, which is essential for maintaining system stability under constantly changing environmental conditions. System stability directly affects the quality of laser emission and the accuracy of subsequent gas detection. A stable control system ensures reliable gas leak detection even under complex or extreme environmental conditions. Once the PID parameters are effectively set using the Ziegler-Nichols method, daily maintenance needs and adjustment frequency are greatly reduced, lowering long-term operating costs and the overall maintenance burden of the system, making the vehicle-mounted cruise gas leak monitoring system more economical and practical.

[0044] Specifically, the steps for performing current wavelength modulation processing on the wavelength at each time point are as follows: obtain the initial wavelength value, the modulation depth, the first modulation frequency, and the modulation phase of the gas to be analyzed (methane and ethane); for each time point, perform a comprehensive analysis on the initial wavelength value, the modulation depth, the first modulation frequency, and the modulation phase of the gas to be analyzed (methane and ethane) to obtain the current modulation wavelength value at each time point.

[0045] The specific formula for calculating the current modulation wavelength value at each time point is as follows:

[0046] λ(t) = λ0 + Δλ′*sin(2*π*f1*t + φ); where λ(t) is the current modulation wavelength at time t, λ0 is the initial wavelength, which is the wavelength of the laser without modulation and is preset according to the absorption characteristics of the target gas, and Δλ′ is the modulation depth of the gas to be analyzed (methane and ethane), which is the maximum amplitude of wavelength modulation, representing the maximum amount by which the wavelength can deviate from the base wavelength. The modulation depth should be sufficient to cover the main absorption peaks from methane to ethane, while avoiding exceeding this range as much as possible to reduce background noise. In the equation, π is the mathematical constant pi, f1 is the first modulation frequency of the gas to be analyzed (methane and ethane), which determines the rate of wavelength change, i.e., the number of wavelength changes per second. The specific frequency may depend on the response speed of the laser system and the sampling rate of the detection device. For example, it can be set to tens to hundreds of hertz to ensure effective scanning. φ is the modulation phase of the gas to be analyzed (methane and ethane), which determines the starting angle of wavelength modulation and can help synchronize the starting point of wavelength modulation. t = 1, 2, 3, ..., t0, where t0 is the number of time points acquired.

[0047] In this embodiment, the initial wavelength value λ0 is for methane and ethane, since the spectral absorption peaks of methane and ethane are typically located in the mid-infrared region. For example, methane has a significant absorption peak at 3.31 micrometers (λ = 3310 nanometers), while ethane also has a strong absorption peak near 3.35 micrometers. Therefore, a center wavelength that covers both absorption peaks is selected as the initial wavelength.

[0048] The modulation depth determines the range of laser output wavelength variation, which should be sufficient to cover the absorption linewidth of the target gas. Generally, the selected modulation depth is slightly greater than or equal to the full width at half maximum (FWHM) of the gas absorption line. This ensures sufficient scanning across the entire absorption peak, thereby improving measurement accuracy.

[0049] The choice of the first modulation frequency is usually based on the system response time and the required measurement speed: too high a frequency may lead to insufficient system response, while too low a frequency may slow down the measurement speed. In gas concentration measurement, the modulation frequency is usually chosen in the range of tens to hundreds of hertz. This is a compromise that can ensure sufficient system response while maintaining a relatively fast measurement update speed.

[0050] Phase modulation is typically used to optimize signal detection and ensure the separation of the signal from system noise. Adjusting the modulation phase can help distinguish signals from the target gas from background noise, especially in the presence of external disturbances or when multiple gases are mixed. Phase adjustment usually needs to be optimized experimentally in order to find the phase setting that produces the maximum signal contrast.

[0051] The following is a specific example of calculating the current modulation wavelength, given the following data:

[0052] λ0 = 1550 nm;

[0053] △λ'=10nm;

[0054] f1 = 2Hz;

[0055] (i.e., 45°);

[0056] Now, using the above data, we can calculate the current modulation wavelength value at the first time point by substituting the data into the formula.

[0057] In this implementation scheme, through precise control of modulation depth and frequency, the laser can cover the spectral absorption peaks of methane and ethane. This coverage ensures maximum interaction between the laser and gas molecules, thereby improving detection sensitivity and reducing the possibility of false positives or false negatives. Accurately modulated wavelengths maximize the intensity of the absorbed signal, which is particularly important for tracking low-concentration gas leaks. By adjusting the modulation frequency and phase, the system can adapt to different environmental conditions and external interferences, such as temperature fluctuations and mechanical vibrations. This is especially critical in vehicle-mounted systems. Appropriate frequency and phase settings help the system distinguish between true signals and noise, particularly in the environment of high-speed moving inspection vehicles. Optimized modulation phase ensures accurate gas detection even against complex backgrounds, thus avoiding signal errors caused by phase mismatch. Signal distortion and the selection of an appropriate modulation frequency are crucial for ensuring the system can respond quickly to environmental changes and update data promptly. This is essential for real-time gas leak monitoring. A fast response time means that the system can immediately sound an alarm and take appropriate safety measures when a potential leak is detected. Fast and accurate wavelength modulation also means that the system can complete multi-point detection in a short time, improving inspection efficiency. This precise wavelength modulation processing method effectively solves the technical challenge of how to continuously perform high-precision gas monitoring under mobile conditions. Especially in vehicle-mounted systems, it can maintain high-performance monitoring under different environmental conditions and gas concentrations, ensuring the system's wide applicability and reliability. Through this method, early warning of gas leaks in complex environments can be achieved, thereby significantly reducing the safety risks caused by gas leaks.

[0058] Specifically, the specific steps for analyzing gas leaks using the laser emitted by the laser control module 201 and received by the detector receiving module 203 via the signal processing module 204 are as follows: For each time point, the detector receiving module 203 converts the laser signal emitted by the laser control module 201 into an electrical signal; the signal processing module 204 amplifies and filters the converted electrical signal at each time point, and demodulates it based on a lock-in amplifier to obtain the second harmonic signal of the gas to be analyzed (methane and ethane) at each time point; the second harmonic signal of the gas to be analyzed (methane and ethane) at each time point is input into the analysis model to obtain the concentration value of the gas to be analyzed (methane and ethane) at each time point; the concentration value of the gas to be analyzed (methane and ethane) at each time point is compared with a preset concentration threshold, and if there is a time point where the concentration value of the gas to be analyzed (methane and ethane) is higher than the preset concentration threshold, it is marked as a gas leak.

[0059] The specific formula for calculating the concentration of the analyte gas (methane and ethane) at each time point is as follows: V'(t)=A*cos(2*f2*t+θ)*e -2[ε*L*C] Where V'(t) is the amplitude of the second harmonic signal of the gas to be analyzed (methane and ethane) at time point t, A is the initial amplitude, f2 is the second modulation frequency (angular frequency; the selection of the modulation frequency is usually based on the dynamic characteristics of the system and the required response speed. It can be selected according to the natural frequency of the system or through optimization experiments to ensure the stability and fast response of the control system), θ is the phase offset (the phase is usually determined experimentally during the system debugging or initialization phase. In actual operation, the phase needs to be adjusted to achieve the best performance of the system, especially when synchronized with other periodic signals or interference), e is the natural constant, ε is the wavelength absorption coefficient, L is the optical path length (the path length through which the emitted light passes), C is the gas concentration, t = 1, 2, 3, ..., t0, and t0 is the number of time points acquired.

[0060] In this embodiment, the concentrations of methane and ethane gases are measured. Therefore, the wavelength absorption coefficients of methane and ethane gases need to be substituted into the model. Since the amplitude of the second harmonic signal at time point t is known, and all other parameters except for the concentrations of methane and ethane gases are known, the concentrations of methane and ethane gases can be obtained by solving the model.

[0061] Furthermore, the absorption coefficients for methane and ethane gases can be directly found in scientific literature or public databases (such as the HITRAN database).

[0062] In this implementation, the laser emitted by the laser control module is absorbed by the target gases (methane and ethane). The reflected or transmitted light is received by the detector and converted into an electrical signal. The converted electrical signal is amplified and filtered by the signal processing module to enhance signal quality and reduce environmental noise and other interference. Using lock-in amplifier technology, the second harmonic component corresponding to the modulation frequency is extracted from the amplified signal. This step is crucial for improving the signal-to-noise ratio. The obtained second harmonic signal is input into the analysis model to calculate the gas concentration at each time point. Using a specific mathematical model and formula, based on parameters such as the amplitude, absorption coefficient, and optical path length of the second harmonic signal, the methane and ethane concentrations at each time point are calculated. The calculated concentrations are compared with preset safety thresholds. If the concentration exceeds the threshold, a leak is identified, and corresponding marking and alarms are triggered. This method utilizes automated signal processing. The system enables real-time monitoring through analytical models, allowing for rapid identification of leak events and significantly improving response speed and processing efficiency. Utilizing second harmonic generation technology and lock-in amplifier demodulation enhances the accuracy of detection signals and system reliability, reducing the possibility of false alarms and missed alarms, and ensuring the accuracy of monitoring results. By adjusting the modulation frequency and phase, the system can flexibly adapt to different environmental conditions and gas characteristics. This adaptability is particularly important for vehicle-mounted systems, as they often operate in changing environments. By timely and accurately monitoring and identifying gas leaks, the system can effectively prevent potential safety accidents such as explosions or fires, thereby protecting personnel and property safety. It provides high-quality monitoring data, supports data-driven decision-making, and helps operations managers optimize maintenance plans and emergency response strategies. Through effective gas leak monitoring and control, it reduces environmental pollution and complies with environmental standards and regulations.

[0063] In summary, this application has at least the following effects:

[0064] By using real-time temperature modulation and current wavelength modulation, this monitoring method can quickly and accurately adjust laser parameters to adapt to environmental changes and the characteristics of the target gas. This not only improves the system's response speed but also enhances the measurement accuracy, enabling effective monitoring of gas leaks even when the vehicle is moving at high speed.

[0065] By continuously monitoring and dynamically adjusting the laser wavelength, the stability of the laser system during the measurement process is ensured, thereby reducing the impact of environmental factors on the monitoring results.

[0066] By comparing with a preset concentration threshold, this method can detect excessive gas concentrations in a timely manner, thereby enabling early warning of potential gas leaks. This not only helps prevent possible safety accidents, such as explosions or fires, but also enables timely emergency response measures to be initiated in emergency situations, effectively reducing potential casualties and property losses.

[0067] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0068] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. QCLAS-based on-board cruise gas leak monitoring device, including: A fixing bracket (1) arranged on the front bumper of an inspection vehicle, characterized in that it also comprises: A monitoring component (2) is arranged on a fixed bracket (1), the monitoring component (2) comprising a laser control module (201) for emitting laser light when the patrol vehicle is cruising, a small open-circuit optical path module (202) is arranged on a side wall of the laser control module (201), one end of the small open-circuit optical path module (202) is connected to a detector receiving module (203) for receiving laser light emitted by the laser control module (201) when the patrol vehicle is cruising, a signal processing module (204) is arranged on a side wall of the detector receiving module (203), and the signal processing module (204) is used to perform gas leakage analysis on the laser light emitted by the laser control module (201) and received by the detector receiving module (203) when the patrol vehicle is cruising; The vehicle cruise gas leakage monitoring method based on QCLAS includes the following steps: When the inspection vehicle is cruising, the laser control module (201) acquires the temperature value at each time point in real time and performs temperature modulation processing respectively; After the temperature modulation process, the wavelength at each time point is subjected to current wavelength modulation process, and the laser is emitted after the current wavelength modulation process; Receiving laser light emitted by the laser control module (201) through a detector receiving module (203); The laser emitted by the laser control module (201) and received by the detector receiving module (203) is analyzed for gas leakage through the signal processing module (204), and the analysis result is sent to a PC tablet terminal inside the inspection vehicle; The specific steps of performing gas leakage analysis on the laser emitted by the laser control module (201) and received by the detector receiving module (203) through the signal processing module (204) are as follows: At each time point, the detector receiving module (203) converts the received laser signal emitted by the laser control module (201) into an electrical signal; The converted electrical signal at each time point is amplified and filtered by a signal processing module (204), and demodulated based on a phase-locked amplifier to obtain a second harmonic signal of the gas to be analyzed at each time point; Inputting the second harmonic signal of the gas to be analyzed at each time point into the analysis model to obtain the concentration value of the gas to be analyzed at each time point; Compare and analyze the concentration value of the gas to be analyzed at each time point with the preset concentration threshold. If there is a time point at which the concentration value of the gas to be analyzed is higher than the preset concentration threshold, it is marked as a gas leak; The specific formula for calculating the concentration value of the gas to be analyzed at each time point is as follows: V′(t)=A*cos(2*f2*t+θ)e -2[ε*L*C] ; Wherein, V′(t) is the amplitude value of the second harmonic signal of the gas to be analyzed at the t-th time point, A is the initial amplitude value, f2 is the second modulation frequency, θ is the phase offset, e is the natural constant, ε is the wavelength absorption coefficient, L is the optical path length, C is the gas concentration, t=1, 2, 3, …, t0, t0 is the number of acquired time points.

2. The QCLAS-based vehicle-mounted cruise gas leakage monitoring device according to claim 1 is characterized in that: The monitoring component (2) further comprises a wireless communication module (205) arranged on a side wall of the laser control module (201), wherein the wireless communication module (205) is used to send the gas leakage analysis result of the signal processing module (204) to a PC tablet terminal inside the inspection vehicle.

3. The QCLAS-based vehicle cruise gas leakage monitoring device according to claim 1 is characterized in that: The specific steps for temperature modulation processing of the temperature value at each time point are as follows: Get the preset temperature threshold; The temperature value at each time point is subjected to difference analysis with the temperature threshold, and the difference analysis result is input into the PID modulation model to obtain the modulation temperature value at each time point.

4. The QCLAS-based vehicle-mounted cruise gas leakage monitoring device according to claim 3 is characterized in that: The specific formula for calculating the modulation temperature value at each time point is as follows: Where Wz(t) is the modulation temperature value at the tth time point, Wy is the preset temperature threshold, Wd(t) is the temperature value at the tth time point, K p is the proportional gain, K i is the integral gain, K d is the differential gain, t=1, 2, 3, …, t0, t0 is the number of acquired time points.

5. The QCLAS-based vehicle cruise gas leakage monitoring device according to claim 1 is characterized in that: The specific steps of performing current wavelength modulation processing on the wavelength at each time point are as follows: Obtaining the initial wavelength value, the modulation depth, the first modulation frequency, and the modulation phase of the gas to be analyzed; At each time point, the initial wavelength value, the modulation depth of the gas to be analyzed, the first modulation frequency, and the modulation phase are comprehensively analyzed to obtain the current modulation wavelength value at each time point.

6. The QCLAS-based vehicle cruise gas leakage monitoring device according to claim 5 is characterized in that: The specific formula for calculating the current modulation wavelength value at each time point is as follows: λ(t)=λ0+Δλ′*sin(2*π*f1*t+φ); Wherein, λ(t) is the current modulation wavelength value at the t-th time point, λ0 is the initial wavelength value, Δλ′ is the modulation depth of the gas to be analyzed, π is the circumference of a circle, f1 is the first modulation frequency of the gas to be analyzed, φ is the modulation phase of the gas to be analyzed, t=1, 2, 3, …, t0, and t0 is the number of acquired time points.

Images