Hydrogen flame detection device and hydrogen station

Abstract

[Problem] To make it possible to receive light from a hydrogen flame and accurately detect the hydrogen flame. [Solution] A hydrogen flame detection device 10 comprises a first light reception unit 18 that receives light from a hydrogen flame in a characteristic wavelength band that is specific to hydrogen flames, a second light reception unit 22 that receives light from the hydrogen flame in a wavelength band that is different from the characteristic wavelength band, and a hydrogen flame determination unit 28 that detects the hydrogen flame on the basis of a first light reception signal obtained from the light in the characteristic wavelength band received by the first light reception unit 18 and a second light reception signal obtained from the light in the wavelength band that is different from the characteristic wavelength band received by the second light reception unit 22.

Description

Hydrogen Flame Detection Device and Hydrogen Station

[0001] The present invention relates to a hydrogen flame detection device that receives light from a flame generated by the combustion of hydrogen (hereinafter sometimes referred to as "hydrogen flame") to detect the hydrogen flame, and a hydrogen station equipped with the device.

[0002] In recent years, in order to reduce the environmental impact, there has been an increasing momentum to promote decarbonization. Among them, efforts to replace fossil fuels with hydrogen have also become popular. For example, the development and popularization of fuel cell vehicles (FCVs) using hydrogen instead of gasoline vehicles are progressing. Along with this, it is necessary to develop infrastructure to install hydrogen stations that can supply hydrogen to fuel cell vehicles using hydrogen at various locations.

[0003] Hydrogen stations include hydrogen stations equipped with hydrogen production facilities (onsite hydrogen stations) and hydrogen stations that store hydrogen supplied from another onsite hydrogen station or the like without hydrogen production facilities (offsite hydrogen stations).

[0004] Also, in hydrogen stations, in order to monitor disasters such as hydrogen leakage and fires, the installation of disaster prevention facilities equipped with gas (hydrogen) detection devices, fire detection devices, water spray facilities, etc. is obligatory. Furthermore, in the event of a hydrogen leakage accident, the installation of disaster prevention devices such as emergency shut-off valves and temperature rise prevention devices, and the safety distance from the location where hydrogen is stored to the public road are defined.

[0005] Also, when hydrogen stored in a hydrogen station leaks and is ignited by hydrogen due to some factor such as static electricity and a hydrogen fire occurs, the hydrogen flame of the hydrogen fire is colorless and transparent and difficult to confirm with the naked eye. Therefore, people cannot notice the hydrogen fire early and only notice the occurrence of the fire when it spreads to combustibles near the source of the hydrogen flame.

[0006] For this reason, there are also fire detection devices that detect hydrogen fires using ultraviolet and infrared rays outside the visible range radiated from hydrogen flames.

[0007] Japanese Patent Application Laid-Open No. 2021-010397, Japanese Patent Application Laid-Open No. 2012-066086

[0008] Incidentally, when detecting hydrogen flames based on ultraviolet or infrared radiation, for example, cosmic rays, infrared radiation from high-temperature objects, and the human body can act as disturbances. Therefore, it is necessary to accurately detect the hydrogen flame by distinguishing it from these disturbances, and higher-precision detection of hydrogen flames is desired. Furthermore, hydrogen flames cannot be accurately detected by conventional infrared flame detection devices that detect flames from combustion fires of wood, gasoline, etc.

[0009] The present invention aims to provide a hydrogen flame detection device that can accurately detect a hydrogen flame by receiving light from the hydrogen flame, and a hydrogen station equipped with the device.

[0010] (Hydrogen Flame Detection Device 1) The present invention is a hydrogen flame detection device for detecting a hydrogen flame based on light from a hydrogen flame, and is characterized by comprising: a first light receiving unit that receives light in a characteristic wavelength band specific to a hydrogen flame contained in the light from the hydrogen flame; and a hydrogen flame determination unit that detects a hydrogen flame based on the signal level and frequency characteristics of a first received signal obtained from the light in the characteristic wavelength band received by the first light receiving unit.

[0011] (Light received by the first light receiving unit) The first light receiving unit receives infrared light in a predetermined wavelength band, including wavelengths included in the 1.3 to 1.7 μm wavelength band, as light in the characteristic wavelength band.

[0012] (Frequency range targeted by the frequency characteristics) The hydrogen flame detection unit detects a hydrogen flame based on a frequency characteristic that targets frequencies including 3 to 5 Hz as the frequency characteristics of the first received light signal.

[0013] (Hydrogen flame detection device 2) Another embodiment of the present invention further includes a second light receiving unit that receives light of a wavelength band different from the characteristic wavelength band from the hydrogen flame, and the hydrogen flame determination unit detects the hydrogen flame based on a first light receiving signal obtained from light of a wavelength band different from the characteristic wavelength band received by the second light receiving unit, in addition to a first light receiving signal obtained from light of a characteristic wavelength band received by the first light receiving unit.

[0014] (Light received by the first and second light receiving units) The first light receiving unit receives infrared light in a predetermined wavelength band, including wavelengths included in the 1.3 to 1.7 μm wavelength band, as light in the characteristic wavelength band, and the second light receiving unit receives infrared light in a predetermined wavelength band, including 2.3 μm, as light in a wavelength band different from the characteristic wavelength band.

[0015] (Judgment Condition 1 for Hydrogen Flame Determination) The hydrogen flame determination unit detects a hydrogen flame by determining whether or not it is a hydrogen flame based on the following: a first hydrogen flame determination condition based on the signal level of the first received light signal; a second hydrogen flame determination condition based on the correlation of the signal waveforms of the first received light signal and the second received light signal; and a third hydrogen flame determination condition based on the correlation of the frequency characteristics of the first received light signal and the second received light signal.

[0016] (Details of Judgment Condition 1 for Hydrogen Flame Determination) The hydrogen flame determination unit calculates the integral value of the first received light signal for a predetermined period, and determines that the first hydrogen flame determination condition is satisfied if the integral value of the first received light signal is equal to or greater than a predetermined threshold or exceeds the predetermined threshold. The unit divides the first and second received light signals for a predetermined period into multiple time intervals, calculates the integral values ​​of the first and second received light signals in each time interval, and determines that the second hydrogen flame determination condition is satisfied if all ratios of the integral value of the first received light signal and the integral value of the second received light signal in the same time interval are within a predetermined threshold range. The first and second received signals for a predetermined period are divided into multiple time intervals, a frequency spectrum is generated that includes at least 3 to 5 Hz frequencies of the first and second received signals in each time interval, the integral values ​​of the frequency spectra of the first and second received signals in each time interval are calculated, and it is determined that the third hydrogen flame determination condition is satisfied if all ratios of the integral values ​​of the frequency spectra of the first and second received signals in the same time interval are within a predetermined threshold range.

[0017] (Determination conditions 2 for hydrogen flame determination) The hydrogen flame determination unit detects a hydrogen flame by determining whether or not it is a hydrogen flame based on the following: a first hydrogen flame determination condition based on the signal level of the first received light signal, a second hydrogen flame determination condition based on the signal levels of the first and second received light signals, and a third hydrogen flame determination condition based on the frequency characteristics of the first received light signal.

[0018] (Details of the second determination condition for hydrogen flame determination) The hydrogen flame determination unit calculates the integral value of the first received light signal for a predetermined period, and determines that the first hydrogen flame determination condition is satisfied if the integral value of the first received light signal is equal to or greater than a predetermined threshold or exceeds the predetermined threshold. The unit calculates the integral values ​​of the first and second received light signals for a predetermined period, and determines that the second hydrogen flame determination condition is satisfied if the ratio of the integral value of the first received light signal to the integral value of the second received light signal satisfies a predetermined threshold condition. The unit generates a frequency spectrum that includes at least 3 to 5 Hz frequencies of the first received light signal for a predetermined period, divides the frequency spectrum into a low-frequency spectrum including 3 to 5 Hz and a high-frequency spectrum, calculates the integral values ​​of the low-frequency spectrum and the high-frequency spectrum, and determines that the third hydrogen flame determination condition is satisfied if the ratio of the integral value of the low-frequency spectrum to the integral value of the high-frequency spectrum satisfies a predetermined threshold condition.

[0019] (Hydrogen flame determination 1) The hydrogen flame determination unit determines that it is a hydrogen flame and detects it if all of the first to third hydrogen flame determination conditions are met.

[0020] (Hydrogen flame determination 2) The hydrogen flame determination unit determines that a hydrogen flame is present and detects it when all of the first to third hydrogen flame determination conditions are met, and the number of times at least one of the first to third hydrogen flame determination conditions has been met reaches a predetermined number of accumulations.

[0021] (Hydrogen Station) Another embodiment of the present invention is a hydrogen station equipped with the hydrogen flame detection device described above, characterized in that the hydrogen flame detection device is installed so as to include an area in which hydrogen leakage may occur within the monitoring area.

[0022] (Effects of Hydrogen Flame Detection Device 1) The present invention is a hydrogen flame detection device that detects a hydrogen flame based on light from a hydrogen flame, comprising: a first light receiving unit that receives light in a characteristic wavelength band specific to hydrogen flames contained in the light from the hydrogen flame; and a hydrogen flame determination unit that detects a hydrogen flame based on the signal level and frequency characteristics of a first received signal obtained from the light in the characteristic wavelength band received by the first light receiving unit. Specifically, the first light receiving unit receives infrared light in a predetermined wavelength band including wavelengths contained in the 1.3 to 1.7 μm wavelength band as the light in the characteristic wavelength band, and the hydrogen flame determination unit detects a hydrogen flame based on frequency characteristics targeting frequencies including 3 to 5 Hz as the frequency characteristics of the first received signal. This enables detection based on both light in a characteristic wavelength band specific to hydrogen flames and fluctuation frequencies specific to hydrogen flames, thereby enabling highly accurate detection of hydrogen flames.

[0023] (Effects of the Hydrogen Flame Detection Device 2) Another embodiment of the present invention further includes a second light receiving unit that receives light of a wavelength band different from the characteristic wavelength band from the hydrogen flame. The hydrogen flame determination unit detects the hydrogen flame based on a first light receiving signal obtained from light of a wavelength band different from the characteristic wavelength band received by the first light receiving unit, as well as a second light receiving signal obtained from light of a wavelength band different from the characteristic wavelength band received by the second light receiving unit. Specifically, the first light receiving unit receives infrared light of a predetermined wavelength band including wavelengths in the 1.3 to 1.7 μm wavelength band as the light of the characteristic wavelength band, and the second light receiving unit receives infrared light of a predetermined wavelength band including 2.3 μm as the light of a wavelength band different from the characteristic wavelength band. This enables detection based on two different wavelengths, making it possible to detect the hydrogen flame with high accuracy.

[0024] (Effect of Judgment Condition 1 for Hydrogen Flame Determination) The hydrogen flame determination unit also detects a hydrogen flame by determining whether or not it is a hydrogen flame based on a first hydrogen flame determination condition based on the signal level of the first received signal, a second hydrogen flame determination condition based on the correlation of the signal waveforms of the first received signal and the second received signal, and a third hydrogen flame determination condition based on the correlation of the frequency characteristics of the first received signal and the second received signal. Specifically, the hydrogen flame determination unit calculates the integral value of the first received signal for a predetermined period, determines that the first hydrogen flame determination condition is satisfied when the integral value of the first received signal is equal to or greater than a predetermined threshold or exceeds the predetermined threshold, divides the first and second received signals for a predetermined period into multiple time intervals, calculates the integral value of the first and second received signals in each time interval, and calculates the integral value of the first and second received signals in the same time interval The system determines that the second hydrogen flame determination condition is satisfied when all ratios are within a predetermined threshold range. The first and second received signals for a predetermined period are divided into multiple time intervals, and frequency spectra are generated for each time interval that include frequencies of at least 3 to 5 Hz from the first and second received signals. The integral values ​​of the frequency spectra of the first and second received signals in each time interval are calculated, and the third hydrogen flame determination condition is determined to be satisfied when all ratios of the integral values ​​of the frequency spectra of the first and second received signals in the same time interval are within a predetermined threshold range. As a result, the system determines whether or not a flame is a hydrogen flame based on multiple hydrogen flame determination conditions, thereby improving the accuracy of hydrogen flame detection.

[0025] Furthermore, the same effect as that of the first criterion for determining a hydrogen flame can be obtained with criterion 2 for determining a hydrogen flame.

[0026] (Effects of Hydrogen Flame Judgment 1) Furthermore, the hydrogen flame judgment unit is configured to detect a hydrogen flame when all of the first to third hydrogen flame judgment conditions are met, thus the conditions for determining a hydrogen flame are strict, making it possible to further improve the accuracy of hydrogen flame detection.

[0027] (Effects of Hydrogen Flame Judgment 2) Furthermore, the hydrogen flame judgment unit detects a hydrogen flame when all of the first to third hydrogen flame judgment conditions are satisfied, and the number of times at least one of the first to third hydrogen flame judgment conditions has been satisfied reaches a predetermined number of accumulated occurrences. As a result, the conditions for judging something as a hydrogen flame are even stricter than those for hydrogen flame judgment 1, making it possible to further improve the accuracy of hydrogen flame detection.

[0028] This is an explanatory diagram showing an example of a hydrogen station. This is an explanatory diagram showing an example of a hydrogen flame detection device. This is an explanatory diagram showing the emission intensity distribution (wavelength spectrum) of a hydrogen flame. This is an explanatory diagram showing the observed values ​​when infrared radiation is received from a hydrogen flame. This is an explanatory diagram showing the frequency spectrum of the received signal when light is received from a hydrogen flame. This is a flowchart showing an example of hydrogen flame detection processing using the hydrogen flame judgment of the first embodiment. This is a flowchart showing an example of hydrogen flame detection processing using the hydrogen flame judgment of the second embodiment.

[0029] [Basic Concepts of the Embodiment] First, the basic concepts of the embodiment will be explained. The embodiment generally relates to a hydrogen flame detection device that detects a hydrogen flame based on light from a hydrogen flame, and a hydrogen station equipped with the hydrogen flame detection device, in which the hydrogen flame detection device is installed so as to include an area where hydrogen leakage may occur in the monitoring area.

[0030] Here, the "monitoring area" is the area where a hydrogen flame generated by the combustion of hydrogen is detected and monitored by a hydrogen flame detection device. It is an outdoor, semi-outdoor, or indoor space of a certain size, and is a concept that includes predetermined areas where hydrogen leaks may occur, such as dispensers (hydrogen supply units) installed in hydrogen stations that supply hydrogen gas to fuel cell vehicles, hydrogen production facilities, and storage facilities. Furthermore, "detecting and monitoring hydrogen flames" is a concept that includes detecting hydrogen flames and monitoring hydrogen fires accompanied by hydrogen flames.

[0031] "Light" is a concept that includes the wavelength ranges (wavelength bands, wavelength spectrums) of ultraviolet, visible, and infrared light, and "luminescence" refers to the emission of light. "Flame" is a flame that accompanies combustion and is a concept that includes combustion products accompanied by luminescence. A "hydrogen flame" emits almost no light in the visible region and is difficult to observe with the naked eye. The spectral spectrum of light emitted from a hydrogen flame has characteristic peaks in the ultraviolet wavelength band of approximately 278-320 nm, approximately 925-1000 nm, approximately 1.3-1.7 μm, and the infrared wavelength band of approximately 1.8 μm-2.1 μm.

[0032] The term "hydrogen flame detection device" includes, for example, a device that detects a hydrogen flame based on light in a characteristic wavelength band specific to hydrogen flames (hydrogen flame detection device 1), and a device that detects a hydrogen flame based on two wavelengths of light: light in a characteristic wavelength band specific to hydrogen flames and light in a different wavelength band than the characteristic wavelength band emitted from the hydrogen flame (hydrogen flame detection device 2). It is a concept that includes devices that can be treated as equivalent in terms of their functions, such as "hydrogen flame detector," "hydrogen flame sensor," and "hydrogen fire detection device."

[0033] The "hydrogen flame detection device 1" comprises a "first light receiving unit" and a "hydrogen flame determination unit." The "first light receiving unit" in the hydrogen flame detection device 1 is a light receiving unit that receives light in characteristic wavelength bands specific to hydrogen flames contained in the light from the hydrogen flame, such as ultraviolet light of approximately 278 to 320 nm, infrared light of approximately 925 to 1000 nm, approximately 1.3 to 1.7 μm, and approximately 1.8 μm to 2.1 μm, which have relatively high emission intensity in hydrogen flames as described above. In particular, the light receiving unit is intended to receive infrared light in a predetermined wavelength band that includes wavelengths included in the 1.3 to 1.7 μm wavelength band.

[0034] The "hydrogen flame determination unit" in the hydrogen flame detection device 1 detects a hydrogen flame based on the signal level and frequency characteristics of the first received light signal obtained from light in a characteristic wavelength band received by the first light receiving unit. Furthermore, since the "first received light signal" is a received light signal corresponding to light in a characteristic wavelength band that has a relatively high emission intensity in a hydrogen flame, when the first light receiving unit receives light in the characteristic wavelength band from a hydrogen flame, its signal level increases in proportion to the emission intensity, and it also has a frequency characteristic that contains many frequency components in the 3-5 Hz range, which corresponds to the fluctuation frequency of a hydrogen flame. Therefore, the "hydrogen flame determination unit" can detect a hydrogen flame by capturing these characteristics from the signal level and frequency characteristics of the first received light signal.

[0035] The "hydrogen flame detection device 2" comprises a "first light receiving unit," a "second light receiving unit," and a "hydrogen flame determination unit." The "first light receiving unit" in the hydrogen flame detection device 2 is the same as that of the hydrogen flame detection device 1, and is a light receiving unit that receives light in characteristic wavelength bands specific to hydrogen flames contained in the light from the hydrogen flame, such as ultraviolet light of approximately 278 to 320 nm, infrared light of approximately 925 to 1000 nm, approximately 1.3 to 1.7 μm, and approximately 1.8 μm to 2.1 μm, which have relatively high emission intensity in hydrogen flames as described above. In particular, the light receiving unit is intended to receive infrared light in a predetermined wavelength band that includes wavelengths included in the 1.3 to 1.7 μm wavelength band.

[0036] The "second light receiving unit" in the hydrogen flame detection device 2 is a light receiving unit that receives light in wavelength bands different from the characteristic wavelength band from the hydrogen flame, such as ultraviolet light of approximately 278 to 320 nm, which has a relatively high emission intensity in the hydrogen flame, and light other than infrared light of approximately 925 to 1000 nm, approximately 1.3 to 1.7 μm, and approximately 1.8 μm to 2.1 μm, in particular infrared light in a predetermined wavelength band including 2.3 μm. Here, "infrared light in a predetermined wavelength band including 2.3 μm" is infrared light in a wavelength band that has been used in conventional fire detectors, etc., and it is possible to reuse the configuration of conventional fire detectors in the hydrogen flame detection device.

[0037] The "hydrogen flame determination unit" in the hydrogen flame detection device 2 detects a hydrogen flame based on a first light-receiving signal obtained from light in a characteristic wavelength band received by the first light-receiving unit and a second light-receiving signal obtained from light in a wavelength band different from the characteristic wavelength band received by the second light-receiving unit.

[0038] Furthermore, the "hydrogen flame determination unit" in the hydrogen flame detection device 2 determines whether or not a hydrogen flame is present based on the first and second light-receiving signals, using two patterns, for example, hydrogen flame determination 1 (first embodiment of hydrogen flame determination) and hydrogen flame determination 2 (second embodiment of hydrogen flame determination).

[0039] In hydrogen flame determination 1, the determination of whether or not it is a hydrogen flame is made based on three determination conditions: a "first hydrogen flame determination condition" based on the signal level of the first received signal, a "second hydrogen flame determination condition" based on the correlation of the signal waveforms of the first and second received signals, and a "third hydrogen flame determination condition" based on the correlation of the frequency characteristics of the first and second received signals.

[0040] In the "First Hydrogen Flame Judgment Condition" of Hydrogen Flame Judgment 1, when the first light receiving unit receives light from the hydrogen flame, the signal level of the first received signal increases in accordance with the characteristic wavelength band where the emission intensity is relatively high. In the "Second Hydrogen Flame Judgment Condition" and the "Third Hydrogen Flame Judgment Condition," when the first and second light receiving units receive light from the hydrogen flame, although there is a difference in the signal levels of the first and second received signals, both the first and second received signals have frequency characteristics that contain many frequency components in the 3-5 Hz range corresponding to the fluctuation frequency of the hydrogen flame, and the signal waveforms and frequency characteristics of the "First Received Signal" and the "Second Received Signal" are highly correlated.

[0041] Here, the conditions set for the first to third hydrogen flame determination conditions of hydrogen flame determination 1 are arbitrary, and the "first hydrogen flame determination condition" based on the signal level of the first received light signal includes, for example, a condition in which the integral value of the first received light signal for a predetermined period is calculated, and the condition is determined to be satisfied when the integral value of the first received light signal is equal to or greater than a predetermined threshold or exceeds that predetermined threshold.

[0042] The "second hydrogen flame determination condition" based on the correlation of the signal waveforms of the first received light signal and the second received light signal is, for example, to divide the first received light signal and the second received light signal for a predetermined period into a plurality of time intervals, calculate the integrated values of the first received light signal and the second received light signal in each time interval, and determine that it is satisfied when all of the ratios of the integrated value of the first received light signal and the integrated value of the second received light signal in the same time interval are within a predetermined threshold range.

[0043] The "third hydrogen flame determination condition" based on the correlation of the frequency characteristics of the first received light signal and the second received light signal is, for example, to divide the first received light signal and the second received light signal for a predetermined period into a plurality of time intervals, generate a frequency spectrum including at least frequencies of 3 to 5 Hz for the first received light signal and the second received light signal in each time interval, calculate the integrated values of the frequency spectrum of the first received light signal and the frequency spectrum of the second received light signal in each time interval, and determine that it is satisfied when all of the ratios of the integrated value of the frequency spectrum of the first received light signal and the integrated value of the frequency spectrum of the second received light signal in the same time interval are within a predetermined threshold range. Note that the frequencies targeted for the frequency spectrum are arbitrary as long as the frequencies of 3 to 5 Hz are included, and for example, those targeting frequencies of 1 to 16 Hz are included.

[0044] In the hydrogen flame determination 2, it is determined whether it is a hydrogen flame based on three determination conditions: the "first hydrogen flame determination condition" based on the signal level of the first received light signal, the "second hydrogen flame determination condition" based on the signal levels of the first received light signal and the second received light signal, and the "third hydrogen flame determination condition" based on the frequency characteristics of the first received light signal.

[0045] In hydrogen flame determination 2, the "first hydrogen flame determination condition" utilizes the fact that, similar to hydrogen flame determination 1, when the first light receiving unit receives light from a hydrogen flame, the signal level of the first received signal increases in accordance with the characteristic wavelength band with relatively high emission intensity. The "second hydrogen flame determination condition" utilizes the fact that when both the first and second light receiving units receive light from a hydrogen flame, the signal level of the first received signal increases relative to the signal level of the second received signal. The "third hydrogen flame determination condition" utilizes the fact that when the first light receiving unit receives light from a hydrogen flame, the first received signal contains many frequency components in the 3-5 Hz range corresponding to the fluctuation frequency of the hydrogen flame, and also has a frequency characteristic that contains more frequency components on the lower frequency side than on the higher frequency side.

[0046] Here, the conditions set for the first to third hydrogen flame determination conditions of hydrogen flame determination 2 are arbitrary, and the "first hydrogen flame determination condition" based on the signal level of the first received light signal includes, similar to hydrogen flame determination 1, a condition in which, for example, the integral value of the first received light signal for a predetermined period is calculated, and the condition is determined to be satisfied when the integral value of the first received light signal is equal to or greater than a predetermined threshold or exceeds that predetermined threshold.

[0047] The "second hydrogen flame determination conditions," based on the signal levels of the first and second received light signals, include, for example, a condition in which the integral values ​​of the first and second received light signals for a predetermined period are calculated, and the condition is determined to be satisfied when the ratio of the integral value of the first received light signal to the integral value of the second received light signal satisfies a predetermined threshold condition.

[0048] The "third hydrogen flame determination condition" based on the correlation of the frequency characteristics of the first received optical signal is, for example, to generate the frequency spectrum of the first received optical signal for a predetermined period, divide the frequency spectrum into a low-frequency spectrum including 3 to 5 Hz and a high-frequency spectrum, calculate the integrated values of the low-frequency spectrum and the high-frequency spectrum, and determine that the condition is satisfied when the ratio of the integrated value of the low-frequency spectrum to the integrated value of the high-frequency spectrum meets a predetermined threshold condition. Note that the frequency targeted for the frequency spectrum is arbitrary as long as the frequency of 3 to 5 Hz is included in the target. For example, the frequency spectrum is generated for frequencies of 1 to 16 Hz, and the frequency spectrum targeted for 1 to 8 Hz is used as the low-frequency spectrum, and the frequency spectrum targeted for 8 to 16 Hz is used as the high-frequency spectrum.

[0049] And the "hydrogen flame determination unit" basically determines that it is a hydrogen flame and detects a hydrogen flame when all of the first to third hydrogen flame determination conditions are satisfied in both hydrogen flame determination 1 and hydrogen flame determination 2. However, in addition to the satisfaction of the first to third hydrogen flame determination conditions, it may also determine that it is a hydrogen flame and detect a hydrogen flame on the condition that the number of times any of the first to third hydrogen flame determination conditions is satisfied reaches a predetermined accumulation number.

[0050] Also, the hydrogen flame determination condition for which the condition that the number of times satisfied reaches the accumulation number is arbitrary, and it may be one, two, or three of the three conditions of the first to third hydrogen flame determination conditions.

[0051] Hereinafter, specific embodiments will be described. In the specific embodiments shown below, the hydrogen flame detection device is a "hydrogen flame detection device installed in a hydrogen station and including a first light receiving unit, a second light receiving unit, and a hydrogen flame determination unit", the "monitoring area" is "inside the hydrogen station", the "first light receiving unit" is a "light receiving unit that receives infrared rays in a narrow wavelength band centered on a central wavelength of 1.5 μm", the "second light receiving unit" is a "light receiving unit that receives infrared rays in a narrow wavelength band centered on a central wavelength of 2.3 μm", and the hydrogen flame determination by the "hydrogen flame determination unit" will be described separately in the first embodiment and the second embodiment.

[0052] [Specific Details of the Embodiments] Embodiments of the hydrogen flame detection device and hydrogen station will be described in the following sections: a. Hydrogen Station b. Hydrogen Flame Detection Device b1. Overall Configuration of the Hydrogen Flame Detection Device b2. First Light Receiving Unit b3. Second Light Receiving Unit b4. Control Unit c. First Embodiment of Hydrogen Flame Judgment c1. First Hydrogen Flame Judgment Condition c2. Second Hydrogen Flame Judgment Condition c3. Third Hydrogen Flame Judgment Condition c4. Hydrogen Flame Detection d. Hydrogen Flame Detection Process Using the Hydrogen Flame Judgment of the First Embodiment e. Second Embodiment of Hydrogen Flame Judgment e1. First Hydrogen Flame Judgment Condition e2. Second Hydrogen Flame Judgment Condition e3. Third Hydrogen Flame Judgment Condition e4. Hydrogen Flame Detection f. Hydrogen Flame Detection Process Using the Hydrogen Flame Judgment of the Second Embodiment g. Modifications of the Invention

[0053] [a. Hydrogen Station] First, we will describe a hydrogen station equipped with a hydrogen flame detection device. In this description, please refer to Figure 1, which shows an example of a hydrogen station. Figure 1(A) shows a top view, and Figure 1(B) shows a front view.

[0054] As shown in Figure 1, the hydrogen station 100 is an example of an on-site hydrogen station equipped with a hydrogen production area 104. Within the site, which is surrounded on three sides by firewalls 102 except for the part facing the road (the lower side in Figure 1(A)), two dispensers 112 for supplying hydrogen to vehicles 124 are installed.

[0055] The hydrogen production area 104 is equipped with a raw fuel tank 105, a hydrogen production facility 106, a compressor 108, and a storage facility 110. The raw fuel tank 105 is installed, for example, underground and stores the raw fuel injected from the inlet 1050, supplying the stored raw fuel to the hydrogen production facility 106. The hydrogen production facility 106 takes in the raw fuel from the raw fuel tank 105 and generates hydrogen (hydrogen gas). The generated hydrogen is compressed to a predetermined pressure by the compressor 108 and stored in the storage facility 110. The storage facility 110 sends the stored hydrogen to the dispenser 112, enabling the supply of hydrogen from the dispenser 112 to the vehicle (fuel cell vehicle) 124 by, for example, 70 MPa differential pressure filling. In Figure 1, the inlet 1050 is located outside the hydrogen production area 104, but it may also be located inside the hydrogen production area 104.

[0056] Furthermore, a roof 115 is installed over a predetermined area including the location where the dispenser 112 is installed, so that rainwater does not come into contact with the dispenser 112. The roof 115 has a ventilation structure that prevents rainwater from passing through from above, but allows hydrogen-containing air from below to pass upwards, in order to diffuse the hydrogen that leaks and rises into the atmosphere when hydrogen is supplied to the vehicle 124.

[0057] Furthermore, the hydrogen station 100 is equipped with fire prevention equipment to monitor hydrogen leaks and fires. The fire prevention equipment includes a receiver 118, a fire detector 120, a transmitter 122, and a hydrogen flame detection device 10 for fire monitoring. The fire detector 120, transmitter 122, and hydrogen flame detection device 10 are connected to a signal line drawn from the receiver 118 located in the office 116. When the receiver 118 receives a fire alarm signal from the fire detector 120 or a fire notification signal from the transmitter 122, it outputs a fire alarm and also outputs a relay signal to other equipment.

[0058] The hydrogen flame detection device 10 is installed in a position that allows it to oversee the inside of the hydrogen station 100, including the dispenser 112, which is highly likely to generate a hydrogen flame due to the combustion of leaked hydrogen. The light receiving axis is set so that the dispenser 112 is included in the monitoring area.

[0059] A hydrogen fire at a hydrogen station 100 occurs when hydrogen leaks for some reason during hydrogen supply, for example, when a filling hose 114 is connected from a dispenser 112 to a vehicle 124, and the leaked hydrogen ignites due to some factor, such as static electricity. However, a hydrogen flame is a colorless and transparent flame, making it difficult to see with the naked eye, and it is also difficult to detect with a conventional fire detector 120. Therefore, in this embodiment, a hydrogen flame detection device 10 detects the hydrogen flame and transmits a hydrogen flame detection signal to a receiver 118, which then issues an alarm indicating that a hydrogen flame has occurred, thereby enabling early detection of the hydrogen flame and rapid firefighting activities.

[0060] Furthermore, although not shown in the diagram, the hydrogen station 100 is also equipped with disaster prevention equipment, including multiple water spray heads installed for the storage facility 110 and dispenser 112, a water spray pump system that supplies fire extinguishing agent (fire extinguishing water, etc.) to the water spray heads via water supply piping, an emergency power supply system installed for the water spray pump system as a countermeasure against power outages, and a gas detection device for monitoring hydrogen leaks. In addition, fire extinguishers are placed in various locations within the hydrogen station 100.

[0061] [b. Hydrogen Flame Detection Device] Next, the hydrogen flame detection device will be described. In this description, please refer to Figure 2, which shows an example of the configuration of the hydrogen flame detection device, Figure 3, which shows the emission intensity distribution (wavelength spectrum) of the hydrogen flame, and Figure 4, which shows the observed values ​​when infrared light is received from the hydrogen flame. Note that Figure 3 shows the emission intensity distribution (wavelength spectrum) in the infrared region (wavelength 0.7 μm to 2.8 μm).

[0062] (b1. Overall configuration of the hydrogen flame detection device) First, the overall configuration of the hydrogen flame detection device will be explained. As shown in Figure 2, the hydrogen flame detection device 10 receives light from a hydrogen flame and detects the hydrogen flame based on the received light signal obtained from the received light, and comprises a first light receiving unit 12, a second light receiving unit 14, and a control unit 15.

[0063] Here, it has been confirmed that hydrogen flames emit almost no light in the visible region, and the spectral spectrum of light emitted from hydrogen flames has characteristic peaks in the ultraviolet wavelength band of approximately 278–320 nm and the infrared wavelength band of 925–950 nm. (See "Development of a wearable device for visualizing hydrogen flames by passive infrared spectroscopy, Shoichi Hagita et al., Shikoku Electric Power Co., Inc., Shikoku Electric Power Transmission & Distribution Co., Inc., Shikoku Research Institute, Research Report 118 (June 2023) 11-19"). In addition, as shown in Figure 3, the spectral spectrum of light emitted from hydrogen flames has been confirmed to have characteristic peaks in the infrared wavelength bands of approximately 1.3–1.7 μm and approximately 1.8 μm–2.1 μm.

[0064] The first light receiving unit 12 receives infrared light in a narrowband wavelength range with a central wavelength of 1.5 μm in order to receive light in a characteristic wavelength range specific to hydrogen flames, for example, infrared light contained in the range of approximately 1.3 to 1.7 μm emitted from a hydrogen flame. The received infrared light is converted into an electrical signal, the hydrogen flame observation value E1 (first light receiving signal), by photoelectric conversion and predetermined amplification processing, and output.

[0065] The second light receiving unit 14 receives light in a wavelength band different from the characteristic wavelength band specific to hydrogen flames, for example, infrared light in a narrow-band wavelength band with a central wavelength of 2.3 μm. The received infrared light is converted into an electrical signal, the non-hydrogen flame observation value E2 (second received signal), through photoelectric conversion and predetermined amplification processing, and output. The operation of the first light receiving unit 12 and the second light receiving unit 14 is synchronized, and the hydrogen flame observation value E1 and the non-hydrogen flame observation value E2 are controlled to be observation values ​​(received signals) based on infrared light received at approximately the same time. The hydrogen flame observation value E1 and the non-hydrogen flame observation value E2 are sometimes referred to as observation values ​​E1 and E2.

[0066] The control unit 15 detects a hydrogen flame based on the hydrogen flame observation value E1 and the non-hydrogen flame observation value E2 output from the first light receiving unit 12 and the second light receiving unit 14.

[0067] (b2. First light receiving unit) Next, the first light receiving unit will be described. The first light receiving unit 12 includes a light-transmitting window 16, a first light receiving section 18, and an amplification processing section 20.

[0068] The first light receiving unit 18 receives infrared light in a narrowband wavelength range with a central wavelength of 1.5 μm, converts the received infrared light into a first light-receiving signal by photoelectric conversion, and outputs it to the amplification processing unit 20. For example, it includes an optical wavelength filter 1810 that corresponds to infrared light in a narrowband wavelength range with a central wavelength of 1.5 μm and a light-receiving element unit 1812 that is sensitive to infrared light in a narrowband wavelength range with a central wavelength of 1.5 μm.

[0069] The light-transmitting window 16 is shared with the second light-receiving unit 14 and is made of a light-transmitting material that transmits infrared light, such as sapphire glass. Light from outside the hydrogen flame detection device 10 is incident on the light-receiving element section 1812 via the light-transmitting window 16 and the optical wavelength filter 1810.

[0070] The amplification processing unit 20 includes, for example, a pre-filter 2010, a pre-amplifier 2012, a main amplifier 2014, and a final stage amplifier 2016. The pre-filter 2010 allows a predetermined frequency band of the first received light signal output from the first light receiving unit 18 to pass through, corresponding to the frequency of the fluctuation component of the hydrogen flame. The pre-amplifier 2012 amplifies the first received light signal that has passed through the pre-filter 2010. The main amplifier 2014 further amplifies the first received light signal amplified by the pre-amplifier 2020 and outputs it. The final stage amplifier 2016 outputs the first received light signal amplified by the main amplifier 2014 to the control unit 15 as a hydrogen flame observation value E1, amplified to a signal level suitable for processing in the control unit 15.

[0071] (b3. Second light receiving unit) Next, the second light receiving unit will be described. The second light receiving unit 14 includes a light-transmitting window 16, a second light receiving section 22, and an amplification processing section 24, which are shared with the first light receiving unit 12.

[0072] The second light-receiving unit 22 receives infrared light in a narrowband wavelength range with a central wavelength of 2.3 μm, converts the received infrared light into a second light-receiving signal by photoelectric conversion, and outputs it to the amplification processing unit 24. For example, it includes an optical wavelength filter 2210 that corresponds to infrared light in a narrowband wavelength range with a central wavelength of 2.3 μm, and a light-receiving element unit 2212 that is sensitive to infrared light in a narrowband wavelength range with a central wavelength of 2.3 μm. In addition, light from outside the hydrogen flame detection device 10 is incident on the light-receiving element unit 2212 through the light-transmitting window 16 and the optical wavelength filter 2210.

[0073] The amplification processing unit 24 includes, for example, a pre-filter 2410, a pre-amplifier 2412, a main amplifier 2414, and a final stage amplifier 2416. The pre-filter 2410 allows the second received signal from the second received signal output from the second light receiving unit 22 to pass through a predetermined frequency band corresponding to the frequency of the fluctuation component of the hydrogen flame. The pre-amplifier 2412 amplifies the second received signal that has passed through the pre-filter 2410. The main amplifier 2414 further amplifies the second received signal amplified by the pre-amplifier 2412 and outputs it. The final stage amplifier 2416 outputs the second received signal amplified by the main amplifier 2414 to the control unit 15 as a non-hydrogen flame observation value E2, amplified to a signal level suitable for processing in the control unit 15.

[0074] (b4. Control Unit) Next, the control unit 15 will be described. The control unit 15 is a computer circuit equipped with, for example, a CPU, memory, various input / output ports, etc. as hardware, and includes an A / D conversion port 1510 which is the input port for the hydrogen flame observation value E1 output from the amplification processing unit 20 of the first light receiving unit 12, and an A / D conversion port 1512 which is the input port for the non-hydrogen flame observation value E2 output from the amplification processing unit 24 of the second light receiving unit 14, and a buffer memory 26, and a hydrogen flame determination unit 28 which is a function realized by the control unit 15.

[0075] The A / D conversion port 1510 converts the analog data of the hydrogen flame observation value E1 output from the final stage amplifier 2016 of the amplification processing unit 20 into digital data and outputs it to the buffer memory 26. Similarly, the A / D conversion port 1512 is the same as the A / D conversion port 1510, and converts the analog data of the non-hydrogen flame observation value E2 output from the final stage amplifier 2416 of the amplification processing unit 24 into digital data and outputs it to the buffer memory 26. Furthermore, the analog data of the hydrogen flame observation value E1 and the non-hydrogen flame observation value E2 are sampled at, for example, 64 Hz and converted into digital data, and the hydrogen flame observation value E1 (digital data) and non-hydrogen flame observation value E2 (digital data) for a predetermined period T, for example, 2 seconds, are temporarily stored in the buffer memory 26.

[0076] Here, when the first light receiving unit 12 and the second light receiving unit 14 receive light from the hydrogen flame, the hydrogen flame observation value E1 is a received signal based on infrared radiation in a narrow wavelength band with a central wavelength of 1.5 μm, that is, infrared radiation of approximately 1.3 to 1.7 μm, which has a relatively high emission intensity in the hydrogen flame. On the other hand, the non-hydrogen flame observation value E2 is a received signal based on infrared radiation in a narrow wavelength band with a central wavelength of 2.3 μm, that is, infrared radiation with a relatively low emission intensity in the hydrogen flame. As shown in Figure 4, the signal level of the non-hydrogen flame observation value E2 is smaller than that of the hydrogen flame observation value E1 (the amplitude of the signal waveform is smaller), but the signal waveforms of the hydrogen flame observation value E1 and the non-hydrogen flame observation value E2 are highly similar.

[0077] The hydrogen flame determination unit 28 detects a hydrogen flame by using hydrogen flame observation values ​​E1 and non-hydrogen flame observation values ​​E2 (digital data) stored in the buffer memory 26 for a predetermined period T to determine whether it is a hydrogen flame. For example, the hydrogen flame determination for detecting the hydrogen flame includes the first and second embodiments shown below.

[0078] [c. First Embodiment of Hydrogen Flame Determination] Next, a first embodiment of hydrogen flame determination by the hydrogen flame determination unit will be described. In the first embodiment of hydrogen flame determination, whether or not it is a hydrogen flame is determined by determining whether or not the following first to third hydrogen flame determination conditions are met.

[0079] (c1. First Hydrogen Flame Determination Condition) First, the first hydrogen flame determination condition in the first embodiment will be described. The first hydrogen flame determination condition in the first embodiment is a condition based on the signal level of the hydrogen flame observation value E1. In the determination using the first hydrogen flame determination condition, for example, the determination is made using the integral value ΣE1 obtained by integrating the hydrogen flame observation value E1 for a predetermined period T.

[0080] The hydrogen flame determination unit 28 reads the hydrogen flame observation value E1 stored in the buffer memory 26 for a predetermined period T minutes, for example, 2 seconds, and calculates the integral value ΣE1. Here, as shown in Figure 4, the integral value of the hydrogen flame observation value E1 is the value obtained by integrating the absolute value of the difference in signal level with respect to the reference potential, with the midpoint position in the signal waveform of the hydrogen flame observation value E1 being used as the reference potential.

[0081] Next, the hydrogen flame observation value E1 is a received signal based on infrared radiation in a narrow wavelength band with a central wavelength of 1.5 μm, that is, infrared radiation of approximately 1.3 to 1.7 μm, which has a relatively high emission intensity in a hydrogen flame. When the first light receiving unit 12 receives light from the hydrogen flame, the signal level is large (the amplitude of the signal waveform is large). Therefore, the hydrogen flame determination unit 28 determines that the first hydrogen flame determination condition is satisfied, for example, when the integral value ΣE1 of the hydrogen flame observation value E1 is equal to or greater than a predetermined threshold Eth or exceeds the threshold Eth.

[0082] (c2. Second Hydrogen Flame Determination Condition) Next, the second hydrogen flame determination condition in the first embodiment will be described. The second hydrogen flame determination condition in the first embodiment is a condition based on the correlation of the signal waveforms of the hydrogen flame observation value E1 and the non-hydrogen flame observation value E2. In the determination using the second hydrogen flame determination condition, the determination is made using the ratio of the integral values ​​of the hydrogen flame observation value E1 and the non-hydrogen flame observation value E2.

[0083] The hydrogen flame determination unit 28 reads the hydrogen flame observation value E1 and non-hydrogen flame observation value E2 stored in the buffer memory 26 for a predetermined period T minutes, for example, 2 seconds. It divides each of the hydrogen flame observation value E1 and non-hydrogen flame observation value E2 into four time intervals T1, T2, T3, and T4 of 500 milliseconds, as shown in Figure 4. For the hydrogen flame observation value E1, it calculates the integral values ​​ΣE11, ΣE12, ΣE13, and ΣE14 for each time interval T1 to T4, and for the non-hydrogen flame observation value E2, it calculates the integral values ​​ΣE21, ΣE22, ΣE23, and ΣE24 for each time interval T1 to T4. Here, the integral value of the non-hydrogen flame observation value E2 is the same as the integral value of the hydrogen flame observation value E1, as shown in Figure 4, and is the value obtained by integrating the absolute value of the difference in signal level with respect to the reference potential, with the midpoint position of the non-hydrogen flame observation value E2 as the reference potential.

[0084] Next, the hydrogen flame determination unit 28 calculates the ratios R1, R2, R3, and R4 of the hydrogen flame observation integral values ​​ΣE11 to ΣE14 and the non-hydrogen flame observation integral values ​​ΣE21 to ΣE24 for each of the same time intervals T1 to T4 from the following equations (1) to (4). These R1 to R4 represent the relationship between the signal waveforms of the hydrogen flame observation value E1 and the non-hydrogen flame observation value E2 in each time interval. R1 = ΣE11 / ΣE21 Equation (1) R2 = ΣE12 / ΣE22 Equation (2) R3 = ΣE13 / ΣE23 Equation (3) R4 = ΣE14 / ΣE24 Equation (4)

[0085] Next, the hydrogen flame determination unit 28 sets a hydrogen flame determination threshold range having a lower threshold TH1 and an upper threshold TH2, for example, based on the ratio R1 of the integral values ​​in the first time interval T1.

[0086] The hydrogen flame detection threshold range is set with, for example, a lower threshold TH1 (= 0.9 * R1) and an upper threshold TH2 (= 1.1 * R1) of ±10% of the ratio R1 of the first time interval T1. If this is not limited to ±10%, then the lower threshold TH1 (= α * R1) is set by multiplying the ratio R1 of the integral values ​​of the first time interval T1 by a predetermined constant α less than 1, and the upper threshold TH2 (= β * R1) is set by multiplying it by a predetermined constant β greater than 1. The coefficients α and β can be set to appropriate values ​​as needed.

[0087] Next, if, for example, the hydrogen flame determination threshold range is set with a lower threshold TH1 (= 0.9 * R1) and an upper threshold TH2 (= 1.1 * R1) of ±10% of the ratio R1 of the first time interval T1, the hydrogen flame determination unit 28 will determine whether or not the conditions shown in the following equations (5) to (7) are satisfied. 0.9 * R1 ≤ R2 ≤ 1.1 * R1 Equation (5) 0.9 * R1 ≤ R3 ≤ 1.1 * R1 Equation (6) 0.9 * R1 ≤ R4 ≤ 1.1 * R1 Equation (7)

[0088] Next, if it is determined that all the conditions in equations (5) to (7) are satisfied, that is, if all the ratios R1 to R4 of the integral values ​​in the time intervals T1 to T4 are within the hydrogen flame determination threshold range, then the hydrogen flame determination unit 28 determines that the second hydrogen flame determination condition is satisfied, because it can be estimated that the first light receiving unit 12 and the second light receiving unit 14 are receiving light from the hydrogen flame, and there is a correlation between the signal waveforms of the hydrogen flame observation value E1 and the non-hydrogen flame observation value E2 in each time interval.

[0089] On the other hand, if at least one of the conditions in equations (5) to (7) is not satisfied, that is, if at least one of the ratios R2 to R4 of the integral values ​​in the time interval T2 to T4 is not within the hydrogen flame determination threshold range, the hydrogen flame determination unit 28 determines that the second hydrogen flame determination condition is not satisfied, since it can be estimated that the first light receiving unit 12 and the second light receiving unit 14 have not received light from the hydrogen flame.

[0090] (c3. Third Hydrogen Flame Determination Conditions) Next, the third hydrogen flame determination conditions in the first embodiment will be described. In this description, refer to Figure 5, which shows the frequency spectrum of the received signal when light is received from a hydrogen flame.

[0091] In the first embodiment, the third hydrogen flame determination condition is a condition based on the correlation of the frequency characteristics of the hydrogen flame observation value E1 and the non-hydrogen flame observation value E2. In the determination using the third hydrogen flame determination condition, the determination is made using the ratio of the integral values ​​of the frequency spectra of the hydrogen flame observation value E1 and the non-hydrogen flame observation value E2.

[0092] The hydrogen flame determination unit 28 reads the hydrogen flame observation value E1 and non-hydrogen flame observation value E2 stored in the buffer memory 26 for a predetermined period T minutes, for example, 2 seconds. It divides each of the hydrogen flame observation value E1 and non-hydrogen flame observation value E2 into four time intervals T1, T2, T3, and T4 of 500 milliseconds, as shown in Figure 4, and performs a predetermined frequency analysis, such as a fast Fourier transform, on the hydrogen flame observation value E1 and non-hydrogen flame observation value E2 for each time interval T1 to T4 to generate a frequency spectrum.

[0093] Here, the hydrogen flame is a flame with a fluctuation frequency of approximately 3 to 5 Hz. When light from the hydrogen flame is received, the frequency spectrum of the received signal will show a relatively high peak at approximately 3 to 5 Hz, as shown in Figure 5, for example, in the frequency spectrum of 1 to 16 Hz. Also, the low-frequency side of 1 to 8 Hz will be at a relatively higher level than the high-frequency side of 8 to 16 Hz. In other words, the frequency spectrum of the received signal when light from the hydrogen flame is received is a frequency spectrum characterized by the low-frequency side of approximately 3 to 5 Hz, and the correlation between the frequency characteristics of the hydrogen flame observation value E1 and the non-hydrogen flame observation value E2 can be determined using, for example, the frequency spectrum in the low-frequency side of 1 to 8 Hz.

[0094] Next, the hydrogen flame determination unit 28 calculates the integral values ​​Σf11, Σf12, Σf13, and Σf14 for each time interval T1 to T4 of the frequency spectrum of the observed hydrogen flame value E1, and calculates the integral values ​​Σf21, Σf22, Σf23, and Σf24 for each time interval T1 to T4 of the frequency spectrum of the observed non-hydrogen flame value E2.

[0095] Next, the hydrogen flame determination unit 28 calculates the ratios Rf1, Rf2, Rf3, and Rf4 of the integral values ​​Σf11 to Σf14 of the frequency spectrum of the observed hydrogen flame value E1 and the integral values ​​Σf21 to Σf24 of the frequency spectrum of the observed non-hydrogen flame value E2 for each of the same time intervals T1 to T4, from the following equations (8) to (11). These Rf1 to Rf4 represent the relationship between the frequency characteristics of the observed hydrogen flame value E1 and the observed non-hydrogen flame value E2 in each time interval. Rf1 = Σf11 / Σf21 Equation (8) Rf2 = Σf12 / Σf22 Equation (9) Rf3 = Σf13 / Σf23 Equation (10) Rf4 = Σf14 / Σf24 Equation (11)

[0096] Next, the hydrogen flame determination unit 28 sets a hydrogen flame determination threshold range having a lower threshold THf1 and an upper threshold THf2, based on, for example, the ratio Rf1 of the integral values ​​in the first time interval T1. Here, the hydrogen flame determination threshold range is set, for example, similar to the hydrogen flame determination threshold range of the second hydrogen flame determination condition, with a lower threshold THf1 (= 0.9 * Rf1) and an upper threshold THf2 (= 1.1 * Rf1) of ±10% of the ratio Rf1 in the first time interval T1.

[0097] Next, the hydrogen flame determination unit 28 determines whether the conditions shown in the following equations (12) to (14) are satisfied. 0.9 * Rf1 ≤ Rf2 ≤ 1.1 * Rf1 Equation (12) 0.9 * Rf1 ≤ Rf3 ≤ 1.1 * Rf1 Equation (13) 0.9 * Rf1 ≤ Rf4 ≤ 1.1 * Rf1 Equation (14)

[0098] Next, if it is determined that all the conditions in equations (12) to (14) are satisfied, that is, if all the ratios Rf1 to Rf4 of the integral values ​​of the frequency spectrum in the time interval T1 to T4 are within the hydrogen flame determination threshold range, then it can be estimated that there is a correlation between the frequency characteristics of the hydrogen flame observed value E1 and the non-hydrogen flame observed value E2 in each time interval, and that the first light receiving unit 12 and the second light receiving unit 14 are receiving light from the hydrogen flame. Therefore, the hydrogen flame determination unit 28 determines that the third hydrogen flame determination condition is satisfied.

[0099] On the other hand, if at least one of the conditions in equations (12) to (14) is not satisfied, that is, if at least one of the ratios Rf2 to Rf4 of the integral values ​​of the frequency spectrum in the time interval T2 to T4 is not within the hydrogen flame determination threshold range, the first light receiving unit 12 and the second light receiving unit 14 are presumed not to have received light from the hydrogen flame, and the hydrogen flame determination unit 28 determines that the third hydrogen flame determination condition is not satisfied.

[0100] (c4. Detection of hydrogen flame) Finally, the hydrogen flame determination unit 28 determines that it is a hydrogen flame and detects it if all of the first to third hydrogen flame determination conditions described above are met. If a hydrogen flame is detected, it outputs a hydrogen flame detection signal to the receiver 118. If at least one of the first to third hydrogen flame determination conditions is not met, it determines that it is not a hydrogen flame.

[0101] Furthermore, in the final determination of whether or not it is a hydrogen flame by the hydrogen flame determination unit 28, the determination may also include the degree of certainty that it is a hydrogen flame. For example, the degree of certainty that it is a hydrogen flame may be varied according to the number of hydrogen flame determination conditions that are satisfied out of the three conditions of the first to third hydrogen flame determination conditions, and the determination of whether or not it is a hydrogen flame may be divided into four stages.

[0102] For example, if all hydrogen flame detection conditions are met and the highest probability of it being a hydrogen flame is determined, a hydrogen flame detection signal is output to the receiver 118, causing the receiver 118 to issue an alarm indicating that a hydrogen flame has occurred. If two hydrogen flame detection conditions are met and the second highest probability of it being a hydrogen flame is determined, or if one hydrogen flame detection condition is met and the third highest probability of it being a hydrogen flame is determined, a hydrogen flame warning signal is output to the receiver 118, causing the receiver 118 to issue a warning alarm (a lower alarm level than the alarm indicating that a hydrogen flame has occurred) indicating that a hydrogen flame may have occurred. If none of the hydrogen flame detection conditions are met, it is determined that it is not a hydrogen flame. Note that different warning alarms may be issued depending on the number of hydrogen flame detection conditions that are met.

[0103] [d. Hydrogen flame detection process using the hydrogen flame determination of the first embodiment] Next, the hydrogen flame detection process using the hydrogen flame determination of the first embodiment by the hydrogen flame determination unit will be described. In this description, refer to Figure 6, which is a flowchart showing an example of the hydrogen flame detection process using the hydrogen flame determination of the first embodiment.

[0104] First, the hydrogen flame determination unit 28 reads the hydrogen flame observation value E1 and non-hydrogen flame observation value E2 stored in the buffer memory 26 for a predetermined period T minutes, for example, 2 seconds. It then calculates an integral value ΣE1 from the read hydrogen flame observation value E1 and determines that the first hydrogen flame determination condition is satisfied if the integral value ΣE1 is greater than or equal to the threshold Eth (steps S1 to S3).

[0105] Furthermore, if the hydrogen flame determination unit 28 determines in step S2 that the integral value ΣE1 is not equal to or greater than the threshold Eth, it determines that it is not a hydrogen flame, and the process returns to before step S1. The hydrogen flame observation value E1 and non-hydrogen flame observation value E2 for the next 2 seconds are then read and processed in the same manner according to the flowchart.

[0106] Next, the hydrogen flame determination unit 28 divides the read hydrogen flame observation value E1 and non-hydrogen flame observation value E2 into four time intervals T1 to T4, calculates the integral values ​​ΣE11 to ΣE14 of the hydrogen flame observation value E1 and the integral values ​​ΣE21 to ΣE24 of the non-hydrogen flame observation value E2 for each time interval T1 to T4, and calculates the ratios R1 to R4 of the integral values ​​ΣE11 to ΣE14 and the integral values ​​ΣE21 to ΣE24 for each of the same time intervals T1 to T4 (steps S4 to S5).

[0107] Next, the hydrogen flame determination unit 28 sets a lower threshold TH1 and an upper threshold TH2 of the hydrogen flame determination threshold range based on the ratio R1 of the integral values ​​in any time interval, for example, the first time interval T1. It then compares the ratios R2 to R4 of the integral values ​​in time intervals T2 to T4 with the lower threshold TH1 and upper threshold TH2 of the hydrogen flame determination threshold range, and determines that the second hydrogen flame determination condition is satisfied if all of the ratios R1 to R4 of the integral values ​​are within the hydrogen flame determination threshold range (steps S6 to S8).

[0108] Furthermore, if in step S7 at least one of the ratios R2 to R4 of the integral values ​​in the time interval T2 to T4 is not within the hydrogen flame determination threshold range, the hydrogen flame determination unit 28 determines that it is not a hydrogen flame, returns to the step before S1, reads the hydrogen flame observation value E1 and the non-hydrogen flame observation value E2 for the next 2 seconds, and performs the same processing according to the flowchart.

[0109] Next, the hydrogen flame determination unit 28 performs a Fast Fourier Transform on the hydrogen flame observation value E1 and the non-hydrogen flame observation value E2 in each time interval T1 to T4 to generate frequency spectra. For the hydrogen flame observation value E1, it calculates the integral values ​​Σf11 to Σf14 of the frequency spectra in each time interval T1 to T4, and for the non-hydrogen flame observation value E2, it calculates the integral values ​​Σf21 to Σf24 of the frequency spectra in each time interval T1 to T4. For each of the same time intervals T1 to T4, it calculates the ratio Rf1 to Rf4 of the integral values ​​ΣEf11 to ΣEf14 and the integral values ​​ΣEf21 to ΣEf24. (Steps S9 to S11).

[0110] Next, the hydrogen flame determination unit 28 sets a lower threshold THf1 and an upper threshold THf2 of the hydrogen flame determination threshold range based on the ratio Rf1 of the integral values ​​in any time interval, for example, the first time interval T1. It then compares the ratios Rf2 to Rf4 of the integral values ​​in time intervals T2 to T4 with the lower threshold THf1 and the upper threshold THf2 of the hydrogen flame determination threshold range, and determines that the third hydrogen flame determination condition is satisfied if all of the ratios Rf1 to Rf4 of the integral values ​​in time intervals T1 to T4 are within the hydrogen flame determination threshold range (steps S12 to S14).

[0111] Next, the hydrogen flame determination unit 28 determines that the third hydrogen flame determination condition is satisfied, which means that all of the first to third hydrogen flame determination conditions are now satisfied. Therefore, it determines that it is a hydrogen flame, detects the hydrogen flame, and outputs a hydrogen flame detection signal (step S15). The process then returns to before step S1, and the hydrogen flame observation value E1 and non-hydrogen flame observation value E2 for the next two seconds are read out and processed in the same manner according to the flowchart.

[0112] Furthermore, if in step S13 the hydrogen flame determination unit 28 determines that it is not a hydrogen flame if at least one of the ratios Rf2 to Rf4 of the integral values ​​in the time interval T2 to T4 is not within the hydrogen flame determination threshold range, the process returns to before step S1, and the hydrogen flame observation value E1 and non-hydrogen flame observation value E2 for the next 2 seconds are read and processed in the same manner according to the flowchart.

[0113] [e. Second Embodiment of Hydrogen Flame Determination] Next, a second embodiment of hydrogen flame determination by the hydrogen flame determination unit will be described. In the second embodiment of hydrogen flame determination, whether or not it is a hydrogen flame is determined by determining whether or not the following first to third hydrogen flame determination conditions are met.

[0114] (e1. First Hydrogen Flame Determination Unit) First, the first hydrogen flame determination conditions in the second embodiment will be described. The first hydrogen flame determination conditions in the second embodiment are the same as the first hydrogen flame determination conditions in the first embodiment, and are conditions based on the signal level of the hydrogen flame observation value E1. In the determination using the first hydrogen flame determination conditions, for example, the determination is made using the integral value ΣE1 of the hydrogen flame observation value E1 over a predetermined period T, and the hydrogen flame determination unit 28 determines that the first hydrogen flame determination conditions have been satisfied when the integral value ΣE1 of the hydrogen flame observation value E1 is equal to or greater than a predetermined threshold Eth or exceeds the threshold Eth.

[0115] (e2. Second Hydrogen Flame Determination Condition) Next, the second hydrogen flame determination condition in the second embodiment will be described. The second hydrogen flame determination condition in the second embodiment is a condition based on the signal levels of the hydrogen flame observation value E1 and the non-hydrogen flame observation value E2. In the determination using the second hydrogen flame determination condition, the determination is made using the ratio of the integral values ​​of the hydrogen flame observation value E1 and the non-hydrogen flame observation value E2.

[0116] The hydrogen flame determination unit 28 reads the hydrogen flame observation value E1 and the non-hydrogen flame observation value E2 stored in the buffer memory 26 for a predetermined period T minutes, for example, 2 seconds, calculates the integral value ΣE1 of the hydrogen flame observation value E1, and calculates the integral value ΣE2 of the non-hydrogen flame observation value E2.

[0117] Next, the hydrogen flame determination unit 28 calculates the ratio R of the integral value ΣE1 of the hydrogen flame observation value E1 and the integral value ΣE2 of the non-hydrogen flame observation value E2 from the following equation (15): R = ΣE1 / ΣE2 Equation (15)

[0118] Next, when the first light receiving unit 12 and the second light receiving unit 14 receive light from the hydrogen flame, the hydrogen flame observation value E1 is a received signal based on infrared radiation in a narrowband wavelength range with a central wavelength of 1.5 μm, that is, infrared radiation of approximately 1.3 to 1.7 μm, which has a relatively high emission intensity in the hydrogen flame, while the non-hydrogen flame observation value E2 is a received signal based on infrared radiation in a narrowband wavelength range with a central wavelength of 2.3 μm, that is, infrared radiation with a relatively low emission intensity in the hydrogen flame. Since the integral value ΣE1 of the hydrogen flame observation value E1 is larger than the integral value ΣE2 of the non-hydrogen flame observation value E2, the hydrogen flame determination unit 28 determines that the second hydrogen flame determination condition is satisfied when the ratio R is equal to or greater than a predetermined threshold Rth or exceeds the threshold Rth.

[0119] (e3. Third Hydrogen Flame Determination Condition) Next, the third hydrogen flame determination condition in the second embodiment will be described. The second hydrogen flame determination condition in the second embodiment is a condition based on the frequency characteristics of the observed hydrogen flame value E1, and the determination using the third hydrogen flame determination condition is made using the integral value of the frequency spectrum of the observed hydrogen flame value E1.

[0120] As shown in Figure 5, the frequency spectrum of the received signal when light from a hydrogen flame is received shows a relatively high peak at approximately 3 to 5 Hz, and the low-frequency side from 1 to 8 Hz is at a relatively higher level than the high-frequency side from 8 to 16 Hz. For this reason, the hydrogen flame determination unit 28 divides the frequency spectrum of the hydrogen flame observation value E1 into a low-frequency spectrum including, for example, 3 to 5 Hz and a high-frequency spectrum, and determines the frequency characteristics of the hydrogen flame observation value E1 by comparing the integral values ​​of the low-frequency spectrum and the high-frequency spectrum.

[0121] The hydrogen flame determination unit 28 reads the hydrogen flame observation value E1 stored in the buffer memory 26 for a predetermined period T minutes, for example, 2 seconds, and performs a predetermined frequency analysis such as a fast Fourier transform on the hydrogen flame observation value E1 to generate a frequency spectrum.

[0122] Next, as shown in Figure 5, the hydrogen flame determination unit 28 divides the generated frequency spectrum into a low-frequency spectrum on the low-frequency side (e.g., 1 to 8 Hz) and a high-frequency spectrum on the high-frequency side (e.g., 8 to 16 Hz), calculates the integral value ΣfL of the low-frequency spectrum of the hydrogen flame observation value E1, and also calculates the integral value ΣfH of the high-frequency spectrum of the hydrogen flame observation value E1.

[0123] Next, the hydrogen-hydrogen flame determination unit 28 calculates the ratio Rf of the integral value ΣfL on the low-frequency side and the integral value ΣfH on the high-frequency side from the following equation (16): Rf = ΣfL / ΣfH Equation (16)

[0124] Next, when the first light receiving unit 12 receives light from the hydrogen flame, the integral value ΣfL of the low-frequency spectrum becomes larger than the integral value ΣfH of the high-frequency spectrum. Therefore, the hydrogen flame determination unit 28 determines that the third hydrogen flame determination condition is satisfied when the ratio Rf is equal to or greater than a predetermined threshold Rfth or exceeds the threshold Rfth.

[0125] Furthermore, the non-hydrogen flame observation value E2 may also be evaluated based on its frequency characteristics, similar to the hydrogen flame observation value E1.

[0126] (e4. Detection of hydrogen flame) Finally, the hydrogen flame determination unit 28 determines that a hydrogen flame is present and detects it if all of the first to third hydrogen flame determination conditions described above are met and the number of times the second to third hydrogen flame determination conditions are met reaches a predetermined number of accumulated occurrences. If a hydrogen flame is detected, it outputs a hydrogen flame detection signal to the receiver 118. If at least one of the first to third hydrogen flame determination conditions is not met, or if the number of times the second to third hydrogen flame determination conditions are met has not reached a predetermined number of accumulated occurrences, it determines that it is not a hydrogen flame.

[0127] Furthermore, in determining whether it is the final hydrogen flame by the hydrogen flame determination unit 28, the determination may include the accuracy of the hydrogen flame, as in the first embodiment. Alternatively, the determination may be made as in the first embodiment, when all of the first to third hydrogen flame determination conditions are satisfied, without including the condition regarding the number of accumulations. Also, the condition regarding the number of accumulations is not limited to the second to third hydrogen flame determination conditions of the second embodiment, but may be set for other conditions such as the first hydrogen flame determination condition of the second embodiment or the first to third hydrogen flame determination conditions of the first embodiment.

[0128] [f. Hydrogen flame detection process using the hydrogen flame determination of the second embodiment] Next, the hydrogen flame detection process using the hydrogen flame determination of the second embodiment by the hydrogen flame determination unit will be described. In this description, refer to Figure 7, which is a flowchart showing an example of the hydrogen flame detection process using the hydrogen flame determination of the second embodiment.

[0129] First, the hydrogen flame determination unit 28 reads the hydrogen flame observation value E1 and non-hydrogen flame observation value E2 stored in the buffer memory 26 for a predetermined period T minutes, for example, 2 seconds. It then calculates an integral value ΣE1 from the read hydrogen flame observation value E1 and determines that the first hydrogen flame determination condition is met if the integral value ΣE1 is greater than or equal to the threshold Eth (steps S21 to S23).

[0130] Furthermore, if the hydrogen flame determination unit 28 determines in step S22 that the integral value ΣE1 is not equal to or greater than the threshold Eth, it determines that it is not a hydrogen flame, and the process returns to before step S21. The hydrogen flame observation value E1 and non-hydrogen flame observation value E2 for the next 2 seconds are then read and processed in the same manner according to the flowchart.

[0131] Next, the hydrogen flame determination unit 28 calculates an integral value ΣE2 from the read-out non-hydrogen flame observation value E2, calculates the ratio R of the integral value ΣE1 and the integral value ΣE2, and determines that the second hydrogen flame determination condition is satisfied if the ratio R of the integral values ​​is greater than or equal to the threshold Rth (steps S24 to S28).

[0132] Next, the hydrogen flame determination unit 28 repeats the processes in steps S21 to S28 until the number of times it has determined that the second hydrogen flame determination condition has been met reaches a predetermined number of accumulated counts. Once the number of times it has determined that the second hydrogen flame determination condition has been met reaches the accumulated count, it moves on to the next process (step S29).

[0133] Furthermore, if the hydrogen flame determination unit 28 determines in step S27 that the ratio R of the integral values ​​is not equal to or greater than the threshold Rth, it determines that it is not a hydrogen flame, and the process returns to before step S21. It then reads the hydrogen flame observation value E1 and the non-hydrogen flame observation value E2 for the next 2 seconds and performs the same process according to the flowchart.

[0134] Next, the hydrogen flame determination unit 28 performs a fast Fourier transform on the observed hydrogen flame value E1 to generate a frequency spectrum. The frequency spectrum is divided into a low-frequency spectrum containing 3 to 5 Hz and a high-frequency spectrum. The integral value ΣfL of the low-frequency spectrum is calculated, as is the integral value ΣfH of the high-frequency spectrum. The ratio Rf of the integral values ​​ΣfL and ΣfH is calculated, and if the ratio Rf of the integral values ​​is greater than or equal to the threshold Rfth, the third hydrogen flame determination condition is determined to be satisfied (steps S30 to S35).

[0135] Next, the hydrogen flame determination unit 28 repeats the processes in steps S21 to S35 until the number of times it has determined that the third hydrogen flame determination condition has been met reaches a predetermined number of accumulated counts. Once the number of times it has determined that the third hydrogen flame determination condition has been met reaches the accumulated count, it moves on to the next process (step S36).

[0136] Next, the hydrogen flame determination unit 28 determines that when the number of times it has determined that the third hydrogen flame determination condition has been met reaches the accumulated number, all of the first to third hydrogen flame determination conditions have been met and the number of times the second to third hydrogen flame determination conditions have been met has reached a predetermined accumulated number. Therefore, it determines that it is a hydrogen flame, detects the hydrogen flame, and outputs a hydrogen flame detection signal (step S37). The process then returns to before step S21, and the hydrogen flame observation value E1 and non-hydrogen flame observation value E2 for the next two seconds are read and processed in the same manner according to the flowchart.

[0137] Furthermore, if the hydrogen flame determination unit 28 determines in step S34 that the ratio Rf of the integral values ​​is not equal to or greater than the threshold Rfth, it determines that it is not a hydrogen flame, and the process returns to before step S21. It then reads the hydrogen flame observation value E1 and the non-hydrogen flame observation value E2 for the next 2 seconds and performs the same process according to the flowchart.

[0138] [g. Modifications of the Invention] Modifications of the hydrogen flame detection device and hydrogen station according to the present invention will be described below. In addition to the embodiments described above, the hydrogen flame detection device and hydrogen station of the present invention include the following modifications.

[0139] (Monitoring Area) In the above embodiment, the hydrogen flame detection device is installed targeting a hydrogen station, but it is not limited to this. The hydrogen flame detection device is installed so that the monitoring area includes any area where hydrogen is handled and where hydrogen flames may be generated.

[0140] (Hydrogen Station) In the above embodiment, the hydrogen station was an on-site hydrogen station, but it may also be an off-site hydrogen station that does not have hydrogen production facilities, or it may be an attached hydrogen station that is installed alongside a gasoline or other fueling station.

[0141] Furthermore, in the above embodiment, the hydrogen flame detection device was installed at the hydrogen station targeting the dispenser 112 that supplies hydrogen to the vehicle. However, the invention is not limited to this, and hydrogen flame detection devices may be installed in other locations where there is a high possibility of hydrogen leakage and hydrogen flame generation, such as hydrogen production facilities and storage facilities, as monitoring areas. The number of hydrogen flame detection devices installed at the hydrogen station is not limited to one.

[0142] (Determination of Correlation between Signal Waveform and Frequency Characteristics) In the above embodiment, in the first embodiment of hydrogen flame determination, the correlation between the signal waveform and frequency characteristics of the hydrogen flame observed value (first received signal) and the non-hydrogen flame observed value (second received signal) is determined by dividing the observed values ​​for a predetermined period into multiple time intervals and determining the correlation from the ratio of the integral values ​​in the same time interval. However, the determination is not limited to the ratio of the integral values, and may be made using an appropriate value such as the correlation coefficient of the observed values.

[0143] (Light received by the hydrogen flame detection device) In the above embodiment, the hydrogen flame detection device received infrared light in a narrowband wavelength band with a center wavelength of 1.5 μm in order to receive infrared light in the range of approximately 1.3 to 1.7 μm emitted from the hydrogen flame as light in the characteristic wavelength band specific to hydrogen flames. However, it is not limited to this, and the hydrogen flame may also be detected by receiving light in wavelength bands corresponding to ultraviolet light of 278 to 320 nm, infrared light of 925 to 1000 nm, or infrared light of 1.8 μm to 2.1 μm, which have characteristic peaks in the spectral spectrum of light emitted from the hydrogen flame. Furthermore, the hydrogen flame detection device received infrared light in a narrowband wavelength band with a center wavelength of 2.3 μm as light in a wavelength band different from the characteristic wavelength band, but it is not limited to this, just like the light in the characteristic wavelength band.

[0144] (Hydrogen flame detection device that receives light in a characteristic wavelength band) In the above embodiment, the hydrogen flame detection device detected the hydrogen flame by receiving light of two wavelengths, one in a characteristic wavelength band and the other in a different wavelength band. However, it is not limited to this, and the device may also detect the hydrogen flame by receiving light of one wavelength in the characteristic wavelength band.

[0145] Furthermore, the hydrogen flame detection method is not limited to the first and second embodiments described above. Any suitable hydrogen flame detection method can be used as long as it is capable of determining the light in the characteristic wavelength band specific to hydrogen flames and the frequency characteristics that include a frequency component of 3 to 5 Hz specific to hydrogen flames.

[0146] Furthermore, the present invention includes appropriate modifications that do not impair its purpose and advantages, and is not limited by the numerical values ​​shown in the above embodiments. For example, the values ​​indicating wavelength and wavelength band, and the values ​​indicating frequency and frequency band, as exemplified in the above embodiments, may be values ​​near the exemplified values, as long as they do not impair the purpose and advantages of the present invention.

[0147] 10: Hydrogen flame detection device 12: First light receiving unit 14: Second light receiving unit 15: Control unit 1510, 1512: A / D conversion port 16: Translucent window 18: First light receiving section 22: Second light receiving section 1810, 2210: Optical wavelength filter 1812, 2212: Light receiving element section 20, 24: Amplification circuit section 2010, 2410: Pre-filter 2012, 2412: Preamplifier 2014, 2414: Main amplifier 2016, 2416: Final stage amplifier 26: Buffer memory 28: Hydrogen flame determination unit 100: Hydrogen station 102: Firewall 104: Hydrogen production area 105: Raw fuel tank 106: Hydrogen production equipment 108: Compressor 110: Storage equipment 112: Dispenser 114: Filling hose 115: Roof 116: Office 118: Receiver 120: Transmitter 124: Vehicle

Claims

1. A hydrogen flame detection device for detecting a hydrogen flame based on light from a hydrogen flame, comprising: a first light receiving unit that receives light in a characteristic wavelength band specific to the hydrogen flame contained in the light from the hydrogen flame; and a hydrogen flame determination unit that detects the hydrogen flame based on the signal level and frequency characteristics of a first received signal obtained from the light in the characteristic wavelength band received by the first light receiving unit.

2. A hydrogen flame detection device according to claim 1, wherein the first light receiving unit receives infrared light in a predetermined wavelength band, including wavelengths included in the 1.3 to 1.7 μm wavelength band, as light in the characteristic wavelength band.

3. A hydrogen flame detection device according to claim 1, wherein the hydrogen flame determination unit detects the hydrogen flame based on a frequency characteristic of the first light receiving signal, which includes frequencies of 3 to 5 Hz.

4. A hydrogen flame detection device according to claim 1, further comprising a second light receiving unit that receives light of a wavelength band different from the characteristic wavelength band from the hydrogen flame, wherein the hydrogen flame determination unit detects the hydrogen flame based on a first light receiving signal obtained from light of a wavelength band different from the characteristic wavelength band received by the second light receiving unit, in addition to a first light receiving signal obtained from light of the characteristic wavelength band received by the first light receiving unit.

5. A hydrogen flame detection device according to claim 4, wherein the first light receiving unit receives infrared light in a predetermined wavelength band including wavelengths in the 1.3 to 1.7 μm wavelength band as light in the characteristic wavelength band, and the second light receiving unit receives infrared light in a predetermined wavelength band including 2.3 μm as light in a wavelength band different from the characteristic wavelength band.

6. A hydrogen flame detection device according to claim 4, wherein the hydrogen flame determination unit determines whether or not it is a hydrogen flame and detects the hydrogen flame based on: a first hydrogen flame determination condition based on the signal level of the first received light signal; a second hydrogen flame determination condition based on the correlation of the signal waveforms of the first received light signal and the second received light signal; and a third hydrogen flame determination condition based on the correlation of the frequency characteristics of the first received light signal and the second received light signal.

7. A hydrogen flame detection device according to claim 6, wherein the hydrogen flame determination unit calculates the integral value of the first light-receiving signal for a predetermined period of time, determines that the first hydrogen flame determination condition is satisfied when the integral value of the first light-receiving signal is equal to or greater than a predetermined threshold or exceeds the predetermined threshold, divides the first light-receiving signal and the second light-receiving signal for the predetermined period of time into a plurality of time intervals, calculates the integral value of the first light-receiving signal and the second light-receiving signal in each time interval, determines that the second hydrogen flame determination condition is satisfied when all ratios of the integral value of the first light-receiving signal and the integral value of the second light-receiving signal in the same time interval are within a predetermined threshold range, A hydrogen flame detection device characterized by dividing the first and second received light signals for a predetermined period into a plurality of time intervals, generating frequency spectra that include at least 3 to 5 Hz frequencies of the first and second received light signals in each time interval, calculating the integral values ​​of the frequency spectra of the first and second received light signals in each time interval, and determining that the third hydrogen flame determination condition is satisfied if all ratios of the integral values ​​of the frequency spectra of the first and second received light signals in the same time interval are within a predetermined threshold range.

8. A hydrogen flame detection device according to claim 4, wherein the hydrogen flame determination unit determines whether or not it is a hydrogen flame and detects the hydrogen flame based on a first hydrogen flame determination condition based on the signal level of the first received light signal, a second hydrogen flame determination condition based on the signal levels of the first received light signal and the second received light signal, and a third hydrogen flame determination condition based on the frequency characteristics of the first received light signal.

9. A hydrogen flame detection device according to claim 8, wherein the hydrogen flame determination unit calculates the integral value of the first received light signal for a predetermined period of time, determines that the first hydrogen flame determination condition is satisfied when the integral value of the first received light signal is equal to or greater than a predetermined threshold or exceeds the predetermined threshold, calculates the integral values ​​of the first received light signal and the second received light signal for a predetermined period of time, determines that the second hydrogen flame determination condition is satisfied when the ratio of the integral value of the first received light signal to the integral value of the second received light signal satisfies a predetermined threshold condition, generates a frequency spectrum of the first received light signal for a predetermined period of time that includes at least 3 to 5 Hz frequencies, divides the frequency spectrum into a low-frequency spectrum and a high-frequency spectrum that include 3 to 5 Hz, calculates the integral values ​​of the low-frequency spectrum and the high-frequency spectrum, and determines that the third hydrogen flame determination condition is satisfied when the ratio of the integral value of the low-frequency spectrum to the integral value of the high-frequency spectrum satisfies a predetermined threshold condition.

10. A hydrogen flame detection device according to claim 6, wherein the hydrogen flame determination unit determines that a hydrogen flame is present and detects the hydrogen flame when all of the first to third hydrogen flame determination conditions are met.

11. A hydrogen flame detection device according to claim 6, wherein the hydrogen flame determination unit determines that a hydrogen flame is present and detects the hydrogen flame when all of the first to third hydrogen flame determination conditions are satisfied and the number of times at least one of the first to third hydrogen flame determination conditions has been satisfied reaches a predetermined number of accumulations.

12. A hydrogen station comprising the hydrogen flame detection device described in claim 1, characterized in that the hydrogen flame detection device is installed such that the area in which hydrogen leakage may occur is included in the monitoring area.

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