JP2007309855A - High-speed gas leakage detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect leakage at a high speed, when hydrogen gas or the like is leaked, since monitoring can be performed at high time resolution using ultrasonic waves. <P>SOLUTION: A high-speed gas leakage detector for detecting the leakage of a second gas, by containing at least a first gas between an ultrasonic transmission element and an ultrasonic receiving element, propagating the ultrasonic wave through a detected gas having the possibility of being contained in the second gas to detect the leakage and measuring the propagated ultrasonic intensity by the ultrasonic-receiving element comprises measuring 100% of the first gas by the ultrasonic-receiving element; and detecting the leakage of the second gas by the difference between the measured value and a measured value of the detected gas. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high-speed gas leak detector that detects a gas leak at high speed, and in particular, a high-speed hydrogen gas leak that can measure a gas such as hydrogen leaked from a hydrogen utilization device such as a fuel cell with high time resolution. It relates to detectors.

There are the following means for measuring hydrogen which are conventionally used.
(1) Hydrogen storage alloy hydrogen measurement using the electrical characteristics of the alloy when storing hydrogen (see cited document 1).
(2) Measurement of the amount of light reflected on the surface of the hydrogen storage metal using the fact that some of the hydrogen storage alloys have different light absorption rates depending on the presence or absence of hydrogen (see cited document 2).
(3) Acoustic characteristic measurement that captures changes in the environment by measuring the acoustic characteristics of the surface acoustic waves of the hydrogen-sensitive membrane (see cited document 3).
JP 2004-327675 A Japanese Patent Laid-Open No. 04-8936 JP 2004-108236 A

  By the way, tanks filled with hydrogen gas are expected to be used in fuel cells, hydrogen gas vehicles, etc. in the near future, but hydrogen leaks from the tank into the atmosphere due to tank corrosion and destruction. Then, the diffusion speed of the flame is extremely high, and safety will become a big problem in the near future.

  For example, in a fuel cell, hydrogen gas is stored in a tank at a high pressure of 75 M Pascal (about 750 atm). If the tank breaks down due to corrosion caused by such underground deposits or an accident when it is mounted on a car, and hydrogen gas leaks into the atmosphere, the diffusion rate of the flame is extremely high, which is extremely important for safety. It is a problem.

  In order to prevent such an accident, it is necessary to detect leaking hydrogen at an extremely high speed. However, none of the conventional hydrogen measuring means can detect the hydrogen concentration in milliseconds. In addition, it is necessary to detect and take measures against such leaks before an accident occurs, but there is no existing hydrogen sensor suitable for the response.

  An object of the present invention is to realize a high-speed gas leak detector that enables monitoring with high time resolution (that is, to detect hydrogen leak at a high speed of 1 millisecond or less) when hydrogen gas leaks. .

  In order to solve the above-described problems, the present invention provides a detection gas that includes at least a first gas and a second gas that should be detected for leakage between the ultrasonic transmission element and the ultrasonic reception element. A high-speed gas leak detector for detecting a leak of a second gas by propagating an ultrasonic wave through and measuring the magnitude of the propagated ultrasonic wave with the ultrasonic wave receiving element, A high-speed gas leak detector is provided, wherein 100% gas is measured by the ultrasonic receiving element, and leakage of the second gas is detected based on a difference between the measured value and the measured value of the detected gas.

  A supply pipe is attached to the sensor having the ultrasonic oscillation element and the ultrasonic reception element, and a first supply pipe for passing the detection gas is connected to the supply pipe via a first valve, and A high-speed gas leak detector, wherein a second supply pipe through which the detection gas is passed is connected through a valve (2).

  According to the high-speed gas leak detector according to the present invention, it is possible to monitor with high time resolution. Therefore, when hydrogen gas or the like leaks, the leak can be detected at high speed.

  The best mode for carrying out the high-speed gas leak detector according to the present invention will be described below with reference to the drawings based on the embodiments.

(Ultrasonic gas concentration meter)
The high-speed gas leak detector according to the present invention measures a change in the concentration of a gas such as hydrogen at a high speed and detects the leak of the gas at a high speed, and uses an ultrasonic gas concentration meter as its principle. Therefore, first, the ultrasonic gas concentration meter will be described.

  FIG. 1 is a diagram showing a configuration of an ultrasonic gas concentration meter 1 applied to measuring the molecular concentration of gas in a chamber. The sensor 2 forming the main body of the ultrasonic gas concentration meter 1 has a chamber 12. The gas flow 10 flows in the direction of the arrow 14 in the chamber 12. An ultrasonic transmission element 16 is provided on one of the left and right side walls of the chamber 12 with respect to the flow of the gas flow 10, and an ultrasonic reception element 18 is provided on the other measurement wall so as to face the ultrasonic transmission element 16. ing.

  The distance between the ultrasonic transmission element 16 and the ultrasonic reception element 18 is kept constant. The ultrasonic wave transmitted from the ultrasonic transmission element 16 propagates or passes through the gas flow 10 in the direction indicated by the arrow 20 and is received by the ultrasonic reception element 18. The ultrasonic wave propagating through the gas flow 10 propagates between the ultrasonic transmitting element 16 and the ultrasonic receiving element 18. A part of the ultrasonic wave appears as a reception signal on the ultrasonic receiving element 18, and a part of the ultrasonic wave is reflected on the surface of the ultrasonic receiving element 18 and returns toward the ultrasonic transmitting element 16.

  At this time, the ultrasonic wave is also reflected on the surface of the ultrasonic transmission element 16, and by repeating this reflection, a steady state of ultrasonic waves is generated between the ultrasonic transmission element 16 and the reception element 18. In this steady state, a phenomenon in which the antinodes and nodes of the ultrasonic wave are called a multi-wave interference pattern appears between the ultrasonic transmission element 16 and the ultrasonic reception element 18.

  In this ultrasonic gas concentration meter, the molecular composition ratio of the gas composing the gas flow 10 (concentration of mixed gas of constituent gases, for example, about 80% is nitrogen for air, and 20% is for the remaining oxygen and rare gases. This phenomenon utilizes the phenomenon that the shape of the multi-wave interference pattern changes. The influence of the multi-wave interference pattern on the molecular composition ratio of the gas appears as attenuation of the ultrasonic wave and phase difference. In the present invention, however, attention is paid to the phase difference shift which is more effective.

  Accordingly, the magnitude of the ultrasonic wave received by the ultrasonic receiving element 18 is measured in advance using the gas flow 10 containing nitrogen gas having various known molecular concentrations, and the measured ultrasonic magnitude and the nitrogen gas are measured. If the relationship (or conversion) between the molecular concentration of the gas and the gas flow 10 including the molecular concentration of the nitrogen gas mixed with the unknown gas is calibrated, the magnitude of the ultrasonic wave received by the ultrasonic receiving element 18 will be described. Then, the molecular concentration of the nitrogen gas mixed with the unknown gas can be determined using the calibration.

  Further, the change in the molecular concentration of the nitrogen gas can be obtained by measuring the temporal change in the magnitude of the ultrasonic wave received by the ultrasonic receiving element 18 without being calibrated in advance.

  A specific configuration of the ultrasonic oscillator 16 of FIG. 1 is shown as an ultrasonic generation circuit 30 of the ultrasonic gas concentration meter 1 in FIG. The ultrasonic generation circuit 30 includes an electric signal oscillation unit 32 and an ultrasonic oscillation unit 34.

  The electric signal oscillating unit 32 includes an oscillation / frequency dividing circuit 36 having an oscillation and frequency dividing function, a resistance group 38, and a switch group 40 that selects a resistance of the resistance group 38 and designates a frequency division ratio. The ultrasonic oscillator 34 includes an ultrasonic transducer 42.

  FIG. 3 shows the configuration of the ultrasonic wave reception and molecular concentration output circuit 50. FIG. 4 shows the states of the ultrasonic waves transmitted from the ultrasonic wave generation circuit 30 of FIG. 2 and signals in the main part of the ultrasonic wave reception and molecular concentration output circuit 50 of FIG.

  The circuit shown in FIG. 3 will be described with a focus on the operation as needed, together with FIG. 4A and 4B show ultrasonic waves, the form converted into an electric signal, that is, its amplitude is indicated by voltage.

  From the ultrasonic transducer 42 of the ultrasonic transmission unit 34 in the ultrasonic generation circuit 30, a sinusoidal ultrasonic wave 70 with very little noise component, as shown in FIG. 4A, is transmitted. When the ultrasonic wave 70 propagates through the gas flow 10 shown in FIG. 1, a received wave 72 having a smaller magnitude than the ultrasonic wave 70 is attenuated by the gas flow 10, and the ultrasonic wave reception and molecular concentration output circuit 50. Is received by the ultrasonic transducer 64 of the ultrasonic receiver 52.

  Since the molecular weight of the gas flow 10 fluctuates with time, the fluctuation component is superimposed on the waveform of the received wave 72 as shown in FIG.

  The ultrasonic reception wave 72 received by the ultrasonic transducer 64 of the ultrasonic reception 52 is converted into an electric signal by the ultrasonic reception unit 52, the fluctuation component is removed by the high pass filter 54, and then the amplification unit 56. Amplified. The increased electrical signal is half-wave rectified by the diode of the rectifier 58, and a waveform as shown in FIG. 4C is obtained.

  The half-wave rectified electrical signal is peak-held at the peak hole portion 60, and a waveform 76 as shown in FIG. 4D is obtained at the output (point A shown in FIG. 3) of the peak hole portion 60. It is done. The peak voltage of the waveform 76 represents the magnitude of the amplitude of the received ultrasonic wave 72 and thus represents the concentration (or average molecular weight) of the gas to be measured in the gas stream 10.

  3 determines when the peak voltage value of the waveform 76 exceeds a predetermined threshold voltage (corresponding to a predetermined threshold concentration of the measurement target gas included in the gas flow 10). Information that informs that the gas to be measured is present more than a predetermined threshold concentration is output on / off, and the determination unit 62 can be arbitrarily provided depending on the application.

  FIG. 5 is a diagram for explaining the basic configuration of the high-speed gas leak detector according to the present invention. An inflow pipe 80 that uses the ultrasonic gas concentration meter 1 shown in FIG. 1 and flows gas toward the interval between the ultrasonic transmission element 16 and the ultrasonic reception element 18 of the sensor 2 in the ultrasonic gas concentration meter 1, and Outflow pipes 81 discharging from this interval are respectively attached to the chambers 12 (see FIG. 1).

  A supply pipe 83 that supplies 100% nitrogen-containing gas as a reference gas is attached to the inflow pipe 80 via a valve 85, and a supply pipe 84 that supplies nitrogen gas containing H 2 gas is attached via a valve 86. It has been. On the other hand, the discharge pipe 81 is provided with a suction pump 87 and a flow meter 89.

  A pump 87 that sucks gas at a constant flow rate sucked 100% nitrogen-containing gas, and measured attenuation of ultrasonic waves when switching to nitrogen gas containing hydrogen from the middle. Curve a in FIG. 6 shows the result of measuring the attenuation of ultrasonic waves when a gas containing 100% nitrogen as a reference gas is sucked and switched to nitrogen gas containing 4% hydrogen. 6 shows the result of measuring the attenuation of the ultrasonic wave when the gas containing 100% nitrogen was sucked and switched to the nitrogen gas containing 1% hydrogen from the middle.

  In FIG. 6, switching to hydrogen-containing nitrogen starts at time 0, and after a delay of a few seconds, when hydrogen-containing nitrogen gas begins to pass in front of the sensor, attenuation of ultrasonic waves is recognized, and hydrogen containing from 100% nitrogen containing gas The knowledge that a change to nitrogen gas occurs was obtained.

  In FIG. 6, the S / N ratio is approximately 55.4 dB when compared with the response of nitrogen alone in the nitrogen containing 4%, and the S / N ratio of 50.42 dB is observed for the hydrogen containing 1%. The knowledge that a slight hydrogen leak can be measured stably was obtained.

  This S / N ratio was basically calculated by S / N = 20 * log (Signal / SD). For Signal, the voltage at 1000 msec and the voltage difference at 5000 msec in each percentage were defined as Signal. The standard deviation of 1000 points of data near 1000 msec was used. About 50 dB means that the signal / noise ratio is about 100 times and the detection signal of 1% hydrogen is 100, and there is only about 1 noise.

(Application example)
The above high-speed gas leak detector is used in the vicinity of a place where there is a possibility of gas leakage (for example, a fuel cell, a junction between a tank and a pipe, or a valve). As the configuration, the following configuration is conceivable.

  In FIG. 5, the tip of the supply pipe 84 opens to a region where hydrogen is likely to leak, and the valve 86 is normally kept open. Thereby, it is set as the structure which can take in into the sensor 2 the detection gas which may contain the hydrogen which should contain the hydrogen which should detect leakage further at least by nitrogen.

  The supply pipe 83 can be connected to a supply source of a gas containing 100% nitrogen as necessary, and the valve 85 is always closed. Here, the supply source of the 100% nitrogen-containing gas is necessary for obtaining the detection output (reference output) for the 100% nitrogen-containing gas in the high-speed gas leak detector, and is mounted (or attached as necessary) It is a tank that stores a gas containing 100% nitrogen that can be always mounted).

  The ultrasonic receiving element has output means including the receiving unit 52, the bypass filter 54, the amplifying unit 56, the rectifying unit 58 and the like shown in the molecular concentration output circuit 50 described in FIG. And it connects to the memory | storage device which memorize | stores the output obtained when connected to the supply source of 100% nitrogen containing gas.

  Furthermore, a comparator is provided for comparing the output when the gas containing 100% nitrogen stored in the storage device is detected with the detection output of the gas to be detected, and determining whether there is hydrogen leakage. The comparator is connected to notification signal generating means for notifying the determination result.

  FIG. 7 is a diagram showing a specific application example of the high-speed gas leak detector according to the present invention. The high-speed gas leak detector according to the present invention is used as a place where there is a possibility of gas leakage. It is the structure applied to the junction part.

  In FIG. 7, the sample collection port of the pipe 91 is opened toward the joint between the tank 89 and the pipe 90 via the valve 92. On the other hand, a reference gas (for example, air) inlet of the pipe 91 opens to the opposite side of the leaking point via the valve 93.

  The sensor 2 is provided in the inflow pipe 94 branched from the pipe 90 between the valves 92 and 93. By alternately switching the valves 92 and 93 and sucking them by the vacuum suction pump 95, the sensor 2 is leaked. Or a reference gas can be introduced. By comparing the components of both gases introduced in this way, the gas leaking from the joint between the tank 89 and the pipe 90 can be detected.

  As described above, the best mode for carrying out the high-speed gas leak detector according to the present invention has been described based on the embodiments. However, the present invention is not limited to such embodiments, and is described in the claims. It goes without saying that there are various embodiments within the technical scope.

  The present invention is configured as described above, and hydrogen leakage can be stably measured. Therefore, in an energy generation power device using hydrogen fuel, such as a fuel cell or a hydrogen automobile, leakage of hydrogen gas into the atmosphere can be accurately performed. Therefore, these devices are extremely useful.

  In particular, hydrogen gas is stored in a tank at a high pressure of 75 M Pascal (about 750 atm). If the tank breaks down due to corrosion caused by such underground deposits or accidents when installed in automobiles, and hydrogen gas leaks into the atmosphere, the flame diffusion rate is extremely high and safety Will be a big problem in the near future.

  Although it is necessary to detect and take measures against such leaks before an accident occurs, there is no existing hydrogen sensor that is suitable for responsiveness. The market value is extremely high as an ultra-high-speed hydrogen leak sensor for preventing the above-mentioned problem.

It is a figure explaining the ultrasonic gas concentration measuring method this invention used as the object of the optimization method of the ultrasonic gas concentration measuring method which concerns on this invention. It is a figure which shows the ultrasonic wave generation circuit of an ultrasonic gas concentration meter. It is a figure which shows the molecular concentration output circuit of an ultrasonic gas concentration meter. It is a figure which shows the signal in the transmission wave and molecular concentration output circuit of an ultrasonic wave generation circuit. It is a figure which shows the high-speed gas leak detector based on this invention. It is a figure which shows the measurement result of a high-speed gas leak detector. It is a figure which shows the specific example of application of the high-speed gas leak detector of this invention.

Explanation of symbols

1 Ultrasonic gas concentration meter 2 Sensor 10 Gas flow
12 Chamber
14 arrows
16 Ultrasonic transmitter
18 Ultrasonic receiver
20 arrows
30 Ultrasonic generator
32 Electric signal oscillator
34 Ultrasonic oscillator
36 Oscillator / Divider Circuit
38 resistance group
42 Ultrasonic vibrator
50 Molecular concentration output circuit
52 Ultrasonic receiver
54 High-pass filter
62 Judgment part
56 Amplifier
58 Rectifier
60 Peak Hall
64 Ultrasonic transducer
72 Received ultrasound (received wave)
76 waveforms
80, 94 Inflow pipe
81 Outflow pipe
83, 84 Supply pipe
85, 86, 92, 93 valves
87, 95 Vacuum suction pump
88 Flow meter 89 Tank 90 Piping

Claims (2)

The ultrasonic wave is propagated between the ultrasonic transmitting element and the ultrasonic receiving element through a detection gas that includes at least the first gas and may also include the second gas to be detected for leakage. A high-speed gas leakage detector that detects leakage of the second gas by measuring the size of the ultrasonic wave with the ultrasonic receiving element,
A high-speed gas leak detector that measures 100% of the first gas with the ultrasonic receiving element and detects a leak of the second gas based on a difference between the measured value and the measured value of the detected gas. .   A supply pipe is attached to the sensor having the ultrasonic oscillation element and the ultrasonic reception element, and a first supply pipe for passing the detection gas is connected to the supply pipe via a first valve, and A high-speed gas leak detector, wherein a second supply pipe through which the detection gas is passed is connected through a valve (2).

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