JP2005227127A - System for determining gas leak - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas leak detection system which performs gas leak detection in a short time and without errors, even if there are variations and malfunctions in the regulator and the cutoff valve. <P>SOLUTION: The gas leak detection system for detecting gas leak in a gas circulation system comprises monitoring means (P2, 20) which cut off gas circulation in sections to be inspected (SV2 to SV3), which are the objects to be inspected concerning gas leak, and monitor the amount of state change of a gas in a transient state in the sections to be inspected, and inspection means (20) which performs gas leak inspection in the sections to be inspected, when the amount of state change of the gas becomes equal to or lower than a predetermined value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell system, and more particularly to an improvement in a gas leak detection method for detecting a gas leak of fuel gas.

  As a method for detecting hydrogen gas leak in a fuel cell system, for example, as described in JP-A-8-329965, a stop valve and a stop valve are provided upstream and downstream of the fuel cell, and power generation operation is started. Previously, the fuel gas was sealed and the pressure change was detected by the pressure notification means, and the occurrence of leakage was detected from the drop in the sealing pressure (Patent Document 1). Further, in the method described in Japanese Patent Laid-Open No. 10-103547, a predetermined time is measured by a standby timer after the predetermined time when the pressure due to valve opening and closing becomes stable, and then the pressure is measured. Leakage determination was performed by measuring (Patent Document 2).

The greater the amount of gas leakage, the lower the sealing pressure. Therefore, it was possible to detect the presence of gas leakage by such a method.
JP-A-8-329965 Japanese Patent Laid-Open No. 10-103547

  However, there are variations in the response speed of regulators and shutoff valves, and there may be a case where valve closing failure occurs. Immediately after valve closing, the pressure of the enclosed gas is not stable, and such an unstable state If gas leak detection is performed, there is a possibility of false detection. On the other hand, in the known technology of Patent Document 2 that provides a waiting time for a certain period in order to deal with such a situation, it is necessary to set a waiting time with an allowance, so a wasteful waiting time may occur. Rapid measurement was not possible. Further, even when the pressure is not stable for a long time due to poor valve closing, the gas leakage determination is performed, and an erroneous determination may occur.

  Therefore, in view of such a problem, the present invention provides a gas leak determination device capable of detecting a gas leak in as short a time as possible without error even if there are variations or malfunction of regulators and shut-off valves. The purpose is to provide.

  In order to solve the above problems, the present invention is a gas leak determination device for detecting a gas leak in a gas distribution system, which interrupts the gas flow in an inspection target section to be inspected for a gas leak, and A monitoring unit that monitors a state change amount in a transition state of the gas in the section, and an inspection unit that performs a gas leak inspection in the inspection target section when the gas state change amount becomes a predetermined value or less. It is characterized by.

  When the gas handling system shuts off the gas flow in a specific inspection section due to gas leakage judgment or other reasons, the gas condition becomes stable due to the response characteristics of the pressure regulating valve and shutoff valve and the nature of the gas. A transition period occurs in which the gas state continues to change. According to the above configuration, after the monitoring means monitors this state change and detects that the amount of state change has become a predetermined value or less, that is, has detected that the transient state transition has converged to such an extent that gas leakage can be measured. A gas leak test is performed. For this reason, gas leak inspection can be performed as soon as the state change in the transition period is completed, so there is no wasteful waiting time, and erroneous detection due to gas leakage inspection during the state change in the transition period is prevented. it can.

  Here, the “gas distribution system” is a system that distributes any gas (fuel gas such as hydrogen and propane, mixed gas such as air), and it is necessary to determine gas leakage from the safety and environmental considerations. Say.

  In addition, “inspection section” refers to a section of the system in which it is desired to check for gas leaks, and includes a section of pure piping and includes one or more members (pumps, batteries, valves, etc.). Including a wide range of sections. For example, this section is blocked by a pressure regulating valve or a shut-off valve.

  Further, the “state change amount” is an index capable of quantifying a transient change related to the shutoff of the gas, and includes, for example, a pressure change amount and a flow rate change amount, but there is no limitation.

  Here, the monitoring in the present invention is performed during the system stop period in the intermittent operation of the gas distribution system. For example, intermittent operation is performed in a fuel cell system. If the gas leakage determination of the present invention is performed during the system outage during the intermittent operation, the system outage period can be used effectively.

  In the present invention, in the monitoring, when the gas leakage inspection cannot be executed for a certain time or more, the abnormality process is executed. If a gas leak of a certain level or more has occurred, if the gas state change in the present invention is monitored, the gas pressure will continue to drop indefinitely, and the gas leak inspection itself cannot be entered. In this regard, according to this configuration, even if the gas state change continues for many hours due to gas leakage, the abnormality is detected as having detected an abnormality after a certain period of time has passed and the abnormality processing has occurred. Yes.

  According to the present invention, since the monitoring means monitors the gas state change and detects that the amount of state change is equal to or less than the predetermined value, the gas leak inspection is executed, so that the state change in the transient period ends. As soon as the gas leak inspection can be performed, there is no wasteful waiting time and it is quick. Further, it is possible to prevent erroneous detection due to a gas leak inspection being performed during a state change during the transition period.

  Next, preferred embodiments for carrying out the present invention will be described with reference to the drawings.

  In the embodiment of the present invention, the gas leak determination device of the present invention is applied to a fuel cell system mounted on a moving body such as an electric vehicle. The following embodiment is merely one embodiment of the present invention, and the present invention is not limited thereto and can be applied. The case of hydrogen gas is illustrated as the gas subject to the leak determination of the present invention.

  FIG. 1 shows an overall system diagram of the fuel cell system. As shown in FIG. 1, the fuel cell system includes a system for supplying hydrogen gas as fuel to the fuel cell stack 10, a system for supplying air, and a system for cooling the fuel cell stack 10. It is prepared for.

The fuel cell stack 10, a hydrogen gas, air, and a separator having a flow path of the cooling water, MEA sandwiched by a pair of separators (M embrane E lectrode A ssembly) stacked and configured cells from the stacks structure It has. The MEA has a structure in which a polymer electrolyte membrane is sandwiched between two electrodes, a fuel electrode and an air electrode. The fuel electrode has a fuel electrode catalyst layer provided in the form of a porous support layer, and the air electrode has an air electrode catalyst layer provided on the porous support layer.

  A system for supplying hydrogen gas to the fuel cell stack 10 is a fuel cell through a hydrogen tank 11, a main valve SV1, a pressure regulating valve RG, a fuel cell inlet shut-off valve SV2, and the fuel cell stack 10 in order from the hydrogen gas supply source. An outlet cutoff valve SV3, a gas-liquid separator 12 and a cutoff valve SV4, a hydrogen pump 13, a purge cutoff valve SV5, and a check valve RV are provided.

  In the present embodiment, the gas leakage determination in the inspection target section divided by the fuel cell inlet cutoff valve SV2 and the fuel cell outlet cutoff valve SV3 is illustrated, but the inspection target section is between the main valve SV1 and the pressure regulating valve RG, and the pressure regulating valve. The same inspection can be performed between the RG and the fuel cell inlet cutoff valve SV2 and between the fuel cell outlet cutoff valve SV3 and the hydrogen pump 13.

  The pressure sensor P1 detects the pressure between the main valve SV1 and the pressure regulating valve RG. The pressure sensor P2 detects the pressure between the fuel cell inlet cutoff valve SV2 and the fuel cell outlet cutoff valve SV3 (internal pressure of the fuel cell stack 10), and the temperature sensor T1 detects the temperature in that section. The pressure sensor P3 detects the pressure between the fuel cell outlet cutoff valve SV3 and the hydrogen pump 13 inlet.

  The hydrogen tank 11 is a high-pressure hydrogen tank. Instead of the high-pressure hydrogen tank, a hydrogen tank using a hydrogen storage alloy, a hydrogen supply mechanism using a reformed gas, a tank for supplying hydrogen from a liquid hydrogen tank, a liquefied gas fuel A storage tank or the like is applicable.

  The main valve SV1 controls the presence or absence of hydrogen gas supply from the hydrogen tank 11. The fuel cell inlet shut-off valve SV2 is shut off at the time of gas leak determination in the section to be inspected up to the original valve SV1 up to the pressure regulating valve RG upstream of the shut-off valve SV2 and further when the pressure regulating valve RG is substantially opened. . The fuel cell outlet shut-off valve SV3 is shut off from the shut-off valve SV3 to the fuel cell inlet shut-off valve SV2, that is, when a gas leak is determined when the inside of the fuel cell stack 10 is an inspection target section. The gas-liquid separator 12 removes moisture and other impurities generated by the electrochemical reaction of the fuel cell stack 10 during normal operation from the hydrogen off-gas and discharges them to the outside through the shut-off valve SV4. The hydrogen pump 13 forcibly circulates hydrogen gas in a hydrogen gas circulation path that passes through the shut-off valves SV2, SV3 and the check valve RV. The purge shut-off valve SV5 is opened at the time of purging, but is shut off at the time of normal operation and gas leak determination of the present invention. The check valve RV prevents the backflow of hydrogen gas. The hydrogen off gas purged from the purge shutoff valve SV5 is processed in an exhaust system including a diluter (not shown).

  As a system for supplying air to the fuel cell stack 10, an air cleaner 21, a compressor 22, a humidifier 23, and the like are provided. The air cleaner 21 purifies the outside air and takes it into the fuel electric system. The compressor 22 changes the amount of air and the air pressure supplied by compressing the introduced air according to the control of the control unit 20. The humidifier 23 adds an appropriate humidity to the compressed air by exchanging air off-gas and moisture. The air off-gas discharged from the fuel cell stack 10 is diluted in a diluter (not shown) and the hydrogen off-gas from the purge control valve SV5 is diluted and discharged to the exhaust system.

  The cooling system of the fuel cell stack 10 includes a radiator 11, a fan 12, and a cooling pump 13, and cooling water is circulated and supplied into the fuel cell stack 10.

  The control unit 20 is a known computer system such as an ECU, and may be configured by mutual communication of a plurality of computers. These computers can operate the system as the gas leak determination apparatus of the present invention by sequentially executing software programs stored in a built-in ROM or the like. That is, according to the procedure (FIG. 2) described later, the control unit 20 outputs a control signal for controlling the opening and closing of the valves SV1 to SV5 and a control signal for determining the driving amount of the hydrogen pump 13 and the compressor 22, and the pressure sensor. Gas leak determination is executed based on detection signals from P1 to P3.

  Next, a gas leak determination method in the present embodiment will be described with reference to the flowchart of FIG. The gas leak determination method in the flowchart is merely an example. Further, FIG. 3 shows how the flag is set and reset in the control unit 20 in relation to such a gas leak determination method, and the gas pressure and fuel by the pressure sensors P1 and P2 and the temperature sensor T1. The timing chart of how battery internal temperature Tfc changes is shown.

  The gas leak determination method shown in this flowchart is repeatedly executed periodically (for example, with a period T). All flags are reset in the initial system state.

  The following processing refers to two flags, an intermittent flag and a leakage determination condition flag. The former intermittent flag is a flag indicating whether or not the system should enter an intermittent operation suspension period. The latter leakage determination condition flag relates to the present invention and indicates whether or not the transient state occurring immediately after the valve means is closed has converged.

  First, the control unit 20 checks whether or not the intermittent flag is set (S1). If it is determined that the intermittent operation pause period has been entered due to the state of the intermittent flag (NO), the process does not proceed to the gas leakage determination process, but if it is determined that the intermittent operation suspension period has been entered ( YES), a shutoff / pause measure for each valve or pump is taken for the gas leak determination process (S2: time t0). The control unit 20 outputs various control signals, closes the shutoff valve SV1, stops the operation of the hydrogen pump 13, closes the fuel cell inlet shutoff valve SV2 and the outlet shutoff valve SV3, and closes the purge shutoff valve SV5. To do.

  As shown in FIG. 3, when the fuel cell inlet shutoff valve SV2 is closed, the gas supply from the hydrogen tank 11 is throttled according to the response characteristics of this valve, and the pressure on the downstream side of the main valve SV1 decreases. start. On the other hand, the pressure on the secondary side of the fuel cell inlet shutoff valve SV2 increases. It takes some time for these pressure states to stabilize.

  In the present embodiment, this transient state is monitored from the pressure change amount (S3). When the transient state ends, the leak judgment condition flag is set, but until then, it has been reset. If the leak determination condition flag is set (S3: YES), the control unit 20 performs a leak determination (S10), but if the leak determination condition flag is reset (S3: NO), hydrogen gas It is determined that it is during the period of monitoring the pressure change, and the process proceeds to the monitoring process.

  With reference to the detection signal from the pressure sensor P2, the control unit 20 detects the pressure p2 downstream of the fuel cell inlet shutoff valve SV2 (S4). Next, the difference between the pressure p2 'measured last time and the pressure p2 measured this time is calculated to calculate the pressure change amount Δp (S5). When the pressure is measured for the first time after entering the period of intermittent operation, it is calculated that the previously measured pressure p2 'is zero.

  As a result, when the pressure change amount Δp is equal to or less than the predetermined threshold value Pth (S6: YES), it means that the transient state is almost finished and the pressure has stabilized. Therefore, the control unit 20 sets a leak condition flag (S9) and permits the shift to the gas leak determination process. Here, the threshold value Pth is selected to be a value that can identify a pressure change rate that does not cause erroneous detection even if a gas leak determination is made.

  In FIG. 3, when the pressure change amount is Δp1, the pressure change is still in a transient state, and the pressure changes too rapidly to determine the gas leak determination. On the other hand, if the pressure change amount becomes Δp2, the pressure change becomes extremely slow, and it is possible to make a gas leak determination. The threshold value Pth is set so that such a pressure change state can be identified.

  If the leak determination condition flag is set and the gas leak determination is possible, the control unit 20 executes a known gas leak determination process (S10). If the gas leak determination is completed (S11: YES), a gas leak determination completion flag is set and the subsequent gas leak determination is prohibited (S12). If it is in the middle of the gas leak determination (S11: NO), it waits until the next routine execution timing.

  Now, since the gas leak rarely occurs and the scale thereof is large, there is a case where the pressure difference Δp, which is the difference between the pressure of the previous measurement calculated in step S6 and the pressure of the current measurement, does not decrease indefinitely. is there. That is, since gas leaks are continuously generated, the pressure of the pipe continues to decrease even after the valve is closed. In such a case, it can be determined that there is an abnormality without waiting for the gas leak determination in step S10.

  Therefore, the control unit 20 is a case where the pressure change amount Δp does not fall below the threshold value Pth (S6: NO), and when a certain time has elapsed since the start of monitoring (S7: YES). Then, abnormality processing is performed on the assumption that some kind of gas leakage continuously occurs (S8). Examples of the abnormality processing include lighting of a warning lamp, reduction of hydrogen gas pressure at the next restart of operation, or prohibition of operation start. If the pressure change amount Δp is larger than the threshold value Pth but the predetermined time has not yet passed (S7: NO), the monitoring is continued.

  Here, the fixed time is set to a time at which it is considered that the pressure will be sufficiently stabilized in a system having no abnormality. This time varies from system to system.

  In the above process, the pressure change monitoring process and the gas leak determination process based on the pressure change monitoring process are performed in one routine, but may be performed in separate routines.

  According to the present embodiment, as shown in the timing of the flag F0 in FIG. 3, the gas leakage can be performed as soon as the gas pressure change amount reaches the predetermined threshold value Pth by the monitoring process. Can be implemented without delay. For this reason, as shown in the flag F1, a gas leak determination is performed in a transient state where the pressure change is severe, and it is erroneously determined as a gas leak, or as shown in the flag F2 as in the prior art, wait for a certain waiting time Tw. Therefore, it is possible to prevent the gas leakage determination from being delayed by an excessive time Td after the gas leakage can be originally performed.

  Accordingly, since the gas leak can be determined as soon as the state change in the transition period is completed, there is no wasteful waiting time, and it is quick. Further, it is possible to prevent erroneous detection due to a gas leak inspection being performed during a state change during the transition period.

(Other embodiments)
The present invention can be applied with various modifications other than the above embodiment.

  For example, although the said embodiment was an example which applied the said gas leak determination apparatus to the fuel cell system, it is possible to apply this gas leak determination apparatus also to the system using gas other than a fuel cell.

  Further, the pressure change determination of the hydrogen gas is not limited to the pressure sensor, and the pressure determination may be performed with reference to a physical quantity (for example, temperature or water vapor amount) that changes according to the pressure level.

  Further, the gas state change is not limited to the pressure change, and other parameters such as a flow rate change can be detected.

  Also, the flowchart of FIG. 2 is merely an example, and the order and contents of processing determination can be variously changed depending on the system configuration.

1 is a block diagram of a fuel cell system according to an embodiment. The flowchart explaining the gas leak determination process which concerns on embodiment. Explanatory drawing of the pressure change in the gas leak determination process which concerns on embodiment.

Explanation of symbols

  SV1 ... main valve, SV2 ... fuel cell inlet shutoff valve, SV3 ... fuel cell outlet shutoff valve, SV4 ... shutoff valve, SV5 ... purge shutoff valve, RV ... check valve, RG ... pressure regulating valve, P1-P3 ... pressure sensor, DESCRIPTION OF SYMBOLS 10 ... Fuel cell stack, 20 ... Control part, 11 ... Hydrogen tank, 12 ... Air-water separator, 13 ... Hydrogen pump, 21 ... Air cleaner, 22 ... Compressor, 23 ... Humidifier, 31 ... Radiator, 32 ... Fan, 33 ... Cooling water pump

Claims (3)

A gas leak determination device for detecting a gas leak in a gas distribution system,
A monitoring means for interrupting the flow of gas in the inspection target section to be inspected for gas leakage, and monitoring the amount of state change in the transient state of the gas in the inspection target section;
A gas leakage determination device, comprising: an inspection unit that performs a gas leakage inspection in the inspection target section when the gas state change amount is equal to or less than a predetermined value.   The gas leakage determination device according to claim 1, wherein the monitoring is performed during a system stop period in intermittent operation of the gas distribution system. 3. The gas leak determination device according to claim 1, wherein in the monitoring, an abnormal process is executed when a gas leak inspection cannot be executed for a predetermined time or more.

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