JP2005353397A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system equipped with a hydrogen sensor that has a high reliability by preventing the hydrogen sensor from internal condensation. <P>SOLUTION: In the fuel cell system, a branch pipe 3 is branched from a main exhaust pipe 2 that exhausts a gas exhausted from a fuel cell to the outside, a cooling means 5 is installed for cooling a gas branched from the main exhaust pipe 2 into the branch pipe 3, a heating means 6 is installed in the branch pipe 3 at the downstream side of the cooling means 5 for heating a branched exhaust gas cooled with the cooling means 5, and the branched exhaust gas heated with the heating means 6 is conducted into a hydrogen sensor 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system that prevents dew condensation of a hydrogen sensor that detects hydrogen in a hot and humid exhaust gas exhausted from a fuel cell.

  Conventionally, as a technique for preventing condensation in a sensor that detects a high-temperature and high-humidity test gas, for example, those described in the following documents are known (see Patent Document 1). In the technique described in this document, a water repellent filter and a heating element are provided between a housing room in which a gas detection element for detecting a gas to be detected is housed and the outside, and the gas intake port passes through the water repellent filter. A high-temperature and high-humidity test gas is taken in, and the introduced high-temperature and high-humidity test gas is heated by a heating element and then reaches the gas detection element to prevent condensation.

In addition, a method has been conventionally proposed in which a heater for heating the sensor is wound around the entire sensor, or a heat insulating material is wound around the heater so that the temperature of the sensor is higher than that of the surroundings to prevent condensation.
JP2003-161712

  In a conventional sensor that detects a high-temperature and high-humidity test gas, the size of the gas detection element is very small, so that the amount of heat generated by the element itself is extremely small. For this reason, the heat generation effect of the element can hardly be expected for the periphery in the housing room in which the element is stored. Therefore, the temperature of the test gas is always higher than the temperature of the inner wall of the housing room. In such a state, the gas detection element does not condense due to its own heat generation, but when the hot and humid test gas is cooled by touching the inner wall of the housing room, it is avoided that the condensed water adheres to the inner wall of the housing room. It becomes impossible.

  When the inner wall of the housing room is condensed, the condensed water adhering to the inner wall may hang down around the gas detection element, and the condensed water may accumulate. When the condensed water touches an element that generates heat at a high temperature, there is a problem that the rapidly cooled element is damaged by thermal stress, for example, is disconnected.

  In the case of a hydrogen sensor that detects hydrogen in a hot and humid exhaust gas exhausted from the fuel cell system, the inner wall temperature of the housing room that houses the hydrogen sensor is introduced into the housing room immediately after the start of the fuel cell system. The exhaust gas temperature is lower. For this reason, there is a problem that condensation occurs on the inner wall of the housing room immediately after the system is started.

  Furthermore, when the hydrogen sensor is heated by an external heater that generates a large amount of heat so that the heating effect can be expected, only the surface of the heater becomes significantly hotter than the surroundings, causing damage to the circuit board of the hydrogen sensor. There was a risk of it.

  Accordingly, the present invention has been made in view of the above, and an object of the present invention is to provide a fuel cell system including a highly reliable hydrogen sensor that prevents condensation inside the hydrogen sensor. .

  In order to achieve the above object, the means for solving the problems of the present invention is to detect hydrogen contained in exhaust gas exhausted from a fuel cell that generates power by reacting hydrogen of a fuel gas with an oxidant gas. A sensor, a branch path provided to the main exhaust pipe for exhausting the exhaust gas to the outside, a branch path for introducing the detected exhaust gas branched from the main exhaust pipe to the hydrogen sensor, and a branch path, And cooling means for cooling the detected exhaust gas that is branched from the main exhaust pipe to the branch passage and introduced into the hydrogen sensor.

  According to the present invention, the detected exhaust gas which has been diverted to the branch path out of the high-temperature and high-humidity exhaust gas exhausted from the fuel cell to the main exhaust pipe is cooled by the cooling means 5 and then the water is removed. Can be introduced. Thereby, generation | occurrence | production of the dew condensation in a hydrogen sensor can be prevented.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS The best embodiment for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a configuration around a hydrogen sensor installed in a fuel cell system according to Embodiment 1 of the present invention. In Example 1 shown in FIG. 1, in a fuel cell stack in which an oxidant gas such as air is supplied to the cathode side through an air pipe and hydrogen gas of fuel gas is supplied to the anode side through a fuel pipe, The hydrogen gas supplied to the side moves to the cathode side through the solid polymer electrolyte as hydrogen ions, and reacts with oxygen in the air supplied to the cathode side to generate electric power. The reaction gas generated by the reaction between hydrogen and oxygen becomes steam in the cathode and is exhausted from the exhaust pipe to the outside of the fuel cell. A hydrogen sensor 1 for detecting hydrogen in high-temperature and high-humidity exhaust gas exhausted from such a fuel cell system is provided in the fuel cell system.

  In the main exhaust pipe 2 for leading the exhaust gas exhausted from the fuel cell system to the outside of the system, the hydrogen sensor 1 is supplied with a shunt exhaust gas that is shunted from the exhaust gas flowing through the main exhaust pipe 2 and becomes a sample gas for detection. A branch pipe 3 (branch path) leading to the main exhaust pipe 2 is provided. The branch pipe 3 is provided with a shut-off valve 4 (shut-off means) that controls the shut-off of the introduction of the split flow exhaust gas to the hydrogen sensor 1. The shutoff valve 4 may be provided in the branch pipe 3 on the downstream side of the hydrogen sensor 1.

  The branch pipe 3 on the downstream side of the shutoff valve 4 is provided with a cooling means (cooling space) 5 for cooling the shunt exhaust gas. The cooling means 5 is composed of, for example, a metal mesh provided in the flow path of the diverted exhaust gas, a cooling fin provided outside the flow path, etc., and cools the diverted exhaust gas that has flowed in. Is lowered to a temperature lower than the temperature of the inner wall of the housing room in which the detection part of the hydrogen sensor 1 is housed.

  The branch pipe 3 on the downstream side of the cooling means 5 is provided with a heating means 6 for heating the diverted exhaust gas flowing through the branch pipe 3. The heating means 6 is composed of, for example, a ribbon heater that covers the branch pipe 3. When the diverted exhaust gas heated by the heating means 6 is introduced into the hydrogen sensor 1, the heated diverted exhaust gas is used as a housing. The internal wall surface of the room is warmed, and the amount of heat that causes the surface temperature of the internal wall of the housing room to be higher than the temperature of the diverted exhaust gas at the branch inlet of the branch pipe 3 is separated into the heated space that flows through the branch pipe 3. Feed the gas and heat the diverted exhaust gas.

  The branch pipe 3 on the downstream side of the heating means 6 is provided with a hydrogen sensor 1 that detects hydrogen in the split flow exhaust gas that is branched from the main exhaust pipe 2 and guided through the branch pipe 3. This hydrogen sensor 1 has a diverted exhaust gas guided through a branch pipe 3 heated by a shutoff valve 4, a cooling means 5, and a heating means 6 provided in a branch pipe 3 branched from a main exhaust pipe 2. It is introduced into a housing room in which a detection unit for detecting hydrogen is housed, and detects hydrogen in the shunt exhaust gas. The split flow exhaust gas discharged from the hydrogen sensor 1 when hydrogen is detected is led to the main exhaust pipe 2 downstream of the pipe pressure loss adjusting valve 7 via the branch pipe 3.

  The main exhaust pipe 2 is provided with a pipe pressure loss adjusting valve 7 (pressure adjusting means) on the downstream side of the branch inlet to which the branch pipe 3 is connected. The pipe pressure loss adjusting valve 7 controls the flow rate of the exhaust gas flowing through the main exhaust pipe 2 according to the opening of the valve, so that the flow rate of the shunt exhaust gas that is shunted from the main exhaust pipe 2 to the branch pipe 3 is always maintained. Adjust and control to a constant flow rate. The valve opening degree of the pipe pressure loss adjusting valve 7 is determined by the pressure of the exhaust gas detected by the pressure sensor 8 (pressure measuring means) provided in the main exhaust pipe 2 upstream of the pipe pressure loss adjusting valve 7. And the pressure of the diverted exhaust gas detected by the pressure sensor 9 (pressure measuring means) provided near the branch inlet of the branch pipe 3 is adjusted and controlled.

  The branch pipe 3 is provided with a temperature sensor 10 composed of a thermocouple or the like at the branch inlet, and this temperature sensor 10 measures the temperature of the shunt exhaust gas at the branch inlet. In addition, a temperature sensor 11 composed of a thermocouple or the like is provided in the heating space inside the branch pipe 3 where the heating means 6 is installed, and this temperature sensor 11 measures the temperature of the shunt exhaust gas flowing through the heating space. To do.

  Opening / closing of the valve in the shutoff valve 4, heating / stopping control in the heating means, and opening / closing of the valve in the pipe pressure loss adjusting valve 7 were detected by various sensors including the pressure sensors 8 and 9 and the temperature sensors 10 and 11. It is controlled by a control unit (not shown) constituted by a microcomputer or the like that functions as a control center for inputting the detection result and controlling the operation of the fuel cell system.

  In such a configuration, among the high-temperature and high-humidity exhaust gas exhausted from the fuel cell system, a small flow rate of exhaust gas is diverted to the branch pipe 3 as a sample gas for detection. The flow rate of the split flow exhaust gas to be branched into the branch pipe 3 is based on the pressure loss difference between both pipes obtained by the pressure sensor 8 provided in the main exhaust pipe 2 and the pressure sensor 9 provided in the branch pipe 3. By controlling the opening of the pipe pressure loss adjusting valve 7, the flow rate is always kept constant. Further, although there are times when it is not necessary to use the hydrogen sensor 1 depending on the system, the shutoff valve 4 is closed to prevent the hydrogen sensor 1 from deteriorating and to prevent condensation.

  The branch exhaust gas branched from the main exhaust pipe 2 to the branch pipe 3 is first introduced into the cooling means 5 and cooled. Here, the cooling means 5 lowers the temperature of the diverted exhaust gas to a temperature equal to or lower than the surface temperature of the inner wall of the hydrogen sensor 1 to remove moisture from the diverted exhaust gas. Thereby, even if the shunt exhaust gas is introduced into the hydrogen sensor 1 and touches the inner wall to be cooled, it is avoided that condensation occurs. The shunt exhaust gas cooled by the cooling means 5 is then heated by the heating means 6. Here, the surface of the inner wall of the hydrogen sensor 1 is heated by the heated diverted exhaust gas, and the amount of heat at which the surface temperature becomes higher than the temperature of the diverted exhaust gas at the branch inlet of the branch pipe 3 is branched by the heating means 6. It is given to the diverted exhaust gas flowing through the heating space of the pipe 3.

  The cooling space of the cooling means 5 is at a temperature lower than the temperature of the shunt exhaust gas, and does not reach a temperature higher than the temperature of the shunt exhaust gas serving as a heat source. For this reason, the heat quantity of the split flow exhaust gas is exchanged with heat, for example, between the cooling fins and the metal mesh constituting the cooling means 5 and moves to the cooling means 5.

  On the other hand, since heat is always generated by the power generation reaction of the fuel cell, the temperature of the shunt exhaust gas cannot be lower than the outside air temperature. In other words, the outside air temperature does not become higher than the temperature of the shunt exhaust gas. Therefore, the amount of heat received by the cooling means 5 from the shunt exhaust gas moves to the ambient air around the cooling means 5 by radiative cooling that naturally occurs from the cooling fins or the metal mesh. As a result, the cooling means 5 is cooled with a higher cooling effect than a normal branch pipe or the like, and the relationship between the temperature of the shunt exhaust gas and the temperature of the cooling space of the cooling means 5 is as follows.

Divided exhaust gas temperature> Cooling space temperature of cooling means 5 (1)
On the other hand, the temperature of the inner wall of the hydrogen sensor 1 is gradually increased by heating the inner wall of the hydrogen sensor 1 with the diverted exhaust gas heated by the heating means so as to be higher than the temperature of the diverted exhaust gas at the branch inlet. Is set to a temperature higher than the temperature of the diverted exhaust gas at the branch inlet. Thereby, the relationship between the temperature of the heating space of the heating means 6, the temperature of the inner wall of the hydrogen sensor 1, and the temperature of the branch exhaust gas at the branch inlet is as shown below.

Temperature of heating space in heating means 6> Internal wall temperature in hydrogen sensor 1> Temperature of branch flow exhaust gas at branch inlet (2)
Therefore, the relationship between the internal wall temperature in the hydrogen sensor 1 and the temperature of the cooling space of the cooling means 5 is as shown below by the relationship shown in the above (1) and (2).

Internal wall temperature in hydrogen sensor 1> cooling space temperature in cooling means 5 (3)
Due to the relationship shown in (3) above, the temperature of the cooling space of the cooling means 5 can always be set lower than the temperature of the inner wall of the hydrogen sensor 1.

  On the other hand, in the heating means 6, the temperature sensors 10 and 11 provided in the branch inlet of the branch pipe 3 and the heating space of the branch pipe 3 measure the temperature of each of the divided exhaust gases, and the difference between the two temperatures (heating space temperature− When the rate of change in the branch exhaust gas temperature at the branch inlet changes from positive to negative, energization is started and heating is started. On the contrary, when the change rate of the difference between the two temperatures is switched from minus to plus, energization is stopped and heating is stopped. In this way, by controlling the operation of the heating means 6, the response delay of the temperature change of the object having the heat capacity (diverted exhaust gas) is prefetched, and the temperature of the heating space is always determined from the temperature of the branch inlet of the branch pipe 3. Can be kept high.

  The power consumption (heat generation amount) of the heating means 6 is such that the cooling space of the cooling means 5 is gradually warmed by the diverted exhaust gas, so that the cooling speed of the cooling means 5 is lower than the speed at which the cooling capacity of the cooling means 5 decreases. It is set so that the temperature rise speed is higher.

  Thus, by cooling the shunt exhaust gas by the cooling means 5, the dew point of the shunt exhaust gas cooled by the cooling means 5 reaches below the internal wall temperature in the hydrogen sensor 1. Even if the heated diverted exhaust gas touches the inner wall of the hydrogen sensor 1 that is not warmed at the time of starting the system, and the temperature of the diverted exhaust gas decreases to the inner wall temperature in the hydrogen sensor 1, condensation will occur. Absent.

  On the other hand, when the cooling means 5 gradually warms up over a long period of operation of the system or the outside air temperature is high, the temperature difference between the cooling space and the outside air is reduced, and the cooling effect (radiation cooling amount) of the cooling means 5 is reduced. Even when the temperature decreases with time, the internal wall temperature in the hydrogen sensor 1 is heated by the diverted exhaust gas and becomes higher than the temperature of the diverted exhaust gas at the branch inlet until such a state is reached. Therefore, even if the shunting exhaust gas is no longer cooled by the cooling means 5, condensation does not occur. That is, it can be said that the cooling means 5 fulfills the function of backing up prevention of condensation until the internal wall temperature in the hydrogen sensor 1 becomes warmer than the branch exhaust gas temperature at the branch inlet.

  FIG. 2 shows the time transition of the shunt exhaust gas temperature and the internal wall temperature in the hydrogen sensor 1, and FIG. 3 shows the temperature transition in the hydrogen sensor 1 from the branch inlet of the branch pipe 3 at the temperature indicated by A in FIG. It represents.

  2 and 3, first, the branch exhaust gas temperature at the branch inlet is T1 ° C. The diverted exhaust gas at this temperature is lowered by the cooling means 5 to a temperature lower than the internal wall temperature T2 ° C. in the hydrogen sensor 1, and moisture is removed from the diverted exhaust gas. At this time, since the dew point of the diverted exhaust gas becomes T2 ° C. or lower, no dew condensation occurs even if the diverted exhaust gas touches the inner wall of the hydrogen sensor 1.

  Subsequently, the cooled diverted exhaust gas is heated by the heating means 6. This heating is performed to warm the inner wall of the hydrogen sensor 1. When the diverted exhaust gas heated by the heating means 6 warms the inner wall of the hydrogen sensor 1, the temperature of the diverted exhaust gas is reduced by heat exchange, but it is lower than the inner wall temperature T2 ° C. of the hydrogen sensor 1. It cannot be considered from the viewpoint of heat exchange, and it can be said that condensation does not occur.

  In this way, the inner wall of the hydrogen sensor 1 is warmed by the heat of the shunt exhaust gas warmed by the heating means 6. At this time, since the temperature of the heating space of the branch pipe 3 is maintained at a temperature higher than the temperature of the diverted exhaust gas at the branch inlet, the internal wall temperature in the hydrogen sensor 1 becomes the diverted exhaust gas after a certain amount of time has passed. The temperature becomes higher than the temperature.

Thereby, after the internal wall temperature in the hydrogen sensor 1 becomes higher than the branch exhaust gas temperature at the branch inlet (after the intersection of the two temperatures in FIG. 2), condensation does not occur. That is, by causing the cooling means 5 and the heating means 6 to act on the diverted exhaust gas introduced into the hydrogen sensor 1, dew condensation is completely prevented from the start of the system while warming the inner wall of the hydrogen sensor 1. It becomes possible.

  As described above, in the first embodiment, of the high-temperature and high-humidity exhaust gas exhausted from the fuel cell system to the main exhaust pipe 2, the shunt exhaust gas that has been split into the branch pipe 3 is converted into hydrogen by the cooling means 5. The sensor 1 is cooled to a temperature equal to or lower than the temperature of the inner wall of the housing room that houses the detection unit, and after removing moisture from the shunt exhaust gas, the shunt exhaust gas is introduced into the hydrogen sensor 1 so that the shunt exhaust gas becomes a hydrogen sensor. Even if it cools by touching the internal wall in 1, dew condensation can be prevented. Thereby, it becomes possible to prevent the failure of the hydrogen sensor 1 due to condensation, and the reliability of the hydrogen sensor 1 can be improved.

  Further, by heating the inner wall of the hydrogen sensor 1 with the heat of the diverted exhaust gas heated by the heating means 6, it becomes possible to warm the inner wall of the hydrogen sensor 1 that is desired to be heated directly.

  Furthermore, since the high-temperature, high-humidity diverted exhaust gas exhausted from the fuel cell is introduced into the cooling means 5 with the passage of time after starting the system, the cooling means 5 is gradually warmed and a desired cooling effect is expected. Although it may become impossible, by providing the heating means 6 immediately downstream of the cooling means 5, when the inner wall of the hydrogen sensor 1 is warmed by the diverted exhaust gas warmed by the heating means 6, the hydrogen sensor is exchanged by heat exchange. Although the internal wall temperature of 1 increases, the shunt exhaust gas temperature decreases, so that the occurrence of condensation can be prevented.

  Further, during a period when hydrogen detection is not necessary, the shutoff valve 4 is closed so that the split exhaust gas is not introduced from the main exhaust pipe 2 to the branch pipe 3. As a result, catalyst deterioration due to the constant exposure of hydrogen to the detection unit of the hydrogen sensor 1 can be prevented. In addition, it is not necessary to heat the hydrogen sensor 1 with an external heater for preventing dew condensation, power for operating the heater becomes unnecessary, and power consumption can be reduced.

  In addition, the temperature of the cooling space in the cooling unit 5 is always kept at a temperature lower than the temperature of the inner wall in the hydrogen sensor 1, so that the temperature of the shunt exhaust gas passing through the cooling unit 5 can be reduced. It becomes possible to cool to below the temperature, and moisture can be removed from the diverted exhaust gas. As a result, the dew point of the shunted exhaust gas after cooling is lower than the inner wall temperature of the hydrogen sensor 1, and even if this shunted exhaust gas touches and cools the inner wall of the hydrogen sensor 1, condensation is prevented. be able to.

  Furthermore, by maintaining the temperature of the heating space in the heating means 6 at a temperature that is always higher than the temperature of the diverted exhaust gas at the branch inlet, the temperature of the diverted exhaust gas that passes through the heating space is higher than the temperature of the diverted exhaust gas at the branch inlet. A high temperature can be achieved. As a result, the shunt exhaust gas having a temperature higher than the shunt exhaust gas temperature at the branch inlet is introduced into the hydrogen sensor 1 and continues to warm the inner wall of the hydrogen sensor 1, so that the inner wall temperature of the hydrogen sensor 1 is shunted at the branch inlet. It becomes possible to make the temperature higher than the exhaust gas temperature. Therefore, even if the shunt exhaust gas introduced into the hydrogen sensor 1 touches the inner wall of the hydrogen sensor 1, it is possible to prevent the occurrence of condensation.

  Further, by connecting a branch pipe 3 that is thinner than the main exhaust pipe 2 to the main exhaust pipe 2 and providing a metal mesh or the like of the cooling means 5 on the branch pipe 3, the pressure loss of the branch pipe 3 is increased and desired. It is assumed that the flow rate (a small flow rate such that the time delay of hydrogen detection is within a predetermined allowable time) does not flow for the purpose of preventing condensation.

  In order to prevent such a phenomenon, the main exhaust pipe 2 on the downstream side of the branch inlet is provided with a pipe pressure loss adjusting valve 7 and the opening of the pipe pressure loss adjusting valve 7 is adjusted to adjust the main exhaust. Pressure loss is performed in the pipe 2. That is, based on the pressure difference 8 (pressure loss difference) monitored by the pressure sensor 8 provided in the main exhaust pipe 2 and the pressure sensor 9 provided at the branch inlet of the branch pipe 3, the pipe pressure loss The opening degree of the adjustment valve 7 is changed in accordance with the flow rate so that a small flow of exhaust gas is continuously supplied to the branch pipe 3. As a result, it is possible to flow a diverted exhaust gas having a desired flow rate from the main exhaust pipe 2 to the branch pipe 3.

  FIG. 4 is a diagram showing a configuration around a hydrogen sensor installed in the fuel cell system according to Example 2 of the present invention. The feature of the second embodiment shown in FIG. 4 is that, compared to the first embodiment, instead of the branch pipe 3 of the first embodiment, the diffusion exhaust gas that becomes the detection sample gas from the exhaust gas flowing through the main exhaust pipe 2. The main exhaust pipe 2 is provided with an introduction path 21 (branch path) for guiding a gas to the hydrogen sensor 1.

  The introduction path 21 is provided with the hydrogen sensor 1 at the end of the bag path, and is provided with cooling fins 22 as cooling means in the middle of the introduction path 21 from the main exhaust pipe 2 to the hydrogen sensor 1. The exhaust gas flowing through the main exhaust pipe 2 is introduced into the introduction passage 21 by natural diffusion, and the introduced diffusion exhaust gas is cooled to the vicinity of the internal wall temperature in the hydrogen sensor 1 by the cooling fins 22 and is cooled. The gas reaches the hydrogen sensor 1 and is introduced into the hydrogen sensor 1.

  In the second embodiment, since the detection sample gas is introduced into the hydrogen sensor 1 by natural diffusion, a means for maintaining the detection sample gas at a desired small flow rate as in the first embodiment is required. do not do.

  Further, since it depends on natural diffusion, the flow rate of the sample gas for detection is very small, so the amount of condensation is inevitably reduced. Furthermore, since the detection sample gas passing through the cooling fins 22 has a very small flow rate, the cooling efficiency is also increased. For this reason, the sample gas for detection is quickly cooled to near the inner wall temperature in the hydrogen sensor 1, and it is possible to suppress dew condensation without heating the inner wall in the hydrogen sensor 1. Accordingly, it is possible to prevent the occurrence of condensation with a small and simple configuration.

  FIG. 5 is a diagram showing a configuration around a hydrogen sensor installed in the fuel cell system according to Example 3 of the present invention. The feature of the third embodiment shown in FIG. 5 is that, compared to the second embodiment, an external heater 31 is attached to the hydrogen sensor 1 and a metal mesh 32 is provided instead of the cooling fins 22 as a cooling means. is there.

  The exhaust gas flowing through the main exhaust pipe 2 is introduced into the introduction path 21 by natural diffusion as in the second embodiment, and the introduced diffusion exhaust gas is cooled to the vicinity of the internal wall temperature in the hydrogen sensor 1 by the metal mesh 32. The cooled diffusion exhaust gas reaches the hydrogen sensor 1 heated and heated by the external heater 31 and is introduced into the hydrogen sensor 1.

  In the third embodiment, as described in the second embodiment, the exhaust gas temperature immediately after the start-up is such that the detection limit gas reaches the failure limit condensation amount only by cooling with the cooling means. It functions effectively in a fuel cell system in which the rising speed of the fuel cell is high. That is, the temperature of the sample gas for detection introduced into the introduction path 21 is cooled by the metal mesh 32 to near the internal wall temperature of the hydrogen sensor 1 and heated by the external heater 31 to be heated. The sample gas temperature can always be kept lower than the internal wall temperature in the hydrogen sensor 1. Thereby, even in a system in which the exhaust gas temperature rises quickly, it is possible to prevent the occurrence of condensation.

  In the third embodiment, the detection sample gas introduced into the introduction passage 21 between the metal mesh 32 of the cooling means and the hydrogen sensor 1 is heated, for example, the ribbon heater described in the first embodiment. A heating means may be provided. In this case, as in the first embodiment, the inner wall of the hydrogen sensor 1 is warmed by the detection sample gas heated by the heating means, so that the rising speed of the inner wall temperature of the hydrogen sensor 1 can be increased.

It is a figure which shows the structure of the periphery in which the hydrogen sensor was installed in the fuel cell system which concerns on Example 1 of this invention. It is a figure which shows the mode of a temperature change with the internal wall temperature of a hydrogen sensor, and exhaust gas temperature. It is a figure which shows the mode of the temperature change of the shunt exhaust gas with respect to the distance from a branch inlet. It is a figure which shows the structure of the periphery in which the hydrogen sensor was installed in the fuel cell system which concerns on Example 2 of this invention. It is a figure which shows the structure of the periphery in which the hydrogen sensor was installed in the fuel cell system which concerns on Example 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Hydrogen sensor 2 ... Main exhaust pipe 3 ... Branch pipe 4 ... Shut-off valve 5 ... Cooling means 6 ... Heating means 7 ... Pipe pressure loss adjustment valve 8, 9 ... Pressure sensor 10, 11 ... Temperature sensor 21 ... Introduction Path 22 ... Cooling fin 31 ... Heater 32 ... Metal mesh

Claims (6)

A hydrogen sensor for detecting hydrogen contained in exhaust gas exhausted from a fuel cell that generates electricity by reacting hydrogen of fuel gas and oxidant gas;
A branch path provided to branch to a main exhaust pipe for exhausting the exhaust gas to the outside, and introducing the detected exhaust gas diverted from the main exhaust pipe to the hydrogen sensor;
A fuel cell system comprising: cooling means provided in the branch path, for cooling the detected exhaust gas that is branched from the main exhaust pipe to the branch path and introduced into the hydrogen sensor. 2. The fuel cell system according to claim 1, wherein heating means for heating the detected exhaust gas cooled by the cooling means is provided in the branch path downstream of the cooling means. 3. The fuel cell system according to claim 1, wherein a shut-off means for shutting off the detected exhaust gas that is branched from the main exhaust pipe to the branch path is provided at the most upstream part of the branch path. The said cooling means cools the to-be-detected exhaust gas branched into the said branching path to temperature lower than the internal wall temperature of the said hydrogen sensor, The one of Claim 1, 2 and 3 characterized by the above-mentioned. Fuel cell system. 3. The fuel cell system according to claim 2, wherein the heating means heats the detected exhaust gas cooled by the cooling means to a temperature higher than the temperature of the exhaust gas at the branch inlet of the branch path. A pressure adjusting means provided in the main exhaust pipe downstream from the branch inlet of the branch path, for adjusting the pressure of the exhaust gas in the main exhaust pipe;
A first pressure measuring means provided at a branch inlet of the branch path, for measuring the pressure of the detected exhaust gas that branches into the branch path;
A second pressure measuring means provided in the main exhaust pipe between the adjusting means and the branch inlet of the branch path, and measuring a pressure of the exhaust gas upstream of the pressure adjusting means;
Based on the pressure measured by the first and second pressure measuring means, the pressure adjusting means adjusts the pressure of the exhaust gas flowing through the main exhaust pipe, and the detected exhaust gas to be diverted to the branch passage. The fuel cell system according to any one of claims 1, 2, 3, 4 and 5, wherein the flow rate is controlled.

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