JP2005228635A - Gas supply system of fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas supply system of a fuel cell, capable of enhancing durability as a whole while properly securing the circulation flow of an offgass. <P>SOLUTION: This gas supply system 4 of the fuel cell is disposed in a supply passage 22 to supply a gas to the fuel cell 2, and is provided with an ejector 24 to return the offgas exhausted from the fuel cell 2 to the supply passage 22 through a circulation passage 23, and a turbocharger 25 disposed in the circulation passage 23 to send the offgas to the ejector 24 by sucking it. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell gas supply system that circulates and supplies off-gas discharged from a fuel cell to a supply channel with an ejector.

Conventionally, as this type of gas supply system for circulating hydrogen gas, a supply channel for supplying hydrogen gas to a fuel cell, a circulation channel for returning hydrogen off-gas discharged from the fuel cell to the supply channel, and a circulation A device including an ejector that recirculates hydrogen off-gas in a flow path to a supply flow path and a hydrogen pump disposed in the circulation flow path is known (see, for example, Patent Document 1).
In general, when the hydrogen gas in the supply channel becomes a small flow rate, the ejector cannot sufficiently suck in the hydrogen off-gas in the circulation channel. Therefore, in this gas supply system, when the hydrogen gas has a small flow rate, the hydrogen pump is temporarily driven to ensure an adequate circulation flow rate of the hydrogen off gas.
Japanese Patent Laid-Open No. 2003-151588 (FIG. 1)

  However, such a conventional hydrogen pump may cause problems in cold startability and durability due to water droplets and ice blocks. In view of the fact that the hydrogen pump itself is heavy in driving power and weight, a new gas supply system is desired.

  An object of the present invention is to provide a gas supply system for a fuel cell capable of improving the durability as a whole while appropriately securing the circulation flow rate of off-gas.

  The fuel cell gas supply system according to the present invention includes an ejector disposed in a supply channel for supplying gas to the fuel cell, and configured to recirculate off-gas discharged from the fuel cell to the supply channel via the circulation channel, and a compressor And a turbocharger that is disposed in the circulation flow path and pumps off-gas to the ejector.

  According to this configuration, the supply and circulation of gas to the fuel cell is performed by the ejector. Even when the gas in the supply passage becomes a small flow rate, the turbocharger provided with the compressor side in the circulation passage can be used. Thus, off-gas can be sucked and forced into the ejector. As a result, the same result as that of increasing the circulation flow rate of off gas is produced, and therefore, a predetermined circulation flow rate of off gas can be appropriately ensured in the entire supply system (in a wide flow rate range). In addition, since a turbocharger is employed as an assisting such ejector, overall durability and energy efficiency can be improved.

  In this case, it is preferable that the turbine side of the turbocharger is disposed in the supply flow path.

  According to this configuration, the gas supplied to the fuel cell can be effectively used to assist with the turbocharger.

  In this case, the turbine side of the turbocharger is preferably disposed on the upstream side of the ejector in the supply flow path.

  According to this configuration, unlike the case where it is provided on the downstream side of the ejector, the gas ejected from the ejector is not used, so that a gas having a predetermined flow rate can be reliably supplied to the fuel cell. In particular, as will be described later, when the gas is hydrogen, high-pressure hydrogen can be effectively used to assist with the turbocharger.

  In these cases, the turbocharger is of a variable capacity type, and when the gas in the supply channel is at a small flow rate, the off-gas intake is shifted to an accelerating tendency, and when the gas in the supply channel is at a large flow rate, the off-gas intake is It is preferable to shift to a decreasing tendency.

  According to this configuration, the turbocharger positively assists the ejector with the turbocharger when the gas in the supply channel is at a low flow rate, and the turbocharger excessively sends off gas to the ejector when the gas in the supply channel is at a large flow rate. Can be suppressed. This eliminates the need for bypassing the gas by bypassing the turbine side of the turbocharger, particularly when the gas in the supply flow path has a large flow rate.

  In these cases, the gas and off-gas are preferably hydrogen.

  According to the fuel cell gas supply system of the present invention, by using the ejector and the turbo jar together, it is possible to appropriately secure the circulation flow rate of the off gas and to improve the durability as a whole.

  Hereinafter, an example in which a gas supply system for a fuel cell according to a preferred embodiment of the present invention is applied to a hydrogen gas supply system of a fuel cell system will be described with reference to the accompanying drawings. In addition, as a fuel cell system, the fuel cell vehicle represented by the apparatus carrying this is demonstrated to an example.

  As shown in FIG. 1, a fuel cell system 1 includes a solid molecular electrolyte type fuel cell 2 that generates electric power when supplied with oxygen gas (air) and hydrogen gas, and the fuel cell 2 has a large number of cells stacked. It is configured as a stack structure. The fuel cell system 1 includes an oxygen gas supply system 3 that supplies oxygen gas to the fuel cell 2, and a hydrogen gas supply system 4 that supplies hydrogen gas to the fuel cell 2.

  The oxygen gas supply system 3 includes an oxygen side supply channel 12 that supplies the oxygen gas humidified by the humidifier 11 to the fuel cell 2, and an oxygen side circulation flow that guides the oxygen off-gas discharged from the fuel cell 2 to the humidifier 11. A passage 13 and an oxygen side exhaust passage 14 for introducing oxygen off gas from the humidifier 11 to the combustor are provided. The oxygen-side supply flow path 12 is provided with a compressor 15 that takes in oxygen gas in the atmosphere and pumps it to the humidifier 11.

  The hydrogen gas supply system 4 includes a hydrogen tank 21 serving as a hydrogen supply source that stores high-pressure hydrogen gas, a hydrogen-side supply passage 22 that supplies the hydrogen gas in the hydrogen tank 21 to the fuel cell 2, and an exhaust from the fuel cell 2. A hydrogen-side circulation passage 23 for returning the hydrogen off-gas thus produced to the hydrogen-side supply passage 22; an ejector 24 for returning the hydrogen off-gas from the hydrogen-side circulation passage 23 to the hydrogen-side supply passage 22; And a turbocharger 25 for feeding into the ejector 24.

  The hydrogen supply channel 22 is provided with a shut valve 26 for opening and closing the hydrogen supply channel 22, a regulator 27 for adjusting the pressure of the hydrogen gas, and a flow rate control valve 28 for adjusting the flow rate of the hydrogen gas. It is installed. In the hydrogen side supply passage 22, the turbine 51 side of the turbocharger 25 is disposed between the flow control valve 28 and the ejector 24. On the other hand, a gas-liquid separator 29 is interposed in the hydrogen-side circulation flow path 23, and the compressor 52 side of the turbocharger 25 is disposed downstream thereof.

  The ejector 24 is configured as a needle type so that the flow rate can be varied, and is disposed so as to be interposed in the hydrogen side supply flow path 22. The ejector 24 includes a primary-side supply port 41 connected to the upstream side of the hydrogen-side supply flow path 22, a secondary-side discharge port 42 connected to the downstream side of the hydrogen-side supply flow path 22, and a hydrogen-side And a suction port 43 on the tertiary side (negative pressure acting side) connected to the downstream side of the circulation flow path 23. The ejector 24 returns the hydrogen off-gas to the hydrogen-side supply channel 22 through the hydrogen-side circulation channel 23. As a result, on the downstream side of the nozzle in the ejector 24 (that is, the diffuser side), the hydrogen gas from the primary side and the hydrogen off-gas from the tertiary side merge and are supplied to the fuel cell 2.

  The turbocharger 25 is disposed in the vicinity of the ejector 24, and includes a turbine 51 disposed in the hydrogen-side supply passage 22, a compressor 52 disposed in the hydrogen-side circulation passage 23, the turbine 51, and the compressor And a power transmission mechanism 53 having a shaft that connects the shafts 52 on the same axis.

  The turbine 51 has a turbine wheel with blades connected to a shaft, and a turbine housing that houses the turbine wheel. The turbine 51 converts the pressure energy of the hydrogen gas flowing through the hydrogen side supply passage 22 into mechanical energy, and rotates the shaft. In this case, the turbine wheel is configured such that the angle of the blade is variable.

  That is, the turbocharger 25 is of a variable capacity type and is configured by a so-called variable turbo. Since the turbocharger 25 is composed of a variable turbo, the compressor 52 is adjusted by adjusting the rotation amount of the shaft based on the flow rate of hydrogen gas in the hydrogen-side supply passage 22 (hereinafter referred to as the main flow rate of hydrogen gas). The supercharging rate can be adjusted (described later).

  The compressor 52 has a compressor wheel connected to the shaft, and a compressor housing that houses the compressor wheel. The compressor 52 pressure-feeds the hydrogen off-gas flowing through the hydrogen-side circulation passage 23 to the ejector 24 as the compressor wheel to which the driving force is input from the shaft rotates. As a result, even when the hydrogen gas in the hydrogen-side supply flow path 22 has a small flow rate, the flow rate of the hydrogen off-gas in the hydrogen-side circulation flow path 23 (hereinafter referred to as the hydrogen off-gas circulation flow rate) can be appropriately secured. Yes.

  Here, the relationship between the main flow rate of hydrogen gas and the circulation flow rate of hydrogen off gas will be described with reference to FIG. In general, when the fuel cell 2 is started up or idling, the main flow rate of hydrogen gas is set to a small flow rate, while when the output of the fuel cell 2 is increased during acceleration of the fuel cell vehicle or the like, The main flow rate is set to a large flow rate. The circulation flow rate of the hydrogen off gas is set in correlation with the main flow rate of the hydrogen gas from the viewpoint of power generation efficiency and the like. A straight line L1 shown in FIG. 2 shows specifications required for the fuel cell 2.

  A curve L2 shown in FIG. 2 shows characteristics when the system is driven without incorporating the turbocharger 25 in the hydrogen gas supply system 4 described above. As is obvious from the curve L2, the main flow rate of hydrogen gas generally requires a large flow rate in order for the ejector 24 to make the circulation flow rate of the hydrogen off gas sufficient. For this reason, when the main flow rate of hydrogen gas is a small flow rate (particularly 200 NL / min), the ejector 24 alone cannot satisfy the required value of the circulation flow rate of the hydrogen off gas.

  In the hydrogen gas supply system 4 according to the embodiment, when the main flow rate of the hydrogen gas is a small flow rate, the hydrogen off gas can be forcibly sent to the ejector 24 by the turbocharger 25, so that the circulation flow rate of the hydrogen off gas is increased. Can give similar results. Thereby, even when the main flow rate of hydrogen gas is a small flow rate, the circulation flow rate of hydrogen off gas can be ensured appropriately, and the required specifications of the fuel cell 2 can be satisfied.

  Therefore, the hydrogen gas supply system 4 according to the embodiment can ensure a predetermined hydrogen off-gas circulation flow rate over the entire region of the main flow rate of hydrogen gas, and thus can satisfy the required specifications of the fuel cell 2. It becomes. In particular, the turbocharger 25 is driven so that it does not become excessive when the main flow rate of hydrogen gas is large.

  That is, when the main flow rate of hydrogen gas is small, the turbocharger 25 shifts the hydrogen off-gas intake to an accelerating trend, and when the hydrogen gas main flow rate is a large flow, the turbo-charger 25 shifts the hydrogen off-gas intake to a decreasing trend. Let Thereby, since the supercharging rate of the compressor 52 described above is adjusted, even when the turbocharger 25 is incorporated in the hydrogen gas supply system 4, it is possible to appropriately satisfy the required specifications of the fuel cell 2. . As a further effect of the hydrogen gas supply system 4 according to the present embodiment, since the ejector 24 and the turbocharger 25 are used in combination, durability and energy efficiency of the entire system may be improved.

  Even if the turbocharger 25 is not a variable turbo, the turbocharger 25 can function to assist the ejector 24 only when the main flow rate of hydrogen gas is small. For example, by providing a bypass flow path or the like that bypasses the turbine 51 in the hydrogen side supply flow path 22, when the main flow rate of the hydrogen gas is a large flow rate, the hydrogen gas is bypassed so that it does not flow into the turbine 51. When the main flow rate of the gas is small, the hydrogen gas may flow into the turbine 51 without bypassing.

  In this embodiment, the turbine 51 side of the turbocharger 25 is disposed upstream of the ejector 24 in the hydrogen-side supply flow path 22. For example, the turbocharger 25 is disposed downstream of the ejector 24 in the hydrogen-side supply flow path 22. May be. Alternatively, it may not be the hydrogen side. For example, the turbine 51 side of the turbocharger 25 is disposed in the oxygen side supply flow path 12, the oxygen side circulation flow path 13 or the oxygen side exhaust flow path 14 of the oxygen gas supply system. Also good.

  In the above description, the hydrogen gas supply system 4 is taken as an example of the fuel cell gas supply system of the present invention, but it goes without saying that the present invention can also be applied to the oxygen gas supply system 3. In this case, for example, the ejector 24 is disposed in the oxygen-side supply channel 12 on the downstream side of the humidifier 11, and the turbine 51 side of the turbocharger 25 is connected to the oxygen-side supply channel 12 on the upstream side of the humidifier 11. The compressor 52 side of the turbocharger 25 is disposed in the oxygen-side circulation flow path 13.

It is a block diagram which shows typically the principal part of the gas supply system of the fuel cell which concerns on embodiment. It is a figure which shows the correlation of the mainstream flow volume and circulating flow volume in the gas supply system of the fuel cell which concerns on embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Fuel cell system, 2 Fuel cell, 3 Oxygen gas supply system, 4 Hydrogen gas supply system, 22 Hydrogen side supply flow path, 23 Hydrogen side circulation flow path, 24 Ejector, 25 Turbocharger, 51 Turbine, 52 Compressor

Claims (5)

An ejector disposed in a supply flow path for supplying gas to the fuel cell, and refluxing off-gas discharged from the fuel cell to the supply flow path through the circulation flow path;
A turbocharger that is disposed in the circulation flow path on the compressor side and pumps the off gas to the ejector;
A fuel cell gas supply system comprising:   The gas supply system for a fuel cell according to claim 1, wherein a turbine side of the turbocharger is disposed in the supply flow path.   The gas supply system for a fuel cell according to claim 2, wherein the turbine side of the turbocharger is disposed upstream of the ejector in the supply flow path.   The turbocharger is of a variable capacity type, and when the gas in the supply channel is at a small flow rate, the off-gas intake is shifted to an accelerating tendency, and when the gas in the supply channel is at a large flow rate, The gas supply system for a fuel cell according to any one of claims 1 to 3, wherein the off-gas intake is shifted to a decreasing tendency. The fuel cell gas supply system according to any one of claims 1 to 4, wherein the gas and the off-gas are hydrogen.

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