JP2007242530A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system in which deterioration of an operation efficiency is prevented and an operation failure of an adjustment valve at a low temperature is prevented. <P>SOLUTION: The adjustment valve 23 is provided in an air exhausting passage 15 in which an exhausted air from the fuel cell flows. A compressed air from an air compressor 17 is supplied through an air supplying passage 19 to the fuel cell 1 and a part of the compressed air is supplied to the adjustment valve 23 through an air bypass passage 25 bifurcated from the air supplying passage 19, and freezing of the adjustment valve is prevented. A ventilating air is supplied to a fuel cell case 27 through a ventilating passage 37 bifurcated from the air supplying passage 19, and the exhaust is supplied to the adjustment valve 23. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system that generates power by supplying fuel gas and oxidant gas to a fuel cell.

  In a fuel cell that generates power by an electrochemical reaction between hydrogen and oxygen, conventionally, in order to normally start at a low temperature such as below freezing point, a system component is often warmed using a heating means such as a heater.

  However, in this case, since it is necessary to provide a separate heating means, extra driving power is required, especially when a fuel cell is mounted on a moving body such as an automobile, in consideration of cost and installation space. Then, adoption becomes difficult.

Here, focusing on the pressure regulating valve that adjusts the pressure of the reaction gas (hydrogen or air) supplied to the fuel cell among the components of the fuel cell system described above, for example, according to Patent Document 1 below, There is a method of controlling the pressure regulation valve so that the opening degree of the pressure regulation valve does not become a predetermined degree or less when it is detected that the pressure regulation valve is likely to be frozen so that the pressure regulation valve does not freeze at low temperatures.
JP 2004-31288 A

  However, in the conventional fuel cell system described above, when exhaust gas with moisture is introduced into the pressure regulating valve after power generation is started, the flow velocity increases and the pressure decreases, so that the inner surface of the flow channel is frosted. There is a problem that it is easy to occur and slows down the operation of the valve, or worst freezes to fix the valve and make the pressure adjustment impossible.

  In addition, since the pressure control valve is controlled so that the opening degree of the pressure regulation valve is not less than a predetermined opening degree, a range of pressure control by the pressure regulation valve is limited, which causes a problem that the operation efficiency of the fuel cell system is reduced.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to prevent a malfunction of a pressure regulating valve at a low temperature while preventing a decrease in operating efficiency as a fuel cell system.

  The present invention provides a fuel cell system in which fuel gas and oxidant gas are supplied to a fuel cell to generate power, an air supply passage for supplying air containing oxidant gas from a compressor to the fuel cell, and exhaust from the fuel cell Each air discharge passage through which air flows is provided, and a pressure regulating valve for adjusting the pressure of the air is provided in the air discharge passage, and a pressure regulating valve air supply passage for supplying the compressed air from the air supply passage is connected to the pressure regulating valve. The most important feature is that

  According to the present invention, the pressure regulating valve provided in the air discharge passage of the fuel cell has a high temperature and can be supplied with dry air directly from the compressor, so that the frost of the pressure regulating valve can be provided without any additional heating means. It is possible to improve the low temperature startability by preventing malfunction at low temperature due to sticking or freezing, etc. At this time, it is not necessary to limit the opening of the pressure regulating valve, so the operating efficiency of the fuel cell system is reduced Can be avoided.

  Also, when operating the fuel cell at a low load such as during idle operation, it is inefficient to operate the compressor at a very low speed, so if air is supplied to the fuel cell while maintaining a certain degree of rotation, the fuel cell May dry out and power generation performance may drop. Even in such a case, if the excess air at low load is supplied to the pressure regulating valve via the pressure regulating valve air supply passage, the efficiency of the compressor is reduced while maintaining the power generation performance of the fuel cell. You can drive without stopping.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an overall configuration diagram showing a fuel cell system according to a first embodiment of the present invention. Hydrogen gas, which is a fuel gas, is supplied to the fuel cell 1 from a fuel supply source such as a hydrogen tank (not shown) through a hydrogen pressure regulating valve 5 provided in the hydrogen supply passage 3, and the discharged hydrogen gas discharged from the fuel cell 1 is Then, the hydrogen is returned to the downstream side of the hydrogen pressure regulating valve 5 through a hydrogen circulation device 9 provided in the hydrogen circulation passage 7, thereby constituting a hydrogen circulation system.

  A purge pipe 11 serving as a fuel gas discharge passage is connected downstream of the hydrogen circulation device 9 in the hydrogen circulation passage 7, and through the purge valve 13 provided in the purge pipe 11, the circulating hydrogen is supplied to an air discharge passage 15 to be described later. Shed part.

  On the other hand, the air is supplied from the compressor 17 to the fuel cell 1 through the humidifier 21 provided in the air supply passage 19, and the exhaust air discharged from the fuel cell 1 passes through the air discharge passage 15 to the outside. Discharged. The air exhaust passage 15 is provided with the humidifier 21 and the pressure regulating valve 23 described above from the fuel cell 1 side. The purge pipe 11 described above is connected downstream of the pressure regulating valve 23.

  In the humidifying device 21, the dry air flowing through the air supply passage 19 is humidified by the moisture in the exhaust air flowing through the air discharge passage 15, and the humidified air is supplied to the fuel cell 1. The solid polymer electrolyte membrane is ensured in a wet state.

  In the air supply passage 19 between the compressor 17 and the humidifier 21, an end of an air bypass passage 25 that bypasses the fuel cell 1 and through which air flows is located upstream, and in the fuel cell case 27 that houses the fuel cell 1. One end of a ventilation inlet passage 29 that supplies air to the downstream is connected to the downstream side. The air bypass passage 25 and the ventilation inlet passage 29 are provided with a bypass valve 31 and a ventilation valve 33 as passage opening / closing means, respectively.

  Then, the other end of the air bypass passage 25 described above is connected to the pressure regulating valve 23. Further, the other end of the ventilation inlet passage 29 is connected to the fuel cell case 27, one end of the ventilation outlet passage 35 is connected, and the other end of the ventilation outlet passage 35 is connected to the pressure regulating valve 23. The ventilation outlet passage 35 and the ventilation inlet passage 29 constitute a ventilation passage 37. Further, the ventilation passage 37 and the air bypass passage 25 constitute a pressure regulating valve air supply passage.

  A hydrogen concentration sensor 39 as a fuel gas concentration detection means is installed in the air discharge passage 15 downstream from the pressure regulating valve 23, and whether or not the hydrogen concentration detected by the hydrogen concentration sensor 39 is equal to or lower than a predetermined value is determined. A control device 41 as a control means monitors.

  2A is a simplified cross-sectional view of the pressure regulating valve 23, and FIG. 2B is a cross-sectional view corresponding to a cross section taken along line AA of FIG. 2A. However, the opening degree of the pressure regulating valve 23 is different between FIG. 2A and FIG.

  The pressure regulating valve 23 includes a shaft portion 45 that is rotatable with respect to the passage wall in a cylindrical housing 43, and a valve that is provided on the shaft portion 45 and opens and closes the internal passage, that is, the air supply passage 15. And a body 47.

  The housing 43 has a double-pipe structure on the right upstream side in FIG. 2 with respect to the shaft portion 45 and the valve body 47 and includes an annular air supply space 49, and an air supply space downstream from the air supply space 49. 49, an air outflow space 51 is provided. The air supply space 49 and the air outflow space 51 constitute an air introduction passage 53.

  The shape of the air introduction passage 53 including the air supply space 49 and the air outflow space 51 described above is shown as a perspective view in FIG. As shown in FIG. 3, the air outflow space 51 extends further downstream from the downstream end of the air supply space 49 at two locations facing each other in the circumferential direction. An outlet 55 is provided.

  On the other hand, air inlets 57 are provided at positions facing each other at 90 degrees along the circumferential direction of the air supply space 49 with respect to the air outflow space 51 described above, and each of the air inlets 57 has the air bypass described above. The passage 25 and the ventilation outlet passage 35 are connected to each other.

  According to the fuel cell system having the above-described configuration, the hydrogen regulated by the hydrogen regulating valve 5 is supplied to the fuel cell 1 through the hydrogen supply passage 3, and the air compressed by the compressor 17 is humidified. Humidified at 21 and supplied to the fuel cell 1, the fuel cell 1 generates power.

  At this time, the discharged hydrogen gas discharged from the fuel cell 1 is returned to the hydrogen supply passage 3 through the hydrogen circulation passage 7 by the hydrogen circulation device 9 and supplied to the fuel cell 1 again. On the other hand, when the purge valve 13 is opened according to the operating state of the fuel cell 1, part of the discharged hydrogen gas flows into the air discharge passage 15 downstream of the pressure regulating valve 23 through the purge pipe 11.

  On the other hand, the exhausted air discharged from the fuel cell 1 humidifies the dried air flowing through the air supply passage 19 by the humidifying device 21, is regulated by the pressure regulating valve 23, and then is discharged outside the system.

  Further, the ventilation air flowing from the air supply passage 19 to the ventilation inlet passage 29 always flows into the fuel cell case 27 through the ventilation valve 33 that is open at a constant opening, and in the fuel cell case 27, the ventilation air slightly passes from the fuel cell 1. A small amount of hydrogen that has permeated into the fuel cell case 27 and leaked into the internal space of the fuel cell case 27 is retained, diluted so that its concentration does not increase, and discharged outside the fuel cell case 27.

  The diluted air is supplied to the pressure regulating valve 23 through the ventilation outlet passage 35, and the air flowing from the air supply passage 19 to the air bypass passage 25 has an opening degree according to the operating state at that time. It is supplied to the pressure regulating valve 23 through the adjusted bypass valve 31.

  When the air flowing through the air bypass passage 25 and the air flowing through the ventilation outlet passage 35 are supplied to the pressure regulating valve 23 as described above, air is introduced into the annular air supply space 49 as shown in FIGS. After flowing in through the inflow port 57, it flows out from the air outflow port 55 through the air outflow space 51 toward the end of the shaft portion 45 near the passage wall.

  Here, in the so-called butterfly valve type pressure regulating valve 23 as described above, the gap between the valve body 47 near the shaft portion 45 and the passage wall surface is the smallest and the flow velocity is high as shown in FIG. When the exhaust air with moisture is introduced when the pressure is lowered and the temperature is lowered and the housing 43 is cooled at the time of low temperature startup, conventionally, as shown in FIG. When the frost 59 is easily attached and increases, the valve body 47 moves so as to scrape the frost 59, so that the frost 59 accumulates, and the friction between the frost 59 and the valve body 47 causes the operation to be slow or the worst freeze. May stick.

  However, in the present embodiment, the frost 59 as described above is supplied to the end of the shaft portion 45 in the vicinity of the passage wall as described above, since the air that is out of the compressor 17 and has a high temperature is supplied. Can be prevented and smooth start-up can be performed. At this time, in this embodiment, since it is not necessary to limit the opening degree of the pressure regulating valve 23, it is possible to avoid a decrease in operating efficiency as the fuel cell system.

  Further, when operating at a low load such as an idle operation in the fuel cell system, it is inefficient to operate the compressor 17 at a very low rotation, so if air is supplied to the fuel cell 1 while maintaining a certain degree of rotation. As a result, the fuel cell 1 is dried and the power generation performance is reduced. Therefore, by bypassing the fuel cell 1 using the bypass valve 31 with excess air at the time of low load, the compressor 17 can be operated without reducing the efficiency while maintaining the power generation performance of the fuel cell 1. There is also an effect that can be done.

  FIG. 5 shows the relationship between the load of the fuel cell system and the opening degree of the bypass valve 31. According to this, it is indicated by a broken line at a low temperature where frost or freezing is likely to occur in the pressure regulating valve 23. As described above, when the load is low, the air supplied to the pressure regulating valve 23 is increased only for a certain period until the bypass valve 31 reaches the load L, and the opening degree of the bypass valve 31 is gradually reduced as the load increases thereafter. Go. Thereby, the operation efficiency of the fuel cell system can be maintained as desired while preventing generation of frost and freezing.

  On the other hand, during normal power generation when the temperature rises, there is no risk of frost or freezing. Therefore, as shown by the solid line, the opening of the bypass valve 31 is gradually reduced from full opening as the load increases from the start of operation. . At this time, the opening degree of the bypass valve 31 is set so that necessary air corresponding to the load is supplied to the fuel cell 1 while maintaining the rotation speed at which the efficiency of the compressor 17 can be maintained at a low load.

  In addition, according to the above-described embodiment, it is possible to efficiently prevent malfunction of the pressure regulating valve 23 by introducing dry air having a high temperature in the vicinity of the end portion of the shaft portion 45 where frost is likely to occur.

  In addition to the air flowing through the air bypass passage 25, the air flowing through the ventilation passage 37 is also supplied to the pressure regulating valve 23, so that the amount of high-temperature air increases and the malfunction of the pressure regulating valve 23 is prevented. Can be further enhanced.

  Note that the ventilation valve 33 is basically always opened at a constant opening even during normal power generation or cold start, and there is no need to control the opening, so an orifice is used or the diameter of the pipe itself is appropriately adjusted. If selected, there is no particular problem even if it is omitted.

  FIG. 6A is a cross-sectional view corresponding to FIG. 2A of a pressure regulating valve 23A showing a second embodiment of the present invention, and FIG. 6B is a cross-sectional view taken along line BB in FIG. It is sectional drawing corresponding to a line cross section. However, the opening degree of the pressure regulating valve 23A is different between FIG. 6A and FIG. 6B.

  Like the pressure regulating valve 23 shown in FIG. 2, the pressure regulating valve 23 </ b> A is provided in the cylindrical housing 43 </ b> A, a shaft portion 45 that can rotate with respect to the passage wall, and the shaft portion 45. An internal passage, that is, a valve body 47 that opens and closes the air supply passage 15 is provided.

  The housing 43A has a double-pipe structure on the right upstream side in FIG. 6 with respect to the shaft portion 45 and the valve body 47, and includes an annular air supply space 61. On the outer periphery of the upstream end portion of the air supply space 61, bypass air inlet 63 for introducing the air flowing through the air bypass passage 25 into the air supply space 61 and ventilation air flowing through the ventilation outlet passage 35, A ventilation air inlet 65 introduced into the air supply space 61 is connected to each other.

  The bypass air inlet 63 and the ventilation air inlet 65 have upstream end portions so that the air flowing into the air supply space 61 flows spirally along the circumferential direction as shown by the arrows in FIG. In the vicinity, the connection is made toward the downstream of the passage and to be inclined with respect to the axis of the passage.

  Further, the downstream end of the air supply space 61 is opened over the entire circumference and serves as an air outlet 67.

  The air supply space 61, the bypass air inlet 63, the ventilation air inlet 65, and the air outlet 67 constitute an air introduction passage.

  In the second embodiment shown in FIGS. 6 and 7, the bypass air and the ventilation air flow into the air supply space 61 from the bypass air inlet 63 and the ventilation air inlet 65 and flow out from the air outlet 67. After that, it flows toward the periphery of the valve body 47 while flowing along the inner surface of the passage.

  As a result, as in the first embodiment, air that is high in temperature and dried out of the compressor 17 is supplied to the end of the shaft portion 45 near the passage wall. Thus, it is possible to prevent the frost 59 from adhering as shown in FIG.

  In the second embodiment, since the bypass air and the ventilation air that have flowed into the air supply space 61 flow spirally along the circumferential direction, the housing 43A itself is warmed by the introduced high-temperature dry air, and Dry air that has flowed out from the air outlet 67 forms a layer along the inner surface of the passage, and this air layer prevents the exhaust air from directly contacting the inner surface of the passage, thereby preventing frost adhesion and freezing more effectively. be able to.

  Further, during normal power generation, exhaust air containing a large amount of water vapor is introduced into the pressure regulating valve 23. However, by introducing dry air having a high temperature through the air bypass passage 25, water vapor in the shaft portion 45, the valve body 47, and the housing 43A. Condensation of the water can be prevented, and poor pressure regulation due to accumulation of liquid water can also be prevented. Such an effect similarly occurs in the first embodiment.

  In the second embodiment described above, a spirally rotating air flow is generated in the air supply space 61 according to the air introduction angle of the bypass air inlet 63 and the ventilation air inlet 65 to the air supply space 61. However, for example, an air guide plate that rectifies the air flow so as to generate a spirally rotating air flow in the air supply space 61 may be attached in the air supply space 61.

  FIG. 8 is an explanatory view showing an example of the opening operation of the ventilation valve 33. In this example, the ventilation valve 33 is a valve whose opening degree can be adjusted, the opening degree is constant as shown by a solid line during normal power generation, and the opening degree is increased and the load is increased as shown by a broken line at low temperature startup. At the same time, the opening is gradually reduced. Thereby, in addition to the introduction of air through the air bypass passage 25 at the time of low load at the time of low temperature start-up, a larger amount of high-temperature dry air can be introduced into the pressure regulating valve 23, so that freezing can be prevented more efficiently.

  Further, a hydrogen concentration sensor 39 that is usually installed only for the purpose of giving a warning when the concentration is higher than a predetermined concentration is used, and a bypass 31 valve and a ventilation valve 33 that are adjustable in opening degree are used, and a hydrogen concentration sensor 39 is used. When the control device 41 changes the opening degree of the bypass valve 31 and the ventilation valve 33 in accordance with the hydrogen concentration detected in step 1, the operating range can be further expanded.

  For example, when a predetermined hydrogen concentration or more is detected, the bypass valve 31 and the ventilation valve 33 are not fully opened and the supply air amount necessary for operation of the fuel cell 1 can be maintained. By increasing the opening degree of the ventilation valve 33, the hydrogen concentration in the air discharge passage 15 can be lowered, and the time during which the operation can be continued can be extended.

1 is an overall configuration diagram showing a fuel cell system according to a first embodiment of the present invention. (A) is simplified sectional drawing of a pressure regulation valve, (b) is sectional drawing corresponding to the AA sectional view of (a). It is a perspective view which shows the shape of the air introduction channel | path in the pressure regulation valve of FIG. It is a perspective view which shows the state in which frost adhered to the channel | wall wall surface of the axial part vicinity of a pressure regulation valve. It is explanatory drawing which shows the relationship between the load of a fuel cell system, and the opening degree of a bypass valve. (A) is sectional drawing of the pressure regulation valve which shows the 2nd Embodiment of this invention, (b) is sectional drawing corresponding to the BB sectional view of (a). It is a perspective view which shows the shape of the air introduction channel | path in the pressure regulation valve of FIG. 6, and the flow state of air. It is explanatory drawing which shows the relationship between the load of a fuel cell system, and the opening degree of a ventilation valve.

Explanation of symbols

1 Fuel cell 11 Purge piping (fuel gas discharge passage)
DESCRIPTION OF SYMBOLS 15 Air discharge passage 17 Compressor 19 Air supply passage 23 Pressure regulation valve which adjusts the pressure of air 25 Air bypass passage (Air supply passage for pressure regulation valves)
31 Bypass valve (passage opening / closing means)
33 Ventilation valve (passage opening / closing means)
37 Ventilation passage (Air supply passage for pressure regulating valve)
39 Hydrogen concentration sensor (fuel gas concentration detection means)
41 Control device (control means)
43, 43A Pressure regulating valve housing 45 Pressure regulating valve shaft 47 Pressure regulating valve disc 49 Air supply space (air introduction passage)
51 Air outflow space (air introduction passage)
53 Air introduction passage 55 Air outlet (outlet) of air outflow space
61 Air supply space (air introduction passage)
63 Bypass air inlet (air introduction passage, inlet)
65 Ventilation air inlet (air introduction passage, inlet)
67 Air outlet (air introduction passage, outlet)

Claims (8)

  In a fuel cell system in which fuel gas and oxidant gas are supplied to a fuel cell to generate power, an air supply passage for supplying air containing oxidant gas from a compressor to the fuel cell, and air through which exhaust air flows from the fuel cell Each of the discharge passages is provided, and a pressure regulating valve for adjusting the pressure of air is provided in the air discharge passage, and a pressure regulating valve air supply passage for supplying the compressed air from the air supply passage is connected to the pressure regulating valve. A fuel cell system.   2. The fuel cell system according to claim 1, wherein the air supply passage for the pressure regulating valve is an air bypass passage that connects the air supply passage and the pressure regulating valve to allow the air to bypass the fuel cell. A fuel cell system.   2. The fuel cell system according to claim 1, wherein the pressure regulating valve air supply passage is a ventilation passage communicating with a fuel cell case that houses the fuel cell. 3.   4. The fuel cell system according to claim 1, wherein the pressure regulating valve includes a shaft portion that is rotatable with respect to a passage wall, and a valve body that is provided on the shaft portion and opens and closes the air supply passage. 5. The fuel cell system is characterized in that the air flowing through the pressure regulating valve air supply passage is supplied to the vicinity of the passage wall of the shaft portion.   5. The fuel cell system according to claim 4, wherein an air introduction passage for supplying air flowing through the pressure regulating valve air supply passage to the vicinity of the passage wall of the shaft portion is provided in the housing of the pressure regulating valve. Fuel cell system.   6. The fuel cell system according to claim 5, wherein the air introduction passage is located on the downstream side of the air supply space and an annular air supply space provided in a passage wall of the housing on the upstream side of the pressure regulating valve. A fuel cell system comprising: an air outflow space in which an outflow port opens so as to supply air to the vicinity of the passage wall of the shaft portion.   6. The fuel cell system according to claim 5, wherein the air introduction passage includes an annular air supply space provided in a passage wall of the housing on the upstream side of the pressure regulating valve, and a part of the air supply space in the circumferential direction. In addition, the air is supplied to the vicinity of the passage wall of the shaft portion at the inflow port where the air supplied to the air supply space flows so as to flow in the circumferential direction and the downstream end portion of the air supply space. A fuel cell system comprising an outlet and an outlet.   The fuel cell system according to any one of claims 1 to 7, wherein a fuel gas discharge passage through which exhaust fuel gas discharged from the fuel cell flows is connected to the air discharge passage downstream of the pressure regulating valve, A fuel gas concentration detection means is provided in the air discharge passage downstream of the fuel gas discharge passage, and a passage opening / closing means is provided in the air supply passage for the pressure regulating valve, and the fuel gas concentration detection means is provided according to the detected concentration of the fuel gas concentration detection means. A fuel cell system comprising control means for controlling opening and closing of the passage opening and closing means.

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