JP2006339095A - Gas pipe for fuel cell and fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the obstruction of a gas flow by an influence of water present in a gas pipe for a fuel cell connecting to a fuel cell in a simple structure. <P>SOLUTION: In the gas pipe for a fuel cell which is connected to the fuel cell and in which a predetermined gas flows, a part of the pipe wall of the lower side in a horizontal part nearly horizontally arranged of the gas pipe for a fuel cell includes a downward convex part which is formed lower than the other part, the upper pipe wall opposing to the downward convex part is formed in a higher position than a pipe wall of the lower side of the horizontal part where the downward convex part is not formed, and a sectional area of the part having the downward convex part is formed smaller than a sectional area of the part not having the downward convex. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell gas pipe that is connected to a fuel cell and through which a predetermined gas flows.

  In recent years, fuel cells have attracted attention as a power source for electric vehicles. In a fuel cell that generates power by receiving supply of hydrogen and oxygen, water is generated in the process of power generation. Normally, this water is generated on the cathode side to which oxygen is supplied, but also permeates to the anode side through the electrolyte membrane. Since the operating temperature of the fuel cell rises to about 80 ° C., the water thus generated becomes water vapor or fine droplets and flows into various gas pipes connected to the fuel cell. During operation of the fuel cell system, these water vapor and droplets are discharged out of the system as off-gas.

  However, after the system is stopped, the water vapor in the gas pipe becomes droplets as the temperature of the fuel cell decreases, and moves to a lower part in the piping path due to the influence of gravity along with the droplets that were originally present. For this reason, when the fuel cell system is left in a sub-freezing environment, water may freeze at that portion and the inside of the pipeline may be significantly narrowed or blocked. As a result, the gas flow in the fuel cell system is hindered and the startability of the system is reduced. In particular, the pipe for supplying hydrogen to the anode of the fuel cell and the gas pipe for discharging the anode off-gas are often formed narrower than the gas pipe for supplying oxygen to the fuel cell. Cheap.

  Thus, for example, it is conceivable to discharge water by inclining a pipe for discharging off-gas over the entire length, but it may be difficult to adopt such a pipe configuration because of the structure of the vehicle. Patent Document 1 below discloses a technique for discharging water generated on the cathode side in a fuel cell by inclining the fuel cell itself or the lower edge of the fuel cell.

JP 2000-30725 A JP 2004-127666 A JP 2003-142136 A

  In view of such a situation, the problem to be solved by the present invention is that the flow of gas in the fuel cell gas pipe is obstructed by the influence of water generated in the process of power generation in the fuel cell. It is to be suppressed by the configuration.

In order to solve the above problems, the present invention is configured as follows. That is,
A fuel cell gas pipe connected to the fuel cell, in which a predetermined gas flows;
In a horizontal portion arranged in a substantially horizontal direction of the fuel cell gas pipe, a lower convex portion formed with a part of a tube wall on the lower side of the horizontal part lower than the other part,
The upper pipe wall of the fuel cell gas pipe facing the lower convex part is formed at a position higher than the lower pipe wall of the horizontal part where the lower convex part is not formed,
The cross-sectional area including the hollow portion of the fuel cell gas pipe in the portion having the lower convex portion is formed smaller than the cross-sectional area including the hollow portion of the fuel cell gas pipe in the portion not having the lower convex portion. It is a summary.

  The fuel cell gas pipe of the present invention has a downward convex part formed by forming a part of the lower tube wall of the horizontal part lower than the other part. Therefore, even if the power generation of the fuel cell is stopped and the water vapor present in the pipe becomes droplets, water is stored in the downward convex portion, and the gas flow in the pipe is obstructed with a simple configuration. This can be suppressed. Furthermore, since the upper pipe wall facing the lower convex part is formed at a position higher than the lower pipe wall of the horizontal part where the lower convex part is not formed, the lower convex part is filled with water. Even in such a case, the pipeline is not blocked. Moreover, since the cross-sectional area of the gas pipe including the downward convex portion is made smaller than the cross-sectional area of the other portion, when the fuel cell is started, the gas flow rate increases at that portion, and the water accumulated in the downward convex portion Can be efficiently discharged.

  Further, the present invention can be configured as a fuel cell system including the above-described fuel cell gas pipe in addition to the configuration as the fuel cell gas pipe.

Hereinafter, in order to further clarify the operation and effect of the present invention described above, embodiments of the present invention will be described based on examples.
FIG. 1 is an explanatory diagram showing the overall configuration of a fuel cell system 100 including a fuel cell gas pipe as an embodiment. The fuel cell gas pipe in this embodiment corresponds to a hydrogen circulation pipe 33 described later. As shown in the figure, a fuel cell system 100 includes a fuel cell 10 that generates power by an electrochemical reaction between hydrogen and oxygen, a hydrogen tank 20 that stores hydrogen, an air compressor 41 that supplies air to the fuel cell 10, and dilution. And a hydrogen pump 45 and the like. The fuel cell system 100 of the present embodiment is mounted on a vehicle and used as a power source for operating an electric motor 50 for driving an axle.

  The fuel cell 10 is a solid polymer electrolyte type fuel cell, and has a stack structure in which a plurality of unit cells (not shown) are stacked. Each single cell has a configuration in which a hydrogen electrode (hereinafter referred to as an anode) and an oxygen electrode (hereinafter referred to as a cathode) are arranged with an electrolyte membrane interposed therebetween. By supplying hydrogen gas to the anode side of each single cell and supplying air containing oxygen to the cathode side, an electrochemical reaction proceeds and an electromotive force is generated.

  An air supply pipe 35 and a cathode offgas discharge pipe 36 are connected to the cathode of the fuel cell 10. The air compressed by the air compressor 41 is supplied to the fuel cell 10 through the air supply pipe 35. This air is exhausted to the outside through the cathode offgas exhaust pipe 36 after oxygen is consumed by an electrochemical reaction in the fuel cell 10. The gas discharged from the cathode in this way is called cathode off gas. A pressure regulating valve 27 and a diluter 44 are connected to the cathode offgas discharge pipe 36. The pressure adjustment valve 27 is a valve for adjusting the back pressure of air supplied from the air supply pipe 35, and the supply amount of air supplied from the air compressor 41 is adjusted by the pressure adjustment valve 27. The diluter 44 is a device for diluting and discharging an anode off gas, which will be described later, with the cathode off gas.

  A hydrogen supply pipe 32 and a hydrogen circulation pipe 33 are connected to the anode of the fuel cell 10. Hydrogen is supplied from the hydrogen tank 20 to the anode through the hydrogen supply pipe 32. The hydrogen supply pipe 32 is provided with a regulator 23, and the high-pressure hydrogen supplied from the hydrogen tank 20 is reduced to a pressure suitable for power generation in the fuel cell 10 by the regulator 23.

  A part of the hydrogen supplied to the anode is consumed by an electrochemical reaction in the fuel cell 10, while the hydrogen that cannot be consumed by the electrochemical reaction is discharged to the hydrogen circulation pipe 33 as an anode off-gas. In addition to hydrogen, the anode off gas includes moisture, nitrogen, and the like that have permeated from the cathode side through the electrolyte membrane in the fuel cell 10.

  The anode off gas discharged to the hydrogen circulation pipe 33 passes through the downward projection 200 and is then pressurized by the hydrogen pump 45. The anode off gas thus pressurized passes through the check valve 28 and is supplied again to the hydrogen supply pipe 32. That is, the anode off gas discharged from the fuel cell 10 is circulated and supplied to the fuel cell 10. As described above, since the anode off gas contains hydrogen that could not be consumed by the electrochemical reaction by the fuel cell 10, the hydrogen can be efficiently utilized by circulating and supplying it to the fuel cell 10 in this way. Can do. The details of the downward projection 200 will be described later.

  Between the hydrogen pump 45 and the check valve 28 in the hydrogen circulation pipe 33, an anode offgas discharge pipe 34 is connected via a discharge valve 26. The other end of the anode off gas discharge pipe 34 is connected to a diluter 44. The discharge valve 26 is periodically opened, and the anode off gas is discharged from the discharge valve 26 through the anode off gas discharge pipe 34 to the diluter 44. The anode off gas discharged to the diluter 44 is diluted with the cathode off gas and then discharged to the outside. As described above, since the anode off gas contains moisture, nitrogen, and the like, the concentration thereof increases when the circulation is repeated. Therefore, by periodically opening and discharging the discharge valve 26, these impurities can be discharged together with hydrogen to reduce the concentration thereof.

  FIG. 2 is an explanatory view showing the piping shape of the hydrogen circulation pipe 33 having the downward convex portion 200. In the figure, a side cross-sectional view of the hydrogen circulation pipe 33, an AA ′ cross-sectional view of the hydrogen circulation pipe 33 in a portion including the lower convex portion 200, and a hydrogen circulation pipe 33 in a portion not including the lower convex portion 200 are illustrated. BB 'sectional drawing and the reference figure which aligned and overlap | superposed the major axis direction of each cross section in order to compare a cross-sectional area are shown.

  The hydrogen circulation pipe 33 is formed of stainless steel or resin, and as shown in the side sectional view of FIG. 2, a part of the lower wall of the hydrogen circulation pipe 33 provided in the horizontal direction is the other part. The lower convex part 200 is formed by being formed lower than this. Further, the upper pipe wall 220 of the hydrogen circulation pipe 33 facing the lower convex part 200 is formed at a position higher than the lower pipe wall 230 where the lower convex part 200 is not formed. The downward projecting portion 200 can be formed into a shape having a volume sufficient to store the amount of water by experimentally measuring the total amount of moisture present in the hydrogen circulation pipe 33 at the end of power generation of the fuel cell.

  In the present embodiment, the hydrogen circulation pipe 33 in the portion including the downward convex portion 200 has an elliptical shape having a long axis in the vertical direction, as shown in the AA ′ sectional view. On the other hand, the hydrogen circulation pipe 33 in the portion not including the downward convex portion 200 has an elliptical shape having a major axis in the horizontal direction, as shown in the BB ′ sectional view. In addition, as shown in the reference diagram, the cross-sectional area SA including the hollow portion of the portion having the lower convex portion 200 (AA ′ cross section) is the portion of the portion not having the lower convex portion 200 (BB ′ cross section). It is formed smaller than the cross-sectional area SB including the hollow portion. The area ratio of the cross-sectional area SA to the cross-sectional area SB can be set, for example, between 50% and 80%. In this embodiment, the cross-sectional area SA is an area of about 70% of the cross-sectional area SB. It was. The area ratio between the cross-sectional area SA and the cross-sectional area SB is such that the anode off-gas flow is not hindered by the portion where the lower convex portion 200 exists, and the water stored in the lower convex portion 200 is pushed out. It is possible to experimentally determine and set a value at which the flow velocity can be blown away. Further, the normal flow rate of the anode off gas is obtained from the rotational speed of the hydrogen pump 45, the power generation amount of the fuel cell 10, the cross-sectional area SB of the normal portion of the hydrogen circulation pipe 33, and the flow rate is stored in the lower convex portion 200. The value of the cross-sectional area SA may be set so as to increase to a flow rate at which water can be pushed out and blown away.

  According to the hydrogen circulation pipe 33 having such a shape, as the fuel cell system 100 is stopped, the temperature of the fuel cell is lowered, and the water vapor present in the hydrogen circulation pipe 33 becomes droplets. Even so, this droplet is stored in the downward convex portion 200 in the hydrogen circulation pipe 33 due to the influence of gravity. Further, since the upper tube wall facing the lower convex portion 200 is formed at a position higher than the lower tube wall 230 where the lower convex portion 200 is not formed, the entire lower convex portion 200 is filled with water. Even if it is done, the entire pipeline will not be filled with water. Therefore, even if the fuel cell system 100 is left in a sub-freezing environment, the water stored in the downward projection 200 is only frozen, and the entire pipeline of the hydrogen circulation pipe 33 is prevented from being frozen and blocked. Can do.

  In addition, in the hydrogen circulation pipe 33 of the present embodiment, the cross-sectional area of the portion including the lower convex portion 200 is formed smaller than the cross-sectional area of the other portions. Therefore, the flow rate of the anode off gas is increased in the portion including the lower convex portion 200, the water stored in the lower convex portion 200 is pushed out, and the water accumulated in the lower convex portion 200 can be efficiently discharged. Further, it can be considered that turbulent flow is generated in the portion where the cross-sectional area is changed, and the remaining water is rolled up and discharged.

  In addition, since the cross-sectional area of the part containing the downward convex part 200 is smaller than another part, there exists a possibility that a pressure loss may generate | occur | produce. However, hydrogen, which is the main component of the anode off-gas, has a lower viscosity and a lower mass than nitrogen and oxygen in the air. Therefore, it can be considered that the influence of the pressure loss in the downward convex portion 200 on the fluidity of the anode off gas flowing through the portion is extremely low.

  The embodiment of the present invention has been described above. According to the above-described embodiment, it is possible to suppress the piping connected to the fuel cell 10 from being blocked by freezing with a simple configuration. As a result, the piping design of the fuel cell system 10 can be performed with a high degree of freedom. Needless to say, the present invention is not limited to such embodiments, and various configurations can be adopted without departing from the spirit of the present invention. For example, the following modifications are possible.

  3 to 6 are explanatory views showing modifications of the hydrogen circulation pipe 33. For example, in the above embodiment, the pipe shape of the hydrogen circulation pipe 33 is such that the cross section of the portion including the lower convex portion 200 and the portion not including the lower convex portion 200 are elliptical. On the other hand, as shown in FIG. 3, for example, a cross section of a portion not including the downward convex portion 200 may be circular. Moreover, the bottom surface of the downward convex part 200 is good also as a rectangular shape, as shown in FIG. Moreover, as shown in FIG. 5, the upper convex part 210 and the downward convex part 215 (part shown with the broken line in the figure) are provided in the upper pipe wall facing the downward convex part of the hydrogen circulation pipe 33. Also good. Further, as shown in the side sectional view of FIG. 6, the downward convex portion may have a shape in which the vicinity of the center protrudes.

  As shown in these modifications, the hydrogen circulation pipe 33 has a lower convex portion 200 in which a part of the lower tube wall is formed lower than the other portions. The opposing upper tube wall is formed at a position higher than the lower tube wall where the lower convex portion 200 is not formed, and the cross-sectional area of the portion having the lower convex portion 200 has the lower convex portion 200. What is necessary is just to be formed smaller than the cross-sectional area in the part which is not.

  Further, in the above embodiment, the downward convex portion 200 is formed in the hydrogen circulation pipe 33, but the downward convex portion 200 may be formed also in the hydrogen supply pipe 32 and the anode off gas discharge pipe 34. This is because water vapor and droplets may exist in these pipes. Of course, it may be formed in the air supply pipe 35 or the cathode offgas discharge pipe 36.

1 is an explanatory diagram showing an overall configuration of a fuel cell system 100. FIG. It is explanatory drawing which shows the piping shape of the hydrogen circulation pipe 33 containing the downward convex part 200. FIG. It is explanatory drawing which shows the modification of the hydrogen circulation pipe. It is explanatory drawing which shows the modification of the hydrogen circulation pipe. It is explanatory drawing which shows the modification of the hydrogen circulation pipe. It is explanatory drawing which shows the modification of the hydrogen circulation pipe.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell 20 ... Hydrogen tank 23 ... Regulator 26 ... Discharge valve 27 ... Pressure regulating valve 28 ... Check valve 32 ... Hydrogen supply piping 33 ... Hydrogen circulation Pipe 34 ... Anode off-gas discharge pipe 35 ... Air supply pipe 36 ... Cathode off-gas discharge pipe 41 ... Air compressor 44 ... Diluter 45 ... Hydrogen pump 50 ... Electric motor 100. .. Fuel cell system 200 ... downward projection

Claims (2)

A fuel cell gas pipe connected to the fuel cell, in which a predetermined gas flows;
In a horizontal portion arranged in a substantially horizontal direction of the fuel cell gas pipe, a lower convex portion formed with a part of a tube wall on the lower side of the horizontal part lower than the other part,
The upper pipe wall of the fuel cell gas pipe facing the lower convex part is formed at a position higher than the lower pipe wall of the horizontal part where the lower convex part is not formed,
The cross-sectional area including the hollow portion of the fuel cell gas pipe in the portion having the lower convex portion is formed smaller than the cross-sectional area including the hollow portion of the fuel cell gas pipe in the portion not having the lower convex portion. The fuel cell gas pipe.   A fuel cell system comprising the gas pipe for a fuel cell according to claim 1.

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