JP2008235020A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of enhancing durability of an injector. <P>SOLUTION: The fuel cell system 1 is provided with a supply flow channel 22 supplying reaction gas to a fuel cell 2, a circulation flow channel 23 returning the reaction gas exhausted from the fuel cell 2 to a confluence A with the supply flow channel 22, an injector 25 fitted in the supply flow channel 22, and a pump 24 fitted in the circulation flow channel 23. Further, it is provided with a pump 100 impressing waves in an opposite phase to pulses generated by the pump 24 at a point from a confluence A to the injector 25. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell system in which an injector is provided in a supply flow path to a fuel cell.

The fuel cell system includes a fuel cell that generates electric power by receiving supply of fuel gas and oxygen gas (hereinafter collectively referred to as “reaction gas”). For example, in the fuel cell system described in Patent Document 1, a flow rate control valve (injector) is disposed in a supply flow path for supplying fuel gas to the fuel cell, and the opening / closing interval and valve opening time of the injector are controlled. The supply flow rate of the fuel gas to the fuel cell is adjusted by the control of the injector.
JP 2003-302563 A

  Although not examined in Patent Document 1, as a fuel cell stem, fuel off-gas and oxidizing off-gas (hereinafter collectively referred to as “reaction off-gas”) are discharged from the fuel cell, and the reaction off-gas is circulated to the fuel cell by a pump. There are also things to let you. In this fuel cell system, a circulation channel for returning the reaction off gas to the supply channel is provided, and a pump is provided in the circulation channel.

  A circulation system using such a pump can be applied to the fuel cell system described in Patent Document 1. However, since the pump generates pulsation as it is discharged, this pulsation may propagate to the injector via the junction of the supply flow path and the circulation flow path. If it becomes so, there exists a possibility that the durability of the internal structure of an injector may fall or it may cause trouble in the opening / closing operation | movement of an injector.

  An object of the present invention is to provide a fuel cell system capable of improving the durability of an injector in circulating reaction off gas to a fuel cell.

  In order to achieve the above object, a fuel cell system of the present invention includes a supply channel for supplying a reaction gas to a fuel cell, a circulation channel for returning a reaction off gas discharged from the fuel cell to a junction with the supply channel, And an injector provided in the supply flow path for injecting the reaction gas, a pump provided in the circulation flow path for pressure-feeding the reaction off gas, and a pulsation reducing means for reducing the pulsation transmitted from the pump to the injector.

  According to this configuration, the injector is suppressed from receiving repeated stress due to pulsation accompanying the discharge of the pump. Thereby, durability of an injector can be improved. Further, since the influence of pulsation by the pump is reduced, malfunction of the injector is also suppressed.

  According to a preferred aspect, the pulsation reducing means applies a wave having a phase opposite to that of the pulsation generated by the pump, between the merging point and the injector.

  According to this configuration, since the pulsation by the pump is canceled out, it is possible to suppress the pulsation from being propagated to the injector.

  More preferably, the pulsation reducing means is another injector arranged in parallel with the injector with respect to the fuel cell, or another pump arranged in parallel with the pump with respect to the fuel cell.

  According to another preferable aspect, the pulsation reducing means may be a buffer provided between the pump and the injector that pass through the junction.

  According to this configuration, since the buffer can absorb pulsation, it is possible to suppress propagation of this pulsation to the injector.

  According to another preferable aspect, the pulsation reducing means may be a control device that controls the rotational speed of the pump so as not to resonate with the injector.

  According to this configuration, it is possible to avoid resonance in the injector that is most affected by pulsation, and thus it is possible to suitably improve the durability of the injector. In addition, since it is a method of controlling the rotational speed of the pump that generates pulsation, it is not necessary to provide another mechanical structure (such as the above-described buffer) for pulsation reduction.

  According to another preferable aspect, the injector is located upstream from the confluence, and the pulsation reducing means may apply a wave having the same phase as the pulsation upstream of the injector.

  According to this configuration, similarly to the above, since the pulsation by the pump is canceled, propagation to the injector can be suppressed. Further, vibration that can be propagated upstream from the injector can also be suppressed.

  In order to achieve the above object, a fuel cell system of the present invention includes a supply channel for supplying a reaction gas to a fuel cell, a circulation channel for returning a reaction off gas discharged from the fuel cell to a junction with the supply channel, And an injector provided in the supply flow path for injecting the reaction gas, and a pump provided in the circulation flow path for pressure-feeding the reaction off gas. Then, the pipe length of the flow path between the pump and the injector that passes through the junction is adjusted so that the reaction gas and the reaction off gas that are out of phase with each other join the junction.

  According to this configuration, since the reaction gas and the reaction off gas that are out of phase with each other merge, the pulsation of the reaction off gas is canceled by the reaction gas. Thereby, it can suppress that the pulsation of the reaction off gas which a pump generate | occur | produces to an injector, and can improve durability of an injector.

  According to a preferred aspect of the present invention, the pipe length of the flow path may be a length that deviates from the resonance point of the injector.

  According to this configuration, it is possible to avoid resonance at the injector that is most affected by pulsation.

  According to the fuel cell system of the present invention described above, the durability of the injector can be enhanced when the reaction off gas is circulated and supplied to the fuel cell.

  Hereinafter, a fuel cell system according to a preferred embodiment of the present invention will be described as an example with reference to the accompanying drawings.

(First configuration example)
As shown in FIG. 1, the fuel cell system 1 includes a fuel cell 2, an oxygen gas piping system 3, a fuel gas piping system 4, and a control device 6.

  The fuel cell 2 is made of, for example, a solid polymer electrolyte type and has a stack structure in which a large number of cells are stacked. The fuel cell 2 generates electric power upon receiving supply of oxygen gas and fuel gas. Further, water is generated on the air electrode side of the fuel cell 2 by this electrochemical reaction. Supply and discharge of oxygen gas and fuel gas to and from the fuel cell 2 are performed by an oxygen gas piping system 3 and a fuel gas piping system 4.

  Oxygen gas and fuel gas are collectively referred to as reaction gas. In particular, oxygen gas and fuel gas discharged from the fuel cell 2 are referred to as oxygen off gas and fuel off gas, respectively, and these are collectively referred to as reaction off gas. Hereinafter, air will be described as an example of oxygen gas, and hydrogen gas will be described as an example of fuel gas.

  The oxygen gas piping system 3 includes a humidifier 11, a supply flow path 12, a discharge flow path 13, an exhaust flow path 14, and a compressor 15. The compressor 15 is provided at the upstream end of the supply flow path 12. Air in the atmosphere taken in by the compressor 15 flows through the supply flow path 12, is pumped to the humidifier 11, is humidified by the humidifier 11, and is supplied to the fuel cell 2. The oxygen off-gas flows through the discharge channel 13 and is introduced into the humidifier 11, and then flows through the exhaust channel 14 and is discharged to the outside.

The fuel gas piping system 4 includes a hydrogen tank 21, a supply channel 22, a circulation channel 23, a pump 24, and an injector 25.
The hydrogen tank 21 is a hydrogen supply source that stores high-pressure hydrogen gas.

  The supply channel 22 supplies the hydrogen gas in the hydrogen tank 21 to the fuel cell 2. The supply flow path 22 includes a main flow flow path 22a and a mixing flow path 22b. The main flow channel 22 a is located upstream from the junction A between the supply channel 22 and the circulation channel 24, and the mixing channel 22 b is located downstream from the junction A. A shut valve 31 and a regulator 32 are provided on the upstream side of the injector 25 in the main flow path 22a. The shut valve 31 functions as a main valve of the hydrogen tank 21. The regulator 32 depressurizes the hydrogen gas.

  The circulation channel 23 returns the hydrogen off gas discharged from the hydrogen gas outlet of the fuel cell 2 to the supply channel 22. A purge passage 35 is branched and connected to the circulation passage 23, and the purge valve 36 is periodically opened. Thereby, the fall of the hydrogen concentration of the hydrogen gas circulated and supplied to the fuel cell 2 can be suppressed.

  The pump 24 is interposed in the circulation channel 23 and pumps the hydrogen off gas to the junction A. Therefore, at the merge point A, the new hydrogen gas from the hydrogen tank 21 and the hydrogen off gas from the pump 24 merge, and the mixed hydrogen gas after the merge flows through the mixing channel 22b and is supplied to the fuel cell 2. . The pump 24 can be configured in various types, for example, a positive displacement type. For example, the pump 24 includes a three-phase AC motor 24a and a compressor unit having an impeller coupled to a drive shaft of the motor 24a. The rotational speed of the motor 24a, that is, the pump rotational speed is controlled by the control device 6.

  The injector 25 is provided in the main flow path 22a and injects hydrogen gas toward the junction A. Although not shown, the injector 25 has a nozzle portion that injects hydrogen gas and a valve portion that controls the supply of hydrogen gas to the nozzle portion. The valve unit is electrically connected to the control device 6. The valve unit is an electromagnetically driven on-off valve (shutoff valve) that can adjust the supply of hydrogen gas to the nozzle unit by driving the valve body at a predetermined driving cycle by electromagnetic driving force and separating it from the valve seat. It has a configuration. By changing the opening time and opening degree of the valve unit, the supply flow rate of hydrogen gas to the nozzle unit is controlled, and the flow rate and pressure of hydrogen gas to the secondary side (fuel cell 2) are adjusted with high accuracy. .

  As a method for controlling the injector 25, it is preferable to use duty control that changes the duty ratio of the pulsed excitation current to be supplied to the valve section. Here, the duty ratio is obtained by dividing the ON time of the pulsed excitation current by the switching period obtained by adding the ON time and the OFF time of the pulsed excitation current. In addition, the opening degree or opening time in a valve part can be switched in two steps, multi-step, continuous (no step), or linear.

  The control device 6 is configured as a microcomputer having a CPU, ROM, and RAM therein. The CPU executes a desired calculation according to the control program, and performs various processes and controls such as control of a pump 24 and an injector 25 described later. The ROM stores control programs and control data processed by the CPU. The RAM is mainly used as various work areas for control processing. The control device 6 receives detection signals from various sensors and outputs control signals to components such as the pump 24 and the injector 25.

  In the fuel cell system 1 described above, the pump 24 pressurizes and discharges the hydrogen off-gas, and joins the hydrogen gas injected from the injector 25. However, when the pulsation of the hydrogen off-gas is generated by the discharge of the pump 24, this pulsation propagates to the valve portion of the injector 25 via the confluence point A, and stress repeatedly acts on the valve portion. As a result, for example, the life of the support spring that supports the valve body may be shortened. Further, the urging force of the spring that urges the valve body to the valve seat acts obliquely, and the valve body may bite and damage the sliding surface.

  Therefore, in the first configuration example of the present invention, the control device 6 is used as means for reducing pulsation by the pump 24. In this case, the control device 6 may control the rotation speed of the pump 24 so that resonance does not occur in the valve portion of the injector 25 due to pulsation by the pump 24. Specifically, the control device 6 may control the motor 24a of the pump 24 so as to skip the pump rotation speed at which resonance occurs in the valve portion of the injector 25. By doing so, it is possible to avoid resonance at the injector 25 where the influence of pulsation is the greatest, so that the durability of the injector can be enhanced. In addition, since the number of rotations of the pump 24 that generates pulsation is controlled, it is not necessary to provide another mechanical structure to reduce pulsation.

  Next, another configuration example for reducing the influence of hydrogen off-gas pulsation on the injector 25 will be described with reference to FIGS.

(Second configuration example)
As shown in FIG. 2, as a means for reducing the pulsation caused by the pump 24, another pump 100 that applies a wave f ₂ having a phase opposite to that of the pulsation wave f ₁ may be used. The pump 100 has, for example, the same structure as the pump 24 and is connected to the control device 6. The fluid taken in and compressed by the pump 100 is hydrogen gas, and the pump 100 pumps the hydrogen gas to the junction A. The position where the pump 100 feeds hydrogen gas is not limited to the junction A as long as it is between the injector 25 and the junction A. The hydrogen gas taken in by the pump 100 is hydrogen gas in the main flow channel 22 a or the circulation channel 23, and the pump 100 is arranged in parallel with the pump 24 with respect to the fuel cell 2.

When reducing the pulsation caused by the pump 24, the control device 6 sets the rotation speed of the motor 100 a of the pump 100 to the rotation speed of the motor 24 a of the pump 24 so that the phase of the wave f _{1 and} the phase of the wave f ₂ are shifted by 180 degrees. Synchronize with. At this time, the discharge pressures of the pump 24 and the pump 100 are made the same. By controlling the pump 100 in this way, the pulsation caused by the pump 24 is canceled out. Thereby, it can suppress that the pulsation by the pump 24 propagates to the injector 25, and the durability of the injector 25 can be improved.

(Third configuration example)
As shown in FIG. 3, an injector 200 may be used instead of the pump 100. The injector 200 has the same structure as the injector 25, for example, and is connected to the control device 6. The injector 200 is arranged in parallel with the injector 25 with respect to the fuel cell 2.

  Specifically, the branch flow path 22 c is connected to the main flow path 22 a so as to bypass the injector 25, and the injector 200 is interposed in the branch flow path 22. The injector 200 injects hydrogen gas from the hydrogen tank 21 to the downstream side of the injector 25. The injected hydrogen gas may join the hydrogen gas from the injector 25 at any position as long as the flow path portion 22d is between the injector 25 and the junction A.

In reducing pulsation by the pump 24, the control device 6, so that the wave f ₂ phase and antiphase waves f ₁ is applied to the channel portion 22 d, it may be opening and closing the injector 200. Even with such a method, the pulsation caused by the pump 24 can be canceled and the durability of the injector 25 can be improved.

(Fourth configuration example)
As shown in FIG. 4, an injector 300 that is separate from the injector 25 may be provided upstream of the injector 25. The injector 300 has, for example, the same structure as the injector 25 and is connected to the control device 6. The injector 300 is disposed in series with the injector 25 with respect to the fuel cell 2 and is interposed in the main flow channel 22.

In reducing pulsation by the pump 24, the control device 6, so that the wave f ₃ of the phase and same phase of the wave f ₁ is applied to the upstream side of the injector 25 may be opening and closing the injector 300. According to such a method, pulsation absorption at the valve portion of the injector 25 can be reduced, and the durability of the injector 25 can be increased. In addition, vibration from the injector 25 toward the pressure regulating valve 32 can be suppressed.

  Furthermore, if the opening / closing timing of both the injectors 25 and 300 arranged in series is controlled to be shifted, the pressure fluctuation range of the hydrogen gas supplied to the fuel cell 2 can be reduced. Further, the injection start and the injection stop of the downstream injector 25 are preceded by the injection start and the injection stop of the upstream injector 300, respectively, so that the injection stop of the injector 25 is started from the start of the injection of the injector 300. The time until the time can be set as a new shortest injection time.

(Fifth configuration example)
As shown in FIG. 5, a buffer 400 may be used as means for reducing pulsation caused by the pump 24. The buffer 400 is interposed in the portion of the circulation channel 23 between the pump 24 and the junction A. The buffer 400 temporarily stores the hydrogen off gas pumped by the pump 24. In this way, by providing the buffer 400, the pulsation caused by the pump 24 is reduced so as to be absorbed by the buffer 400 once. Thereby, since the pulsation pressure by the pump 24 falls, it can suppress that a big pulsation pressure propagates to the injector 25. FIG. Therefore, durability of the injector 25 can be improved.

  In another embodiment, the buffer 400 may be interposed in the main flow channel 22a between the injector 25 and the junction A. Even with such a configuration, it is possible to suppress a large pulsating pressure from propagating to the injector 25 as described above. However, in view of the fact that the injector 25 controls the flow rate with high accuracy, the buffer 400 is preferably provided downstream of the pump 24 rather than downstream of the injector 25.

(Sixth configuration example)
FIG. 6 is a diagram showing a configuration that can reduce the influence of the pulsation by the pump 24 on the injector 25 with the same number of parts as the fuel cell system 1 shown in FIG. In this configuration, the pipe length of the flow path between the pump 24 and the injector 25 that passes through the merge point A is adjusted so that the hydrogen gas and the hydrogen off-gas that are out of phase with each other merge at the merge point A. .

Specifically, at least one of the pipe line length L ₁ from the injector 25 to the confluence point A and the pipe length L ₂ from the pump 24 to the confluence point A is adjusted so that the hydrogen off-gas The pulsation can be canceled by hydrogen gas. Preferably, the entire pipeline length (= L ₁ + L ₂ ) may be set to a length that deviates from the resonance point of the valve portion of the injector 25. By doing so, resonance at the valve portion of the injector 25 where the influence of pulsation becomes the largest can be avoided, and the durability of the injector 25 can be enhanced. Further, according to this configuration example, it is not necessary to provide other mechanical structures (such as the pump 100, the injectors 200 and 300, and the buffer 400) for reducing pulsation.

  The fuel cell system 1 of the present invention can be mounted on a moving body such as a train, an aircraft, a ship, a self-propelled robot, or the like other than a two-wheel or four-wheel automobile. In addition, the fuel cell system 1 can be stationary and can be incorporated into a cogeneration system.

  In each of the above-described examples, the example in which the pump 24 and the injector 25 are provided in the fuel gas piping system 4 has been described. Of course, the contents can be applied to the oxygen gas piping system 3. In that case, the discharge flow path 13 may be configured as a circulation flow path, and the oxygen off gas may be returned to the supply flow path 12.

It is a block diagram which shows the fuel cell system which concerns on a 1st structural example. It is a block diagram which shows the principal part of the fuel cell system which concerns on a 2nd structural example. It is a block diagram which shows the principal part of the fuel cell system which concerns on a 3rd structural example. It is a block diagram which shows the principal part of the fuel cell system which concerns on a 4th structural example. It is a block diagram which shows the principal part of the fuel cell system which concerns on a 5th structural example. It is a block diagram which shows the principal part of the fuel cell system which concerns on a 6th structural example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1: Fuel cell system, 2: Fuel cell, 6: Control apparatus, 22: Supply flow path, 23: Circulation flow path, 24: Pump, 25: Injector, 100: Pump (pulsation reduction means), 200: Injector (pulsation) (Reducing means), 300: injector (pulsation reducing means), 400: buffer (pulsation reducing means), A: confluence

Claims (8)

A supply flow path for supplying a reaction gas to the fuel cell;
A circulation flow path for returning the reaction off gas discharged from the fuel cell to the junction with the supply flow path;
In a fuel cell system comprising an injector provided in the supply flow path and injecting the reaction gas,
A pump provided in the circulation flow path for pumping the reaction off gas;
A fuel cell system comprising: pulsation reducing means for reducing pulsation transmitted from the pump to the injector.   2. The fuel cell system according to claim 1, wherein the pulsation reducing means applies a wave having a phase opposite to that of the pulsation generated by the pump between the junction and the injector.   The said pulsation reduction means is another injector arrange | positioned in parallel with the said injector with respect to the said fuel cell, or another pump arrange | positioned in parallel with the said pump with respect to the said fuel cell. Fuel cell system.   2. The fuel cell system according to claim 1, wherein the pulsation reducing unit is a buffer provided between the pump passing through the junction and the injector.   2. The fuel cell system according to claim 1, wherein the pulsation reducing unit is a control device that controls the rotation speed of the pump so as not to resonate with the injector. 3. The injector is located upstream of the junction;
The fuel cell system according to claim 1, wherein the pulsation reducing means applies a wave having the same phase as the pulsation upstream of the injector. A supply flow path for supplying a reaction gas to the fuel cell;
A circulation flow path for returning the reaction off gas discharged from the fuel cell to the junction with the supply flow path;
In a fuel cell system comprising an injector provided in the supply flow path and injecting the reaction gas,
A pump that is provided in the circulation flow path and pumps the reaction off gas;
A fuel cell system in which a pipe length of a flow path between the pump and the injector that passes through the merge point is adjusted so that a reaction gas and a reaction off gas that are out of phase with each other merge at the merge point .   The fuel cell system according to claim 7, wherein a pipe length of the flow path is a length that deviates from a resonance point in the injector.

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