JPH10172593A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform fine control of the amount of humidification in compliance with the rate of gas flow supplied precisely and effectively while the configuration remains simple. SOLUTION: A fuel cell system comprises a fuel cell 12, humidifier part 14, and gas supply pipes 16 and 18. The gas supply pipe 16 is fitted with a flow meter 52 to sense the rate of hydrogen flow in the pipe 16 and a high pressure jetting nozzle 54 to supply pure water to the hydrogen for humidification. The flow meter 52 and nozzle 54 are connected with a control means 56 which sets the amount of pure water jetting from the nozzle 54 in conformity to the signal given by the flow meter 52.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel cell system for supplying a humidified gas to a fuel cell.

[0002]

2. Description of the Related Art For example, a fuel cell has been developed in which a plurality of fuel cell structures having an anode electrode and a cathode electrode opposed to each other with a solid polymer electrolyte membrane interposed therebetween are sandwiched by a separator and stacked. It is being put to practical use for various applications.

[0003] This type of fuel cell generally supplies hydrogen gas (fuel gas) to an anode side electrode and oxidant gas (air or oxygen gas) to a cathode side electrode. Are ionized and flow through the solid polymer electrolyte membrane, whereby electric energy is obtained outside.

In this case, in the fuel cell, it is necessary to maintain the solid polymer electrolyte membrane in an appropriate wet state in order to exhibit an effective power generation function. For this reason, by preparing a humidifying device for humidifying the fuel gas or the oxidizing gas with water in advance, and connecting the humidifying device to a fuel cell, the humidified fuel gas or the oxidizing gas is generated by the power generation unit. It is known to supply certain fuel cell structures.

As a humidifier of this type, for example, as disclosed in Japanese Patent Application Laid-Open No. Hei 7-263010, a humidifier comprising an ultrasonic generator, an injector, and a heater is connected to a hydrogen supply pipe connected to a fuel cell. A fuel cell system provided with a device is known. In this fuel cell system, the amount of pure water injected from the injector is controlled in accordance with the load of the fuel cell, and the injected pure water is atomized by an ultrasonic generator, and is also supplied via a heater. The fuel cell is configured to be heated to a reaction temperature.

[0006]

However, in the prior art described above, the gas is humidified only by pure water injected from a mechanically or electrically operated injector. For this reason, it has been pointed out that it is difficult to finely control the humidification amount, and particularly when the injector does not operate, the humidification amount of the gas is reduced or the gas cannot be humidified. And always,
There is a problem that power consumption increases due to control of the injector.

The present invention solves this kind of problem, and a fuel cell capable of performing a fine control of the humidification amount in accordance with the flow rate of supplied gas with high accuracy and efficiency with a simple configuration. The purpose is to provide a system.

[0008]

In order to solve the above-mentioned problems, in a fuel cell system according to the present invention, a fuel and / or a gas as an oxidant is constantly supplied by a fixed amount of pure water via a humidifying means. The humidified gas is supplied to the fuel cell, and based on a change in the flow rate of the gas flowing through the supply passage, pure water is supplied to the gas under the action of the high-pressure injection means to humidify the gas.

Specifically, when the flow rate of the gas supplied to the fuel cell is relatively small, only the humidifying means operates, while when the flow rate of the gas is relatively high, the humidifying means is additionally provided. The high pressure injection means operates. This makes it possible to easily perform fine humidification control according to the gas flow rate. Further, by using both the humidifying unit and the high-pressure injection unit, highly accurate humidification amount control is reliably performed.

Further, the humidifying means constitutes a membrane type humidifying means provided with a water permeable membrane. Therefore, the configuration of the humidifying unit can be effectively simplified, and the humidifying unit itself can be downsized by using the high-pressure injection unit together.

Further, the humidification amount by the humidification means is set to be at least equal to or more than the humidification amount corresponding to the gas at the flow rate required at the time of idling. Therefore, for example, the high-pressure injection unit starts operating only when a load equal to or more than a predetermined value is generated in the fuel cell due to the start of the running operation when the accelerator is depressed. As a result, highly accurate humidification amount control according to the load of the fuel cell is performed, and power saving is achieved.

[0012]

FIG. 1 is a schematic structural explanatory view of a fuel cell system 10 according to a first embodiment of the present invention.
The fuel cell system 10 includes a fuel cell 12 and a humidifying unit (humidifying means) 14 for constantly humidifying a fuel gas and an oxidizing gas supplied to the fuel cell 12 with a certain amount of pure water.
And gas supply pipes (supply passages) 16 and 18 for supplying hydrogen (fuel gas) and air (oxidant gas) to the humidifying section 14, respectively.

The fuel cell 12 includes a solid polymer electrolyte membrane 20
A power generation unit (unit cell) 26 having an anode 22 and a cathode 24 opposed to each other with the power generation unit 26 interposed therebetween.
Are laminated with a separator (not shown) interposed therebetween.
The fuel cell 12 has a fuel gas inlet 28, an oxidizing gas inlet 30, a fuel gas outlet 32, and an oxidizing gas (including reaction product water) outlet 34. As a means for detecting the load of the fuel cell 12, a means for detecting a current value may be used, or a means for detecting the supply amount of hydrogen or air supplied to the fuel cell 12 (see the flow chart to be described later). A meter 52) may be used.

The humidifying section 14 includes a plurality of water permeable membranes 36a to 36 spaced at predetermined intervals via a separator (not shown).
n, and each of the water permeable membranes 36a to 36n is formed of, for example, an ion exchange membrane. A fuel gas passage 38a and a humidifying water passage 40a are formed on both sides of the water permeable membrane 36a, and a water passage 4a is formed on both sides of the water permeable membrane 36b.
0b and an oxidant gas passage 42a are formed. A fuel gas passage 38b and a humidifying water passage 40c are formed on both sides of the water permeable membrane 36c, and a water passage 40d and an oxidizing gas passage 42b are formed on both sides of the water permeable membrane 36d. Hereinafter, the structure is the same up to the water permeable membrane 36n.

The humidifying section 14 has a fuel gas outlet 44 for supplying humidified hydrogen to the fuel gas inlet 28 of the fuel cell 12 and an oxidizing gas inlet of the fuel cell 12 for supplying the humidified air. Oxidizing gas outlet 4 for sending out to 30
6, a humidification water inlet 48 for supplying humidification water to the water channels 40a to 40d, and a humidification water outlet 50 for discharging the humidification water to the outside. The humidification water inlet 48 and the humidification water outlet 50 communicate with a water tank (not shown), and are configured to circulate and supply the humidification water.
Reaction water discharged from the fuel cell 12 is supplied to the water tank.

The gas humidification amount by the humidification unit 14 is set to be equal to or greater than the humidification amount corresponding to at least the flow rate of gas required at the time of idling when the fuel cell system 10 is used for a mobile body such as an electric vehicle. You.

The gas supply pipe 16 has
A flow meter (gas flow rate detecting means) 52 for detecting the flow rate of hydrogen flowing in the inside, and a high-pressure injection nozzle (high-pressure injection means) 54 for supplying pure water to the hydrogen as needed to humidify it are provided. . The pure water supplied to the high-pressure injection nozzle 54 is sent from a humidification water tank supplied to the humidification unit 14. The high-pressure injection nozzle 54 is generally constituted by an injector widely used for fuel injection of an automobile engine, and a detailed description thereof will be omitted.

The flow meter 52 and the high-pressure injection nozzle 54 are connected to control means 56 for setting a pure water injection amount of the high-pressure injection nozzle 54 based on a signal from the flow meter 52.

The gas supply pipe 18 for supplying air is
It is configured in the same manner as the gas supply pipe 16 for supplying hydrogen, and the same components are denoted by the same reference characters and will not be described in detail. Note that oxygen may be used instead of air, and the high-pressure injection nozzle 54 may be provided only in the gas supply pipe 16 on the hydrogen side.

The operation of the fuel cell system 10 according to the first embodiment will be described below.

First, as shown in FIG.
Is supplied as fuel gas to the high pressure injection nozzle 54 through the flow meter 52. As shown in FIG. 2A, when the load on the fuel cell 12 is smaller than the preset humidification switching line C, the high-pressure injection nozzle 54 is not operated, and hydrogen is supplied to the humidification unit 14 as it is. On the other hand, in the gas supply pipe 18, air is supplied as an oxidizing gas, and this air is supplied to the humidifying unit 14 in the same manner as the hydrogen.

Here, the case where the load on the fuel cell 12 is small corresponds to the case where the flow rate of hydrogen detected by the flow meter 52 is smaller than the set amount. Sent to 56. The control means 56 sets the pure water injection amount of the high-pressure injection nozzle 54 based on the detection signal from the flow meter 52.

In the humidifying section 14, the water permeable membranes 36a to 36n
Gas passages 38a, 38b formed on one side of
And oxidant gas passages 42a and 42b are supplied with hydrogen and air, respectively, and the water permeable membranes 36a to 36n
The humidification water is supplied to the water channels 40a to 40d formed on the other surface side of the. Thereby, the hydrogen and oxygen moving along one surface of the water permeable films 36a to 36n are humidified by the humidified water moving along the other surface of the water permeable films 36a to 36n. By penetrating,
Humidified.

The humidified hydrogen and oxygen are supplied from the fuel gas outlet 44 and the oxidant gas outlet 46 to the fuel cell 12.
Is supplied to the power generation unit 26 via the fuel gas inlet 28 and the oxidizing gas inlet 30.

As shown in FIG. 2A, when the load of the fuel cell 12 exceeds the humidification switching line C, the flow rate of hydrogen detected by the flow meter 52 becomes larger than the set amount. Thus, the high-pressure injection nozzle 54 is driven. Therefore, the pure water sent from the water tank (not shown) is atomized by the high-pressure injection nozzle 54 and injected into the hydrogen in the gas supply pipe 16, and the hydrogen is humidified and sent to the humidification unit 14. On the other hand, the air supplied to the gas supply pipe 18 is sent to the humidifier 14 in a humidified state.

The hydrogen and air sent to the humidifier 14 are
After being further humidified by the humidifying water supplied to the humidifying section 14 by a fixed amount, the power generation section 2 constituting the fuel cell 12
6. As a result, pure water is injected according to the load of the fuel cell 12 (see FIG. 2B), and hydrogen and air maintained in a desired humidified state are supplied to the power generation unit 26 of the fuel cell 12 to provide high quality. Power generation performance can be exhibited.

As described above, in the first embodiment, when the supply amount of hydrogen flowing through the gas supply pipe 16 is small (when the load on the fuel cell 12 is small), the hydrogen is humidified only by the humidification unit 14. The power is supplied to the power generation unit 26 of the fuel cell 12. On the other hand, when the supply amount of hydrogen flowing through the gas supply pipe 16 is large (when the load on the fuel cell 12 is large), the high-pressure injection nozzle 54 operates via the control means 56 and
The humidification by the high-pressure injection nozzle 54 is added to the humidification by, and the hydrogen is sufficiently humidified.

This makes it possible to easily perform fine humidification control in accordance with the gas flow rate by using the humidifying unit 14 and the high-pressure injection nozzle 54 in combination, and to connect the humidification unit 14 and the high-pressure injection nozzle 54 with each other. Since the humidification amount can be individually operated, an effect that the humidification amount control with high accuracy is surely performed can be obtained. Here, the combined use of the high-pressure injection nozzle 54 makes it possible to reduce the size of the humidifying unit 14 at a stroke as compared with the conventional structure.

Moreover, the gas humidification amount by the humidification unit 14 is
The humidification amount is set to at least the humidification amount corresponding to the gas at the flow rate required during idling. Therefore, at idle,
The operation of the high-pressure injection nozzle 54 can be stopped by using only the humidifier 14. Thereby, there is an advantage that power saving of the entire fuel cell system 10 can be easily performed.

The humidifying section 14 and the high-pressure injection nozzle 5
The humidification water (pure water) used in 4 is stored in the same water tank, and supplies reaction water discharged from the fuel cell 12 to this water tank. For this reason, the water tank can be effectively reduced in size, and the fuel cell system 1
0 is made compact.

In the first embodiment, the humidifying section 14 is provided at a stage subsequent to the high-pressure injection nozzle 54. On the contrary, the high-pressure injection nozzle 54 is connected to the fuel cell 12 and the humidifying section 14. It may be arranged between.

FIG. 3 is a schematic structural explanatory view of a fuel cell system 70 according to a second embodiment of the present invention. The same components as those of the fuel cell system 10 according to the first embodiment are denoted by the same reference numerals, and a detailed description thereof will be omitted.

In the fuel cell system 70, a Venturi nozzle 72 is provided between the high-pressure injection nozzle 54 and the humidifier 14. Thereby, the diffusibility and atomization of the pure water injected from the high-pressure injection nozzle 54 are improved, and it is possible to humidify hydrogen and air more effectively.

FIG. 4 is a schematic structural explanatory view of a fuel cell system 80 according to a third embodiment of the present invention. The same components as those of the fuel cell system 10 according to the first embodiment are denoted by the same reference numerals, and a detailed description thereof will be omitted.

In the fuel cell system 80, a heating section 82 is disposed between the high-pressure injection nozzle 54 and the humidifying section 14.
Accordingly, the same effects as in the second embodiment are obtained, such as the diffusibility and atomization of the pure water injected from the high-pressure injection nozzle 54 are improved.

[0036]

As described above, in the fuel cell system according to the present invention, the fuel and / or the gas as the oxidizing agent are constantly humidified by a certain amount of pure water via the humidifying means and supplied to the fuel cell. In addition, since the gas is humidified under the action of the high-pressure injection means based on the change in the gas flow rate, fine humidification control according to the gas flow rate can be easily performed. Further, by using the humidifying means and the high-pressure injection means together, high-precision humidification amount control is surely performed, and the humidifying means can be downsized, so that the entire fuel cell system can be made compact. .

[Brief description of the drawings]

FIG. 1 is a schematic configuration explanatory view of a fuel cell system according to a first embodiment of the present invention.

FIG. 2A is an explanatory diagram when a load of a fuel cell fluctuates, and FIG. 2B is an explanatory diagram of a pure water injection amount related to the load fluctuation.

FIG. 3 is a schematic configuration explanatory view of a fuel cell system according to a second embodiment of the present invention.

FIG. 4 is a schematic configuration explanatory view of a fuel cell system according to a third embodiment of the present invention.

[Explanation of symbols]

10, 70, 80 ... fuel cell system 12 ... fuel cell 14, 82 ... humidification unit 16, 18 ... gas supply pipe 26 ... power generation unit 36a to 36n
... water permeable membrane 52 ... flow meter 54 ... high pressure injection nozzle 56 ... control means 72 ... Venturi nozzle

Claims (3)

[Claims] 1. A fuel cell; a gas flow rate detecting means provided in a supply passage for supplying a gas as a fuel and / or an oxidant to the fuel cell; High-pressure injection means for supplying and humidifying pure water by means of: a means for setting a pure water injection amount of the high-pressure injection means based on a signal from the gas flow rate detection means; provided at a stage before or after the high pressure injection unit And a humidifying unit that constantly humidifies the gas supplied through the supply passage with a fixed amount of pure water. 2. The system according to claim 1, wherein the humidifying means includes a water permeable membrane, a gas supply passage formed on one surface of the water permeable membrane, and the other surface of the water permeable membrane. A fuel cell system, comprising: a humidification water channel formed in the fuel cell system. 3. The fuel cell system according to claim 1, wherein a humidification amount by said humidification means is set to at least a humidification amount corresponding to a gas having a flow rate required at the time of idling. .