Gas-inlet pressure adjustment structure for flow field plate of fuel cell stack

Abstract

Disclosed is a gas-inlet pressure adjustment structure for a flow field plate of a fuel cell stack. At least one gas inlet opening, at least one gas outlet opening, and a plurality of channels are defined in a central zone of the flow field plate. A membrane electrode assembly is stacked over the central zone. The channels are of a parallel arrangement and each having a reduced open end and an expanded open end, the reduced open end having a cross-sectional area smaller than that of the expanded open end. The reduced open end communicates the gas inlet opening through which a reaction gas is supplied to the flow field plate. Water generated by chemical reaction occurring inside the flow field plate and attached to a surface of the gas channel by surface tension is expelled out of the channel by a force caused by a pressure difference induced in the reaction gas, which is supplied through the gas inlet opening and flows in sequence through the reduced open end, the channel, and the expanded open end and eventually discharges through the gas outlet opening.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be apparent to those skilled in the art by reading the following description of preferred embodiments thereof, with reference to the attached drawings, in which:

FIG. 1 schematically shows a cross-section of a single cell of a conventional fuel cell assembly;

FIG. 2 shows a cross-sectional view of a portion of the conventional fuel cell assembly;

FIG. 3 shows a cross-sectional view taken along line 3-3 of FIG. 2;

FIG. 4 shows a plan view of a flow field plate for a fuel cell in accordance with a first embodiment of the present invention;

FIG. 5 shows an enlarged view of encircled portion A in FIG. 4;

FIG. 6 shows a cross-sectional view taken along line 6-6 of FIG. 5;

FIG. 7 shows a cross-sectional view taken along line 7-7 of FIG. 5;

FIG. 8 shows relative positions between portions of the flow field plate of the first embodiment of the present invention and a membrane electrode assembly;

FIG. 9 shows a cross-sectional view illustrating that adjacent flow field plates of the present invention are sealed with a sealing element;

FIG. 10 schematically shows the channels of the flow field plate of the present invention to illustrate expulsion of condensed water from the channels by pressure difference;

FIG. 11 schematically shows a flow field plate constructed in accordance with a second embodiment of the present invention; and

FIG. 12 schematically shows a flow field plate constructed in accordance with a third embodiment of the present invention.

Claims

1. A gas-inlet pressure adjustment structure for a flow field plate having a central zone and a membrane electrode assembly stacked over the central zone of a fuel cell stack, comprising: at least one gas inlet opening for supplying a reaction gas to the flow field plate;at least one gas outlet opening for discharging gas from the flow field plate; anda plurality of channels in a parallel arrangement and each having a reduced open end for communicating the gas inlet opening and an expanded open end for communicating the gas outlet opening, with the reduced open end having a cross-sectional area smaller than a cross-sectional area of the expanded open end,wherein at least one water drop occurring inside the flow field plate and attached to a surface of the gas channel is expelled out of the channel by a force caused by a pressure difference induced in the reaction gas, which is supplied through the gas inlet opening and flows in sequence through the reduced open end, the gas channel, and the expanded open end and eventually discharges through the gas outlet opening.

2. The gas-inlet pressure adjustment structure as claimed in claim 1, wherein the channel further comprises a narrow channel section for communicating with the gas inlet opening via the reduced open end, a wide channel section for communicating the gas outlet opening via the expanded open end, and a divergent channel section for connecting the narrow channel section and the wide channel section.

3. The gas-inlet pressure adjustment structure as claimed in claim 1, wherein the channel further comprises a wide channel section for communicating the gas outlet opening via the expanded open end and a divergent channel section for communicating with the gas inlet opening via the reduced open end and connecting to the wide channel section.

4. The gas-inlet pressure adjustment structure as claimed in claim 1, wherein the flow field plate is an anode flow field plate of the fuel cell stack.

5. The gas-inlet pressure adjustment structure as claimed in claim 1, wherein the flow field plate is a cathode flow field plate of the fuel cell stack.

6. The gas-inlet pressure adjustment structure as claimed in claim 1, wherein the flow field plate is a bipolar plate of the fuel cell stack.

7. The gas-inlet pressure adjustment structure as claimed in claim 1, wherein the gas inlet opening serves as an inlet of hydrogen and the gas outlet opening serves as an outlet of hydrogen.

8. The gas-inlet pressure adjustment structure as claimed in claim 1, wherein the gas inlet opening serves as an inlet of an oxygen-contained gas and the gas outlet opening serves as an outlet of the oxygen-contained gas.