U.S. patent application number 09/761660 was filed with the patent office on 2001-09-27 for fuel cell system.
Invention is credited to Sang, Jochen.
Application Number | 20010024747 09/761660 |
Document ID | / |
Family ID | 7627762 |
Filed Date | 2001-09-27 |
United States Patent
Application |
20010024747 |
Kind Code |
A1 |
Sang, Jochen |
September 27, 2001 |
Fuel cell system
Abstract
A fuel cell system includes at least one fuel cell unit which is
accommodated in a fuel cell enclosure. A cathode gas delivery line,
cold-start gas delivery line, a cathode off-gas return line, anode
off-gas return line may also be provided. According to the
invention, the system is equipped with at least one Coanda flow
amplifier in order to amplify the air stream for the purpose of
ventilating the fuel cell enclosure, a cathode gas stream, a
cold-start gas stream, a recirculated cathode off-gas stream or a
recirculated anode off-gas stream. The may be equipped with a
ventilating means for a housing outside the fuel cell enclosure. In
the housing are components of the fuel cell system, said
ventilating means including a Coanda flow amplifier.
Inventors: |
Sang, Jochen;
(Kirchheim/Teck, DE) |
Correspondence
Address: |
EVENSON, McKEOWN, EDWARDS & LENAHAN, P.L.L.C.
Suite 700
1200 G Street, N.W.
Washington
DC
20005
US
|
Family ID: |
7627762 |
Appl. No.: |
09/761660 |
Filed: |
January 18, 2001 |
Current U.S.
Class: |
429/415 |
Current CPC
Class: |
Y02E 60/50 20130101;
H01M 8/04225 20160201; H01M 8/04231 20130101; H01M 8/04089
20130101 |
Class at
Publication: |
429/34 ;
429/25 |
International
Class: |
H01M 008/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 18, 2000 |
DE |
100 01 717.7 |
Claims
What is claimed is:
1. A fuel cell system comprising: a fuel cell enclosure; at least
one fuel cell unit inserted into the fuel cell enclosure; an
enclosure ventilating arrangement including a purge gas delivery
line connected to the fuel cell enclosure, a purge gas outlet line
which issues from the fuel cell enclosure, and a Coanda flow
amplifier disposed in one of the purge gas delivery line and the
purge gas outlet line.
2. The fuel cell system according to claim 1, further comprising: a
ventilating arrangement for a housing outside the fuel cell
enclosure, in which housing are components of the fuel cell system,
said ventilating means including a Coanda flow amplifier.
3. A fuel cell system claim 1, comprising: at least one fuel cell
unit having at least one of an associated cathode-gas delivery line
and a cold-start gas delivery line; and a Coanda flow amplifier
disposed in at least one of the cathode gas delivery line and the
cold-start gas delivery line.
4. A fuel cell system according to claim 3, further comprising: a
high-pressure compressor disposed upstream of the Coanda flow
amplifier on a high-pressure side thereof.
5. A fuel cell system comprising: at least one fuel cell unit
having an associated cathode off-gas return line for at least
partial recirculation of cathode off-gas to a cathode inlet side;
and a Coanda flow amplifier disposed in the cathode off-gas return
line and having its high-pressure side connected to a
compressed-air line.
6. A fuel cell system comprising: at least one fuel cell unit
having an associated anode off-gas return line; a Coanda flow
amplifier disposed in an anode off-gas return line and having its
high-pressure side connected to a fuel gas reservoir.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
[0001] This application claims the priority of German patent
document 100 01 717.7, filed Jan. 18, 2000, the disclosure of which
is expressly incorporated by reference herein.
[0002] The present invention relates to a fuel cell system having
one or more fuel cell units inserted into a fuel cell box.
Allocated to the fuel cell units are one or more of are a cathode
gas delivery line, a cold-start gas delivery line, a cathode
off-gas return line and an anode off-gas return line. Fuel cell
systems of this type are used, for example, as an energy supply for
electric vehicles.
[0003] Delivery or discharge of gas streams by a gas stream
propelling means are provided in conventional fuel cell systems;
usually by fans, blowers, ventilators and compressors. In other
fields, however, it is known to use Coanda flow amplifiers. By
supplying a driving flow medium at relatively high pressure and in
a relatively small amount, such flow amplifiers can drive a flow of
a second flow medium at relatively low pressure but high volume
flow rate by exploiting the Coanda effect. To this end the Coanda
flow amplifier designed in the form of a nozzle gap has a suitable
internal or alternatively external flow wall surface for a
wall-hugging flow of the drive medium supplied at elevated
pressure.
[0004] Coanda flow amplifiers of this type are commercially
available, for example, from EXAIR Corp. as air flow amplifiers and
also from other suppliers under the description of "air
amplifiers". Their delivered air flow can be used for cooling,
drying, cleaning or ventilation, or their aspirated air flow can be
used for the extraction of off-gases, vapors, smoke and dusts.
[0005] International patent document WO 98/32964 discloses an
internal combustion engine with exhaust gas recirculation, in which
the exhaust gas return line has a Coanda flow amplifier connected,
via its high-pressure connection, to the compressed-air source of a
compressed-air braking system of a motor vehicle. A special design
of a Coanda flow amplifier to generate a helical fluid flow is
disclosed in European patent document EP 0 456 931 B1.
[0006] One object of the present invention is to provide a fuel
cell system of the type first mentioned above, which operates with
relatively few components requiring electrical actuation.
[0007] These and other objects and advantages are achieved by the
fuel cell system according to the invention, which is equipped with
one or more Coanda flow amplifiers.
[0008] In one embodiment of the invention, a Coanda flow amplifier
is provided in a purge gas line via which purge air can be
introduced into a fuel cell box and discharged therefrom in order
to ventilate said box.
[0009] In another embodiment of the invention, a Coanda flow
amplifier is disposed in a delivery line to supply a cathode-side
gas stream to the fuel cell and/or in a delivery line via which a
cold-start gas is supplied to the at least one fuel cell unit. The
cold-start gas feeds a cold-start component which brings the system
to operating temperature as rapidly as possible in the event of a
cold start.
[0010] In still another embodiment, a Coanda flow amplifier is
provided in a cathode off-gas return line which recirculates at
least part of the cathode off-gas to the cathode inlet side,
thereby improving the water balance of the system.
[0011] In yet another embodiment, a Coanda flow amplifier is
disposed in an anode off-gas return line and is connected, via a
compressed-gas inlet, to a gas reservoir in which fuel (e.g.,
hydrogen) is stored under pressure.
[0012] In a refinement of the invention, the Coanda gas amplifier
disposed in the cathode gas delivery line and/or cold-start gas
delivery line has a high-pressure compressor connected to it on its
upstream side. The compressor pressurizes the drive gas, which is
used for gas amplification in the Coanda flow amplifier, to an
adequate pressure.
[0013] Other objects, advantages and novel features of the present
invention will become apparent from the following detailed
description of the invention when considered in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 shows a schematic block diagram of a fuel cell system
comprising a ventilatable fuel cell box, and a Coanda flow
amplifier in the associated purge air line;
[0015] FIG. 2 is a schematic depiction of the use of a Coanda flow
amplifier for a cold-start component of a fuel cell system;
[0016] FIG. 3 is a schematic depiction of a fuel cell with partial
cathode off-gas recirculation driven by a Coanda flow amplifier;
and
[0017] FIG. 4 is a schematic depiction of a fuel cell with anode
gas circulation driven by a Coanda flow amplifier.
DETAILED DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 illustrates a fuel cell system comprising one or more
fuel cell units or modules (not shown separately) arranged in a
surrounding, virtually completely closed fuel cell enclosure 1.
Associated with this enclosure 1 are ventilation means by which it
can be ventilated with purge air, particularly to avoid
accumulation of any hydrogen within the enclosure volume, which
might escape from a fuel cell module as a result of a leak.
[0019] To this end, the enclosure ventilating means comprise a
purge gas delivery line 2 which is connected to the enclosure 1,
and a purge gas outlet line 3 which issues from the enclosure 1 at
the opposite side or at a suitable location. Disposed in the purge
gas delivery line 2 is a Coanda flow amplifier 4 which, on its high
pressure side, is connected to a compressed-air line 5 via which
purge air can be supplied e.g. in the form of leakage air of the
system or transfer air of a high-pressure compressor of the system
or from some other compressed-air source of the system. As a result
of the Coanda effect of the compressed air fed in, the Coanda flow
amplifier 4 on its suction side 4a aspirates purge air from the
environment at a high volume flow rate. In the example shown, a
further enclosure 6 provided in the purge gas delivery line 2
upstream of the Coanda flow amplifier 4 accommodates peripheral
components of the fuel cell system, and is similarly ventilated by
the gas flow.
[0020] As an alternative to the arrangement of the Coanda flow
amplifier 4 between the two enclosures 1, 6 as shown in FIG. 1, it
is possible to provide a Coanda flow amplifier 4' in the section of
the purge gas delivery line 2 upstream of the peripheral enclosure
6, or for a Coanda flow amplifier 4" to be provided in the purge
gas outlet line 3 of the fuel cell enclosure 1, as shown by dashed
lines in FIG. 1 in each instance. In any case, accumulation of
leaked hydrogen in the fuel cell enclosure 1 and consequently in
the fuel cell modules arranged therein can be effectively prevented
by purging with air. Such purging can be driven solely by the
Coanda flow amplifier 4, 4', 4", without necessity of electric flow
propelling components.
[0021] The arrangement of the enclosures 1 and 6 can also be
transposed.
[0022] FIG. 2 illustrates the use of a Coanda flow amplifier 7 for
the purpose of amplifying a cold-start gas stream 8 which is
supplied to a cold-start component 9 of a fuel cell system to bring
the system to operating temperature as rapidly as possible in the
event of a cold start, as will be familiar per se to those skilled
in the art. This may involve e.g. an increased cathode air supply
and/or the delivery of a gas mixture to be used specifically during
the cold-start phase. In the example shown, amplification of the
cold-start gas stream 8 by the Coanda flow amplifier 7 is effected
by supplying the high-pressure side of the flow amplifier with
ambient air compressed to a sufficiently high pressure by a
high-pressure compressor 10. Particularly for relatively small fuel
cell systems, cathode air delivery even in the warmed-up system
state can be effected, if required, solely by means of the
arrangement of FIG. 2, the Coanda flow amplifier 7 then assuming
the function of a conventional cathode inlet air compressor.
[0023] FIG. 3 schematically illustrates a fuel cell 11 having a
cathode side 12, an anode side 13 and an intermediate membrane 14.
The anode side is supplied, via a fuel gas delivery line 15, with a
fuel gas, e.g. hydrogen. The anode off-gas discharged via an outlet
line 16 can, if required, be recirculated at least in part to the
anode inlet side, as indicated by an anode off-gas return line 17
shown by a dashed line.
[0024] The cathode side 12 is supplied, under pressure, with
ambient fresh air via a delivery line 18 and a compressor 19. In
addition, part of the cathode off-gas exiting via a cathode off-gas
line 20 is recirculated to the cathode inlet side. For this
purpose, a corresponding cathode off-gas return line 21 branches
off from the cathode off-gas line 20 via a switchable valve 22.
Disposed in the cathode off-gas return line 21 is a Coanda flow
amplifier 23 which, on its high-pressure side, is connected to a
compressed-air line 24 of a compressed-air source (not shown in any
detail) of the system.
[0025] In this implementation of the system, the Coanda flow
amplifier 23 effects gas flow propulsion, by metering in compressed
air, for the cathode off-gas to be recirculated. Thus, this
function of the fuel cell system likewise does not absolutely
depend on electrically fed flow propulsion components. Such partial
cathode offgas recirculation improves the water balance of the
system on the cathode side.
[0026] FIG. 4 again schematically shows a fuel cell 25 having a
cathode side 26, an anode side 27 and intermediate membrane 28. The
cathode side 26 is again fed with ambient air at high pressure via
a compressor 29. On the anode side, in this example, the anode
off-gas exiting on the anode gas outlet side 27a is recirculated
via an anode gas return line 30 to the anode inlet side 27b.
Disposed in the anode gas return line 30 is a Coanda flow amplifier
31. The latter is connected, on its high-pressure side, via a fuel
gas delivery line 32, to a fuel gas pressure vessel 33 in which the
fuel gas used, e.g. hydrogen, is stored under pressure. The
hydrogen can be gaseous or liquid.
[0027] During operation, the fuel gas passes, under sufficient
pressure, from the pressure vessel 33 to the Coanda flow amplifier
31, where it propels the recirculated anode gas stream and is
metered into the circulating anode-side gas stream of the fuel cell
25. The Coanda flow amplifier 31 in this case eliminates the need
for electric fuel gas metering-in components.
[0028] Initial trials of Coanda flow amplifiers at the inventive
locations of a fuel cell system such as illustrated in the
above-described specific embodiments, show surprisingly good
efficacy, which generally allows electric flow propulsion
components such as fans, blowers and ventilators to be dispensed
with at that particular location. When used in potentially
explosive atmospheres, this has the additional beneficial effect
that no elaborate safety measures are required. Moreover, cabling
and control arrangements normally required for electric flow
propulsion components can also be dispensed with.
[0029] The failure risk of Coanda flow amplifiers is extremely low,
as they do not include any moving parts. As a further advantage,
contaminants of the medium such as e.g. water droplets, do not have
any significant effect on the mode of operation of a Coanda flow
amplifier. The Coanda flow amplifier usually permits the propelled
gas mass stream to be amplified by a factor of from 10 to 30. It is
apparent that, depending on application, the fuel cell system can
be equipped with a plurality of Coanda flow amplifiers at the
positions illustrated in FIGS. 1 to 4.
[0030] Moreover it is possible for the fuel cell system to be
provided not only with the fuel cell enclosure, but also other
housings or enclosures in which components of the fuel cell system
are accommodated jointly. There too ventilation means can be
provided which advantageously include a Coanda flow amplifier in
order to purge locations or enclosures subject to explosion
hazards. For example, the Coanda flow amplifier can also be
employed in the field of peripheral units of the fuel cell and/or
in the field of off-gas cleaning of the fuel cell system outside
the fuel cell enclosure.
[0031] The foregoing disclosure has been set forth merely to
illustrate the invention and is not intended to be limiting. Since
modifications of the disclosed embodiments incorporating the spirit
and substance of the invention may occur to persons skilled in the
art, the invention should be construed to include everything within
the scope of the appended claims and equivalents thereof.
* * * * *