U.S. patent application number 17/034165 was filed with the patent office on 2021-11-25 for condensate water drain control system and method for fuel cells.
The applicant listed for this patent is Hyundai Motor Company, Kia Motors Corporation. Invention is credited to Soon Woo Kwon, Dong Hun Lee, Joon Yong Lee, Sung Gone Yoon.
Application Number | 20210367247 17/034165 |
Document ID | / |
Family ID | 1000005130791 |
Filed Date | 2021-11-25 |
United States Patent
Application |
20210367247 |
Kind Code |
A1 |
Lee; Joon Yong ; et
al. |
November 25, 2021 |
CONDENSATE WATER DRAIN CONTROL SYSTEM AND METHOD FOR FUEL CELLS
Abstract
A condensate water drain control system for fuel cells includes
a fuel cell stack configured to generate electric power through
chemical reaction, a fuel supply line configured to recirculate
fuel discharged from the fuel cell stack together with fuel
introduced from a fuel supply valve, a water trap located in the
fuel supply line, the water trap being configured to collect
condensate water discharged from the fuel cell stack, a drain valve
configured to discharge the condensate water stored in the water
trap to the outside when opened, and a drain controller configured
to determine whether the fuel supply valve is controlled such that
pressure in the fuel supply line is maintained before the drain
valve is opened and to sense discharge of fuel from the fuel supply
line through the drain valve upon determining that the pressure is
maintained.
Inventors: |
Lee; Joon Yong; (Seoul,
KR) ; Lee; Dong Hun; (Anyang, KR) ; Kwon; Soon
Woo; (Yongin, KR) ; Yoon; Sung Gone; (Suwon,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hyundai Motor Company
Kia Motors Corporation |
Seoul
Seoul |
|
KR
KR |
|
|
Family ID: |
1000005130791 |
Appl. No.: |
17/034165 |
Filed: |
September 28, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 8/04164 20130101;
H01M 8/04753 20130101; H01M 2250/20 20130101; H01M 8/0494 20130101;
H01M 8/04201 20130101; H01M 8/04947 20130101; H01M 8/04179
20130101 |
International
Class: |
H01M 8/04119 20060101
H01M008/04119; H01M 8/04746 20060101 H01M008/04746; H01M 8/04082
20060101 H01M008/04082; H01M 8/04828 20060101 H01M008/04828 |
Foreign Application Data
Date |
Code |
Application Number |
May 19, 2020 |
KR |
10-2020-0059600 |
Claims
1. A condensate water drain control system for fuel cells, the
condensate water drain control system comprising: a fuel cell stack
configured to generate electric power through chemical reaction in
the fuel cell stack; a fuel supply line configured to recirculate
fuel discharged from the fuel cell stack together with fuel
introduced from a fuel supply valve so as to be supplied to the
fuel cell stack; a water trap located in the fuel supply line, the
water trap being configured to collect condensate water discharged
from the fuel cell stack; a drain valve located in an outlet of the
water trap, the drain valve being configured to discharge the
condensate water stored in the water trap to an outside when
opened; and a drain controller configured to determine whether the
fuel supply valve is controlled such that pressure in the fuel
supply line is maintained before the drain valve is opened and to
sense discharge of fuel from the fuel supply line through the drain
valve upon determining that the pressure is maintained.
2. The condensate water drain control system according to claim 1,
wherein the drain controller determines whether the fuel supply
valve is controlled such that the pressure in the fuel supply line
is maintained based on a change in pressure in the fuel supply line
or a change in opening degree of the fuel supply valve in a state
in which the drain valve is closed.
3. The condensate water drain control system according to claim 2,
further comprising: a pressure sensor configured to sense the
pressure in the fuel supply line, wherein the drain controller
determines whether the fuel supply valve is controlled such that
the pressure in the fuel supply line is maintained based on a
change in a pressure signal sensed by the pressure sensor.
4. The condensate water drain control system according to claim 2,
further comprising: a fuel tank configured to store fuel in the
fuel tank; and a fuel supply controller configured to control the
opening degree of the fuel supply valve such that the pressure in
the fuel supply line follows a target pressure, wherein the drain
controller determines whether the fuel supply valve is controlled
such that the pressure in the fuel supply line is maintained based
on a change in a signal for controlling the opening degree of the
fuel supply valve from the fuel supply controller.
5. The condensate water drain control system according to claim 4,
wherein the fuel supply controller fixes the target pressure in the
fuel supply line in a case in which opening of the drain valve is
required.
6. The condensate water drain control system according to claim 1,
further comprising a power controller configured to fix required
current or required power of the fuel cell stack in a case in which
opening of the drain valve is required.
7. The condensate water drain control system according to claim 6,
further comprising: a battery configured to be assist generation of
electric power by the fuel cell stack while being charged or
discharged by electric power generated by the fuel cell stack; and
a load connected to the fuel cell stack and the battery to receive
electric power from the fuel cell stack or the battery, wherein the
power controller controls the required current or required power of
the fuel cell stack based on required power of the load or a charge
amount of the battery, and controls charging and discharging of the
battery in order to satisfy the required power of the load in a
case in which the required current or required power of the fuel
cell stack is fixed.
8. The condensate water drain control system according to claim 1,
wherein the drain controller senses the discharge of fuel from the
fuel supply line through the drain valve based on a change in
pressure in the fuel supply line or a change in opening degree of
the fuel supply valve in a state in which the drain valve is
open.
9. The condensate water drain control system according to claim 1,
wherein: the drain valve is configured to have a purge function of
purging fuel in the fuel supply line to the outside when opened,
and the drain controller measures a purge time from a point in time
when the discharge of fuel from the fuel supply line through the
drain valve is sensed to a point in time when the drain valve is
closed.
10. The condensate water drain control system according to claim 1,
further comprising a concentration estimator configured to estimate
an amount purged by opening of the drain valve and to estimate
concentration of fuel in the fuel supply line through reflection of
the estimated purge amount.
11. A condensate water drain control method for fuel cells, the
condensate water drain control method comprising the steps of:
determining, by a drain controller, whether a fuel supply valve is
controlled such that pressure is maintained in a fuel supply line,
which is configured to recirculate fuel discharged from a fuel cell
stack together with fuel introduced from the fuel supply valve so
as to be supplied to the fuel cell stack; opening, by the drain
controller, a drain valve located in an outlet of a water trap
located in the fuel supply line, the water trap being configured to
collect condensate water discharged from the fuel cell stack, the
drain valve being configured to discharge condensate water stored
in the water trap to an outside when opened; and sensing, by the
drain controller, discharge of fuel from the fuel supply line
through the drain valve upon determining in the determining step
that the pressure is maintained.
12. The condensate water drain control method according to claim
11, wherein the step of determining whether the fuel supply valve
is controlled such that the pressure in the fuel supply line is
maintained comprises determining whether the fuel supply valve is
controlled such that the pressure in the fuel supply line is
maintained based on a change in pressure in the fuel supply line or
a change in opening degree of the fuel supply valve in a state in
which the drain valve is closed.
13. The condensate water drain control method according to claim
11, further comprising: determining whether opening of the drain
valve is required before the step of determining whether the fuel
supply valve is controlled such that the pressure in the fuel
supply line is maintained; and fixing a target pressure in the fuel
supply line or fixing required current or required power of the
fuel cell stack upon determining that opening of the drain valve is
required.
14. The condensate water drain control method according to claim
11, further comprising: measuring a purge time from a point in time
when the discharge of fuel from the fuel supply line through the
drain valve is sensed to a point in time when the drain valve is
closed after the step of sensing the discharge of fuel; estimating
an amount purged by opening of the drain valve based on the
measured purge time; and estimating concentration of fuel in the
fuel supply line through reflection of the estimated purge
amount.
15. A condensate water drain control system for fuel cells, the
condensate water drain control system comprising: a fuel cell stack
configured to generate electric power through chemical reaction in
the fuel cell stack; a fuel supply line configured to recirculate
fuel discharged from the fuel cell stack together with fuel
introduced from a fuel supply valve so as to be supplied to the
fuel cell stack; a water trap located in the fuel supply line, the
water trap being configured to collect condensate water discharged
from the fuel cell stack; a drain valve located in an outlet of the
water trap, the drain valve being configured to discharge the
condensate water stored in the water trap to an outside when
opened; a drain controller configured to sense discharge of fuel
from the fuel supply line through the drain valve; and a fuel
supply controller configured to control the fuel supply valve such
that pressure in the fuel supply line is maintained when the drain
valve is opened under control of the drain controller.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims under 35 U.S.C. .sctn. 119(a) the
benefit of Korean Patent Application No. 10-2020-0059600, filed on
May 19, 2020 with the Korean Intellectual Property Office, the
entire contents of which are incorporated by reference herein.
BACKGROUND
1. Technical Field
[0002] The present disclosure relates to a condensate water drain
control system and method for fuel cells, more particularly, to the
condensate water drain control system and method that are
configured to sense hydrogen discharged from a hydrogen supply line
by opening of a drain valve.
2. Description of the Related Art
[0003] A fuel cell is a battery that directly converts chemical
energy generated as the result of oxidation of fuel into electrical
energy, and thus serves as a type of power generation device. A
fuel cell is similar to a chemical cell in that reduction-oxidation
is used, but is different from the chemical cell in that a reactant
is continuously introduced from the outside and a reaction product
is continuously discharged out of a system, unlike the chemical
cell, which is configured such that cell reaction occurs in a
closed system. In recent years, a fuel cell generation system has
been used practically, e.g., in a fuel cell vehicle, and research
into using a fuel cell as an energy source for
environmentally-friendly vehicles has been actively conducted,
since a reaction product from the fuel cell is pure water.
[0004] A fuel cell system includes a fuel cell stack configured to
generate electric energy through chemical reaction, an air supply
device configured to supply air to an air electrode of the fuel
cell stack, and a hydrogen supply device configured to supply
hydrogen to a hydrogen electrode of the fuel cell stack.
[0005] When electric power is generated in the fuel cell stack,
water is generated in the fuel cell stack. Some of the water is
discharged to the hydrogen electrode through an electrolyte
membrane due to a concentration difference. Hydrogen gas is
recirculated to the hydrogen supply device through a recirculation
device, and the water discharged from the hydrogen electrode is
condensed and is stored in a water trap included in the hydrogen
supply device.
[0006] The water trap includes a water level sensor. When the level
of condensate water sensed by the water level sensor is greater
than or equal to a predetermined discharge level, a drain valve is
opened to discharge the stored condensate water to the outside. In
addition, when the level of condensate water sensed by the water
level sensor is greater than or equal to a predetermined
interruption level, the drain valve is closed to prevent the
discharge of hydrogen.
[0007] In a case in which the water level sensor of the water trap
breaks, however, it is not possible to measure the level of
condensate water stored in the water trap, whereby it is not
possible to appropriately control the drain valve. In particular,
when condensate water in the hydrogen supply device is not smoothly
discharged to the outside, the water generated in the fuel cell
stack cannot be discharged to the outside, whereby flow channels in
a separator are blocked. If the drain valve is opened more than
necessary, hydrogen is unnecessarily discharged, whereby fuel
economy is deteriorated.
[0008] Conventionally, in order to solve this problem, fail-safe
control is performed to open the drain valve when, based on a
current integration value obtained by integrating current generated
in the fuel cell stack, the current integration value reaches a
predetermined value in the case in which the water level sensor of
the water trap breaks. Since the amount of condensate water stored
in the water trap is not uniform depending on the state of the fuel
cell stack, however, it is not possible to accurately measure the
level of the water trap.
[0009] To address this problem, a method of measuring the pressure
in the hydrogen supply line in the state in which the drain valve
is open is used. In the case in which target pressure in the
hydrogen supply line is variable in the state in which the drain
valve is open, however, the discharge of hydrogen is falsely
detected despite hydrogen not being discharged from the hydrogen
supply line.
[0010] The matters disclosed in this section are merely for
enhancement of understanding of the general background of the
disclosure and should not be taken as an acknowledgment or any form
of suggestion that the matters form the related art already known
to a person skilled in the art.
SUMMARY
[0011] The present disclosure provides technology for accurately
sensing the discharge of hydrogen from a hydrogen supply line by
opening of a drain valve.
[0012] In accordance with an aspect of the present disclosure, the
above and other objects can be accomplished by the provision of a
condensate water drain control system for fuel cells, the
condensate water drain control system including a fuel cell stack
configured to generate electric power through chemical reaction in
the fuel cell stack, a fuel supply line configured to recirculate
fuel discharged from the fuel cell stack together with fuel
introduced from a fuel supply valve so as to be supplied to the
fuel cell stack, a water trap located in the fuel supply line, the
water trap being configured to collect condensate water discharged
from the fuel cell stack, a drain valve located in an outlet of the
water trap, the drain valve being configured to discharge the
condensate water stored in the water trap to the outside when
opened, and a drain controller configured to determine whether the
fuel supply valve is controlled such that pressure in the fuel
supply line is maintained before the drain valve is opened and to
sense discharge of fuel from the fuel supply line through the drain
valve upon determining that the pressure is maintained.
[0013] The drain controller may determine whether the fuel supply
valve is controlled such that the pressure in the fuel supply line
is maintained based on a change in pressure in the fuel supply line
or a change in opening degree of the fuel supply valve in the state
in which the drain valve is closed.
[0014] The condensate water drain control system may further
include a pressure sensor configured to sense the pressure in the
fuel supply line, wherein the drain controller may determine
whether the fuel supply valve is controlled such that the pressure
in the fuel supply line is maintained based on a change in a
pressure signal sensed by the pressure sensor.
[0015] The condensate water drain control system may further
include a fuel tank configured to store fuel in the fuel tank and a
fuel supply controller configured to control the opening degree of
the fuel supply valve such that the pressure in the fuel supply
line follows a target pressure, wherein the drain controller may
determine whether the fuel supply valve is controlled such that the
pressure in the fuel supply line is maintained based on a change in
a signal for controlling the opening degree of the fuel supply
valve from the fuel supply controller.
[0016] The fuel supply controller may fix the target pressure in
the fuel supply line in the case in which opening of the drain
valve is required.
[0017] The condensate water drain control system may further
include a power controller configured to fix required current or
required power of the fuel cell stack in the case in which opening
of the drain valve is required.
[0018] The condensate water drain control system may further
include a battery configured to be assist generation of electric
power by the fuel cell stack while being charged or discharged by
electric power generated by the fuel cell stack and a load
connected to the fuel cell stack and the battery to receive
electric power from the fuel cell stack or the battery, wherein the
power controller may control the required current or required power
of the fuel cell stack based on required power of the load or a
charge amount of the battery, and may control charging and
discharging of the battery in order to satisfy the required power
of the load in the case in which the required current or required
power of the fuel cell stack is fixed.
[0019] The drain controller may sense the discharge of fuel from
the fuel supply line through the drain valve based on a change in
pressure in the fuel supply line or a change in opening degree of
the fuel supply valve in the state in which the drain valve is
open.
[0020] The drain valve may be configured to have a purge function
of purging fuel in the fuel supply line to the outside when opened,
and the drain controller may measure a purge time from the point in
time when the discharge of fuel from the fuel supply line through
the drain valve is sensed to the point in time when the drain valve
is closed.
[0021] The condensate water drain control system may further
include a concentration estimator configured to estimate an amount
purged by opening of the drain valve and to estimate concentration
of fuel in the fuel supply line through reflection of the estimated
purge amount.
[0022] In accordance with another aspect of the present disclosure,
there is provided a condensate water drain control system for fuel
cells, the condensate water drain control system including a fuel
cell stack configured to generate electric power through chemical
reaction in the fuel cell stack, a fuel supply line configured to
recirculate fuel discharged from the fuel cell stack together with
fuel introduced from a fuel supply valve so as to be supplied to
the fuel cell stack, a water trap located in the fuel supply line,
the water trap being configured to collect condensate water
discharged from the fuel cell stack, a drain valve located in an
outlet of the water trap, the drain valve being configured to
discharge the condensate water stored in the water trap to the
outside when opened, a drain controller configured to sense the
discharge of fuel from the fuel supply line through the drain
valve, and a fuel supply controller configured to control the fuel
supply valve such that pressure in the fuel supply line is
maintained when the drain valve is opened under control of the
drain controller.
[0023] In accordance with a further aspect of the present
disclosure, there is provided a condensate water drain control
method for fuel cells, the condensate water drain control method
including: determining, by a drain controller, whether a fuel
supply valve is controlled such that pressure is maintained in a
fuel supply line, which is configured to recirculate fuel
discharged from a fuel cell stack together with fuel introduced
from the fuel supply valve so as to be supplied to the fuel cell
stack; opening, by the drain controller, a drain valve located in
an outlet of a water trap located in the fuel supply line, the
water trap being configured to collect condensate water discharged
from the fuel cell stack, the drain valve being configured to
discharge condensate water stored in the water trap to an outside
when opened; and sensing, by the drain controller, discharge of
fuel from the fuel supply line through the drain valve upon
determining in the determining step that the pressure is
maintained.
[0024] The step of determining whether the fuel supply valve is
controlled such that the pressure in the fuel supply line is
maintained may include determining whether the fuel supply valve is
controlled such that the pressure in the fuel supply line is
maintained based on a change in pressure in the fuel supply line or
a change in opening degree of the fuel supply valve in the state in
which the drain valve is closed.
[0025] The condensate water drain control method may further
include determining whether opening of the drain valve is required
before the step of determining whether the fuel supply valve is
controlled such that the pressure in the fuel supply line is
maintained and fixing a target pressure in the fuel supply line or
fixing required current or required power of the fuel cell stack
upon determining that opening of the drain valve is required.
[0026] The condensate water drain control method may further
include measuring a purge time from the point in time when the
discharge of fuel from the fuel supply line through the drain valve
is sensed to the point in time when the drain valve is closed after
the step of sensing the discharge of fuel, estimating an amount
purged by opening of the drain valve based on the measured purge
time, and estimating concentration of fuel in the fuel supply line
through reflection of the estimated purge amount.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The above and other objects, features and other advantages
of the present disclosure will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0028] FIG. 1 is a view showing the construction of a condensate
water drain control system for fuel cells according to an
embodiment of the present disclosure;
[0029] FIG. 2 is a view showing conventional condensate water drain
and fuel supply control signals; and
[0030] FIG. 3 is a flowchart showing a condensate water drain
control method for fuel cells according to an embodiment of the
present disclosure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] It is understood that the term "vehicle" or "vehicular" or
other similar term as used herein is inclusive of motor vehicles in
general such as passenger automobiles including sports utility
vehicles (SUV), buses, trucks, various commercial vehicles,
watercraft including a variety of boats and ships, aircraft, and
the like, and includes hybrid vehicles, electric vehicles, plug-in
hybrid electric vehicles, hydrogen-powered vehicles and other
alternative fuel vehicles (e.g. fuels derived from resources other
than petroleum). As referred to herein, a hybrid vehicle is a
vehicle that has two or more sources of power, for example both
gasoline-powered and electric-powered vehicles.
[0032] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the disclosure. As used herein, the singular forms "a," "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, and/or components, but do not preclude
the presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof. As
used herein, the term "and/or" includes any and all combinations of
one or more of the associated listed items. Throughout the
specification, unless explicitly described to the contrary, the
word "comprise" and variations such as "comprises" or "comprising"
will be understood to imply the inclusion of stated elements but
not the exclusion of any other elements. In addition, the terms
"unit", "-er", "-or", and "module" described in the specification
mean units for processing at least one function and operation, and
can be implemented by hardware components or software components
and combinations thereof.
[0033] Further, the control logic of the present disclosure may be
embodied as non-transitory computer readable media on a computer
readable medium containing executable program instructions executed
by a processor, controller or the like. Examples of computer
readable media include, but are not limited to, ROM, RAM, compact
disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart
cards and optical data storage devices. The computer readable
medium can also be distributed in network coupled computer systems
so that the computer readable media is stored and executed in a
distributed fashion, e.g., by a telematics server or a Controller
Area Network (CAN).
[0034] Specific structural or functional descriptions of the
embodiments of the present disclosure disclosed in this
specification or this disclosure are given only for illustrating
embodiments of the present disclosure. Embodiments of the present
disclosure may be realized in various forms, and should not be
interpreted to be limited to the embodiments of the present
disclosure disclosed in this specification or this disclosure.
[0035] Since the embodiments of the present disclosure may be
variously modified and may have various forms, specific embodiments
will be shown in the drawings and will be described in detail in
this specification or this disclosure. However, the embodiments
according to the concept of the present disclosure are not limited
to such specific embodiments, and it should be understood that the
present disclosure includes all alterations, equivalents, and
substitutes that fall within the idea and technical scope of the
present disclosure.
[0036] It will be understood that, although the terms "first",
"second", etc. may be used herein to describe various elements,
corresponding elements should not be understood to be limited by
these terms, which are used only to distinguish one element from
another. For example, within the scope defined by the present
disclosure, a first element may be referred to as a second element,
and similarly, a second element may be referred to as a first
element.
[0037] It will be understood that when a component is referred to
as being "connected to" or "coupled to" another component, it may
be directly connected to or coupled to the other component, or
intervening components may be present. In contrast, when a
component is referred to as being "directly connected to" or
"directly coupled to" another component, there are no intervening
components present. Other terms that describe the relationship
between components, such as "between" and "directly between" or
"adjacent to" and "directly adjacent to", must be interpreted in
the same manner.
[0038] Reference will now be made in detail to the preferred
embodiments of the present disclosure, examples of which are
illustrated in the accompanying drawings. Wherever possible, the
same reference numbers will be used throughout the drawings to
refer to the same or like parts.
[0039] FIG. 1 is a view showing the construction of a condensate
water drain control system for fuel cells according to an
embodiment of the present disclosure.
[0040] Referring to FIG. 1, the condensate water drain control
system for fuel cells according to the embodiment of the present
disclosure includes a fuel cell stack 10 configured to generate
electric power through chemical reaction in the fuel cell stack 10,
a fuel supply line 20 configured to recirculate fuel discharged
from the fuel cell stack 10 together with fuel introduced from a
fuel supply valve 42 so as to be supplied to the fuel cell stack
10, a water trap 30 located in the fuel supply line 20, the water
trap 30 being configured to collect condensate water discharged
from the fuel cell stack 10, a drain valve 32 located in an outlet
31 of the water trap 30, the drain valve 32 being configured to
discharge the condensate water stored in the water trap 30 to the
outside when opened, and a drain controller 50 configured to
determine whether the fuel supply valve 42 is controlled such that
the pressure in the fuel supply line 20 is maintained before the
drain valve 32 is opened and to sense the discharge of fuel from
the fuel supply line 20 through the drain valve 32 upon determining
that the pressure of the fuel supply line 20 is maintained.
[0041] The fuel cell stack 10 receives air including hydrogen and
oxygen, as fuel, from a hydrogen electrode (anode) and an oxygen
electrode (cathode), and generates electric power through chemical
reaction. In the fuel cell stack 10, hydrogen and oxygen react with
each other, whereby condensate water is generated.
[0042] The fuel supply line 20 supplies fuel from a fuel tank 41 to
the fuel cell stack 10 and supplies fuel discharged from the fuel
cell stack 10 to the fuel cell stack 10 through recirculation. That
is, fuel discharged from the fuel cell stack 10 is supplied to the
fuel cell stack 10 through recirculation in the state of being
mixed with fuel supplied from the fuel tank 41.
[0043] The water trap 30 is provided in the fuel supply line 20 to
store condensate water generated in the fuel cell stack 10. In
particular, condensate water generated by the oxygen electrode of
the fuel cell stack 10 and moved to the fuel supply line 20 as the
result of diffusion to the hydrogen electrode is collected and
stored in the water trap 30. The outlet 31 of the water trap 30 may
be connected to the outside, or may be to a humidifier located in
an oxygen electrode inlet of the fuel cell stack 10 in order to
supply moisture.
[0044] The drain valve 32 may be provided in the outlet 31 of the
water trap 30 to control the discharge of condensate water from the
water trap 30. In particular, the drain valve 32 may allow the
discharge of condensate water stored in the water trap 30 when
opened, and may block the discharge of condensate water when
closed.
[0045] In general, the drain valve 32 is controlled to be closed
such that hydrogen is not discharged through the outlet 31 of the
water trap 30, and is opened to discharge condensate water to the
outside when the condensate water is intermittently stored.
[0046] The drain controller 50 may control opening and closing of
the drain valve 32. In particular, the drain controller 50 may
sense or predict the level of condensate water stored in the water
trap 30, may perform control such that the drain valve 32 is opened
in the state in which the level of condensate water is high, and
perform control such that the drain valve 32 is closed when the
level of condensate water is lowered as the result of opening of
the drain valve 32.
[0047] FIG. 2 is a view showing conventional condensate water drain
and fuel supply control signals.
[0048] Referring further to FIG. 2, conventionally, the water trap
30 includes a water level sensor 33 configured to sense the amount
of condensate water stored in the water trap 30, and opening and
closing of the drain valve 32 are controlled using the water level
sensor 33.
[0049] In particular, when the storage amount of condensate water
sensed by the water level sensor 33 is greater than or equal to a
predetermined high-level critical value, the drain valve 32 is
controlled to be opened, and when the storage amount of condensate
water is less than or equal to a predetermined low-level critical
value, the drain valve 32 is controlled to be closed.
[0050] However, the water level sensor 33 frequently malfunctions,
whereby sensing accuracy is low and responsiveness is slow. As in
an abnormal discharge state of FIG. 2, therefore, the drain valve
32 remains open, whereby hydrogen is discharged through the outlet
31, even when the discharge of condensate water is completed.
[0051] Conventionally, in order to solve this, control is performed
such that the drain valve 32 is opened whenever the integrated
value of output current of the fuel cell at the time of malfunction
of the water level sensor 33 reaches a predetermined integrated
current value, is maintained open for a predetermined opening time,
and is then closed. However, opening and closing of the drain valve
32 are controlled irrespective of the amount of condensate water
stored in the water trap 30, which causes the discharge of hydrogen
or flooding of the fuel cell stack 10.
[0052] In order to estimate the amount of condensate water stored
in the water trap 30 and to perform control based thereon even at
the time of breakdown of the water level sensor 33, the drain
controller 50 senses whether fuel is discharged from the fuel
supply line 20 through the outlet 31 in the state in which the
drain valve 32 is open, and performs control such that the drain
valve 32 is closed upon sensing the discharge of fuel.
[0053] In particular, the fuel supply valve 42 controls the
pressure in the fuel supply line 20 so as to follow target pressure
(PI control), and the drain controller 50 senses the discharge of
fuel through the outlet 31 based on a signal for controlling the
opening degree of the fuel supply valve 42 in the state in which
the drain valve 32 is open.
[0054] However, in the case in which such control is followed, as
shown in FIG. 2, when the target pressure in the fuel supply line
20 is changed in the state in which the drain valve 32 is open, the
pressure in the fuel supply line 20 and the control signal of the
fuel supply valve 42 are variable, whereby fuel is misjudged to be
discharged even in the case in which no fuel is discharged through
the drain valve 32 (false detection of hydrogen discharge
state).
[0055] According to the present disclosure, in order to solve this
problem, the drain controller 50 may determine whether the fuel
supply valve 42 is controlled such that the pressure in the fuel
supply line 20 is maintained when the drain valve 32 is opened, and
upon determining that the fuel supply valve is controlled such that
the pressure of the fuel supply line is maintained, may sense the
discharge of fuel from the fuel supply line 20 through the drain
valve 32 in the state in which the drain valve 32 is open.
[0056] Consequently, the drain controller 50 may accurately sense
the discharge of fuel through the drain valve 32 in the state in
which the drain valve 32 is open, and therefore it is possible to
prevent misjudgment of fuel discharge due to a change in pressure
in the fuel supply line 20 due to another environmental change.
[0057] Here, that the fuel supply valve 42 is controlled such that
the pressure in the fuel supply line 20 is maintained means that
the fuel supply valve 42 is controlled such that the pressure in
the fuel supply line 20 is maintained except that the pressure in
the fuel supply line 20 is changed as the result of the discharge
of fuel from the fuel supply line 20 through the drain valve 32.
That is, a change in pressure in the fuel supply line 20 due to
other factors is minimized in the state in which the drain valve 32
is open.
[0058] In particular, the drain controller 50 may determine whether
the fuel supply valve 42 is controlled such that the pressure in
the fuel supply line 20 is maintained based on a change in pressure
in the fuel supply line 20 or a change in opening degree of the
fuel supply valve 42 in the state in which the drain valve 32 is
closed.
[0059] In an embodiment, a pressure sensor 21 configured to sense
the pressure in the fuel supply line 20 may be further included,
and the drain controller 50 may determine whether the fuel supply
valve 42 is controlled such that the pressure in the fuel supply
line 20 is maintained based on a change in a pressure signal sensed
by the pressure sensor 21.
[0060] In particular, the pressure sensor 21 may be located in the
fuel supply line 20 at the inlet side of the fuel cell stack 10 and
may sense the pressure in the fuel supply line 20, and a fuel
supply controller 40, a description of which will follow, may
adjust the opening degree of the fuel supply valve 42 based on the
pressure in the fuel supply line 20 sensed by the pressure sensor
21.
[0061] In particular, the drain controller 50 may differentiate the
pressure signal sensed by the pressure sensor 21 or calculate
variation (absolute value) from a previous sensing value, and may
determine that the fuel supply valve 42 is controlled such that the
pressure in the fuel supply line 20 is maintained in the case in
which the calculated differential value or variation is maintained
within a predetermined range for a period of time greater than or
equal to a predetermined maintenance time.
[0062] In another embodiment, a fuel tank 41 configured to store
fuel in the fuel tank 41 and a fuel supply controller 40 configured
to control the opening degree of the fuel supply valve 42 such that
the pressure in the fuel supply line 20 follows the target pressure
may be further included, and the drain controller 50 may determine
whether the fuel supply valve 42 is controlled such that the
pressure in the fuel supply line 20 is maintained based on a change
in a signal for controlling the opening degree of the fuel supply
valve 42 from the fuel supply controller 40.
[0063] The fuel tank 41 may store high-pressure hydrogen in the
fuel tank 41, and may supply the stored hydrogen to the fuel supply
line 20 through the fuel supply valve 42. In particular, the
high-pressure hydrogen stored in the fuel tank 41 may be supplied
to the fuel supply line 20 after being decompressed.
[0064] The fuel supply controller 40 may control opening and
closing of the fuel supply valve 42 based on the pressure in the
fuel supply line 20, and the signal for controlling the opening
degree of the fuel supply valve 42 may be output from the fuel
supply controller 40.
[0065] In particular, the fuel supply controller 40 may control
opening and closing of the fuel supply valve 42 based on the target
pressure in the fuel supply line 20 and the pressure and
temperature in the fuel supply line 20. That is, the signal for
controlling the opening degree of the fuel supply valve 42 may be
set based on the target pressure in the fuel supply line 20 and the
pressure and temperature in the fuel supply line 20.
[0066] The drain controller 50 may differentiate the signal for
controlling the opening degree of the fuel supply valve 42 from the
fuel supply controller 40 or calculate variation (absolute value)
from a previous control value, and may determine that the fuel
supply valve 42 is controlled such that the pressure in the fuel
supply line 20 is maintained in the case in which the calculated
differential value or variation is maintained within a
predetermined range for a period of time greater than or equal to a
predetermined maintenance time.
[0067] Referring to FIG. 2, variation in a pressure signal of the
fuel supply line 20 is relatively small, whereby it is difficult to
sense the discharge of fuel through the drain valve 32; however,
variation in a control signal of the fuel supply valve 42 is
relatively large, whereby it is possible to rapidly, accurately,
and easily sense the discharge of fuel.
[0068] In an embodiment, the fuel supply controller 40 may fix the
target pressure in the fuel supply line 20 in the case in which
opening of the drain valve 32 is required.
[0069] The fuel supply controller 40 may set the target pressure in
the fuel supply line 20 based on required current or required power
of the fuel cell. Particularly, in the case in which opening of the
drain valve 32 is required, the fuel supply controller 40 may fix
the target pressure in the fuel supply line 20 even though the
required current or required power of the fuel cell is
variable.
[0070] In another embodiment, a power controller configured to fix
the required current or required power of the fuel cell in the case
in which opening of the drain valve 32 is required may be further
included.
[0071] The power controller may control the required current or
required power of the fuel cell based on required current or
required power of a load and the charge amount of a battery 80, a
description of which will follow. That is, the power controller may
set the required current or required power of the fuel cell in
order to satisfy the required current of the load, which is changed
in real time. However, the power controller may perform control
such that the required current or required power of the fuel cell
is fixed in the case in which opening of the drain valve 32 is
required.
[0072] A battery 80 configured to assist generation of electric
power by the fuel cell stack 10 while being charged or discharged
by electric power generated by the fuel cell stack 10 and a load
connected to the fuel cell stack 10 and the battery 80 to receive
electric power from the fuel cell stack 10 or the battery 80 may be
further included.
[0073] That is, the fuel cell stack 10 and the load may be
connected to each other via a main bus end, and the battery 80 may
be connected to the main bus end in parallel. In particular, a
high-voltage converter 81 may be located between the main bus end
and the battery 80, and the power controller may control the
high-voltage converter 81 to control charging and discharging of
the battery 80.
[0074] The power controller may control the required current or
required power of the fuel cell based on the required power of the
load or the charge amount of the battery 80, and may control
charging and discharging of the battery 80 in order to satisfy the
required power of the load in the case in which the required
current or required power of the fuel cell is fixed.
[0075] That is, the power controller may satisfy the required power
of the load through charging and discharging of the battery 80 when
the required power of the load is variable in the case in which the
required current or required power of the fuel cell is fixed.
[0076] In particular, required power Pt of the load may be the sum
of required power Ps of the fuel cell stack 10 and auxiliary power
Pb of the battery 80.
Pt=Ps+Pb->Pb=Pt-Ps
On the assumption that voltage of the main bus end between the fuel
cell stack and the load is V, discharge current Ib of the battery
80 is as follows.
Ib=Pt/V-Is
[0077] Here, in the case in which required current Is of the fuel
cell stack 10 is fixed and the required power Pt of the load is
variable, the discharge current Ib of the battery 80 may be
variable to satisfy the required power Pt of the load.
[0078] Particularly, in the case in which Ib>0, which is the
state in which the battery 80 is discharged, the power controller
may control voltage of the high-voltage converter 81 to be
Vref=V+.alpha. such that the battery 80 is discharged.
[0079] On the other hand, in the case in which Ib<0, which is
the state in which the battery 80 is charged, the power controller
may control voltage of the high-voltage converter 81 to be
Vref=V-.alpha. such that the battery 80 is charged.
[0080] The drain controller 50 may control opening of the drain
valve 32 based on the storage amount of condensate water sensed by
the water level sensor 33. For example, when the storage amount of
condensate water sensed by the water level sensor 33 is greater
than or equal to a predetermined high-level critical value, the
drain controller may determine that opening of the drain valve 32
is required.
[0081] In addition, when the storage amount of condensate water
sensed by the water level sensor 33 is less than or equal to a
predetermined low-level critical value, or when the discharge of
fuel through the outlet 31 is sensed in the state in which the
drain valve 32 is open, the drain controller 50 may perform control
such that the drain valve 32 is closed.
[0082] In particular, the drain controller 50 may sense the
discharge of fuel from the fuel supply line 20 through the drain
valve 32 based on a change in pressure in the fuel supply line 20
or a change in opening degree of the fuel supply valve 42 in the
state in which the drain valve 32 is open.
[0083] The drain controller 50 may sense the discharge of fuel from
the fuel supply line 20 through the drain valve 32 based on a
pressure signal sensed by the pressure sensor 21 or a signal for
controlling the opening degree of the fuel supply valve 42 output
from the fuel supply controller 40.
[0084] In an embodiment, in the case in which a rate of change in
the signal for controlling the opening degree of the fuel supply
valve 42 output from the fuel supply controller 40 is greater than
or equal to a predetermined rate of change, the drain controller 50
may sense that fuel has been discharged.
[0085] In the case in which the rate of change over time in the
signal for controlling the opening degree of the fuel supply valve
42 output from the fuel supply controller 40 is abruptly variable
to greater than or equal to the predetermined rate of change, it
may be determined that the pressure in the fuel supply line 20 is
abruptly changed, and therefore it may be determined that fuel has
been discharged through the outlet 31.
[0086] In another embodiment, in the case in which a difference
between the signal for controlling the opening degree of the fuel
supply valve 42 output from the fuel supply controller 40 and an
output signal reference value based on a pre-mapped output signal
map is greater than or equal to a predetermined error, it may be
sensed that fuel has been discharged.
[0087] In the pre-mapped output signal map, the output signal
reference value may be pre-mapped based on the target pressure in
the fuel supply line 20 and the temperature in the fuel supply line
20, and in the case in which the difference between the output
signal reference value based on the pre-mapped output signal map
and the signal for controlling the opening degree of the fuel
supply valve 42 output from the fuel supply controller 40 is
greater than or equal to the predetermined error, it may be
determined that the pressure in the fuel supply line 20 is abruptly
changed, and therefore it may be determined that fuel has been
discharged through the outlet 31.
[0088] In another embodiment, it may be sensed that fuel has been
discharged at an inflection point at which a peak is formed as the
result of the signal for controlling the opening degree of the fuel
supply valve 42 output from the fuel supply controller 40 being
decreased and then increased.
[0089] In an embodiment, the drain valve 32 may be configured to
have a purge function of purging fuel in the fuel supply line 20 to
the outside when the drain valve 32 is opened. That is, the drain
valve 32 may discharge condensate water accumulated in the fuel
supply line 20, and simultaneously perform the function of a purge
valve 70 capable of purging fuel including impurities that flow in
the fuel supply line 20 to the outside.
[0090] The drain controller 50 may measure a purge time from the
point in time when the discharge of fuel from the fuel supply line
20 through the drain valve 32 is sensed to the point in time when
the drain valve 32 is closed.
[0091] The drain controller 50 may measure a purge time for which
gas including fuel is discharged from the fuel supply line 20
through the outlet 31 from the point in time when the discharge of
fuel through the drain valve 32 is sensed to the point in time when
the drain valve 32 is closed.
[0092] In another embodiment, the purge valve 70 may be separately
located at the fuel supply line 20 downstream of the fuel cell
stack 10.
[0093] A concentration estimator 60 configured to estimate an
amount purged by opening of the drain valve 32 and to estimate the
concentration of fuel in the fuel supply line 20 through reflection
of the estimated purge amount may be further included.
[0094] The concentration estimator 60 may multiply a discharge rate
over time by purge time (time from the point in time when the
discharge of fuel through the drain valve 32 is sensed to the point
in time when the drain valve 32 is closed) to estimate an amount
purged by opening of the drain valve 32.
[0095] In particular, the concentration estimator 60 may estimate
the concentration of fuel in the fuel supply line 20 in real time
by reflecting the purge amount and crossover amount transmitted to
an air supply line due to diffusion in the initial concentration in
the fuel supply line 20.
[0096] In particular, the concentration of fuel in the fuel supply
line 20 may be estimated on the assumption that only nitrogen,
hydrogen, and vapor are present in the fuel supply line 20 while
having uniform concentration throughout the fuel supply line 20, as
expressed by the following numerical formula.
.times. ? ? = 1 - ? ? - ? ? ##EQU00001## ? .times. indicates text
missing or illegible when filed ##EQU00001.2##
[0097] Here, n.sub. is the total amount of gases in the fuel supply
line 20, n.sub. is the amount of nitrogen, n.sub. is the amount of
vapor, and n.sub. is the amount of hydrogen.
[0098] The concentration of fuel in the fuel supply line 20 may be
estimated by reflecting the amount of nitrogen and the amount of
vapor introduced through crossover, the amount of hydrogen
discharged through crossover, the purge amount, and the discharge
amount in the initial concentration in the fuel supply line 20.
[0099] The total amount of gases n.sub. in the fuel supply line 20
may be estimated from an abnormal gas state equation using pressure
P, volume V, and temperature T in the fuel supply line 20, as
expressed by the following numerical formula.
.times. ? = ? RT .function. [ mol ] ##EQU00002## ? .times.
indicates text missing or illegible when filed ##EQU00002.2##
[0100] Here, R is a gas constant, 8.314 [J/mol K].
[0101] The amount of nitrogen and the amount of vapor may be
estimated by adding (amount of nitrogen introduced through
crossover/amount of vapor-amount of nitrogen by purge/amount of
vapor-amount of nitrogen discharged through outlet 31/amount of
vapor) to the initial amount through integration over time, as
expressed by the following numerical formula.
? .function. [ mol ] ##EQU00003## ? .times. indicates text missing
or illegible when filed ##EQU00003.2##
[0102] The initial amount of nitrogen or vapor may be estimated
based on the pre-mapped map by reflecting the operation stop time
in the case in which the operation of the fuel cell is stopped and
then resumed.
[0103] In particular, the crossover amount of gas may be calculated
by applying Fick's law (law of diffusion) below. The diffusion rate
of gas may be inversely proportional to the thickness of an
electrolyte membrane of the fuel cell stack 10, and may be
proportional to a difference in partial pressure of gas between the
anode and the cathode
m . A = - D .times. .differential. c .differential. x = - D .times.
M RT .times. .differential. P .differential. x ##EQU00004##
[0104] Here, is mass diffusivity of gas (g/s), A is diffusion area,
D is a diffusion coefficient of gas, x is diffusion distance, c is
the concentration of gas, R is a universal gas constant (8.314
J/mol K), P is the pressure of gas, T is the temperature of gas,
and M is a molar mass of gas (g/mol), which may be arranged as
follows.
m . = - D .times. M RT .times. .differential. P .differential. x
.times. A = n . M ##EQU00005## n . = - D .times. 1 RT .times.
.differential. P .differential. x .times. A ##EQU00005.2##
[0105] Here, .sub. is diffusivity of gas (mol/s).
[0106] That is, the crossover amount of gas through the electrolyte
membrane of the fuel cell stack 10 may be calculated by the
following numerical formula.
n N .times. .times. 2 .times. .times. _ .times. .times. xo . = D N
.times. .times. 2 RT .times. P Ca , N .times. .times. 2 - P An , N
.times. .times. 2 .delta. .times. A ##EQU00006##
[0107] Here, .sub. is diffusivity of nitrogen, P is pressure [kPa],
R is a gas constant (8.314 [J/mol K]), T is temperature [K], D is a
diffusion coefficient, A is the area of the electrolyte membrane,
is the thickness of the electrolyte membrane, .sub. is the partial
pressure of nitrogen at the cathode of the fuel cell, and .sub. is
the partial pressure of nitrogen at the anode of the fuel cell.
n V .times. .times. _ .times. .times. xo . = D V RT .times. P Ca ,
V - P An , V .delta. .times. A ##EQU00007##
[0108] Here, .sub. is diffusivity of vapor, P is pressure [kPa], R
is a gas constant (8.314 [J/mol K]), T is temperature [K], D is a
diffusion coefficient, A is the area of the electrolyte membrane,
is the thickness of the electrolyte membrane, .sub. is the partial
pressure of vapor at the cathode of the fuel cell, and .sub. is the
partial pressure of vapor at the anode of the fuel cell.
[0109] Reversely, hydrogen may cross over from the anode to the
cathode of the fuel cell.
n H .times. .times. 2 .times. _ .times. .times. xo . = D H .times.
.times. 2 RT .times. P An , H .times. .times. 2 - P Ca . H .times.
.times. 2 .delta. .times. A ##EQU00008##
[0110] Here, n.sub.H.sub. 2_xo is diffusivity of hydrogen, P is
pressure [kPa], R is a gas constant (8.314 [J/mol K]), T is
temperature [C], D is a diffusion coefficient, A is the area of the
electrolyte membrane, is the thickness of the electrolyte membrane,
P.sub.An,H2 is the partial pressure of vapor at the anode, and
P.sub.Ca,H2 is the partial pressure of vapor at the cathode.
[0111] In addition, diffusivity of gas may be proportional to a
diffusion coefficient of gas, and the diffusion coefficient of gas
may be variable depending on water content and temperature of the
electrolyte membrane located between the anode and the cathode of
the fuel cell.
[0112] In order to improve accuracy, a value that is variable
depending on the state, such as the degree of degradation or
temperature, of the fuel cell may be used as the diffusion
coefficient D of gas although a fixed constant value may be used as
the diffusion coefficient D of gas. In particular, the diffusion
coefficient D of gas may be calculated using a value that is
variable depending on water content and temperature of the
electrolyte membrane located between the anode and the cathode of
the fuel cell. In addition, the diffusion coefficient D of gas may
be calculated as a variable value depending on degradation of the
electrolyte membrane of the fuel cell stack 10.
[0113] The purge amount may be estimated by integrating, over time,
a discharge rate over time or multiplying the discharge rate over
time by purge time.
[0114] The discharge rate over time n.sub. purge may be
proportional to a difference between gas pressure P.sub.An at the
anode and external gas pressure P.sub.out. The external gas
pressure P.sub.out may be gas pressure at the cathode. A concrete
numerical formula may be as follows.
? .times. dt ##EQU00009## ? .times. dt ##EQU00009.2## ? .times.
indicates text missing or illegible when filed ##EQU00009.3##
[0115] Here, C is a purge gain value, which may be set based on the
opening degree of the purge valve 70 at the time of purge.
[0116] As expressed by the following numerical formula, the
discharge rate over time may be proportional to a difference in
pressure between the fuel supply line 20 and the outside, and a
discharge gain may be multiplied as a proportional constant. The
discharge gain may be proportional to the diameter or the area of
the outlet 31 of the water trap 30.
m . A = - D .times. .differential. c .differential. x = - D .times.
M RT .times. .differential. P .differential. x ##EQU00010##
[0117] Here, is a discharge rate over time, Cd is a discharge gain,
is pressure in the fuel supply line 20, and is external
pressure.
[0118] In addition, the purge amount of each gas may be estimated
by multiplying the total purge amount by the concentration of each
gas in the fuel supply line 20.
[0119] Furthermore, control may be performed such that the
concentration in the fuel supply line 20 follows target
concentration using the concentration of fuel in the fuel supply
line 20 estimated by the concentration estimator 60. In particular,
the concentration of fuel in the fuel supply line 20 may be
adjusted by controlling opening of the purge valve 70, controlling
opening of the drain valve 32 having the purge function, or
controlling the fuel supply valve 42.
[0120] Consequently, it is possible to prevent degradation of the
fuel cell stack 10 due to a decrease in concentration of fuel in
the fuel supply line 20, whereby it is possible to improve
durability and to prevent a reduction in fuel efficiency due to
excessive concentration of fuel.
[0121] In an exemplary embodiment of the present disclosure, the
fuel supply controller 40, the drain controller 50, and the
concentration estimator 60 may be realized by a non-volatile memory
(not shown) configured to store an algorithm for controlling the
operation of various elements of a vehicle or data on software
commands for executing the algorithm and a processor (not shown)
configured to perform an operation, which will be described below,
using the data stored in the memory. Here, the memory and the
processor may be realized as individual chips. Alternatively, the
memory and the processor may be realized as a single integrated
chip. The processor may include one or more processors.
[0122] FIG. 3 is a flowchart showing a condensate water drain
control method for fuel cells according to an embodiment of the
present disclosure.
[0123] Referring to FIG. 3, the condensate water drain control
method for fuel cells according to the embodiment of the present
disclosure includes a step of determining whether the fuel supply
valve 42 is controlled such that the pressure in the fuel supply
line 20, configured to recirculate fuel discharged from the fuel
cell stack 10 together with fuel introduced from the fuel supply
valve 42 so as to be supplied to the fuel cell stack 10, is
maintained (S300), a step of opening the drain valve 32, located in
the outlet 31 of the water trap 30 located in the fuel supply line
20, the water trap being configured to collect condensate water
discharged from the fuel cell stack 10, the drain valve being
configured to discharge the condensate water stored in the water
trap 30 to the outside when opened (S400), and a step of sensing
discharge of fuel from the fuel supply line 20 through the drain
valve 32 upon determining in the determination step (S300) that the
pressure is maintained (S500).
[0124] In the step of determining whether the fuel supply valve 42
is controlled such that the pressure in the fuel supply line 20 is
maintained (S300), it may be determined whether the fuel supply
valve 42 is controlled such that the pressure in the fuel supply
line 20 is maintained based on a change in pressure in the fuel
supply line 20 or a change in opening degree of the fuel supply
valve 42 in the state in which the drain valve 32 is closed.
[0125] Before the step of determining whether the fuel supply valve
42 is controlled such that the pressure in the fuel supply line 20
is maintained (S300), a step of determining whether opening of the
drain valve 32 is required (S100) and a step (S200) of fixing the
target pressure in the fuel supply line 20 (S210) or fixing the
required current or the required power of the fuel cell stack 10
(S220) upon determining that opening of the drain valve 32 is
required may be further included.
[0126] After the step of sensing the discharge of fuel (S500), a
step of measuring a purge time from the point in time when the
discharge of fuel from the fuel supply line 20 through the drain
valve 32 is sensed to the point in time when the drain valve 32 is
closed (S600), a step of estimating an amount purged by opening of
the drain valve 32 based on the measured purge time (S700), and a
step of estimating the concentration of fuel in the fuel supply
line 20 through reflection of the estimated purge amount (S800) may
be further included.
[0127] A condensate water drain control system for fuel cells
according to another embodiment of the present disclosure may
include a fuel cell stack 10 configured to generate electric power
through chemical reaction in the fuel cell stack 10, a fuel supply
line 20 configured to recirculate fuel discharged from the fuel
cell stack 10 together with fuel introduced from a fuel supply
valve 42 so as to be supplied to the fuel cell stack 10, a water
trap 30 located in the fuel supply line 20, the water trap being
configured to collect condensate water discharged from the fuel
cell stack 10, a drain valve 32 located in an outlet 31 of the
water trap 30, the drain valve 32 being configured to discharge the
condensate water stored in the water trap 30 to the outside when
opened, a drain controller 50 configured to sense the discharge of
fuel from the fuel supply line 20 through the drain valve 32, and a
fuel supply controller 40 configured to control the fuel supply
valve 42 such that the pressure in the fuel supply line 20 is
maintained when the drain valve 32 is opened under control of the
drain controller 50.
[0128] The drain controller 50 may perform control such that the
drain valve 32 is opened in the case in which discharge of
condensate water stored in the water trap 30 is required. That is,
the drain valve 32 may be opened in the case in which opening of
the drain valve 32 is required.
[0129] In addition, the drain controller 50 may sense the discharge
of fuel from the fuel supply line 20 through the drain valve 32 in
the state in which the drain valve 32 is open. In particular, the
drain controller 50 may sense the discharge of fuel from the fuel
supply line 20 based on a pressure signal sensed by a pressure
sensor 21 or a signal for controlling the opening degree of the
fuel supply valve 42 output from the fuel supply controller 40.
[0130] The fuel supply controller 40 may control the fuel supply
valve 42 such that the pressure in the fuel supply line 20 is
maintained while the drain valve 32 is open or before the drain
valve 32 is opened.
[0131] In particular, the fuel supply controller 40 may control the
fuel supply valve 42 such that the pressure in the fuel supply line
20 is maintained by fixing target pressure in the fuel supply line
20 or required current or required power of the fuel cell stack 10
while the drain valve 32 is open or before the drain valve 32 is
opened.
[0132] As is apparent from the above description, the condensate
water drain control system and method for fuel cells according to
the present disclosure have the effect of minimizing the discharge
of hydrogen from the water trap through the outlet caused due to
inaccuracy and slow responsiveness of the water level sensor.
[0133] In addition, the condensate water drain control system and
method for fuel cells according to the present disclosure have the
effect of accurately estimating the concentration of fuel in the
fuel supply line so as to be used for purge control, etc., thereby
improving accuracy in controlling the concentration of fuel in the
fuel supply line, and preventing unnecessary purge control, thereby
improving fuel economy.
[0134] In addition, the condensate water drain control system and
method for fuel cells according to the present disclosure have the
effect of performing control such that the pressure in the fuel
supply line is variable in order to solve a problem in that the
discharge of fuel through the drain valve is falsely detected,
thereby accurately estimating the concentration of fuel in the fuel
supply line and thus improving durability.
[0135] Although the preferred embodiments of the present disclosure
have been described above with reference to the accompanying
drawings, those skilled in the art will appreciate that the present
disclosure can be implemented in various other embodiments without
changing the technical ideas or features thereof.
* * * * *