阅读说明：本技术 用于燃料电池的冷凝水排水控制系统和方法 (Condensed water drain control system and method for fuel cell ) 是由 李准庸 李东勋 权纯祐 尹圣坤 于 2020-10-23 设计创作，主要内容包括：本发明涉及用于燃料电池的冷凝水排水控制系统和方法,所述用于燃料电池的冷凝水排水控制系统包括：燃料电池堆、燃料供应管线、集水器、排水阀和排水控制器,所述燃料电池堆配置为通过化学反应发电,所述燃料供应管线配置为使从燃料电池堆排放的燃料再循环并与从燃料供应阀引入的燃料一起供应到燃料电池堆,所述集水器位于燃料供应管线中并且配置为收集从燃料电池堆排放的冷凝水,所述排水阀配置为在打开时将集水器中储存的冷凝水排放到外部,所述排水控制器配置为在排水阀打开之前确定燃料供应阀是否被控制成使得燃料供应管线中的压力得以维持,并且在确定压力得以维持时感测燃料从燃料供应管线通过排水阀排放。(The present invention relates to a condensed water drain control system and method for a fuel cell, the condensed water drain control system for a fuel cell including: a fuel cell stack configured to generate electricity through a chemical reaction, a fuel supply line configured to recirculate fuel discharged from the fuel cell stack and supply the fuel to the fuel cell stack together with fuel introduced from a fuel supply valve, a water collector located in the fuel supply line and configured to collect condensed water discharged from the fuel cell stack, a water discharge valve configured to discharge the condensed water stored in the water collector to the outside when opened, a water discharge controller configured to determine whether the fuel supply valve is controlled such that pressure in the fuel supply line is maintained before the water discharge valve is opened, and to sense discharge of the fuel from the fuel supply line through the water discharge valve when the pressure is determined to be maintained.)

1. A condensed water drain control system for a fuel cell, the condensed water drain control system comprising:

a fuel cell stack configured to generate electricity through a chemical reaction in the fuel cell stack;

a fuel supply line configured to recirculate fuel discharged from the fuel cell stack and supply the fuel to the fuel cell stack together with fuel introduced from a fuel supply valve;

a water collector located in the fuel supply line, the water collector configured to collect condensed water discharged from the fuel cell stack;

a drain valve located at an outlet of the sump, the drain valve configured to discharge condensed water stored in the sump to the outside when opened; and

a drain controller configured to determine whether the fuel supply valve is controlled such that the 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 when it is determined that the pressure is maintained.

2. A condensed water drain control system for a fuel cell 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 the pressure in the fuel supply line or a change in the degree of opening of the fuel supply valve in a state where the drain valve is closed.

3. The condensed water drain control system for a fuel cell according to claim 2, further comprising:

a pressure sensor configured to sense a 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 the pressure signal sensed by the pressure sensor.

4. The condensed water drain control system for a fuel cell according to claim 2, further comprising:

a fuel tank configured to store fuel therein; and

a fuel supply controller configured to control an opening degree of the fuel supply valve such that a 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 from the fuel supply controller for controlling the degree of opening of the fuel supply valve.

5. A condensed water drain control system for a fuel cell according to claim 4, wherein the fuel supply controller fixes the target pressure in the fuel supply line in a case where it is required to open the drain valve.

6. The condensed water drain control system for a fuel cell according to claim 1, further comprising: a power controller configured to fix a required current or a required power of the fuel cell stack in a case where it is required to open the water discharge valve.

7. The condensed water drain control system for a fuel cell according to claim 6, further comprising:

a battery configured to assist power generation of the fuel cell stack when 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 a required current or a required power of the fuel cell stack based on the required power of the load or an amount of electricity of the storage battery, and controls charge and discharge of the storage battery to satisfy the required power of the load with the required current or the required power of the fuel cell stack fixed.

8. A condensed water drain control system for a fuel cell according to claim 1, wherein the drain controller senses the discharge of the 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 the degree of opening of the fuel supply valve in a state in which the drain valve is opened.

9. The condensed water drain control system for a fuel cell according to claim 1, wherein:

the drain valve is configured to have a purge function to purge the fuel in the fuel supply line to the outside when opened;

the drain controller measures a purge time from a point of time when the discharge of the fuel from the fuel supply line through the drain valve is sensed to a point of time when the drain valve is closed.

10. The condensed water drain control system for a fuel cell according to claim 1, further comprising: a concentration estimator configured to estimate an amount of purge by opening the water discharge valve, and estimate a concentration of the fuel in the fuel supply line by reflecting the estimated purge amount.

11. A condensed water drain control method for a fuel cell, the condensed water drain control method comprising the steps of:

determining, by the drain controller, whether the fuel supply valve is controlled such that a pressure in a fuel supply line configured to recirculate fuel discharged from the fuel cell stack and supply the fuel to the fuel cell stack together with fuel introduced from the fuel supply valve is maintained;

opening a drain valve through a drain controller, the drain valve being located at an outlet of a sump in a fuel supply line, the sump being configured to collect condensed water discharged from the fuel cell stack, the drain valve being configured to discharge the condensed water stored in the sump to the outside when opened;

the discharge of fuel from the fuel supply line through the drain valve is sensed by the drain controller when it is determined in the determining step that the pressure is maintained.

12. The method of 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: it is determined whether the fuel supply valve is controlled such that the pressure in the fuel supply line is maintained, based on a change in the pressure in the fuel supply line or a change in the degree of opening of the fuel supply valve in a state where the water discharge valve is closed.

13. The method of claim 11, further comprising:

determining whether the drain valve needs to be opened before the step of determining whether the fuel supply valve is controlled such that the pressure in the fuel supply line is maintained;

the target pressure in the fuel supply line or the required current or the required power of the fuel cell stack is fixed when it is determined that the water discharge valve needs to be opened.

14. The method of claim 11, further comprising:

measuring a purge time from a point of time at which the discharge of the fuel from the fuel supply line through the water discharge valve is sensed to a point of time at which the water discharge valve is closed, after the step of sensing the discharge of the fuel;

estimating an amount of purging by opening the drain valve based on the measured purge time;

the fuel concentration in the fuel supply line is estimated by reflecting the estimated purge amount.

15. A condensed water drain control system for a fuel cell, the condensed water drain control system comprising:

a fuel cell stack configured to generate electricity through a chemical reaction in the fuel cell stack;

a fuel supply line configured to recirculate fuel discharged from the fuel cell stack and supply the fuel to the fuel cell stack together with fuel introduced from a fuel supply valve;

a water collector located in the fuel supply line, the water collector configured to collect condensed water discharged from the fuel cell stack;

a drain valve located at an outlet of the sump, the drain valve configured to discharge condensed water stored in the sump to the outside when opened;

a drain controller configured to sense a 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 a pressure in the fuel supply line is maintained when the drain valve is opened under the control of the drain controller.

Technical Field

The present invention relates to a condensed water drain control system and method for a fuel cell, and more particularly, to a condensed water drain control system and method configured to sense discharge of hydrogen from a hydrogen supply line by opening a drain valve.

Background

A fuel cell is a battery that directly converts chemical energy generated by oxidation of fuel into electrical energy, and is therefore a power generation device. A fuel cell is similar to an electrochemical cell in that reduction-oxidation is used, but is different from the electrochemical cell in that reactants are continuously introduced from the outside and reaction products are continuously discharged out of the system, unlike the electrochemical cell configured to perform a cell reaction in a closed system. In recent years, fuel cell power generation systems have been practically used in, for example, fuel cell vehicles, and since the reaction product of fuel cells is pure water, research into using fuel cells as an energy source for environmentally friendly vehicles has been actively conducted.

The fuel cell system includes a fuel cell stack configured to generate electric power through a 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.

When power is generated in the fuel cell stack, water is generated in the fuel cell stack. Due to the concentration difference, some water is discharged to the hydrogen electrode through the electrolyte membrane. The hydrogen gas is recirculated to the hydrogen supply device by the recirculation device, and the water discharged from the hydrogen electrode is condensed and stored in a sump included in the hydrogen supply device.

The sump includes a water level sensor. When the condensed water level sensed by the water level sensor is greater than or equal to a predetermined drain water level, the drain valve is opened to discharge the stored condensed water to the outside. In addition, when the condensed water level 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.

However, in case that the water level sensor of the sump is broken, the level of the condensed water stored in the sump cannot be measured, and thus the drain valve cannot be properly controlled. Specifically, when the condensed water in the hydrogen supply device cannot be smoothly discharged to the outside, the water generated in the fuel cell stack cannot be discharged to the outside, thereby blocking the flow channel in the separator. If the opening of the water discharge valve is more than necessary, hydrogen is unnecessarily discharged, deteriorating fuel economy.

Conventionally, in order to solve this problem, in the case where the water level sensor of the sump is broken, on the basis of a current integration value obtained by integrating the current generated in the fuel cell stack, when the current integration value reaches a predetermined value, fail-safe control is performed to open the water discharge valve. However, since the amount of condensed water stored in the sump is not uniform according to the state of the fuel cell stack, the water level of the sump cannot be accurately measured.

To solve this problem, a method of measuring the pressure in the hydrogen supply line in a state where the water discharge valve is opened is used. However, in the case where the target pressure in the hydrogen supply line is variable in a state where the water discharge valve is opened, the discharge of hydrogen may be erroneously detected although hydrogen is not discharged from the hydrogen supply line.

The information disclosed in this section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms relevant art known to a person skilled in the art.

Disclosure of Invention

The present invention provides a technique of accurately sensing discharge of hydrogen from a hydrogen supply line by opening a drain valve.

In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of a condensed water drain control system for a fuel cell, comprising: a fuel cell stack configured to generate electricity through a chemical reaction in the fuel cell stack, a fuel supply line, a water collector, a water discharge valve, and a water discharge controller; the fuel supply line is configured to recirculate fuel discharged from the fuel cell stack and supply the fuel to the fuel cell stack together with fuel introduced from a fuel supply valve; the water collector is located in the fuel supply line and configured to collect condensed water discharged from the fuel cell stack; the drain valve is located at an outlet of the sump and configured to discharge condensed water stored in the sump to the outside when opened; the drain controller is configured to determine whether the fuel supply valve is controlled such that the pressure in the fuel supply line is maintained before the drain valve opens, and to sense the discharge of fuel from the fuel supply line through the drain valve when it is determined that the pressure is maintained.

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 the pressure in the fuel supply line or a change in the degree of opening of the fuel supply valve in a state where the drain valve is closed.

The condensed water drain control system may further include a pressure sensor configured to sense a 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 the pressure signal sensed by the pressure sensor.

The condensed water drain control system may further include a fuel tank configured to store fuel in the fuel tank, and a fuel supply controller; the fuel supply controller is configured to control the degree of opening 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 from the fuel supply controller for controlling the degree of opening of the fuel supply valve.

In the case where it is necessary to open the drain valve, the fuel supply controller may fix the target pressure in the fuel supply line.

The condensed water drain control system may further include a power controller configured to fix a required current or a required power of the fuel cell stack in a case where it is required to open the drain valve.

The condensed water drain control system may further include: a battery configured to assist power generation of the fuel cell stack when being charged or discharged by electric power generated by the fuel cell stack, and a load; the load is 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 a required current or a required power of the fuel cell stack based on the required power of the load or an amount of electricity of the storage battery, and may control charging and discharging of the storage battery to satisfy the required power of the load with the required current or the required power of the fuel cell stack fixed.

The drain controller may sense discharge of the 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 the degree of opening of the fuel supply valve in a state in which the drain valve is opened.

The water discharge valve may be configured to have a purge function to purge the fuel in the fuel supply line to the outside when opened; the drain controller may measure a purge time from a point of time when the discharge of the fuel from the fuel supply line through the drain valve is sensed to a point of time when the drain valve is closed.

The condensed water drain control system may further include a concentration estimator configured to estimate an amount of purging by opening the drain valve, and estimate a concentration of the fuel in the fuel supply line by reflecting the estimated purge amount.

According to another aspect of the present invention, there is provided a condensed water drain control system for a fuel cell, including: a fuel cell stack configured to generate electricity through a chemical reaction in the fuel cell stack, a fuel supply line, a water collector, a water discharge valve, a water discharge controller, and a fuel supply controller; the fuel supply line is configured to recirculate fuel discharged from the fuel cell stack and supply the fuel to the fuel cell stack together with fuel introduced from a fuel supply valve; the water collector is located in the fuel supply line and configured to collect condensed water discharged from the fuel cell stack; the drain valve is located at an outlet of the sump and configured to discharge condensed water stored in the sump to the outside when opened; the drain controller is configured to sense a discharge of fuel from the fuel supply line through the drain valve; the fuel supply controller is configured to control the fuel supply valve such that the pressure in the fuel supply line is maintained when the drain valve is opened under the control of the drain controller.

According to another aspect of the present invention, there is provided a condensed water drain control method for a fuel cell, the condensed water drain control method including the steps of: determining, by the drain controller, whether the fuel supply valve is controlled such that a pressure in a fuel supply line configured to recirculate fuel discharged from the fuel cell stack and supply the fuel to the fuel cell stack together with fuel introduced from the fuel supply valve is maintained; opening a drain valve through a drain controller, the drain valve being located at an outlet of a sump in a fuel supply line, the sump being configured to collect condensed water discharged from the fuel cell stack, the drain valve being configured to discharge the condensed water stored in the sump to the outside when opened; the discharge of fuel from the fuel supply line through the drain valve is sensed by the drain controller when it is determined in the determining step that the pressure is maintained.

The step of determining whether the fuel supply valve is controlled such that the pressure in the fuel supply line is maintained may comprise: it is determined whether the fuel supply valve is controlled such that the pressure in the fuel supply line is maintained, based on a change in the pressure in the fuel supply line or a change in the degree of opening of the fuel supply valve in a state where the water discharge valve is closed.

The condensed water drain control method may further include: determining whether the drain valve needs to be opened before the step of determining whether the fuel supply valve is controlled such that the pressure in the fuel supply line is maintained; the target pressure in the fuel supply line or the required current or the required power of the fuel cell stack is fixed when it is determined that the water discharge valve needs to be opened.

The condensed water drain control method may further include: measuring a purge time from a point of time at which the discharge of the fuel from the fuel supply line through the water discharge valve is sensed to a point of time at which the water discharge valve is closed, after the step of sensing the discharge of the fuel; estimating an amount of purging by opening the drain valve based on the measured purge time; the fuel concentration in the fuel supply line is estimated by reflecting the estimated purge amount.

Drawings

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

fig. 1 is a schematic diagram showing the structure of a condensed water drain control system for a fuel cell according to an embodiment of the present invention;

fig. 2 is a schematic diagram showing a conventional condensed water drain control signal and a fuel supply control signal; and

fig. 3 is a flowchart illustrating a condensed water drain control method for a fuel cell according to an embodiment of the present invention.

Detailed Description

It should be understood that the term "vehicle" or "vehicular" or other similar terms as used herein generally includes motor vehicles, such as passenger automobiles including Sport Utility Vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft including a variety of boats, 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 non-petroleum sources). As referred to herein, a hybrid vehicle is a vehicle having two or more power sources, such as both a gasoline-powered vehicle and an electric-powered vehicle.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. 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, values, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, values, 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 this 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," "device," "means," and "module" described in the specification denote a unit for performing at least one of functions and operations, and may be implemented by hardware components or software components, and a combination thereof.

Furthermore, the control logic of the present invention may be embodied as a non-transitory computer readable medium on a computer readable medium, including 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) -ROM, magnetic tape, floppy disk, flash drive, smart card, and optical data storage device. The computer readable medium CAN also be distributed over a network coupled computer system so that the computer readable medium is stored and executed in a distributed fashion, such as through a telematics server or Controller Area Network (CAN).

The specific structural and functional descriptions of the embodiments of the present invention disclosed in the specification or the present invention are merely illustrative of the embodiments of the present invention. Embodiments of the invention may be embodied in various forms and should not be construed as limited to the embodiments of the invention disclosed in this specification or the present invention.

Since embodiments of the present invention can be variously modified and can have various forms, specific embodiments will be shown in the drawings and will be described in detail in the present specification or the present invention. However, the embodiments according to the concept of the present invention are not limited to these specific embodiments, and it should be understood that the present invention includes all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention.

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, the corresponding elements should not be construed as limited by these terms, which are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present invention.

It will be understood that when an assembly is referred to as being "connected to" or "coupled to" another assembly, it can be directly connected or coupled to the other assembly or intervening assemblies may be present. In contrast, when an element is referred to as being "directly connected to" or "directly coupled to" another element, there are no intervening elements present. Other terms describing the relationship between components, such as "between … …" and "directly between … …" or "directly adjacent to … …" and "directly adjacent to … …", must be interpreted in the same way.

Reference will now be made in detail to the preferred embodiments of the present invention, 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.

Fig. 1 is a schematic diagram showing the structure of a condensed water drain control system for a fuel cell according to an embodiment of the present invention.

Referring to fig. 1, a condensed water drain control system for a fuel cell according to an embodiment of the present invention includes: the fuel cell stack 10, the fuel supply line 20, the water collector 30, the drain valve 32 and the drain controller 50, the fuel cell stack 10 is configured to generate power through a chemical reaction in the fuel cell stack 10, the fuel supply line 20 is configured to recirculate the fuel discharged from the fuel cell stack 10 and supply the fuel to the fuel cell stack 10 together with the fuel introduced from the fuel supply valve 42, the water collector 30 is located in the fuel supply line 20 and is configured to collect condensed water discharged from the fuel cell stack 10, the drain valve 32 is located at the outlet 31 of the sump 30 and is configured to discharge condensed water stored in the sump 30 to the outside when opened, the drain controller 50 is 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 opens, and senses the discharge of fuel from the fuel supply line 20 through the water discharge valve 32 when it is determined that the pressure of the fuel supply line 20 is maintained.

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 electricity through a chemical reaction. In the fuel cell stack 10, hydrogen and oxygen react with each other, thereby generating condensed water.

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 by recirculation. That is, the fuel discharged from the fuel cell stack 10 is supplied to the fuel cell stack 10 by recirculation in a state of being mixed with the fuel supplied from the fuel tank 41.

A water collector 30 is provided in the fuel supply line 20 to store condensed water generated in the fuel cell stack 10. Specifically, the condensed water, which is generated by the oxygen electrode of the fuel cell stack 10 and moves to the fuel supply line 20 due to diffusion to the hydrogen electrode, is collected and stored in the sump 30. The outlet 31 of the water collector 30 may be connected to the outside or may be connected to a humidifier located at an oxygen electrode inlet of the fuel cell stack 10 so as to supply moisture.

A drain valve 32 may be provided in the outlet 31 of the sump 30 to control the discharge of the condensed water from the sump 30. Specifically, the drain valve 32 may allow the drainage of the condensed water stored in the sump 30 when opened, and may prevent the drainage of the condensed water when closed.

Generally, the drain valve 32 is controlled to be closed such that hydrogen cannot be discharged through the outlet 31 of the sump 30, and opened to discharge condensed water to the outside when the condensed water is intermittently stored.

The drain controller 50 may control the opening and closing of the drain valve 32. Specifically, the drain controller 50 may sense or predict the level of the condensed water stored in the sump 30, may control such that the drain valve 32 is opened in a state where the level of the condensed water is high, and may control such that the drain valve 32 is closed when the level of the condensed water is lowered due to the opening of the drain valve 32.

Fig. 2 is a schematic diagram illustrating a conventional condensed water drain control signal and a fuel supply control signal.

Further referring to fig. 2, conventionally, the sump 30 includes a water level sensor 33, the water level sensor 33 being configured to sense an amount of condensed water stored in the sump 30, and to control opening and closing of the drain valve 32 using the water level sensor 33.

Specifically, the drain valve 32 is controlled to be opened when the storage amount of the condensed water sensed by the water level sensor 33 is greater than or equal to a predetermined high water level threshold value, and the drain valve 32 is controlled to be closed when the storage amount of the condensed water is less than or equal to a predetermined low water level threshold value.

However, the water level sensor 33 frequently malfunctions, so that sensing accuracy is degraded and response is slow. Therefore, as in the abnormal discharge state of fig. 2, even if the discharge of the condensed water is completed, the water discharge valve 32 is kept open, so that the hydrogen is discharged through the outlet 31.

Conventionally, in order to solve this problem, control is performed such that, when the water level sensor 33 malfunctions, the water discharge valve 32 is opened as long as the integrated value of the output current of the fuel cell reaches a predetermined integrated current value, and the water discharge valve 32 is kept open for a predetermined opening time and then closed. However, the opening and closing of the drain valve 32 is controlled regardless of the amount of condensed water stored in the sump 30, which results in the discharge of hydrogen or flooding of the fuel cell stack 10.

In order to estimate the amount of condensed water stored in the sump 30 and to perform control based on the amount of condensed water even when the water level sensor 33 malfunctions, the drain controller 50 senses whether fuel is discharged from the fuel supply line 20 through the outlet 31 in a state in which the drain valve 32 is opened, and controls such that the drain valve 32 is closed when the fuel discharge is sensed.

Specifically, the fuel supply valve 42 controls the pressure in the fuel supply line 20 to follow the target pressure (PI control), and the drain controller 50 senses the discharge of the fuel through the outlet 31 based on the signal for controlling the opening degree of the fuel supply valve 42 in a state where the drain valve 32 is opened.

However, in the case of following such control, as shown in fig. 2, in a state where the water discharge valve 32 is opened, when the target pressure in the fuel supply line 20 is changed, the pressure in the fuel supply line 20 and the control signal of the fuel supply valve 42 are also variable, so that the fuel discharge (erroneous detection of the discharge state of hydrogen) is erroneously judged even in a case where no fuel is discharged through the water discharge valve 32.

According to the present invention, 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 when it is determined that the fuel supply valve is controlled such that the pressure in the fuel supply line is maintained, the drain controller 50 may sense that fuel is discharged from the fuel supply line 20 through the drain valve 32 in a state in which the drain valve 32 is opened.

Therefore, the drain controller 50 can accurately sense the discharge of the fuel through the drain valve 32 in a state where the drain valve 32 is opened, and thus can avoid erroneous judgment of the fuel discharge due to a pressure change in the fuel supply line 20 caused by other environmental changes.

Here, the fuel supply valve 42 being 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 unless the pressure in the fuel supply line 20 changes due to the discharge of fuel from the fuel supply line 20 through the water discharge valve 32. That is, in the state where the drain valve 32 is opened, the pressure variation in the fuel supply line 20 due to other factors is minimized.

Specifically, 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 the pressure in the fuel supply line 20 or a change in the degree of opening of the fuel supply valve 42 in a state where the drain valve 32 is closed.

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.

Specifically, a pressure sensor 21 may be located at an inlet side of the fuel cell stack 10 in the fuel supply line 20, and may sense the pressure in the fuel supply line 20, and a fuel supply controller 40 (which will be described later) 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.

Specifically, the drain controller 50 may differentiate the pressure signal sensed by the pressure sensor 21 or calculate a change value (absolute value) from a previous sensed value, and in the case where the calculated differential value or change value is maintained within a predetermined range for a time greater than or equal to a predetermined holding time, the drain controller 50 may determine that the fuel supply valve 42 is controlled such that the pressure in the fuel supply line 20 is maintained.

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 a 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 from the fuel supply controller 40 for controlling the opening degree of the fuel supply valve 42.

The fuel tank 41 may store high-pressure hydrogen in the fuel tank 41, and the stored hydrogen may be supplied to the fuel supply line 20 through the fuel supply valve 42. Specifically, the high-pressure hydrogen stored in the fuel tank 41 may be supplied to the fuel supply line 20 after being depressurized.

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 may output a signal for controlling the degree of opening of the fuel supply valve 42 from the fuel supply controller 40.

Specifically, the fuel supply controller 40 may control the 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 degree of opening 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.

The drain controller 50 may differentiate a signal for controlling the degree of opening of the fuel supply valve 42 from the fuel supply controller 40 or calculate a change value (absolute value) from a previous control value, and in the case where the calculated differential value or change value is held within a predetermined range for a time greater than or equal to a predetermined holding time, the drain controller 50 may determine that the fuel supply valve 42 is controlled such that the pressure in the fuel supply line 20 is maintained.

Referring to fig. 2, the variation value of the pressure signal of the fuel supply line 20 is relatively small, so that it is difficult to sense the discharge of the fuel through the discharge valve 32; however, the variation value of the control signal of the fuel supply valve 42 is relatively large, so that the emission of the fuel can be sensed quickly, accurately, and easily.

In an embodiment, the fuel supply controller 40 may fix the target pressure in the fuel supply line 20 in the event that the drain valve 32 needs to be opened.

The fuel supply controller 40 may set the target pressure in the fuel supply line 20 based on the required current or the required power of the fuel cell. Specifically, in the case where it is necessary to open the water discharge valve 32, the fuel supply controller 40 may fix the target pressure in the fuel supply line 20 even if the required current or the required power of the fuel cell is variable.

In another embodiment, a power controller configured to fix a required current or a required power of the fuel cell in the case where it is required to open the water discharge valve 32 may be further included.

The power controller may control the required current or the required power of the fuel cell based on the required current or the required power of the load and an amount of electricity of the storage battery 80 (to be described later). That is, the power controller may set the required current or required power of the fuel cell to meet the required current of the load that varies in real time. However, the power controller may perform control so that the required current or the required power of the fuel cell is fixed in the case where it is necessary to open the water discharge valve 32.

It may further include a battery 80 configured to assist the power generation of the fuel cell stack 10 when being charged or discharged by the 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 the electric power from the fuel cell stack 10 or the battery 80.

That is, the fuel cell stack 10 and the load may be connected to each other via the main bus terminals, and the battery 80 may be connected in parallel to the main bus terminals. Specifically, the high voltage converter 81 may be located between the main bus terminal and the storage battery 80, and the power controller may control the high voltage converter 81 to control charging and discharging of the storage battery 80.

The power controller may control the required current or the required power of the fuel cell based on the required power of the load or the capacity of the battery 80, and in the case where the required current or the required power of the fuel cell is fixed, the power controller may control the charging and discharging of the battery 80 to meet the required power of the load.

That is, in the case where the required current or the required power of the fuel cell is fixed, when the required power of the load is variable, the power controller may satisfy the required power of the load by charging and discharging the battery 80.

Specifically, the required power Pt of the load may be the sum of the required power Ps of the fuel cell stack 10 and the auxiliary power Pb of the battery 80.

Pt＝Ps+Pb->Pb＝Pt-Ps

Assuming that the voltage at the main bus terminal between the fuel cell stack 10 and the load is V, the discharge current Ib of the battery 80 is as follows.

Ib＝Pt/V-Is

Here, in the case where the 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 meet the required power Pt of the load.

Specifically, in the case where Ib >0 (which is a state in which the battery 80 is discharged), the power controller may control the voltage of the high-voltage converter 81 to Vref ═ V + α so that the battery 80 is discharged.

On the other hand, in the case where Ib <0 (which is the state of charge of the battery 80), the power controller may control the voltage of the high-voltage converter 81 to Vref-V- α so that the battery 80 is charged.

The drain controller 50 may control the opening of the drain valve 32 based on the storage amount of the condensed water sensed by the water level sensor 33. For example, the drain controller may determine that the drain valve 32 needs to be opened when the storage amount of the condensed water sensed by the water level sensor 33 is greater than or equal to a predetermined high water level threshold value.

In addition, when the storage amount of the condensed water sensed by the water level sensor 33 is less than or equal to a predetermined low water level threshold value, or when it is sensed that the fuel is discharged through the outlet 31 in a state in which the drain valve 32 is opened, the drain controller 50 may control such that the drain valve 32 is closed.

Specifically, 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 the pressure in the fuel supply line 20 or a change in the degree of opening of the fuel supply valve 42 in a state where the drain valve 32 is open.

The drain controller 50 may sense discharge of the 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.

In an embodiment, the drain controller 50 may sense that fuel has been discharged in the case where the rate of change of the signal for controlling the degree of opening of the fuel supply valve 42, which is output from the fuel supply controller 40, is greater than or equal to a predetermined rate of change.

In the case where the rate of change over time of the signal for controlling the degree of opening of the fuel supply valve 42, which is output from the fuel supply controller 40, abruptly changes to be greater than or equal to a predetermined rate of change, it can be determined that the pressure in the fuel supply line 20 abruptly changes, and therefore it can be determined that fuel has been discharged through the outlet 31.

In another embodiment, in the case where the difference between the signal for controlling the opening degree of the fuel supply valve 42 output from the fuel supply controller 40 and the output signal reference value based on the pre-mapped output signal map is greater than or equal to a predetermined error, it may be sensed that fuel has been discharged.

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 where 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, which is output from the fuel supply controller 40, is greater than or equal to a predetermined error, it may be determined that the pressure in the fuel supply line 20 has suddenly changed, and thus it may be determined that fuel has been discharged through the outlet 31.

In another embodiment, it may be sensed that the fuel has been discharged at an inflection point of a peak formed as a result of a decrease and then an increase in the signal for controlling the opening degree of the fuel supply valve 42, which is output from the fuel supply controller 40.

In an embodiment, the water discharge valve 32 may be configured to have a purge function of purging the fuel in the fuel supply line 20 to the outside when the water discharge valve 32 is opened. That is, the drain valve 32 may drain the condensed water accumulated in the fuel supply line 20 and, at the same time, perform the function of the purge valve 70, which purge valve 70 is capable of purging the fuel including the impurities flowing in the fuel supply line 20 to the outside.

The drain controller 50 may measure a purge time from a point of time when the discharge of the fuel from the fuel supply line 20 through the drain valve 32 is sensed to a point of time when the drain valve 32 is closed.

The drain controller 50 may measure a purge time, during which the gas including the fuel is discharged from the fuel supply line 20 through the outlet 31, from a time point at which the discharge of the fuel through the drain valve 32 is sensed to a time point at which the drain valve 32 is closed.

In another embodiment, the purge valve 70 may be located separately at the fuel supply line 20 downstream of the fuel cell stack 10.

A concentration estimator 60 may be further included, the concentration estimator 60 being configured to estimate the amount of purging by opening the water discharge valve 32 and estimate the concentration of the fuel in the fuel supply line 20 by reflecting the estimated purge amount.

The concentration estimator 60 may multiply the discharge rate varying with time by a purge time (time from a time point at which the discharge of the fuel through the water discharge valve 32 is sensed to a time point at which the water discharge valve 32 is closed) to estimate the amount of purging by opening the water discharge valve 32.

Specifically, the concentration estimator 60 may estimate the fuel concentration in the fuel supply line 20 in real time by reflecting the purge amount and the crossover amount transmitted to the air supply line due to diffusion of the initial concentration in the fuel supply line 20.

Specifically, the fuel concentration in the fuel supply line 20 may be estimated based on the following assumption: only nitrogen, hydrogen and vapor are present in the fuel supply line 20 while having a uniform concentration throughout the fuel supply line 20, as shown by the numerical formula below.

Here, n is_AnIs the total amount of gas in the fuel supply line 20,is the amount of nitrogen, n_VIs the amount of the vapor that is present,is hydrogenAmount of the compound (A).

The fuel concentration in the fuel supply line 20 can be estimated by reflecting the amount of nitrogen and the amount of vapor introduced by crossover, the amount of hydrogen discharged by crossover, the purge amount, and the discharge amount in the initial concentration in the fuel supply line 20.

The total amount of gas n in the fuel supply line 20 can be estimated by using an abnormal gas state equation of pressure P, volume V and temperature T in the fuel supply line 20_AnAs shown by the following numerical formula.

Here, R is the gas constant 8.314[ J/mol K ].

The amount of nitrogen and the amount of vapor may be estimated by adding the initial amount to the integral of time (by the amount of nitrogen/vapor introduced crosswise-the amount of nitrogen purged/the amount of vapor-the amount of nitrogen discharged through the outlet 31) as shown in the following numerical formulas.

In the case where the fuel cell is stopped and then resumed, the initial amount of nitrogen or vapor may be estimated based on the pre-map by reflecting the stop time.

Specifically, the crossing amount of the gas can be calculated by applying the following fick's law (diffusion law). The diffusivity of the gas may be inversely proportional to the thickness of the electrolyte membrane of the fuel cell stack 10 and may be proportional to the difference in partial pressure of the gas between the anode and the cathode.

In this case, the amount of the solvent to be used,is the mass diffusivity of the gas (g/s), A is the diffusion area, D is the diffusion coefficient of the gas, x is the diffusion distance, c is the concentration of the gas, R is the universal gas constant (8.314J/mol K), P is the pressure of the gas, T is the temperature of the gas, and M is the molar mass of the gas (g/mol), and can be set as follows.

In this case, the amount of the solvent to be used,is the diffusivity (mol/s) of the gas.

That is, the crossing amount of the gas passing through the electrolyte membrane of the fuel cell stack 10 can be calculated by the following numerical formula.

In this case, the amount of the solvent to be used,is the diffusivity of nitrogen, P is the pressure (kPa), R is the gas constant (8.314(J/mol K)), T is the temperature (K), D is the diffusion coefficient, A is the area of the electrolyte membrane, δ is the thickness of the electrolyte membrane, P is the diffusion coefficient_Ca,N2Is the partial pressure of nitrogen, P, at the cathode of the fuel cell_An,N2Is the partial pressure of nitrogen at the anode of the fuel cell.

In this case, the amount of the solvent to be used,is the diffusivity of the vapor, P is the pressure (kPa), R is the gas constant (8.314(J/mol K)), T is the temperature (K), D is the diffusion coefficient, A is the area of the electrolyte membrane, δ is the thickness of the electrolyte membrane, P is the diffusion coefficient of the electrolyte membrane_Ca,VIs the partial pressure of the vapor at the cathode of the fuel cell, P_An,VIs the partial pressure of the vapor at the anode of the fuel cell.

Instead, hydrogen may cross from the anode to the cathode of the fuel cell.

In this case, the amount of the solvent to be used,is the diffusivity of hydrogen, P is the pressure (kPa), R is the gas constant (8.314(J/mol K)), T is the temperature (K), D is the diffusion coefficient, A is the area of the electrolyte membrane, δ is the thickness of the electrolyte membrane, P is the diffusion coefficient_An，H2Is the partial pressure of hydrogen at the anode, P_Ca，H2Is the partial pressure of hydrogen at the cathode.

In addition, the diffusivity of the gas may be proportional to the diffusion coefficient of the gas, and the diffusion coefficient of the gas may vary according to the water content and temperature of an electrolyte membrane located between an anode and a cathode of the fuel cell.

For the purpose of improving the accuracy, although a fixed constant value may be used as the diffusion coefficient D of the gas, a value that varies depending on the state of the fuel cell (e.g., the degree of degradation or the temperature) may also be used as the diffusion coefficient D of the gas. Specifically, the diffusion coefficient D of the gas may be calculated using a value that varies according to the water content and the temperature of an electrolyte membrane located between an anode and a cathode of the fuel cell. In addition, the diffusion coefficient D of the gas may be calculated using a variable value that depends on the degradation of the electrolyte membrane of the fuel cell stack 10.

The purge amount may be estimated by integrating the time-varying discharge rate over time or multiplying the time-varying discharge rate by the purge time.

Time-varying discharge rateCan be related to the gas pressure P at the anode_AnAnd an external gas pressure P_outThe difference between them is proportional. Outside gas pressure P_outMay be the gas pressure at the cathode. Specific numerical formulas may be as follows.

Here, C is a purge gain value, which may be set based on the degree of opening of the purge valve 70 at the time of purge.

As shown in the following numerical formula, the time-varying discharge rate may be proportional to the pressure difference between the fuel supply line 20 and the outside, and may be multiplied by a discharge gain that is a proportionality constant. The discharge gain may be proportional to the diameter or area of the outlet 31 of the sump 30.

In this case, the amount of the solvent to be used,is the discharge rate over time, Cd is the discharge gain, P_AnIs the pressure in the fuel supply line 20, P_{Stk_Out}Is the external pressure.

In addition, the purge amount of each gas can be estimated by multiplying the total purge amount by the concentration of each gas in the fuel supply line 20.

Further, using the fuel concentration in the fuel supply line 20 estimated by the concentration estimator 60, control may be performed such that the concentration in the fuel supply line 20 follows the target concentration. Specifically, the fuel concentration in the fuel supply line 20 may be adjusted by controlling the opening of the purge valve 70, controlling the opening of the drain valve 32 having a purge function, or controlling the fuel supply valve 42.

Therefore, the fuel cell stack 10 can be prevented from being degraded due to the decrease in the fuel concentration in the fuel supply line 20, so that the durability can be improved, and the fuel efficiency can be prevented from being decreased due to the excessively high fuel concentration.

In an exemplary embodiment of the present invention, the fuel-supply controller 40, the drain controller 50, and the concentration estimator 60 may be implemented by a non-volatile memory (not shown) configured to store an algorithm for controlling operations of various elements of the vehicle or data of software commands for executing the algorithm, and a processor (not shown) configured to perform the operations described below using the data stored in the memory. Here, the memory and the processor may be implemented in the form of separate chips. Alternatively, the memory and processor may be implemented as a single integrated chip. The processor may include one or more processors.

Fig. 3 is a flowchart illustrating a condensed water drain control method for a fuel cell according to an embodiment of the present invention.

Referring to fig. 3, a condensed water drain control method for a fuel cell according to an embodiment of the present invention includes: a step (S300) of determining whether the fuel supply valve 42 is controlled such that the pressure in the fuel supply line 20 is maintained, the fuel supply line 20 being configured to recirculate the fuel discharged from the fuel cell stack 10 and to supply to the fuel cell stack 10 together with the fuel introduced from the fuel supply valve 42; a step (S400) of opening a water discharge valve 32, the water discharge valve 32 being located at an outlet 31 of the sump 30 in the fuel supply line 20, the sump being configured to collect the condensed water discharged from the fuel cell stack 10, the water discharge valve being configured to discharge the condensed water stored in the sump 30 to the outside when opened; and a step (S500) of sensing discharge of the fuel from the fuel supply line 20 through the water discharge valve 32 when it is determined in the determining step (S300) that the pressure is maintained.

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 the pressure in the fuel supply line 20 or a change in the opening degree of the fuel supply valve 42 in a state where the water discharge valve 32 is closed.

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), it may further include: a step of determining whether it is necessary to open the water discharge valve 32 (S100), and a step (S200) including a step of fixing a target pressure in the fuel supply line 20 when it is determined that it is necessary to open the water discharge valve 32 (S210) or a step of fixing a required current or required power of the fuel cell stack 10 (S220).

After the step of sensing fuel emissions (S500), may further include: a step (S600) of measuring a purge time from a time point at which the discharge of the fuel from the fuel supply line 20 through the water discharge valve 32 is sensed to a time point at which the water discharge valve 32 is closed; a step (S700) of estimating an amount of purging by opening the drain valve 32 based on the measured purging time; and a step (S800) of estimating the fuel concentration in the fuel supply line 20 by reflecting the estimated purge amount.

A condensed water drain control system for a fuel cell according to another embodiment of the present invention may include: a fuel cell stack 10 configured to generate electricity through a chemical reaction in the fuel cell stack 10, a fuel supply line 20 configured to recirculate fuel discharged from the fuel cell stack 10 and supply the fuel to the fuel cell stack 10 together with fuel introduced from a fuel supply valve 42, a water collector 30 located in the fuel supply line 20 and configured to collect condensed water discharged from the fuel cell stack 10, a water discharge valve 32 located at an outlet 31 of the water collector 30 and configured to discharge the condensed water stored in the water collector 30 to the outside when opened, a drain controller 50 configured to sense discharge of the fuel from the fuel supply line 20 through the water discharge valve 32, a drain controller 40 configured to control the fuel supply valve 42 such that pressure in the fuel supply line 20 is obtained when the water discharge valve 32 is opened under the control of the drain controller 50, 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 obtained when the water discharge valve 32 is opened under the control of the drain controller 50 To maintain.

The drain controller 50 may control such that the drain valve 32 is opened in case it is required to drain the condensed water stored in the sump 30. That is, the drain valve 32 may be opened in the case where it is necessary to open the drain valve 32.

In addition, the drain controller 50 may sense the discharge of the fuel from the fuel supply line 20 through the drain valve 32 in a state where the drain valve 32 is opened. Specifically, the drain controller 50 may sense that fuel is discharged from the fuel supply line 20 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.

The fuel supply controller 40 may control the fuel supply valve 42 so that the pressure in the fuel supply line 20 is maintained while the water discharge valve 32 is opened or before the water discharge valve 32 is opened.

Specifically, 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 the target pressure in the fuel supply line 20 or the required current or the required power of the fuel cell stack 10 when the water discharge valve 32 is opened or before the water discharge valve 32 is opened.

As apparent from the above description, the condensed water drain control system and method for a fuel cell according to the present invention have the effects of: the discharge of hydrogen from the sump through the outlet due to the inaccuracy and slow response of the water level sensor is minimized.

In addition, the condensed water drain control system and method for a fuel cell according to the present invention have the effects of: the fuel concentration in the fuel supply line can be accurately estimated for purge control or the like, thereby improving the accuracy of controlling the fuel concentration in the fuel supply line, and avoiding unnecessary purge control, thereby improving fuel economy.

In addition, the condensed water drain control system and method for a fuel cell according to the present invention have the effects of: it is possible to control so that the pressure in the fuel supply line is variable, thereby solving the problem of erroneously detecting the discharge of the fuel through the water discharge valve, thereby accurately estimating the fuel concentration in the fuel supply line, and thus improving the durability.

Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art will appreciate that the present invention can be implemented in various other embodiments without changing the technical ideas or features thereof.