Abstract:
A fuel cell system with an ejector is provided. In particular, the system includes a stack, fuel injection nozzle and a water injection nozzle. In particular, the stack produces electricity via an electrochemical reaction using fuel and air. The fuel injection nozzle injects fuel into the stack and the water injection nozzle injects water into the fuel injection nozzle. In particular, water is supplied from the water injection nozzle into the fuel injection nozzle due to a vacuum within the fuel injection nozzle.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2013-0111104 filed in the Korean Intellectual Property Office on Sep. 16, 2013, the entire contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    (a) Field of the Invention 
         [0003]    The present invention relates to a fuel cell system having an ejector that stably supplies fuel and moisture to a fuel cell stack that produces electric energy by using the fuel and air to stably produce electricity. 
         [0004]    (b) Description of the Related Art 
         [0005]    Fuel cell vehicles operating via a fuel cell system often supply hydrogen (as fuel) to a fuel cell stack to produce electricity via an electrochemical reaction. This electricity is then used to power an electric motor to drive the vehicle. As such, a fuel cell system is a kind of power generation system that electrochemically converts chemical energy of fuel directly into electric energy in the fuel cell stack without converting the chemical energy of the fuel into heat by combustion. 
         [0006]    In the fuel cell system, high-purity hydrogen is typically supplied from a hydrogen storage tank to a fuel electrode (anode) of the fuel cell during operation and air from the atmosphere is supplied directly to an air electrode (cathode) of the fuel cell via an air supply device such as an air blower. 
         [0007]    The hydrogen supplied to the fuel cell stack is generally separated into a hydrogen ion and an electron as a catalyst of the fuel electrode (anode) and the separated hydrogen ion moves toward the air electrode (cathode) through a polymer electrolyte membrane. Oxygen supplied to the air electrode is combined with the electron that enters the air electrode through an external conducting wire to generate electric energy while generating water. 
         [0008]    In order to properly operate a fuel cell, moisture needs to be appropriately maintained in a membrane electrode assembly (MEA) of the fuel cell stack, and a humidifier should be installed on each fuel circulation line and air circulation line that circulates the stack to operate the stack effectively. 
         [0009]    However, this humidifying device/system is conventionally disposed outside the stack and thus requires additional space within the vehicle and often involves a complicated pipe connection. 
         [0010]    The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention has been made in an effort to provide a fuel cell system which utilizes an ejector that can reduce the capacity of an external humidifier or omit a humidifier from the system by continuously reusing moisture generated in an air electrode or a fuel electrode. 
         [0012]    An exemplary embodiment of the present invention provides a fuel cell system with an ejector. In particular, a stack is provided which produces electricity via an electro-chemical reaction between fuel and air and a fuel injection nozzle is disposed within the system to inject fuel into the stack. A water injection nozzle is also disposed within the system to inject water into the fuel injection nozzle. This water may be supplied to the water injection nozzle via pressure from the fuel injected via the fuel injection nozzle. 
         [0013]    More specifically, a fuel injection aperture disposed to receive and inject the fuel may be formed in the fuel injection nozzle. Likewise, a water injection aperture of the water injection nozzle may be disposed at a center of the fuel injection aperture. 
         [0014]    Furthermore, a water supply line may be connected with the water injection nozzle in order to supply water contained in a lower portion of a condensed water reservoir to the water injection nozzle. The fuel injection nozzle may be disposed in an intake chamber of the ejector where gas circulated in the stack and the fuel are mixed with each other. A notch may be formed at the fuel injection aperture of the fuel injection nozzle. 
         [0015]    The fuel injection nozzle may be disposed in the condensed water reservoir in which condensed water is contained, and a main fuel injection nozzle that injects fuel separately from the fuel injection nozzle may be disposed in the intake chamber of the ejector. 
         [0016]    The fuel injection nozzle may be disposed in a manifold adjacent to the stack, and a main fuel injection nozzle that injects fuel separately from the fuel injection nozzle may be disposed in the intake chamber of the ejector. 
         [0017]    The system may further include a water supply line which is connected with the water injection nozzle to supply water to the water injection nozzle The water supply line may be connected with each of a first condensed water reservoir gathers moisture from the fuel circulated in the stack and a second condensed water reservoir which gathers moisture inform the air circulated in the stack. 
         [0018]    A level sensor may be disposed to sense a level of the water contained in the second condensed water reservoir a and a water supply control valve may be disposed on a water supply line that connects the second reservoir and the water injection nozzle. Furthermore, a control unit may open the water supply control valve when judged determination by the control unit is made that the level of the water contained in the second reservoir is equal to or higher than a set value. 
         [0019]    The system may further include a fuel control valve which controls the fuel supplied to the fuel injection nozzle; and a main fuel control valve which controls the fuel supplied to the main fuel injection nozzle. 
         [0020]    Advantageously, according to an exemplary embodiment of the present invention, it is possible to reduce a size of an external humidifier or even completely remove a humidifier from the fuel cell system by reusing water generated in an air electrode or a fuel electrode. As such, the required external humidification can be greatly reduced by minimizing or removing water that moves from the air electrode to the fuel electrode and at the same time managing moisture within the fuel electrode. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is an overall configuration diagram of a fuel cell system. 
           [0022]      FIG. 2  is an overall configuration diagram of a fuel cell system having an ejector according to an exemplary embodiment of the present invention. 
           [0023]      FIG. 3  is a partial detailed cross-sectional view of a fuel cell system having an ejector according to a first exemplary embodiment of the present invention. 
           [0024]      FIG. 4  is a partial detailed cross-sectional view of a fuel cell system having an ejector according to a second exemplary embodiment of the present invention. 
           [0025]      FIG. 5  is a schematic configuration diagram of a fuel cell system having an ejector according to a third exemplary embodiment of the present invention. 
           [0026]      FIG. 6  is a schematic configuration diagram of a fuel cell system having an ejector according to a fourth exemplary embodiment of the present invention. 
           [0027]      FIG. 7  is a schematic configuration diagram of a fuel cell system having an ejector according to a fifth exemplary embodiment of the present invention. 
           [0028]      FIGS. 8A ,  8 B, and  8 C are schematic configuration diagrams illustrating a method for heating hydrogen in the fuel cell system having an ejector according to the exemplary embodiment of the present invention. 
           [0029]      FIG. 9  is a schematic configuration diagram illustrating a position of a heat exchanger that heats hydrogen in the fuel cell system having an ejector according to the exemplary embodiment of the present invention. 
           [0030]      FIGS. 10A and 10B  are a plan view and a side view illustrating a method for installing the ejector in the fuel cell system having an ejector according to the exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0031]    An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
         [0032]    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, fuel cell 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. 
         [0033]    Additionally, it is understood that the below methods are executed by at least one controller. The term controller refers to a hardware device that includes a memory and a processor configured to execute one or more steps that should be interpreted as its algorithmic structure. The memory is configured to store algorithmic steps and the processor is specifically configured to execute said algorithmic steps to perform one or more processes which are described further below. 
         [0034]    Furthermore, the control logic of the present invention 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 the computer readable mediums include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, flash drives, smart cards and optical data storage devices. The computer readable recording 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). 
         [0035]      FIG. 1  is an overall configuration diagram of a fuel cell system. Referring to  FIG. 1 , the fuel cell system may include a stack  210  including a cooling channel, a fuel electrode, and an air electrode. The fuel cell system may include a filter  130 , a silencer  140 , a compressor  150 , an intercooler  160 , a humidifier  170 , and a discharge valve  180  as components that circulates air to the air electrode of the stack  210 . 
         [0036]    The fuel cell system may also include a coolant reservoir  105 , a radiator  120 , and a water pump  110  as components that circulate coolant to the cooling channel, and an ejector  100 , a humidifier  220 , a reservoir  202 , a purge valve  190 , and a drain valve  200  as components that supply hydrogen which is fuel to the fuel electrode. 
         [0037]    In the exemplary embodiment of the present invention, the related art is referred to for a detailed description of structures and functions of respective components of the fuel cell system and a detailed description thereof will be omitted. Water is generated to from the air electrode in a proton exchange membrane fuel cell (PEMFC) of the stack  210  and conductivity of an electrode membrane is improved by moisture being supplied from the outside. That is, forming appropriate moisture to an MEA is essential for proper operation. 
         [0038]    As illustrated, a humidifier is included in a line that is circulated to the air electrode and the humidifier is installed at a hydrogen supply side to achieve proper operation. However, a separate installation space is required to install a separate humidifier and piping may be complicated. Moreover, the moisture (H 2 O) generated from the air electrode in the stack  210  is present in a liquid or vapor form depending on temperature and is transferred to the fuel electrode through a membrane of the air electrode due to a pressure difference. 
         [0039]    The amounts of water and vapor of the fuel electrode are changed depending on driving conditions and the water and vapor are discharged to the outside by a condensed water reservoir or drain valve through an appropriate method by reducing a hydrogen reaction. That is, an unbalanced driving pattern is provided in which the moisture is replenished from the outside in the air electrode and the moisture is discharged to the outside in the fuel electrode. 
         [0040]      FIG. 2  is an overall configuration diagram of a fuel cell system having an ejector according to an exemplary embodiment of the present invention.  FIG. 3  is a partial detailed cross-sectional view of a fuel cell system having an ejector according to a first exemplary embodiment of the present invention. 
         [0041]    Referring to  FIGS. 2 and 3 , a part of the fuel cell system may include the stack  210 , the condensed water reservoir  202 , the ejector  100 , a fuel injection nozzle  255 , a mixture pipe  280 , a water injection nozzle  267 , a water supply line  265 , a heater  260 , a to pressure sensor  280 , and a humidity sensor  282 . An intake chamber  275  is disposed inside the ejector  100  and the fuel injection nozzle  255  is disposed in the intake chamber  275 . 
         [0042]    A fuel injection aperture  270  is formed at the end of the fuel injection nozzle  255 The water injection nozzle  267  may be disposed inside the fuel injection nozzle  255 , and a water injection aperture  300  of the water injection nozzle  267  may be disposed at a center of the fuel injection aperture  270  of the fuel injection nozzle  255 . 
         [0043]    A fuel control valve  250  may be disposed in the system in order to control the flow of hydrogen which is the fuel supplied to the fuel injection nozzle  255  and a control unit  10  may be configured to control the fuel control valve  250  according to a driving condition including a load/pressure/humidity of the stack  210 . 
         [0044]    Furthermore, a water supply line  265  may be provided in order to supply water to the water injection nozzle  267 . This water supply line  265  may extend downward into the condensed water reservoir  202 . 
         [0045]    When the fuel control valve  250  is opened by the control unit  10 , the hydrogen may be injected from the fuel injection aperture  270  of the fuel injection nozzle  255 . At this point, a vacuum is formed by the injected hydrogen. As a result, water is pulled through the water supply line  265 , and is injected from the water injection aperture  300  of the water injection nozzle  267  in to the fuel injection nozzle  255 . 
         [0046]    In the exemplary embodiment of the present invention, the amount of moisture discharged from the stack  210  of the fuel cell varies due to various factors including driving temperature, pressure, and the like. As such, the hydrogen injected by the fuel injection nozzle  255  has a sonic velocity (Mach=1, approximately 1200 m/s) and the water is pulled into the fuel injection nozzle via vacuum pressure which is caused by the velocity. 
         [0047]    The water injected by the water injection nozzle  267  is atomized by the flow of the hydrogen to be mixed with the fuel. Moreover, supply/mixture performance of the fuel and the water may be improved by intermittently opening the fuel control valve  250 . 
         [0048]    In the exemplary embodiment of the present invention, when a driving load is increased, an operating temperature of the stack is increased, an inlet of the fuel electrode becomes dry, and the amount of discharge water is increased. As described above, the discharged water is recirculated to the fuel electrode again to reduce a size of an external humidifier or omit the external humidifier altogether. 
         [0049]      FIG. 4  is a partial detailed cross-sectional view of a fuel cell system having an ejector according to a second exemplary embodiment of the present invention. A description of similar parts will be skipped in  FIG. 4  as compared with  FIGS. 1 to 3  and only a distinct difference will be described. 
         [0050]    Referring to  FIG. 4 , a notch  400  is formed at the fuel injection aperture  270  of the fuel injection nozzle  255 . The notch  400  is formed inside the fuel injection aperture  300  ( FIG. 3 ) in an A or V shape and turbulence intensity of the hydrogen injected from the fuel injection nozzle  255  is increased to minimize and unify a particle size and strengthen a mixture of the hydrogen and the recirculated gas. 
         [0051]    In the exemplary embodiment of the present invention, water injection may be suppressed under a low-load condition and the water injection may be performed under a set load or more. Moreover, an inner diameter of the water supply line  265  may be controlled, an aperture (not illustrated) may be formed on the water supply line, or the height of the water supply line  265  may be controlled. In addition, a separate control valve (not illustrated) may be mounted on the water supply line  265  to actively control injection of water. 
         [0052]    Further, a heater  260  ( FIG. 2 ) may be applied to the mixture pipe  280  of the ejector  100  or the fuel recirculation line, and as a result, low-temperature operation efficiency may be improved by managing increasing the temperature of the water an internal circulation line. 
         [0053]      FIG. 5  is a schematic configuration diagram of a fuel cell system having an ejector according to a third exemplary embodiment of the present invention. A description of similar parts will be skipped in  FIG. 5  as compared with  FIGS. 1 to 4  and only a distinct difference will be described. 
         [0054]    Referring to  FIG. 5 , the fuel cell system includes the stack  210 , the condensed water reservoir  202 , the ejector  100 , the mixture pipe  280 , and the control unit  10 . A main fuel injection nozzle  255   a  is disposed at the center of the intake chamber  275  formed in the ejector  100 , and the control unit  10  controls a main hydrogen control valve  250   a  to control the amount of hydrogen injected from the main fuel injection nozzle  255   a.    
         [0055]    A fuel injection nozzle  255   b  may be disposed in the condensed water reservoir  202  and a water injection nozzle  267  may be disposed inside the fuel injection nozzle  255   b.  The water supply line  265  may extend to supply water contained in the condensed water reservoir  202  to the water injection nozzle  267 . 
         [0056]    Moreover, the control unit  10  may be configured to control a hydrogen control valve  250   b  that regulates the amount of hydrogen supplied to the fuel injection nozzle  255   b.  In addition, the amount of the water injected from the water injection nozzle  267  may also controlled according to the amount of hydrogen injected from the fuel injection nozzle  255   b.    
         [0057]    Additionally, the fuel injection nozzle  255   b  may be inclined to easily supply the fuel and the moisture to the ejector  100  from the condensed water reservoir  202 . 
         [0058]      FIG. 6  is a schematic configuration diagram of a fuel cell system having an ejector according to a fourth exemplary embodiment of the present invention. A description of similar parts will be skipped in  FIG. 6  as compared with  FIGS. 1 to 5  and only a distinct difference will be described. 
         [0059]    Referring to  FIG. 6 , the main fuel injection nozzle  255   a  is disposed at a center of the intake chamber  275  formed in the ejector  100 , and the control unit  10  may be configured to control the main hydrogen control valve  250   a  to regulate the amount of hydrogen injected from the main fuel injection nozzle  255   a.  In addition, a manifold  600  may be formed adjacent to the stack  210  and the hydrogen which is the fuel may be supplied to the stack  210  through the manifold  600 . 
         [0060]    The fuel injection nozzle  255   b  may be disposed in the manifold  600  and the water injection nozzle  267  may be disposed inside the fuel injection nozzle  255   b.  The water supply line  265  may extend into the condensed water reservoir  202  to supply the water contained in the condensed water reservoir  202  to the water injection nozzle  267 . 
         [0061]    Moreover, the control unit  10  may be configured to control the hydrogen control valve  250   b  to regulate the amount of hydrogen supplied to the fuel injection nozzle  255   b.  In addition, the amount of water injected from the water injection nozzle  267  may also be controlled according to the amount of hydrogen injected from the fuel injection nozzle  255   b.    
         [0062]      FIG. 7  is a schematic configuration diagram of a fuel cell system having an ejector according to a fifth exemplary embodiment of the present invention.  FIG. 7  is to compared with  FIG. 2  and a distinct difference will be described and a description of similar parts will be skipped. 
         [0063]    Referring to  FIG. 7 , the fuel cell system may include an air condensed water reservoir  710 , a level sensor  720 , and a water supply control valve  730 . The air condensed water reservoir  710  may be a space that is disposed on an air circulation line that is circulated in the air electrode to condense and collect moisture included in air. The water supply line  265  may supply water gathered in a lower portion of the condensed water reservoir  202  and water gathered in a lower portion of the air condensed water reservoir  710  to the water injection nozzle  267 . In addition, the water supply control valve  730  may regulate the supply of the water contained in the air condensed water reservoir  710 . 
         [0064]    A level sensor  720  that senses stored water may be disposed in the air condensed water reservoir  710 , and the control unit  10  may be configured to determine a level of water through the level sensor  720  and control the water supply control valve  730  according to sensed level. 
         [0065]    That is, when it is determined that the level of the water contained in the air condensed water reservoir  710  is below a given value, the control unit  10  may close the water supply control valve  730  and when it is determined that the level of the water is equal to or higher than a set value, the control unit  10  may open the water supply control valve  730 . Accordingly, air may be prevented from flowing into a line where the fuel of the fuel cell is circulated. 
         [0066]      FIGS. 8A ,  8 B, and  8 C are schematic configuration diagrams illustrating a method for heating hydrogen in the fuel cell system having an ejector according to the exemplary embodiment of the present invention. 
         [0067]    Referring to  FIG. 8A , the heater  260  may be installed within a hydrogen line supplied to the ejector  100  to heat hydrogen. 
         [0068]    Referring to  FIG. 8B , a heat exchanger may be installed within the hydrogen line supplied to the ejector  100  and coolant and hydrogen pass through the heat exchanger  800  and the hydrogen is heated by the coolant. 
         [0069]    Referring to  FIG. 8C , a heat exchanger  800  may be disposed within the hydrogen line supplied to the ejector  100 , condensed water may be discharged from the humidifier  170  through the discharge valve  180  and the discharged condensed water may pass through the heat exchanger  800 . The hydrogen may then be heated by the condensed water. 
         [0070]      FIG. 9  is a schematic configuration diagram illustrating a position of a heat exchanger that heats hydrogen in the fuel cell system having an ejector according to the exemplary embodiment of the present invention. Referring to  FIG. 9 , the stack  210  is installed at a front-wheel side of a vehicle and a hydrogen tank  900  is installed at a rear-wheel side. Hydrogen is supplied from the hydrogen tank  900  to the stack  210  and the heat exchanger  800  is installed within a supply line. Air discharged from the stack  210  to the outside may pass through the heat exchanger  800  and the discharged air heats the hydrogen. Further, the discharged air can pass through the ejector housing  290  to heat the hydrogen passing the ejector housing  290 . 
         [0071]      FIGS. 10A and 10B  are a plan view and a side view illustrating a method for installing the ejector in the fuel cell system having an ejector according to the exemplary embodiment of the present invention. 
         [0072]    Referring to  FIGS. 10A and 10B , the ejector  100  may be installed at an inlet side of a fuel supply manifold  101 , hydrogen may be injected from the ejector  100  and a to direction in which the hydrogen is injected and a longitudinal direction of the fuel supply manifold  101  may coincide with each other. Moreover, recirculated combustion gas discharged from a fuel discharge manifold  102  may be supplied to the ejector  100  and new hydrogen gas may also be supplied to the ejector  100 . 
         [0073]    While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 
       DESCRIPTION OF SYMBOLS 
       [0074]      10 : Control unit 
         [0075]      100 : Ejector 
         [0076]      210 : Stack 
         [0077]      255 : Fuel injection nozzle 
         [0078]      265 : Water supply line 
         [0079]      267 : Water injection nozzle 
         [0080]      280 : Mixture pipe