Air humidification device and air humidification method for fuel cell using injector

Provided are air humidification device and method for a fuel cell. The air humidification device and method for the fuel cell may cool an air compressor and air compressed by the air compressor and easily humidify air supplied to the fuel cell by mixing water with air and injecting the mixture into an inlet of the air compressor. In particular, the air humidification device and method may easily humidify air supplied to a cathode of the fuel cell by bypassing a portion of the compressed air from an outlet of an air compressor supplying air to the cathode of the fuel cell and simultaneously by injecting condensed water discharged from a fuel cell system into an inlet of the air compressor using the bypassed compressed air.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims under 35 U.S.C. §119 (a) the benefit of Korean Patent Application No. 10-2014-0065092 filed on May 29, 2014, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an air humidification device and a method for a fuel cell. The air humidification device and the method for a fuel cell may cool an air compressor and air compressed by the air compressor, and thus, air supplied to the fuel cell may be easily humidified by mixing water with air and injecting the mixture into an inlet of the air compressor.

BACKGROUND

A fuel cell vehicle is a vehicle which is driven by a fuel cell that converts chemical energy into electric energy by a reaction of oxygen and hydrogen. As the fuel cell used in the fuel cell vehicle, a polymer electrolyte membrane fuel cell has been typically used.

When the polymer electrolyte membrane is adequately dipped into water, ion conductivity of the polymer electrolyte membrane is increased, and as consequence, a loss by resistance is reduced. When relative humidity of air and hydrogen which are supplied to the polymer electrolyte membrane is substantially, moisture of the polymer electrolyte membrane is reduced and the ion conductivity of the polymer electrolyte membrane is reduced, and as consequence, the loss by resistance increases. Meanwhile, when reaction gas having substantially reduced humidity is continuously supplied, the electrolyte membrane is dried after all and thus may not be used as the electrolyte membrane at all. As such, in the polymer electrolyte membrane fuel cells, the supplied gas needs to be humidified.

Accordingly, various methods for humidifying a fuel cell for a vehicle have been developed, and as a currently used device for humidifying the fuel cell for the vehicle, a gas-gas membrane humidification device has been widely used.

The gas to gas membrane humidification device is based on a method for making fuel cell exhaust gas flow in a first surface thereof and gas flow in a second surface with a membrane through which only moisture may penetrate the membrane. In particular, the supplied gas is discharged from a stack and simultaneously receives heat and water from the exhaust gas of which the temperature is elevated and the moisture is saturated.

However, the gas to gas membrane humidification device may also be expensive due to high manufacturing cost of an exchange membrane. Further, the gas to gas membrane humidification device may not have sufficient humidification performance and may not perform sufficient humidification in a high load area, and as a result, a vehicle may stop on an uphill road.

Meanwhile, in the conventional membrane humidification device for humidifying the fuel cell, humidification amount may not be controlled optimally. In the related arts, injector type humidification may be generally used for controlling the humidification amount.

The injector type humidification refers to injecting water by the injector to atomize the water such that a surface area may increase for evaporating the water, thereby improving humidification effect.

The humidification using the injector may have advantages. For example, the humidification amount may be easily controlled, injector humidification technologies which have been applied and researched in other technical fields may be applied, cost of the device may be less, and the like.

In the related arts, as an example of the existing injector type humidification technology, a gas humidification device and a method for operating a fuel cell system have been developed. The device includes a water pump pumping water from an external supply source, an air compressor compressing external air, and a mixing chamber and a magnetic type injection nozzle for mixing and injecting the compressed air and the water.

However, the fuel cell system also includes several components such as the compressor, the mixing chamber, and the like in addition to the water pump, and when an additional device is installed, costs may increase and a mounting area may increase in volume. Further, since moving part components such water pump, injection nozzle, and the like in which water flow are exposed to the outside as they are, the water may be easily frozen or leaked in cold temperature conditions.

In another example from the related arts, a water supply device for a fuel cell has been provided. When a proper amount of water is pumped by a water pump, and at the same time, injected into an inlet of a screw compressor by a magnetic nozzle, the injected water may be compressed along with air, cooled by an after-cooler, and then supplied to the fuel cell in the water supply device.

However, as described above, since the moving part components such as water pump, magnetic nozzle, and the like in which water flows are also exposed to the outside as they are, the water may be easily frozen or leaked in the cold weather condition.

SUMMARY OF THE INVENTION

The present invention provides an air humidification device and an air humidification method for a fuel cell which may easily humidify air supplied to a cathode of the fuel cell and obtain an air cooling effect. As such, temperature elevation may be prevented in advance by compressing the supplied air, by bypassing a portion of the compressed air from an outlet of an air compressor supplying air to the cathode of the fuel cell, and simultaneously, by injecting condensed water discharged from the fuel cell system into an inlet of the air compressor by the bypassed compressed air.

In one aspect, the present invention provides an air humidification device for a fuel cell. In an exemplary embodiment, the air humidification device may include: an air compressor supplying air to a cathode of the fuel cell; and a sprayer disposed in an air supply line connected to an inlet of the air compressor and injecting condensed water discharged from the fuel cell from an outlet of the air compressor to the inlet of the air compressor using a pressure of the bypassed compressed air.

In particular, a bypass line connecting the outlet of the air compressor to an inlet of an injector may be provided with a bypass valve which may control an opening and closing angle.

In addition, the injector may be a binary spray nozzle, which may include: an outer hollow body having a first nozzle disposed at a central portion of one side of the outer hollow body; and an inner hollow body having a second nozzle which is inserted into the central portion of the first nozzle and disposed at one end the inner hollow body.

Moreover, the injector may be a binary spray nozzle including: an outer hollow body having a first nozzle disposed at a central portion of one side of the outer hollow body; and an inner hollow body having a second nozzle which is spacedly inserted into the central portion of the first nozzle and is disposed at one end thereof.

In particular, a space between the outer hollow body and the inner hollow body of the injector may be formed as a compressed air flow space which is communicatedly connected to the outlet of the air compressor by a bypass line. In addition, an inner space of the internal hollow body may be formed as a condensed water flow space which is communicatedly connected through a condensed water discharge line connected to a condensed water reservoir of the fuel cell.

Moreover, the outlet of the air compressor may be provided with a relative humidity measuring humidity sensor and a temperature measuring temperature sensor for air supplied to the cathode in parallel.

In another aspect, the present invention provides an air humidification method for a fuel cell, which may include: suctioning and compressing external air by an air compressor and supplying the compressed external air to the fuel cell; bypassing a portion of the compressed air from an outlet of the air compressor to an inlet side of the air compressor; injecting condensed water discharged from the fuel cell into the inlet of the air compressor and simultaneously suctioning the condensed water discharged from the fuel cell using a pressure of the compressed air bypassed to the inlet side of the air compressor; and passing the external air through the air compressor while the external air being humidified by the injected condensed water.

In particular, when an outlet temperature Toof the air compressor reaches a predetermined temperature Ttor greater, the injected condensed water may be bypassed to the inlet of the air compressor along with the compressed air; and when To is less than Tt, the injection of the condensed water may stop.

In addition, an injection amount of the condensed water may control a bypass amount of the compressed air bypassed from the outlet of the air compressor to the inlet thereby adjust a relative humidity at an outlet side of the air compressor to be equal to or less than about 100%.

Alternatively, an air humidification device for a fuel cell may include: an air compressor supplying air to a cathode of the fuel cell; and an injector disposed in an air supply line connected to an inlet of the air compressor and directly injecting condensed water discharged from the fuel cell to an inlet of the air compressor.

In particular, the injector may be a water injection nozzle which directly injects the condensed water from a condensed water reservoir in which the condensed water discharged from the fuel cell is stored through a condensed water discharge line.

Further, the present invention provides an air humidification method for a fuel cell. The method may include: suctioning and compressing external air by an air compressor and supplying the compressed external air to the fuel cell; directly injecting condensed water discharged from the fuel cell into an inlet of the air compressor using a water injection nozzle; and passing the external air through the air compressor while the external air being humidified by the injected condensed water.

By the above configuration, the present invention has various advantages. For example, the air supplied to the cathode of the fuel cell may be easily humidified by bypassing a portion of the compressed air from the outlet of the air compressor for supplying external air to the cathode of the fuel cell and simultaneously injecting the condensed water discharged from the fuel cell system into the inlet of the air compressor using the pressure of the bypassed compressed air. In addition, costs may be reduced by ruling out the conventional pump for supplying and pumping water, and the like. Further, a freezing phenomenon, a corrosion phenomenon, and the like of the water supply line including the pump and the like may be prevented by reusing the condensed water discharged from the fuel cell system in order to humidify the air. Moreover, the load of the humidifier may decrease by increasing the relative humidity of the air supplied to the cathode of the fuel cell from the inlet of the air compressor when a separate humidifier is further installed at the inlet side of the cathode. The humidification capacity and the size of the humidifier which is separately installed at the inlet side of the cathode may decrease by increasing the relative humidity of air supplied to the cathode of the fuel cell from the inlet of the air compressor in advance. In addition, cooling effect of the air compressed may be obtained by the condensed water injected into the inlet of the air compressor and the air compressor, thereby improving the aerodynamic performance and the efficiency of the air compressor. The humidification amount may also be controlled by adding a control element.

Also provided are preferred fuel cell systems that include fuel cell air humidification devices of the invention. In addition, preferred vehicle are provided and the vehicles comprise fuel cell systems including the fuel cell air humidification device of the invention.

100: binary spray nozzle

102: first nozzle

104: outer hollow body

108: inner hollow body

110: bypass line

120: condensed water reservoir

122: condensed water discharge line

114: compressed air flow space

124: condensed water flow space

200: fuel cell

202: air compressor

208: temperature sensor

210: water injection nozzle

212: exhaust pressure control valve

DETAILED DESCRIPTION

According to one aspect of the present invention, air supplied to a cathode of a fuel cell may be easily humidified by bypassing a portion of the compressed air from an outlet of an air compressor for supplying external air to the cathode of the fuel cell and simultaneously by injecting condensed water discharged from a fuel cell system into an inlet of the air compressor by using the bypassed compressed air.

FIG. 1illustrates an exemplary air humidification device for a fuel cell according to an exemplary embodiment of the present invention.

InFIG. 1, a binary spray nozzle100may be used as an injector for injecting water by using high-pressure air as a power source.

Accordingly, the injector may be a the binary spray nozzle100such that condensed water discharged from a fuel cell may be injected into an inlet side of an air compressor202in a spray form by suction pressure of compressed air.

As illustrated inFIG. 2, the binary spray nozzle100according to an exemplary embodiment of the present invention may include an outer hollow body104having a first nozzle102disposed at a central portion of one side of the outer hollow body104, and an inner hollow body108in which a second nozzle106is inserted into the central portion of the first nozzle102and is formed at one end of the inner hollow body. In particular, the first nozzle102and the second nozzle106may be in a concentric circle arrangement having the same center on the same vertical line.

As illustrated inFIG. 3, the binary spray nozzle100according to an exemplary embodiment of the present invention may include the outer hollow body104having the first nozzle102disposed at the central portion of one side thereof; and the inner hollow body108having the second nozzle106which is spacedly disposed into the central portion of the first nozzle102and disposed at one end thereof. The first nozzle102and the second nozzle106may be in an arrangement spaced apart from each other on the same vertical line.

The air compressor202may be, but not limited to, an air blower for compressing and supplying external air to a cathode of a fuel cell200or fuel cell stack. An outlet of the air compressor202may be connected to the cathode of the fuel cell200, and an inlet line of the air compressor202may be provided with a filter/flow rate sensor204which filters the external air and measures an external air flow rate.

In particular, the binary spray nozzle100may be disposed in an air supply line between the inlet of the air compressor202and the filter/flow rate sensor204.

Meanwhile, a bypass line110for bypassing a portion of the compressed air from the outlet of the air compressor202to the inlet of the binary spray nozzle100may be connected between the outlet of the air compressor202and the inlet of the binary spray nozzle100, particularly in the bypass line110, a bypass valve112which may control an opening and closing angle to control a supply amount of compressed air may be installed.

The condensed water generated during a reaction of the fuel cell may be discharged from the fuel cell and filled in a condensed water reservoir120, and a condensed water discharge line122for suctioning condensed water into the inlet of the spray nozzle100may be connected between an outlet of the condensed water reservoir120and the inlet of the binary spray nozzle100.

In particular, a bypass line110which may communicate with the outlet of the air compressor202may be connected to a space between an outer hollow body104and an inner hollow body108of the binary spray nozzle100. In other words, a compressed air flow space114and a condensed water discharge line122which may communicate with the condensed water reservoir120may be connected to an inner space of the inner hollow body108of the binary spray nozzle100or to a condensed water flow space124.

Meanwhile, in the outlet of the air compressor202, a humidity sensor206for measuring relative humidity and a temperature sensor208for measuring a temperature of air supplied to the cathode of the fuel cell200may be installed in parallel.

Hereafter, a method for humidifying a cathode of a fuel cell of the present invention based on the configuration will be described below.

In the initial operation of the fuel cell system, in order to generate electric energy by a reaction of hydrogen and oxygen in the air in the fuel cell stack, a process of suctioning and compressing external air by the air compressor202and supplying the external air to the cathode of the fuel cell200is first performed. In this process, a portion of the compressed air supplied from the outlet of the air compressor202to the cathode of the fuel cell200may be supplied to the binary spray nozzle100along the bypass line110. Simultaneously, condensed water generated during the reaction of the fuel cell and collected into the condensed water reservoir120may be supplied to the binary spray nozzle100. In particular, the condensed water in the condensed water reservoir120may be suctioned and supplied into the binary spray nozzle100by flow pressure formed by locally reduced pressure of the compressed air which is bypassed from the outlet of the air compressor202and supplied to the binary spray nozzle100.

Accordingly, when the compressed air is bypassed from the outlet of the air compressor202and supplied to the binary spray nozzle100, the supplied compressed air may be injected to the inlet side of the air compressor202through the first nozzle102via the compressed air flow space114which is a space between the outer hollow body104and the inner hollow body108of the binary spray nozzle100.

At the same time, the condensed water suctioned from the condensed water reservoir120may be injected into the inlet of the air compressor202through the second nozzle102via the condensed water flow space124which is the inner space of the inner hollow body108of the binary spray nozzle100. In other words, the condensed water injected through the second nozzle102may be injected in a spray form by injection pressure of the compressed air which is injected through the first nozzle102.

The condensed water discharged from the fuel cell may be suctioned by pressure of the bypassed compressed air and simultaneously injected into the inlet of the air compressor202, and thus the external air passing through the filter/flow rate sensor204may pass through the air compressor202while being humidified by the injected condensed water to be supplied to the cathode of the fuel cell.

As described above, a cooling effect absorbing heat energy of air increased by an air compression process performed by the air compressor may be obtained and air supplied to the cathode of the fuel cell may be easily humidified by injecting the condensed water discharged from the fuel cell system into the inlet of the air compressor202using the pressure of the bypassed compressed air and simultaneously by bypassing some of the compressed air from the outlet of the air compressor for supplying external air to the cathode of the fuel cell200.

When a separate humidifier is further mounted at the inlet side of the cathode, the relative humidity of air supplied to the cathode of the fuel cell may increase from the inlet of the air compressor in advance and the air may be supplied to the humidifier, and as consequence, a load for a humidification operation of the humidifier may be reduced and the humidification capacity and the size of the humidifier separately mounted at the inlet side of the cathode may decrease.

Meanwhile, when an outlet temperature Toof the air compressor202reaches a targeted temperature Tt, the bypass valve112mounted in the bypass line110may be opened and thus the injected condensed water may be bypassed to the inlet of the air compressor202together with the compressed air from the outlet of the air compressor202. Further, when the outlet temperature Toof the air compressor202is equal to or less than the target temperature Tt, an injection amount of the condensed water may be controlled by controlling a bypass valve.

Particularly, the injection amount of the condensed water may control a bypass amount of the compressed air which may be bypassed from the outlet of the air compressor to the inlet to adjust the relative humidity at the outlet of the air compressor to be equal to or less than about 100% and adjust a relative humidity (RH) to be equal to or less than about 100% in a state in which the outlet temperature Toof the air compressor is equal to or greater than the target temperature Ttand the relative humidity (RH) may be equal to or greater than about 100% or saturated depending on a type of the compressor. For example, in the case of a volumetric compressor such as screw, roots, and the like, compression efficiency may increase by a seal operation of water to perform a control to adjust the RH to be equal to or greater than about 100% such that the condensed water is generated.

As such, by determining whether to inject the condensed water depending on the outlet temperature of the air compressor and simultaneously by reusing the condensed water discharged from the fuel cell system for air humidification, costs may be saved by omitting conventional pump and the like for supplying an pumping water and a freezing phenomenon, a corrosion phenomenon, and the like of a water supply line including the pump, and the like may be prevented.

Alternatively, in an exemplary embodiment of the present invention, the condensed water discharged from the fuel cell may be reused for air humidification by using a water injection nozzle for injecting only water. As illustrated inFIG. 4, a water injection nozzle210which may inject only water may be disposed in the air supply line which is connected to the inlet of the air compressor202supplying air to the cathode of the fuel cell.

Particularly, a means which supplies water to the water injection nozzle210may include the condensed water reservoir120which temporarily stores the condensed water discharged from the fuel cell and a condensed water discharge line122which is directly connected between the outlet of the condensed water reservoir120and the water injection nozzle210. In this case, compared to a rear end (outlet) position of the air compressor202, a section between the rear end of the air compressor202and the exhaust pressure control valve212may have increased pressure. Although the binary spray nozzle for high pressure air and water is replaced with the water injection nozzle210injecting only water, the water injection may still be performed.

As such, the condensed water may be supplied from the condensed water reservoir120in which the condensed water discharged from the fuel cell is stored to the water injection nozzle210through the condensed water discharge line122and then may be injected into the inlet of the air compressor202, such that the external air passing through the filter/flow rate sensor204by the injected condensed water may pass through the air compressor202while being humidified and then is supplied to the cathode of the fuel cell.

As such, according to various exemplary embodiments of the present invention, the condensed water discharged from the fuel cell system may be directly injected into the inlet of the air compressor202by using the water injection nozzle210, thereby easily humidifying the air supplied to the cathode of the fuel cell.