Fuel cell recirculation system

Abstract

A fuel recirculation system manages fuel cell humidity requirements during the continuous operation of the vehicle by separating / injecting the water into the fuel line. During vehicle shutdown, the fuel recirculation system operates in a dehumidification mode in which fuel outlet from the fuel cell stack repeatedly cycles through a water separator and / or purge valve without being routed back to the fuel cell stack. Contaminated fuel from a gear case or sealing region of a blower also can be purged from the system. An example water separator includes a valve arrangement having a float-type actuator to selectively allow liquid water past a membrane to the storage tank.

Description

FUEL CELL RECIRCULATION SYSTEMCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of Indian Provisional Application No. 202311078579, filed November 20, 2023, the disclosure of which is incorporated by reference in its entirety.BACKGROUND

[0002] A fuel recirculation system within a vehicle power cell system may be vulnerable to failure at low ambient conditions due to ice formation in the flow channels. For example, in the anode loop of a fuel cell system, when the recirculated gas rich in vapor combines with the fuel from storage tanks having relatively lesser temperature than that of the recirculated gas, the combined mixture condenses. This condensed mixture, which may include liquid water, stays in the flow channel and can reach the blower housing when the blower is not in operation. When the ambient temperature is low, the condensed water may freeze to ice. The ice may inhibit operation of the blower or other components of the fuel cell recirculation system. In addition, when the amount of water is large, an excess of vapors will be supplied to the fuel cell stack which can cause the blockage of flow channels and hence reduced efficiency of the fuel cell stack and / or of the blower. For example, liquid in the blower can impact isentropic efficiency and / or volumetric efficiency.SUMMARY

[0003] A fuel recirculation system manages fuel cell humidity requirements during the continuous operation of the vehicle by separating / injecting the water into the fuel line. The recirculation system includes a blower, a water separator, and a purge valve.

[0004] In accordance with certain aspects of the disclosure, during vehicle shutdown, the fuel recirculation system operates in a dehumidification mode in which fuel outlet from the fuel cell stack repeatedly cycles through a water separator and / or purge valve without being routed back to the fuel cell stack.

[0005] In accordance with certain aspects of the disclosure, contaminated fuel (e.g., fuel contaminated with lubrication) from a gear case or sealing region of a blower also can be purged from the system.

[0006] In accordance with certain aspects of the disclosure, An example water separator includes a valve arrangement having a float-type actuator to selectively allow liquid water past a membrane to the storage tank.

[0007] A variety of additional inventive aspects will be set forth in the description that follows. The inventive aspects can relate to individual features and to combinations of features. It is to be understood that both the forgoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the broad inventive concepts upon which the embodiments disclosed herein are based.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The accompanying drawings, which are incorporated in and constitute a part of the description, illustrate several aspects of the present disclosure. A brief description of the drawings is as follows:

[0009] FIG. l is a schematic diagram showing a recirculation system for a fuel cell stack, the recirculation system including a blower, a water separator, and a purge valve in accordance with the principles of the present disclosure.

[0010] FIG. 2 illustrates an operating flow path within the recirculation system of FIG. 1.

[0011] FIG. 3 illustrates a water supplementing flow path within the recirculation system of FIG. 1.

[0012] FIG. 4 illustrates a dehumidification loop within the recirculation system of FIG. 1.

[0013] FIG. 5 is a flow chart illustrating a vehicle shutdown process during which fluid is cycled through the dehumidification loop.

[0014] FIG. 6 is a schematic diagram of the recirculation system of FIG. 1 including a valve arrangement to selectively isolate the ejector and including a vent line from the blower, the recirculation system being configured to mix flow from the vent line, gases purged at the purge valve, and water condensed at the water separator at a location external of the water separator.

[0015] FIG. 7 illustrates an example implementation of a blower suitable for use in any of the recirculation system described herein, the blower including a pump, a gear case, and a sealing chamber therebetween.

[0016] FIG. 8 illustrates an example water separator and an example purge valve mounted together at the example blower of FIG. 7, the blower including a vent channel from a sealing chamber.

[0017] FIG. 9 illustrates an example water separator and an example purge valve mounted together at the example blower of FIG. 7 except the blower includes a vent channel extending from the gear case.

[0018] FIG. 10 illustrates another example water separator and an example purge valve mounted together at an example blower that includes both a pump and an ejector, the ejector being selectively accessible through a first example type of check valve.

[0019] FIG. 11 illustrates the example water separator and the example purge valve of FIG. 10 mounted together at an example blower that includes both a pump and an ejector, the ejector being selectively accessible through a second example type of check valve.

[0020] FIG. 12 illustrates the example water separator and the example purge valve of FIG. 11 mounted together at an example blower that includes both a pump and an ejector, the pump and the ejector each being selectively accessible through a third example type of valve arrangement.

[0021] FIG. 13 is a schematic diagram of the recirculation system of FIG. 1 including a valve arrangement to selectively isolate the pump and / or the ejector and including a vent line from the blower to a water storage tank of the water separator, the recirculation system being configured to direct the gases purged at the purge valve and fluid flow vented from the vent line into the storage tank of the water separator and to selectively release the mixture from the storage tank to a diffuser.

[0022] FIG. 14 illustrates an example implementation of the blower, the water separator, and the purge valve of FIG. 13, the blower including a vent channel extending from the sealing chamber.

[0023] FIG. 15 illustrates an example implementation of the blower, the water separator, and the purge valve of FIG. 13, the blower including a vent channel extending from the gear case.

[0024] FIG. 16 illustrates an example implementation of the blower, the water separator, and the purge valve of FIG. 13, the blower including an ejector selectively accessible through a first example type of valve arrangement.

[0025] FIG. 17 illustrates an example implementation of the blower, the water separator, and the purge valve of FIG. 13, the blower including an ejector selectively accessible through a second example type of valve arrangement.

[0026] FIG. 18 illustrates an example implementation of a water separator suitable for use within any of the blowers and purge valves disclosed herein.

[0027] FIG. 19 illustrates an example implementation of a purge valve suitable for use with any of the blowers and water separators disclosed herein.DETAILED DESCRIPTION

[0028] Reference will now be made in detail to exemplary aspects of the present disclosure that 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.

[0029] A fuel cell system converts chemical energy into electrical energy to supply a motor or other powered mover of a vehicle or other device. The fuel cell system includes a fuel cell stack having an anode side and a cathode side. Hydrogen is supplied to the anode side while oxygen is supplied to the cathode side to provide reactions therebetween.

[0030] FIGS. 1, 6, and 13 shows various configurations of a recirculation system 100 for the anode side of the fuel cell stack 102. The recirculation system 100 supplies hydrogen or other fuel to the anode side of the fuel cell stack 102. In certain implementations, the recirculation system 100 directs unreacted fuel leaving an outlet 106 of the fuel cell stack 102 back towards an inlet 104 of the fuel cell stack 102. In certain cases, the unreacted fuel leaves the fuel cell stack 102 in a flowing mixture of water vapor, fuel (e.g., H2), and other gases (e.g., N2). In certain examples, the recirculation system 100 processes the flowing mixture to remove all or part of the water and / or other gases before directing the remaining unreacted fuel back to the fuel cell stack 102. In certain examples, fresh fuel from a fuel source 108 is added to the flowing mixture directed back to the fuel cell stack 102.

[0031] In certain implementations, hydrogen or other fuel from the fuel source 108 is directed to the inlet 104 of the fuel cell stack 102. In certain implementations, the hydrogen or other fuel is driven to the inlet 104 using an injector 110. In certain examples, a pressure regulator 112 can be disposed between the fuel source 108 and the injector 110 to manage the pressure of the fuel reaching the injector 110. For example, the hydrogen or other fuel may be kept highly pressurized within the fuel source 108 and may be partially or fully depressurized at the pressure regulator 112 before being directed towards the fuel cell stack 102.

[0032] In certain implementations, the recirculation system 100 includes a blower 114 that pulls the flowing mixture from the stack outlet 106 and directs the flowing mixture towards the stack inlet 104. In certain implementations, the blower 114 includes a pump 152 (e.g., a motorized pump) that directs the flowing mixture along a pump path through the blower 114. In some implementations, the blower 114 includes an ejector 154 that pulls the flowing mixture along an ejector path (e.g., through the blower 114, alongside the blower 114, etc.) when pressurized fuel is supplied from the fuel source 108. In other implementations, an ejector 154 can be installed in parallel with the blower 114 to pull the flowing mixture along an ejector path. In such implementations, the flow from the pump path can be combined with the flowfrom the ejector path downstream of the blower 114 and upstream of the fuel cell stack inlet 104.

[0033] In certain implementations, an injector 142 can be installed at an inlet of the ejector 154 (e.g., see FIGS. 6, 11, 12, and 13). In certain implementations, the injector 142 can be integrated into a housing of the ejector 154. In certain examples, the injector 142 can be integrated into a common housing of the ejector 154 and the blower 114. In certain implementations, the injector 142 directs fresh fuel towards a nozzle of the ejector 154.

[0034] In certain implementations, a water separator 116 removes water (e.g., liquid water and / or water vapor) from the flowing mixture leaving the outlet 106 of the fuel cell stack 102 before the flowing mixture is returned to the inlet 104 of the stack 102. In certain examples, the water separator 116 removes the water before the flowing mixture reaches the blower 114. In certain implementations, a purge valve 118 removes nitrogen or other gases from the flowing mixture prior to the flowing mixture being returned to the stack inlet 104. In certain examples, the purge valve 118 removes the nitrogen or other gases before the flowing mixture reaches the blower 114. In certain examples, the purge valve 118 removes the nitrogen or other gases before the flowing mixture reaches the water separator 116. In some implementations, the purge valve 118 and water separator 116 are joined at a common housing or are otherwise coupled to each other as will be discussed in more detail herein with reference to FIGS. 6-17. In other implementations, however, the purge valve 118 may be separate from and disposed upstream of the water separator 116 (e.g., as shown in FIG. 1). In certain implementations, the purge valve outputs gases to be purged to a diffuser 119. In certain examples, the diffuser 119 chemically reacts with one or more of the gases to be purged to render the gas inert or otherwise safe for release into the atmosphere. For example, the diffuser 119 may react Hydrogen (H2) with oxygen (02) to produce water.

[0035] In certain implementations, the recirculation system 100 is configured to manage the levels of components forming the flow mixture routed through the recirculation system 100 by controlling when these components either enter the system 100 or leave the system 100. The recirculation system 100 includes an arrangement of one or more valves 120 that define multiple potential paths through the recirculation system 100 for adding and / or removing mixture components. A first flow path Pl is utilized during normal operation of the vehicle to supply fresh and recirculated fuel to the fuel cell stack (e.g., see FIG. 2). A second flow path P2 supplements the first flow path Pl to supply water to the stack inlet 104 without passing the water through the blower 114 (e.g., see FIG. 3). A third flow path P3 isolates the inlet 104 ofthe fuel cell stack 102 from the recirculated flow mixture (e.g., see FIG. 4) as will be described in more detail herein.

[0036] In certain implementations, a first valve 122 of the arrangement of valves 120 is disposed along the second flow route P2. When closed, the first valve 122 blocks water from a storage tank of the water separator 116 from reaching the inlet 104 of the fuel cell stack 102. When open, the first valve 122 allows water from the storage tank of the separator 116 to bypass the blower 114 and to feed into an input flow path 130 leading to the stack inlet 104. Accordingly, water removed from the flow channels and stored in the water separator 116 can be reintroduced back into the system for reuse. For example, the stored water can be used to humidify the cell membranes during start-up of the vehicle. In certain examples, the stored water is reintroduced through direct injection in the anode flow channels or the stack inlet 104.

[0037] In certain examples, the first valve 122 is closed during normal operation of the vehicle. In certain examples, the first valve 122 is closed during parking of the vehicle. In certain implementations, the first valve 122 is open (e.g., see FIG. 3) when the vehicle is started and the humidity in the fuel cell stack 102 is lower than a predetermined humidity threshold. The humidity threshold is selected based on the requirement for activation of membrane proton transport at the fuel cell stack 102. Water (e.g., water vapor) from the water separator 116 flows along the second flow path P2, through the first valve 122, to the input flow path 130. By bypassing the blower 114, the water provided from the water separator storage tank does not condense and / or ice over within the blower 114. Once humidity within the stack 102 reaches the humidity threshold, the first valve 122 is closed to block the second flow path P2.

[0038] In certain implementations, during normal operation of the vehicle, the flow mixture follows the first flow path Pl. For example, the water leaves the stack outlet 106 and flows through the purge valve 118 and water separator 116 to filter out undesired components (e.g., water and nitrogen) of the flow mixture (e.g., see FIG. 2). A remainder of the flow mixture passes through the blower 114 (e.g., driven by the pump and / or the ejector of the blower 114) and combines with fresh fuel from the fuel source 108. The combined flow mixture leaves the blower 114 and is then routed back to the stack inlet 104 along the input flow path 130.

[0039] When the vehicle is parked or otherwise stopped for an extended period, the recirculation system 100 performs a dehumidification operation. During the dehumidification operation, the valve arrangement 120 closes the first flow path Pl and opens the third flow path P3. The third flow path P3 isolates the inlet 104 of the fuel cell stack 102 from the blower 114 and water separator 116. Accordingly, the blower 114 continues to operate to circulate themixture through the purge valve 118 and water separator 116 until a sufficient amount of water and / or gases (e.g., N2) has been purged from the mixture. In certain examples, the valve arrangement 120 enables the flow mixture leaving the fuel cell stack outlet 106 to be pulled by the blower 114 into the dehumidification loop. However, the valve arrangement 120 does not allow the mixture from the dehumidification loop to enter the input flow path 130. Running the mixture through the dehumidification loop removes water vapor in the flow channels to inhibit ice formation within the flow channels. Mitigating ice formation within the flow channels facilitates a smooth start-up of the fuel cell system after being parked even in low temperatures and / or for an extended period of time.

[0040] In certain implementations, the valve arrangement 120 includes a first isolation valve 124 and a second isolation valve 126. The first isolation valve 124 is disposed downstream of the cell stack outlet 106 and upstream of the purge valve 118. The second isolation valve 126 is disposed downstream of the blower 114 and upstream of the input flow path 130. In certain implementations, one or both of the isolation valves 124, 126 include three-way valves. In certain implementations, the first and second isolation valves 124, 126 are managed by an electronic controller 135. For example, the electronic controller 135 can send electrical signals (see dashed lines) to selectively actuate the isolation valves 124, 126 to open and close the first and third flow paths Pl, P3. In certain examples, the electronic controller 135 also can manage the first valve 122 to selectively open and close the second flow path P2. In other implementations, one or more of the valves 122, 124, 126 can be hydraulically controlled or otherwise controlled.

[0041] FIG. 5 is a flow chart illustrating an example vehicle shut down process 140. The vehicle shut down process 140 begins at a receive step 141 at which a signal is received (e.g., at the electronic controller 135). The signal indicates that the vehicle is being parked or has been parked. For example, the signal may indicate that the parking mode of the vehicle has been engaged. In a stop step 143, the injector 110 ceases to inject fresh fuel from the source 108 into the input flow path 130.

[0042] In a close step 145, the second isolation valve 126 stops directing flow output from the blower 114 (and / or ejector) to the input flow path 130. Rather, the second isolation valve 126 redirects the mixture leaving the blower 114 and / or ejector back to the first isolation valve 124. The first isolation valve 124 receives the redirected mixture from the second isolation valve 126 and directs that mixture back to the purge valve 118 and / or the water separator 116 to form a dehumidification loop. In certain examples, the first isolation valve 124 also directs any fluid received from the cell stack outlet 106 into the dehumidification loop.

[0043] In a perform step 147, the recirculation system 100 operates the dehumidification loop in accordance with a predetermined strategy. In some implementations, the blower 114 operates the pump at a predetermined rate of speed for a predetermined period of time. In certain implementations, the blower 114 operates the pump at decreasing rates of speed for predetermined periods of time. In certain examples, the blower 114 may run multiple cycles where the pump progressively steps down a recirculation rate of the fluid within the dehumidification loop. In other implementations, the blower 114 continues to operate until a predetermined level of water within the dehumidification loop is reached. In other implementations, the blower 114 continues to operate until the fuel cell stack reaches a predetermined state of charge. The recirculation system 100 shuts down at step 149 when the dehumidification strategy has been run.

[0044] In certain implementations, the ejector 154 can be isolated from the dehumidification loop using a valve arrangement 128. For example, an inlet valve 128a can be disposed at the inlet of the ejector 154 and an outlet valve 128b can be disposed at the outlet of the ejector 154 (e.g., see FIG. 6). In some examples, the inlet and outlet valves 128a, 128b close during vehicle shut down so that only the pump directs the fluid through the dehumidification loop. In other examples, the inlet valve 128a and / or the outlet valve 128b can be left open to allow fluid to enter and / or exit the ejector 154 during the dehumidification cycle. In other implementations, the inlet valve 128a and outlet valve 128b are disposed to control flow into and out of the pump 152 instead of or in addition to the ejector 154.

[0045] In accordance with certain aspects of the disclosure, one or more vent channels 176 can be integrated into the blower 114 to drain or otherwise remove any recirculation fluid that has leaked or otherwise flowed outside the sealed pump portion 152 of the blower 114 (e.g., see FIGS. 6-17). In some implementations, fluid from the vent channel 176 can be directed outside the blower 114 along a vent line 160 and combined with condensed water output from the water separator 116 and then directed to the diffuser 119 (e.g., see FIGS. 6-12). In other implementations, the vent channel 176 can be outlet into or directed to the storage tank of the water separator (e.g., see FIGS. 13-17).

[0046] FIG. 7 shows an example implementation of a blower 114. As shown, the blower 114 includes a pump 152 having rotors driven by shafts 170 that extend into a gear case 158. A motor 156 drives the shafts 170 to turn the rotors. In certain implementations, a sealing arrangement is disposed at a sealing chamber 175 between the pump 152 and the gear case 158 to inhibit mixing of the fluid (e.g., fuel, water vapor, and other gases) passing through the pump 152 and the lubrication (e.g., oil) disposed within the gear case 158. In certain examples, thesealing arrangement includes a gas seal 172 disposed around each shaft 170 at the pump side of the chamber 175 and an oil seal 174 disposed around each shaft 170 at the gear case side of the chamber 175. In certain examples, a dust seal 173 may be disposed at an opposite side of the pump 152 along the pump shaft 170.

[0047] In certain implementations, the vent channel 176 extends from the sealing chamber 175 to an exterior of the blower 114 (e.g., see FIGS. 7 and 8). Fluid that passes the gas seal 172 from the pump 152 into the sealing chamber 175 and / or any lubrication that passes the oil seal 174 from the gear case 158 into the sealing chamber 175 can be evacuated from the blower 114 along the vent channel 176. As fluid (e.g., recirculation fluid and / or lubrication) builds up in the sealing chamber 175, the pressure of the fluid increases, which presses the fluid out of the sealing chamber 175 along the vent channel 176. In certain examples, a check valve 178 is disposed along the vent channel 176 to inhibit back flow into the channel 176 even as the pressure within the sealing chamber 175 drops. Relieving the pressure within the sealing chamber 175 mitigates the passage of contaminated fluid (e.g., recirculation fluid mixed with lubrication) back into the pump 152.

[0048] In other implementations, the vent channel 176 extends from the gear case 158 (e.g., see FIG. 9). In such implementations, the vent channel 176 facilitates evacuation of any recirculation fluid that passed through the sealing chamber 175 to the gear case 158. The vent channel 176 inhibits pressure from building up at the gear case 158, which mitigates any flow from the gear case 158 back across the sealing chamber 175. The check valve 178 inhibits fluid external of the blower 114 from flowing back into the gear case 158 along the vent channel 176.

[0049] As shown in FIGS. 8-12, the purge valve 118 and water separator 116 can be mounted together at the blower 114. For example, recirculation fluid leaving the stack outlet 106 can pass to the purge valve 118. At the purge valve 118, the fluid can be directed either to an inlet 165 of the water separator 116 or to a purge line 167. In certain implementations, the purge valve 118 directs the fluid to the purge line 167 when a sensed fuel level of the recirculation fluid drops below a predetermined threshold, when a sensed nitrogen level of the recirculation fluid climbs above a predetermined threshold, or at predetermined periods of operation of the recirculation system 100.

[0050] Fluid directed to the water separator inlet 165 enters the water separator 116. Within the water separator 116, water vapor is condensed into liquid water, which is transferred to a storage tank 182. A valve 166 (e.g., a check valve) at the storage tank 182 selectively allows the liquid water to leave the storage tank 182 along a combined purge line 168. Incertain examples, the combined purge line 168 leads to the diffuser 119. In certain implementations, fluid drained from either the sealing chamber 175 or the gear case 158 of the blower 114 passes beyond the valve 178, along a drain line 160, to a valve 162 (e.g., a check valve). When open, the valve 162 allows the drained fluid access to the combined purge line 168.

[0051] In certain implementations, an intermediate purge line 167 extends from the purge valve 118 towards the combined purge line 168. In certain examples, the intermediate purge line 167 may have a nozzle leading to the combined purge line 168. In certain examples, the combined purge line 168 has a converging-diverging shape. When the valve 162 is open, flow from the intermediate purge line 167 to the combined purge line 168 may suck fluid from the drain line 160 into the combined purge line 168.

[0052] A remainder of the fluid (e.g., hydrogen fuel) is directed to an inlet 151 of the blower 114 and passes through the blower 114 to an outlet 153. In FIGS. 8 and 9, the inlet 151 leads to the pump 152, which leads to the outlet 153. In FIGS. 10 and 11, the inlet 151 leads to both the pump 152 and an ejector 154. In FIG. 10, the check valve arrangement 128a is a ball valve that selectively allows access to the ejector 154. In FIG. 11, the check valve arrangement 128a is a flapper valve that allows access to the ejector 154, but inhibits back flow from the ejector 154. In FIG. 12, the check valve arrangement 128a includes a first check valve providing selective access to the pump 152 and a second check valve providing selective access to the ejector 154.

[0053] In accordance with certain aspects of the disclosure, a vent line 160 leads from a blower 114 (e.g., from the check valve 178) to the storage tank 182 of a water separator 116 (e.g., see FIGS. 13-17). In certain implementations, the water separator 116 is mounted directly to the blower 114. In certain implementations, the purge valve 118 is mounted directly to the water separator 116. In such implementations, the purge valve 118 directs purged gases (e.g., N2) along a purge line 167 to the storage tank 182. A combination of fluid from the vent line 160 and purged gases from the purge valve 118 collect in the storage tank 182 until evacuated (e.g., to the diffuser 119, to ambient, etc.) via a water separator outlet 169.

[0054] When not purging, the purge valve 118 directs the recirculation fluid to a first inlet 165 of the water separator 116. From the first inlet 165, the recirculation fluid divides into liquid water in the storage tank 182 and gaseous fluid directed to the inlet 151 of the blower 114. In certain implementations, the inlet valve arrangement 128a enables fluid entering the blower 114 from the water separator 116 to be directed selectively to the pump 152 and / or the ejector 154. In certain implementations, the inlet valve arrangement 128a (e.g., one or morecheck valves such as ball valves, flapper valves, etc.) selectively closes access to the ejector 154. In certain implementations, the inlet valve 128a selectively closes access to the pump 152. In certain implementations, the inlet valve 128a allows access from the water separator 116 to both the pump 152 and the ejector 154. In other implementations, the inlet valve arrangement 128a only controls access to the ejector 154 and not to the pump 152.

[0055] FIG. 18 illustrates an example implementation 180 of a water separator 116 suitable for use in any of the configurations for a recirculation systems 100 shown above. The water separator 180 includes a condensation region 184, a buffer region 186, and a storage tank 182. In some implementations, the condensation region 184 includes a baffle arrangement upon which the water vapor may condense. In other implementations, the condensation region 184 may have other structure to condense the water vapor. The condensation region 184 defines the first inlet 165 at which a first portion of the recirculation fluid is received from the purge valve 118. In particular, the first portion of the recirculation fluid is the portion not intended to be purged. In certain examples, this portion includes primarily fuel and water vapor.

[0056] In some implementations, the condensation region 184 and buffer region 186 are separated by a porous wall. In other implementations, the condensation region 184 and buffer region 186 are open to each other. In certain implementations, the buffer region 186 is disposed beneath the condensation region 184 so that condensed water will drip from the condensation region 184 into the buffer region 186. A membrane 188 separates the buffer region 186 and the storage tank 182. The membrane inhibits liquid water from passing from the buffer region 186 into the storage tank 182. In certain implementations, the membrane 188 is hydrophobic. The membrane 188 defines a passage 187 fluidly connecting the buffer region 186 and the storage tank 182. A valve arrangement 195 selectively opens and closes the passage 187.

[0057] In certain implementations, the valve arrangement 195 is disposed at least partially within the buffer region 186. In certain examples, the valve arrangement 195 also is partially disposed within the storage tank 182. The valve arrangement 195 is configured to open the passage 187 when the buffer region 186 fills to a predetermined level of liquid water. The collected water will cover the entrance to the passage 187, thereby inhibiting any gas from passing from the buffer region 186, along the passage 187, to the storage tank 182. In certain examples, the valve arrangement 195 is configured to re-close the passage 187 while some liquid water remains in the buffer region 186 so that the passage entrance remain covered.

[0058] In certain implementations, the valve arrangement 195 includes a piston 192 movable (e.g., slidable) relative to the membrane 188 between an open position and a closedposition. In certain examples, the piston 192 is biased (e.g., spring biased) to the closed position. In some examples, the piston 192 carries a seal 194 to open and close the passage 187. In other examples, the piston 192 moves relative to the seal 194 to open and close the passage 187. In certain implementations, the valve arrangement 195 includes an actuator 190 that controls movement of the piston 192. In certain examples, the actuator 190 includes a float disposed within the buffer region 186. As liquid water collects in the buffer region 186, the float rises and thereby moves the piston 192. In the example shown in FIG. 18, the actuator 190 includes a pivoting lever having a float at one end. As the float rises in the buffer region 186, the opposite end of the lever pushes the piston 192 against the bias of the biasing member towards the open position to open the passage 187 to the storage tank 182.

[0059] The storage tank 182 defines a second inlet 181 at which a second portion of the recirculation fluid is received from the purge valve 118. The second portion of the recirculation fluid is the portion intended to be purged. In certain examples, this portion includes a large percentage of nitrogen (N2). In certain implementations, the storage tank 182 also defines a third inlet 183 from the drain line 160 extending from the blower 114. Accordingly, both fluid being purged from the flow channels of the recirculation system 100 and fluid being purged from the gear case 158 and / or sealing chamber 175 of the blower 114 can be collected at the storage tank 182.

[0060] FIG. 19 illustrates an example implementation 200 of a purge valve 118 suitable for use with the various configurations of a recirculation system 100 disclosed above. The purge valve 200 includes a body 201 defining an inlet 202, a first outlet 204, and a second outlet 206. The inlet 202 receives recirculation fluid that leaves the fuel cell stack outlet 106. The inlet 202 is fluidly connected to the first outlet 204 through a passage 203 and is fluidly connected to the second outlet 206 through a passage 205. A piston 208 selectively opens and closes the passages 203, 205. In certain implementations, only one of the passages 203, 205 is open at any given time.

[0061] In certain implementations, the piston 208 is configured to move (e.g., slide) relative to the body 201 between a first position and a second position. In certain implementations, the piston 208 includes a first stop member 210 fixedly connected to a second stop member 212 so that the first and second stop members 210, 212 move together as a unit. When the piston 208 is disposed in the first position, the first stop member 210 opens the passage 203 and the second stop member 212 closes the passage 205. When the piston 208 is disposed in the second position, the first stop member 210 closes the passage 203 and the second stop member 212 opens the passage 205.

[0062] In certain implementations, the piston 208 is biased to the closed position. In certain examples, the piston 208 is spring-biased to the closed position. In certain implementations, the piston 208 is moved by a solenoid. In certain examples, the solenoid may receive electrical signals from an electronic controller based on a sensed state of the recirculation flow. For example, the controller may switch the positions of the piston 208 to vent the recirculation flow if a fuel level of the recirculation flow drops below a predetermined level or if a nitrogen (or other gas) level of the recirculation flow rises above a predetermined level. In other examples, the controller may periodically switch the position of the piston 208 at predetermined time intervals while the recirculation system 100 is operating.

[0063] Some example implementations of the disclosure are included in the following aspects:

[0064] Aspect 1. A recirculation system for a fuel cell stack, the recirculation system comprising:

[0065] a fuel cell stack having an inlet and an outlet;

[0066] a purge valve fluidly coupled to the outlet of the fuel cell stack;

[0067] a water separator fluidly coupled to the purge valve;

[0068] a blower having a first inlet configured to receive fluid flow from the water separator, the blower having an outlet configured to direct the fluid flow towards the inlet of the fuel cell stack;

[0069] a valve arrangement configured to transition between an operating mode and a dehumidification mode, the valve arrangement isolating the fuel cell stack inlet when configured in the dehumidification mode and connecting the fuel cell stack inlet to the blower when configured in the operation mode.

[0070] Aspect 2. The recirculation system of aspect 1, further comprising a valve that selectively provides access between a water storage tank of the water separator and the inlet of the fuel cell stack.

[0071] Aspect 3. The recirculation system of aspect 1, wherein the blower includes a pump and an ejector.

[0072] Aspect 4. The recirculation system of aspect 1, wherein the purge valve is directly coupled to the water separator.

[0073] Aspect 5. The recirculation system of aspect 1, wherein a vent channel provides a path for contaminated fluid out of the blower.

[0074] Aspect 6. The recirculation system of aspect 5, wherein the vent channel extends from a gear case.

[0075] Aspect 7. The recirculation system of aspect 5, wherein the vent channel extends from a sealing chamber between a pump and a gear case.

[0076] Aspect 8. The recirculation system of aspect 5, wherein vented fluid from the vent channel, purged fluid from the purge valve, and condensed fluid from a storage tank of the water separator are merged together at a combined purge line.

[0077] Aspect 9. The recirculation system of aspect 8, wherein the vented fluid, the purged fluid, and the condensed fluid are merged together external of the water separator.

[0078] Aspect 10. The recirculation system of aspect 8, wherein the vented fluid, the purged fluid, and the condensed fluid are merged together within the storage tank of the water separator.

[0079] Aspect 11. The recirculation system of aspect 1, wherein the water separator includes a valve arrangement separating a storage tank from a buffer region, the valve arrangement including a float style actuator.

[0080] Aspect 12. A water separator comprising:

[0081] a condensation region configured to transition water vapor to liquid water;

[0082] a buffer region disposed beneath the condensation region to receive the liquid water;

[0083] a valve arrangement disposed in the buffer region, the valve arrangement being configured to selectively open and close a passage to a storage tank, the valve arrangement being configured to open the passage when the buffer region fills to a predetermined level.

[0084] Aspect 13. The water separator of aspect 12, further comprising a baffle arrangement disposed in the condensation region.

[0085] Aspect 14. The water separator of aspect 12, further comprising a housing having a plurality of chambers, wherein the condensation region is defined by a first of the chambers, the buffer region is defined by a second of the chambers, and the storage tank is defined by a third of the chambers.

[0086] Aspect 15. The water separator of aspect 12, wherein the first, second, and third chambers are vertically aligned.

[0087] Aspect 16. The water separator of aspect 12, wherein the first chamber defines an inlet and a gas outlet.

[0088] Aspect 17. The water separator of aspect 12, wherein a porous membrane is disposed between the first and second chambers.

[0089] Aspect 18. The water separator of aspect 12, wherein the valve arrangement includes a valve biased to a closed position.

[0090] Aspect 19. The water separator of aspect 12, wherein the valve arrangement including a lever that pivots based on an amount of liquid water disposed within the buffer region, the lever being configured to move the valve against the bias to an open position when the buffer region fills to a predetermined level.

[0091] Aspect 20. The water separator of aspect 12, wherein the valve carries a seal that blocks an exit of the passage when the valve is biased to the closed position, and wherein the seal is offset from the exit to open the passage.

[0092] Having described the preferred aspects and implementations of the present disclosure, modifications and equivalents of the disclosed concepts may readily occur to one skilled in the art. However, it is intended that such modifications and equivalents be included within the scope of the claims which are appended hereto.

Claims

What is claimed is:

1. A recirculation system for a fuel cell stack, the recirculation system comprising: a. a fuel cell stack having an inlet and an outlet; b. a purge valve fluidly coupled to the outlet of the fuel cell stack; c. a water separator fluidly coupled to the purge valve; d. a blower having a first inlet configured to receive fluid flow from the water separator, the blower having an outlet configured to direct the fluid flow towards the inlet of the fuel cell stack; e. a valve arrangement configured to transition between an operating mode and a dehumidification mode, the valve arrangement isolating the fuel cell stack inlet when configured in the dehumidification mode and connecting the fuel cell stack inlet to the blower when configured in the operation mode.

2. The recirculation system of claim 1, further comprising a valve that selectively provides access between a water storage tank of the water separator and the inlet of the fuel cell stack.

3. The recirculation system of claim 1, wherein the blower includes a pump and an ejector.

4. The recirculation system of claim 1, wherein the purge valve is directly coupled to the water separator.

5. The recirculation system of claim 1, wherein a vent channel provides a path for contaminated fluid out of the blower.

6. The recirculation system of claim 5, wherein the vent channel extends from a gear case.

7. The recirculation system of claim 5, wherein the vent channel extends from a sealing chamber between a pump and a gear case.

8. The recirculation system of claim 5, wherein vented fluid from the vent channel, purged fluid from the purge valve, and condensed fluid from a storage tank of the water separator are merged together at a combined purge line.

9. The recirculation system of claim 8, wherein the vented fluid, the purged fluid, and the condensed fluid are merged together external of the water separator.

10. The recirculation system of claim 8, wherein the vented fluid, the purged fluid, and the condensed fluid are merged together within the storage tank of the water separator.

11. The recirculation system of claim 1, wherein the water separator includes a valve arrangement separating a storage tank from a buffer region, the valve arrangement including a float style actuator.

12. A water separator comprising: a. a condensation region configured to transition water vapor to liquid water; b. a buffer region disposed beneath the condensation region to receive the liquid water; c. a valve arrangement disposed in the buffer region, the valve arrangement being configured to selectively open and close a passage to a storage tank, the valve arrangement being configured to open the passage when the buffer region fills to a predetermined level.

13. The water separator of claim 12, further comprising a baffle arrangement disposed in the condensation region.

14. The water separator of claim 12, further comprising a housing having a plurality of chambers, wherein the condensation region is defined by a first of the chambers, the buffer region is defined by a second of the chambers, and the storage tank is defined by a third of the chambers.

15. The water separator of claim 12, wherein the first, second, and third chambers are vertically aligned.

16. The water separator of claim 12, wherein the first chamber defines an inlet and a gas outlet.

17. The water separator of claim 12, wherein a porous membrane is disposed between the first and second chambers.

18. The water separator of claim 12, wherein the valve arrangement includes a valve biased to a closed position.

19. The water separator of claim 12, wherein the valve arrangement including a lever that pivots based on an amount of liquid water disposed within the buffer region, the lever being configured to move the valve against the bias to an open position when the buffer region fills to a predetermined level.

20. The water separator of claim 12, wherein the valve carries a seal that blocks an exit of the passage when the valve is biased to the closed position, and wherein the seal is offset from the exit to open the passage.

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