Compressor with hydration system

Abstract

An air handling sub-system within a fuel cell system is configured to condition the air for the fuel cell. The air handling sub-system conditions the air by dosing water into the air at or near the compressor. Liquid water is introduced into the compressor to form a thin film. The compressor comprises a body defining an interior cavity extending between an inlet and an outlet; a rotor disposed within the interior cavity and a hydration system including at least one hydration passage extending through the body to deliver the liquid water to the interior cavity.

Description

COMPRESSOR WITH HYDRATION SYSTEMGOVERNMENT LICENSE RIGHTS

[0001] This invention was made with government support under DE-EE0009618 awarded by the U.S. Department of Energy. The government has certain rights in the invention.CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 558,771, filed February 28, 2024, and titled “Compressor with Hydration System”; U.S. Provisional Application No. 63 / 640,544, filed April 30, 2024, and titled “Liquid Water Detection in Fuel Cell System”; and U.S. Provisional Application No. 63 / 658,226, filed June 10, 2024, and titled “Humidity Control in Fuel Cell System”, the disclosures of all of which are hereby incorporated herein by reference in their entirety.BACKGROUND

[0003] A fuel cell system can provide power to certain types of vehicles (e.g., electric vehicles, hybrid-electric vehicles, etc.). The fuel cell system includes a fuel cell stack at which hydrogen and oxygen (e.g., air) are combined across a membrane. When combined, these elements generate electricity and water. The fuel cell system typically includes a first circulation system to supply oxygen / air to the fuel cell stack and a second circulation system to supply hydrogen to the fuel cell stack. The first circulation system includes a compressor (e.g., a positive displacement compressor) to direct the air through the first circulation system.SUMMARY

[0004] Aspects of the disclosure are directed to conditioning a fluid (e.g., air or oxygen) within a compressor (e.g., a positive displacement compressor) to facilitate use of the fluid at a fuel cell stack. In certain implementations, the compressor pressurizes the fluid. In certain implementations, the fluid is hydrated at the compressor. In certain implementations, the fluid is heated at the compressor.

[0005] In accordance with certain aspects of the disclosure, the compressor includes a hydration system including one or more hydration passages leading into an interior of the compressor. In some implementations, the hydration passages lead to interior surfaces of the rotor bores. In certain examples, the water is smeared over the interior surface of a rotor bore, resulting in a thin film to facilitate evaporation. In other implementations, the hydrationpassages lead to an axial end of the rotor bores. In certain examples, a low pressure region is disposed at the axial end of the rotor bore to facilitate directing the water into the compressor.

[0006] In accordance with certain aspects of the disclosure, the water introduced into the compressor is at least partially obtained from water exhausted from an outlet of the fuel cell stack. For example, a water trap may be disposed downstream of the fuel cell stack outlet. The water trap may direct all or some of the exhausted water towards a water reservoir fluidly coupled to the hydration system.

[0007] In accordance with certain aspects of the disclosure, the evaporation of the water within the compressor cools the fluid (e.g., air or oxygen) passing through the compressor. In certain implementations, heated coolant is circulated through or along the compressor to counteract this cooling. In certain examples, the transfer of heat from the heated coolant facilitates evaporation of the water within the compressor. In certain examples, the transfer of heat from the heated coolant heats the fluid passing through the compressor to be usable within the fuel cell stack. In certain implementations, the compressor and the fuel cell stack share a coolant circuit. In such implementations, the heated coolant from the fuel cell stack is passed through the compressor before being directed back to a coolant radiator of the coolant circuit. Such routing also assists in reducing the temperature of the heated coolant, thereby increasing the efficiency of the fuel cell coolant system.

[0008] Other aspects of the disclosure are directed to the detection of liquid water within a fuel cell air handling system. The presence of liquid water at a specific point within the system is determined using at least two temperature readings — including one temperature reading at the specific point. In certain implementations, at least three temperature readings are used to enhance accuracy. In certain implementations, two or more temperature readings subsequent to the temperature reading at the specific point can be used to calibrate the detection process.

[0009] In some implementations, liquid water is being introduced into the system to humidify the fluid (e.g., air or oxygen) directed to the fuel cell. For example, water may be dosed into the fluid stream at a compressor upstream of the fuel cell. In such implementations, the dosing of the liquid water may be adjusted based on whether liquid water is detected at a specific point downstream of the compressor and upstream of the fuel cell.

[0010] In other implementations, moisture is being removed from the fuel cell system (e.g., after parking the vehicle). For example, the moisture can be removed by operating the compressor without dosing the liquid water or otherwise introducing moisture into the system.In certain such implementations, the compressor may be run until liquid water is not detected at a specific point (e.g., a location downstream of the fuel cell).

[0011] Aspects of the disclosure are directed to the detection of liquid water within a fuel cell air handling system.

[0012] In some implementations, liquid water is being introduced into the system to humidify the fluid (e.g., air or oxygen) directed to the fuel cell. For example, water may be injected into the fluid stream of a compressor upstream of the fuel cell at a predetermined dose rate. In such implementations, the dosing of the liquid water may be adjusted based on the estimated relative humidity of the fuel cell or the conduit extending between the compressor and the fuel cell.

[0013] In other implementations, moisture is being removed from the fuel cell system (e.g., after parking the vehicle). For example, the moisture can be removed by operating the compressor without dosing the liquid water or otherwise introducing moisture into the system. In certain such implementations, the compressor may be run for a predetermined period of time or until liquid water is no longer detected within the system.

[0014] 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

[0015] 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:

[0016] FIG. l is a schematic diagram of a portion of an example fuel cell system including a fuel cell, a compressor, an optional coolant circuit, and an optional water reservoir configured in accordance with the principles of the present disclosure;

[0017] FIG. 2 is a perspective view of a first example compressor suitable for use in the fuel cell system of FIG. 1, the first compressor having a first type of hydration system;

[0018] FIG. 3 is a perspective view of a transverse cross-section of the compressor of FIG. 2 taken along the 3-3 lines, the rotors having been removed for ease in viewing the interior of the compressor;

[0019] FIG. 4 shows the rotors disposed within the compressor of FIG. 3;

[0020] FIG. 5 is a perspective view of a second example compressor suitable for use in the fuel cell system of FIG. 1, the second compressor having a second type of hydration system;

[0021] FIG. 6 is a perspective view of a longitudinal cross-section of the compressor of FIG. 5 taken along the 6-6 lines, the rotors having been removed for ease in viewing the interior of the compressor; and

[0022] FIG. 7 shows the rotors disposed within the compressor of FIG. 6.

[0023] FIG. 8 shows inserts disposed within an example compressor to assist in spreading out liquid water being dosed.

[0024] FIG. 9 is a perspective view of an example insert suitable for use in the compressor of FIG. 8.

[0025] FIG. 10 is a schematic diagram of a portion of another example fuel cell system including a self-hydrating fuel cell, a compressor, and a doser managed by a controller configured in accordance with the principles of the present disclosure.

[0026] FIG. 11 is a flow chart illustrating an example doser management process.

[0027] FIG. 12 is a schematic diagram of a portion of an example fuel cell system including a fuel cell, a compressor, an optional coolant circuit, and an optional water reservoir configured in accordance with the principles of the present disclosure.

[0028] FIG. 13 is a flowchart illustrating an example humidification process suitable for use with the fuel cell system of FIG. 12.

[0029] FIG. 14 is a flowchart illustrating an example dehumidification process suitable for use with the fuel cell system of FIG. 12.

[0030] FIG. 15 is a flowchart illustrating a first example detection process suitable for use in implementing a detection step of either the humidification process of FIG. 13 or the dehumidification process of FIG. 14.

[0031] FIG. 16 illustrates a first example implementation of a water separation feature disposed between two temperature sensors suitable for use in implementing the detection process of FIG. 15.

[0032] FIG. 17 illustrates disposing a temperature sensor at a bottom of a conduit.

[0033] FIG. 18 illustrates an example conduit disposed between the compressor and the fuel cell of FIG. 12 with example temperature sensors and water separation features disposed along the same in accordance with another configuration.

[0034] FIG. 19 illustrates an example conduit disposed between the compressor and the fuel cell of FIG. 12 with example temperature sensors and water separation features disposedalong the same in accordance with another configuration allowing for the implementation of the second detection process of FIG. 20.

[0035] FIG. 20 is a flowchart illustrating a second example detection process suitable for use in implementing a detection step of either the humidification process of FIG. 13 or the dehumidification process of FIG. 14.

[0036] FIG. 21 illustrates a graph plotting temperature readings against the physical position of the temperature sensors for a system in which heat is lost between the compressor and the fuel cell.

[0037] FIG. 22 illustrates a graph plotting temperature readings against the physical position of the temperature sensors for a system in which heat is gained between the compressor and the fuel cell.

[0038] FIG. 23 shows an example water injection control system and various sensors disposed along the cathode side of the fuel cell system of FIG. 12.

[0039] FIG. 24 is a flowchart illustrating a humidification process by which the cathode side of the fuel cell system of FIGS. 12 and 23 can be water dosed.

[0040] FIG. 25 is a schematic block diagram of an example virtual relative humidity sensor.

[0041] FIG. 26 is a flowchart illustrating an example estimation process by which the relative humidity within the fuel cell system is determined.

[0042] FIG. 27 shows the mapping from a relative humidity column vector to an absolute humidity column vector.

[0043] FIG. 28 is a flowchart showing a dehumidification process for the cathode side of the fuel cell system of FIGS. 12 and 23.DETAILED DESCRIPTION

[0044] 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.

[0045] An air handling portion of an example fuel cell system 100, 400 includes a fuel cell 102, 402 for providing power to a vehicle (e.g., to an electric or hybrid electric vehicle). The fuel cell 102, 402 has a first inlet 104, 404 at which a first fluid (e.g., oxygen) is received, a second inlet 106, 406 at which a second fluid (e.g., hydrogen) is received, and an outlet 108, 408 at which output fluid (e.g., oxygen, water vapor, liquid water, trace amounts of hydrogen,etc.) is directed. In certain examples, at least some of the output fluid is directed towards a pressure valve 110.

[0046] In certain implementations, the first fluid is supplied to the first inlet 104 using a compressor 112. The compressor 112 includes two rotors power by a motor 114 that direct the first fluid from an inlet 142 of the compressor 112 to an outlet 144 of the compressor 112. A filter 116 (e.g., an air filter) feeds the inlet 142 of the compressor 112. The first fluid is directed from the outlet 144 of the compressor 112 to the first inlet 104 of the fuel cell 102.

[0047] In certain implementations, the fuel cell 102 is cooled using a cooling circuit 118. The cooling circuit 118 includes a coolant radiator 120 that reduces the temperature of coolant running therethrough. In certain implementations, a motor 128 powers a fan or other vent to blow air or other fluid over the radiator 120 to cool the coolant flowing therethrough. A coolant pump 122 circulates the coolant through the cooling circuit 118 so that cooled coolant flows from the radiator 120 to the fuel cell 102 and heated coolant flows from the fuel cell 102 back towards the radiator 120. In certain examples, the coolant pump 122 is driven by a motor 124. In certain implementations, a flow control valve 126 manages flow through the coolant circuit 118.

[0048] In accordance with certain aspects of the disclosure, the coolant circuit 118 can be used to heat the compressor 112 as well as cool the fuel cell 102. In certain examples, the temperature of the heated coolant after leaving the fuel cell 102 is higher than the temperature within the compressor 112 during hydration of the first fluid as will be described in more detail herein. Accordingly, the flow control valve 126 may direct heated coolant from the fuel cell 102 to the compressor 112 upstream of the coolant radiator 120. In such cases, the compressor 112 assists the coolant radiator 120 in removing heat introduced into the coolant from the fuel cell 102, thereby reducing thermal load on the coolant radiator 120.

[0049] In accordance with certain aspects of the disclosure, the first fluid being directed through the compressor 112, 412 can be hydrated using water expelled by the fuel cell 102, 402. For example, a water trap 130 or water separator 430 can be disposed downstream of the output 108, 408 of the fuel cell 102, 402. In certain examples, the water trap 130 or water separator 430 directs at least some of the water to a water reservoir 132, 432. In an example, a flow control valve 134 selectively allows flow of the water from the water reservoir 132, 432 to the compressor 112 or a doser 450. At the compressor or doser, the water is introduced into the first fluid as will be discussed in more detail herein. Accordingly, the first fluid assists in supplying the fuel cell 102, 402 with humidity.

[0050] In some implementations, the doser 450 includes the hydration system 170, 220, 320 described above with respect to FIGS. 2-9. In other implementations, however, the doser 450 may include a nozzle that injects aerosolized water into the first fluid. In some examples, the nozzle may be disposed at the compressor 412. In other examples, however, the nozzle may be disposed upstream of the compressor 412 (e.g., see FIG. 10). In still other examples, the nozzle may be disposed downstream of the compressor 412.

[0051] In accordance with certain aspects of the disclosure, the compressor 112 is configured to condition the first fluid to enhance performance of the fuel cell 102. In certain implementations, the compressor 112 is configured to pressurize the first fluid to a first predetermined pressure threshold suitable for normal operation of the fuel cell 102. In certain implementations, the compressor 112 is configured to hydrate the first fluid to a predetermined humidity threshold suitable for normal operation of the fuel cell 102. In certain examples, the compressor 112 is configured to hydrate the first fluid to about 60% - 80% relative humidity measured at the outlet of the compressor 112. In certain implementations, the compressor 112 is configured to manage the temperature of the first fluid to be above a predetermined temperature threshold suitable for normal operation of the fuel cell 102.

[0052] In certain implementations, the predetermined temperature threshold is about 60 degrees Celsius. In certain examples, the predetermined temperature threshold ranges between 60-80 degrees Celsius. In certain examples, evaporation of the water within the compressor 112 reduces the temperature within the compressor 112 and / or the temperature of the first fluid passing through the compressor to less than 60 degrees Celsius. For example, the temperature of the compressor 112 and / or the first fluid passing through the compressor 112 may be between 30-60 degrees Celsius. In certain examples, the temperature of the heated coolant leaving the fuel cell stack is more than 80 degrees Celsius. In certain examples, the temperature of the heated coolant leaving the fuel cell stack is more than 85 degrees Celsius.

[0053] FIGS. 2-4 illustrate a first example implementation 150 of a compressor 112 configured in accordance with the principles of the present disclosure is shown. FIGS. 5-7 illustrate a second example implementation 200 of a compressor 112 configured in accordance with the principles of the present disclosure is shown. FIGS. 8-10 illustrate a third example implementation 300 of a compressor 112 including an insert 350 configured in accordance with the principles of the present disclosure is shown.

[0054] The compressor 150, 200, 300 includes a body 152, 202, 302 extending between the inlet 142 and the outlet 144. In certain implementations, the body 152, 202, 302 extends along a longitudinal axis LA between a first end 151, 201 of the body 152, 202, 302 and anopposite second end 153, 203 of the body 152, 202. In certain implementations, the inlet 142 is disposed at the first end 151, 201 of the body 152, 202, 302 and the outlet 144 is disposed at the second end 153, 203 of the body 152, 202, 302.

[0055] In certain implementations, the inlet 142 is angled relative to the outlet 144. In the example shown, the inlet 142 is located orthogonal to the outlet 144 (e.g., see FIG. 5). In other examples, however, the inlet 142 can be disposed at a different angle relative to the outlet 144. In still other examples, the inlet 142 can be aligned with the outlet 144 along the longitudinal axis LA. The compressor body 152, 202, 302 defines an interior cavity 154, 204, 304 in which one or more rotors 156, 206, 306 are disposed. In certain examples, the interior cavity 154, 204, 304 extends along the longitudinal axis LA of the compressor housing 152, 202, 302.

[0056] The one or more rotors 156, 206, 306 are each configured to rotate about a respective rotation axis within a respective rotor bore at the interior cavity 154, 204, 304. In certain examples, each rotation axis is parallel to the longitudinal axis LA. In certain implementations, each rotor 156, 206, 306 has lobes that extend outwardly from a hub towards the inner surface 155, 355 of the interior cavity 154, 204, 304. The lobes define the paths through the interior cavity 154, 204, 304. In the example shown, the rotors 156, 206, 306 are helical rotors having twisting lobes. In certain implementations, a pair of rotors 156a- 156b, 206a-206b, 306a-306b are disposed within the interior cavity 154, 204, 304. In certain examples, the rotors 156a-156b, 206a-206b, 306a-306b rotate in opposite directions. For example, the rotor 156a, 206a, 306a may rotate counter-clockwise while the rotor 156b, 206b, 306b rotates clockwise.

[0057] In some implementations, tips of the rotor lobes glide over the inner surface 155, 355 of the interior cavity 154, 204, 304, thereby forming fluid channels for the first fluid between adjacent lobes of the rotors 156, 206, 306. Rotation of the one or more rotors 156, 206, 306 directs fluid (e.g., air or oxygen) from the inlet 142, along the fluid channels, to the outlet 144. The fluid channels move within the cavity 154, 204, 304 as the one or more rotors 156, 206, 306 rotate within the rotor bores. In certain implementations, the rotors 156, 206, 306 of the compressor 150, 200, 300 increase the pressure of the fluid to at least a predetermined threshold.

[0058] In certain implementations, the compressor body 152, 202, 302 defines a hydration system 170, 220, 320 fluidly coupled to the water reservoir 132 via the flow control valve 134. Integrating the humidification process of the first fluid into the compressor reduces the overall number of components required in the fuel cell system 100. One or more hydration passages 172, 222, 322 lead into the interior cavity 154, 204, 304 of the compressor 150, 200, 300. Incertain implementations, the hydration system 170, 220, 320 introduces the water in liquid form. In certain implementations, the water is introduced at a sufficiently low velocity that the water initially remains liquid as the water is smeared by the tips of the rotors 156, 206, 306 along an inner surface 155, 355 of the interior cavity 154, 204, 304, thereby forming a thin film along the inner surface 155, 355. Accordingly, the water is introduced onto one or more surfaces of the compressor body 152, 202, 302 instead of directly into the fluid stream.

[0059] In certain implementations, the heat of the compression of the first fluid within the compressor 150, 200, 300 vaporizes the thin film of water, thereby enhancing the humidity of the first fluid. In certain examples, friction of the rotor tips sliding over the thin film of water increases the temperature of the water, thereby enhancing or assisting vaporization of the water. By initially introducing the water in liquid form and spreading the liquid along the inner surface 155, 305 of the cavity 154, 204, 304, the water is vaporized within the compressor cavity 154, 204, 304 and introduced into the fluid stream of the first fluid from over a larger surface area compared to introduction through a nozzle, thereby enhancing diffusion of the vaporized water into the first fluid passing through the compressor body 152, 202, 302.

[0060] In some implementations, the hydration system 170, 220, 320 may feed water into the rotor cavity 154, 204, 304 (e.g., using a pump or other driver). In other implementations, however, a negative pressure generated through movement of the rotors 156, 206, 306 may draw the water into the rotor cavity 154, 204, 304, thereby reducing or eliminating a need for a driver. In some implementations, the hydration system 170, 220, 320 may draw or be fed fresh water from a fresh water reservoir. In other implementations, however, the hydration system 170, 220, 320 may draw or be fed waste water exhausted by the fuel cell stack. For example, as shown in FIG. 1, a water trap 130 may direct at least some of the water exhausted from the fuel cell stack to a reservoir 132. In certain implementations, the reservoir may store a mixture of both fresh and exhausted water.

[0061] In some implementations, the hydration passages 172 lead into the interior cavity 154 at locations extending along the longitudinal axis LA of the compressor 150. For example, the hydration passages 172 may lead to outlet ports 174 disposed at the inner surface 155 of the rotor bores (e.g., see FIG. 4). In other implementations, the hydration passages 222 lead into an axial end of the interior cavity 204 (e.g., see FIG. 6). In certain implementations, the water dosing within the compressor 112 introduces water to fill the clearance between the rotor tips and the inner surface of the cavity 154, 204, 304, thereby inhibiting fluid leaks between the rotors 156, 206, 306 and the cavity body.

[0062] In FIGS. 2-4, the hydration passages 172 include a trunk passage 172a and a plurality of branch passages 172b. In certain implementations, the trunk passage 172 extends parallel with the longitudinal axis LA of the compressor housing 152. Each of the branch passages 172b leads from the trunk passage 172a to the outlet ports 174 at the interior cavity 154. In certain examples, the outlet ports 174 are disposed in one or more rows along the longitudinal axis LA. In certain implementations, the outlet ports 174 are disposed to output directly into fluid channels formed by the rotors 156. Such locations of the outlet ports 174 result in the rotor lobes smearing the water against the inner surface 155 of the rotor bores as the rotors 156 rotate. Such smearing creates a thin film of the water, which aids the water in evaporating more quickly. For example, tips of the rotors 156 may glide over the inner surface, thereby heating the film of water to enhance evaporation of the water. In certain examples, a pump, injector, or other such device can be used to direct the water into the hydration passages 172.

[0063] In certain implementations, the distribution of the water over the inner surface 155 of the rotor bores may be facilitated by the presence of a coating over at least portions of the inner surface 155. In certain examples, the coating is a hydrophilic coating. Such a coating would help the water to migrate along the inner surface 155, which exposes more water to the rotors 156 and / or to the heat obtained through the inner surface 155 from the heated coolant passing through or around the compressor 112.

[0064] In FIGS. 5-7, the hydration passages 222 extend through an outer wall of the compressor at the first end 151. In the example shown, two hydration passages 222 extend through the outer wall. In other examples, however, a greater or lesser number of passages 222 (e.g., one, three, four, ten, etc.) can be provided through the outer wall. In certain implementations, the hydration passages 222 lead to a region within the cavity 204 that is not fully exposed to the inlet 142. Accordingly, the region can be at sub-atmospheric conditions or low pressure. In some examples, the low pressure of the region may draw the water into the compressor 200 without the use of a pump, injector, or other such device. In other examples, a pump, injector, or other such device may assist in directing the water into the hydration passages 222.

[0065] In FIGS. 8-10, the hydration passages 322 extend through the compressor body 302 and leads to one or more inlets into the interior cavity 304. In certain implementations, one or more inserts 350 are disposed within the interior cavity 304. As shown in FIGS. 9 and 10, each insert 350 includes a contoured wall 352 supported by sidewalls 354. The sidewalls 354 space the contoured wall 352 radially inwardly towards the rotors 306 so that the contouredwall 352 defines the inner surface 355 of the interior cavity 304. The sidewalls 354 and contoured surface 352 cooperate to define a pocket 356 disposed between the inner surface 355 of the interior cavity 304 and an inner surface 359 of the compressor body 302.

[0066] In certain examples, the contoured wall 352 defines one or more apertures 358 extending therethrough between the pocket 356 and the inner surface 355. In the example shown, the apertures 358 are distributed over a majority of the contoured wall 352. In other examples, however, the apertures 358 may have other configurations. For example, in certain implementations, the apertures 358 may be distributed over less than a majority of the contoured wall 352. In the example shown, the apertures 358 are disposed in a series of rows. In other examples, the apertures 358 may be configured into groups, shapes, or other designs.

[0067] The hydration passages 322 of the hydration system 320 lead to the pocket 356 of each insert 350. In use, liquid water flows from the hydration passages 322, within the pocket 356, and then through the apertures 358 to the inner surface 355. The rotors 306 are sized so that tips of the rotors 306 glide over the inner surface 355, thereby smearing the liquid water into a thin film. In certain examples, the liquid water flowing through the apertures 358 may enhance sealing between the rotor tips and the interior surface 355, thereby reducing leaks along the fluid stream pathway.

[0068] In certain implementations, the contoured wall 352 has a hydrophilic coating along at least the inner surface 355. In certain examples, the hydrophilic coating may be disposed along both the inner surface 355 and outer surface of the contoured wall 352. As the term is used herein, a “hydrophilic coating” is a coating having a tendency to mix with, dissolve in, or be wetted by water. Such a hydrophilic coating would enhance the ability of the liquid water to spread out over the contoured wall 352.

[0069] In some examples, the contoured walls 352 of the inserts 350 extend over a majority of the surface area of the interior cavity 304 (e.g., see FIG. 8). For example, each contoured wall 352 may extend along at least a majority of a depth of the interior cavity. In an example, each contoured wall 352 may extend along at least a quarter of a circumference of the interior cavity 304. In another example, the interior cavity 304 is formed from two joined rotor bores and each rotor bore receives an insert 350. In some such examples, each contoured wall 352 may extend along a majority of the circumference of the respective rotor bore (e.g., see FIG. 8).

[0070] In certain implementations, the rotors 156, 206, 306 may have a hydrophilic coating (e.g., a nanocoating). Such a hydrophilic coating would enhance the ability of the liquid water introduced by the hydration system 170, 320, 220 to spread out onto and / or stickto an exterior surface of the rotors 156, 206, 306. Accordingly, the liquid water would form a thin film along the exterior surfaces of the rotors 156, 206, 306. Such a thin film on the rotors 156, 206, 306 would enhance the sealing between the rotors 156, 206, 306 and the cavity interior surface 155, 355, thereby reducing leakage along the fluid stream path. In certain examples, causing the liquid water to stick to the rotors (unless and until smeared onto the inner surface 155, 355 and / or vaporized) inhibits water droplets (unvaporized drops of water) from being carried by the fluid stream of the first fluid towards the fuel cell 102. In certain examples, the stuck water would eventually evaporate into the fluid stream from the surfaces of the rotors 156, 206, 306, thereby enhancing the surface area from which the evaporation stems to better diffuse the vaporized water into the fluid stream.

[0071] Water evaporation is an endothermic reaction. Accordingly, in certain implementations, the phase change of the water within the compressor 112, 150, 200, 300 may cool the first fluid passing through the compressor 112, 150, 200, 300. Accordingly, the water dosing within the compressor allows for a smaller package size for the compressor 112, 150, 200, 300 as the compressor 112, 150, 200, 300 does not need to accommodate as much thermal growth of the first fluid.

[0072] In certain implementations, heating of the first fluid may be provided at the compressor 112 using the coolant circuit 118. In certain examples, the heat may assist in water evaporation, thereby increasing hydration of the first fluid. In certain examples, the heat may bring the temperature of the first fluid into an appropriate range for use at the fuel cell 102. In certain implementations, the compressor body 152, 202, 302 defines a coolant pathway 160, 210 around the interior cavity 154, 204, 304. In some examples, the coolant pathway 160, 210 defines an annular cavity partially surrounding an outer wall 158, 208 of the interior cavity 154, 204, 304. In other examples, the coolant pathway 160, 210 defines a winding channel extending around and / or along the outer wall 158, 208 of the interior cavity 154, 204, 304.

[0073] In some implementations, the humidity at the fuel cell 102 is managed through the water dosage at the compressor 112. In other implementations, however, the fuel cell 402 is a self-hydrating fuel cell that manages its own humidity (e.g., see FIG. 10). In such implementations, water (e.g., vaporized water, liquid water, etc.) may still be introduced into the first fluid by a doser 450 at or near the compressor 412 to manage a temperature of the first fluid instead of a humidity level. In certain examples, the temperature of the first fluid may be tracked at the fuel cell 402. Based on a monitored temperature at the inlet of the compressor 412 and / or the fuel cell 402, the amount of water introduced into the first fluid by a doser 450 may be increased or decreased. For example, a controller 480 managing the doser 450 isconfigured to increase the amount of water introduced by the doser 450 to lower the temperature of the first fluid. Because the dosing is controlled based on temperature, the humidity of the first fluid leaving the compressor 412 may be less than a humidity required for operation of a traditional fuel cell. For example, the humidity of the first fluid leaving the compressor 412 may be 70-90% of the operating relative humidity of the fuel cell 402. Accordingly, in certain implementations, the fuel cell 402 is a self-hydrating fuel cell (e.g., a fuel cell with a self-humidifying membrane).

[0074] In certain implementations, dosing of the first fluid may be ceased when an ambient temperature (e.g., a temperature outside the fuel cell system 400, such as outside a vehicle powered by the fuel cell system 400) is below a predetermined threshold T1. When the ambient temperature is below the threshold Tl, dosing at the compressor 412 ceases and the humidity at the fuel cell 402 is directly managed by the fuel cell 402 (e.g., the self-hydrating fuel cell 402). When the ambient temperature is at or above the threshold Tl, however, dosing is performed at or upstream of the compressor 412 to manage the temperature of the selfhydrating fuel cell 402. In certain examples, the threshold Tl is the freezing point of water (e.g., 0 degrees Celsius). In other examples, however, the threshold Tl can be above or below this temperature (e.g., -2 degrees Celsius, -1 degree Celsius, 1 degree Celsius, 2 degrees Celsius, 5 degrees Celsius, 6 degrees Celsius, or 7 degrees Celsius).

[0075] In certain implementations, the fuel cell system 400 includes a compressor 412 directing the first fluid to the first inlet 404 of the fuel cell 402 and an expander 460 receiving output fluid from the outlet 408. Examples of such a fuel cell system 400 are shown and described in WO 2022-242915, the disclosure of which is hereby incorporated herein by reference in its entirety. In certain examples, a water separator 430 may be disposed between the fuel cell outlet 408 and the expander 460. Accordingly, the first fluid being directed through the compressor 112 can be dosed using water expelled by the fuel cell 102. For example, the expelled water may be separated out from the output fluid at the water separator 430 and directed to the water reservoir 432.

[0076] As noted above, dosing of the first fluid may be ceased based on the ambient temperature. In certain implementations, the water reservoir 432, the doser 450, and / or conduits leading therebetween may be drained when the ambient temperature drops below the threshold Tl . Of course, a different threshold also may be used for determining when to drain the water reservoir 432, the doser 450, and / or conduits therebetween.

[0077] FIG. 11 illustrates an example doser management process 490 by which dosing of the first fluid may be implemented. At a first step, an ambient temperature A is checked. Atdecision module 492, the ambient temperature A is compared to the first threshold Tl. If the ambient temperature A is below the first threshold Tl, then one or more components of the dosing sub-system (e.g., the water reservoir 432, the doser 450, conduits therebetween) are drained. If the ambient temperature A is at or above the first threshold Tl, however, then a temperature T of the first fluid is checked at a step 493.

[0078] Decision module 494 compares the temperature of the first fluid to a second predetermined threshold T2. If the temperature T of the first fluid is above the second threshold T2, then the controller 480 causes the doser 450 to introduce water into the first fluid at step 495. In certain examples, the second threshold T2 is the target temperature of the fuel cell 402. In certain examples, the second threshold T2 is between 60 degrees Celsius and 100 degrees Celsius. In certain examples, the second threshold T2 is between 70 degrees Celsius and 90 degrees Celsius. In certain examples, the second threshold is between 75 degrees Celsius and 85 degrees Celsius. In an example, the second threshold is about 85 degrees Celsius.

[0079] Referring now to FIGS. 12-22, another example fuel cell system 500 includes a fuel cell 502 for providing power to a vehicle (e.g., to an electric or hybrid electric vehicle). The fuel cell 502 has a first inlet 504 at which a first fluid (e.g., oxygen or air) is received and a second inlet 506 at which a second fluid (e.g., hydrogen) is received. The fuel cell 502 also has an outlet 508 from which a first output fluid (e.g., air with unreacted oxygen, liquid water, water vapor, etc.) leaves the fuel cell 502 and a second outlet 510 at which a second output fluid (e.g., unreacted hydrogen, etc.) is directed.

[0080] In certain implementations, the first fluid is supplied to the first inlet 504 using a compressor 512. In certain examples, the compressor 512 includes two rotors power by a motor 514 that direct the first fluid from an inlet 513 of the compressor 512 to an outlet 515 of the compressor 512. A filter 516 (e.g., an air filter) feeds the inlet 513 of the compressor 512. The first fluid is directed from the outlet 515 of the compressor 512 towards the first inlet 504 of the fuel cell 502.

[0081] In certain implementations, the fuel cell 502 is cooled using a cooling circuit 518. The cooling circuit 518 includes a coolant radiator 520 that reduces the temperature of coolant running therethrough. In certain implementations, a motor 528 powers a fan or other vent to blow air or other fluid over the radiator 520 to cool the coolant flowing therethrough. A coolant pump 522 circulates the coolant through the cooling circuit 518 so that cooled coolant flows from the radiator 520 to the fuel cell 502 and heated coolant flows from the fuel cell 502 back towards the radiator 520. In certain examples, the coolant pump 522 is driven by a motor 524.

[0082] In certain implementations, moisture is introduced into the fuel cell system 500 upstream of the fuel cell 502. In some implementations, the compressor 512 is configured to condition the first fluid to enhance performance of the fuel cell 502. For example, the air or other fluid passing through the compressor 512 can be dosed with water (e.g., liquid water) to humidify the air before the air reaches the fuel cell 502. In other implementations, moisture can be introduced into air expelled from the compressor 512 at a location downstream of the compressor 512 and upstream of the fuel cell stack 502. In certain implementations, the air or other fluid is humidified to a predetermined humidity threshold suitable for normal operation of the fuel cell 502. In certain examples, the air is humidified to about 60% - 80% relative humidity measured at the outlet of the compressor 512.

[0083] In accordance with certain aspects of the disclosure, the amount of water being added to the system 500 (e.g., being dosed at the compressor 512) is adjusted based on a regulation process, such as humidification process 540 disclosed herein with respect to FIG. 13. For example, the mount of water being dosed into the system 500 can be lowered if liquid water is detected downstream of the compressor 512.

[0084] In accordance with certain aspects of the disclosure, a dehumidification process can be run to remove moisture from the fuel cell system 500 (e.g., when the vehicle is parked, when the vehicle is parked in a low temperature environment, etc.). FIG. 14 illustrates an example dehumidification process 550 by which moisture can be removed from the fuel cell system 500.

[0085] FIG. 13 is a flowchart illustrating an example humidification process 540 for a fuel cell system 100, 500. The humidification process 540 doses water (e.g., liquid water, steam, etc.) into a fluid stream directed towards the fuel cell 102, 502. In some examples, the water (e.g., liquid water, steam, etc.) is injected into an interior of the compressor 112, 512 or into the inlet 142, 513 of the compressor 112, 512. In other examples, the water is injected into a conduit 530 leading from the compressor 112, 512 towards the fuel cell 102, 502.

[0086] At step 544, a detection process 544 is implemented in accordance with the principles of the present disclosure to determine whether liquid water is present in the conduit 530 downstream of the compressor 112, 512. In certain examples, the detection process 544 determines whether liquid water is present in the conduit 530 at a certain distance upstream of the fuel cell 102, 502. An example detection process 544 is shown in FIG. 15, which will be discussed in more detail herein.

[0087] A decision module 546 determines whether or not water was detected. If water was detected, then the humidification process 540 lowers the dose of water being introducedinto the fuel cell system 100, 500 at step 548. For example, less liquid water may be injected into the compressor 112, 512. The humidification process 540 then cycles back to start again. If liquid water is not detected, however, then the humidification process 540 may cycle back to start continue monitoring. In certain examples, the humidification process 540 continues during normal operation of the vehicle.

[0088] FIG. 14 is a flowchart illustrating an example dehumidification process 550 for a fuel cell system 100, 500. The dehumidification process 550 removes moisture (e.g., liquid water, steam, etc.) from the conduit 530 as well as from the fuel cell 102, 502 itself. In certain implementations, the dehumidification process 550 is run when the vehicle is parked or turned off. In certain examples, the dehumidification process 550 is run when the vehicle is parked or turned off in sub-freezing and / or near freezing ambient temperatures.

[0089] The compressor 112, 512 is run without being dosed with water at a dehumidify step 552. As the compressor 112, 512 is running, a detection process is implemented at step 554. In some examples, the detection process determines whether liquid water is present in the conduit 530 upstream of the fuel cell 102, 502. In other examples, the detection process determines whether liquid water is present in a conduit 531 downstream of the first outlet 108, 508 of the fuel cell 102, 502. An example detection process 554 is shown in FIG. 15, which will be discussed in more detail herein.

[0090] A decision module 556 determines whether or not water was detected. If water was detected, then the dehumidification process 550 cycles back to the dehumidify step 552 to continue monitoring. In other words, the dehumidify process continues until water is not detected. If liquid water is not detected, however, then the dehumidification process 550 may terminate. For example, the compressor 112, 512 may stop directing air through the conduit 530 towards the fuel cell 102, 502.

[0091] FIG. 15 is a flowchart illustrating an example detection process 560 suitable for implementing step 544 of the humidification process 540 and / or step 554 of dehumidification process 550. At a first step 562, a first temperature reading is taken by a first sensor 532 (e.g., thermocouple). At a second step 564, a second temperature reading is taken by a second sensor 534. The second sensor 534 is separated from the first sensor 532 by a water separator arrangement 538. In certain implementations, the first and second sensors 532, 534 are disposed in the same conduit 530, 531.

[0092] At a step 566, the first and second temperature readings are compared. In certain implementations, liquid water W is expected to have a lower temperature than the fluid (e.g., oxygen or air) leaving the compressor 112, 512. In certain implementations, liquid water Wcollects on the first sensor 532 and then evaporates. The evaporation of the water W cools the first sensor 532. Accordingly, the detection process 560 determines that liquid water W is present at the first sensor 552 if the first temperature reading is determined to be lower (e.g., cooler) than the second temperature reading. If the first temperature reading is determined to be higher than the second temperature reading, however, then the detection process 560 determines that liquid water is not present.

[0093] In some implementations, when the detection process 560 is being implemented at step 544 of the humidification process 540, the first and second sensors 532, 534 are disposed upstream of the fuel cell 102, 502. In some examples, the first sensor 532 is disposed at the outlet 515 of the compressor 112, 512. In other examples, the first sensor 532 can be disposed downstream of the compressor outlet 515. In other implementations, the first and second sensors 532, 534 can be otherwise disposed within the fuel cell system 100, 500.

[0094] When the detection process 560 is being implemented at step 554 of the dehumidification process 550, the first and second sensors 532, 534 are disposed downstream of the fuel cell 102, 502. In some examples, the first sensor 532 is disposed at the outlet 508 of the fuel cell 102, 502. In other examples, the first sensor 532 can be disposed downstream of the fuel cell outlet 108, 508. In other implementations, the first and second sensors 532, 534 can be otherwise disposed within the fuel cell system 100, 500 (e.g., upstream of the fuel cell 102, 502).

[0095] In certain implementations, the first and second sensors 532, 534 are separated from each other by a water separator 538. FIGS. 16 and 17 illustrate example water separation techniques. In FIG. 16, a conduit 530, 531 carrying the first fluid (e.g., air or oxygen) has an elbow-bend 538A where the downstream portion of the conduit 530, 531 travels in a generally vertical direction. The first temperature sensor 532 is disposed at the conduit 530, 531 upstream of the elbow-bend 538 A and the second temperature sensor 534 is disposed at the conduit 530 downstream of the elbow-bend 538A. In such an implementation, any liquid water is likely to stay in the conduit upstream of the elbow-bend 538 A. Accordingly, the first temperature sensor 532 will read a temperature of the liquid water present in the conduit 530, 531 while the second temperature sensor 534 will read a temperature of the fluid expelled from the compressor 112, 512. In FIG. 17, liquid water W within a conduit 530, 531 is likely to collect at a bottom surface of the conduit 530 based on gravity. In other implementations, a water separator using baffles or other such structures may be disposed between the first and second sensors 532, 534.

[0096] As shown in FIG. 18, additional temperature sensors, such as a third temperature sensor 536, can be introduced into the fuel cell system 100, 500 to enhance accuracy or information collected. For example, if the temperature obtained by the second sensor 534 in FIG. 18 is higher than the temperature obtained by the first sensor 532, then liquid water is determined to be present at sensor 532. On the other hand, if the temperature obtained by the first and second sensors 532, 534 is about the same, but the temperature obtained by the third sensor 536 is higher, then water is determined to be present at the first and second sensors 532, 534. Accordingly, adding additional temperature sensors may aid in determining how much liquid water is present. Further, adding additional sensors may aid in pinpointing where the liquid water is present within the system 100, 500.

[0097] Referring now to FIGS. 19-22, the readings obtained from the second and third sensors 534, 536 can be used to calibrate the readings obtained from the first sensor 532. Using the subsequent sensor readings to calibrate the first reading enhances the accuracy of the detection process in a system where heat is being introduced downstream of the compressor 112, 512 (e.g., through the walls of the conduit 530, 531). FIG. 19 shows a third sensor 536 disposed downstream of the second sensor 534 without a water separator therebetween. However, the first sensor 532 is still separated from the other sensors 534, 536 by a water separator 538.

[0098] In some implementations, the temperature of the fluid expelled from the compressor 512 may be greater than a temperature of a pipe wall of the conduit 530, 531 through which the fluid is directed. In such cases, heat is transferred from the fluid to the pipe wall. Accordingly, the fluid will cool as the fluid moves through the conduit 530, 531. In other implementations, the temperature of the fluid is less than the pipe wall of the conduit 530, 531. In such cases, heat is transferred from the pipe wall to the fluid as the fluid passes along the conduit 530, 531.

[0099] When the sensors 532, 534, 536 are disposed within a predetermined distance of each other (e.g., adjacent ones of the sensors 532, 534, 536 being less than three feet apart, adjacent ones of the sensors 532, 534, 536 being less than two feet apart, adjacent ones of the sensors 532, 534, 536 being less than 1 foot apart, outer sensors 532, 536 being less than three feet apart, outer sensors 532, 536 being less than two feet apart, outer sensors 532, 536 being less than one foot apart, etc.), the relationship between the temperature readings is estimated to be linear.

[0100] FIG. 20 shows a flow chart for an example calibrated detection process 580 using the sensor layout shown in FIG. 19. This calibrated detection process 580 can be used toimplement the detection process 544 in humidification process 540. The calibrated detection process 580 also can be used to implement the detection process 554 in dehumidification process 550. At step 582, a first temperature reading is obtained at the first sensor 532. At step 584, a second temperature reading is obtained at the second sensor 534. At step 586, a third temperature reading is obtained at the third sensor 536.

[0101] At step 588, a first line 596 is plotted based on the temperature readings at the second and third sensors 534, 536. The first line 596 is calculated by plotting a linear relationship between the temperature differences and the physical spacing of the second and third sensors 534, 536 (see FIGS. 21 and 22). Depending on the surrounding environment of the fuel cell system 500, heat may increase, decrease, or remain constant as the fluid travels along the conduits 530. FIG. 21 shows a first line LI plotted for a system in which system temperature decreases as the fluid flows away from the compressor 112, 512. FIG. 22 shows a first line LI plotted for a system in which system temperature increases as the fluid flows away from the compressor 112, 512.

[0102] In some implementations, the first line LI forms a decision line LD that is used in step 592 (see dashed arrow). In other implementations, however, the decision line LD is offset from the first line LI at step 590. In certain implementations, the decision line LD is offset from the first line LI towards a lower temperature. In certain implementations, the decision line LD is offset by at least 0.5 degrees. In certain implementations, the decision line LD is offset by at least 1 degree. In certain implementations, the decision line LD is offset by no more than 5 degrees. In certain implementations, the decision line LD is offset by no more than 3 degrees. In certain implementations, the decision line LD is offset by no more than 2 degrees. In certain implementations, the decision line LD is offset by 1 degree. In certain implementations, the decision line LD is offset by 2 degrees. The offset between decision line LD and the calculated first line LI provides an error band to accommodate uncertainty within the system.

[0103] Step 592 compares the temperature readings obtained by the first sensor 532 to the decision line LD. If a temperature reading obtained at the first sensor 532 is above the decision line LD (e.g., see temperature reading A), then module 594 determines that liquid water is not present at the first sensor 532. However, if the temperature reading obtained at the first sensor 532 is below the decision line LD (e.g., see temperature reading B), then step 594 determines that liquid water is present at the first sensor 532.

[0104] Referring now to FIGS. 23-28, the humidity of the fuel cell system can be monitored as part of a management and control schema for the air handling system of the fuelcell system 100, 500, 600. FIG. 23 illustrates a portion of another example fuel cell system 600 including a compressor arrangement 611 feeding a first inlet 604 of a fuel cell 602. Moisture is introduced into the fuel cell system 600 upstream of the fuel cell 602. For example, the moisture can be introduced at or near the compressor 612 to condition the first fluid to enhance performance of the fuel cell 602. In certain implementations, an injector 640 can dose the air or other fluid passing through the compressor 612 with water (e.g., liquid water) to humidify the air upstream of the compressor before the air reaches the fuel cell 602. In certain implementations, the air or other fluid is humidified to a predetermined humidity threshold suitable for normal operation of the fuel cell 602. In certain examples, the air is humidified to about 60% - 80% relative humidity measured at the outlet of the compressor 612 or at an intermediate location along the conduit 630.

[0105] In some examples, the injector 640 can be disposed upstream of the compressor 612. In other examples, an injector 640 can be disposed within or downstream of the compressor 612 while still upstream of the fuel cell stack 602. For example, the injector 640 can be disposed at the compressor outlet 615. In certain examples, the injector 640 may be one of multiple injectors 640. In certain examples, one injector 640 can be disposed at the compressor inlet 613 while another injector 640 is disposed at the compressor outlet 615. In certain implementations, the injector 640 differs from a traditional humidifier in that a predetermined amount of water can be introduced into the fuel cell system 600 at a predetermined flow rate.

[0106] The amount of water dosed through the injector(s) 640 is dynamically controlled by an injection controller 642. For example, the amount of water being dosed into the system 600 can be lowered if the relative humidity at the fuel cell inlet 604 exceeds a predetermined maximum threshold. Conversely, the amount of water dosed into the system 600 can be raised if the relative humidity at the fuel cell inlet 604 drops below a predetermined minimum threshold. In accordance with aspects of the disclosure, the amount of water being added to the system 600 (e.g., being dosed at the injector 640) is adjusted based on a regulation process, such as humidification process 650 disclosed herein with respect to FIG. 24.

[0107] The humidification process 650 of FIG. 24 includes a first step 652 of injecting water at a first dose rate. The first dose rate may be selected based on a predetermined value associated with the fuel cell size, a measured ambient relative humidity, or other factors. At step 654, the humidification process 650 determines a relative humidity of the fuel cell system 600 (e.g., a relative humidity downstream of the compressor arrangement 611 and at or upstream of the fuel cell inlet 604) using a virtual relative humidity sensor 646. In certainexamples, as shown in FIG. 25, the virtual sensor 646 can be implemented by a processor 682 and memory 684 storing calculation instructions 685, predetermined thresholds 687, and other data 689. The virtual sensor 646 includes one or more sensor interfaces 686 at which one or more physical sensors 660 (e.g., temperature sensors, pressure sensors, ambient relative humidity sensors, flow meters, etc.) communicate data to the virtual relative humidity sensor 646.

[0108] Relative humidity is difficult to directly measure within the system 600 as any humidity sensor would need to function within a high-pressure, high-temperature, and / or humid environment between the compressor 612 and the fuel cell 602. Further, positioning a humidity sensor at the fuel cell outlet 608 or outside the system 600 will provide readings too slowly to dynamically control the relative humidity effectively. Accordingly, relative humidity within the conduit 630 downstream of the compressor 612 and upstream of the fuel cell 602 can be estimated based on other known conditions to dynamically control the water dosing as will be discussed in more detail herein.

[0109] The humidification process 650 then compares the estimated relative humidity to a predetermined range (e.g., maximum and minimum relative humidity thresholds) for the fuel cell 602 at a determination module 656. If the estimated relative humidity is within the range of the predetermined thresholds, then the humidification process 650 cycles back to the first step 652 and continues to dose at the first dose rate. However, if the estimated relative humidity is outside the range of the predetermined thresholds, then the humidification process 650 proceeds to an adjust step 658 at which the dose rate of the injectors 640 (e.g., an upstream injector and / or a downstream injector and / or humidifier) is adjusted based on the estimated relative humidity. In certain implementations, the adjust step 658 is implemented by a proportional-integral-derivative (PID) controller.

[0110] Referring to FIG. 26, a flowchart of an example estimation process 660 by which step 654 of the humidification process 650 can be implemented. The estimation process 660 begins at step 662 in which an actual absolute humidity AH within the fuel cell system 600 (e.g., at the fuel cell inlet 604, downstream of the compressor arrangement 611 and upstream of the fuel cell inlet 604, etc.) is calculated. In certain implementations, the actual absolute humidity AH within the fuel cell system 600 is calculated based on the amount of water contained in the first fluid flowing from the air filter 616 combined with the amount of water introduced by the injector 640.

[0111] Accordingly, a variety of sensors 660 are positioned within the fuel cell system 600 and external of the fuel cell system 600 (e.g., see FIG. 23). For example, a relativehumidity sensor 662 is positioned external of the fuel cell system 600 (e.g., at or upstream of the air filter 616). In certain examples, a pressure sensor 664 is disposed at each of the inlet 613 of the compressor 612 (or otherwise upstream of the compressor 612 and downstream of the air filter 616). In certain examples, a pressure sensor 664 is disposed at the outlet 615 of the compressor 612 (or along the conduit 630 downstream of the compressor 612 and upstream of the fuel cell inlet 604). In certain examples, a temperature sensor 666 (e.g., a thermocouple) is disposed at each of the inlet 613 (or otherwise upstream of the compressor 612 and downstream of the air filter 616). In certain examples, a temperature sensor 666 is disposed at the outlet 615 of the compressor 612 (or along the conduit 630 downstream of the compressor 612 and upstream of the fuel cell inlet 604). As noted in FIG. 24, a flow sensor 668 also is disposed at or near the air filter 616.

[0112] In certain examples, the amount of water contained in the first fluid flowing from the air filter 616 is determined from a measured relative humidity of the ambient air obtained at the relative humidity sensor 662 as well as the measured flow rate of the air entering the fuel cell system 600 obtained at flow rate sensor 668. In certain examples, the amount of water contained in the first fluid is also determined based on the measured temperature and pressure at the compressor inlet 613.

[0113] At step 664 of the estimation process 660, a column vector 674 of absolute humidity is calculated from a column vector 672 of possible relative humidity (e.g., see FIG. 6) in view of a target temperature and pressure at the fuel cell inlet 604. In particular, for each predetermined value RH1, RH2, RH3. . RUN along a vector 672 of possible relative humidity, the virtual relative humidity sensor 646 calculates a corresponding absolute humidity value AB1, AB2, AEG ... ABN that would occur at the fuel cell inlet 604 if the relative humidity at the fuel cell inlet 604 were the corresponding relative humidity value RHI, RH2, RH3. . RHN.

[0114] In certain examples, the predetermined values RHI, RH2, RH3...RHN are determined by stepping through potential relative humidity values between 0 and 600 at a predetermined interval. In an example, a predetermined interval of 5 may result in relative humidity values RHI, RH2, RH3...RHN of 0, 5, 10...600. In another example, a predetermined interval of 10 may result in relative humidity values RHI, RH2, RH3. . .RHN of 0, 10, 20. . .600. In certain examples, the first and last relative humidity values RHI and RHN, respectively, may be set at predetermined values offset from the actual minimum and maximum values of 0 and 600. For example, the first relative humidity value RHI for which an absolute humidity value is calculated may equal 0 plus the predetermined interval or may be stored in memory 684 of the virtual relative humidity sensor 646.

[0115] At step 666, the virtual relative humidity sensor 646 then compares the actual absolute humidity AH determined at step 662 against the absolute humidity values AB1, AB2, AB3...ABN calculated for the column vector 674. The virtual relative humidity sensor 646 then, at step 668, determines the relative humidity value RH1, RH2, RH3...RHN that corresponds with the matching potential absolute humidity value AB1, AB2, AB3. . . ABN. In some examples, the virtual sensor 646 determines the closest match between the actual absolute humidity AH and the potential absolute humidity values AB1, AB2, AB3...ABN. In other examples, the virtual sensor 646 interpolates between the potential absolute humidity values AB1, AB2, AB3. . . ABN to more accurately identify the corresponding relative humidity within the fuel cell system 600.

[0116] In some implementations, the estimation process 660 also includes a step 670 at which the relative humidity of the fuel cell inlet 604 is determined from the relative humidity value identified at step 668. For example, the fuel cell inlet 604 may be configured to condition the first fluid passing through the inlet 604 to reach a predetermined temperature. In some such systems, the relative humidity value determined at step 668 is adjusted based on the predetermined temperature before being returned as the estimate at step 654 of the humidification process. In such implementations, the predetermined range of determination module 656 is based on the minimum and maximum relative humidity values desired at the fuel cell 602.

[0117] In other implementations, the relative humidity value determined at step 668 is returned as the estimate at step 654 of the humidification process. This relative humidity value is an estimate of the relative humidity at or downstream of the compressor outlet 615 before reaching the conditioning of the fuel cell inlet 604. In such systems, the predetermined thresholds against which the estimated relative humidity is compared at determination module 656 would be adjusted based on the measured conditions of the fuel cell system 600 at the location for which the relative humidity was estimated (e.g., at the compressor outlet 615, within the conduit 630, etc.). For example, the desired minimum and maximum relative humidity values for the fuel cell 602 may be adjusted by the measured temperature of the compressor outlet 615 or conduit 630.

[0118] In accordance with certain aspects of the disclosure, a dehumidification process can be run to remove moisture from the fuel cell system 600 (e.g., when the vehicle is parked, when the vehicle is parked in a low temperature environment, etc.). FIG. 28 illustrates an example dehumidification process 690 by which moisture can be removed from the fuel cell system 600. The dehumidification process 690 is initiated at step 692. In some examples, step692 automatically initiates the dehumidification process 690 based on an external temperature of the vehicle (e.g., if the temperature is at, below, or near the freezing point of water). In other examples, step 692 is manually initiated by a user through a user interface (e.g., a button, toggle, touchscreen, or other such interface of the vehicle).

[0119] At step 694, the compressor 612 is run in reverse. In other words, the compressor 612 is operated to pull the first fluid from the conduit 630, through the compressor 612, and out to ambient (e.g., through air filter 616). Water (e.g., liquid water) trapped in the conduit 630 from the water dosing can be sucked through the compressor 612 and purged from the fuel cell system 600.

[0120] In some implementations, the compressor 612 is run in reverse for a predetermined period of time. In other implementations, the fuel cell system 600 includes sensors at the conduit 630 to detect liquid water. In such implementations, the compressor 612 is run in reverse until no liquid water is detected (or the amount of liquid water drops below a predetermined threshold). In certain implementations, the compressor 612 can be cycled between forward and reverse operation during the step 694. The dehumidification process 690 ends at step 698.

[0121] It will be understood that the relative humidity virtual sensor 646 can be utilized in any of the fuel cell systems 100, 500, 600 disclosed herein. In particular, the relative humidity virtual sensor 646 can be used within the air handling sub-system of the fuel cell systems 100, 500, 600.

[0122] Examples of the disclosure may be implemented in accordance with the following aspects of the disclosure:

[0123] Aspect 1. A compressor comprising:

[0124] a body defining an interior cavity extending between an inlet and an outlet;

[0125] a rotor disposed within the interior cavity; and

[0126] a hydration system including at least one hydration passage extending through the body to deliver water to the interior cavity.

[0127] Aspect 2. The compressor of aspect 1, wherein the hydration passage leads to an inner surface of the interior cavity over which lobes of the rotor swipe.

[0128] Aspect 3. The compressor of aspect 1, wherein the hydration passage leads to an axial end of the interior cavity.

[0129] Aspect 4. The compressor of aspect 1, wherein the body defines a coolant passage between the interior cavity and an exterior of the body.

[0130] Aspect 5. A fuel cell system comprising:

[0131] a fuel cell having a first inlet, a second inlet, and an outlet;

[0132] a compressor directing first fluid to the first inlet; and

[0133] a coolant circuit configured to direct coolant to the fuel cell, the coolant circuit also being configured to direct coolant to the compressor.

[0134] Aspect 6. The fuel cell system of aspect 5, further comprising a water trap downstream of the outlet of the fuel cell, the water trap directing water towards the compressor for use in a hydration system of the compressor.

[0135] Aspect 7. A method of dynamically humidifying a hydrogen fuel cell air handling system including a compressor and a fuel cell stack connected together by a pipe arrangement, the method comprising:

[0136] dosing liquid water at the compressor;

[0137] measuring a first temperature reading of an output flow of the compressor at a first location within the pipe arrangement that is at or downstream of an outlet of the compressor;

[0138] routing the output flow through a water separation location within the pipe arrangement downstream of the first location;

[0139] measuring a second temperature reading at a second location within the pipe arrangement, the second location being downstream of the water separation location and being upstream of the fuel cell stack;

[0140] determining that the second temperature is higher than the first temperature by a predetermined amount; and

[0141] reducing the dosing at the compressor.

[0142] Aspect 8. A method of dynamically humidifying a hydrogen fuel cell air handling system including a compressor and a fuel cell stack connected together by a pipe arrangement, the method comprising:

[0143] dosing liquid water at the compressor;

[0144] measuring a first temperature reading of an output flow of the compressor at a first location within the pipe arrangement that is at or downstream of an outlet of the compressor;

[0145] routing the output flow through a water separation location within the pipe arrangement downstream of the first location;

[0146] measuring a second temperature reading at a second location within the pipe arrangement, the second location being downstream of the water separation location and being upstream of the fuel cell stack;

[0147] measuring a third temperature reading at a third location that is downstream of the second location and upstream of the fuel cell stack;

[0148] plotting a difference between the second and third temperature readings against a distance along the pipe arrangement between the second and third locations;

[0149] determining an estimated temperature reading for the first location based on the plotted difference;

[0150] determining the first temperature reading is below the estimated temperature reading; and

[0151] reducing the dosing at the compressor.

[0152] Aspect 9. A method of drying out a fuel cell air handling system including a fuel cell stack, the method comprising:

[0153] cycling air through the fuel cell system without humidifying the air upstream of the fuel cell stack;

[0154] measuring a first temperature of an output flow of the fuel cell stack at a first location that is at or downstream of an outlet of the fuel cell stack;

[0155] routing the output flow through a water separation location downstream of the first location;

[0156] measuring a second temperature of the output flow downstream of the water separation location; and

[0157] continuing to cycle the air through the fuel cell system at least until the second temperature is lower than the first temperature.

[0158] Aspect 10. The method of aspect 9, further comprising:

[0159] measuring a third temperature reading at a third location that is downstream of the second location;

[0160] plotting a difference between the second and third temperature readings against a distance between the second and third locations;

[0161] determining an estimated temperature reading for the first location based on the plotted difference; and

[0162] continuing to cycle the air through the fuel cell system until the first temperature reading is at least as high as the estimated temperature reading.

[0163] Aspect 11. A method of dynamically humidifying a hydrogen fuel cell air handling system including a compressor and a fuel cell stack connected together by a pipe arrangement, the method comprising:

[0164] running a compressor in a forward direction to pull an air stream from ambient through an air inlet towards the compressor;

[0165] injecting water at a flow rate into the air stream downstream of the air inlet;

[0166] estimating a relative humidity at the fuel cell inlet based on a measured ambient relative humidity, a temperature of the compressor inlet, a pressure of the compressor inlet, and the flow rate of the injected water; and

[0167] dynamically adjusting the flow rate of the liquid water to keep the estimated relative humidity within a predetermined range.

[0168] Aspect 12. The method of aspect 11, wherein estimating the relative humidity at the fuel cell inlet comprises determining an actual absolute humidity at the compressor outlet; calculating a column vector of potential absolute humidity values from potential relative humidity values; and determining the potential relative humidity value that corresponds to the potential absolute humidity value that matches the actual absolute humidity value.

[0169] Aspect 13. A method of dehumidifying a compressor of a hydrogen fuel cell air handling system comprising running the compressor in reverse for a predetermined time period to push an air stream from within the fuel cell air handling system through the compressor and towards ambient.

[0170] Aspect 14. A compressor comprising:

[0171] a body defining an interior cavity extending between an inlet and an outlet;

[0172] a rotor disposed within the interior cavity; and

[0173] a hydration system including at least one hydration passage extending through the body to deliver liquid water to the interior cavity.

[0174] Aspect 15. The compressor of aspect 14, wherein the hydration passage leads to an inner surface of the interior cavity over which lobes of the rotor swipe to spread the liquid water in a film.

[0175] Aspect 16. The compressor of aspect 15, wherein the inner surface is defined by a body of the compressor.

[0176] Aspect 17. The compressor of aspect 15, wherein the inner surface is defined by a separate insert , the inner surface defining apertures leading to an inner pocket defined by the insert.

[0177] Aspect 18. The compressor of aspect 14, wherein the hydration passage leads to an axial end of the interior cavity.

[0178] Aspect 19. The compressor of any of aspects 15-18, wherein the inner surface has a hydrophilic coating.

[0179] Aspect 20. The compressor of any of aspects 14-19, wherein the rotor has a hydrophilic coating.

[0180] Aspect 21. The compressor of any of aspects 14-20, wherein the body defines a coolant passage between the interior cavity and an exterior of the body.

[0181] Aspect 22. A fuel cell system comprising:

[0182] a fuel cell having a first inlet, a second inlet, and an outlet;

[0183] a compressor directing first fluid to the first inlet; and

[0184] a coolant circuit configured to direct coolant to the fuel cell, the coolant circuit also being configured to direct coolant to the compressor.

[0185] Aspect 23. The fuel cell system of claim 22, further comprising a water trap downstream of the outlet of the fuel cell, the water trap directing water towards the compressor for use in a hydration system of the compressor.

[0186] Aspect 24. A method of dynamically humidifying a hydrogen fuel cell air handling system including a compressor and a fuel cell stack connected together by a pipe arrangement, the method comprising:

[0187] dosing liquid water at the compressor;

[0188] measuring a first temperature reading of an output flow of the compressor at a first location within the pipe arrangement that is at or downstream of an outlet of the compressor;

[0189] routing the output flow through a water separation location within the pipe arrangement downstream of the first location;

[0190] measuring a second temperature reading at a second location within the pipe arrangement, the second location being downstream of the water separation location and being upstream of the fuel cell stack;

[0191] determining that the second temperature is higher than the first temperature by a predetermined amount; and

[0192] reducing the dosing at the compressor.

[0193] Aspect 25. A method of dynamically humidifying a hydrogen fuel cell air handling system including a compressor and a fuel cell stack connected together by a pipe arrangement, the method comprising:

[0194] dosing liquid water at the compressor;

[0195] measuring a first temperature reading of an output flow of the compressor at a first location within the pipe arrangement that is at or downstream of an outlet of the compressor;

[0196] routing the output flow through a water separation location within the pipe arrangement downstream of the first location;

[0197] measuring a second temperature reading at a second location within the pipe arrangement, the second location being downstream of the water separation location and being upstream of the fuel cell stack;

[0198] measuring a third temperature reading at a third location that is downstream of the second location and upstream of the fuel cell stack;

[0199] plotting a difference between the second and third temperature readings against a distance along the pipe arrangement between the second and third locations;

[0200] determining an estimated temperature reading for the first location based on the plotted difference;

[0201] determining the first temperature reading is below the estimated temperature reading; and

[0202] reducing the dosing at the compressor.

[0203] Aspect 26. A method of drying out a fuel cell air handling system including a fuel cell stack, the method comprising:

[0204] cycling air through the fuel cell system without humidifying the air upstream of the fuel cell stack;

[0205] measuring a first temperature of an output flow of the fuel cell stack at a first location that is at or downstream of an outlet of the fuel cell stack;

[0206] routing the output flow through a water separation location downstream of the first location;

[0207] measuring a second temperature of the output flow downstream of the water separation location; and

[0208] continuing to cycle the air through the fuel cell system at least until the second temperature is lower than the first temperature.

[0209] Aspect 27. The method of claim 26, further comprising:

[0210] measuring a third temperature reading at a third location that is downstream of the second location;

[0211] plotting a difference between the second and third temperature readings against a distance between the second and third locations;

[0212] determining an estimated temperature reading for the first location based on the plotted difference; and

[0213] continuing to cycle the air through the fuel cell system until the first temperature reading is at least as high as the estimated temperature reading.

[0214] Aspect 28. A method of dynamically humidifying a hydrogen fuel cell air handling system including a compressor and a fuel cell stack connected together by a pipe arrangement, the method comprising:

[0215] running a compressor in a forward direction to pull an air stream from ambient through an air inlet towards the compressor;

[0216] injecting water at a flow rate into the air stream downstream of the air inlet;

[0217] estimating a relative humidity at the fuel cell inlet based on a measured ambient relative humidity, a temperature of the compressor inlet, a pressure of the compressor inlet, and the flow rate of the injected water; and

[0218] dynamically adjusting the flow rate of the liquid water to keep the estimated relative humidity within a predetermined range.

[0219] Aspect 29. The method of claim 28, wherein estimating the relative humidity at the fuel cell inlet comprises determining an actual absolute humidity at the compressor outlet; calculating a column vector of potential absolute humidity values from potential relative humidity values; and determining the potential relative humidity value that corresponds to the potential absolute humidity value that matches the actual absolute humidity value.

[0220] Aspect 30. A method of dehumidifying a compressor of a hydrogen fuel cell air handling system comprising running the compressor in reverse for a predetermined time period to push an air stream from within the fuel cell air handling system through the compressor and towards ambient.

[0221] Aspect 31. A method of conditioning a fluid flowing within an air handling system of a fuel cell system, the fuel cell system including a fuel cell and a compressor, the method comprising:

[0222] monitoring a temperature of the fluid;

[0223] increasing a dosing rate of water into the fluid at or upstream of the compressor when the temperature drops below a predetermined threshold; and

[0224] decreasing the dosing rate of water into the fluid when the temperature reaches the predetermined threshold.

[0225] Aspect 32. The method of claim 31, further comprising:

[0226] monitoring an ambient temperature ; and

[0227] draining doser equipment of the air handling system when the ambient temperature drops below a second predetermined threshold, the doser equipment including at least one component of the following components: a water reservoir, a doser, and a conduit.

[0228] Aspect 33. The fuel cell systems and methods of any of claims 22-32, wherein the fuel cell is a self-hydrating fuel cell .

[0229] 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 compressor comprising: a body defining an interior cavity extending between an inlet and an outlet; a rotor disposed within the interior cavity; and a hydration system including at least one hydration passage extending through the body to deliver liquid water to the interior cavity.

2. The compressor of claim 1, wherein the hydration passage leads to an inner surface of the interior cavity over which lobes of the rotor swipe to spread the liquid water in a film.

3. The compressor of claim 2, wherein the inner surface is defined by a body of the compressor.

4. The compressor of claim 2, wherein the inner surface is defined by a separate insert, the inner surface defining apertures leading to an inner pocket defined by the insert.

5. The compressor of claim 1, wherein the hydration passage leads to an axial end of the interior cavity.

6. The compressor of any of claims 2-5, wherein the inner surface has a hydrophilic coating.

7. The compressor of any of claims 1-6, wherein the rotor has a hydrophilic coating.

8. The compressor of any of claims 1-7, wherein the body defines a coolant passage between the interior cavity and an exterior of the body.

9. A fuel cell system comprising: a fuel cell having a first inlet, a second inlet, and an outlet; a compressor directing first fluid to the first inlet; and a coolant circuit configured to direct coolant to the fuel cell, the coolant circuit also being configured to direct coolant to the compressor.

10. The fuel cell system of claim 9, further comprising a water trap downstream of the outlet of the fuel cell, the water trap directing water towards the compressor for use in a hydration system of the compressor.

11. A method of dynamically humidifying a hydrogen fuel cell air handling system including a compressor and a fuel cell stack connected together by a pipe arrangement, the method comprising: dosing liquid water at the compressor; measuring a first temperature reading of an output flow of the compressor at a first location within the pipe arrangement that is at or downstream of an outlet of the compressor; routing the output flow through a water separation location within the pipe arrangement downstream of the first location; measuring a second temperature reading at a second location within the pipe arrangement, the second location being downstream of the water separation location and being upstream of the fuel cell stack; determining that the second temperature is higher than the first temperature by a predetermined amount; and reducing the dosing at the compressor.

12. A method of dynamically humidifying a hydrogen fuel cell air handling system including a compressor and a fuel cell stack connected together by a pipe arrangement, the method comprising: dosing liquid water at the compressor; measuring a first temperature reading of an output flow of the compressor at a first location within the pipe arrangement that is at or downstream of an outlet of the compressor; routing the output flow through a water separation location within the pipe arrangement downstream of the first location; measuring a second temperature reading at a second location within the pipe arrangement, the second location being downstream of the water separation location and being upstream of the fuel cell stack; measuring a third temperature reading at a third location that is downstream of the second location and upstream of the fuel cell stack; plotting a difference between the second and third temperature readings against a distance along the pipe arrangement between the second and third locations;determining an estimated temperature reading for the first location based on the plotted difference; determining the first temperature reading is below the estimated temperature reading; and reducing the dosing at the compressor.

13. A method of drying out a fuel cell air handling system including a fuel cell stack, the method comprising: cycling air through the fuel cell system without humidifying the air upstream of the fuel cell stack; measuring a first temperature of an output flow of the fuel cell stack at a first location that is at or downstream of an outlet of the fuel cell stack; routing the output flow through a water separation location downstream of the first location; measuring a second temperature of the output flow downstream of the water separation location; and continuing to cycle the air through the fuel cell system at least until the second temperature is lower than the first temperature.

14. The method of claim 13, further comprising: measuring a third temperature reading at a third location that is downstream of the second location; plotting a difference between the second and third temperature readings against a distance between the second and third locations; determining an estimated temperature reading for the first location based on the plotted difference; and continuing to cycle the air through the fuel cell system until the first temperature reading is at least as high as the estimated temperature reading.

15. A method of dynamically humidifying a hydrogen fuel cell air handling system including a compressor and a fuel cell stack connected together by a pipe arrangement, the method comprising: running a compressor in a forward direction to pull an air stream from ambient through an air inlet towards the compressor;injecting water at a flow rate into the air stream downstream of the air inlet; estimating a relative humidity at the fuel cell inlet based on a measured ambient relative humidity, a temperature of the compressor inlet, a pressure of the compressor inlet, and the flow rate of the injected water; and dynamically adjusting the flow rate of the liquid water to keep the estimated relative humidity within a predetermined range.

16. The method of claim 15, wherein estimating the relative humidity at the fuel cell inlet comprises determining an actual absolute humidity at the compressor outlet; calculating a column vector of potential absolute humidity values from potential relative humidity values; and determining the potential relative humidity value that corresponds to the potential absolute humidity value that matches the actual absolute humidity value.

17. A method of dehumidifying a compressor of a hydrogen fuel cell air handling system comprising running the compressor in reverse for a predetermined time period to push an air stream from within the fuel cell air handling system through the compressor and towards ambient.

18. A method of conditioning a fluid flowing within an air handling system of a fuel cell system, the fuel cell system including a fuel cell and a compressor, the method comprising: monitoring a temperature of the fluid; increasing a dosing rate of water into the fluid at or upstream of the compressor when the temperature drops below a predetermined threshold; and decreasing the dosing rate of water into the fluid when the temperature reaches the predetermined threshold.

19. The method of claim 18, further comprising: monitoring an ambient temperature; and draining doser equipment of the air handling system when the ambient temperature drops below a second predetermined threshold, the doser equipment including at least one component of the following components: a water reservoir, a doser, and a conduit.

20. The fuel cell systems and methods of any of claims 9-19, wherein the fuel cell is a selfhydrating fuel cell.

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