Integrated and additively manufactured hydrogen fuel cell injection unit and method for additively manufacturing a fuel injection unit

Abstract

Additively manufactured hydrogen fuel cell injection unit (200), comprising: comprising a body (314) having an integrated noise damping volume, wherein a first end (324) of the body (314) has an opening (356) for mounting an injection unit (391); an ejection arrangement (388) with an ejection tube (390) and a stacked anode inlet (312) positioned at a second end (321) of the body (314), wherein the stacked anode inlet (312) is configured to inject hydrogen into a fuel cell; a heat exchanger (336) integrated into the noise-attenuating volume and comprising a triple periodic minimal surface lattice, TPMS lattice, of unit cells arranged therein, the TPMS lattice being configured to heat hydrogen flowing through it, each end surface of the heat exchanger (336) being separated from the first and second ends (324, 321) of the body (314) by a corresponding volume; and an ejection nozzle (344) coupled to the interior of the body (314) and aligned with the injection (391) near the first end (324) of the body (314), wherein the ejection nozzle (344) is surrounded by a gap (342) and the gap (342) leads to a return path inlet (320) of the body (314) to recapture residual hydrogen near the return path inlet (320), wherein the discharge pipe (390) extends through the heat exchanger (336) and is aligned with the discharge nozzle (344) so ​​that the discharge pipe (390) directs hydrogen through the stack anode inlet (312).

Description

[0001] An injection unit can be used to inject a fuel, such as hydrogen, into a vehicle's fuel cell in a controlled manner to generate electricity and propel the vehicle via an electric motor. One advantage of a hydrogen-powered vehicle is that, unlike gasoline-powered internal combustion engines that emit carbon monoxide, the main byproduct of a hydrogen system is water vapor, thus avoiding most toxic emissions.

[0002] Injection units typically work by injecting a fuel, such as hydrogen, into the anode section of a hydrogen fuel cell (or stack), where a combustion reaction takes place to generate electricity. Before the hydrogen is actually injected into the fuel cell, various preparatory steps are carried out using different connected components. For example, the hydrogen is heated using a heat exchanger. Noise is dampened using a silencer. Furthermore, the hydrogen is brought to a suitable pressure and velocity using various nozzles and injection elements. These elements can assist in recovering unused hydrogen from a previous cycle and injecting hydrogen into the fuel cell using a streamlined exhaust arrangement.

[0003] Modern fuel cell injection units are bulky and unwieldy, making them prone to hydrogen leaks. Bolts and O-rings are required to connect the various components of the injection unit. The bulky muffler is particularly prone to leaks, and complex forging techniques are often used to combat this phenomenon. However, these injection units can have several leakage points. Because common hydrogen isotopes consist of a single proton and a single electron (often bonded in molecular form to another hydrogen atom), the fuel is physically very small and penetrates through the smallest of openings. Leaks are particularly common at elastomer seals such as the O-rings commonly used in fuel injection systems and other connectors between different components.These leaks contribute to fuel losses and an increase in unwanted hydrogen emissions.

[0004] WO 2019 / 178 628 A1 describes a fuel cell system, in particular an SOFC system, wherein the fuel cell system is constructed in a stack-like manner, comprising at least one fuel cell stack with a cathode section and an anode section, at least one end plate, at least one intermediate plate, at least one gas processing plate, wherein the intermediate plate is arranged at least partially above the gas processing plate, the end plate is arranged at least partially above the intermediate plate and the fuel cell stack is arranged at least partially above the end plate.

[0005] DE 10 2021 203 564 A1 describes a jet pump device with at least one jet pump unit for conveying a compressed fuel gas from a gas reservoir unit to a combustion unit, with at least one recirculation gas line for returning a portion of the fuel gas after the combustion unit as recirculation gas back to the jet pump unit. It is proposed that the jet pump device comprise at least one recirculation heat exchanger unit which is designed to heat the compressed fuel gas with thermal energy of the recirculation gas.

[0006] DE 10 2014 105 995 A1 describes a fuel cell system comprising a fuel cell stack, an ejector fluidly connected to the fuel cell stack and having a converging-diverging nozzle with a hydrogen supply nozzle and a return line upstream of a throat of the CD nozzle, and a heat source configured to heat the ejector. A hydrogen supply arrangement for a fuel cell system comprises an ejector with a converging-diverging nozzle and a mixing chamber upstream of the CD nozzle. The mixing chamber has a return line and a hydrogen supply nozzle. A heat source is configured to heat the ejector.

[0007] The object of the invention is to reduce fuel losses caused by leaks.

[0008] The object of the invention is solved by the subject matter of the independent claims.

[0009] The invention is defined by the subject matter of the independent claims.

[0010] According to the invention, an additively manufactured hydrogen fuel cell injection unit comprises a body having a noise dampening volume integrated therein. A first end of the body has an opening for mounting an injector. The hydrogen fuel cell injection unit further comprises an exhaust assembly with an exhaust tube and a stacked anode inlet positioned at a second end of the body. The stacked anode inlet is configured to inject hydrogen into a fuel cell. The hydrogen fuel cell injection unit further comprises a heat exchanger integrated into the noise dampening volume and a triple-periodic minimum surface area (TPMS) lattice of unit cells arranged therein.The TPMS grid is configured to heat hydrogen flowing therethrough, with each end surface of the heat exchanger separated from the first and second ends of the body by a corresponding volume. The hydrogen fuel cell injection unit further includes an exhaust nozzle coupled to the interior of the body and aligned with the injector near the first end of the body. The exhaust nozzle is surrounded by a gap, and the gap leads to a recirculation path inlet of the body to recapture residual hydrogen near the recirculation path inlet. The exhaust tube extends through the heat exchanger and is aligned with the exhaust nozzle such that the exhaust tube directs hydrogen through the stack anode inlet.

[0011] According to one embodiment, the hydrogen directed to the stacked anode inlet comprises (1) the pressurized hydrogen originating from the injection nozzle, (2) the residual hydrogen in the gap, and (3) the hydrogen exiting the heat exchanger. The second end of the body includes an inlet for receiving hydrogen from a source. A volume between the first end surface of the heat exchanger and the first end of the body defines a first volume. A second end surface of the heat exchanger, adjacent to the second volume, is shaped with a geometric gradient designed such that the residual hydrogen received at the inlet at the second end of the body is evenly distributed throughout the second volume upon entering the heat exchanger to enable a uniform heat rise of the hydrogen.

[0012] According to another embodiment, the second end surface of the heat exchanger is located near the second volume into which the hydrogen flows. The first end surface of the heat exchanger defines a lower portion of the first volume and is shaped to form a gradient for a more even distribution of the heated hydrogen. In one embodiment, the gradient is at least partially conical in shape. The TPMS grid comprises a plurality of unit cells with two channels, a first channel conducting hydrogen through the heat exchanger and a second channel passing a fluid to heat the hydrogen.

[0013] According to another embodiment, one side of the body includes two openings for the flow of liquid through the second channel of the heat exchanger. The ejection nozzle can be configured to be selectively activated to controllably direct hydrogen flowing from a heat exchanger surface near the first end of the body through the ejection tube and emit it into the fuel cell. Activation of the injection is configured to create a low-pressure zone in the gap to draw the residual hydrogen through the end-effector tube of the ejection nozzle into the stacked anode inlet.

[0014] According to the invention, an additively manufactured fuel cell injection unit comprises a body having a noise attenuation volume therein. A first end of the body includes an opening for mounting a hydrogen injector. The fuel cell injection unit further comprises an exhaust assembly having an exhaust tube coupled to a stacked anode inlet. The stacked anode inlet is positioned at a second end of the body for injecting hydrogen into a fuel cell. A heat exchanger comprises a grid of unit cells integrated into the noise attenuation volume. The grid is configured to heat hydrogen flowing therethrough. Each end surface of the heat exchanger is separated from the respective first and second ends of the body by a corresponding volume. An end surface of the heat exchanger adjacent to each corresponding volume includes a gradient.An exhaust nozzle is coupled to an injector outlet at the first end of the body. The exhaust nozzle is surrounded by a gap. The gap leads to a recirculation path inlet of the body to recapture excess hydrogen. The exhaust tube extends through the heat exchanger and is aligned with the exhaust nozzle, so that the exhaust tube is configured to direct hydrogen to the fuel cell via the stack anode inlet.

[0015] According to one embodiment, one or both end surfaces of the heat exchanger adjacent to the corresponding volumes are at least partially conical in shape.

[0016] According to one embodiment, the injection is selectively activated to inject hydrogen from a source into the discharge nozzle to create a low pressure region in the gap in which the unused hydrogen from the last engine cycle is recaptured.

[0017] According to one embodiment, the injection is further configured to deliver the heated hydrogen exiting the heat exchanger into the volume defined by the surface of the heat exchanger into the ejection nozzle and then into the ejection tube.

[0018] According to one embodiment, the fuel injection unit further comprises a plurality of pressure sensors collectively printed into an outlet of the noise attenuation volume. The injection can be cyclically activated to inject the hydrogen when the pressure drops below a threshold. The additively manufactured body and the integrated noise attenuation volume and heat exchanger can be molded as a single, integral unit to avoid the use of elastomeric seals. The body elements are designed to avoid sharp angles and abrupt edges, using curved sections instead. The exhaust tube can be a venturi tube manufactured by additive manufacturing without a relief angle.

[0019] According to the invention, a method for additive manufacturing of a fuel injection unit is also provided. The method comprises forming a body with an at least partially cylindrical shape and defining a sound-damping volume therein.

[0020] The method further includes printing a venturi extending longitudinally along at least a portion of the body from a first end to a second end, and a stack anode inlet at the second end for injecting hydrogen into a fuel cell. The method also includes printing an ejection nozzle aligned with the venturi at the first end for selectively injecting hydrogen into the venturi, and enclosing the ejection nozzle in a gap extending to an opening in a surface of the body. The gap is for recovering unused hydrogen for emission via the ejection nozzle and venturi into the stack anode inlet. The method further includes integrating a heat exchanger into the sound attenuation volume.The heat exchanger includes a grid of unit cells disposed between the venturi tube and a periphery of the body such that a first end surface of the heat exchanger adjacent the first end has a gradient defining a first volume at the first end, and a second end surface of the heat exchanger adjacent the second end has a gradient defining a second volume with the second end. Hydrogen entering an inlet opening in the second end surface flows through the heat exchanger from the second volume to the first volume. The method also includes forming an opening in the first end for mounting an injector configured to selectively deliver hydrogen from the first volume and from an injection through the ejection nozzle and into the venturi tube for entry into the fuel cell at the stack anode inlet.

[0021] In one embodiment, the first or second surface of the heat exchanger is at least partially conical in shape.

[0022] In a further embodiment, the body further comprises a coolant inlet for injecting coolant into a channel of the heat exchanger and a coolant outlet for receiving the coolant from the heat exchanger.

[0023] The accompanying drawings, which form a part of this description, illustrate embodiments of the description and, together with the description, explain the principles of the description. Fig. Figure 1 is a mechanical diagram of an existing fuel injection system. Fig. 2 is a mechanical diagram of an additively manufactured integrated fuel injection unit according to the description. Fig. 3 is a cross-section through the fuel injection unit of Fig. 2 along a vertical axis through the diagram, as described. Fig. Figure 4 is a geometric representation of a two-channel heat exchanger according to the description. Fig. Figure 5 is a conceptual diagram of a three-dimensional (3-D) powder bed fusion printer for the additive manufacturing of metal products such as the device in Fig. 2. Fig. 6 is an exemplary flow diagram of a method for additively manufacturing an integrated fuel injection unit according to the description.

[0024] The accompanying drawings are not necessarily to scale and may represent a simplified representation of various features of the present description, including, for example, certain dimensions, orientations, positions, and shapes. In some cases, readily apparent features may be omitted from certain drawings so as not to unduly obscure the concepts of the description. The details associated with such features will be determined in part by the particular intended application and use case environment.

[0025] Devices, systems, and methods are described in which the elements of a fuel injection system are unified using additive manufacturing, also known as 3D printing. The result is a much smaller and more streamlined fuel injection system. There are many types of 3D printers. Printers specifically designed for printing metals, such as powder bed fusion (PFD) printers, can be particularly useful. They first create a CAD file, which, using specialized computer-aided design (CAD) software, defines the shape, geometry, and properties of the part to be printed, sometimes called the "part." Increasingly advanced 3D printers can use advanced techniques to precisely print very small geometric metal and other designs, resulting in a single, integrated unit as the final component.

[0026] In many 3D printing applications, the CAD file is then "sliced" by a slicing application, which divides the part designed in CAD into many small geometries that, when assembled, reproduce the part. Slicing can be used because, in PDF and similar printers, the printed object is gradually built up from a substrate in individual slices. Each slice corresponds to a layer of powder. Each of the sampled cross-sectional areas of the layers melts and then solidifies as the 3D printer scans each new layer. To print a slice of a part, a uniform layer of powder can first be applied to the substrate using a caster. A laser or electron beam can then be used in the printer to selectively fuse or melt areas of the slice that are considered part of the part according to the coordinates found in each slice.The remaining unfused areas of the disc are not part of the part, so the powder belonging to those areas is not melted and can later fall off or fall out of the design. After the melting process just described, another layer of powder can be deposited on top of the freshly printed layer using the casting device. The laser or electron beam can then scan this layer to form the next disc in the series. This process continues until all layers have been deposited or scanned. The result is a part or printed object that can be cleaned of excess powder.

[0027] One advantage of 3D printing a part is that a multitude of elements can be printed as a single, discrete, unified object. In various aspects of the disclosure, the fuel injection unit and its various components are integrated into a single design and then additively manufactured. The resulting fuel injection unit is significantly smaller than existing units. An equally important problem with modern hydrogen fuel cells is hydrogen leakage. Existing fuel injection systems are manufactured using typical subtractive manufacturing techniques, such as machining, molding, tooling, extrusion, forging, die casting, and the like. One problem with applying this approach is that it creates a number of individual components that must be joined together by a fastener.As mentioned in the background section, hydrogen is a very small molecule and can easily escape from many components. Subtractive manufacturing techniques generally rely on the use of bolts, nuts, O-rings, clamps, and other such elements to connect various objects together, through which hydrogen can easily leak. This not only leads to unwanted hydrogen emissions into the air but also significantly reduces the overall efficiency of the hydrogen vehicle as it spontaneously loses hydrogen. In addition, casting, machining, and forging techniques tend to create sharper corners and draft angles, which can undesirably alter the efficient flow of hydrogen and cause unintended emission artifacts.In contrast, due to the geometric nature of additive manufacturing, it is easier to form smooth, intended surfaces that match the actual geometric goals of the structure and minimize unwanted artifacts caused by sharp corners, warpage angles, and other imperfections due to many implementations of existing manufacturing.

[0028] Fig. Figure 1 is a mechanical schematic of an existing fuel injection unit. The device's piping 15 carries the hydrogen, to be fed into the fuel cell via the injection unit, from inlet 20 to inlet 17, which is the inlet to heat exchanger 19. One function of heat exchanger 19 is to raise the temperature of the hydrogen flowing through one of the channels by exchanging heat between a first channel containing the hydrogen and a second channel, which may contain a hotter "coolant" or other substance, from which heat can flow to the hydrogen, or to which cold can flow from the hydrogen to the coolant, in accordance with general thermodynamic principles. As the figure shows, the typical heat exchanger 19 can be implemented as a plurality of plates stacked one on top of the other, the area of ​​which is maximized to maximize the contact area of ​​the channels with each other.The heat exchanger 19 can be attached to a vehicle frame with a screw and an opening 18a in the bracket.

[0029] The heat exchanger 19 is generally secured to a bracket 18 with a series of bolts. The purpose of the bracket 18 is to allow the fuel injection unit to be rigidly mounted to a frame (not shown) on a part of the vehicle's interior. The heat exchanger 19 may also include one or more pressure sensors 12b mounted on the heat exchanger 19 to detect the pressure values ​​of the fluids entering the heat exchanger 19.

[0030] The hydrogen is progressively heated by the heat exchanger 19 as it flows from the inlet 17 until it exits the heat exchanger 19 and flows into a channel 16, which may be an elongated tube. The inlet and outlet of the channel 16 may include respective ports 16a and 16b (e.g., connected with bolts, nuts, or other fasteners), which in turn may contain additional pressure sensors. An example is the pressure sensor 12a near the port 16b. Hydrogen may then flow into a fuel rail dampening volume 14 (sometimes referred to as a FRAV, sound attenuation volume, or dampening volume). The FRAV in Fig. 1 is a complex arrangement of components designed to reduce the acoustic noise caused by the hydrogen flow and the corresponding pressure differences. As shown in Fig. 1, the FRAV 14 is a separate component from that of the heat exchanger 19. While the outer part of the FRAV 14 is shown in the figure, the interior of the FRAV 14 comprises an outer cylinder (for example, defined by component 14b) and an inner cylinder (not visible). The inner cylinder contains the heated hydrogen flowing out of the heat exchanger from the outlet 16a of the channel 16. The circumference of the port 16a may correspond to the circumference of the inner cylinder of the FRAV 14. The outer cylinder, defined by component 14b, contains dampening hydrogen (for example, a portion of the hydrogen used to dampen acoustic noise) positioned between the inner circumference of the inner cylinder and the outer circumference (component 14b) of the FRAV 14.

[0031] Existing FRAVs typically consist of a subset of individual parts that are sealed and bolted together. In the example shown, the FRAV 14 comprises two aluminum components 14a and 14b. Currently, the aluminum components 14a and 14b are manufactured by forging, die casting, and / or machining. After forming, the aluminum components 14a and 14b are bonded and sealed together. During the manufacture of the aluminum components 14a and 14b, for example, a web 27 may be formed. Half of the web 27 may be manufactured as part of the aluminum component 14a, the other half of the web 27 may be manufactured as part of the aluminum component 14b. The respective sections of the web 27 are then aligned and connected together using screws 28 extending through the web.

[0032] To further seal the aluminum portions 14a and 14b of web 27, an O-ring is inserted between web 27 to reinforce the seal. The O-ring is compressed thinly when the two aluminum portions 14a and 14b of FRAV 14 are joined together; for this reason, the O-ring is not visible. Furthermore, as previously mentioned, FRAV 14 contains an inner cylinder (not visible) through which the heated hydrogen gas from heat exchanger 19 is passed. A second O-ring is inserted within FRAV 14 between aluminum components 14a and 14b, along with a device similar to web 27. Thus, FRAV 14 contains at least two O-rings, in addition to the multiple bolts 28 that connect the respective portions of at least web 27 together. These areas, where bolts 28 and elastomeric materials (called O-rings) are used, are particularly susceptible to hydrogen leaks.

[0033] In addition, the FRAV 14 has two injectors 6 and 8. The injectors can be switched on or off to optimize the hydrogen flow through the inner cylinder of the FRAV 14. Injectors 6 and 8 can be positioned near an inlet 10 that allows pressurized hydrogen to flow to injectors 6 and 8 and be released into the FRAV 14 when injectors 6 and 8 are activated. The FRAV 14 can also be located near the pressure sensor 12a that measures the pressure inside the FRAV 14. In this example, injectors 6 and 8 are side injectors. Injectors 6 and 8 bridge the gap between the inner and outer cylinders of the FRAV 14. This means that the hydrogen is fed into the FRAV 14 with injectors 6 and 8 via the inlet 10.Injectors 6 and 8, in turn, control the pressure and velocity of the hydrogen flow into the inner cylinder of FRAV 14. In addition to the hydrogen entering FRAV 14 from heat exchanger 19, hydrogen also comes from injectors 6 and 8. When injectors 6 and 8 are activated selectively or periodically, FRAV 14 dampens the resulting noise.

[0034] As in Fig. 1, the FRAV 14 is connected to the ejector assembly 13. While the ejector assembly 13 comprises various components, it is identified as that part of the fuel injection unit from (and including) reference numeral 13 to (and including) reference numeral 12. The ejector assembly 13 terminates at the stacked anode inlet 12, where the hydrogen is injected into the anode of the corresponding fuel cell. The ejector assembly 13 may consist of three injection-molded components welded into a single assembly. The ejector assembly 13 is connected to the FRAV 14 as a standalone device. In this example, the cylindrical portion of the ejector assembly 13 is coupled to the aluminum component 14a by three screws, two of which are represented by small segments 32 that protrude through the connecting plate 31, and one of which is not visible because it is located on the opposite side of the unit.During use of the fuel injection unit, hydrogen is directed from the inner cylinder of the FRAV 14 through the tube 33 of the exhaust assembly 13 and from the stacked anode inlet 12 into the anode portion of a corresponding fuel cell. The exhaust assembly further includes pressure sensors 39a and 39b for detecting the pressure as the hydrogen gas flows through the region of the tube 33.

[0035] The example of a fuel injection unit described above is prone to hydrogen leaks in several areas. During manufacturing, the FRAV 14 is first split into two separate components, which are then joined together using a combination of bolts and O-rings. As previously mentioned, the FRAV 14 is prone to hydrogen leaks due to the inadequacies of the elastomer O-rings and the general inadequacy of the joint. In addition, the exhaust assembly 13 is separately connected to the FRAV by a multitude of bolts. Therefore, hydrogen can leak through the imperfect connection between the exhaust assembly 13 and the FRAV 14. The injection unit, as shown from the inlet 20 through the tube 15 and finally to the stacked anode inlet 12, is not only prone to excessive hydrogen leakage, but its irregular and larger shape must be considered in the overall design of the vehicle body.Each of the pressure sensors, including pressure sensor 12a on FRAV 14 and pressure sensors 39a and 39b on ejector assembly tube 33, is subject to additional hydrogen leakage.

[0036] Accordingly, in one aspect of the disclosure, additive manufacturing techniques are used to (1) integrate the fuel cell injection unit into a single, unified structure and (2) reduce and streamline the shape and size of the structure, thereby making the vehicle's propulsion system more compact and capable of producing more power in a smaller volume. As discussed further below, a streamlined internal shape of the FRAV's internal volume can also result in the integrated fuel injection unit having significant performance advantages, such as an efficient venturi tube in the FRAV without a significant air angle.

[0037] Fig. Figure 2 is a mechanical diagram of an additively manufactured, integrated fuel cell injection unit 200 according to one aspect of the description. The integrated fuel cell injection unit 200 includes, in comparison to Fig. 1 and including a number of additional differences to be discussed here, an efficient version of the Fig. 1 features positioned between the inlet 20 and the stack anode inlet 12.

[0038] The structure of Fig. 2 can be additively manufactured using a variety of suitable 3D printers. In the initial stages of an additive manufacturing process, the designer typically creates a detailed CAD file containing a visual and numerical representation of the features of the structure in question. In one example, a powder bed fusion (PBF) 3D printer may be used. The CAD drawing is then formatted for use by the 3D printer. In one step, for example, software compatible with the 3D printer may be used to analyze the CAD file(s) and divide the file into a series of slices. The slices physically and visually represent cross-sectional segments of the structure to be printed. The slices thus contain the necessary data to reproduce a physical version of the integrated hydrogen injection unit in the 3D printer.

[0039] In this embodiment, one wafer is produced at a time. A PDF printer in this embodiment may include a substrate. During a first print cycle, the printer may use a coater to deposit a first layer of powder into the powder bed. In alternative print designs, a roller may instead be used to distribute a predetermined amount of powder from a first powder source onto the substrate. Depending on the printer and design goals, the powder may be a specific type of metal or alloy. However, it is understood that different printer types are capable of printing different materials.Back to the first print cycle: After the first layer has been applied, a laser or electron beam source can deflect the laser or electron beam via a movable mirror, allowing the laser or electron beam source to selectively melt or weld portions of the applied powder sheet, as defined by the data in the sheet. The remaining, unmelted portions of the applied powder can be removed later, for example, when the final structure is removed from the printer.

[0040] After the first slice has been applied and selectively melted, the 3D printer can apply the next slice and selectively melt areas within that slice. This process can continue until the so-called part is completed. Any remaining unused powder can be removed, and the part can be reworked for cleaning. The structure can then be integrated with other structures and finally connected to the corresponding fuel cell(s) in the vehicle part.

[0041] In relation to Fig. 2, the integrated fuel cell injection unit 200 includes a stack anode inlet 212, which provides an opening for introducing heated hydrogen at the appropriate pressure and velocity into the anode portion of an associated fuel cell or fuel cell stack (not shown). The integrated fuel cell injection unit 200 also includes a flange 202, which in this example has two openings for coupling the integrated fuel cell injection unit 200 to its respective position in the vehicle. The stack anode inlet 212 and the flange 202 are positioned at the upper end 221 of the integrated fuel cell injection unit 200. (The upper end 221 is also referred to as the second end throughout this description.)

[0042] As shown, the integrated fuel cell injection unit 200 further includes a generally cylindrical body 214. The upper portion of the body 214 near the second end assumes a generally conical portion 222 of the body 214, although other shapes are possible. As shown in the cross-sectional view of the integrated fuel cell injection unit 200 in Fig. 3, the interior of at least a portion of the conical portion 222 of the body 214 comprises a volume between a surface of an internal heat exchanger and the top or second end of the integrated fuel cell injection unit 200. In this embodiment, the conical portion 222 further comprises an inlet 204. The inlet 204 is coupled to a channel for receiving fresh hydrogen from a hydrogen tank or other source. In some embodiments, the inlet 204 may additionally or alternatively be used to capture unused hydrogen previously injected into the corresponding fuel cell. In this embodiment, unused hydrogen that does not react or explode in the fuel cell may be channeled back into the inlet 214 of the conical portion 222 of the body 214 through the channel.To ensure the efficiency and performance of a fuel cell or fuel cell stack, the integrated fuel cell injection unit 200 is configured to inject more hydrogen into the fuel cell than is needed for the subsequent chemical reaction. Consequently, unused hydrogen can be pumped back to the stack anode inlet 212 of the stack using a jet pump or recirculation fan. As shown in FIG. Fig. 3, residual hydrogen not used in a previous reaction can be recycled via a special recycle path inlet 220.

[0043] As in Fig. 2, the body 214 includes a lower end 224, also referred to herein as the first end. Furthermore, the body 214 includes two openings 206 and 208. The opening 206 may be an inlet, and the other opening 208 is an outlet. As described below, the openings 206 and 208 may be used to direct fresh and used coolant, respectively, through a second channel of a dual-channel heat exchanger. The temperature of the coolant is higher than that of the hydrogen when the coolant enters the integrated fuel cell injection unit 200. The body 214 also includes a partial view of the recirculation path inlet 220 into the body 214. Residual hydrogen from the environment, which might otherwise result in wasted emissions, may be drawn into the recirculation path inlet 220 and reused in the corresponding fuel cell.

[0044] In the integrated fuel cell injection unit 200, the interior of the body 214 may include a volume (for example Fig. 3), which serves as a damping volume. That is, as will be seen, an inner cylinder within the body 214 may contain a channel for conveying heated hydrogen for injection into the fuel cell, while an outer volume of the body 214 may serve to dampen the sound, similar to the FRAV 14 of Fig. 1.

[0045] Fig. 3 is a cross-section through the fuel cell injection unit of Fig. 2 along a vertical axis through the integrated fuel cell injection unit 200, according to one aspect of the description. The lower (first) end 324 of the integrated fuel cell injection unit 200 has an opening 356 integrated into the body 314 of the integrated fuel cell injection unit 200. Although more than one such opening may be present, only one opening 356 is shown in this embodiment. A nozzle receptacle 360 ​​is positioned perpendicular to the opening 356 in the body 314. The nozzle receptacle 360 ​​can be attached to an interior surface of the body 314. The function of the opening 356 and the nozzle receptacle 360 ​​is to allow the manufacturer to introduce a selectively activating hydrogen injector 391 vertically into the body 314 near the lower (first) end 324. The injector 391 has a function analogous to one of the Fig. 1. The injection 391 serves to control the flow of heated hydrogen in volume 340, in addition to the hydrogen exiting from the exhaust. Unlike in Fig. 1, the injection can be Fig. 3 be installed vertically in the opening 356 so that the end of the injection can be securely coupled to the nozzle holder 360.

[0046] Pressure sensors can be integrated into the nozzle receptacle 360 ​​or the injector itself, or both, as well as other areas of the body 314 of the integrated fuel cell injection unit 200. In existing techniques, the pressure sensors are discrete elements that can lead to leaks. In the embodiment of Fig. 3, however, one or more pressure sensors can be integrated into the additively manufactured body 314 to prevent leakage. During 3D printing, printing can be temporarily paused at a certain point to add a pressure sensor, after which printing can be resumed. In other examples, the 3D printer itself can be used to manufacture the pressure sensor or parts thereof. In both cases, the pressure sensors can be integrated into the body 314, effectively eliminating leakage issues.

[0047] The injector can be installed at a strategic point during the additive manufacturing process or deployed after the 3D printing job is completed. The nozzle receiver 360 not only serves to stabilize and secure the deployed injector, but also includes an outlet that directs the hydrogen emitted by the injector through a suitable path 361. The path 361, in turn, allows the injector outlet to effectively align with an inlet 344a of the ejection nozzle 344. The ejection nozzle 344, shown here in cross-section, can be a cylindrical or tubular nozzle that receives hydrogen from the injector outlet (via channel 361) as well as from other hydrogen sources described herein and expels the hydrogen into an ejection tube 390. In some embodiments, the ejection tube 390 is a venturi tube.The pressure changes resulting from the selective activation of the injection cause the ejection nozzle 344 to eject hydrogen into the ejection tube 390. This mechanism of action includes pressure differentials that occur in a gap 342 as a result of the selective injections of hydrogen by the injector described herein. The gap 342 is coupled outwardly through the body 314 via the recirculation path inlet 320 (shown in cross-section). In other words, the gap 342 is a return path for residual hydrogen and includes the wide, split cross-sectional opening (i.e., the recirculation path inlet 320) that bulges upward toward the ejection tube 390. The gap allows residual hydrogen located outside the integrated fuel cell injection unit 200 to flow through the inlet 320 into the body 314 for use in the fuel injection process.Similar to the unused hydrogen entering inlet 304, the recirculation path can be used to recycle residual hydrogen that was injected into the fuel cell but not used. This residual hydrogen can originate from the output of the fuel cell stack during operation.

[0048] The exhaust tube 390 extends at least partially longitudinally of the body 314 to the stack anode inlet 312 at the upper end 321, where the hydrogen is supplied to an anode of the fuel cell. When an interaction occurs in the fuel cell, the unused hydrogen can be diverted through a channel (not shown) to the inlet 304. Thus, the inlet 304 receives unused hydrogen from the fuel cell (or fuel cell stack), which receives hydrogen from the stack anode inlet 312. The hydrogen not used in the interaction therefore enters the conical portion 322 of the body 314 via the inlet 304. The unused hydrogen may initially enter the conical portion 322 as a liquid, for example, when a significant amount of heat is released during the final fuel cell reaction.In various embodiments, the inlet 304 may alternatively or additionally be used to feed hydrogen from another source, for example a tank, into the integrated fuel cell injection unit 200.

[0049] The unused hydrogen from this reaction, after passing through the inlet 304, first enters a volume region 338 located near the upper surface 321 and around the exhaust tube (e.g., Venturi tube) 390. Since the unused hydrogen at this stage has a lower temperature than that required for injection into the fuel cell, the unused hydrogen should be reheated relatively quickly and efficiently. Accordingly, in one aspect of the description, a heat exchanger 336 is positioned within the body 314 of the integrated fuel cell injection unit 200. The heat exchanger 336 forms the set of wavy lines on either side of the exhaust tube 390 and the empty areas therebetween. While Fig. 3 is a cross-sectional view, in various embodiments, the heat exchanger 336 may extend around the entire circumference of the exhaust tube 390.

[0050] The strategic placement of the heat exchanger 336 within the body 314 significantly simplifies the design and significantly reduces the space required for the heat exchanger. In another aspect of the description, the upper surface 350 of the heat exchanger 336 is formed in the shape of a gradient around the body 314 of the integrated fuel cell injection unit 200. For example, the surface 350 on the top of the heat exchanger 336 gradually increases in height. Like a cone (symmetrical or not), the height of the opposite side of the heat exchanger surface 350 gradually decreases. The distributed gradient of the heat exchanger 336, defined by its conical surface 350, offers significant advantages. For example, the gradient of the surface 350 allows the hydrogen supplied from the inlet 304 to be evenly distributed over a much larger area.In addition, the heat exchanger 336 uses instead of the plate heat exchanger of . Fig. 1 a gyroscopic or similar pattern using a triply periodic minimal surface area (TPMS) lattice of unit cells. As a result, hydrogen can be heated to the required temperatures much more quickly and efficiently. For clarity, note that the gradient has a surface extending around the perimeter of the gap 342 / ejection nozzle 344 / ejection tube 390 assembly (collectively referred to as "ejection assembly 388") on the inside of body 314 and bounded by the perimeter of body 314 on the outside of body 314, while showing a cross-sectional view.

[0051] For a better understanding of the fluid flow in the embodiment of the two-channel heat exchanger 336, Fig. 4 shows a non-cross-sectional view of the heat exchanger. In general, the example heat exchanger 336 according to Fig. 3 is a two-channel heat exchanger. In the first channel 336a (referred to as one of several segments), the hydrogen can flow freely. For clarity, a first channel to the right of the exhaust tube 390 is also shown in the reference numeral 332. The heat exchanger 336 is optimized to facilitate the flow of hydrogen through the first channel 336a, starting from the surface 350 of the heat exchanger 336 and then downward through the various branches of the first channel 336a to a second conical gradient 350 near the lower end 324 of the body 314 of the integrated fuel cell injection unit 200. Fig. 3, it is not clear that the channels, similar to 336a, are arranged in topologically optimized three-dimensional shapes configured to facilitate the flow of hydrogen through the heat exchanger 336 and into the volume 340 at the lower (“first”) end of the body 314.

[0052] Similarly, a second channel 336b is present adjacent to the first channel 336a. The second channel 336b is depicted essentially as empty space within the heat exchanger 336. The second channel 336b carries the "coolant" material from which the hydrogen absorbs heat. The second channel 336b is designed so that the coolant molecules cannot leave the second channel. Like the first channel 336a, the second channel 336b is topically optimized three-dimensionally. In various embodiments, the second channel 336b is often routed directly adjacent to the first channel 336a to facilitate heat exchange between the hydrogen in the first channel 336a and the coolant in the second channel 336b.

[0053] Since the coolant entering the heat exchanger via inlet 206 has a higher temperature than the hydrogen passing through the heat exchanger, the coolant can be used to heat the hydrogen. The hydrogen absorbs heat from the coolant until it evaporates through heat exchange with the coolant. A thermally conductive metal or alloy can be used to define the respective channels 336a-b and physically separate the two materials. For example, fresh coolant can be expelled into inlets 362, which in this cross-sectional view are located closer to the top end 321 of the integrated fuel cell injection unit 200, and cold (spent) coolant can exit the body 314 via certain outlets 372 near the first end 324. In various embodiments, the inlets 362 can be Fig. 3 entrance 206 ( Fig. 2) and the outlets 372 of Fig. 3 exit 208 ( Fig. 2).

[0054] After the heated hydrogen reaches the bottom of the heat exchanger 336, it flows through the conical wall 352 and fills the volume 340 below the heat exchanger 336.

[0055] When the injection is activated, hydrogen is expelled from an external source (e.g., a tank). A consequence of this emission is that the unused hydrogen in volume 340, heated by heat exchanger 336, is forced through path 361, which directs the injection to the ejection nozzle 344, through the inlet 344a of the ejection nozzle 344, up through the ejection tube 390, and into the fuel cell via the stack anode inlet 312 at the top end 321 of the integrated fuel cell injection unit 200. Furthermore, activating the injection generates hydrogen at a specific pressure and velocity. These properties of the expelled hydrogen create a low-pressure region in the gap 342. This mechanism, in turn, allows residual hydrogen outside the body 314 of the integrated fuel cell injection unit 200 to enter the gap at the recirculation path inlet 320.The residual hydrogen in the gap can enter the exhaust tube 390 along with the hydrogen released by the injection and the unused hydrogen that has passed through the heat exchanger. The hydrogen can then enter the fuel cell via the stack anode inlet 312. In short, the integrated fuel cell injection unit 200 can use the hydrogen activated by the injection to create the negative pressure zone in the gap 342, thereby drawing the residual hydrogen back into the stack anode inlet.

[0056] Another significant advantage of the described subject matter is that the ejection arrangement 13 in Fig. 1 is now integrated into the body 314 of the integrated fuel cell injection unit 200. The exhaust assembly, in this example, may include the exhaust tube 390 and the stacked anode inlet 312. Accordingly, the connecting plate 31 and the bolts represented by cylindrical segments 32 are no longer required. Thus, this area where hydrogen leaks is effectively eliminated.

[0057] In a related aspect of the description, the heat exchanger 336 is integrated into the damping volume (FRAV volume). Activation of the injection(s) causes a reduction in fluid pressure as the hydrogen flows. When the activated injection closes, the body 314 and the gap 342 leading to the recirculation path inlet 320 can be used to dampen the sound. In the example shown, the volume within the body 314 up to the boundary formed by the ejection assembly 388 forms the FRAV volume. The inclusion of the heat exchanger 336 in the FRAV volume potentially saves a significant amount of space and reduces the overall size of the integrated fuel cell injection unit 200. The ejection nozzle 344 and the ejection tube 390 correspond to the inner cylinder of the FRAV 14 in Fig. 1.

[0058] As in Fig. 3, the high-pressure, high-velocity hydrogen gas flows from the injector through nozzle 344 and exhaust tube 390, the latter of which may be a venturi tube. In some cases, fresh hydrogen is supplied to inlet 304 from one or more fuel sources, such as hydrogen tanks. The hydrogen that has just passed through inlet 304, volume 338, heat exchanger 336, and volume 340 is directed into exhaust tube 390 via exhaust nozzle 344, as described herein. In addition to this freshly supplied hydrogen, residual hydrogen observed near integrated fuel cell injection unit 200 is generally a byproduct of previous interactions or combustion in the fuel cell stack involving hydrogen, certain other gaseous species, and water.The geometry of the exhaust tube 390 can create the negative pressure zone in the gap 342, allowing the residual hydrogen to flow into the gap 342. The hydrogen in the gap 342 is then propelled upward through the exhaust tube 390. The entire pressure control system is designed so that when the pressure of the hydrogen flow to the stacked anode inlet 312 falls below a threshold, the injector 391 can be activated, injecting hydrogen. This injection of hydrogen increases the pressure in the system, whereupon the injector 391 is closed, and the flow of hydrogen from the injector 391 stops.

[0059] Depending on the power demand of the fuel cell to which the integrated fuel cell injection unit 200 is coupled, the cyclic injections from the injection 391 can occur at a higher or lower frequency. The venturi tube acts like a jet pump or a vacuum pump. In some embodiments, the inlet of the anode stack can reach a point where it is at a higher pressure than the injected contents of the integrated fuel cell injection unit 200. The pressure difference would naturally cause the hydrogen to flow backward. This process can be avoided by using a venturi tube as the exhaust tube 390. For example, when hydrogen is injected into the fuel cell, a negative pressure region is created, as described herein. The gap 342 can overcome the pressure difference by absorbing residual or excess hydrogen from the recirculation path inlet 320.

[0060] A venturi tube increases the speed of the hydrogen flowing through it by forcing it into a tube with a cone, such as cone 396 near the base of venturi tube 390 in Fig. 3. The remaining portion of the venturi tube, which extends upward to the stacked anode inlet 312, is restricted to a cylindrical size. Due to the geometric constraint, the hydrogen flow must be accelerated, which reduces its pressure and creates a partial vacuum at gap 342. In the venturi tube, the pressure of the hydrogen increases as it exits the constriction. The integrated fuel cell injection unit 200 in Fig. 3 takes advantage of the velocity of the hydrogen and the sonic flow from the discharge nozzle, so that the geometric relationship between the venturi tube and the discharge nozzle 344 maintains appropriate pressures that prevent backflow of hydrogen.

[0061] In contrast, the venturi tube in existing techniques may not be ideal because it is made of injection-molded plastic. This, in turn, results in an undesirable air angle that compromises the effectiveness of the venturi tube. However, in the present embodiments, injection molding is not required, and the venturi tube can be additively manufactured without compromising the relief angle.

[0062] A further advantage of the description is that the pressure sensors 39a and 39b on the tube 33 of the ejection assembly 13 are eliminated. Instead, the pressure sensors can be integrated into the FRAV body 314 at strategic points during the additive manufacturing process. Hydrogen leaks attributable to the sensors 39a and 39b can therefore be largely avoided.

[0063] Another shortcoming of existing fuel-injection systems is the fact that FRAVs, or acoustic silencers, typically require forging to close the molecular structure of the aluminum and prevent excessive hydrogen from diffusing through the aluminum. The disadvantages associated with a lengthy forging process can be eliminated through additive manufacturing, and the integration of the various fuel-injection components into the body significantly minimizes hydrogen diffusion.

[0064] Fig. Figure 4 is a geometric representation of a dual-channel heat exchanger 436 according to one aspect of the description. The heat exchanger 436 corresponds to the heat exchanger shown in Figures Fig. 2 and Fig. 3. An upper portion 450 of the semi-cylindrical structure shows the gradient used to increase the surface area of ​​the incident hydrogen gas entering the heat exchanger from volume 338 ( Fig. 3). The spherical-looking elements are part of the first channel, through which the hydrogen is intended to flow downwards from the upper gradient 450. The first channel 436 therefore carries hydrogen. A TPMS lattice of unit cells can be used to form the channels and confine the fluid flow. For example, the metallic portion 463 of the first channel 436a can be used to confine the hydrogen flow within the first channel, which can be distributed throughout the heat exchanger 436. The hydrogen itself comprises the substance between the channels, for example, the hydrogen 465.

[0065] The empty spaces between the first channels 436a, including channels 436b, each form a second channel that carries the coolant. Since a significant amount of hot coolant is required to heat the hydrogen, the second channels are larger. It should also be noted that a simple external representation of the heat exchanger 436 does not appear to show how the hydrogen can flow from the upper part 450 to the lower part 424. However, it should be considered that the internal part of the heat exchanger 436 can interconnect the various branches of the first channel. As previously mentioned, the TPMS grid can be designed to topologically optimize the hydrogen flow from the upper part 450 to the lower part 424.For example, the two channels 436a and 436b can be aligned so that the hydrogen is exposed to a maximum amount of coolant (albeit separated by the channels), but flows quickly enough from the upper part 450 to the lower part 424 to provide a sufficient amount of hydrogen fuel for the fuel cell stack.

[0066] The heat exchanger 436 may also have dedicated points for the supply of coolant, for example, an inlet 462in into the second channel, and for the removal of used (cold) coolant, for example, at the outlet 462out. In this way, the heat exchanger 436 can be continuously supplied with a sufficient volume of heated coolant via the channels 426in and 462out.

[0067] The lower part 424 may correspond to an edge of the lower end 324 ( Fig. 3). It should be noted that in some embodiments, as in Fig. 3, the gradient is an upward cone. Thus, only the edges of the ground surface 424 are visible, making the object appear flat at the bottom.

[0068] Although the heat exchanger is generally included along with other components in a practical integrated fuel cell injection unit 200, in Fig. 4, only the heat exchanger is shown so as not to overly obscure the concepts of the description. Although the heat exchanger 436 has a semi-cylindrical shape with gradients on the upper and lower portions 450 and 424, the principles of the description are not limited to this shape. A variety of geometries can be adopted and incorporated into the sound attenuation volume. In some examples, additional channels can be used. The channels can also be formed from different materials and with different structures.

[0069] Fig. 5 is a conceptual diagram of a three-dimensional (3-D) powder bed fusion printer 500 for additive manufacturing of metallic products such as the device of Fig. 2. Although a powder bed fusion (PBF) printer is described for illustrative purposes, a variety of different types of 3D printers may be used to manufacture the integrated fuel cell injection unit 200 without deviating from the principles of the description. Furthermore, 3D printers may be complex devices and controlled with integrated electronics, a separate computer, or a combination thereof; this description focuses on the basic elements.

[0070] As previously mentioned, after creating a CAD file of the integrated fuel cell injection unit 200, software specific to the respective 3D printer can be run to geometrically divide the structure and its details into a large number of individual slices. Each slice corresponds to a powder layer. The powder can consist of a variety of metals or their alloys, such as, but not limited to, aluminum or an aluminum alloy. After applying the layers and deposition of the relevant cross-sectional areas of the structure, the integrated fuel cell injection unit 200 can be post-processed and completed.

[0071] As in Fig. 5, the hopper 502 may be a large tank containing the powder to be used during printing. A dispensing device, such as channel 504, may withdraw selected amounts of powder from the tank and direct it to the caster 510. The caster 510 is a movable device, and for this reason at least, the use of channel 504 to withdraw the powder is a simplification. In reality, the caster may rest on the platform 523 or hover above it when a scan is in progress. In some embodiments, the caster may include a smaller tank to store enough powder for a few cycles. In some embodiments, the powder is supplied from a tank via a vertical channel when the caster 510 is at rest.

[0072] After the control unit controlling the printing process receives the cut code and the hopper supplies the caster with powder, the caster can apply a first layer to the substrate 518. At the beginning of the printing process, the substrate 518 can be approximately level with the platform 523. The caster 510 then slides over the surface of the substrate and applies a first layer, which represents the first slice or base of the integrated fuel cell injection unit 200. The depositor can then return to the platform 523 so as not to interfere with the next process, namely the scanning cycle. In the scanning cycle, a laser beam source 506 (which uses a Cartesian coordinate system) is used under the control of code and / or electronic hardware, which can use a Cartesian coordinate system as a reference for performing the scanning cycle.A laser beam source 506 (which in other printers may instead be an electron beam source) sends a laser beam onto a mirror 508 or other reflective, movable lens. The laser light 507 is deflected so that it strikes selected areas of the powder corresponding to the first slice, effectively melting them. Areas of the powder that do not represent cross-sectional areas of the structure are not scanned. The scanned areas melt upon laser impact and then quickly fuse together to form a cross-section of the first slice.

[0073] Before the depositor deposits another layer corresponding to the second slice, the controller may move the substrate downward slightly using a piston 520. After each deposition and scanning cycle, the substrate is moved downward by small but equal amounts. This movement allows the object to be printed, also referred to as a part 516, to become larger as more layers are used. This movement also creates a powder reservoir 512 located in an area between the top of the powder bed 512 and one side (cropped for illustration) of the 3D printer wall 514. In some cases, the controller and extensive electronic circuitry may also be integrated into the 3D printer 500, below the platform and within the body of the 3D printer, as defined by the wall 514, in an internal rectangular area.In other embodiments, platform 523 may instead include a second powder bed that uses a roller to evenly roll each layer of powder onto powder bed 512. The embodiment of . Fig. 5, however, focuses on the design of the caster.

[0074] After excess powder has been removed from the hopper 502 via channel 504, the caster 510 applies another layer and returns to the platform 523. The controller then uses the position data in the second disk to scan the areas of the powder with the laser beam 507 that will become part of the component 516. The mirror 508 is precisely controlled by a controller, as it is responsible for directing the laser beam to the correct position on the powder layer.

[0075] This process is repeated slice by slice, or layer by layer, until the component 516 (here, the integrated fuel cell injection unit 200) is complete. In some embodiments, the printing process can be interrupted. This interruption may be desirable, for example, if the manufacturer wishes to incorporate a custom injection into the integrated fuel cell injection unit 200 or a custom pressure sensor along with the associated electronics (e.g., semiconductors, low-resistance metallic traces, etc.). In some embodiments, the print is suspended multiple times to allow for the insertion of various components into the integrated fuel cell injection unit 200, including non-metals or other materials. In some printer designs, multiple printing materials can be used.In some 3D printers, another substance, such as a gel or liquid, can be used instead of metal powder.

[0076] As in Fig. As shown in Figure 5, the 3D printing process (also referred to as additive manufacturing) is very advantageous because the printer 500 can integrate the various features of the integrated fuel cell injection unit 200 into a single body. For example, the 3D printer is capable of producing TPMS grilles, nozzles, tubes of various selected geometries, and many other structures. The 3D printer is geometrically very diverse. In this case, the 3D printer eliminates many, if not most, subtractive manufacturing processes, such as machining, molding, extrusion, forging, die casting, etc. These processes are not only expensive but also inflexible. A mold, for example, can only produce a single shape. In contrast, the geometric shapes that can be produced with a 3D printer 500 are limited primarily by the imagination of the manufacturer.

[0077] Fig. 6 is an exemplary flowchart 600 of a method for additive manufacturing of an integrated fuel injection unit according to one aspect of the description. The steps in Fig. 6 can be performed with a variety of 3D printers, including the Powder Bed Fusion (PBF) 500 3D printer from Fig. 5 and the many PBF variants. In order not to blur the concepts of the description, the steps are not positioned in any particular order and refer to the additive manufacturing of different components. Therefore, Fig. 6 the individual processes of 3D printers are not shown, at least because such printers can differ greatly in their functionality, but can be suitable for the additive manufacturing of the integrated fuel cell injection unit 200.

[0078] In logic block 602, the 3D printer may form a body with a cylindrical shape (or other suitable shape) to define a sound attenuation volume. This volume may be defined by the walls of the body 314 ( Fig. 3) and other sound dampening components. In logic block 604, the 3D printer can also gradually print a Venturi tube into the body of the component 516 (for example, in slices, as described above with reference to Fig. 5). The venturi tube can be printed to have a directional component extending longitudinally of the body, allowing the venturi tube to form a stacked anode inlet at its end.

[0079] According to logic block 606, the 3D printer can print an ejection nozzle whose outlet is aligned with the Venturi tube to selectively inject hydrogen into the Venturi tube. It's worth noting that in powder bed fusion processes, some or all of these components can be formed at least partially simultaneously due to the layered nature of the printing and the cross-sectional laser scanning. For this reason at least, the printing steps are not positioned in a specific chronological order.

[0080] In logic block 608, the 3D printer can enclose the ejection nozzle in a gap extending to an opening in a surface of the body to recover unused hydrogen. In the context of a PDF 3D printer 500, one way to accomplish this step is to leave the relevant geometric portions of the CAD file corresponding to the gap blank, so that during cutting, the areas corresponding to the gap are not scanned with the laser beam. This way, the finished part will contain a gap full of loose powder that can be removed using various techniques.

[0081] In logic block 610, the 3D printer can integrate a heat exchanger into the sound-damping volume. Again, this process can involve creating a CAD representation of the heat exchanger within the body. The 3D printer can print the grid and the body simultaneously in some areas, with the unit cell grid being incorporated using precision laser or electron beam scanning.

[0082] At logic block 612, the 3D printer may form an opening and a receptacle for mounting a custom injector to control hydrogen flow. In some embodiments, the receptacle and / or the injector may be fully or partially custom-designed. For example, the container or injector may be a custom item or a commercially available (COTS) item rather than additively manufactured. If the container is additively manufactured but the injector is custom-designed, the 3D printer may produce the integrated fuel cell injection unit 200 with one or more recesses on the bottom to accommodate the respective injectors. After removing the dust powder from the finished part and post-processing (polishing, applying fluids, etc.), the manufacturer can insert a custom injector through the opening on the underside of component 516 and ensure that the injector is firmly seated in the receptacle. In some cases, glues or adhesives can be used to ensure that a custom injector is properly coupled to the receptacle and opening. In other cases, the injector is additively manufactured or partially additively manufactured. It may be advantageous to interrupt the printing process shortly after the opening is created so that off-printing steps to seal or secure the injector can be easily performed before resuming the printing process to complete the integrated fuel cell injection unit 200.

[0083] A further advantage of the principles described here is that, unlike conventional manufacturing processes, where sharp edges and awkward angles are often difficult or impossible to avoid, the resolution of modern 3D printers is extremely high and the geometric resolution of print jobs is so precise that a wide variety of shapes can be produced. Sharp edges and awkward angles present in current fuel injection units can be eliminated using many existing additive manufacturing techniques, including those described here.

Claims

[1] Additively manufactured hydrogen fuel cell injection unit (200), comprising: a body (314) having a noise dampening volume integrated therein, a first end (324) of the body (314) having an opening (356) for mounting an injector (391); an ejection assembly (388) having an ejection tube (390) and a stacked anode inlet (312) positioned at a second end (321) of the body (314), the stacked anode inlet (312) configured to inject hydrogen into a fuel cell; a heat exchanger (336) integrated into the noise dampening volume and having a triply periodic minimum surface area (TPMS) lattice of unit cells arranged therein, the TPMS lattice being configured to heat hydrogen flowing therethrough, each end surface of the heat exchanger (336) being separated from the first and second ends (324, 321) of the body (314) by a corresponding volume; and an ejection nozzle (344) coupled to the interior of the body (314) and aligned with the injector (391) near the first end (324) of the body (314), the ejection nozzle (344) being surrounded by a gap (342), the gap (342) leading to a recirculation path inlet (320) of the body (314) for recapturing residual hydrogen near the recirculation path inlet (320), wherein the ejection tube (390) extends through the heat exchanger (336) and is aligned with the ejection nozzle (344) such that the ejection tube (390) conducts hydrogen through the stack anode inlet (312). [2] The fuel cell injection unit (200) of claim 1, wherein the hydrogen passing from the stacked anode inlet (312) to the fuel cell comprises (1) the pressurized hydrogen originating from the injection (391), (2) the residual hydrogen near the recirculation path inlet (320), and (3) the hydrogen exiting the heat exchanger (336). [3] Fuel cell injection unit (200) according to claim 1, wherein: the second end (321) of the body (314) has an inlet coupled to a hydrogen source; the volume between a first end surface of the heat exchanger (336) and the first end (324) of the body (314) is a first volume (340); the volume between a second end surface (350) of the heat exchanger (336) and the second end (321) of the body (314) is a second volume (338); and the second end surface (350) of the heat exchanger (336) is shaped in a geometric gradient configured to enable the hydrogen received from the inlet at the second end (321) of the body (314) to be evenly distributed in the second volume (338) as it enters and passes through the heat exchanger (336) to enable a uniform heat rise of the hydrogen. [4] Fuel cell injection unit (200) according to claim 1, wherein: a first end surface of the heat exchanger (336) and the first end (324) of the body (314) define a first volume (340) into which heated hydrogen exiting the heat exchanger (336) flows; and the first end surface of the heat exchanger (336) is shaped to form a gradient for a more even distribution of the heated hydrogen as the heated hydrogen passes from the heat exchanger (336) into the first volume (340). [5] Fuel cell injection unit (200) according to claim 4, wherein the gradient is at least partially conical in shape. [6] Additively manufactured fuel cell injection unit (200), comprising: a body (314) having a noise dampening volume therein; a first end (324) of the body (314) containing an opening (356) for mounting a hydrogen injector (391); an ejection assembly (388) having an ejection tube (390) coupled to a stacked anode inlet (312), the stacked anode inlet (312) positioned at a second end (321) of the body (314) for injecting hydrogen into a fuel cell; a heat exchanger (336) comprising a grid of unit cells integrated into the noise attenuation volume, the grid configured to heat hydrogen flowing therethrough, each end surface of the heat exchanger (336) being separated from the first and second ends (321) of the body (314) by a corresponding volume, an end surface of the heat exchanger (336) being adjacent to each corresponding volume, and including a gradient; an ejection nozzle (344) coupled to an outlet of the injector (391) at the first end (324) of the body (314), the ejection nozzle (344) being surrounded by a gap (342), the gap (342) leading to a recirculation path inlet (320) of the body (314) for recapturing excess hydrogen; and an exhaust tube (390) extending through the heat exchanger (336) and aligned with the exhaust nozzle (344) such that the exhaust tube (390) is configured to direct hydrogen to the fuel cell via the stack anode inlet (312). [7] The fuel cell injection unit (200) of claim 6, wherein one or both end surfaces of the heat exchanger (336) adjacent to the respective volumes are at least partially conical in shape. [8] The fuel cell injection unit (200) of claim 6, wherein the injector (391) is selectively activatable to inject hydrogen from a source into the ejection nozzle (344), to eject hydrogen from the stacked anode inlet (312) into the fuel cell via the ejection tube (390), and to create a low pressure region in the gap (342) to recapture the excess hydrogen. [9] Method for additively manufacturing a fuel injection unit, comprising: Forming a body (314) having at least a partially cylindrical shape and defining a sound attenuation volume therein; Printing a venturi tube (390) extending longitudinally along at least a portion of the body (314) from a first end (324) to a second end (321), a stack anode inlet (312) at the second end (321) for injecting hydrogen into a fuel cell; printing an ejection nozzle (344) aligned with the venturi tube (390) at the first end (324) to selectively inject hydrogen into the venturi tube (390); Enclosing the ejection nozzle (344) in a gap (342) extending to an opening in a surface of the body (314), the gap (342) serving to recover unused hydrogen for emission via the ejection nozzle (344) and the venturi tube (390) into the stack anode inlet (312); Integrating a heat exchanger (336) into the sound attenuation volume, the heat exchanger (336) comprising a grid of unit cells disposed between the venturi tube (390) and a periphery of the body (314) such that a first end surface of the heat exchanger (336) adjacent to the first end (324) has a gradient defining a first volume (340) at the first end (324), and a second end surface (350) of the heat exchanger (336) adjacent to the second end (321) has a gradient defining a second volume (338) with the second end (321), wherein hydrogen entering an inlet opening in the second end surface (350) flows through the heat exchanger (336) from the second volume (338) to the first volume (340); and Forming an opening (356) in the first end (324) for mounting an injector (391), the injector (391) being configured to selectively deliver hydrogen from the first volume (340) and from an injector (391) through the ejection nozzle (344) and into the venturi tube (390) for entry into the fuel cell at the stack anode inlet (312). [10] The method of claim 9, wherein the body (314) further comprises a coolant inlet for injecting coolant into a channel (336a, 336b) of the heat exchanger (336), and a coolant outlet for receiving the coolant from the heat exchanger (336).

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