Reactant feed and return assembly for fuel cell stacks including nozzle structure

Abstract

To provide: a reactant feed and return assembly, such as an anode splitter plate (ASP), for facilitating a reactant feed flow in a solid oxide fuel cell (SOFC) stack system; and a fuel cell stack system comprising the same.SOLUTION: Embodiments include a reactant feed and return assembly 15 including at least one nozzle structure 903-1 along a flow path of a reactant feed to a fuel cell stack. The at least one nozzle structure may have a width dimension that decreases along the flow path of the reactant. The at least one nozzle structure of the assembly may accelerate the reactant feed as the reactant feed enters the adjacent fuel cell stack, and may provide the reactant feed with sufficient kinetic energy to negate the effects of an increase in viscous resistance along the reactant flow path through the fuel cell stack.SELECTED DRAWING: Figure 8C

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate generally to fuel cell systems, and more particularly to a supply return assembly including a nozzle. [Background technology]

[0002] A fuel cell is an electrochemical device that can convert energy stored in a fuel into electrical energy with high efficiency. An electrolysis cell is an electrochemical device that can use electrical energy to reduce a given substance, such as water, to generate a fuel, such as hydrogen. Fuel cells and electrolysis cells can include reversible cells that operate in both fuel cell and electrolysis modes.

[0003] In high-temperature fuel cell systems, such as solid oxide fuel cell (SOFC) systems, an oxidizing stream passes through the cathode side of the fuel cell and a fuel stream passes through the anode side of the fuel cell. The oxidizing stream is typically air, and the fuel stream can be a hydrocarbon fuel, such as methane, natural gas, hydrogen, propane, ethanol, or methanol. When the fuel cell operates at typical temperatures between 750°C and 950°C, oxygen is allowed to combine with free hydrogen, leaving excess electrons behind. The excess electrons are directed back to the cathode side of the fuel cell through an electrical circuit completed between the anode and cathode, resulting in the flow of electrical current through the circuit.

[0004] Fuel cell stacks can be internally or externally manifolded for fuel and air. In an internally manifolded stack, fuel and air are distributed to each cell using risers contained within the stack. In other words, gas flows through openings or holes in each fuel cell's support layer, such as the electrolyte layer, and through each cell's gas separator. In an externally manifolded stack, the stack is open to fuel and air inlet and outlet sides, and the fuel and air are introduced and collected independently of the stack hardware. For example, the inlet and outlet fuel and air flow in separate channels between the stack and the manifold housing in which the stack is located. Some fuel cell stacks can be internally manifolded for a first reactant (e.g., fuel) and externally manifolded for a second reactant (e.g., air).

[0005] A fuel cell power generation system may include one or more fuel cell stacks and a distribution system that provides reactant flow streams to the appropriate locations of each fuel cell in the stack(s) and removes exhaust streams from the fuel cells and stack(s). Summary of the Invention

[0006] One embodiment includes a reactant supply and return assembly for a fuel cell stack system, comprising: a reactant supply opening in the reactant supply and return assembly; a reactant exhaust opening in the reactant supply and return assembly; a reactant supply channel in the reactant supply and return assembly fluidly connected to a reactant supply conduit; at least one nozzle structure fluidly connected to the reactant supply channel and an inlet riser channel of the fuel cell stack, the at least one nozzle structure having a width dimension that decreases along the direction of reactant flow through the at least one nozzle structure to the inlet riser channel; and a reactant exhaust channel in the reactant supply and return assembly fluidly connected to a reactant exhaust conduit.

[0007] A further embodiment includes a column including at least a first fuel cell stack and a second fuel cell stack, and a reactant supply / return assembly positioned within the column between the first and second fuel cell stacks, the reactant supply / return assembly being in fluid communication with the first and second fuel cell stacks and configured to provide a reactant feed to and receive a reactant exhaust therefrom, respectively, the reactant supply / return assembly including at least one nozzle structure along a flow path of the reactant feed, the at least one nozzle structure having a width dimension that decreases along the direction of the reactant feed flow path. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of a prior art SOFC stack assembly. [Figure 2] FIG. 2 is a perspective view of a prior art SOFC stack. [Figure 3] FIG. 3 is a schematic cross-sectional side view of a prior art SOFC stack. [Figure 4] FIG. 4 is a cross-sectional side view of a prior art SOFC stack. [Figure 5A] FIG. 5A is a perspective view of prior art fuel flow in a SOFC end plate. [Figure 5B] FIG. 5B is a perspective view of prior art fuel flow in an SOFC end plate. [Figure 6A] FIG. 6A is an exploded view of a reactant supply and return assembly used in a column of a SOFC stack. [Figure 6B] FIG. 6B is a perspective view showing a reactant supply and return assembly and a SOFC stack positioned on top of the reactant supply and return assembly. [Figure 7] FIG. 7 is a plot of the temperature profile as a function of column height for a pair of fuel cell stacks separated in a column by the anode reactant supply and return assembly of FIG. 6B. [Figure 8A]FIG. 8A is a top perspective view of an anode reactant supply and return assembly according to one embodiment of the present disclosure. [Figure 8B] FIG. 8B is a partial cutaway view of the assembly showing region B of FIG. 8A. [Figure 8C] FIG. 8C is a partial cross-sectional side view of the assembly taken along line CC' of FIG. 8A. [Figure 9] FIG. 9 is a partial cross-sectional side view of an anode reactant supply and return assembly according to one embodiment of the present disclosure. [Figure 10] FIG. 10 is a plot showing comparative fuel utilization (FU) distributions of fuel cell stacks as a function of column height using a comparative anode supply and return assembly and an anode supply and return assembly according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and, together with the general description above and the detailed description below, serve to explain features of the invention.

[0010] 1 is a partially exploded perspective view of a prior art SOFC stack assembly 200. In this embodiment, the SOFC stack assembly 200 includes multiple fuel cell stacks 14 that are internally manifolded for fuel and externally manifolded for air, although it will be appreciated that other configurations may be utilized, such as an internally manifolded system for air and manifolded for fuel, or an internally manifolded system for both fuel and air.

[0011] As shown in FIG. 1 , wedge-shaped ceramic side baffles 220 (e.g., having a horizontally non-uniform thickness and a roughly triangular cross-sectional shape) are positioned between adjacent fuel cell stacks 14 (or fuel cell stack columns 201). One of the fuel cell stacks 14 (or fuel cell stack columns 201) is enclosed by area A. The baffles 220 function to direct the cathode feed into the cathode flow path and to fill the space between adjacent stacks, so that the cathode feed passes through each of the stacks 14 rather than bypassing the longitudinal sides of the stacks 14. The baffles 220 are held in place by tie rods 222 passing through tight-fitting bores 224 located in the center of each baffle 220. The baffles 220 are preferably non-conductive and fabricated as a single, integral piece from a suitable ceramic material. FIG. 1 also shows the fuel distribution manifold between the stacks in the stack column, and the fuel inlet and exhaust conduits connected to the manifold. Those skilled in the art will appreciate that the embodiments described below are not limited to use in the particular assembly configuration shown in FIG.

[0012] FIG. 2 is a perspective view of a column 201 including one or more fuel cell stacks 14, such as those shown in region A of FIG. 1. FIG. 2 illustrates multiple fuel cell stacks 14, each including a vertically stacked fuel cell. The column 201 can include at least one supply / return assembly 15 for reactants. For example, in the case of an internally manifolded fuel cell system for fuel, the supply / return assembly 15 can be referred to as an anode supply / return assembly 15. The anode supply / return assembly 15 can be coupled to an anode supply port (not shown in FIG. 2) and can direct the anode feed (e.g., a fuel-containing reactant stream) into one or more fuel cell stacks 14, collect the anode exhaust from the corresponding fuel cell stack 14, and direct the anode exhaust into an exhaust port (not shown in FIG. 2). The anode supply / return assembly 15 can have a plate-shaped portion located within the column 201, such as between the two fuel cell stacks 14 shown in FIG. 2, and can also have a fluid connector port at a protrusion 808 extending from the column. The anode supply / return assembly 15 can direct anode feed to, and collect anode exhaust from, multiple fuel cell stacks 14 located above and below the anode supply / return assembly 15 within the column 201. Such an anode supply / return assembly 15 can also be referred to as an anode splitter plate (ASP). Any number of ASPs 15 can be provided between adjacent fuel cell stacks 14 as desired. Furthermore, the number of fuel cell stacks 14 within the column 201 and / or the number of fuel cell stacks 14 between each ASP 15 can be selected as desired and is not limited to the configuration shown in FIG. 2.

[0013] FIG. 3 is a schematic cross-sectional side view of a prior art column 201, illustrating the reactant flow paths through the ASP 15 and multiple fuel cell stacks 14-1, 14-2. Fuel flow is indicated by solid black arrows 160. Fuel is shown initially entering the ASP 15 at a first side 301 of the column 201, where it is distributed vertically through the stacks 14-1, 14-2 (e.g., into inlet riser channels 16a that extend through each stack 14-1, 14-2). As the fuel travels from left to right in FIG. 3 through each stack 14-1, 14-2, at least a portion of the fuel in the reactant stream reacts in the fuel cells to generate electricity. As indicated by solid black arrows 170, the exhaust streams containing reaction products and any unreacted fuel are then directed from various locations along the vertical axis of the right side of stacks 14-1, 14-2 (e.g., through outlet riser channel 16b) to ASP 15, where they exit the second side of column 201. ASP 15 thus manages the incoming and outgoing reactant flows 160, 170.

[0014] While FIG. 3 depicts the fuel and exhaust streams entering and exiting the column 201 at opposite sides 301, 303 of the column 201, it will be understood that in various embodiments, the fuel and exhaust streams can enter and exit the column 201 on the same side, such as the configuration shown in FIG. 2. The ASP 15 can include an internal conduit (not shown in FIG. 3 ) that directs the fuel stream 160 from the first side 301 of the column 201 into the inlet riser channel 16 a of each of the stacks 14-1, 14-2. The ASP 15 can also include another internal conduit (not shown in FIG. 3 ) that directs the exhaust stream 170 from the outlet riser channel 16 b of each of the stacks 14-1, 14-2 through the ASP to the first side 301 of the column 201, where the exhaust stream 170 can exit the column 201. The internal conduits of the ASP can lie at least partially in different planes (i.e., planes facing into and out of the page of FIG. 3 ).

[0015] FIG. 4 is a cross-sectional view of a portion of a prior art column 201 including multiple SOFC stacks 14-1, 14-2 and an ASP 15. The column 201 shown in FIG. 4 is rotated 90 degrees about a vertical axis from the column 201 shown in FIG. 3. Each SOFC 1 in the stacks 14-1, 14-2 includes a cathode electrode 7, a solid oxide electrolyte 5, and an anode electrode 3. Fuel cell stacks are often constructed from multiple SOFCs 1 in the form of planar elements, tubes, or other geometric shapes. Furthermore, although a vertical stack is shown in FIG. 4, the fuel cells may be stacked horizontally or in any other suitable orientation between vertical and horizontal. The primary function of a fuel cell stack is to provide fuel and air to an electrochemically active surface, which may be large in area.

[0016] Gas flow separators 9 (referred to as gas flow separator plates when part of a planar stack), containing gas flow passages or channels 8 between ribs 10, separate the individual cells in the stack. Often, the gas flow separator plates 9 are also used as interconnects, electrically connecting the anode or fuel electrode 3 of one cell to the cathode or air electrode 7 of an adjacent cell. In this case, the gas flow separator plates functioning as interconnects are made of or contain a conductive material. The interconnect / gas flow separator 9 separates a fuel, such as a hydrocarbon fuel, flowing to the fuel electrode (i.e., anode 3) of one cell in the stack from an oxidant, such as air, flowing to the air electrode (i.e., cathode 7) of an adjacent cell in the stack. At either end of a portion of the stack 14, there may be an air end plate 11a or a fuel end plate 11b, which provide air or fuel, respectively, to the end electrodes. The ASP 15 is located between the fuel cell stacks 14-1 and 14-2 and can contact the air or fuel end plate 11a of the first fuel cell stack 14-1 and the air or fuel end plate 11b of the second fuel cell stack 14-2.

[0017] Figures 5A and 5B are perspective views showing reactant flow in the SOFC end plates 11a and 11b. Figure 5A shows the top surface of the air end plate 11a shown in Figure 4, and Figure 5B shows the bottom surface of the fuel end plate 11b shown in Figure 4. That is, the sides of the end plates 11a and 11b that are not visible in Figures 5A and 5B are substantially flat and, when installed in the SOFC stacks 14-1 and 14-2 shown in Figure 4, can directly contact the ASP 15 (not shown).

[0018] The portion of the end plates 11a, 11b shown in cross-sectional side view in FIG. 4 is taken along line AA in FIGS. 5A and 5B. Referring first to FIG. 5B, the fuel end plate 11b includes gas flow passages or channels 8 between the ribs 10 to direct fuel flow. The fuel end plate 11b in this embodiment has at least one riser channel 16a, as indicated by arrow 29, that provides fuel to the anode side of the SOFC. The riser channel 16a generally has a fuel inlet riser opening or hole that penetrates at least one layer of fuel cells and interconnects within the stack. As shown in FIG. 5B, fuel can flow through the inlet riser channel 16a to the anode side of each fuel cell. Here, the fuel can collect in an inlet plenum 17a (e.g., a groove in the surface of the interconnect) and flow across the fuel cell anode 3, through gas flow channels 8 formed in the fuel end plate 11b, to an outlet plenum 17b, and exit through a separate outlet riser channel 16b.

[0019] The air end plate 11a shown in FIG. 5A can have gas flow passages or channels 8 between ribs 10 that direct airflow 44 across the cathode electrodes of the fuel cells. Seals 15a, 15b can seal the respective risers 16a, 16b on the cathode side of the interconnect and fuel cells to prevent fuel from reaching the cathode electrodes of the fuel cells. The seals can have a donut or hollow cylindrical shape, as shown, with the risers 16a, 16b penetrating the hollow central portions of the respective seals 15a, 15b. The seals 15a, 15b can have a raised top surface that contacts the flat surface of the adjacent SOFC. A peripheral seal 15c can seal the anode side of the fuel cell to prevent air from reaching the anode electrodes of the fuel cells. The seals 15a-15c can include a glass material. Any of the glass seals 15a-15c can provide sufficient pneumatic isolation of the fuel from the air.

[0020] FIG. 6A is an exploded view of a reactant supply / return assembly 15 that can be used in a column 201 including multiple SOFC stacks 14-1, 14-2, such as that shown in FIG. 4. In this example, the reactant supply / return assembly is an anode splitter plate (ASP). The ASP 15, as shown in FIG. 6A, can be formed by joining multiple plates together via a suitable joining process, such as a welding or brazing process. The ASP can include two or more plates joined together, such as the three plates 804A, 804B, and 804C shown in FIG. 6A. It will be understood that the ASP 15 can include four or more plates joined together. Alternatively, the ASP 15 can include a single, integral plate member and can include suitable openings and fluid channels within the plate member, as described below.

[0021] In some ASPs, one or more of the plates 804A, 804B, and 804C forming the ASP may have a segmented structure, with gaps between the segments of each of the plates 804A, 804B, and 804C, allowing the segments to "float" independently of one another. FIG. 6B is a perspective view of an assembled ASP 15 and an SOFC stack 14-1 positioned on top of the ASP 15, where the top plate 804A of the ASP 15 has multiple segments 701 and 702 with gaps 703 between the segments 701 and 702. This segmented structure may help reduce thermal stresses on adjacent components of the SOFC stacks 14-1 and 14-2 during thermal cycling. Optionally, a sealing material may fill the gaps 703 between adjacent segments of the APS plate(s) 804A.

[0022] Plates 804A, 804B, and 804C of ASP15 can be formed from a durable, electrically conductive material that exhibits good resistance to high-temperature oxidation and corrosion, such as grade 446 stainless steel (SS446) sheet metal or Inconel™ alloy. Each of plates 804A, 804B, and 804C of ASP15 can be formed from the same material or different materials. In some embodiments, ASP15 can be formed from different materials having different coefficients of thermal expansion (CTE), as described in U.S. Pat. No. 10,511,047, which is incorporated herein by reference. In particular, the outermost portions of ASP 15 (e.g., plates 804A and 804B) can be formed from a material having a CTE between the CTE of the inner portions of ASP 15 (e.g., plate 804C) and the CTE of adjacent components of SOFC stacks 14-1, 14-2, such as end plates 11a, 11b (e.g., Cr-Fe alloy plates) of SOFC stacks 14-1, 14-2. In some embodiments, all or a portion of ASP 15 can include a Cr-Fe alloy and can be fabricated using a sheet metal or powder metallurgy (PM) process.

[0023] ASP 15 may have inlet riser openings that may be comprised of openings 812a, 812b, and 812c formed through plates 804A, 804B, and 804C, respectively, such that when plates 804A, 804B, and 804C are joined together, openings 812a, 812b, and 812c form a continuous fluid passageway through ASP 15 through which reactants (e.g., fuel) can flow. ASP 15 may also have outlet riser openings that may be comprised of openings 814a, 814b, and 814c formed through plates 804A, 804B, and 804C, respectively, such that when plates 804A, 804B, and 804C are joined together, openings 814a, 814b, and 814c form a continuous fluid passageway through ASP 15 through which exhaust streams can flow. The inlet and outlet riser openings of the ASP 15 may be aligned with the riser channels 16a, 16b of the SOFC stacks 14-1, 14-2, as shown in FIG. 6B.

[0024] Each of the plates 804A, 804B, and 804C may also have a protrusion 808 extending from a side of the plate 804A, 804B, and 804C. The protrusions 808 may be configured to extend from the column 201 of the fuel cell stack 14 when the ASP15 is assembled into the SOFC system, as shown in FIG. 2. Each protrusion 808 may have a pair of openings 806 and 807 extending therethrough, such that when the plates 804A, 804B, and 804C are joined together, the openings 806, 807 form a pair of continuous fluid passageways through the protrusion 808 of the ASP15. The openings 806 may provide a reactant supply opening for the ASP15, and the openings 807 may provide a reactant exhaust opening for the ASP15.

[0025] Plate 804C can have an open area 815 extending continuously between opening 806 and opening 812c, such that when plates 804A, 804B, and 804C are joined together, open area 815 can form a first internal conduit extending between reactant supply opening 806 and inlet riser openings 812a-c of ASP15. Plate 804C can also have an open area 816 extending between opening 807 and opening 814c, such that when plates 804A, 804B, and 804C are joined together, open area 816 can form a second internal conduit extending between reactant exhaust opening 807 and outlet riser openings 814a-c of ASP15. A reactant (e.g., anode) supply pipe 817 can be joined to or integrally formed with a protrusion 808 of ASP15 above the reactant supply opening 806, and a reactant exhaust pipe 818 can be joined to or integrally formed with a protrusion 808 of ASP15 above the reactant exhaust opening 807.

[0026] Reactants (e.g., fuel) from reactant supply pipe 817 can flow into reactant supply opening 806 in protruding portion 808 of ASP 15 and through first internal fluid conduit 815 to inlet riser openings 812a-812c. From there, the reactants can flow through inlet riser openings 812a-812c into inlet riser channels 16a of fuel cell stacks 14-1 and 14-2 located above and below ASP 15 within column 201 (see FIG. 2). Reactant (i.e., anode) exhaust from fuel cell stacks 14-1 and 14-2 can flow from outlet riser channels 16b of fuel cell stacks 14-1 and 14-2 to outlet riser openings 814a-814c of ASP 15, through second internal fluid conduit 816, to reactant exhaust opening 807 in protruding portion 808 of ASP 15, and exit through reactant exhaust pipe 818.

[0027] 2, a column 201 of fuel cell stacks 14 may include a reactant supply / return assembly 15, such as the ASP 15 shown in Figures 6A and 6B, that provides reactants (i.e., fuel) to and removes reactant exhaust from a pair of fuel cell stacks 14-1, 14-2 located above and below the reactant supply / return assembly 15 in the column 201. Thus, each fuel cell stack 14 in the column 201 may abut against the reactant supply / return assembly 15 at one end of the fuel cell stack 14 (e.g., at the ASP-to-stack interface), and some of the fuel cell stacks 14 in the column 201 may abut against another fuel cell stack 14 in the column 201 at the other end of the fuel cell stack 14 (i.e., at the stack-to-stack interface).

[0028] In the SOFC stack assembly 200 shown and described with reference to FIGS. 1-6B, the temperature of the fuel cell stack 14 is not uniform. Typically, the temperature within the fuel cell stack 14 increases as a function of distance from an adjacent reactant supply / return assembly 15 (e.g., distance from the ASP-to-stack interface). The highest temperature within the fuel cell stack 14 often occurs at the interface between the fuel stack 14 and the adjacent fuel cell stack (i.e., the stack-to-stack interface). This is illustrated in FIG. 7. Specifically, FIG. 7 shows a temperature profile 701 for a pair of fuel cell stacks 14-1, 14-2 separated by an ASP 15 in a column. The lowest stack temperature occurs adjacent the ASP, and stack temperature increases as a function of distance from the ASP, reaching a maximum at the opposite end of the stack where the stack abuts the adjacent stack in the column. This large difference in stack temperature can also result in undesirable variations in fuel utilization (FU) across the fuel cell stack. In particular, the viscous resistance to fuel flow within a fuel cell stack increases with increasing stack temperature, such that at high stack temperatures near the stack-to-stack interface, the fuel (e.g., hydrogen fuel) lacks sufficient kinetic energy to overcome the increased viscous resistance. Therefore, less fuel is available to flow to the fuel cells near the stack-to-stack interface, and more fuel flows to the fuel cells nearest the ASP. This can result in a higher fuel utilization (FU) near the stack-to-stack interface of the fuel cell stack than near the ASP-to-stack interface, which in some cases can lead to fuel starvation in one or more fuel cells of the stack near the stack-to-stack interface.

[0029] Various embodiments of the present disclosure relate to a reactant supply / return assembly, such as an anode splitter plate (ASP), that can minimize the effects of increased viscous drag along a reactant (e.g., fuel) flow path in a fuel cell stack. In one embodiment, the fuel can include hydrogen. In another embodiment, the fuel can include a hydrocarbon fuel, such as natural gas, pentane, or methane, or a mixture of hydrogen and a hydrocarbon fuel. In various embodiments, the reactant supply / return assembly can include at least one nozzle structure, e.g., a pair of nozzle structures, in the reactant feed flow path(s) to an adjacent fuel cell stack(s). Each nozzle structure of the assembly can include a gradually decreasing width dimension of the nozzle structure along the direction of the reactant feed flow path. The nozzle structure(s) can be configured to accelerate the reactant feed as it enters an adjacent fuel cell stack, providing the reactants with sufficient kinetic energy to counteract the effects of increased viscous drag along the reactant flow path through the fuel cell stack.

[0030] FIG. 8A is a top perspective view of an anode reactant supply and return assembly 15 according to one embodiment of the present disclosure. FIG. 8B is a partial cutaway view of the assembly 15 showing region B of FIG. 8A. FIG. 8C is a partial side cross-sectional view of the assembly 15 taken along line C-C' of FIG. 8A. Referring to FIGS. 8A-8C, the anode reactant supply and return assembly 15 can be an anode splitter plate (ASP) as shown and described with reference to FIGS. 6A and 6B. One or more ASPs 15 shown in FIGS. 8A-8C can be positioned between two fuel cell stacks 14 in a column 201, such as stacks 14-1 and 14-2 shown in FIGS. 2, 3, and 4. A first surface 901 of the ASP can face the first fuel cell stack 14-1 (see FIG. 3) of the column 201, and a second surface 902 can face the second fuel cell stack 14-2 of the column 201. In some embodiments, the first surface 901 and the second surface 902 of the ASP 15 can be in direct contact with the end plates 11 a, 11 b of the respective fuel cell stacks 14-1 and 14-2. The ASP 15 can have an inlet riser opening 812 and an outlet riser opening 814 that can extend through the ASP 15. When the ASP 15 is located within the column 201, the inlet riser opening 812 of the ASP 15 can be in fluid communication with the inlet riser channel 16 a of each of the adjacent fuel cell stacks 14-1 and 14-2. Additionally, the outlet riser opening 814 of the ASP 15 can be in fluid communication with the outlet riser channel 16 b of each of the adjacent fuel cell stacks 14-1 and 14-2. Thus, the inlet riser opening 812 through the ASP 15 can provide a fluid channel continuous with the inlet riser channel 16 a of the fuel cell stack 14 manifolded within the column 201, and the outlet riser opening 814 through the ASP 15 can provide a fluid channel continuous with the outlet riser channel 16 b of the fuel cell stack 14 manifolded within the column 201.

[0031] The ASP 15 may have a protrusion 808 that may extend laterally from the column 201 of the fuel cell stack 14 when the ASP 15 is positioned within the column 201. The protrusion 808 may have a reactant supply opening 806 extending therethrough and a reactant outlet opening 807 extending therethrough. A first internal fluid conduit 815 within the ASP 15 may extend between the reactant inlet opening 806 and the inlet riser opening 812. A second internal fluid conduit 816 may extend between the reactant outlet opening 807 and the outlet riser opening 814 within the ASP. A pair of reactant supply pipes (not shown in FIGS. 8A-8C ) may be coupled to the protrusion 808 on the first and second surfaces 901, 902 of the ASP 15 and may be fluidly connected to the reactant inlet opening 806. Additionally, a pair of reactant exhaust tubes (not shown in Figures 8A-8C) can be coupled to protrusions 808 on the first surface 901 and second surface 902 of the ASP and can be fluidly connected to the reactant exhaust openings 807.

[0032] Thus, during operation of the SOFC stack assembly, reactants (e.g., fuel) from the reactant supply tubes can enter reactant supply openings 806 and flow through first internal fluid conduits 815 to inlet riser openings 812. As shown in the cross-sectional view of FIG. 8C , when the reactant stream (indicated by solid black arrows 160) reaches inlet riser openings 812, the reactant stream can split, with a first portion of the reactant stream (indicated by arrow 160-1) flowing in a first direction through inlet riser openings 812 and exiting ASP15 through outlet 906 at first (e.g., upper) surface 901 of ASP15, and a second portion of the reactant stream (indicated by arrow 160-2) flowing in a second direction through inlet riser openings 812 and exiting ASP15 through outlet 907 at second (e.g., lower) surface 902 of ASP15. Portion 160-1 of the reactant flow exiting ASP15 through outlet 906 can enter inlet riser channel 16a (shown in dashed lines in FIG. 8C) of fuel cell stack 14-1, and portion 160-2 of the reactant flow exiting ASP15 through outlet 907 can enter inlet riser channel 16a (shown in dashed lines in FIG. 8C) of fuel cell stack 14-2.

[0033] In various embodiments, the inlet riser opening 812 of the ASP 15 may comprise at least one nozzle structure, and preferably a pair of nozzle structures 903-1 and 903-2 located within the reactant flow path(s) through the inlet riser opening 812. Referring to FIG. 8C , the first nozzle structure 903-1 may be defined by a tapered sidewall 908 of the inlet riser opening 812, where the width dimension of the inlet riser opening 812 may gradually decrease along the direction of the reactant flow 160-1 toward an outlet 906 at the first (e.g., upper) surface 901 of the ASP 15. The second nozzle structure 903-2 may be defined by a tapered sidewall 909 of the inlet riser opening 812, where the width dimension of the inlet riser opening 812 may gradually decrease along the direction of the reactant flow 160-2 toward an outlet 907 at the second (e.g., lower) surface 902 of the ASP 15. 8B is a partial cutaway view of ASP 15 with a portion surrounding outlet 906 of ASP 15 removed to show the shape of the sidewall 908 of the inlet riser opening 812 that forms the first nozzle structure 903-1. In the embodiment shown in FIGS. 8A-8C, nozzle structures 903-1 and 903-2 have a frustum shape with a width dimension (i.e., diameter) that converges along the direction of reactant flows 160-1 and 160-2 through their respective nozzle structures 903-1 and 903-2. It will be appreciated that nozzle structures 903-1 and 903-2 in various embodiments may have different shapes, such as a frustum of a pyramid, a frustum of a sphere, an ovoid segment, or any other shape with a width dimension that converges along the direction of reactant flows 160-1 and 160-2. In various embodiments, the nozzle structures 903-1 and 903-2 can accelerate the flow of reactants 160 as they exit the ASP 15 through outlets 906 and 907, respectively. Thus, the reactants 160 accelerated by the nozzle structures 903-1 and 903-2 before entering the inlet riser channels 16a of the adjacent fuel cell stacks 14-1 and 14-2 can have sufficient kinetic energy to overcome increasing viscous drag along the reactant flow path through the fuel cell stacks 14-1 and 14-2.

[0034] 9 is a partial cross-sectional view of a portion of an ASP 15 without arrows indicating reactant flow to more clearly illustrate nozzle structures 903-1 and 903-2 at an inlet riser opening 812 of the ASP 15 according to one embodiment of the present disclosure. Referring to FIG. 9 , a first internal fluid conduit 815 may be located between a first (i.e., upper) interior wall 910 and a second (i.e., lower) interior wall 911 of the ASP 15. The distance between the upper interior wall 910 and the lower interior wall 911 may define a height dimension H of the first internal fluid conduit 815. The first nozzle structure 903-1 at the inlet riser opening 812 may have an inlet 912 defined by an opening in the upper interior wall 910 of the ASP 15. The second nozzle structure 903-2 at the inlet riser opening 812 may have an inlet 913 defined by an opening in the lower interior wall 911 of the ASP 15. The inlets 912 and 913 to the nozzle structures 903-1 and 903-2 may have a width dimension W1. In some embodiments, the width dimension W1 of the inlets 912 and 913 to the nozzle structures 903-1 and 903-2 may be greater than the height dimension H of the first internal fluid conduit 815. In some embodiments, the width dimension W1 of the inlets 912 and 913 to the nozzle structures 903-1 and 903-2 may be less than the width of the inlet riser channel 16a of the adjacent fuel cell stacks 14-1 and 14-2 (see FIG. 8C ).

[0035] Within nozzle structures 903-1 and 903-2, the width dimension of nozzle structures 903-1 and 903-2 may be defined by at least one sidewall 908 and 909. In the embodiment shown in Figure 9, the sidewalls 908 and 909 of nozzle structures 903-1 and 903-2 may be curved sidewalls that extend continuously around the entire periphery of nozzle structures 903-1 and 903-2. In other embodiments, multiple sidewalls may extend around the periphery of nozzle structures 903-1 and 903-2 such that nozzle structures 903-1 and 903-2 may have a polygonal cross-sectional shape. 9, at least one sidewall 908, 909 of each nozzle structure 903-1, 903-2 can be angled or curved along the direction of reactant flow such that the width dimension of the nozzle structures 903-1, 903-2 gradually decreases along the length of the nozzle structures 903-1, 903-2 between the respective inlets 912, 913 and the respective outlets 906, 907. In the embodiment shown in FIG. 9, the sidewalls 908, 909 of the nozzle structures 903-1, 903-2 have a converging angle θ with respect to the vertical. In various embodiments, the converging angle θ of at least one sidewall 908, 909 of the nozzle structures 903-1, 903-2 can be between about 10° and about 45°, such as between about 15° and about 35°, for example, about 26°.

[0036] The outlets 906 and 907 of the nozzle structures 903-1 and 903-2 can have a width dimension W2 that is less than the width dimension W1 of the inlets 912 and 913 of the nozzle structures 903-1 and 903-2. In various embodiments, the width dimension W2 of the outlets 906 and 907 of the nozzle structures 903-1 and 903-2 can be at least about 20% less, such as 30% to 50%, for example about 40% less, than the width dimension W1 of the inlets 912 and 913 of the nozzle structures 903-1 and 903-2. In some embodiments, the width dimension W2 of the outlets 906 and 907 of the nozzle structures 903-1 and 903-2 can be less than the height dimension H of the first internal fluid conduit 815. Each of the nozzle structures 903-1 and 903-2 may have a length dimension between the inlets 912 and 913 and the outlets 906 and 907 of the nozzle structures 903-1 and 903-2, respectively, defined by a thickness T of the ASP 15 between the outer surfaces 901 and 902 and the inner walls 910 and 911 of the ASP 15, respectively. In some embodiments, the thickness T may be less than a width dimension W2 of the outlets 906 and 907 of the nozzle structures 903-1 and 903-2.

[0037] In one non-limiting embodiment, the height dimension H of first internal fluid conduit 815 can be 3 mm to 8 mm, e.g., 5 mm to 6 mm, the width dimension W1 of inlets 912 and 913 of nozzle structures 903-1 and 903-2 can be 4 mm to 10 mm, e.g., 6 mm to 7 mm, the width dimension W2 of outlets 906 and 907 of nozzle structures 903-1 and 903-2 can be 2 mm to 6 mm, e.g., 4 mm to 5 mm, and the length dimension (defined by thickness T) of each of nozzle structures 903-1 and 903-2 can be 1 mm to 4 mm, e.g., 2 mm to 3 mm. In the embodiment shown in FIG. 9, each of nozzle structures 903-1 and 903-2 has the same size and shape, although it will be understood that nozzle structures 903-1 and 903-2 may have different sizes and / or shapes. 8A-9 include a pair of nozzle structures 903-1 and 903-2 positioned within the inlet riser opening 812, it will be understood that various embodiments of the reactant supply and return assembly 15 may include three or more nozzle structures 903, or may include a single nozzle structure 903. For example, the ASP 15 described above may have an inlet riser opening 812 with nozzle structure 903-1 along one reactant flow path to one adjacent fuel cell stack 14-1, and may have a conventional (i.e., non-tapered) opening with straight, vertically extending sidewall(s) along a second reactant flow path to another adjacent fuel cell stack 14-2.

[0038] 8A-9, can help ensure that adequate fuel reaches all of the fuel cells in adjacent fuel cell stacks 14-1 and 14-2, including fuel cells near the "stack-to-stack" interface. A fuel cell stack assembly including one embodiment of a reactant supply and return assembly 15 can reduce differences in fuel utilization (FU) in different portions of the fuel cell stacks 14-1 and 14-2 compared to fuel cell stack assemblies with conventional reactant supply and return assemblies.

[0039] 10 shows a plot of fuel utilization as a function of column height for a pair of fuel cell stacks 14-1 and 14-2 separated within a column by an anode splitter plate 15. Line 1001 corresponds to the FU of the comparative ASP without nozzles, and line 1002 corresponds to an embodiment of an ASP 15 having a pair of nozzle structures 903-1 and 903-2 within the inlet riser opening 812. As shown in FIG. 10, the difference between the maximum and minimum fuel utilization values ​​for the fuel cell stack using the embodiment of the ASP (i.e., maximum FU - minimum FU) is less than half the difference between the maximum and minimum fuel utilization values ​​for the fuel cell stack using the comparative ASP.

[0040] Thus, use of an embodiment of a reactant supply / return assembly 15 (e.g., ASP) having at least one nozzle structure 903-1 and 903-2 described above can result in a more uniform FU as a function of column height and a maximum fuel utilization (FU) much closer to the intended FU set point. This can enable operation of a fuel cell stack and / or a hot box including a fuel cell stack at a higher FU set point without risking fuel starvation in any of the fuel cells in the stack(s). In some embodiments, the FU set point of the stack(s) can be increased by at least 1%, such as at least about 1.5% (e.g., about 1.6%), without affecting cell performance, thereby improving system efficiency. Furthermore, the gain in maximum FU can be achieved without significant spikes in reactant pressure in the fuel cells closest to the ASP. A more uniform FU as a function of column height also leads to a more uniform output voltage profile as a function of column height.

[0041] The above method descriptions are provided as illustrative examples and are not intended to require or imply that the steps of the various embodiments must be performed in the order presented. As will be understood by one of ordinary skill in the art, the order of steps in the above embodiments can be performed in any order. Terms such as "thereafter," "then," and "next" are not intended to necessarily limit the order of the steps. These terms are merely used to guide the reader through the method descriptions. Furthermore, any reference to a claim element in the singular, for example, using the article "a," "an," or "the," should not be construed as limiting the element to the singular.

[0042] Furthermore, any step of any embodiment described herein can be used in any other embodiment. The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use any of the described embodiments. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments without departing from the scope of the present disclosure. Thus, the claims are not intended to be limited to the embodiments shown herein, but are to be accorded the widest scope consistent with the language of the claims and the principles and novel features disclosed herein.

Claims

1. A fuel cell stack system, comprising: a fuel cell stack including end plates having inlet and outlet riser channel openings extending therethrough; a reactant supply and return assembly having an outer surface adjacent the end plate of the fuel cell stack; the reactant supply and return assembly comprising: a reactant supply opening in the reactant supply and return assembly; a reactant exhaust opening in the reactant supply and return assembly; a reactant supply channel in said reactant supply and return assembly in fluid communication with a reactant supply opening; a nozzle structure disposed between the reactant supply channel and an opening in the outer surface of the reactant supply and return assembly, the nozzle structure having a width dimension that decreases along a direction of reactant flow through the at least one nozzle structure to the opening in the outer surface of the reactant supply and return assembly; a reactant exhaust channel in the reactant supply and return assembly in fluid communication with the reactant exhaust opening; Equipped with an opening in an exterior surface of the reactant supply and return assembly adjacent the inlet riser channel opening in the end plate of the fuel cell stack; a width of the opening in the outer surface of the reactant supply and return assembly is smaller than a width of the inlet riser channel opening; Fuel cell stack system.

2. the reactant supply and return assembly includes an anode splitter plate; the nozzle structure includes a first nozzle structure; the reactant supply and return assembly includes a second nozzle structure in fluid communication with the reactant supply channel; The fuel cell stack system according to claim 1 .

3. 3. The fuel cell stack system of claim 2, wherein the reactant supply channel is located between a first inner wall and a second inner wall of the reactant supply and return assembly, an opening in the first inner wall defining an inlet to the first nozzle structure, and an opening in the second inner wall defining an inlet to the second nozzle structure.

4. a width dimension of the opening in the first inner wall of the reactant supply / return assembly is greater than a width dimension of the opening in the first outer surface of the reactant supply / return assembly; 4. The fuel cell stack system of claim 3, wherein a width dimension of the opening in the second inner wall of the reactant supply / return assembly is greater than a width dimension of the opening in the second outer surface of the reactant supply / return assembly.

5. 5. The fuel cell stack system of claim 4, wherein the width dimensions of the openings in the first outer surface and the second outer surface of the reactant supply / return assembly are 30% to 50% smaller than the width dimensions of the openings in the first inner wall and the second inner wall of the reactant supply / return assembly.

6. 5. The fuel cell stack system of claim 4, wherein a height dimension between the first inner wall and the second inner wall of the reactant supply / return assembly is greater than a width dimension of the openings in the first outer surface and the second outer surface of the reactant supply / return assembly.

7. 5. The fuel cell stack system of claim 4, wherein a height dimension between the first inner wall and the second inner wall of the reactant supply / return assembly is smaller than a width dimension of the opening in the first inner wall and the second inner wall of the reactant supply / return assembly.

8. The reactant supply return assembly outer surface comprises a reactant supply return assembly first outer surface; the first nozzle structure includes at least one sidewall that is angled or curved to gradually decrease a width dimension of the first nozzle structure between the opening in the first inner wall and the opening in the first outer surface of the reactant supply and return assembly; 5. The fuel cell stack system of claim 4, wherein the second nozzle structure includes at least one sidewall that is angled or curved to gradually decrease a width dimension of the second nozzle structure between the opening in the second inner wall and an opening in a second outer surface of the reactant supply / return assembly opposite the first outer surface of the reactant supply / return assembly.

9. 9. The fuel cell stack system of claim 8, wherein the at least one sidewall of the first nozzle structure and the at least one sidewall of the second nozzle structure have a convergent angle with respect to vertical of between 15° and 35°.

10. The fuel cell stack includes a first fuel cell stack having a first end plate having a first inlet riser channel opening and a first outlet riser channel opening extending through the first end plate; the outer surface of the reactant supply / return assembly adjacent the first end plate of the first fuel cell stack comprises a first outer surface of the reactant supply / return assembly; the fuel cell stack system further includes a second fuel cell stack having a second end plate with inlet riser channel openings and outlet riser channel openings extending therethrough; a second outer surface of the reactant supply / return assembly disposed adjacent the second end plate of the second fuel cell stack; The fuel cell stack system according to claim 1 .

11. the nozzle structure includes a first nozzle structure in fluid communication with the reactant supply channel and the first inlet riser channel of the first fuel cell stack; the reactant supply and return assembly includes a second nozzle structure in fluid communication with the reactant supply channel and a second inlet riser channel of the second fuel cell stack; the first nozzle structure has a width dimension that decreases along a direction of reactant flow through the at least one nozzle structure to the first inlet riser channel; 11. The fuel cell stack system of claim 10, wherein the second nozzle structure has a width dimension that decreases along a direction of reactant flow through the at least one nozzle structure to the second inlet riser channel.

12. a reactant supply conduit fluidly connected to the reactant supply opening; a reactant exhaust conduit fluidly connected to the reactant exhaust opening; The fuel cell stack system of claim 11 further comprising:

13. the reactant supply channel includes an internal fluid conduit extending between the reactant supply opening and an inlet riser opening; the inlet riser opening extends through the reactant supply and return assembly and is in fluid communication with the first inlet riser channel of the first fuel cell stack and the second inlet riser channel of the second fuel cell stack; 13. The fuel cell stack system of claim 12, wherein the first nozzle structure and the second nozzle structure are located within the inlet riser opening of the reactant supply and return assembly.

14. 12. The fuel cell stack system of claim 11, wherein the first nozzle structure is configured to accelerate the reactants flowing through the assembly before the reactants enter the first inlet riser channel of the first fuel cell stack.

15. 15. The fuel cell stack system of claim 14, wherein the reactants include a fuel, and the first fuel cell stack and the second fuel cell stack include solid oxide fuel cell stacks.

16. a column including at least a first fuel cell stack and a second fuel cell stack; a reactant supply and return assembly located between the first fuel cell stack and the second fuel cell stack within the column; Equipped with the reactant supply and return assembly is in fluid communication with the first fuel cell stack and the second fuel cell stack and is configured to provide a reactant supply to, and receive a reactant exhaust from, each of, the first fuel cell stack and the second fuel cell stack; the reactant supply and return assembly comprising a nozzle structure along a flow path of the reactant supply; the nozzle structure has a width dimension that decreases along the direction of the flow path of the reactant feed through the nozzle structure to the inlet of the first fuel cell stack of the column; the nozzle structure is external to the first fuel cell stack and the second fuel cell stack; a central axis of the nozzle structure vertically aligned with an inlet of the first fuel cell stack of the column; a width dimension of the nozzle structure at the outlet that is smaller than a width dimension of the inlet of the first fuel cell stack in the column; Fuel cell stack system.

17. the nozzle structure includes a first nozzle structure along a flow path of the reactant feed to the first fuel cell stack of the column; the reactant supply and return assembly further comprising a second nozzle structure along a flow path of the reactant supply to the second fuel cell stack of the column.

17. The fuel cell stack system of claim 16.

18. 20. The fuel cell stack system of claim 17, wherein the reactant supply and return assembly includes an anode splitter plate, and the first fuel cell stack and the second fuel cell stack include solid oxide fuel cell stacks.

19. 20. The fuel cell stack system of claim 17, wherein the reactant supply and return assembly further comprises a reactant supply channel located between a first interior wall and a second interior wall of the assembly, an opening in the first interior wall defining an inlet to the first nozzle structure and an opening in the second interior wall defining an inlet to the second nozzle structure.

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