KR100842987B1 - Mixer/educator for high temperature fuel cells - Google Patents

Abstract

The fuel cell system includes a fuel cell stack having an anode side and a cathode side, and a mixer / educator for mixing anode exhaust gas and oxidant feed gas from the anode side outlet; The anode side has an inlet for receiving fuel and an outlet for exhausting anode exhaust gas containing fuel gas; The cathode side has an inlet for receiving oxidant gas and an outlet for releasing oxidant exhaust gas. The mixer / educator produces a branching jet or stream of oxidant feed gas to enhance mixing and promote pressure loss reduction. In particular, the mixer / educator includes elements disposed at an angle to the path of the oxidant feed gas that is unique to serve to establish a complex oxidant gas stream.

Anode, cathode, exhaust, nozzle, mixing duct, baffle, air spinner, blade

Description

Mixer / Educator for High Temperature Fuel Cells {MIXER / EDUCATOR FOR HIGH TEMPERATURE FUEL CELLS}

The present invention relates to the control of pressure deviations between the anode or fuel and the oxidation side of the cathode or fuel cell stack, in particular the anode outlet or exhaust gas for supplying the stack cathode side with the inlet air or oxidant gas. This is to minimize the pressure deviation when mixing. In particular, the present invention relates to anode tail gas and deviation pressure that compensates for a fuel cell system.

A fuel cell is a device that directly converts chemical energy stored in a hydrogen-containing fuel such as hydrogen, methane, or natural gas into electrical energy by an electrochemical reaction. This is different from traditional power generation methods, where the fuel must first be burned to produce heat and then converted to mechanical energy and finally to electricity. The more direct conversion process used by fuel cells has significant advantages over traditional means in terms of increased efficiency and reduced pollutant emissions.

In general, a fuel cell similar to a battery includes a negative electrode or an anode electrode and a positive electrode or a cathode electrode separated by an electrolyte, and the electrolytic material is used to conduct electrically charged ions between the negative electrode and the positive electrodes. Used. However, unlike batteries, fuel cells will continue to produce power as long as fuel and oxidant are supplied to the anode and cathode. To achieve this, a gas flow field is provided near the anode and cathode, through which fuel and oxidant gas are supplied. In order to generate useful power levels, a number of different fuel cells must be stacked in series with the conductive separator between each cell and its neighbors.

In a high temperature fuel cell stack, fresh air provided on the oxidant or cathode side of the stack needs to be heated from ambient temperature to the temperature of the fuel cell stack. One way to achieve this is to burn unused fuel from the anode side exhaust in the incoming air. This "combustion" is carried out in gas-phase combustors or catalytic reactors, which are generally used for high temperature fuel cells. In order to ensure a perfect reaction of the fuel and also to minimize the temperature gradient in the catalyst, the anode side exhaust gas must be perfectly mixed with air.

In the process flow, this mixing process combines the anode side gas pressure with the cathode side gas pressure at the junction of the two streams. The pressure at the anode side outlet is higher than the pressure at the cathode side inlet by the amount necessary to overcome the pressure loss associated with the oxidant and connecting piping used to combust the gas. Pressure deviations cause a tendency for the anode gas to leak into the cathode inlet space; The higher the pressure deviation, the better the seal should be. The seal between anode and cathode in a fuel cell stack is typically formed by mechanical forces between two surfaces, and in some cases the manifold seal includes a porous gasket material designed to allow for an "acceptable" leak rate. Sometimes. The leak rate in these two embodiments is a function of the anode-cathode pressure deviation. Therefore, it is very important to minimize the pressure deviation in order to prevent excessive leakage. Ultimately, leakage acts to reduce system efficiency, and also increases contamination emissions and shortens stack life.

Minimization of the pressure deviation in conventional systems has been achieved by equilibrating the pressure of oxidant gas at the cathode side inlet of the stack relative to the pressure of the exhaust fuel gas at the anode side outlet of the stack. This must be realized in spite of other operating requirements which tend to make the pressures not equal.

Existing fuel cell systems have a variety of approaches to solve the problems of mixing and deviation pressures. Mixing is accomplished by flowing the two streams along a long pipe length before distributing the catalyst. However, the length of pipe required for proper mixing is too long for use in conventional systems, causing excessive pressure deviations. Long pipes may generate unwanted heat losses from the gas stream. Other mixing systems use commercially available "static" mixing plates, which produce a high degree of fluid shear in the mixture, providing a very uniform composition. Unfortunately, such static mixers generate significant pressure losses, which increase the unbalance of anode-cathode pressure in the fuel cell stack.

To solve the pressure balance problem, the system overcomes the pressure loss of the connecting piping and the mixer and oxidant by using a high temperature booster blower placed between the anode side outlet and the mixing point of the stack. This has the advantage of being able to control the pressure balance independently, but there is a significant cost and reliability problem for commercial systems. Another system uses a downstream hot regeneration blower to draw the anode exhaust and fresh air oxidant gas through the mixer and oxidant. This system allows, by some control over the deviation, the gas pressure at the cathode side inlet to be higher than the gas pressure at the anode side outlet. Disadvantages to such a system include the overall complexity of the system hardware as well as the cost and reliability of the regenerative blower. Another approach to solving the pressure deviation is simply to make the fuel pressure higher than the oxidant pressure. Experience in this case presents several problems in operation, such as uneven stack temperatures, reduced system efficiency, and increased emissions of exhaust pollutants.

US patent application Ser. No. 10 / 187.495, assigned to the assignee of the present invention, discloses a mixer / educator; This mixer / educator provides good mixing of fresh oxidant or air with ananoe exhaust gas and provides a reduced pressure deviation between the gas at the cathode side inlet of the fuel cell stack and the gas at the anode side outlet of the stack. . The mixer / educator uses energy from the incoming fresh air stream (provided by a fresh air blower) to reduce the pressure of the anode stream at the point of mixing. In particular, the mixer / educator is designed to increase the speed and to reduce the pressure of the oxidant feed gas to which the anode outlet stream is connected and mixed with the oxidant gas stream. The high speed mixture then passes through a diffuser portion that slows the mixture down and raises the pressure of the mixture. The pressure rise of the mixed gas is controlled such that the gas pressure at the anode side outlet is the same as the gas pressure at the stack cathode side inlet.

It is an object of the present invention that the pressure loss of oxidant gas through the eductor can be further reduced; The mixing level of the fresh air of the oxidant gas and the anode exhaust is optimized; In a manner to avoid the disadvantages described above, there is provided an improved mixer / educator in which the pressure between the gas at the anode side outlet of the stack and the gas at the cathode side inlet can be balanced over the entire operating range of the system. It is.

According to the principles of the present invention, the above and other objects can be realized in a fuel cell system having a mixer / educator of the type described above adapted to produce a composite jet of oxidant feed gas; Desired mixing between the oxidant feed gas and the anode exhaust in the mixer / educator can be realized, and the equilibrium between the anode exhaust at the anode side outlet of the system's fuel cell and the oxidant gas at the cathode side inlet is further achieved. It is well realized. In particular, in accordance with the present invention, the mixer / educator includes elements arranged at an angle to the path of the oxidant feed gas to interact with the anode outlet gas to produce a branched jet set of cathode gas that is effectively mixed. This type of mixer / educator allows the desired mixing and pressure balance to be realized for a known operating range in the system design of the setup. In addition, the flow of oxidant exhaust gas or oxidant gas from the exhaust regeneration blower may be controlled to help balance the pressure.

Other objects, features and advantages of the present invention will be more clearly understood by the following detailed description with reference to the accompanying drawings.

1 is a block diagram illustrating a fuel cell system including a mixer / educator in accordance with the principles of the present invention;

FIG. 2A is a sectional view of a first embodiment of the mixer / educator of FIG.

FIG. 2B is a perspective view of a portion of the mixer / educator of FIG. 2A. FIG.

FIG. 2C is a cross-sectional view of a portion of the mixer / educator shown in FIG. 2B to illustrate a gas flow path. FIG.

3A is a sectional view of a second embodiment of the mixer / educator of FIG.

FIG. 3B is a perspective view of a portion of the mixer / educator of FIG. 3A. FIG.

FIG. 3C is a cross sectional view of a portion of the mixer / educator shown in FIG. 3B to illustrate a gas flow path; FIG.

4A is a cross-sectional view of a third embodiment of the mixer / educator of FIG.

4B is a perspective view of a portion of the mixer / educator of FIG. 4A.

4C is a cross-sectional view of a portion of the mixer / educator shown in FIG. 4B to illustrate a gas flow path.

FIG. 5A is a sectional view of a fourth embodiment of the mixer / educator of FIG.

FIG. 5B is a perspective view of a portion of the mixer / educator of FIG. 5A. FIG.

FIG. 5C is a cross-sectional view of a portion of the mixer / educator shown in FIG. 5B to illustrate a gas flow path. FIG.

FIG. 6A is a cross-sectional view of the mixer / educator of US Patent Application No. 10 / 187.495. FIG.

FIG. 6B is a cross-sectional view of a portion of the mixer / educator shown in FIG. 6A to illustrate a gas flow path. FIG.

FIG. 7 is a graph comparing measured air side pressure loss improvement of the mixer / educator of US patent application Ser. No. 10 / 187.495 and the mixer / educator of the present invention. FIG.

8 is a graph comparing measured anode side suction improvement of the mixer / educator of US patent application Ser. No. 10 / 187.495 and the mixer / educator of the present invention.

9 shows measured mixing uniformity achieved using the mixer / educator of the present invention.

FIG. 10 shows measured mixing uniformity achieved using the mixer / educator of US patent application 10 / 187.495.

1 schematically shows a fuel cell system 1. The system 1 comprises a fuel cell 2 comprising anode and cathode portions 2A and 2B, respectively, an oxidant 3 and a blower 4. The fuel cell system 1 also comprises a mixer / educator 5 according to the principles of the invention.

As shown, the exhaust oxidant gas and fresh air 6 recovered by the regeneration blower 4 from the cathode side portion 2B are combined to produce an oxidant feed gas 6A. The oxidant feed gas 6A is supplied to the mixer / educater 5 at the inlet 5A. When passing through the mixer / educator 5, the oxidant feed gas 6A depressurizes the pressure and contains the anode exhaust gas entering the mixer / educator 5 at the inlet 5B. The mixture of oxidant feed gas and anode exhaust gas exits the mixer / educator 5 at outlet 5C and continues to inlet 3A of oxidant 3. In the oxidant 3, the fuel remaining in the anode exhaust of the mixed gas is burned, raising the temperature of the gas stream. The outlet stream from the oxidant is distributed to the cathode inlet 8 of the cathode portion 2B.

The oxidant exhaust gas is output from the cathode outlet 9, and as described above, part of it is regenerated by the regeneration blower 4 into the inlet air. Fuel gas is distributed to the anode portion 2A at the inlet 11.

In general, one purpose of the mixer / educator 5 in the system 1 is to provide an anode exhaust at the outlet 7 of the anode portion 2A and an oxidant gas at the inlet 8 of the cathode portion 2B. It is to reduce or minimize the pressure deviation. Another purpose of the mixer / educator 5 is to provide an anode exhaust gas contained in the inlet 5B of the mixer / eductor for supply to the oxidant 3 and an oxidant feed gas 6A contained in the inlet 5A of the mixer / eductor. It is to achieve a good mixing of.

According to the invention, the mixer / educator 5 increases the speed and reduces the pressure of the oxidant feed gas at the position where the anode exhaust stream meets the oxidant feed gas stream. This is to reduce the pressure of the anode exhaust at the inlet 5B of the mixer / educator. The anode exhaust mixes with the oxidant feed gas received at the inlet 5A of the mixer / educate. The pressure of the mixed gas increases as it passes through the mixer / educator 5 and through the oxidant 3.

According to the invention, the mixer / educator 5 comprises several elements arranged at an angle with respect to the axis or path of the oxidant feed gas 6A, in which the branching of the oxidant feed gas for the oxidant feed gas. The jet is set. In this way, the increase in pressure of the mixed gas and the mixing of the gas can be well controlled, thus optimizing the mixing and oxidizing the oxidant gas and the anode portion 2A at the inlet 8 of the cathode portion 2B. The pressure deviation of the anode exhaust at the outlet 7 is minimized. Various embodiments of the mixer / educator of the present invention will be described below.

First Embodiment (FIGS. 2A-2C): Five Nozzles

2A-2C show a first embodiment of the mixer / educator 100 of the present invention. In FIG. 2B, mixer / educator 100 includes an oxidant feed gas inlet 120 for an oxidant feed gas and an anode exhaust gas inlet 121 for an anode exhaust gas; These inlets form the T-shaped mixing assembly 122. In another embodiment, shown in dashed lines, the mixing assembly 122 may be modified to form a crossover assembly by providing a second inlet 121A for anode exhaust. Another anode exhaust gas inlet may be added without changing the spirit or function of the present invention. It should be appreciated that the cross-sectional areas 101 and 102 of the inlets 120 and 121 shown in FIG. 2A are selected based on the overall flow rate required at the inlet.

The nozzle arrangement 126 connected to the inlet 120 comprises a device at a divergent angle with respect to the path of the incoming oxidant feed gas, so branched oxidant gas jets which help to enhance mixing of the two streams and minimize pressure losses. Can be generated. In particular, as shown in Figs. 2A to 2C, five nozzle tubes 126A to 126E are arranged in the nozzle apparatus; Four nozzle tubes 126B to 126E of the five nozzle tubes are disposed at an angle with respect to the path of the incoming oxidant 129, and the other nozzle tube 126A is disposed along this path. In the illustrated embodiment, the nozzle tubes 126A are arranged horizontally, and opposing first pairs of tubes 126B and 126C form an angle (third and fourth angles) above and below the tube 126A. Opposite second tube pairs 126D, 126E (not shown) are at an angle (the fifth and sixth angles) with respect to the right and left sides of tube 126A. Each nozzle tube 126A-126E includes a smooth filleted lead-in 139 (shown in FIG. 2B).

The nozzle tubes 126A-126E accelerate the oxidant feed gas at high speed, as shown in FIG. 2C, by the velocity vectors 140, 141, 142 of the tubes 126A- 126C. The number and diameter 106 (shown in FIG. 2A) of the nozzle tubes 126A-126E are selected to provide the required speed required for the desired pressure level. In this regard, each nozzle tube 126A-126E may have a different diameter depending on the particular application. In addition, the direction of the nozzle tubes 126A to 126E may differ from that shown. In general, the tubes are aligned on one or more axes of symmetry, but may be intentionally asymmetrical to meet the specific performance requirements of a given application. In addition, the length 107 of the nozzle tube is selected to ensure that the flow is directed at the desired angle 108 while preventing excessive frictional pressure loss in the tube itself.

As the oxidant feed gas leaves the nozzle tubes 126A-126E, mixing with the anode exhaust begins in the mixing assembly 122. To this end, the shape of the nozzle arrangement 126, such as the angle 108 or the like, where four nozzle tubes 126B to 126E are directed with respect to the incoming oxidant path 129, is a vector of anode exhaust gas (see FIG. 2C). And 150 to maximize mixing of the oxidant gas and the anode exhaust in the mixing assembly 122 and delaying the incorporation of each jet into a single large jet. In addition, the rotational position 128 (FIG. 2B) of the nozzle tubes 126B-126E is selected so that the mixing of the two gas streams is maximized. The position 109 of the ends of the nozzle tubes 126A to 126E relative to the centerline of the inlet 121 (FIG. 2A) is also selected to achieve the desired pressure distribution.

The high velocity of oxidant gas includes the anode exhaust inside the mixing assembly 122, which mixture is moved to the mixing duct 123. The mixing duct 123 has a mouth opening 103, a length 104 and a fire or branch angle 105; All these devices are chosen to promote the desired mixing. Thus, mixing between the two gas streams (ie, the first and second streams) in the mixing duct is continued, and this mixing is aided by the baffle plate 124 which acts to create turbulence and recycling in the mixture. As shown in Figure 2A, the length 110, angle 111 and position 112 of the baffle plate 124 is selected to maximize mixing while preventing excessive pressure loss. The gas mixture continues to flow down the mixing duct, enters the catalyst manifold 198, rotates in this catalyst manifold (shown by arrow 159) and passes through the catalyst bed 199.

Parameters useful for realizing the various components of the mixer / educator of FIGS. 2A-2C include nozzle tube divergence angle 108 of 0 ° to 45 °; Nozzle tube position 109 between -1 and +1 times the anode gas pipe diameter 102; Nozzle tube rotation clocking 128 between -90 ° and + 90 °; Nozzle tube length 107 between one and ten times the nozzle tube diameter 106; A mixing duct fire angle 105 between 0 ° and 30 °; Catalyst surface directivity angle 159 between 0 ° and 90 °; Use of nozzle tube 126; The use of baffle plate 124.

Second Embodiment (FIGS. 3A-3C): Four Nozzles

3A-3C show a second embodiment of the mixer / educator 200 of the present invention. In FIG. 3B, the mixer / educator includes an oxidant feed gas inlet 220 for an oxidant feed gas and an anode exhaust gas inlet 221 for an anode exhaust gas; These inlets form the T-shaped mixing assembly 222. In another embodiment, as described above for the first embodiment of the mixer / educator, the mixing assembly 222 may be formed as a crossover assembly by providing an additional inlet for anode exhaust, or various angles. It may be formed by adding another inlet at the location. The cross-sectional areas 201 and 202 of the inlets 220 and 221 shown in FIG. 3A are selected based on the overall flow rates foreseen for the particular application.

The nozzle device 226 connected to the inlet 220 includes a device at a branch angle to the path of the incoming oxidant feed gas, thereby generating a branch jet that enhances mixing of the two streams and minimizes pressure loss. In particular, four nozzle tubes 226A to 226D are arranged in the nozzle apparatus; It is disposed at an angle to the path 229 of the incoming oxidant. 3A-3C only vertically opposed nozzle tubes 226A- 226B are shown connected to the right side of the partition wall terminating at the inlet 220. On the left side of the partition wall is connected a pair of similarly opposed nozzle tubes 226C to 226D. Each nozzle tube 226A-226D includes a smooth filleted lead-in 239 (shown in Figure 3B).

The nozzle tubes 226A through 226D accelerate the oxidant feed gas at high speed as shown in FIG. 3C by the velocity vectors 240 and 241 of the tubes 226A through 226B. The diameter 206 (shown in FIG. 3A) of the nozzle tubes 226A-226D is selected to provide the required speed required for the desired volume level. Each nozzle 226 may have a different diameter depending on the particular application. In addition, the nozzle tubes 226A-226D are generally aligned on one or more axes of symmetry, but may be asymmetrically aligned to meet the mixing requirements and specific volume of use. In addition, the length 207 of the nozzle tube (first nozzle tube to fourth nozzle tube) 226A to 226D is such that the desired flow angles (first angle and second angle) while preventing excessive frictional pressure loss in the tube itself. Is selected to ensure that it is directed to (208).

As the oxidant feed gas leaves the nozzle tubes 226A-226D, mixing with the anode exhaust begins in the mixing assembly 222. The shape of the nozzle apparatus 226, such as the angles 208 and the like, to which the nozzle tubes 226A to 226D are directed, includes the inclusion of anode exhaust (shown as vectors 250 and 251 in FIG. 3C) and the mixing assembly 222. ) Maximizes the mixing of oxidant gas and anode exhaust gas and delays the incorporation of each gas flow path into a single large path. In addition, the rotational position 228 (FIG. 3B) of the nozzle tubes 226A-226D is selected so that the mixing of the two gas streams is maximized. The position 209 of the end of the nozzle tube with respect to the centerline of the inlet 221 (FIG. 3A) is also selected to achieve the desired pressure distribution.

The high velocity of oxidant gas includes the anode exhaust inside the mixing assembly 222, which mixture is moved to the mixing duct 223. The mixing duct 223 has a mouth opening 203, a length 204, and a fire or branch angle 205; All these devices are chosen to promote the desired mixing. Thus, mixing between the two streams in the mixing duct is continued and this mixing is aided by a baffle plate (not shown) which acts to create turbulence and recycle in the mixture. The gas mixture continues to flow down the mixing duct, enters the catalyst manifold 298, rotates in this catalyst manifold (shown by arrow 259) and passes through the catalyst bed 299.

Parameters useful for realizing the various components of the mixer / educator of FIGS. 3A-3C include nozzle tube branch angles 208 of 0 ° to 90 °; Nozzle tube position 209 between -1 and +1 times the anode gas pipe diameter 202; Nozzle tube rotation clocking 228 between -45 ° and + 45 °; Nozzle tube length 207 between 1 and 10 times nozzle tube diameter 206; A mixing duct impingement angle 205 between 0 ° and 30 °; Catalyst surface directivity angle 259 between 0 ° and 90 °; Use of nozzle tube 226; The use of baffle plate 124.

Third Embodiment (Figs. 4A to 4C): One nozzle, first air spinner, mixed cone and second mixed spinner

4A-4C show a third embodiment of the mixer / educator 300 of the present invention. In FIG. 4C, mixer / educator 300 includes an oxidant feed gas inlet 320 for oxidant feed gas and an anode exhaust gas inlet 321 for anode exhaust gas; These inlets form the T-shaped mixing assembly 322. In other embodiments (not shown in Figures 4A-4C), the mixing assembly 322 may be formed as a crossover assembly by providing additional inlets for anode exhaust, or at various angular positions and It may be formed by adding another inlet. The cross-sectional areas 301, 302 of the inlets 320, 321 shown in FIG. 4A are selected based on the overall flow rates anticipated for the particular application.

The nozzle device 326 connected to the inlet 320 includes a device at a branch angle to the path of the incoming oxidant feed gas, thereby creating a branch flow that enhances mixing of the two streams and minimizes pressure loss. In particular, as shown in FIG. 4B, the mixing device includes a nozzle 326A disposed along a path 329 of the incoming oxidant feed gas and a first air spinner 330 at the inlet to the nozzle. The first air spinner 330 has a curved blade 330A forming an attack angle 338 and induces a vortex in a clockwise or counterclockwise direction with respect to the incoming oxidant gas.

When the oxidant gas flows through the nozzle 326A, it contracts and leaves through an opening having a diameter 306 (shown in FIG. 4A), which diameter 306 is larger than the diameter of the opening into which the oxidant gas enters the nozzle. small. The contraction of the gas flow by the nozzle accelerates the inlet oxidant gas at high speed as shown in FIG. 4C by the velocity vectors 340 and 341. The diameter 306 of the nozzle opening is selected to provide the required speed required for the desired pressure. In addition, the length 307 of the nozzle is selected to prevent excessive frictional pressure loss.

When the increased oxidant gas stream leaves the nozzle 326A, mixing with the anode exhaust begins in the mixing assembly 322 shown in FIG. 4C. The mixing device 326 includes a mixing cone 327; This mixing cone includes a surface 327A that is inclined to the path of the oxidant gas 329 to split the oxidant gas into several unique streams to improve gas mixing. A second mixed spinner 331 having curved blades 331A forming an attack angle 339 is provided inside the sleeve 332 which is subsequent to the mixing cone 327. The spinner 332 intensifies the mixing by inducing a clockwise or counterclockwise vortex in the gas mixture in a separate path from the mixing cone 327.

The shape of the mixing device 326, such as dimensions 310 and 322 of the mixing cone 327, includes the anode exhaust (shown as vectors 350 and 351 in FIG. 4C) and the oxidant gas in the mixing assembly 322. And mixing of the anode exhaust gas is maximized, and each flow stream is prevented from coalescing into a single large stream. Thus, for example, the distance 319 between the end of the nozzle 326A and the base of the mixing cone 327 is selected such that the mixing of the two gas streams is maximized. The position 309 of the end of the nozzle tube 326 relative to the centerline of the inlet 321 (FIG. 4A) is also selected to achieve the desired pressure distribution.

The high velocity of oxidant gas comprises anode exhaust inside the mixing assembly 322; After passing through the mixing cone 327 and the second mixing spinner 331, the gas mixture is moved to the mixing duct 323. The mixing duct (323) has a mouth opening (303), a length (304), and an indentation (305); All these devices are chosen to promote the desired mixing. This embodiment includes a baffle plate, such as the baffle plate 124 shown in FIG. 2A. The gas mixture continues to flow through the mixing duct 323, enters the catalyst manifold 398, rotates in this catalyst manifold (shown by arrow 359) and passes through the catalyst bed 399.

Parameters useful for realizing the various components of the mixer / educator of FIGS. 4A-4C include: attack angle 338 of the first air spinner 330 between −60 ° and + 60 °; The attack angle of the second blended spinner 331 between -60 ° and + 60 °; Nozzle position 309 between -1 and +1 times the anode gas pipe diameter 302; A mixing cone position 319 between one and ten times the nozzle tube diameter 306; A mixing duct deflection angle 305 between 0 ° and 30 °; Catalyst surface directivity angle 359 between 0 ° and 90 °; The use of baffle plate 124.

4th Embodiment (FIGS. 5A-5C): One nozzle, annular gap, mixed cone

5A-5C illustrate a third embodiment of the mixer / educator of the present invention. In FIG. 5B, mixer / educator 400 includes an oxidant feed gas inlet 420 for oxidant feed gas and an anode exhaust gas inlet 421 for anode exhaust. The cross-sectional areas 401, 402 of the inlets 420, 421 shown in FIG. 5A are selected based on the overall flow rates anticipated for the particular application.

The nozzle device 46 connected to the inlet 40 comprises an element angled with respect to the path of the incoming oxidant feed gas, which enhances the mixing of the oxidant gas flow with the anode exhaust stream and the oxidant feed gas. Split into two unique streams to minimize pressure loss. In particular, as shown in FIGS. 5A-5C, the mixing device 426 includes a nozzle 426A disposed along the path 429 of the incoming oxidant feed gas and protruding into the mixing elbow 431. The nozzle 426A has a bell mouse having a diameter 412, a nozzle tube diameter 406, an opening having a diameter 413 smaller than the bell mouse diameter 412 and opposite the bell mouse, and a nozzle tube diameter. 406. The incoming oxidant feed gas enters the nozzle 426A through the bell mouse, flows through the nozzle tube, and contracts as it leaves the nozzle into the elbow 431 through the opening as shown in FIG. 5C. The contraction of the air flow by the nozzle 426A accelerates the oxidant feed gas at high speed as shown in FIG. 5C by the velocity vectors 440 and 442 (first portion of the oxidant feed gas).

Oxidant gas that does not enter the bell mouse of the nozzle 426A flows around the nozzle and is contracted by an annular gap 424 formed at the inlet to the mixing duct 423. This contraction of the oxidant gas by the annular gap 424 accelerates the oxidant gas passing through the gap at high speed by the velocity vectors 441 and 443 (second portion of the oxidant feed gas). The combined flow zone of the nozzle 426A (measured by the diameter 413 of the nozzle opening) and the annulus 424 is selected to accelerate the oxidant gas at the rate required for the desired pressure. In addition, the length 407 of the nozzle 426A is selected to prevent excessive frictional pressure loss at the nozzle.

As shown in FIG. 5B, the anode exhaust gas inlet 421 directs the anode exhaust gas into the constriction passage 430, which constricts the anode exhaust gas as it flows into the mixing elbow 431. FIG. Accelerated exhaust gases are included by the increased oxidant gas stream leaving the nozzle 426A. When the increased oxidant gas stream leaves the nozzle 426A, it strikes the mixing cone 427 disposed in the mixing elbow 431. Since the mixed cone 427 includes a surface 427A angled with respect to the path 429 of the oxidant gas, the oxidant gas branches into several unique flow streams. The interaction of these various gas streams improves the mixing of oxidant exhaust and anode exhaust when anode exhaust is included, as shown in FIG. 5C.

The shape of the mixing device 426, such as the dimensions 410 and 411 of the mixing cone 427, includes the anode exhaust (shown as vectors 450 and 451 in Figure 5C) and the oxidant in the mixing elbow 431. The mixing of gas and anode exhaust gas is maximized, and each gas stream is prevented from coalescing into a single stream. Thus, for example, the distance 419 between the end of the nozzle 426A and the base of the mixing cone 427 is selected to maximize the mixing of the two gas streams. The position 409 of the end of the nozzle tube 426A with respect to the centerline of the inlet 421 (FIG. 5A) is also selected to achieve the desired pressure distribution.

The high velocity of the oxidant gas comprises the anode exhaust inside the mixing elbow 431, which mixture moves over the mixing cone 427 into the mixing duct 423 and passes through the annulus 424. Is derived. The mixing duct (423) has a mouth opening (403), a length (404), and an indentation (405); All these devices are chosen to promote the desired mixing. This embodiment includes a baffle plate, such as the baffle plate 124 shown in FIG. 2A. The gas mixture continues to flow through the mixing duct 423, enters the catalyst manifold 498, rotates in this catalyst manifold (shown by arrow 459) and passes through the catalyst bed 499.

Parameters useful for realizing the various components of the mixer / educator of FIGS. 5A-5C include nozzle tube positions 409 between -1 and +1 times the anode gas pipe diameter 402; A nozzle tube length 407 between one and ten times the nozzle tube diameter 406; A mixing cone position 419 between one and ten times the nozzle tube diameter 406; A mixing duct deflection angle 405 between 0 ° and 30 °; Catalyst surface directivity angle 459 between 0 ° and 90 °; Possible use of one or more baffle plates 124.

US patent application Ser. No. 10 / 187.495: Figures 6A and 6B

6A and 6B show a mixer / educator 500 of the type disclosed in US patent application Ser. No. 10 / 187.495. In FIG. 6A, the mixer / educator includes an oxidant gas inlet 50 for oxidant gas and an anode exhaust gas inlet 521 for anode exhaust. The cross sectional areas 501, 502 of the inlets 520, 521 are selected based on the overall flow rates anticipated for the particular application.

When the oxidant feed gas flows through the inlet 520, it contracts or “pinches” through an annular gap 524 between the circular opening of the elbow portion 521A of the inlet 521 and the inlet to the mixing duct 523. . The mixing duct has a diameter 503, a length 504, and an indentation 505. Contraction or “pinching” of the air flow through the annular gap 524 accelerates the inlet oxidant gas at high velocity in the mixing duct 523, as shown by the velocity vectors 540, 541 in FIG. 6B. The region of the annular gap 524 is selected to provide the required speed required for the desired pressure. In addition, the length 504 and width of the mixing duct 523 should be selected to prevent excessive pressure loss in the duct.

The high velocity oxidant feed gas comprises anode exhaust gas through which the elbow portion 521A of the inlet 521 passes through the opening into the mixing duct 523. The flow of anode exhaust to the mixing duct 523 is represented by a vector 550 as shown in FIG. 6B. The gas mixture continues to flow through the mixing duct 523, enters the catalyst manifold 598, rotates in this catalyst manifold (shown by arrow 559), and passes through the catalyst bed 599.

FIG. 7 shows the cathode-side pressure loss from point 6 to point 8 of FIG. 1 for the four embodiments described above when compared to a system using a mixer / educator of US patent application 10 / 187.495. Is a graph. In particular, the relative pressure at the cathode side gas inlet using the mixer / educator of US patent application Ser. No. 10 / 187.495 and the mixer / educator of the present invention is compared at various levels of oxidant feed gas flow rate. The data points on the chart represent oxidant gas pressure losses at different flow rates corresponding to the examples described above and those of US patent application Ser. No. 10 / 187.495.

Between the data point associated with the oxidant feed gas pressure loss in the mixer / educator of US patent application 10 / 187.495 and the data point associated with the oxidant feed gas pressure loss for the first to third embodiments of the present invention. Distance 710 represents an oxidant gas pressure loss of about 40%. The distance 711 between the data point associated with the oxidant feed gas pressure loss in the mixer / educator of US patent application 10 / 187.495 and the data point associated with the oxidant gas pressure loss for the fourth embodiment of the present invention is An oxidant gas pressure loss of about 15% is shown.

FIG. 8 is a graph showing the inhalation of the mixer / educator of US patent application Ser. No. 10 / 187.495 and the anode exhaust of the mixer / educator for each of the four embodiments of the present invention. Inhalations useful for the anode exhaust of the mixer / educator are shown at various levels of oxidant feed gas flow rates for the mixer / educator of US patent application 10 / 187.495 and each of the four embodiments of the present invention.

Larger negative values along the y-axis of these graphs indicate more suction at a given flow rate, and the ability to overcome more flow restrictions in interconnect piping and oxidant. As can be appreciated from this graph, the data indicate that the anode exhaust intake is almost identical to the mixer / educator of US patent application Ser. No. 10 / 187.495 and the mixer / educator of the first and second embodiments of the present invention. . This is shown by arrow 810, indicating that the deviation between the vacuum achieved by these embodiments and the vacuum achieved by the mixer / educator of US patent application 10 / 187.495 can be ignored. When inhalation variations can be neglected, these embodiments of the present invention have the advantage of providing 40% oxidant feed gas pressure loss as compared to the mixer / educator of US patent application 10 / 187.495. Arrow 811 represents the vacuum achieved by the fourth embodiment of the present invention. As shown by arrow 810, for the vacuum achieved by the mixer / educator of US patent application Ser. No. 10 / 187.495, this indicates that the fourth embodiment of the present invention provides a 500% improvement in suction. have. At the same time, the fourth embodiment provides a 15% improvement in oxidant gas pressure loss as compared to US patent application Ser. No. 10 / 187.495.

9 and 10 show the mixing uniformity on the surface of a catalyst bed using the mixer / educator of US patent application 10 / 187.495 and the mixer / educator of the first embodiment of the present invention. The values shown in FIG. 9 are values obtained through measurements made in the laboratory by racing an anode exhaust stream with helium and also using a helium detector to determine the concentration at the oxidant surface. Deviated data is a percentage deviation from the mean blend value. As shown in Fig. 9, the deviation value for the mixing uniformity in the first embodiment is ± 2%.

The values shown in FIG. 10 are values obtained through measurements made in the field of the operating temperature distribution of the oxidant. The temperature distribution is transformed into the estimated anode-outlet mixture distribution by subtracting the measured oxidant inlet temperature from the measured oxidant outlet temperature to obtain a heat release distribution in the oxidant. The heat dissipation is proportional to the anode exhaust distribution through the oxidant. Departures in FIG. 10 are expressed as percentage deviations from the average blend value. As shown in Fig. 10, the variation in mixing uniformity is ± 7% to 12%. Thus, the mixer / educator of the present invention significantly improves the mixing of gas compared to the mixer / educator of US patent application Ser. No. 10 / 187.495.

The present invention has been described with reference to the preferred embodiments, and is not limited thereto, and one of ordinary skill in the art should recognize that various modifications and changes can be made to the present invention without departing from the appended claims. Thus, for example, four or five nozzles were used in the first and second embodiments of the present invention, although more or fewer tubes may be used. The number of tubes ranges from 2 to 16.

Claims (42)

A fuel cell stack having an anode side and a cathode side; A mixer / educator for mixing anode exhaust and oxidant feed gas from the anode side outlet, The anode side has an inlet for receiving fuel and an outlet for exhausting anode exhaust gas containing fuel gas; The cathode side has an inlet for receiving oxidant gas and an outlet for releasing oxidant exhaust gas; The mixer / educator mixes the anode exhaust gas and the oxidant feed gas while reducing a deviation between the anode exhaust gas pressure at the anode side outlet and the pressure of the oxidant gas at the cathode side inlet; The mixer / educator produces a plurality of oxidant gas streams consisting of a first stream and a second stream to facilitate mixing of the oxidant feed gas and the anode exhaust gas and to reduce pressure drift. system. The fuel cell system of claim 1, wherein the first and second streams of the plurality of oxidant gas streams are angled with respect to each other. The fuel cell system of claim 1, wherein the mixer / educator comprises an assembly having elements angled with respect to the path of the oxidant feed gas to establish one or more composite gas streams. 4. The mixer / educator of claim 3, wherein the mixer / educator receives an anode exhaust gas inlet for receiving and transporting it to the region of the mixer / educator and an oxidant feed gas and transferring it to the region of the mixer / educator. An oxidant feed gas inlet for and a mixing duct leading to the region of the mixer / educator for receiving gas passing through the region; And the assembly is disposed in the region. 5. The assembly of claim 4, wherein the assembly comprises one or more nozzles arranged in the region and aligned at an angle to the path of the oxidant feed gas; One or more oxidant gas streams are established for the oxidant feed gas and the oxidant feed gas in the one or more oxidant gas streams interacts with the anode exhaust in the region to allow the gas to pass through the mixing duct. A portion of the feed gas passes through the one or more nozzles. 6. The fuel cell system of claim 5, wherein the mixer / educator further comprises one or more baffles disposed in the mixing duct to promote mixing of the gases in the mixing duct. 6. The apparatus of claim 5, wherein the at least one nozzle comprises first and second nozzles facing each other and vertically spaced apart from each other and third and fourth nozzles facing and mutually spaced apart from each other; The first and second nozzles are disposed at a first angle with respect to each other; And the third and fourth nozzles are disposed at a second angle with respect to each other, and are spaced horizontally from the first and second nozzles. 8. The fuel cell system of claim 7, wherein the mixer / educator further comprises one or more baffles disposed in the mixing duct to promote mixing of the gases in the mixing duct. The fuel cell system as claimed in claim 7, wherein the first angle and the second angle are the same. 6. The mixer of claim 5, wherein the mixer / educator includes additional nozzles disposed along the path of the oxidant feed gas; And a portion of the oxidant feed gas passes through this nozzle to establish one oxidant gas stream for the oxidant feed gas. 11. The apparatus of claim 10, wherein the one or more nozzles comprise first and second nozzles facing each other and third and fourth nozzles facing each other; The first and second nozzles are disposed above and below the additional nozzle at a third and fourth angle with respect to the additional nozzle and spaced vertically; And the third and fourth nozzles are disposed at left and right sides of the additional nozzles at a fifth angle and a sixth angle with respect to the additional nozzles, and are spaced horizontally. 12. The fuel cell system of claim 11, wherein the mixer / educator further comprises one or more baffles disposed in the mixing duct to promote mixing of the gases in the mixing duct. The fuel cell system as claimed in claim 11, wherein the third to sixth angles are the same. 5. The assembly of claim 4, wherein the assembly comprises a mixing cone disposed in the region; The mixing cone has a surface disposed at an angle to the path of the oxidant feed gas; One or more oxidant gas streams are established for the oxidant feed gas such that the oxidant feed gas in the one or more oxidant gas streams interacts with the anode exhaust in the region such that the gas passes through the mixed duct. And a gas impinges on the surface. 15. The apparatus of claim 14, wherein the mixer / educator comprises a nozzle disposed in the path of an oxidant feed gas preceding the mixing cone; Before impinging on the surface of the mixing cone, the oxidant feed gas passes through the nozzle. 16. The mixer / educator of claim 15, further comprising a first air spinner and a second mixed spinner for circulating gas in a clockwise or counterclockwise direction, wherein the first air spinner supplies an oxidant supply preceding the nozzle. And a second mixed spinner disposed after the mixed cone in the path of the gas from the mixed cone. 16. The fuel cell system of claim 15, wherein the spinners each comprise a plurality of curved blades. 16. The fuel cell system of claim 15, wherein the mixer / educator further comprises one or more baffles disposed in the mixing duct to promote mixing of the gases in the mixing duct. 5. The assembly of claim 4, wherein the assembly comprises a mixing cone disposed in the region and a nozzle disposed in the path of an oxidant feed gas preceding the mixing cone; The mixing cone has a surface disposed at an angle to the path of the oxidant feed gas; Wherein the one or more oxidant gas streams are set up for the first portion of the oxidant feed gas such that the first portion of the oxidant feed gas is present in the one or more oxidant gas streams and passes through the mixing duct. A portion impinges on the surface; Before impinging on the surface of the mixing cone, a first portion of an oxidant feed gas passes through the nozzle; The second portion of the oxidant feed gas passes through the gap around the nozzle and the mixing cone and into the mixing duct, The inlet includes an elbow portion extending into an area into the mixing cone for transferring anode exhaust to the mixing cone from which the nozzle extends, And a first portion of an oxidant feed gas and a second portion of the oxidant feed gas and the anode exhaust in the one or more oxidant gas streams interact in a mixing duct. 20. The fuel cell system according to claim 19, wherein the gap is formed in an area outside the area where the elbow is coupled with the outer circumferential portion of the support for the mixing cone. 20. The fuel cell system of claim 19, wherein the mixer / educator further comprises one or more baffles disposed in the mixing duct to promote mixing of the gases in the mixing duct. A mixer / educator for use in a fuel cell system, The fuel cell system includes a fuel cell stack having an anode side and a cathode side, and a mixer / educator for mixing anode exhaust gas and oxidant feed gas from the anode side outlet; The anode side has an inlet for receiving fuel and an outlet for exhausting anode exhaust gas containing fuel gas; The cathode side has an inlet for receiving oxidant gas and an outlet for releasing oxidant exhaust gas; The mixer / educator mixes the anode exhaust gas and the oxidant feed gas while reducing the deviation between the anode exhaust gas pressure at the anode side outlet and the pressure of the oxidant gas at the cathode side inlet; The mixer / educator produces a plurality of oxidant gas streams consisting of a first stream and a second stream to facilitate mixing of the oxidant feed gas and the anode exhaust gas and to reduce pressure drift. 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