WO2023186700A1

WO2023186700A1 - Water separator and hydrogen dilution device

Info

Publication number: WO2023186700A1
Application number: PCT/EP2023/057505
Authority: WO
Inventors: Stephen MITCHLEY; Adam SHEPHERD; David Millward
Original assignee: Jaguar Land Rover Limited
Priority date: 2022-03-28
Filing date: 2023-03-23
Publication date: 2023-10-05
Also published as: GB2617078A; GB202204363D0

Abstract

Aspects of the present invention relate to a fuel cell exhaust system comprising an apparatus (10, 110) for removing water and diluting purged hydrogen (B) in an exhaust gas stream (A), the apparatus comprising a conduit (12) having a first inlet (14, 114) configured to receive an exhaust gas stream (A) and a second inlet (66) configured to receive purged hydrogen (B), a water separation device (38, 56, 156) positioned downstream of the first inlet (14, 114) and upstream of the second inlet (66), and configured to remove water (W) from the exhaust gas stream (A) to produce a drier exhaust gas stream (D), and one or more mixing means (28a, 28b, 30a, 30b, 128a, 128b, 130a, 130b) configured to mix the purged hydrogen (B) and drier exhaust gas stream (D). Also disclosed is a method of removing water (W) and diluting purged hydrogen (B) in an exhaust gas stream and a vehicle (100) comprising the fuel cell exhaust system.

Description

WATER SEPARATOR AND HYDROGEN DILUTION DEVICE

TECHNICAL FIELD

The present disclosure relates to a water separator and hydrogen dilution device. Aspects of the invention relate to an apparatus for removing water and diluting purged hydrogen in an exhaust gas stream, to a method for removing water and diluting purged hydrogen in an exhaust gas stream, to a system comprising the aforementioned apparatus, to a fuel cell exhaust system comprising the aforementioned apparatus and to a vehicle comprising the aforementioned fuel cell exhaust system.

BACKGROUND

A fuel cell is an electrochemical cell that converts chemical energy of a fuel, such as hydrogen, and an oxidizing agent, such as oxygen, into electricity. A fuel cell consists of a negative electrode (or anode) and a positive electrode (or cathode) separated by an ion-conducting electrolyte. A fuel, such as hydrogen, is fed to the anode and air is fed to the cathode. In a hydrogen fuel cell, hydrogen molecules are separated at the anode by a catalyst, into their constituent protons and electrons, each of which takes a different path to the cathode. The electrons travel in an external circuit (supplying power). The protons move through the electrolyte to the cathode, where they combine with oxygen and the electrons (which have travelled through the external circuit) to produce water and heat.

Fuel cells can be used in a wide range of applications, providing power for those applications and have several benefits over conventional combustion-based technologies currently in use in many applications such as vehicles. For example, fuel cells have lower or zero emissions as compared to combustion engines, hydrogen fuel cells emit only water and therefore do not produce carbon dioxide emissions which may contribute to climate change, and fuel cells do not emit air pollutants that create smog and which may be detrimental to health.

Purging of hydrogen from the fuel cell is necessary to prevent fuel cell deterioration and to improve durability of the fuel cell. The purging process involves a controlled release of a proportion of the (gaseous) fuel and/ or oxidant (e.g. air) through an exhaust system. The purging process removes accumulated impurities, water and particulates from the fuel cell and restores fuel cell performance. However, release of hydrogen into the open air may present safety concerns if the concentration of the released hydrogen is above a level which is deemed safe. Currently, it is preferred that concentration of released hydrogen is 4% or less by volume. One method of diluting purged hydrogen in an exhaust gas stream and reducing the concentration of hydrogen released into the atmosphere is to pass the exhaust gas stream containing the purged hydrogen through a long conduit comprising a series of bends. As the exhaust gas stream passes around each of the bends in the long conduit, the bends create turbulence in the exhaust gas stream which mixes the purged hydrogen with air in the exhaust gas stream to which reduces the concentration of released hydrogen as compared to an unmixed stream.

When the hydrogen fuel cell system is applied to a vehicle, the long conduit with bends for mixing the exhaust gas stream is usually disposed along the length of the vehicle, such that advantage is taken of the vehicle’s length to provide numerous bends in the long conduit to improve mixing of the exhaust gases and thus reducing the concentration of hydrogen gas released. A disadvantage with this known arrangement is that the long conduit and multiple bends takes up a significant proportion of available space underneath the vehicle and placement of each of the bends and/or other components fitted to the vehicle’s underside must be carefully considered to ensure that each required component can be accommodated.

A further disadvantage of the aforementioned known method of diluting purged hydrogen in an exhaust gas stream is that water in the exhaust gas stream can reduce the efficacy of mixing of the purged hydrogen and exhaust gas stream. Water in the gas stream may also reduce the homogeneity of the resulting mixed stream of purged hydrogen and exhaust gas. This may cause an inconsistent dilution of purged hydrogen in the exhaust gas stream which is undesirable.

It is an aim of the present invention to address one or more of the disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide an apparatus for removing water and diluting purged hydrogen in an exhaust gas stream, a method for removing water and diluting purged hydrogen in an exhaust stream, a system comprising the apparatus, a fuel cell exhaust system comprising the apparatus and a vehicle comprising the fuel cell exhaust system, as claimed in the appended claims

According to an aspect of the present invention there is provided an apparatus for removing water and diluting purged hydrogen in an exhaust gas stream, comprising: a conduit having a first inlet for receiving an exhaust gas stream and a second inlet for receiving purged hydrogen; a water separation device positioned downstream of the first inlet and upstream of the second inlet, and configured to remove water from the exhaust gas stream to produce a drier exhaust gas stream; and one or more mixing means configured to mix the purged hydrogen and drier exhaust gas stream.

Providing a water separation device to remove a proportion of water from the exhaust gas stream produces a drier exhaust gas stream which improves efficiency of mixing when the drier exhaust gas stream is mixed with the purged hydrogen in the conduit. By positioning the water separation device downstream of the exhaust gas inlet and upstream of the purged hydrogen inlet, water is removed by the water separation device from the exhaust gas stream prior to it being mixed with the purged hydrogen. This improves the rate and efficiency of mixing, as well as improve the homogeneity of the mixed exhaust gas stream and purged hydrogen. By improving the efficiency of mixing, the overall path length required to achieve the desired level of mixing and resultant hydrogen concentration emerging from the end of the mixing path, i.e. conduit, can be reduced as compared to known arrangements, such as an arrangement in which mixing of the gases is achieved in a long conduit comprising a series of bends for mixing the gases.

Optionally, the water separation device may comprise a receiving portion for receiving the exhaust gas stream.

By providing a receiving portion adapted to capture all of the incoming exhaust gas stream, for example by being wider than more downstream section of the water separation device, the exhaust gas stream passes unhindered into the water separation device.

Optionally, the water separation device may comprise a collection portion configured to collect separated water from the exhaust gas stream.

By providing a collection portion, separated water from the exhaust gas stream can be kept separate to the incoming, “wetter” exhaust gas stream and the outgoing “drier” exhaust gas stream and can be more easily removed from the conduit, if required.

Optionally, the water separation device may comprise a mixer configured to deflect the exhaust gas stream prior to removal of water. The mixer creates turbulence in the incoming exhaust gas stream which assists in separation of water from gas in the exhaust gas stream.

Optionally, the mixer may be configured to cause a helical rotating flow of the exhaust gas stream.

The helical rotating flow efficiently removes water from the exhaust gas stream under centrifugal force.

Optionally, the water separation device may comprise a condensation plate.

A condensation plate effectively traps water from the exhaust gas stream to allow drier exhaust gas to emerge from the downstream side of the condensation plate.

Optionally, the mixer may comprise a swirl generator. The swirl generator may be in accordance with known swirl generators.

The swirl generator causes rotation of the exhaust gas flow which assists with mixing of gases and assists with removal of any residual water in the gas flow.

The water separation device may be any form of separation device configured to remove a proportion of water from a gas stream. As non-limiting examples, the water separation device may comprise a centrifugal-type separator, or comprise a condensation-plate type separator.

Optionally, the one or more mixing means may comprise one or more means of deflecting a gas stream, such as but not limited to a conduit, for receiving an exhaust gas stream and purged hydrogen, wherein the conduit comprises one or more bends. Each of the one or more bends may be capable of deflecting the flow of gas within the conduit causing a turbulent flow in the gas stream, resulting in mixing of the exhaust gas stream with the purged hydrogen flow and a dilution in the concentration, by volume, of purged hydrogen within the exhaust gas stream released from a downstream end of the conduit.

The one or more mixing means may comprise one or a plurality of plurality of mixing devices. The plurality of mixing devices may be spaced apart along a longitudinal axis of the conduit.

By providing a plurality of mixing devices, either in a single mixing plate or in a series of mixing plates disposed along the longitudinal axis of the conduit, the amount of turbulence that can be created in the flow of exhaust gas and purged hydrogen in the apparatus is increased, thus improving the mixing of the exhaust gas and purged hydrogen which leads to a reduction or dilution of the concentration of hydrogen present, by volume, in the exhaust gas stream emerging from the apparatus.

Spacing the plurality of mixing devices along a longitudinal axis of the conduit further improves the efficiency of mixing at least in part because the gases are being mixed by each of the plurality of mixing devices at more than one location in the conduit.

The plurality of mixing devices may be disposed on an inner surface of the conduit. The plurality of mixing devices may be disposed around on an inner circumferential surface of the conduit.

Disposing the mixing devices on an inner surface, optionally an inner circumferential surface of the conduit, means that no additional space is taken up by the mixing devices.

The plurality of mixing devices may comprise at least one upstream mixing device and at least one downstream mixing device that is positioned in the conduit downstream of the at least one upstream device, wherein the at least one downstream mixing device is configured to receive a turbulent stream of purged hydrogen and exhaust gas stream deflected from the at least one upstream mixing device.

By arranging at least one downstream mixing device to receive a turbulent stream of purged hydrogen and exhaust gas stream deflected from at least one upstream mixing device, turbulence in the flow of purged hydrogen and exhaust gas in the conduit can be increased, thus increasing the efficiency of mixing.

The downstream mixing device may be configured to deflect the purged hydrogen and exhaust gas stream in a different direction to the turbulent stream of purged hydrogen and exhaust gas stream deflected from the at least one upstream mixing device.

By deflecting the purged hydrogen and exhaust gas stream in different directions in the conduit, turbulence in the stream of purged hydrogen and exhaust gas is increased, thus increasing the efficiency of mixing.

Each of the one or more mixing devices may comprise a plurality of planar and/or curved surfaces for deflecting the purged hydrogen and exhaust gas stream. Providing a plurality of planar and/ or curved surfaces changes the deflection angle of the gases so that the nature of the turbulent mixing can be modified in dependence on the angle of the planar and/or curved surface, to achieve the desired flow/ mixing pattern.

The configuration of the plurality of planar and/or curved surfaces may cause clockwise and/or anti-clockwise air flow.

Clockwise and/or anti-clockwise air flow causes rotational flow of the purged hydrogen and exhaust gas stream which has been found to produce effective mixing. An arrangement comprising both clockwise and anticlockwise rotational flows of gas, such as via a plurality of mixing devices, causes folding or tumbling of the two rotational flows, i.e the purged hydrogen flow and the exhaust gas flow, which significantly improves mixing of the hydrogen and exhaust gas. For example, a combination of a rotational gas flow emerging from one mixing device in a clockwise direction with a rotational flow of gas emerging from another mixing device in an anti-clockwise direction causes effective mixing by folding of the two rotational gas flows which dilutes the concentration of hydrogen in the exhaust gas stream in the mixed gas stream emerging from the conduit.

The plurality of planar and/or curved surfaces may be arranged at one or more inclined angles relative to a longitudinal axis of the conduit. Such a configuration may assist in deflecting the air flow in one or more different directions relative to the longitudinal axis of the conduit. This improves the efficiency of mixing of the purged hydrogen and exhaust gas stream.

The plurality of planar and/or curved surfaces of each of the one or more mixing devices may comprise fins or blades.

The fins or blades of the plurality of planar and/ or curved surfaces of each of the one or more mixing devices may extend radially outward from one or more hubs on each of the one or more mixing devices. This provides a convenient arrangement for providing a plurality of surfaces for deflection of the gases.

The apparatus may be disposed in a fuel cell exhaust system.

Provision of the apparatus in a fuel cell exhaust system enables purged fuel from the fuel cell to be effectively mixed and diluted in the exhaust system prior to release into the atmosphere. The conduit of the apparatus may comprise a drain. The drain may be suitable for draining water from the exhaust gas stream from the conduit.

Provision of a drain in the conduit prevents water removed from the exhaust gas stream from collecting within the conduit.

According to another aspect of the invention, there is provided a method of removing water and diluting purged hydrogen in an exhaust gas stream, the method comprising the steps of: introducing an exhaust gas stream into a conduit; removing water from the exhaust gas stream to produce a drier exhaust gas stream; introducing purged hydrogen into the drier exhaust gas stream; and mixing the purged hydrogen and the drier exhaust gas stream.

The method of the present invention is advantageous over known methods of diluting purged hydrogen in an exhaust gas stream, such as known methods comprising the use of a long conduit having bends therein which cause mixing of gases within the conduit, for a number of reasons. The presence of the water separation device in the conduit in the claimed position means that purged hydrogen is introduced into the exhaust gas stream once a proportion of water has been removed from the exhaust gas, which increases the ease with which the purged hydrogen and exhaust gas stream mix together, as compared to mixing of the purged hydrogen with a non-dried gas stream. This results in an improved efficiency of mixing and improved homogeneity of the mixed purged hydrogen and exhaust gas stream expelled from the conduit. The presence of the one or more mixing devices disposed in the conduit more effectively mixes the purged gases, e.g. purged hydrogen and exhaust gas stream, in the conduit across a shorter path length as compared to the path length required to achieve a comparable level of mixing or dilution in a known system, e.g. a long conduit comprising bends.

A concentration of hydrogen in the mixed purged hydrogen and exhaust gas stream discharged from the conduit may be 4% or less, by volume.

A concentration of 4% or less of purged hydrogen in the exhaust gas stream and discharged from the conduit is optimal according to present emissions standards.

According to another aspect of the invention, there is provided system comprising the apparatus disclosed herein, wherein the system comprises a hydrogen source in fluid communication with at least one inlet of the conduit. According to another aspect of the invention, there is provided system comprising the apparatus disclosed herein, wherein the system comprises a hydrogen source in fluid communication with the second inlet of the conduit.

Optionally, the hydrogen source may comprise at least one hydrogen fuel cell.

According to another aspect of the invention, there is provided a fuel cell exhaust system comprising the apparatus disclosed herein.

Applying the apparatus in a fuel cell exhaust system means that mixing of the purged fuel (e.g. hydrogen) with exhaust gases is more efficient and homogenous as compared to known arrangements in which the exhaust gas stream is not dried before mixing with the purged hydrogen. This reduces the path length required for effective mixing of the drier exhaust gas stream with purged fuel from the fuel cell to achieve a desirable concentration of purged fuel in the mixed fuel and exhaust gas stream emerging from the fuel cell exhaust system.

The fuel cell exhaust system may comprise a hydrogen source in fluid communication with the at least one inlet of the conduit of the apparatus.

The hydrogen source may comprise at least one hydrogen fuel cell.

According to another aspect of the invention, there is provided a vehicle comprising the fuel cell exhaust system disclosed herein.

By applying the apparatus to a vehicle, the overall path length required for effective mixing and achieving the desired levels of dilution of purged hydrogen in the emergent exhaust gas stream from the apparatus as a result of the arrangement of one or more mixing devices in the conduit and the provision of the water separation device to dry the exhaust gas stream, is significantly reduced as compared to known methods of mixing exhaust gases emitted from cars, such as a long conduit extending substantially the length of the vehicle. The shorter path length required by the apparatus only takes up a fraction of the length of the vehicle, in contrast to the known, long conduit apparatus, thus freeing up vital space for other components on the underside of the vehicle. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows an exploded view of another embodiment of apparatus in accordance with the present invention, comprising a condensation-plate type water separation device and a plurality of mixing devices positioned in a conduit;

Figure 2 shows an exploded view of an embodiment of apparatus in accordance with the present invention, comprising a centrifugal type water separation device and a plurality of mixing devices positioned in a conduit;

Figure 3 shows a cross-sectional schematic illustration of an embodiment of apparatus in accordance with the present invention, comprising a centrifugal type water separation device, and illustrating the various flow paths within the embodiment of the apparatus during use and thus illustrating an embodiment of method in accordance with the present invention;

Figure 4 shows a perspective view of a downstream face of the plurality of mixing devices shown in Figure 1 and in Figure 2;

Figure 5 shows a side view of another embodiment of apparatus in accordance with the present invention, comprising a housing in the form of a conduit in which the mixing devices shown in Figure 4 are arranged in series along a longitudinal axis of the conduit and a centrifugal-type water separation device is positioned in the conduit between some of the mixing devices; Figure 6 shows a schematic representation of the profile of some of the individual fins of the plurality of mixing devices shown in Figure 4;

Figure 7 shows a schematic illustration of a vehicle to which an apparatus or a system according to the present invention may be fitted and/ or which may employ the method of the present invention; and

Figure 8 shows a flow chart of an embodiment of a method in accordance with the present invention.

DETAILED DESCRIPTION

An apparatus in accordance with embodiments of the present invention is described herein with reference to the accompanying Figures. As described with reference to Figure 7, the apparatus can be installed in a vehicle. The vehicle 100 in the embodiment relating to Figure 7 is an automobile, such as a wheeled vehicle, but it will be understood that the apparatus may be used in other types of vehicle, such as but not limited to watercraft or any other type of vehicle having an exhaust gas system. Similarly, the method, system and fuel cell system described herein can be applied to a vehicle, such as a wheeled vehicle as shown in Figure 6, but as with the apparatus, the method, system and fuel cell system described herein can be applied to other types of vehicle such as but not limited to watercraft or any other type of vehicle having an exhaust gas system.

The apparatus 10 of the present invention is configured to dilute reacted fuel gas, such as hydrogen in the present example, and optionally other contaminants from a fuel cell to levels which are considered to be safe for release into the atmosphere. The reacted fuel gas is released from the fuel cell (not shown) when a valve (not shown) coupled to the fuel cell is opened. The valve is coupled to a conduit which fluidly connects the fuel cell and the apparatus 10 of the present invention so that when the valve is opened, the reacted fuel gas can transfer from the fuel cell into the apparatus 10 of the present invention via the conduit.

Two embodiments of an apparatus 10, 110 according to the present invention are shown in each of Figures 1 and 2, respectively. In each embodiment, the apparatus 10, 110 comprises a housing 12, 112 which generally defines a conduit 12, 112. The significant difference between the embodiment of Figure 1 and the embodiment of Figure 2 is that the embodiment illustrated in Figure 1 comprises a generally planar water separation device 38 in the form of a condensation plate whereas the embodiment illustrated in Figure 2 comprises a centrifugaltype water separation device 156. Otherwise, the remaining features of each embodiment of the invention are generally the same or similar and thus the same reference numerals are used to identify common features between the embodiments, with Figure 2 reference numerals being preceded by “1”. In each embodiment of the present invention, the water separation device, irrespective of its form, is positioned downstream of the exhaust input and upstream of the hydrogen input in the conduit, as will be explained,

Referring to Figures 1 , 2, 3 and 4, the housing 12, 112 comprises a first part 12a, 112a and a second part 12b, 112b. At the upstream end of the first part 12a, 112a is a first inlet 14, 114 for receiving an exhaust gas stream A and the downstream end of the first part 12a, 112a comprises an annular flange 16, 116 for securing the first part 12a, 112a to a corresponding annular flange 18, 118 on the second part 12b, 112b of the housing 12, 112b. The conduit 12, 112 comprises a second inlet 66 for receiving purged hydrogen, which is shown on Figure 1. The second inlet 66 is positioned downstream of the first inlet 14, 114 and upstream of a plurality of mixing devices 28a, 28b, 30a, 30b, as will be described.

The second part 12b, 112b of the housing 12, 112 comprises an outlet 20, 120 at the downstream end for discharging the exhaust gas stream A and the purged hydrogen B after they have been mixed together in the housing or conduit 12, 112 as will be explained. The upstream end of the second part 12b, 112b of the housing 12, 12 comprises an annular flange 18, 118. The first and second parts 12a, 12b, 112a, 112b of the housing 12, 112 are secured together using a plurality of fasteners 22, 122 to couple the annular flanges 16, 18, 116, 118 of each of the first and second parts 12a, 12b, 112a, 112b together. Each of the first housing part 12a, 112a and second housing part 12b, 112b comprises a pair of mounting brackets (not shown) for mounting the housing or conduit 12, 112 onto a surface. In the present example, the mounting brackets are intended to secure the housing 12, 112 to a surface on the underside 100a of a vehicle 100, such as that schematically shown in Figure 7. It is to be understood that the configuration of the housing 12, 112 in the present embodiment is not intended to be limiting. Other configurations of housing or conduit 12, 112 may also be suitable for use in accordance with the present apparatus 10, 110.

Positioned inside the housing or conduit 12, 112 of the present embodiment is a plurality of mixing devices 28a, 28b, 30a, 30b, as illustrated in Figure 3. Other embodiments of the apparatus 10 may comprise a single mixing device. In the present embodiment, the plurality of mixing devices 28a, 28b, 30a, 30b, 128a, 128b, 130a, 130b, are secured to a generally planar, rectangular mounting plate 32, 132 which is positioned substantially mid-way between the inlet 14, 114 of the first part 12a, 112a of the housing 12, 112 and the outlet 20, 120 of the second part 12b, 112b of the housing 12, 112. It is to be understood that this positioning is not necessarily essential and that the plurality of mixing devices 28a, 28b, 30a, 30b, 128a, 128b, 130a, 130b, may be mounted elsewhere in the housing or conduit 12, 112. It is also to be understood that the shape and/ configuration of the mounting plate 32, 132 or, more generally, mounting means for mounting one or more mixing devices, may differ from that described and illustrated in respect of the present embodiment.

The plurality of mixing devices 28a, 28b, 30a, 30b, 128a, 128b, 130a, 130b, are generally positioned to intersect the flow of the exhaust gas stream A and purged hydrogen B, respectively, each of which enters the housing 12, 112 at distinct locations in the housing 12, 112, as can be seen for example in Figure 1. The exhaust gas stream A enters the housing, or conduit 12, 112 through the inlet 14, 114 of the first housing part 12a, 112a. The inlet 14, 114 is positioned upstream of a water separation device 38, 38’, 156 which is positioned in the conduit 12, 112 for removing water from the incoming exhaust gas stream A, as will be explained. The purged hydrogen B is introduced into the conduit 12, 112 via a separate inlet 66 which opens into the conduit in a position which is downstream of the water separation device 38, 38’, 156 and upstream of the mixing devices 28a, 28b, 30a, 30b, 128a, 128b, 130a, 130b, such that the flow of purged hydrogen B does not pass through the water separation device 38, 38’, 156 but does pass through the mixing devices 28a, 28b, 30a, 30b, 128a, 128b, 130a, 130b, as is explained below.

In the present embodiment, the aforementioned intersection of the gas stream is achieved by mounting the plurality of mixing devices 28a, 28b, 30a, 30b, 128a, 128b, 130a, 130b, on first and second mixing plates 34, 36, 134, 136 which extend generally perpendicularly with respect to the planar mounting plate 32, 132 as can be seen for example on Figures 1 , 2 and 4. This is explained in more detail below. The planar mounting plate 32, 132 is then mounted in the housing or conduit 12, 112 such that the longer side of the rectangular mounting plate 32, 132 extends along a longitudinal axis of the housing or conduit 12, 112, the longitudinal axis being generally in the direction of the arrow labelled C on each of Figures 1 and 2.

The mounting plate 32, 132 is sized and shaped so as to conform with the internal dimensions of the housing or conduit 12, 112. Similarly, the size and shape of the plurality of the mixing plates 34, 36, 134, 136 also conforms to the internal dimensions of the housing 12, 112. By ensuring that the dimensions of the mixing plates 34, 36, 134, 136 and mounting plate 32, 132 onto which they are secured conform to the internal dimensions of the housing or conduit 12, 112, all or substantially all, of the exhaust gas stream A and purged hydrogen B is directed through the mixing devices 28a, 28b, 30a, 30b, 128a, 128b, 130a, 130b, and is unable to bypass the mixing plates 34, 36, 134, 136. This arrangement ensures thorough mixing of the exhaust gas stream A and the purged hydrogen B within the housing or conduit 12, 112. It is to be understood that in one or more other embodiments, it may be the shape and/ or dimensions of the one or more mixing devices which are configured to conform to the internal dimensions of the housing or conduit 12, 112, for example, in an embodiment in which the one or more mixing devices are mounted directly to the housing or conduit 12, 112 instead of on mixing plates as shown in the present example.

In the embodiment shown in Figure 1 , the apparatus 10 is provided with a generally planar water separation device 38 positioned between the inlet 14 of the first part 12a of the housing 12 and the mixing devices 28a, 28b, 30a, 30b, 128a, 128b, 130a, 130b. The generally planar water separation device 38 is substantially in accordance with a known condensation platetype water separator. A purged hydrogen stream B is introduced into the conduit downstream of the water separation device 38, as illustrated in Figure 1 .

In the embodiment shown in Figure 2 and as shown in Figure 3 the apparatus is provided with a centrifugal-type water separation device 156 positioned downstream of the exhaust gas stream A inlet and upstream of an inlet 66 for receiving purged hydrogen gas B. The inlet 66 is in fluid communication with the internal cavity of the conduit and introduces the purged hydrogen B into the conduit in the region of the “drier” exhaust gas stream D emerging from the downstream side of the water separation device 56, 156.

In either of the embodiments shown in Figures 1 and 2, respectively, and in accordance with other embodiments of the present invention, the water separation device 56, 38, 156 removes a proportion of water from the exhaust gas stream A before the “drier” exhaust gas stream D passes through to the mixing devices 28a, 28b, 30a, 30b, 128a, 128b, 130a, 130b.

The water separation device 38 in the example embodiment of Figure 1 is a known condensation plate and therefore will not be described in detail, but in general terms, comprises a filter screen which traps a proportion of the water from the exhaust gas stream A as the exhaust gas stream A passes through the filter, which “dries” the exhaust gas stream prior to it reaching the mixing devices 28a, 28b, 30a, 30b and prior to the introduction of purged hydrogen into the housing or conduit 12. It is to be appreciated that any water separation device may be employed in the present apparatus and that the examples of water separation devices described herein are by way of non-limiting example.

In the example embodiment shown in Figure 2, the water separation device 156 is mounted onto an end plate 140 at an upstream end of the rectangular mounting plate 132 and upstream of the mixing devices 128a, 128b, 130a, 130b so as to intersect the flow of the exhaust gas stream A entering the housing, or conduit 112. The end plate 140 extends from the planar rectangular mounting plate 132 at an angle between around 90 degrees and 110 degrees relative to the mounting plate 132 so as to be able to intersect the incoming exhaust gas stream A when the mounting plate 132 is situated in the housing or conduit 112. As with the mixing plates 34, 36, the shape and configuration of the end plate 140 conforms to the internal dimensions of the housing or conduit 112 so as to force all or substantially all of the exhaust gas stream A through the water separation device 156 and to prevent any of the exhaust gas stream A from bypassing the water separation device 156.

It is to be appreciated that varying housing/ conduit/ exhaust passage geometries will require an alteration of the water separation device 38, 38’, 156 and/ or mixing devices 28a, 28b, 30a, 30b, 128a, 128b, 130a, 130b and/ or mixing plates 34, 36, 134, 136 and/ or mounting plate 32, 132 to enable each of the aforementioned components to fit tightly within the housing or conduit 12, 112 or an exhaust passage.

By way of example, Figure 5 illustrates, in cross section, an embodiment of apparatus 10 comprising a plurality of mixing devices 28a’, 30a’ spaced apart in a conduit 12’. In this example, a first mixing device 28a’ is positioned upstream of a second mixing device 30a’ within the conduit 12’, and a water separation device 38’ is positioned adjacent the upstream side of the downstream, i.e. second mixing device 30a’. The mixing devices 28a’, 30a’ are, in the present example, of the same configuration as shown in the embodiment in each of Figure 1 , Figure 2 and Figure 4. The water separation device 38’ in the embodiment shown in Figure 5 is generally conical, in contrast to the generally planar water separation device 38 of the embodiment of Figure 1. A swirl generator 54, schematically illustrated in Figure 3, rotates the incoming exhaust gas stream A. The rotating exhaust gas stream A subsequently enters the water separation device 38’. The generally conical shape of the water separation device 38’ causes the incoming rotating gas stream to be deflected around the inner surface of the conical separation device 38’ which maintains the rotational flow of the exhaust gas stream A initiated by the swirl generator. As the gas stream A rotates in the separator 38’, water present in the gas stream A moves radially outward under centrifugal force, causing it to contact the inner surface of the water separation device 38’. The water droplets W then move downwardly towards a drain 42 in the conduit 12 and underlying the water separation device, which allows water collected by the separation device 38’ to drain out of the conduit.

The inventors have found that by positioning a water separation device downstream of the exhaust gas inlet 14 and upstream of the purged hydrogen inlet 66, mixing and thus dilution of the purged hydrogen B in the exhaust gas stream A is more effective as compared to an arrangement in which the purged hydrogen is mixed with the exhaust gas stream prior to removal of water from the exhaust gas. This is because the exhaust gas stream emerging from the downstream side of the water separation device is drier than the exhaust gas stream prior to passing through the water separation device. The drier exhaust gas stream is able to more readily mix with the purged hydrogen gas, which produces a more homogenous mixture of exhaust gas and purged hydrogen, which in turn results in a more consistent dilution of purged hydrogen within the exhaust gas stream emerging from the apparatus.

The inventors also found that by positioning the one or more mixing means, which may include simple mixing means such as one or more bends in a conduit (such as an exhaust tail pipe), downstream of the “drier” exhaust gas stream and purged hydrogen inlet, mixing of the “drier” exhaust gas stream and purged hydrogen could be achieved more quickly because the drier exhaust gas stream more readily mixed with the purged hydrogen as compared to an exhaust gas stream from which the water had not been removed. An effect of this is that the path length of the conduit, which may, in an example embodiment, be in the form of an exhaust tail pipe, can be reduced as compared with known arrangements. A further effect of positioning the water separation device downstream of the exhaust gas inlet and upstream of the purged hydrogen inlet is that removal of a significant proportion of water from the exhaust gas stream prior to mixing it with the purged hydrogen produces a more homogenously mixed gas stream.

The mixing devices of the present embodiment of the apparatus will now be described in more detail and with reference to Figures 1 , 2 and 4 as illustrative examples. The embodiments shown in Figures 1 and 2 each comprises four static mixing devices 28a, 28b, 30a, 30b, 128a, 128b, 130a, 130b each of which, in very general terms, resembles a fan-like structure having a plurality of inclined surfaces S, S’ extending radially outward from a hub 44. The plurality of inclined surfaces S, S’ are referred to hereinafter as vanes S, S’. In the present embodiment, each vane S, S’ comprises at least one curved surface, as will be explained, although vanes comprising only generally planar surfaces may also be used in one or more embodiments. The vanes S, S’ are static. This arrangement is most clearly shown in Fig. 3. The four mixing devices 28a, 28b, 30a, 30b, 128a, 128b, 130a, 130b are arranged such that two mixing devices 28a, 28b, 128a, 128b are formed spaced apart side by side on a first mixing plate 34, 134 which extends substantially perpendicularly from the planar mounting plate 32, 132 and a further two mixing devices 30a, 30b, 130a, 130b are formed spaced apart and side by side on a second mixing plate 36, 136 which extends substantially perpendicularly from the planar mounting plate 32, 132. The first and second mixing plates 34, 36, 134, 136 are spaced apart along a longitudinal axis (in the direction of arrow, C) of the conduit 12, 112 as shown in the Figures.

It is to be appreciated that other embodiments may have a different arrangement of mixing devices as compared with that of the present embodiment. For example, one or more embodiments may comprise a single mixing device which may or may not be mounted on a mixing plate, or may comprise a plurality of mixing devices having one or more mixing devices disposed on one or more mixing plates disposed throughout the conduit. One or more embodiments may use a series of bends in conduit to achieve mixing, for example such as embodiment relating to an exhaust tail pipe extending substantially the length of a vehicle to which it is fitted and comprising a series of bends for deflecting air and mixing exhaust gases within the tail pipe.

In the present example, the each mixing device 28a, 28b, 30a, 30b, 128a, 128b, 130a, 130b is integrally joined with its respective mixing plate 34, 36, 134, 136. However, in another example, each mixing plate 34, 36, 134, 136 may comprise one or more apertures into which a separate mixing device can be securely mounted. As best appreciated from Figures 1 , 2 and 4, each mixing device 28a, 28b, 30a, 30b, 128a, 128b, 130a, 130b comprises an inlet or upstream side 46, 146 and an outlet or downstream side 48, 148.

The inlet or upstream side 46, 146 comprises, in the present example, a recessed annular flange 50, 150 which is integrally joined with the outer-most edge of the upstream side of each of the vanes S, S’. The recessed portion of the flange 50, 150 projects away from the downstream side of the mixing plate 34, 36, 134, 136 as best seen on Figures 1 and 2. The inner-most edge of each of the vanes is connected to a central hub 44, 144 around which the vanes S, S’ are radially mounted. The hub 44, 144 is generally cone-shaped on the inlet surface and extends from the inlet or upstream side in the direction of the incoming exhaust gas stream A and purged hydrogen flow B, as shown in Figures 1 and 2. In the present example, each of the mixing devices 28a, 28b, 30a, 30b, 128a, 128b, 130a, 130b comprises nine static vanes S, S1 extending radially from the central hub 44. As an example, this configuration of mixing devices can be used in conjunction with a mass flow rate of purged hydrogen of 75kg/ hr.

On the downstream or outlet side of each mixing device 28a, 28b, 30a, 30b, 128a, 128b, 130a, 130b the static vanes S, S’ extend away from the downstream face 48, 148 of each mixer plate 34, 36, 134, 136 such that they project from a first point on the annular flange 50, 150 on downstream face of the mixing plate 34, 36, 134, 136 in a plane that is generally perpendicular to the upstream and downstream faces 46, 48, 146, 148 of the mixing plate 34, 36, 134, 136 before curving back towards a second point on the annular flange 50, 150 on the downstream side of the mixer plate 34, 36, 134, 136 to define a vane S, S1 having a generally concave first, upstream side and corresponding convex second, downstream side. The vanes S, S1 are spaced apart around the annular flange.

The axial spacing 52 between the static vanes S, S’ creates space through which the exhaust gas stream A and purged hydrogen B can flow from the upstream side of the each mixing device 28a, 28b, 30a, 30b as the exhaust gas stream A and purged hydrogen B are deflected off the concave and convex surfaces of each vane S, S1 . As the exhaust gas stream A and purged hydrogen B moves through each mixing device 28a, 28b, 30a, 30b, 128a, 128b, 130a, 130b the inclined surface of each vane causes the exhaust gas stream A and purged hydrogen flow B to change direction which causes mixing of the exhaust gas stream A and purged hydrogen B.

On the first mixing plate 34, 134 the vanes of one mixing device 28a, 128a deflect the incoming drier exhaust gas stream and purged hydrogen in an anti-clockwise direction and the vanes of the second mixing device 28b, 128b are configured to deflect the incoming drier exhaust gas stream D and purged hydrogen B in a clockwise direction, to produce a tumbling flow ABT of mixed exhaust gas and purged hydrogen AB emerging from the downstream side of the first mixing plate 34, 134. On the second mixing plate 36, 136 the mixing devices 30a, 30b, 130a, 130b are configured such that the vanes of one mixing device 30a, 130a deflect the incoming mixed drier exhaust gas stream and purged hydrogen AB in an anti-clockwise direction and the vanes of the second mixing device 30b, 130b are configured to deflect the incoming mixed drier exhaust gas stream and purged hydrogen AB in a clockwise direction, to create further turbulence in the tumbling flow ABT of mixed exhaust gas and purged hydrogen AB. The turbulent flow ABT of mixed exhaust gas and purged hydrogen AB is released out of the conduit 12, 112 via outlet 20, 120 positioned at the downstream end of the conduit 12, 112.

It is to be appreciated that other embodiments of mixing may comprise a different number of vanes, or may arrange the vanes, or more generally a plurality of inclined surfaces in a different configuration so as to achieve mixing of the exhaust gas stream and purged hydrogen.

The angle and shape of each of the inclined surfaces or vanes S, S’ may differ between embodiments of mixing device, to cause a suitable deflection to achieve the required mixing pattern of the exhaust gas stream and purged hydrogen. The vanes S, S’ may be configured to have generally planar faces in one or more embodiments. Figure 6 illustrates the profile of some of the outer-most tips 52 of the surfaces of the vanes S, S’ of the mixer devices shown in Fig. 4.

The effect of the positioning of the water separation device relative to the exhaust gas and purged hydrogen inputs will be described in more detail and with reference to Figure 3, as an example embodiment. Figure 3 also illustrates a method according to an embodiment of the present invention, as will be described. Referring to the embodiment of Figure 3, the apparatus 10 of the present invention is shown comprising a centrifugal-type water separation device 56.

In accordance with an embodiment of the method and apparatus of the present invention, the exhaust gas stream A enters a swirl generator 54 in the water separation device 56 which is upstream of the plurality of mixing devices 28, 30. The mixing devices 28, 30 in the present example are as per those described above and illustrated in Figures 1 , 2 and 4. The swirl generator 54 is in accordance with known swirl generators 54 and so will not be described in detail. The swirl generator 54 is configured to receive a generally laminar flow of exhaust gas stream A and rotate the exhaust gas stream A to produce a swirling flow of exhaust gas A. The swirling motion causes water droplets W in the exhaust gas stream W to be forced radially outward out of the exhaust gas stream A, as they are heavier than the remaining exhaust gases, so that they collect on the inner surface of the water separation device 56, which, in the present embodiment, is generally conical in shape and comprises an inwardly extending annular rim 58 which extends inwardly from an outer wall 62 of the water separation device 56 and towards the upstream end of the conduit 12, terminating before it reaches a downstream side of the swirl generator 54, to define an inner wall 60 of the water separation device 56 which is spaced apart from the outer wall 62. The outer wall 62 may or may not be integrally formed with the conduit 12.

For ease of reference, the “incoming” exhaust gas stream which comprises the full amount of water discharged from the exhaust gas system is identified on the Figures as A, whereas the “drier” exhaust gas stream emerging from the water separation device is identified as D. Mixed exhaust gas and purged hydrogen is identified as AB.

The inwardly extending annular rim 58 prevents collected water droplets W from being forced through the conduit 12 under the pressure associated with the exhaust gas. Instead, the collected water droplets W are able to drain out of the water separation device 56 and the conduit 12 via a drain 64, 164 which underlies a part of the inwardly extending annular rim 58 and inner wall 60.

The exhaust gas stream D emerging from the downstream side of the water separation device 56 is therefore drier than the exhaust gas stream A entering the swirl generator 54 on the upstream side of the water separation device 56. This can be advantageous in that the drier exhaust gas stream D improves ease of mixing with purged hydrogen B as compared to an exhaust gas stream having a higher water content.

The conduit 12 is provided with an inlet 66 for introducing purged hydrogen B into the conduit. The inlet 66 is positioned downstream of the water separation device in the present embodiment. This positioning can be advantageous in that the purged hydrogen B is introduced to the drier exhaust gas stream D and so may more easily mix. However, the effective mixing provided by the present invention is achieved by the one or more mixing devices which are positioned downstream of the purged hydrogen inlet 66, and is not necessarily dependent on the presence of the water separation device 56 in the apparatus 10 to achieve effective mixing, however, the combination of water separation device and or more mixing devices achieves a thorough and more homogenous mixture of purged exhaust gas and hydrogen as compared to mixing the purged hydrogen and exhaust gas stream components without “drying” the exhaust gas stream first.

The purged hydrogen B initially combines with the drier exhaust gas stream D emerging from the downstream side of the water separation device 56 before, under pressure from the exhaust system, the drier exhaust gas stream D and purged hydrogen B move downstream towards the first upstream mixing device 28. The first, upstream mixing plate 34 is in accordance with the embodiment of mixing plate 34 shown on Figure 4 and thus is configured so that the vanes of one mixing device 28a on the mixing plate 34 deflect the incoming drier exhaust gas stream and purged hydrogen in an anti-clockwise direction and the vanes of the second mixing device 28b on the mixing plate 34 are configured to deflect the incoming drier exhaust gas stream D and purged hydrogen B in a clockwise direction, to produce a tumbling flow of mixed exhaust gas and purged hydrogen AB emerging from the downstream side of the first mixing plate 34.

The second mixing plate 36 which comprises two mixing devices in accordance with the embodiment of mixing plate 36 shown on Figure 4, receives the emergent mixed exhaust gas and purged hydrogen AB from the downstream side of the first mixing plate 34. As with the first mixing plate 34, the second mixing plate 36 is configured so that the vanes of one mixing device 30a on the mixing plate deflect the incoming mixed drier exhaust gas stream and purged hydrogen AB in an anti-clockwise direction and the vanes of the second mixing device 30b on the mixing plate 36 are configured to deflect the incoming mixed drier exhaust gas stream and purged hydrogen AB in a clockwise direction, to create further turbulence in the tumbling flow of mixed exhaust gas and purged hydrogen AB. The turbulent flow of mixed exhaust gas and purged hydrogen AB is released out of the conduit 12 via outlet 20 positioned at the downstream end of the conduit.

It is to be appreciated that other embodiments of mixing devices may be configured to deflect the exhaust gas stream and purged hydrogen in a different manner which may or may not include a rotational flow element as per the present embodiment. In general terms, the mixing devices are configured to receive a flow of gas, either substantially laminar or non-laminar in flow, and deflect the received flow to produce a turbulent flow, i.e. a flow in different directions, which may or may not have a rotational element as per the tumbling flow described in relation to the present example.

Figure 8 illustrates a method 200 according to an embodiment of the present invention. The method 200 comprises introducing 202 an exhaust gas stream into a conduit 12, removing 204 water W from the exhaust gas stream A using a water separation device 38, 156 positioned in the conduit 12 to produce a drier exhaust gas stream D, introducing 206 purged hydrogen B into the drier exhaust gas stream D, mixing 208 the purged hydrogen B and the drier exhaust gas stream D in the conduit 12, and discharging 210 the mixed purged hydrogen and drier exhaust gas stream AB from the conduit 12.

The discharge step 210 in Figure 8 which includes discharging 210 the mixed purged hydrogen and exhaust gas stream AB from the conduit 12 is intended to illustrate an example of a flow path taken by the mixed purged hydrogen and exhaust gas stream after the mixing stage within the conduit 12 when the method 200 is in use in a particular application, such as in an exhaust gas system. However, it is to be appreciated that the step 210 of discharging the mixed purged hydrogen and exhaust gas stream AB from the conduit 12 is not an essential step of the invention.

The position of the water separation device downstream of the exhaust gas inlet 14 and upstream of the purged hydrogen inlet 66, allows for more effective mixing and thus dilution of the purged hydrogen B in the exhaust gas stream A as compared to an arrangement in which the purged hydrogen is mixed with the exhaust gas stream prior to removal of water from the exhaust gas. By arranging the water separation device to “dry” the exhaust gas stream before the purged hydrogen is introduced into the conduit for mixing, the rate and homogeneity of mixing of the exhaust gas stream and purged hydrogen is increased, which improves the efficiency of mixing. A technical effect of this is that the path length of the conduit, which may, in an example embodiment, be in the form of an exhaust tail pipe, can be reduced as compared with known arrangements.

This above-mentioned technical effect can be further supplemented by providing a plurality of mixing devices that are configured to deflect, i.e. change the direction of the gas stream flow, in the conduit as described herein, to further improve efficiency of mixing of the drier exhaust gas stream and purged hydrogen and thus also enables effective mixing of the purged hydrogen with an exhaust gas stream across a much smaller path length as compared with an arrangement which comprises a longer path length having alternative mixing means such as bends.

The addition of a plurality of mixing devices as described herein, either in a single mixing plate or in a series of mixing plates disposed along the longitudinal axis of the conduit increases the amount of turbulence that can be created in the flow of exhaust gas and purged hydrogen in the apparatus, thus even further improving the technical effect of the present invention. Therefore, it will be appreciated that employing a plurality of mixing devices either in a single plane or on a single mixing plate in the conduit and/or by providing a series of mixing devices disposed along the longitudinal axis of the conduit, the path length required for effective mixing and achieving the desired levels of dilution of purged hydrogen in the emergent exhaust gas stream from the apparatus, can be substantially reduced. This is of particular benefit when the apparatus is used in applications where space is at a premium, for example on the underside of a vehicle, such as that illustrated in Figure 7. Instead of employing, for example, a long conduit extending substantially the length of the vehicle and comprising bends for creating turbulence to mix various exhaust gases, the present invention can be applied to achieve effective mixing of the exhaust gas stream and purged hydrogen across a much smaller path length and thus takes up only a fraction of the length of the vehicle, thereby freeing up vital space for other components on the underside of the vehicle. By combining the one or more mixing devices with a water separation device in the apparatus as described herein, the aforementioned technical effects of the invention are further enhanced due to the increased ease of mixing a “drier” exhaust gas stream with purged hydrogen.

As a further consequence of the reduced path length, design considerations for accommodating the various components on the underside of the vehicle are significantly simplified by using the present invention, as it is no longer necessary for designers to have to accommodate a long exhaust conduit with its multiple bends that traditionally are required to extend substantially the length of the vehicle.

Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

1. A fuel cell exhaust system comprising an apparatus (10, 110) for removing water and diluting purged hydrogen in an exhaust gas stream, the apparatus comprising: a conduit (12, 112) having a first inlet (14, 114) configured to receive an exhaust gas stream (A) and a second inlet (66) configured to receive purged hydrogen (B); a water separation device (38, 56, 156) positioned downstream of the first inlet (14, 114) and upstream of the second inlet (66), and configured to remove water from the exhaust gas stream (A) to produce a drier exhaust gas stream (D); and one or more mixing means (28a, 28b, 30a, 30b, 128a, 128b, 130a, 130b) configured to mix the purged hydrogen (B) and drier exhaust gas stream (D).

2. A system according to claim 1 , wherein the water separation device (38, 56, 156) comprises a receiving portion configured to receive the exhaust gas stream (A).

3. A system according to claim 2, wherein the water separation device (38, 56, 156) comprises a collection portion configured to collect separated water from the exhaust gas stream (A).

4. A system according to claim 2 or claim 3, wherein the water separation device (38, 56, 156) comprises a mixer (54) configured to deflect the exhaust gas stream (A) prior to removal of water (W).

5. A system according to according to claim 4, wherein the mixer (54) is configured to cause a helical rotating flow of the exhaust gas stream (A).

6. A system according to claim 5, wherein the mixer (54) comprises a swirl generator.

7. A system according to claim 1 or claim 2, wherein the water separation device (38, 56, 156) comprises a condensation plate.

8. A system according to of any of claims 1 to 7, comprising a hydrogen source in fluid communication with the second inlet (66) of the conduit (12, 112).

9. A system according to claim 8, wherein the hydrogen source comprises at least one hydrogen fuel cell.

10. A method of removing water and diluting purged hydrogen in an exhaust gas stream, the method comprising the steps of: introducing an exhaust gas stream (A) into a conduit (12, 112); removing water (W) from the exhaust gas stream (A) to produce a drier exhaust gas stream (D); introducing purged hydrogen (B) into the drier exhaust gas stream (D); mixing the purged hydrogen (B) and the drier exhaust gas stream (D).

11. A method as claimed in claim 11 , comprising discharging the mixed purged hydrogen and drier exhaust gas (AB) from the conduit (12, 112), wherein the concentration of hydrogen (B) in the mixed purged hydrogen and drier exhaust gas (AB) discharged from the conduit (12, 112) is 4% or less, by volume.

12. A vehicle (100) comprising the fuel cell exhaust system of any of claims 1 to 9.