Exhaust fluid injector

Abstract

An exhaust fluid injector (e.g. ammonia or urea) plate 102 for an exhaust fluid vortex mixing conduit (fig.1, 108). The exhaust fluid injector plate comprising an injection aperture 202 and a pluralit

Description

Field of the disclosure The present disclosure relates to an apparatus for treating exhaust gases emitted during the operation of an internal combustion engine. In particular, the present disclosure relates to an exhaust fluid injector plate for an exhaust fluid injector. Background Internal combustion engines output various substances when burning fuel, such as diesel, petrol and / or alternative fuels such as hydrogen. An aftertreatment system may be provided to process one or more of the output substances. This processing may assist in meeting current and future emissions legislation. Most commonly those substances comprise hydrocarbons (HC), carbon monoxides (CO), mono-nitrogen oxides (NOx) and particulate matter, such as carbon (C), a constituent of soot. The emission of some of those substances may be reduced by careful control of the operating conditions of the engine, but usually it is necessary to provide an aftertreatment system downstream of the engine to treat at least some of those substances entrained in the exhaust fluid. For example, it is known to reduce or eliminate mono-nitrogen oxides (NOX) in diesel combustion emissions by conversion to diatomic nitrogen (N2) and water (H2O) by catalytic reaction with chemicals such as ammonia (NH3) entrained in the exhaust fluid. Generally, ammonia is not present in exhaust gases and must therefore be introduced upstream of a catalyst, typically by injecting an exhaust fluid, for example a reductant such as a urea solution, into the exhaust gas which decomposes into ammonia at sufficiently high temperatures. By this method, exhaust gases can be treated, meaning that a proportion of the substances which would otherwise be released to atmosphere are instead converted to nitrogen (N2) and water (H2O). Inefficient mixing of the exhaust gas with the exhaust fluid and inefficient decomposition of urea into ammonia may result in exhaust fluid collecting on surfaces of the aftertreatment system. This in turn can lead to solid deposits (e.g. urea) being formed on surfaces of the aftertreatment system. The accumulation of deposits on surfaces of the aftertreatment system, can cause blocking of apertures and conduits or affect the performance of the aftertreatment system. Deposits may also be more likely to form when the temperature of an aftertreatment system is relatively low (e.g. following ignition of the engine). To reduce or eliminate the formation of deposits at relatively low temperatures, the amount of exhaust fluid injected at relatively low temperatures of the aftertreatment system may be reduced. As such, it may be challenging to provide sufficient mixing of exhaust fluid and exhaust gas when operating the aftertreatment system at relatively low temperatures. US2023065989A1 discloses a mixer, a mixer assembly and a mixing method in which the mixer comprises a shell defining a first space, the first space receives engine exhaust, and the shell has a mounting area located on a wall of the shell; a doser mounting base arranged in the mounting area for mounting the doser, wherein the doser mounting base comprises a spray inlet as an inlet end for the spray that is sprayed by the doser entering the first space, and the doser mounting base further comprises a first swirl structure that surrounds the spray inlet to make the exhaust form a swirl around the spray inlet. Against this background, there is provided an improved, or at least commercially relevant alternative exhaust fluid injector plate. Summary of the disclosure According to a first aspect, an exhaust fluid injector plate for an exhaust fluid vortex mixing conduit is provided. The exhaust fluid injector plate defines: an injection aperture through the exhaust fluid injector plate. The exhaust fluid injector plate comprises: a plurality of exhaust gas directing vanes, each exhaust gas directing vane protruding from a flow surface of the exhaust fluid injector plate and extending across the flow surface in a spiral trajectory about the injection aperture. The exhaust fluid injector plate is for an exhaust fluid vortex mixing conduit which mixes a vortex exhaust gas flow with an exhaust fluid. In such an arrangement, an exhaust fluid injector injects exhaust fluid through the injection aperture into a vortex exhaust gas flow. Pressure and velocity of the exhaust gas flow may vary across the vortex exhaust gas flow. For example, the velocity and / or pressure of the exhaust gas may be lower towards a centre of the vortex exhaust gas flow. In some embodiments, the exhaust fluid may be injected into a relatively low pressure and / or a relatively low velocity region of the vortex exhaust gas flow (e.g. towards the centre). As a consequence of the relatively low pressure and / or relatively low velocity, the rate of formation of exhaust fluid deposits on surfaces of the exhaust fluid mixing conduit / exhaust fluid injector plate may be increased. Similarly, where exhaust gas recirculates about the injection aperture, the rate of formation of exhaust fluid deposits on surfaces of the exhaust fluid mixing conduit / exhaust fluid injector plate may be increased. For example, deposits can accumulate on or around the injection aperture, which may cause blockages and stoppages of the exhaust fluid injector. Additionally, as deposits form more easily at lower temperatures, it may be challenging to inject sufficient exhaust fluid whilst reducing or avoiding the formation of deposits when an engine is being operated at relatively low temperatures (e.g. in the time immediately following ignition of the engine). The exhaust fluid injector plate of the first aspect includes a plurality of exhaust gas directing vanes, each of which extend along a spiral trajectory towards the injection aperture. The spiral trajectory of each exhaust gas directing vane directs the vortex exhaust gas flow toward the injection aperture. Accordingly, the vortex exhaust gas flow can be accelerated across the flow surface of the exhaust fluid injector plate towards the injection aperture. As such, the plurality of exhaust gas directing vanes increase the velocity and change the pressure of the exhaust gas flow local to the injection aperture. The change in the pressure of the exhaust gas flow local to the injection aperture may be an increase or a decrease in the pressure of the exhaust gas flow local to the injection aperture. The plurality of exhaust gas directing vanes may also reduce recirculation of the exhaust gas. This in turn reduces or prevents the accumulation of exhaust fluid proximal to the injection aperture, and any exhaust fluid which is (temporarily) present may be carried away from the injection aperture by the increased velocity exhaust gas flow. Consequently, the formation of depositions around the exhaust fluid injector may be reduced or prevented. This means the exhaust fluid injector is less likely to become blocked by deposits, which may improve the lifetime of the exhaust fluid injector, may reduce the frequency of cleaning the exhaust fluid injector, and / or may reduce the need to replace the exhaust fluid injector. Further, it will be appreciated that increased velocity of vortex exhaust gas flow around the injection aperture provided by the first aspect is not dependent on the temperature of the exhaust fluid injector plate. Thus, the first aspect may allow a larger quantity of exhaust fluid to be injected into the exhaust gas when the engine is operated at relatively low temperatures (e.g. in the time immediately following ignition of the engine) without forming excessive amounts of deposits. Consequently, the need for application of external thermal energy is reduced. Such an exhaust fluid injector plate can thereby improve the overall emissions performance of an exhaust fluid mixing system. Brief description of the drawings Embodiments of the disclosure will be set out with reference to the following non-limiting figures in which: Figure 1 shows an embodiment of an exhaust fluid injection system comprising an exhaust fluid injector plate; Figure 2 shows a perspective view of an embodiment of an exhaust fluid injection assembly; Figure 3 shows a flow surface of the exhaust fluid injector plate; Figure 4 shows a flow diagram of the flow surface of the exhaust fluid injector plate of Figure 3; Figure 5 shows a cross-sectional view of the flow diagram of Figure 4; Figure 6 shows a perspective view of the exhaust fluid injection assembly integrated with an exhaust fluid vortex mixing conduit; Figure 7 shows a view of the flow surface of the exhaust fluid injector plate integrated with the exhaust fluid vortex mixing conduit; Figure 8 shows an exhaust fluid vortex mixing conduit comprising a primary spiral mixing blade connected with an inflow conduit; Figure 9 shows an embodiment of the exhaust fluid injector plate comprising a plurality of vortex mixing blades; Figure 10 shows a view of the exhaust fluid injector plate of Figure 9, without the plurality of vortex mixing blades; Figure 11 shows the vortex mixing blades of Figure 9; Figure 12 shows a view of a flow surface of the exhaust fluid injector plate with a plurality of vortex mixing blades integrated with the exhaust fluid vortex mixing conduit; Figure 13 shows a first view of an exhaust fluid injector plate comprising six exhaust gas directing vanes and three vortex mixing blades; and Figure 14 shows a second view of the exhaust fluid injector plate of Figure 13. Detailed description Figure 1 shows an embodiment of an exhaust fluid injection system 100. The exhaust fluid injection system 100 comprises an inlet 110 through which an exhaust gas may be received when the exhaust fluid injection system 100 is in use. Downstream of the inlet, the exhaust fluid injection system 100 comprises an exhaust fluid vortex mixing conduit 108. The exhaust fluid mixing conduit 108 may be for mixing the exhaust gas with exhaust fluid. The exhaust fluid injection system 100 comprises an exhaust fluid injection assembly 112. The exhaust fluid injection assembly 112 comprises an exhaust fluid injector 104 mounted to an exhaust fluid injector plate 102. The exhaust fluid injector 104 may inject exhaust fluid into the exhaust gas when the exhaust fluid injection system 100 is in use. Downstream of the exhaust fluid mixing conduit 108, the exhaust fluid injection system comprises a selective catalytic reduction system (SCR) 106. The SCR 106 may catalyse a chemical reaction between the exhaust fluid and the exhaust gas which may decrease the amount of Nitrogen Oxide in the exhaust gas. As such, the exhaust fluid injector 104 may inject an exhaust fluid, which is a reductant, wherein the reductant reacts with the nitrogen oxide in the exhaust gas at the SCR 106. The exhaust fluid injection system 100 may cause the exhaust gas to flow in a generally II-shaped flow path from the inlet 110 to the SCR 106. Geometries of the flow path other than the general U-shape shown in Figure 1 may also be used, for example the flow path pay be generally L shaped, or Z shaped. As such, the exhaust gas may be received in a first direction D1 through the inlet 110, be redirected by the exhaust fluid mixing conduit 108 into a second direction D2, the second direction D2 being transverse to the first direction D1. The exhaust gas may then be re-directed through the SCR 106 in a third direction D3 opposite to the first direction D1. The exhaust fluid injection assembly 112 may be provided such that the exhaust fluid injector 104 injects the exhaust fluid in an injection direction transverse to the first direction D1. Alternatively, or additionally, the injection direction may be aligned with the second direction D2. The exhaust fluid vortex mixing conduit 108 may be configured to create a vortex exhaust gas flow within the exhaust fluid vortex mixing conduit 108. For example, the exhaust fluid vortex mixing conduit 108 may comprise an outer wall 114 and a primary spiral mixing blade 116 defining an outer surface for the exhaust gas flow path through the exhaust fluid vortex mixing conduit which spirals inward about the second direction D2. As such, as the exhaust gas is redirected in the second direction D2, the exhaust gas may be flowing in a vortex having a central axis aligned with the second direction D2. The exhaust fluid injector 104 may be configured to inject exhaust fluid through the central axis of the vortex. The vortex exhaust gas flow may improve the mixing between the exhaust fluid and the exhaust gas. Figure 2 shows a perspective view of an embodiment of the exhaust fluid injection assembly 112. The exhaust fluid injector assembly 112 comprises the exhaust fluid injector plate 102 and the exhaust fluid injector 104. The exhaust fluid injector plate 102 defines an injection aperture (indicated by reference numeral 202, but not in view in Figure 2) through the exhaust fluid injector plate 102. The exhaust fluid injector 104 is configured to inject exhaust fluid through the injection aperture 202. For example, the exhaust fluid injector 104 may be configured to inject exhaust fluid such that the injection direction is aligned with the injection aperture 202. As shown in Figure 2, the exhaust fluid injector 104 may be configured to inject exhaust fluid in a cone extending in the injection direction aligned with the injection aperture 202 and expanding in a direction transverse with the injection direction. The exhaust fluid injector 102 plate comprises a plurality of exhaust gas directing vanes 204. The exhaust gas directing vanes 204 may interact with the exhaust gas as it rotates about the exhaust fluid vortex mixing conduit 108. For example, the exhaust gas directing vanes 204 may direct and / or accelerate the vortex of exhaust gas toward the injection aperture 202, thereby increasing the velocity and / or changing the pressure of the vortex of exhaust gas around the injection aperture 202. The change in the pressure of the vortex of exhaust gas around the injection aperture 202 may be an increase or a decrease in the pressure of the vortex of exhaust gas around the injection aperture 202. Additionally, directing and / or acceleration of the vortex of exhaust gas toward the injection aperture 204 may reduce recirculation of the exhaust gas. Each of the plurality of exhaust gas directing vanes 204 protrudes from a flow surface 206 of the exhaust fluid injector plate 102 and extends across the flow surface 206 of the exhaust fluid injector plate 102. Each of the plurality of the exhaust gas directing vanes 204 protrudes from the flow surface 206 by a vane height and extends across the flow surface 206 by a vane length. One or more of the vane heights may be variable along the respective vane length. For example, the vane height may be constant along a majority of the vane length (e.g. at least 50%, at least 60%, at least 70%, at least 80% or at least 90% of the vane length). In some embodiments, the vane height may reduce along a minority of the vane length (e.g. no greater than 50%, no greater than 40%, no greater than 30%, no greater than 20%, or no greater than 10% of the vane length). In some embodiments, the vane height may reduce along the vane length toward the injection aperture 202. In some embodiments, the vane height may reduce along the length in a linear manner. In some embodiments, for example as shown in Figure 6, the vane height may reduce in a nonlinear manner. As such, the vane height shown in Figure 6 may follow a (smooth) convex curve along a (minority) portion of the vane length. By providing a reduction in vane height toward the injection aperture 202, the exhaust gas directing vanes 204 may decrease flow disturbances as the exhaust gas transitions from flowing along the plurality of exhaust gas directing vanes 204 to flowing from the plurality of exhaust gas directing vanes 204 toward the injection aperture 202. By decreasing flow disturbances, the mixing of the exhaust gas with the exhaust fluid may be improved. Each of the plurality of exhaust gas directing vanes 204 may be rotationally symmetric about the injection aperture 202 with each of the other of the plurality of exhaust gas directing vanes 204.. In the embodiment shown in Figure 2, the plurality of exhaust gas directing vanes 204 comprises 3 vanes. By providing exhaust gas directing vanes 204 which are rotationally symmetric about the injection aperture 202, the plurality of exhaust gas directing vanes 204 may not disturb a uniformity of the vortex. Consequently, the plurality of exhaust gas directing vanes 204 may direct and / or accelerate the vortex of exhaust gas toward the injection aperture 202, without disturbing the uniformity of the vortex. The vortex of exhaust gas may be uniform in the sense that the vortex is rotationally invariant about the central axis of the vortex. As shown in Figures, 2, 3 and 9, the flow surface 206 of the exhaust gas fluid injector plate 102 may comprise an (outer) flat surface portion 208. The flow surface 206 may also comprise an (inner) concave surface portion 210. The inner concave surface portion 210 may surround the injection aperture 202, and the outer flat surface portion 210 may surround the inner concave surface portion 210. For example, each of the outer flat surface portion 208 and the inner concave surface portion 210 may define concentric annuli surfaces about the injection aperture 202. The outer flat surface portion 208 may smoothly transition to the inner concave surface portion 210 via an intermediate convex portion defining an annulus between the outer flat surface portion 208 and the inner concave surface portion 210. The smooth transition between the outer flat surface portion 210 and the inner concave surface portion 210 may reduce flow disturbances as the vortex of exhaust gas flows across the flow surface 206. The injection aperture 202 may be located at a centre of the flow surface 206. For example, the injection aperture 202 may be located at the centre of the concave surface portion 210 of the flow surface 206. In some embodiments, the injection aperture 202 may be concentric with a centre of the flow surface 206. By providing the flow surface with an inner concave surface portion 210, the vortex of exhaust gas may be permitted by the inner concave surface portion 210 to gain a component of velocity toward the injection aperture 202, in a direction opposite to the injection direction. Consequently, the inner concave surface portion 210 may accelerate the exhaust gas flow toward the injection aperture 202. In some embodiments, the injection aperture 202 may be offset from the centre of the flow surface 206. In some embodiments, the injection aperture may be offset from the centre of the concave surface portion 210 of the flow surface 206. The plurality of exhaust gas directing vanes 204 may extend across the outer flat surface portion 208, the inner concave surface portion 210, and / or both the outer flat surface portion 208 and the inner concave surface portion 210. As shown in Figure 2, each of the plurality of exhaust gas directing vanes 204 may extend across the inner concave surface portion 210. According to this disclosure, the vane height of one or more of the exhaust gas directing vanes 204 may be a height protruding normally (e.g. perpendicular) from the surface on which the exhaust gas directing vane 204 is provided. The exhaust fluid injector plate 102 may be mounted with the exhaust fluid injector 104. As shown in Figure 2, the exhaust fluid injector plate 102 may comprise a mounting surface 216 (indicated by reference numeral 216, but not in view in Figure 2) opposite the flow surface 206. The mounting surface 216 may comprise attachment means to secure the exhaust fluid injector 104 to the mounting surface 216. For example, one or more screw holes may be defined by the mounting surface 216 and configured to receive screws of the exhaust fluid injector 104. As shown in Figure 1, the exhaust fluid injector plate 102 may be integrated with the outer wall 114 of the exhaust fluid mixing conduit 108. In some embodiments, the exhaust fluid injector plate 102 may be form part of the outer wall 114. That is to say, in some embodiments the outer wall 114 of the exhaust fluid mixing conduit 108 may define an exhaust fluid injector plate 102 according to this disclosure. In other embodiments, the exhaust fluid injector plate 102 may be a separate part to the outer wall 114, wherein the exhaust fluid mixing conduit 108 is configured to integrate the exhaust fluid injector plate 102. For example, the outer wall 114 may define an injector plate receiving hole (not shown in Figure 1) configured to receive the exhaust fluid injector plate 102. The outer wall 114 may define an outer surface of the outer wall 114, an inner surface of the outer wall 114, and a plate engaging surface extending between the inner and outer surfaces around the injector plate receiving hole. In some embodiments, the exhaust fluid injector plate 102 may comprise a first portion. The first portion of the exhaust fluid injector plate provide a surface of the exhaust fluid injector plate 102 which defines the injection aperture 202. The exhaust fluid injector plate may also comprise a second portion. The second portion of the exhaust fluid injector plate may provide a surface on which the plurality of exhaust gas directing vanes 204 are provided. In some embodiments, the exhaust fluid injector plate 102 may comprise a third portion which provides a surface on which the plurality of vortex mixing blades 902 are provided. In some embodiments, the first portion, the second portion, and optionally the third portion may be formed as a single part. In some embodiments, one or more of the first portion, the second portion, and optionally the third portion may be separate parts which may be assembled to form the exhaust fluid injector plate. For example, one or more of the first portion, the second portion, and optionally the third portion may be provided by the outer wall 114 of the exhaust fluid mixing conduit 108. In some embodiments, the exhaust fluid injector plate 102 may define a first spacing between each the plurality of exhaust gas directing vanes 204 and the injection aperture 202. The spacing may be defined in the radial direction relative to a centre of the injection aperture on the surface of the exhaust fluid injector plate 102. In some embodiments, the first spacing may be defined by the shape / size of the second portion of the exhaust fluid injector plate 102. In some embodiments, the exhaust fluid injector plate 102 may define a second spacing between each the plurality of exhaust gas directing vanes 204 and each of the vortex mixing blades 902. The second spacing may be defined in the radial direction relative to a centre of the injection aperture on the surface of the exhaust fluid injector plate 102. In some embodiments, the second spacing may be defined by the shape / size of the third portion of the exhaust fluid injector plate 102. As such, in some embodiments, the exhaust fluid injector plate 102 may be provided such that the plurality of exhaust gas directing vanes 204 may be positioned in the proximity of the exhaust fluid injector 102 (specifically a tip of the exhaust fluid injector 102) in order to direct the flow of exhaust gas in the region proximal to the exhaust fluid injector 102. Referring again to Figure 2, the exhaust fluid injector plate 102 may define a wall engaging surface 212 extending from the flow surface 206 to the mounting surface 216. The wall engaging surface 212 may be configured to engage with the plate receiving surface of the outer wall 114. For example, the wall engaging surface may extend between the flow surface 206 and the mounting surface 216 by a distance equivalent to a thickness of the outer wall 114 between the inner surface of the outer wall 114 and the outer surface of the outer wall 114. The exhaust fluid injector plate 102 may comprise a flange 214 configured to engage with the outer surface of the outer wall 114. The flow surface 206 may be continuous with an inner surface of the outer wall 114 as the flange 214 engages with the outer surface of the outer wall 114 and as the wall engaging surface 212 engages with the plate engaging surface of the outer wall 114. The wall engaging surface 212 may be shaped to fit the plate engaging surface such that no exhaust gas and / or exhaust fluid can escape between the wall engaging surface 212 and the plate engaging surface. The flange 214 may extend over an interface of the wall engaging surface 212 and the plate engaging surface such that no exhaust gas and / or exhaust fluid can escape between the wall engaging surface 212 and the plate engaging surface. Figure 3 shows the flow surface 206 of the exhaust fluid injector plate 102. Each of the plurality of exhaust gas directing vanes 204 extends across the flow surface along a first spiral trajectory about the injection aperture 202. The first spiral trajectory may be one of: an Archimedean spiral, a hyperbolic spiral, a logarithmic spiral, a Fibonacci spiral, a lituus spiral, and a Theodorus spiral. For example, the first spiral trajectory may follow a trajectory defined by: r=f(0), where r is a position along the trajectory, defined in terms of a radial distance from the injection aperture 202, 0 is an angular coordinate about the injection aperture 202, and f is a first spiral function (e.g. an Archimedean spiral function, a hyperbolic spiral function, a logarithmic spiral function, a Fibonacci spiral function, a lituus spiral function or a Theodorus spiral function). The first spiral trajectory may extend between a first end of the first spiral trajectory having polar coordinates (r1, 01), corresponding with a respective first end of each of the plurality of exhaust gas directing vanes 204, and a second end of the first spiral trajectory having polar coordinates (r2, 02), corresponding with a respective second end of each of the plurality of exhaust gas directing vanes 204. The difference between angular coordinates of the polar coordinates (e.g. 01- 02) may be smaller than 180 degrees, smaller than 90 degrees or smaller than 45 degrees. In some embodiments, where the plurality of exhaust gas directing vanes 204 comprises N vanes, the difference between the angular coordinates (e.g. 01- 02) of the first and second ends of each of the plurality of exhaust gas directing vanes 204 is around (360 / N) degrees. A vane thickness of the or each of the plurality of exhaust gas directing vanes 204 may be constant along the respective vane length. The vane thickness may extend perpendicular to the first spiral trajectory and the vane height. In some embodiments, the vane thickness may be no greater than the vane length. For example the vane thickness may be: no greater than 10% of the vane length, no greater than 5% of the vane length, or no greater than 1% of the vane length. By making the vane thickness small compared to the vane length, each of the plurality of exhaust gas directing vanes 204 may direct and / or accelerate the exhaust gas toward the injection aperture 202 while minimising disturbance and / or turbulence of the exhaust gas flow. In some embodiments, for example as shown in Figure 3, the vane thickness may be constant along substantially the entirety of the vane length. In other embodiments, the vane thickness may be variable along the majority of the vane length. For example, the vane thickness may reduce toward the injection aperture 202. In some embodiments, one of both of the first and second ends an exhaust gas directing vane 204 may be rounded, or chamfered. For example, as shown in Figure 3, each of the first and second ends of each exhaust gas directing vane may be rounded or chamfered. By rounding / chamfering each of the first and second ends, flow disturbances at the first and second ends of the spiral trajectory may be decreased. The radius of each rounding / chamfering each end may be no greater than 5%, or no greater than 1% of the total vane length. In some embodiments (not shown in Figure 3), one or more of the exhaust gas directing vanes 204 may be rotationally asymmetric about the injection aperture 202. For example, plurality of exhaust gas directing vanes may comprise a first exhaust gas directing vane and a second exhaust gas directing vane. As such, there may be no angle by which the first exhaust gas directing vane 204 can be rotated about the injection aperture 202 onto the second exhaust gas directing vane 204. For example, a first vane height of the first gas directing vane 204 may be greater than a second vane height of the second exhaust gas directing vane 204. Alternatively, or additionally, a first vane length of the first exhaust gas directing vane 204 may be greater than a second vane length of the second exhaust gas directing vane 204. Alternatively, or additionally, the first spiral trajectory of the or each of the first and second exhaust gas directing vanes 204 may follow different first spiral functions f. By providing one or more exhaust gas directing vanes 204 which are rotationally asymmetric about the injection aperture 202, the directing by the plurality of exhaust gas directing vanes 204 of a rotationally asymmetric vortex of exhaust gas may be improved. Figure 4 shows a flow diagram of the flow surface of the exhaust fluid injector plate of Figure 3. Point X is to the side of one of the exhaust gas directing vanes 204. Point Y is downstream of point X, and is beyond the one of the exhaust gas directing vanes 204. The vortex of exhaust gas flows along one of the exhaust gas directing vanes 204, passing through point X, and then flows beyond the one of the exhaust gas directing vanes 204, passing through point Y. A velocity toward the injection aperture 202 at point Y (indicated by arrows around point Y) is greater than the velocity toward the injection aperture 202 at point X (indicated by arrows around point X). As such, it will be appreciated that the vortex of exhaust gas flow has been accelerated toward the injection aperture 202 by the exhaust gas directing vane 204. Figure 5 shows a cross-sectional view of the flow diagram of Figure 5. The cross-sectional view in Figure 5 is taken into the page through the dashed line B of Figure 4. Point Q is to the side of one of the exhaust gas directing vanes 204. The distance from Q to the flow surface 206 is less than the height of the exhaust gas directing vanes 204. Point R is not to the side of one of the exhaust gas directing vanes 204. As such, the distance from R to the flow surface 206 is greater than the height of the exhaust gas directing vanes 204. The velocity toward the injection aperture 202 at point Q (indicated by arrows around point Q) is greater than the velocity toward the injection aperture 202 at point R (indicated by arrows around point R). As such, the velocity of the vortex of exhaust gas flow toward the injection aperture 202 is increased to the sides of the exhaust gas directing vanes 204 compared with regions not to the sides of the exhaust gas directing vanes 204. Figure 6 shows a perspective view of the exhaust fluid injector plate 102 integrated with the exhaust fluid vortex mixing conduit 108. The exhaust fluid vortex mixing conduit 108 comprises the outer wall 114 defining an inlet 110 configured to receive the exhaust gas in the first direction, and an outlet 610 configured to output the exhaust gas in the second direction D2. The primary spiral mixing blade 116 is provided within the exhaust fluid vortex mixing conduit 108 extending from the outer wall 114 proximate the outlet 610. The outer wall 114 and the primary spiral mixing blade 116 define an outer surface for the exhaust gas flow path through the exhaust fluid vortex mixing conduit 110 which spirals inward about the second direction D2 in order to create a vortex exhaust gas flow within the exhaust fluid vortex mixing conduit 108. The injection aperture 202 may be configured to accommodate an injection of exhaust fluid into the exhaust fluid vortex mixing conduit 108. For example, as shown in Figure 6, the exhaust fluid injector plate 102 is integrated with the outer wall 114 such that the injection aperture 202 of the exhaust fluid injector plate 102 allows exhaust fluid to be injected into a centre of the vortex exhaust gas flow in the second direction D2. In use, the vortex exhaust gas flow may be flowing in a vortex having a central axis aligned with the second direction D2 and the injection aperture 202. The exhaust fluid injector 104 may be configured to inject exhaust fluid through the central axis of the vortex. In some embodiments, the exhaust fluid injector 104 may be configured to inject exhaust fluid at a first angle with respect to the central axis of the vortex exhaust gas flow. For example, the first angle may be no greater than 1 degrees, 5 degrees, 10 degrees, 20 degrees, 30 degrees, or 45 degrees. Downstream of the outlet 610, the exhaust fluid injection system 100 may comprise an outflow conduit 620 defining a channel aligned with the second direction D2. A diameter of the channel may be equivalent to a diameter of the outlet 610. The outer wall 114 may reduce in a diameter toward the outlet 610 such that the exhaust gas is directed from the exhaust fluid vortex mixing conduit 108, through the outlet 610, and then through the outflow conduit 620. Figure 7 shows a view of the flow surface 206 of the exhaust fluid injector plate 102 integrated with the exhaust fluid vortex mixing conduit 108. As shown in Figure 7, the outer wall 114 and the primary spiral mixing blade 116 define the exhaust gas flow path 702 through the exhaust fluid vortex mixing conduit 108. The exhaust gas flow path 702 spirals inward from the inlet 110 to the outlet 610 (the outlet 610 is best seen in Figure 6). As will be appreciated from Figure 7, in some embodiments a curvature of the primary spiral mixing blade 116 may be different to a curvature of the first spiral trajectories of the plurality of exhaust gas directing vanes 204. In some embodiments, the curvature of the primary spiral mixing blade 116 may complement the curvature of the first spiral trajectories of the plurality of exhaust gas directing vanes. For example, the primary spiral mixing blade may follow a primary spiral mixing blade spiral function which is the same as the first spiral function f. The primary spiral mixing blade 116, the outer wall 114, and / or the exhaust gas flow path 702 may be one of: an Archimedean spiral, a hyperbolic spiral, a logarithmic spiral, a Fibonacci spiral, a lituus spiral, and a Theodorus spiral. The outer wall 114 may comprise an assembly plate 640, and an enclosing portion 630, configured to enclose a first surface of the assembly plate 640. A second surface, opposite the first surface, may be flat such that the fluid vortex mixing conduit 108 can be interfaced with and / or connected with the exhaust fluid injection system 100. The first surface of the assembly plate 640 enclosed by the enclosing portion may define the inlet 110. The assembly plate 640 may be configured to connect the inlet 110 with an inflow conduit 802 (best seen in Figure 8) upstream of the inlet 110. The enclosing portion may extend in a spiral from the outlet 110 to a recess of the first surface of the assembly plate 630, the recess continuing the spiral to the primary spiral mixing blade, which extends from the first surface of the assembly plate 640. The enclosing portion 630 may define the injector plate receiving hole and the outlet 610. Figure 8 shows an exhaust fluid vortex mixing conduit 108 comprising the primary spiral mixing blade 116 connected with the inflow conduit 802. The exhaust fluid injection system 100 may comprise the inflow conduit 802 upstream of the inlet 110. The inflow conduit 802 may define a channel aligned with the first direction D1. A diameter of the channel may be equivalent to a diameter of the inlet 110. The channel may be a cylindrical channel, or any other prism shaped channel. Figure 9 shows an embodiment of the exhaust fluid injector plate 102 integrated with a plurality of vortex mixing blades 902. The plurality of vortex mixing blades 902 may be configured to modulate the vortex created by the outer wall 114 and the primary spiral mixing blade 116. As shown in Figure 9, the exhaust fluid injector plate 102 further comprises a plurality of vortex mixing blades 902. Each vortex mixing blade 902 protrudes from the flow surface 206 by a blade height greater than the vane height of the exhaust gas directing vanes. The exhaust gas directing vanes 204 are obscured in Figure 9 by the vortex mixing blades 902). In some embodiments (not shown in Figure 9), the exhaust fluid injector plate 102 may further comprise a plurality of blade locators, wherein each of the plurality of blade locators is configured to locate a respective vortex mixing blade 902 on the flow surface 206. The mounting surface 216 may comprise an outer flat surface portion 908 and an inner convex surface portion 906. The inner convex surface portion 906 may be opposite the inner concave surface portion 210 of the flow surface 206. The injection aperture 202 may be located at the centre of the inner convex surface portion 906 of the mounting surface 216. The inner convex surface portion 906 of the mounting surface 216 may be configured to receive the exhaust fluid injector 104. As described above, each of the plurality of exhaust gas directing vanes 204 may extend across the flow surface 206 along the first spiral trajectory about the injection aperture 202. In some embodiments, each of the plurality of vortex mixing blades 902 extends across the flow surface 206 along a second spiral trajectory about the injection aperture 202. The second spiral trajectory may follow a trajectory defined by: r=g(0), where r is a position along the trajectory, defined in terms of a radial distance from the injection aperture 202, 0 is an angular coordinate about the injection aperture 202, and g is a second spiral function (e.g. an Archimedean spiral function, a hyperbolic spiral function, a logarithmic spiral function, a Fibonacci spiral function, a lituus spiral function or a Theodorus spiral function). The second spiral trajectory may extend between a first end of the second spiral trajectory having polar coordinates (r3, 03), corresponding with a respective first end of each of the plurality of vortex mixing blades 902, and a second end of the second spiral trajectory having polar coordinates (r4, 04), corresponding with a respective second end of each of the plurality of vortex mixing blades 902. The plurality of vortex mixing blades 902 may be arranged about the injection aperture 202 outside the plurality of exhaust gas directing vanes 204. For example, r1 and r2 may each be less than r3 or r4. Alternatively, at least one of r1 or r2 may be less than at least one of r3 or r4. In some embodiments, the first spiral trajectory may be similar to the second spiral trajectory. For example, the first spiral function f may be the same as the second spiral function g. By providing the first spiral function the same as the second spiral function, the acceleration of the vortex of exhaust gas toward the injection aperture 202 by the exhaust gas directing vanes 204 may be improved because the first spiral trajectory complements the second spiral trajectory. In some embodiments, the first spiral trajectory may be different to the second spiral trajectory. For example, the first spiral function f may be different to the second spiral function g. The first spiral function f may have a steeper gradient toward the injection aperture 202 than the second spiral function g such that the flow is accelerated as the vortex of exhaust gas flows from the plurality vortex mixing blades 902 to the plurality of exhaust gas directing vanes 204. In some embodiments, each of the plurality of vortex mixing blades 902 may be rotationally symmetric about the injection aperture 202. For example, where the plurality of vortex mixing blades 902 comprises N blades, a rotation of an nth vortex mixing blade 902 by (360 / N) degrees about the injection aperture 202 may rotate the nth vortex mixing blade 902 onto an (n+1)th vortex mixing blade 902. In the embodiment shown in Figure 9, the plurality of vortex mixing blades 902 comprises 3 blades. As such, the plurality of vortex mixing blades 902 may create a symmetric vortex of exhaust gas about the injection aperture 202. By providing the plurality of exhaust gas directing vanes 204, and the plurality of vortex mixing blades 902 rotationally symmetric about the injection aperture, the directing, by the plurality of exhaust gas directing vanes 204, of the symmetric vortex created by the plurality of vortex mixing blades 902 can be improved. For example, the vortex of exhaust gas may be accelerated more quickly and / or uniformly toward the aperture 202. Figure 10 shows a view of the exhaust fluid injector plate 102 of Figure 9, without the plurality of vortex mixing blades. In some embodiments (not shown in Figure 10) the plurality of blade locators may extend across the flow surface 204. For example, each of the plurality of blade locators may extend across the outer flat surface portion 208. The plurality of blade locators may protrude from the flow surface 206. Each of the plurality of blade locators may extend partially along the second spiral trajectory of a respective one of the plurality of vortex mixing blades 902 between the first end of the second spiral trajectory and the second end of the second spiral trajectory. In some embodiments (as shown in Figure 10) each of the plurality of exhaust gas vanes 204 may protrude from the inner concave surface portion 210. In some embodiments, one or more of the plurality of exhaust gas directing vanes 204 may protrude, at least in part, from the flat surface portion 208. In some embodiments (not shown in Figure 10), each of the plurality of blade locators may protrude from the outer flat surface portion 208. As such, each of the plurality of vortex mixing blades 902 may protrude from the outer flat surface portion 208. In some embodiments, one or more of the plurality of vortex mixing blades 902 may protrude, at least in part, from the inner concave surface portion 210. Figure 11 shows the vortex mixing blades 902 of Figure 9. As shown in Figure 11, the blade height of one or more of the vortex mixing blades 902 may be variable. For example, each of the plurality of the vortex mixing blades 902 in Figure 9 protrudes from the flow surface 206 by the blade height and extends across the flow surface 206 by a blade length. One or more of the blade heights may be variable along the respective blade length. For example, the blade height may be constant along a majority of the blade length (e.g. more than 50%, more than 60%, more than 70%, more than 80% or more than 90% of the vane length) and then reduce along a remainder of the blade length. The blade height may reduce along the blade length toward the injection aperture 202. The reduction in blade height toward the injection aperture 202 may prevent the plurality of vortex mixing blades 902 from blocking the cone of injected exhaust fluid. Figure 12 shows a view of the flow surface 206 of the exhaust fluid injector plate 102 with a plurality of vortex mixing blades 902 integrated with the exhaust fluid vortex mixing conduit 108. The flow surface 206, the plurality of exhaust gas directing vanes 204, and the plurality of vortex mixing blades 902, are configured to define a vortex exhaust gas flow path 1202. The vortex exhaust gas flow path 1202 may be downstream from the exhaust gas flow path 702. As such, the vortex exhaust gas flow path 1202 may cause the vortex created by the outer wall 114 and the primary spiral mixing blade 116 to be further rotated by the plurality of vortex mixing blades 902, and then to be accelerated and / or directed toward and / or rotated around the injection aperture 202 by the plurality of exhaust gas directing vanes 202. A central axis of the vortex exhaust gas flow path 1202 extends in a direction transverse to the flow surface 206. In some embodiments, the plurality of exhaust gas directing vanes 204 may comprise two vanes, three vanes, four vanes, five vanes, six vanes or more vanes. In some embodiments, the plurality of vortex mixing blades 902 may comprise two blades, three blades, four blades, five blades, six blades or more blades. The number of exhaust gas directing vanes 204 may be the same as the number of vortex mixing blades 902. The number of exhaust gas directing vanes 204 may be different to the number of vortex mixing blades 902. For example, Figure 13 shows a first view of an exhaust fluid injector plate 102 comprising six exhaust gas directing vanes 204 and three vortex mixing blades 902. Figure 14 shows a second view of the exhaust fluid injector plate 102 of Figure 13. By providing more exhaust gas directing vanes 204 than vortex mixing blades 902, the vortex of exhaust gas created by the plurality of vortex mixing blades 902 may be accelerated by the exhaust gas directing vanes 204. In some embodiments (not shown in Figure 13), each of the plurality of exhaust gas directing vanes 204 may have a maximum vane height at a first point 1303 along the vane length. Towards the first end of the respective exhaust gas directing vane 204 from the first point, the vane height may reduce from the maximum vane height to the flow surface 206 (e.g. the vane height may be zero at the first end). Towards the second end of the respective exhaust gas directing vane 204 from the first point, the vane height may reduce from the maximum vane height to the flow surface 206 (e.g. the vane height may be zero at the second end). The vane height may reduce linearly, in a convex curve, or in a concave curve. The vane height may reduce in a convex curve towards the first end of the respective exhaust gas directing vane 204 from the first point. The vane height may reduce linearly toward the second end of the respective exhaust gas directing vane 204 from the first point. Each exhaust gas directing vane 204 may have the first end closer to the injection aperture than the second end, and the first point closer to the second end than the first end. In some embodiments (not shown in Figure 13), each of the plurality of vortex mixing blades 902 may have a maximum blade height at a second point along the blade length. Each of the plurality of vortex mixing blades 902 may have a reduced blade height at the first end of the respective vortex mixing blade 902. The vane height may reduce from the maximum vane height at the first point to the reduced vane height at the first end of the respective vortex mixing blade 902. Towards the second end of the respective vortex mixing blade 902 from the second point, the vane height may reduce from the maximum vane height to the flow surface 206 (e.g. the vane height may be zero at the second end). The vane height may reduce linearly, in a convex curve, or in a concave curve. The vane height may reduce in a convex curve towards the first end of the respective vortex mixing blade 902 from the second point. The vane height may reduce in a convex curve toward the second end of the respective vortex mixing blade 902 from the second point. Each vortex mixing blade 902 may have the first end may be closer to the injection aperture 202 than the second end, and the second point may be closer to the first end than the second end. In some embodiments (as shown in Figure 14), the mounting surface 216 may comprise a flat outer portion 1402 and a raised inner portion 1404. The injection aperture 202 may be located at a centre of the raised inner portion 1404. The raised inner portion 1404 may be configured to interface with the exhaust fluid injector 104. The raised inner portion 1404 may be opposite a portion of the flow surface from which the plurality of exhaust gas directing vanes 204 and / or the plurality of vortex mixing blades 902 extend. As such, the mechanical stability of the plurality of exhaust gas directing vanes 204 and / or the plurality of vortex mixing blades 902 may be improved by the raised inner portion 1404. In some embodiments, the exhaust fluid injector 104 may be mounted to the exhaust fluid injector plate 102. The exhaust fluid injector 104 may comprise an injection nozzle configured to inject exhaust fluid through the injection aperture 202. In some embodiments, the exhaust fluid may be injected as a liquid. In some embodiments, the exhaust fluid may be injected as a gas. Industrial applicability According to embodiments of this disclosure, an exhaust fluid injector plate 102 is provided. The exhaust fluid injector plate 102 may be provided as part of an exhaust fluid injection assembly 112 and / or as part of an exhaust fluid vortex mixing conduit 108. The exhaust fluid injector plate 102, the exhaust fluid injection assembly 112, or the exhaust fluid vortex mixing conduit may be provided as part an exhaust fluid injection system 100 for mixing an exhaust gas with exhaust fluid. In some embodiments, the exhaust fluid injection system may be provided as part of an internal combustion engine. The exhaust gas fluid injection system 100 may be used with any type of internal combustion engine. In particular, the internal combustion engine may be a diesel engine. As such, the exhaust fluid injection system 100 may be a diesel exhaust fluid (DEF) injection system. Such a DEF injection system may be configured to inject DEF (e.g. a fluid comprising urea water) into a DEF mixing conduit. The DEF may comprise a reductant or otherwise decompose into a reductant in the exhaust system 100 in such that a reduction reaction occurs at the SCR 106. Of course, in other embodiments, the exhaust fluid injection system 100 may be configured to work with other, alternative fuels such as hydrogen and the like. As discussed above, the exhaust fluid vortex mixing conduit 108 defines an exhaust gas flow path 702 which spirals from the inlet 110 to the outlet 610, wherein the spiral exhaust gas flow path spirals about the outlet 610 (in the second direction D2). Due to the rotation, a vortex of exhaust gas is created at the outlet, and about the injection aperture 202 of the exhaust fluid injector plate 102, rotating about the second direction D2. This vortex flow may be modulated by the plurality of vortex mixing blades 902. This vortex flow may create low pressure, low velocity regions of the vortex (e.g. at the centre of the vortex, into which the exhaust fluid may be injected). As such, the rate of formation of exhaust fluid deposits around the low-pressure, low velocity, flow recirculation regions may be increased. For example, deposits can accumulate on or around the injection aperture, which may cause blockages and stoppages of the exhaust fluid injector. Additionally, as deposits form more easily at lower temperatures, it may be challenging to inject sufficient exhaust fluid whilst reducing or avoiding the formation of deposits when an engine is being operated at relatively low temperatures (e.g. in the time immediately following ignition of the engine). The exhaust fluid injector plate 102 includes a plurality of exhaust gas directing vanes 204, each of which extend along a spiral trajectory towards the injection aperture 202. The spiral trajectory of each exhaust gas directing vane 204 directs the vortex exhaust gas flow toward the injection aperture 202. Accordingly, the vortex exhaust gas flow can be accelerated across the flow surface 206 of the exhaust fluid injector plate 102 towards the injection aperture 102. As such, the plurality of exhaust gas directing vanes 204 increase the velocity and change the pressure of the exhaust gas flow local to the injection aperture 202. This in turn reduces or prevents the accumulation of exhaust fluid proximal to the injection aperture 202, and any exhaust fluid which is (temporarily) present may be carried away from the injection aperture 202 by the increased velocity exhaust gas flow. Consequently, the formation of depositions around the exhaust fluid injector 206 may be reduced or prevented. This means the exhaust fluid injector 206 is less likely to become blocked by deposits, which increases the lifetime of the exhaust fluid injector 206, reduces the frequency of cleaning the exhaust fluid injector 206, and / or reduces the need to replace the exhaust fluid injector 206. Further, it will be appreciated that increased velocity of vortex exhaust gas flow around the injection aperture 202 is not dependent on the temperature of the exhaust fluid injector plate 102. Thus, the first aspect may allow a larger quantity of exhaust fluid to be injected into the exhaust gas when the engine is operated at relatively low temperatures (e.g. in the time immediately following ignition of the engine) without forming excessive amounts of deposits. Consequently, the need for application of external thermal energy is reduced. Such an exhaust fluid injector plate 102 can thereby improve the overall emissions performance of exhaust fluid injection system 100.

Claims

1. An exhaust fluid injector plate for an exhaust fluid vortex mixing conduit, the exhaust fluid injector plate defining:an injection aperture through the exhaust fluid injector plate; andthe exhaust fluid injector plate comprising:a plurality of exhaust gas directing vanes, each exhaust gas directing vane protruding from a flow surface of the exhaust fluid injector plate and extending across the flow surface along a spiral trajectory about the injection aperture.

2. The exhaust fluid injector plate of claim 1, further comprising:a plurality of vortex mixing blades each protruding from the flow surface by a blade height greater than a vane height of the exhaust gas directing vanes,wherein the plurality of vortex mixing blades are arranged about the injection aperture outside of the plurality of exhaust gas directing vanes.

3. The exhaust fluid injector plate of claim 2, whereineach of the plurality of exhaust gas directing vanes extends across the flow surface along a first spiral trajectory about the injection aperture; andeach of the plurality of vortex mixing blades extends across the flow surface along a second spiral trajectory about the injection aperture.

4. The exhaust fluid injector plate of claim 3, whereinthe first spiral trajectory is different to the second spiral trajectory.

5. The exhaust fluid injector plate of any of claims 2 to 4, wherein:the flow surface, the plurality of exhaust gas directing vanes, and the plurality of vortex mixing blades, are configured to define a vortex exhaust gas flow path of the exhaust fluid vortex mixing conduit, wherein a central axis of the vortex exhaust gas flow path extends in a direction transverse to the flow surface.

6. The exhaust fluid injector plate of any of claims 1 to 5, wherein:the injection aperture is configured to accommodate an injection of exhaust fluid into the exhaust fluid vortex mixing conduit.

7. The exhaust fluid injector plate of any preceding claim, wherein:the spiral trajectory is one of: an Archimedean spiral, a hyperbolic spiral, a logarithmic spiral, a Fibonacci spiral, a lituus spiral, and a Theodorus spiral.

8. The exhaust fluid injector plate of any preceding claim wherein:the vane height of at least one of the exhaust gas directing vanes is variable along its length.

9. The exhaust fluid injector plate of claim 8, whereinthe vane height reduces along the length of the at least one exhaust gas directing vane towards the injection aperture.

10. The exhaust fluid injector plate of any preceding claim, wherein:each of the plurality of exhaust gas directing vanes is rotationally symmetric about the injection aperture with each other of the plurality of exhaust gas directing vanes.

11. The exhaust fluid injector plate of any of claims 1 to 9, wherein:a vane height of a first exhaust gas directing vane of the plurality of exhaust gas directing vanes is greater than a vane height of a second exhaust gas directing vane of the plurality of exhaust gas directing vanes.

12. The exhaust fluid injector plate of any of claims 1 to 9 or 11, wherein:a length of the spiral trajectory of a first vane of the plurality of exhaust gas directing vanes is greater than a length of the spiral trajectory of a second vane of the plurality of exhaust gas directing vanes.

13. The exhaust fluid injector plate of any preceding claim, wherein:the flow surface comprises an outer flat surface portion and an inner concave surface portion.

14. The exhaust fluid injector plate of claim 13, wherein:the injection aperture is located at a centre of the concave surface portion of the flow surface.

15. The exhaust fluid injector plate of claim 13 or claim 14, whereinthe vortex mixing blades each protrude from the outer flat surface portion of the flow surface.

16. The exhaust fluid injector plate of any of claims 13 to 15, whereinthe plurality of exhaust gas directing vanes each protrude, at least in part, from the concave surface portion of the flow surface.

17. The exhaust fluid injector plate of any preceding claim, wherein:the injection aperture is concentric with a centre of the flow surface.

18. An exhaust fluid injection assembly comprising:an exhaust fluid injector plate according to any of claims 1 to 17; andan exhaust fluid injector mounted to the exhaust fluid injector plate, the exhaust fluid injector comprising an injection nozzle configured to inject exhaust fluid through the injection aperture in an injection direction aligned with the injection aperture.

19. The exhaust fluid injection assembly of claim 18, wherein:the exhaust fluid injector is configured to inject exhaust fluid in a cone extending in the injection direction aligned with the injection aperture and expanding in a direction transverse with the injection direction.

20. An exhaust fluid vortex mixing conduit for mixing an exhaust gas with exhaust fluid, the exhaust fluid vortex mixing conduit comprising:an outer wall defining:an inlet configured to receive the exhaust gas in a first direction;an outlet configured to output the exhaust gas in a second direction;a primary spiral mixing blade provided within the exhaust fluid vortex mixing conduit extending from the outer wall proximate the inlet,wherein the outer wall and the primary spiral mixing blade define an outer surface for the exhaust gas flow path through the exhaust fluid vortex mixing conduit which spirals inward from the inlet to the outlet about the second direction in order to create a vortex exhaust gas flow within the exhaust fluid vortex mixing conduit; andan exhaust fluid injector plate according to any of claims 1 to 17, or the exhaust fluid injector assembly of claims 18 or 9;wherein the exhaust fluid injector plate is integrated with the outer wall such that the injection aperture of the exhaust fluid injector plate allows exhaust fluid to be injected into a centre of the vortex exhaust gas flow in the second direction.

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