DE102021121133A1 - MIXING DEVICE FOR LIQUIDS AND MIXING ASSEMBLY FOR AN EXHAUST SYSTEM - Google Patents

Abstract

A mixing device (300) for mixing an injected fluid with exhaust gas discharged from an internal combustion engine (12), the mixing device comprising: one or more inlet ports (302) configured to inject a first portion (P1) of the exhaust gas take up; a bypass passage (304) configured to receive a second portion (P2) of the exhaust gas; a mixing chamber (306) configured to allow the injected fluid to mix with the first portion of the exhaust to form a mixed exhaust; and one or more exhaust ports (308) configured to communicate the mixed exhaust gas with the second portion of the exhaust gas.

Description

TECHNICAL AREA

The present disclosure relates to a fluid mixing device for an exhaust system and a corresponding mixing arrangement. In particular, but not exclusively, the exhaust system is an exhaust system for an internal combustion engine of a vehicle.

BACKGROUND

Internal combustion engines (“Engines”) produce exhaust emissions. To reduce certain emissions, exhaust from the engine flows through a series of exhaust aftertreatment devices that form an exhaust aftertreatment system.

For example, the exhaust from diesel engines and direct-injection gasoline engines can contain high levels of nitrogen oxides. In order to reduce nitrogen oxide emissions, vehicle exhaust systems are increasingly being equipped with after-treatment systems for selective catalytic reduction (SCR). Such systems can reduce nitrogen oxides by 70-95%.

SCR systems consist of a catalyst chamber, which is generally a substrate with a multitude of small channels surrounded by catalyst walls through which the exhaust gases flow. The supply of a reducing agent such as ammonia or urea is required for the nitrogen oxide reduction reaction. The reducing agent is generally stored in a special tank and injected into the exhaust before the SCR system.

The liquid injector for the injection of the reducing agent must be positioned as far upstream as possible from the reaction site to ensure sufficient mixing length to produce a homogeneous mixture. In some applications a distance of one meter is considered sufficient. If the mixing length is insufficient, the nitric oxide reduction reaction is limited to only a small part of the substrate cross-section.

SUMMARY OF THE INVENTION

According to one aspect of the invention, there is provided a mixing device for mixing an injected fluid with exhaust gas from an internal combustion engine, the mixing device comprising:
one or more intake ports configured to receive a first portion of the exhaust gas;
a bypass passage configured to receive a second portion of the exhaust gas;
a mixing chamber configured to allow the injected fluid to mix with the first portion of the exhaust to form a mixed exhaust; and one or more exhaust ports configured to communicate the mixed exhaust gas with the second portion of the exhaust gas.

One benefit is that the mixing length required to achieve a substantially homogeneous fluid-gas mixture is significantly reduced. This enables, for example, the provision of an additional substrate (e.g. SCR substrate) close to the engine that works effectively.

In some examples, the one or more outlet openings is a plurality of outlet openings.

In some examples, the mixing device is shaped to cause axial circulation about a longitudinal axis such that the first portion of the exhaust gas and the injected fluid circulate axially in the mixing chamber before exiting through the one or more outlet ports.

In some examples, the mixing chamber is substantially coaxial with the bypass duct and the longitudinal axis is substantially in the direction of the bypass duct.

In some examples, the one or more intake ports include louvers configured to impart axial circulation to the first portion of the exhaust gas.

In some examples, the mixing chamber is generally toroidal in shape and the bypass passage is a central hole defined through the generally toroidal mixing chamber.

In some examples, the substantially toroidal mixing chamber is shaped and sized to fit within an exhaust system housing in an orientation where an equatorial plane of the substantially toroidal mixing chamber is substantially perpendicular to the oncoming exhaust gas.

In some examples, the depth of the substantially toroidal mixing chamber is less than the average outside diameter of the substantially toroidal mixing chamber.

In some examples, the one or more exhaust ports are a plurality of exhaust ports spaced in a toroidal manner arranged in a row around the substantially toroidal mixing chamber, and/or wherein the one or more inlet ports are a plurality of inlet ports arranged in a toroidally spaced row around the substantially toroidal mixing chamber.

In some examples, the one or more inlet ports are oriented to face in a different poloidal direction than the one or more outlet ports.

In some examples, the one or more inlet ports are poloidally aligned to face a first direction, wherein the one or more outlet ports are poloidally aligned to face a second direction, and wherein the first direction and the second direction on opposite sides of an equatorial plane of the substantially toroidal mixing chamber.

In some examples, the one or more exhaust ports are poloidally aligned to face the bypass passage.

In some examples, the one or more outlet openings have smaller cross-sectional areas than the one or more inlet openings.

In some examples, the one or more outlet openings are arranged in the vicinity of the bypass channel such that a vaporized phase of the fluid can pass through the one or more outlet openings while droplets of the fluid are distributed in a part of the mixing chamber that is remote from the bypass channel is where the droplets are retained for evaporation.

In some examples, the mixing chamber includes an injector inlet for receiving fluid injector spray.

In some examples, the injector inlet is oriented to inject flow-wise in a configured direction of exhaust gas circulation within the mixing chamber.

In some examples, the one or more outlet ports are a plurality of outlet ports, wherein a distance between a first pair of the outlet ports is increased relative to an average distance between the outlet ports overall, and the injector inlet is limited to the increased space between the first pair of outlet ports is aligned.

According to one aspect of the invention, a mixer assembly is provided that includes the mixing device and a flow-directing plate that is configured to be positioned downstream of the bypass duct, wherein the flow-directing plate includes a flow deflector, and wherein the bypass duct and the one or more outlet ports Flow deflector facing.

In some examples, the flow directing plate includes a plurality of openings in a periphery of the flow deflector.

In some examples, the openings include louvered openings configured to direct the flow into a space obscured by the flow deflector.

In some examples, the mixer assembly has a substrate housing arranged to receive the mixing device and one or more substrates.

In some examples, the mixer assembly includes a secondary bypass channel formed between the substrate housing and an outer periphery of the mixing device, wherein the one or more outlet ports face away from the secondary bypass channel, and wherein the secondary bypass channel has a smaller cross-sectional area than the first bypass channel.

In some examples, the mixing device is configured to receive one or more sensors and to position the one or more sensors in a flow path connected to the secondary bypass passage.

According to one aspect of the invention, an exhaust system is provided that includes the mixer assembly.

According to one aspect of the invention, a vehicle is provided that includes the exhaust system.

• ein Gehäuse, das einen Abgasdurchgang mit einer Längsachse definiert, entlang der das Abgas durch das Gehäuse strömt; und
• eine Axialdrall-Mischvorrichtung, wobei die Axialdrall-Mischvorrichtung so konfiguriert ist, dass sie eine axiale Zirkulation um die Längsachse erzeugt, um zumindest einen Teil des Abgases mit einem Fluid zu mischen.

According to one aspect of the invention, there is provided a mixer arrangement for mixing an injected fluid with an exhaust gas output of an internal combustion engine, the mixer arrangement comprising:

• a housing defining an exhaust gas passage having a longitudinal axis along which exhaust gas flows through the housing; and
• an axial swirl mixing device, the axial swirl mixing device being configured to provide axial circulation around the longitudinal generated axis to mix at least a portion of the exhaust gas with a fluid.

It is expressly intended within the scope of this application that the various aspects, embodiments, examples and alternatives set forth in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, are independent of one another or in any combination falling within the scope of the appended claims. That is, any embodiment and/or feature of an embodiment may be combined in any manner and/or combination that falls within the scope of the appended claims, provided these features are not incompatible. Applicant reserves the right to amend any originally filed claim or to file a new claim accordingly, including the right to amend an originally filed claim to depend on another claim and/or to incorporate a feature of another claim, even if it was not originally claimed in this way.

character list

• 1 zeigt ein Beispiel für ein Fahrzeug;
• 2 zeigt ein Beispiel für eine Mischvorrichtung;
• 3 zeigt ein Beispiel für eine Mischvorrichtung, die die Richtung der Abgase zeigt;
• 4 zeigt eine Detailansicht einer beispielhaften Einlassöffnung für eine Mischvorrichtung;
• 5 zeigt ein Beispiel für eine Mischvorrichtung und eine strömungsleitende Platte;
• 6 zeigt ein Beispiel für eine Auslassseite einer Mischvorrichtung;
• 7 zeigt ein Beispiel für eine strömungsleitende Platte;
• 8 zeigt ein Beispiel für eine Mischvorrichtung;
• 9 zeigt eine Querschnittsansicht eines Schnitts einer beispielhaften Mischvorrichtung; und
• 10 zeigt ein Beispiel für die Gestaltung einer zweiten Einlassöffnung.

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

• 1 shows an example of a vehicle;
• 2 shows an example of a mixing device;
• 3 shows an example of a mixing device showing the direction of the exhaust gases;
• 4 shows a detailed view of an exemplary inlet opening for a mixing device;
• 5 Figure 12 shows an example of a mixing device and a flow directing plate;
• 6 shows an example of an outlet side of a mixing device;
• 7 shows an example of a flow-guiding plate;
• 8th shows an example of a mixing device;
• 9 Figure 12 shows a cross-sectional view of a section of an exemplary mixing device; and
• 10 shows an example of the design of a second inlet opening.

DETAILED DESCRIPTION

1 1 shows an example of a vehicle 10 in which embodiments of the invention may be implemented. In some, but not necessarily all, examples, the vehicle 10 is a passenger vehicle, also referred to as a car or an automobile. In other examples, embodiments of the invention may be used for other applications, such as industrial or commercial vehicles. The vehicle 10 includes an engine 12. The engine 12 is connected to an exhaust system 14 which leads to an exhaust pipe.

The exhaust system 14 includes one or more exhaust gas aftertreatment devices and one or more silencers, which are connected to one another directly or via exhaust pipes. The exhaust aftertreatment devices are housed in enclosures commonly referred to as duct systems. the 2 until 9 show a mixing unit 16 of the exhaust system 14 of the vehicle 10.

The mixer assembly 16 includes a housing 100. The housing 100 includes at least one exhaust aftertreatment device and a mixing device 300 as described herein. 2 12 is a top cross-sectional view through the center of a central portion 104 of housing 100.

The illustrated housing 100 includes an upstream inlet portion 102 configured to receive exhaust gas and having a relatively small cross-sectional area. The housing 100 includes a central portion 104 (passageway) through which the exhaust gas flows and which has a relatively large, relatively constant cross-sectional area. The housing 100 includes a downstream outlet portion 106 through which the exhaust gas exits and which has a relatively small cross-sectional area. The outlet section 106 and the inlet section 102 are at opposite ends of the middle section 104.

The geometry of the exhaust system 14 is described in terms of the following dimensions. 2 12 shows a central longitudinal axis L extending through the central portion 104 of the housing 100 toward the outlet portion 106. FIG. A set of local Cartesian coordinates is shown including an L-axis defining the longitudinal axis and an x-axis and a y-axis defining a plane orthogonal to the longitudinal axis. Alternatively, the x-axis and y-axis can be expressed as a radius from the longitudinal axis in cylindrical coordinates.

The inlet portion 102 of the housing 100 is configured to attach to an upstream component of the exhaust system 14, such as an outlet of a turbocharger (not shown). The outlet portion 106 of the housing 100 is configured to attach to a downstream component of the exhaust system 14, such as an exhaust pipe (also not shown).

In some, but not necessarily all, examples, the inlet portion 102 and/or the outlet portion 106 may be offset from the L-axis in the x and/or y direction in an asymmetric configuration. Likewise, the inlet section 102 and/or the outlet section 106 can point in different directions. As such, the flow flowing through the central portion 104 of the housing 100 may be unevenly distributed across the cross section of the central portion 104 . 1 12 shows that the outlet section 106 faces in a different direction than the inlet section 102. The offset of the inlet section 102 is shown in the plan view of FIG 1 not visible, but would be visible in a side view.

Housing 100 could be made of steel or other suitably heat resistant material.

In the present example, but not necessarily in all examples, the housing 100 is a substrate housing 100, the further components within the housing 100 comprising at least one substrate (exhaust gas aftertreatment device). 2 Figure 1 shows a pair of substrates 200, 500 within the housing 100. The substrates shown include a first, upstream substrate 200 and a second, downstream substrate 500, both located in the central portion 104 of the same housing 100 and having a longitudinal gap therebetween.

The upstream substrate 200 may be configured as a lean NOx trap and/or a fuel (eg, diesel) oxidation catalyst, as one non-limiting example.

The downstream substrate 500 can be configured as an SCR substrate and optionally also as a soot filter (non-limiting example). The downstream substrate 500 is referred to herein as an SCR substrate, although in other examples it could be used for a different form of exhaust aftertreatment. The SCR reaction requires injection of a reductant into the exhaust gas upstream of the SCR substrate 500. The reductant may be urea, ammonia, or other equivalents. In one implementation, the reductant is an aqueous urea solution, commonly marketed as diesel exhaust fluid.

Mixing device 300 mixes the reducing agent fluid with the exhaust gas, resulting in a nearly homogeneous mixture that enters SCR substrate 500 . the 2 , 3 , 5 , 6 , 8th and 9 show different views of the mixing device 300. The reducing agent liquid can be injected into the mixing device 300. FIG.

The mixing device 300 is located in the middle section 104 of the housing 100, upstream of the SCR substrate 500. In 2 the mixing device 300 is located in the short longitudinal gap between the upstream substrate 200 and the SCR substrate 500.

In 2 , but not necessarily in all examples, the other components within the housing 100 include a flow-directing plate 400, as in FIG 7 shown in detail, for use with the mixing device 300. Although the flow directing plate 400 will be described in detail later, its purpose can be summarized as helping to redirect the flow exiting the mixing device 300 in a manner that improves the distribution of the gas-fluid mixture entering the SCR substrate 500 is further improved. The flow directing plate 400 is located immediately downstream of the mixing device 300.

As will be explained below, the mixing device 300 and the flow-guiding plate 400 can mix the injected reducing agent fluid with the exhaust gas as evenly as possible and in the shortest possible way, so that essentially the entire volume of the SCR substrate 500 can be used for the reduction reaction.

In the example shown, the mixing device 300 and the flow directing plate 400 allow the reductant fluid to flow less than 100 mm, e.g. less than 45mm, upstream of the SCR substrate 500 while achieving good mixing. This offers several advantages, which are explained below.

First, the assembly 16 can fit within an appropriately sized housing 100 by spacing the two substrates 200, 500 slightly further apart to accommodate the mixing device 300 and flow directing plate 400. Therefore, other parts of the vehicle 10 do not have to be changed, which would otherwise require retooling.

Second, the SCR substrate 500 can be housed in the housing 100 near the engine 12 . At this point, the exhaust gas has a high Reynolds number, which facilitates mixing. The exhaust gas temperature is higher and the exhaust gas temperature can be reached more quickly.

Third, the injector 600 for the reducing agent ( 8th ) should not be placed too far upstream of the SCR substrate 500. Therefore, the liquid injector 600 does not have to be too close to the heat of the engine 12 and turbocharger.

Fourth, the proximity of the reductant injector 600 to the SCR substrate 500 means that devices that could be damaged by the reductant need not be located between the reductant injector 600 and the SCR substrate 500 . Sensors, particularly those sensitive to direct contact with liquid, can be moved out of the way to avoid direct contact with the reductant; also, an exhaust gas recirculation port may be moved out of the way to prevent the reductant from being drawn into the engine 12 .

Although not shown, other components of the exhaust system may be provided downstream of housing 100 . For example, the downstream components may include another substrate, which may also be configured for SCR. The further substrate can be supplied with reducing agent from a separate, special reducing agent injection device. The additional substrate can be equipped with its own separate housing. The additional substrate may be larger than the SCR substrate 500 in the housing 100. As such, an exhaust system 14 according to examples of the present disclosure may include two SCR assemblies and two corresponding reductant injectors. The illustrated smaller SCR substrate 500 is configured to heat up and begin to react quickly while the engine 12 is relatively cold and exhaust emissions are at their highest before the additional substrate becomes effective. In other embodiments, SCR could be performed with only one substrate.

The mixing device 300 and flow directing plate 400 of the present examples are intended for the illustrated smaller substrate 500, which is particularly advantageous given the limited space available. However, they could also be used additionally or alternatively for the larger downstream SCR substrate.

As in the 2 , 3 , 8th and 9 As shown, the housing 100 may further include one or more sensor receiving portions 108A, 108B, 108C for one or more sensors. The sensor receiving portions may be protrusions and/or holes on a wall of the housing 100 to allow access to the sensors from the outside. The sensors may include one or more of the following sensors: a temperature sensor, one or more pressure sensors, an oxygen sensor, a nitrogen oxide sensor, or the like.

As illustrated, the sensors may be located upstream of the mixing device 300 where they are protected from the reductant. Temperature sensors may be located upstream of the mixer 300 to allow for clean readings. A sensor receiving section 108A is located at the inlet section 102. Another sensor receiving section 108B is located at the outlet section 106 after the reductant has been consumed. Another sensor receiving section 108C for a set of sensors 702, 704, 706 is located in the middle section 104 of the housing, between the upstream substrate 200 and in front of the reducing agent injector 600 and the mixing device 300. The sensors 702, 704, 706 can e.g. B. include a nitrogen oxide sensor, an oxygen sensor and / or a temperature sensor.

As in 8th shown, the housing 100 includes a receiving portion 110 for the reductant injector 600. The reductant injector 600 is shown in situ. The reducing agent injector 600 can inject the reducing agent directly into the mixing device 300 . In some examples, reductant injector 600 may be water cooled and/or heat shielded due to its proximity to engine 12 . During cold starts, the reductant injector 600 may be equipped with heated urea feed lines.

The mixing device 300 will now be described in more detail. The mixing device 300 is shaped in such a way that a good mixing of the reducing agent is ensured without requiring a large mixing length in the L-axis.

As in 3 As shown, a first portion P1 of the exhaust gas enters a closed mixing chamber 306 within the mixing device 300 via the upstream inlet ports 302 of the mixing device 300 . Another, second portion P2 of the exhaust gas bypasses the mixing device 300 through a bypass passage 304 without entering the mixing chamber 306 . The reducing agent injector tor sprays the reductant RF into the mixing chamber 306 to form a mixture with the first portion P1 of the exhaust gas. The reductant RF mixes with the first portion P1 of the exhaust gas in the mixing chamber 306 without having to move in the L axis. The reductant may vaporize and decompose into ammonia as it flows through the mixing chamber 306 or mixer ring. The mixture then exits the mixing chamber 306 via outlet ports 308 to join the diverted exhaust gas P2 before flowing to the SCR substrate 500 . The evaporation time in the ring and the merging of the two gas streams through numerous openings allow a reduction in the mixing time and a good distribution of the reducing agent on the SCR substrate 500.

In the figures, but not necessarily in all examples, the mixing chamber 306 is looped in the x-y plane, allowing an axial circulation C of the mixture about the longitudinal axis L . This increases the effective mixing length without the mixing chamber 306 having to extend far in the L-axis.

As in the 5 , 6 and 8th As shown, but not necessarily in all examples, the mixing chamber 306 is generally toroidal in shape to form the loop.

The toroid shown in the figures would be considered a ring toroid since it has a central hole (cavity). This central bypass opening 304 allows the main gas flow to be directed through the toroid with minimal back pressure. The flow directing plate 400 blocks the bypassed exhaust gas and forces a portion of the gas flow into an annular region where the reductant is injected. The toroid's exhaust ports are strategically placed to inject vaporized and decomposed reductant into the diverted gas stream. The position of the toroid outlet openings is determined by simulations of the reductant distribution on the inlet side of the SCRF substrate.

In an alternative embodiment with higher back pressure, the center hole could be blind and the bypass passage 304 could be located elsewhere.

The L axis runs through the center of the bypass channel 304. The mixing chamber 306 can, but need not, be rotationally symmetrical about the L axis. The illustrated mixing device 300 has a rectangular toroidal shape, but only because the x-y cross-section of the example housing 100 is rectangular - other shapes are possible.

Although the interior of the mixing chamber 306 has a substantially circular cross-section as shown in FIG 9 shown corresponding to a classic toroidal shape, the term "toroidal" should be understood to also cover other cross-sectional shapes of the chamber, such as e.g. B. square shapes. In addition, the loop formed by the chamber 306 need not be a surface of revolution but may be made up of vertices, while in the general sense it is considered toroidal.

As can be seen in the figures, the mixing device 300 requires little installation space along the L-axis inside the housing 100.

Mixing device 300 is shaped to fit within housing 100 in a substantially vertical, non-tilted orientation such that an equatorial plane EE ( 9 ) of the toroid is substantially perpendicular to the L-axis and such that the center hole (bypass passage 304) faces the exhaust gas. Furthermore, the mixing chamber 306 can have a depth in the L-axis of between 3 cm and 20 cm, e.g. B. about 4 cm, which shows how little space is required in the downstream direction. This depth dimension is less than the average radius of the chamber 306 to its outer perimeter. The ring is sized to vaporize and decompose the required amount of reducing agent. In one embodiment, the mixing device 300 is dimensioned such that between 10% and 50%, e.g. B. 15%, of the total gas flow flow through the ring.

The mixing device 300 can be formed into the ring shape using techniques such as pressing. Such techniques avoid welding to facilitate attachment to housing 100 and allow for better accommodation of thermal expansion and contraction.

In one embodiment, the mold may be formed by clamping or otherwise attaching a pair of pressed looped sheets 316A, 316B ( 9 ) can be formed from a suitably strong material such as steel or, in particular, stainless steel. To form a toroid, each sheet 316A, 316B comprises a looped half tube (half toroid). The half tubes can be connected in the equatorial plane EE of the toroid. Optionally, for ease of assembly, the sheets 316A, 316B may be locally welded together to facilitate installation. Optionally, bridging pieces can be added to hold the assembly to the fluid-carrying plate 500 as well. When located in the housing 100, the mixing device 300 can primarily be a frictional connection with the Housing 100 are held. As will be apparent to those skilled in the art, other bonding techniques and methods are also useful.

Each plate 316A, 316B may further include an inner mating surface 322A, 322B on the inner perimeter of the half-tube and an outer mating surface 318A, 318B on the outer perimeter of the half-tube. Mating is a continuous surface-to-surface contact where a connection can be made. The manufacturing process bonds the inner mating surface 322A of the first sheet 316A to the inner mating surface 322B of the second sheet 316B, and the outer mating surface 318A of the first sheet 316B to the outer mating surface 318B of the second sheet 316B.

As in 9 As shown, each plate 316A, 316B may further include a distal mating flange 320A, 320B configured to mate with the interior surface of the housing 100. FIG. The outer mating surface 318A, 318B may form a web that supports the distal mating flange 320A, 320B. Web 318A and flange 320A form an L-shaped cross-section of a single sheet 316A. After the sheets 316A, 316B are joined together, the webs 318A, 318B and flanges 320A, 320B form a T-shaped cross section. The T-shaped ridge and flange extend in a loop around the outer periphery of the mixing chamber 306.

As in the 3 , 5 , 6 and 8th As shown, the mixing device 300 may optionally include at least one secondary bypass duct 310 to create a separate flow path that allows a third portion P3 of the exhaust gas to pass one or more peripheral sensors or help channel ammonia onto the downstream substrate . The secondary bypass duct 310 has a smaller cross-sectional area than the main bypass duct, and the outlet openings 308 of the mixing device 300 all face away from the secondary bypass duct 310 .

In the figures, the secondary bypass passage 310 is located at a radially distal location from the center of the mixing device 300 . The secondary bypass passage 310 may be formed between the housing 100 and the outer periphery of the mixing device 300 .

The secondary bypass passage 310 may be positioned proximal to the sensor receiving portion 108C of the central portion 104 of the housing 100 such that the heads of one or more sensors 702, 704, 706 are positioned in the portion 108C in the flow path of the secondary bypass passage 310.

The secondary bypass passage 310 can be created by introducing a discontinuity in the outer mating surfaces 318A, 318B of the plates 316A, 316B. The discontinuity means that the outer pads 318A, 318B do not extend around the entire circumference of the looped mixing channel. The discontinuity is a gap that allows a portion of the exhaust gases to flow directly through, creating the secondary bypass passage 310 . The same discontinuity can be provided in the distal mating flange 320A, 320B.

Advantageously, the mixing chamber 306 in the vicinity of the secondary bypass passage 310 can have approximately the same cross-sectional area as the rest of the mixing chamber 306 without being locally restricted. As in the 5 , 8th and 9 1, however, an indentation 314 may be provided in the surface of the mixing chamber 306 of the mixing device 300 to provide additional clearance for a sensor head and gas flow to such an external sensor 702. The indentation 314 is so small that the cross-sectional area of the mixing chamber 306 at this location can still be considered approximately the same as the area of the mixing chamber 306 elsewhere.

The inlet ports 302 and outlet ports 308 of the mixing device 300 will now be described in more detail.

In the figures, but not necessarily in all examples, the inlet openings 302 are provided with louvers, the louvers being a flow directing means causing an axial flow circulation C in a configured clockwise or counterclockwise direction. It goes without saying that other passive or active flow guide devices can also be provided.

A louver is a baffle that effectively changes the orientation of the opening plane of the intake port 302 . The flow entering the inlet port is generally directed in a direction perpendicular to the plane of the inlet port 302 opening due to the pressure field around the leading and trailing edges of the port.

4 12 shows a detail view of a louvered intake port 302 that includes a vent slot 303. FIG. The ventilation slot 303 is hood-shaped in this example and can be referred to as a hood. A hood 303 is a raised cover that has its own opening that is angled relative to the incoming flow. The hood 303 protrudes from the wall of the mixing device 300 in the flow direction.

In the 4 The hood 303 shown can be roughly described as a hollow paraboloid shape resulting from an eccentric conic section, where the conic section is an opening through which the exhaust gas can enter. The eccentricity of the conical section determines the angle of the opening and therefore affects the amount of change in direction. Decreasing the eccentricity would lead to an ellipsoidal dome, increasing the eccentricity to a hyperboloidal dome.

The vent shown has a male shape where the hood 303 lies outside the mixing chamber 306 and forms a leading edge where the incoming flow encounters first. Alternatively, the vent can also have a female shape that protrudes into the mixing chamber 306, as in FIG 10 shown.

The hoods 303 can be formed by stamping processes without requiring additional fabrication. Referring to the manufacturing method described above and to 9 For example, the hooded inlet ports 302 could be formed in one sheet 316B of the pair of sheets 316A, 316B. The outlet openings 308 can be stamped in the other sheet metal 316A.

A hooded inlet port 302 may be formed by piercing a slot 324 or similar hole in the sheet metal 316B in the desired orientation and forming the hoods 303 by locally deforming the sheet metal 316B on the desired side of the slot 324 (e.g depending on whether the flow circulation C is clockwise or counterclockwise). Piercing and shaping could correspond to a single tool strike. The pierced slits 324 can, as in 4 shown, be slightly rounded to reduce material stresses.

5 12 shows the number and location of the inlet ports 302. The inlet ports 302 may be arranged in a toroidally spaced array 302A-302H around the mixing chamber 306. FIG. The toroidal distance refers to the distance in a toroidal direction φ, where the toroidal direction follows a large ring around the toroid surrounding the central hole.

5 Figure 12 shows eight inlet ports 302A-302H in series, although a different number of inlet ports could be provided. Although at least one inlet port 302 provides some degree of mixing, multiple inlet ports provide high circulation and mixing. For reasons of space, the number of openings would be limited.

The annular spacing Δφi between inlet ports 302A-302H in the series may be constant or variable as illustrated. The row of inlet openings 302 optionally does not extend around the entire circumference of the toroid. Therefore, the first inlet port 302A and the last inlet port 302H of the series have a greater toroidal spacing than the spacing between the other inlet ports 302B-302G. This increased void space may be located near the sensor receiving portion 108C of the middle section 104 of the housing 100 to ensure that backflow of liquid from the inlet ports 302 does not reach the sensors 702,704,706.

The louvers may be angled relative to one another to form a clockwise or counterclockwise pattern that follows the curvature of the loop so that each louvered inlet port 302 redirects flow in the desired clockwise or counterclockwise direction. The inlet port is used to create a spiral flow in the ring to mix the reductant and gas.

As in 9 As shown, the inlet openings 302 may be in a constant or variable poloidal position θi. A poloidal position refers to a position in a poloidal direction θ that is orthogonal to the toroidal direction and follows a small ring around the surface. Poloidal coordinates may be used to indicate whether a feature is upstream or downstream with respect to the direction of exhaust flow P2 through bypass passage 304, for example. As in 9 shown, the inlet openings 302 are directed upstream. 9 12 shows the inlet ports 302 in a poloidal position θi that is approximately perpendicular to the toroid's equatorial plane EE (xy plane) and on the upstream side of the equatorial plane EE.

Once the first portion P1 of the exhaust has entered through the intake ports 302 , the exhaust circulates and mixes with the reductant, which is sprayed directly into the mixing chamber 306 . The manner in which the reducing agent is sprayed into the mixing chamber 306 is best in the 3 , 5 and 8th shown. In 8th For example, the mixing device 300 is shown transparent to show the interior of the chamber where an injector inlet 312 can be seen.

The injector inlet 312 is any suitable device in the mixing device 300 that allows the injector 600 for the reductant to spray into the mixing chamber 306 . In the figures, injector inlet 312 includes an opening for receiving a spray pattern from reductant fluid injector 600 . The injector inlet 312 may be located at the distal end of a branched chamber 313 , with the branched chamber 313 having a proximal end that merges into the toroidal main mixing chamber 306 .

As shown, branched chamber 313 may be aligned with injector inlet 312 such that reductant is flow sprayed into chamber 306 in the configured direction of exhaust gas circulation C (clockwise or counterclockwise). This improves mixing and vaporization since spraying against the flow direction can reduce circulation C. In the figures, branched chamber 313 extends in a direction that is partially tangential to mixing chamber 306 and partially radially inward. The tangential extension can be clockwise or counterclockwise.

The illustrated injector inlet 312 may be arranged annularly in front of the first inlet opening 302A of the row of inlet openings 302 so that the reducing agent droplets can bypass as many of the inlet openings 302 and outlet openings 308 as possible. This gives the reductant time to evenly vaporize and mix with the exhaust gases in the toroid before exiting the exhaust ports 308 .

The injected reductant droplets form part of the circulating flow in the mixing chamber 306. The droplets vaporize in the circulating exhaust flow. Larger droplets are conveyed to the distal wall of the mixing chamber 306 where they are retained until vaporized. This makes sense as larger drops are less effective for the SCR.

The mixture can make at least a half revolution through the mixing chamber 306 or more. This recirculation of the mixture around the perimeter of the mixer 300 allows time for the reductant to vaporize, generate ammonia, and mix thoroughly so that no additional tailpipe length is required. The vaporized mixture then exits through the outlet openings 308 of the mixing device 300 .

The outlet openings 308 are now defined.

Like the inlet openings 302, the outlet openings 308 can consist of a plurality of openings in the mixing device 300. However, there are a number of differences between the 302 inlet ports and the 308 outlet ports.

In particular, the outlet openings 308 are not directed in the same polar direction as the inlet openings 302 . The outlet openings 308 are in the 6 and 9 shown as not being on the upstream side of the mixing device 300, for example. The outlet openings 308 can instead point downstream, ie to the other side of the equatorial plane EE of the annular mixing device 300 .

In the examples shown, the outlet openings 308 are arranged proximal to the bypass channel 304 . As in 9 As shown, the outlet openings 308 face in a poloidal direction θo that is downstream and radially inward toward the bypass passage 304 . In an alternative example, the outlet openings 308 could point radially toward the bypass passage 304, but not downstream or upstream. In another alternative example, the outlet openings 308 are not located near the bypass channel 304.

9 Figure 12 shows the exhaust ports 308 which distribute the ammonia and urea evenly into the gas stream and onto the next substrate. The exhaust ports 308 are in a poloidal position θo corresponding to a value between about 20 degrees and about 70 degrees from the toroid's equatorial plane EE and facing the bypass passage 304 to utilize the venturi effect described later.

The positioning of the outlet openings 308 close to the bypass channel 304 ensures that the larger droplets of reductant are distributed distally from the outlet openings 308 according to CFD simulations. Therefore, the larger droplets are less likely to pass through the outlet openings 308.

Another difference between the outlet openings 308 and the inlet openings 302 is that the outlet openings 308 may be of a different (eg, smaller) size than the inlet openings 302 to control the downstream distribution of the reductant.

The total area of the outlet openings controls the vaporization time for the reductant as the mixture continues to circulate in the mixing device 300 prior to exit.

In the 6 and 8th the number and arrangement of the outlet openings 308 are shown. The outlet openings 308 may be arranged in a toroidally spaced series of outlet openings 308A-308R around the mixing chamber 306. This allows the mixture to combine with the diverted exhaust gas P2 at multiple locations to quickly form a homogeneous mixture.

As illustrated, the mixing device 300 may include more outlet openings 308 than inlet openings 302 . The example shown includes 18 outlet ports 308A-308R, although a different number of outlet ports 308 could be provided.

The annular distance Δφo between the outlet openings 308 in the row can be constant, as in FIG 6 shown, or variable. As in 8th As shown, the row of exhaust ports 308 optionally does not extend around the entire circumference of the toroid. Therefore, the first outlet port 308A and the last outlet port 308R in the series have a greater toroidal spacing therebetween to prevent injected droplets from escaping directly from the ring. This increased space may be located near the injector's inlet 312 to ensure that an outlet orifice 308 is not directly in the spray pattern of the reductant injector 600 . The branched chamber 313 for the injector inlet 312 may face this enlarged space free of exhaust ports.

The injector inlet 312 may be farther from the first outlet port 308A in the series than the last outlet port 308R in the series, such that the reductant fluid must travel a longer distance and mix further before reaching the first outlet port 308A.

In an alternative example, the row of outlet openings 308 extends around the entire mixing chamber 306, including near the injector inlet 312. However, the outlet opening(s) near the injector inlet 312 can be poloidally relocated so that they are outside of the Spray pattern of the reducing agent fluid injector 600 are.

Another difference from the inlet openings 302 is that the outlet openings 308 in the example shown are not provided with ventilation slots. Depending on the design, ventilation slots could be used for the outlet openings 308 .

The flow-guiding plate 400 is described in more detail below. Their purpose is to make the mixture entering the SCR as homogeneous as possible. An example is in 7 shown. As shown, the baffle 400 may be flat. The flow directing plate 400 may be perpendicular to the L-axis.

A central area of the flow-guiding plate 400 includes a flow deflector 404. The flow deflector 404 is aligned with the bypass channel 304 of the mixing device 300. FIG. The flow deflector 404 is an area of the flow directing plate 400 that is a solid surface with no openings and therefore no porosity or at least very little porosity compared to a peripheral area of the flow directing plate 400 that has openings 402,406. The bypass channel 304 faces the flow guide plate 404 and the outlet openings 308 of the mixing device 300 essentially face the flow guide plate 404 . In the figures, the outlet openings 308 are angled inward toward the center (L-axis) of the bypass passage 304 .

The flow diverter 404 causes the second portion P2 of the exhaust gas exiting the bypass duct 304 to be diverted away from the L-axis and towards the edge region of the flow directing plate 400 where the openings 402, 406 are located.

The diverted exhaust gas flows through a restricted space between the mixing device 300 and the flow directing plate 400 on its way to the openings 402, 406. The restriction forms a venturi with a corresponding pressure drop. The outlet openings 308 of the mixing device 300 are aligned with this local constriction. This advantageously leads to a low pressure at the outlet openings 308 in order to reduce the resistance to the mixture exiting the mixing device 300 and to further promote the axial circulation and thus the mixing of reducing agent and exhaust gases in the mixing device 300 .

The mixture emerging from the mixing device 300 encounters the flow deflected at a relatively high speed and is deflected directly into the edge area of the flow-guiding plate 400 . Since the mixing device 300 can have a large number of distributed outlet openings 308, the mixture is distributed approximately evenly in the diverted bypass exhaust gas P2. This geometry helps a homogeneous mixture enters the SCR substrate 500.

The geometry described above is also useful for distributing the exhaust gas evenly across the cross-section of the housing 100, e.g. B. when the flow entering the housing 100 is unevenly distributed due to an offset inlet section 102 not aligned with the L-axis.

It is noted that the flow baffle 404 creates a "blind spot" behind the flow directing plate 400 in which the SCR substrate 500 may receive reduced flow. To avoid glare on part of the SCR substrate 500, at least some of the openings 406 of the flow directing plate 400 may be direction changing openings. The direction-changing openings 406 can be e.g. B. act to slat openings.

The louvers 407 of the flow-guiding plate 400 can have a similar geometry as the louvers 303 of the inlet openings 302 of the mixing device 300, for example a hollow paraboloid shape or the like. The louvers may be oriented to redirect the exhaust into the space directly behind the flow deflector 404 to reduce the blind spot. That is, the fins direct the exhaust gases back to the central area, in the direction of the L axis.

7 shows that the openings 402, 406 in the edge area of the flow-guiding plate 400 do not all have to be designed the same. In 7 For example, a first set of openings 406 are louvered to direct flow into a space obstructed by flow deflector 404, while a second set of openings 402 are unlouvered.

The first set of louvered openings 406 is in a first portion (e.g., first half) of the flow directing plate 400 of FIG 7 shown associated with the highest flow rate. This is because, as previously described, an asymmetric inlet section 102 of the housing 100 may result in a higher flow rate at some parts of the cross section of the housing 100 than at others.

The second group of openings 402 can be smaller and/or at least some of the second group of openings 402 can form a perforation pattern. The perforation pattern can be a regular array. The perforation pattern may be on a different portion (e.g., the other half) of the flow directing plate 400 . A perforation pattern helps prevent hot spots from forming on the SCR substrate 500 .

It is understood that a small subset of one or more openings from the first or second set of openings 402, 406 may be located in the portion of the flow directing plate 400 that connects to the other type of opening. 7 FIG. 4, for example, shows a small group of second set openings in the portion of flow directing plate 400 containing first set of louver openings 406. FIG. The arrangement depends on the specific design of the vehicle exhaust, which is determined by simulation and experiment.

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

The mixing device 300 and optionally the flow baffle 400 could be provided as a retrofit kit for an existing housing 100 .

Although embodiments of the present invention have been described in the preceding sections with reference to various examples, it should be understood that changes may be made in the examples provided without departing from the scope of the invention as claimed.

For example, although the above embodiments are intended for mixing an aqueous urea solution with exhaust gases, the fluid could be another fluid intended for mixing with exhaust gases. For example, the fluid could be a gas, such as oxygen for an oxidation catalyst or an oxidation-reduction catalyst. In another example, the fluid could be fuel for a secondary combustion process, such as combustion. B. a fuel burner for igniting a particulate filter.

The mixing device 300 and/or the flow directing plate 400 can be housed in a housing 100 which is separate from a housing with the substrate 500 .

Although the above examples refer to a toroid, a toroidal direction, and a poloidal direction, in other examples, the mixing chamber 306 may have a different loop shape. The poloidal and toroidal directions can be mentioned in connection with other loop shapes.

Although the above examples refer to a mixing chamber 306 forming a compact closed loop, in other examples the chamber could follow a spiral path or another path that extends further downstream.

The features described in the preceding description can also be used in combinations other than those expressly described.

Although functions have been described with reference to particular features, these functions may be performed by other features, whether described or not.

Although features have been described with reference to particular embodiments, these features may be present in other embodiments as well, whether described or not.

Although the foregoing description has attempted to draw attention to those features of the invention deemed to be of particular importance, it should be understood that the applicant reserves the right to grant protection in respect of any patentable feature or combination of features which are mentioned herein and/or shown in the drawings, whether or not particular emphasis is placed on them.

Claims (17)

Mixing device for mixing an injected fluid with the exhaust gas output of an internal combustion engine, the mixing device comprising: one or more intake ports configured to receive a first portion of the exhaust gas; a bypass passage configured to receive a second portion of the exhaust gas; a mixing chamber configured to allow the injected fluid to mix with the first portion of the exhaust to form a mixed exhaust; and one or more exhaust ports configured to communicate the mixed exhaust gas with the second portion of the exhaust gas. mixing device claim 1 wherein the mixing device is shaped to cause axial circulation about a longitudinal axis such that the first portion of the exhaust gas and the injected fluid circulate axially within the mixing chamber before exiting through the one or more outlet ports; optionally, the mixing chamber is substantially coaxial with the bypass channel and the longitudinal axis lies substantially in the direction of the bypass channel. mixing device claim 2 wherein the one or more inlet openings comprise louvers configured to impart the axial circulation to the first portion of the exhaust gas. mixing device claim 2 or 3 wherein the mixing chamber is substantially toroidal in shape and the bypass passage is a central hole defined through the substantially toroidal mixing chamber; optionally, the substantially toroidal mixing chamber is shaped and sized to fit within an exhaust system housing in an orientation where an equatorial plane of the substantially toroidal mixing chamber is substantially perpendicular to oncoming exhaust gas. mixing device claim 4 wherein the depth of the substantially toroidal mixing chamber is less than the average outside diameter of the substantially toroidal mixing chamber. mixing device claim 4 or 5 wherein the one or more outlet ports are a plurality of outlet ports arranged in a toroidally spaced array around the substantially toroidal mixing chamber, and/or wherein the one or more inlet ports are a plurality of inlet ports arranged in a toroidal spaced row around the substantially toroidal mixing chamber. Mixing device according to one of Claims 4 until 6 wherein the one or more inlet ports are oriented to face in a different poloidal direction than the one or more outlet ports; optionally the one or more inlet ports are poloidally aligned to face a first direction, wherein the one or more outlet ports are poloidally aligned to face a second direction, and wherein the first direction and the second direction opposite sides of an equatorial plane of the substantially toroidal mixing chamber. Mixing device according to one of Claims 4 until 7 , wherein the one or more outlet openings are poloidally aligned to face the bypass passage. Mixing device according to one of the preceding claims, wherein the one or more outlet openings have smaller cross-sectional areas than the one or more inlet openings. Mixing device according to one of the preceding claims, wherein the one or more outlet openings are arranged in the vicinity of the bypass channel, so that a vaporized phase of the fluid can pass through the one or more outlet openings, while droplets of the fluid are distributed onto a part of the mixing chamber , remote from the bypass channel where the droplets are retained for evaporation. The mixing device of any preceding claim, wherein the mixing chamber includes an injector inlet for receiving fluid injector spray; optionally, the injector inlet is oriented to inject streamwise in a configured direction of exhaust gas circulation within the mixing chamber. mixing device claim 11 wherein the one or more outlet ports are a plurality of outlet ports, wherein a distance between a first pair of the outlet ports is increased relative to an average distance between the outlet ports as a whole, and wherein the injector inlet is aligned with the increased space between the first pair of outlet ports is. A mixer assembly comprising the mixing device of any preceding claim and comprising a flow directing plate configured to be located downstream of the bypass duct, the flow directing plate including a flow deflector and the bypass duct and the one or more outlet openings facing the flow deflector are; optionally, the flow directing plate includes a plurality of openings in a perimeter of the flow deflector, where the openings may include louvered openings configured to direct flow into a space occluded by the flow deflector. mixer arrangement Claim 13 with a substrate housing arranged to receive the mixing device and one or more substrates. mixer arrangement Claim 13 or 14 comprising a secondary bypass channel formed between the substrate housing and an outer periphery of the mixing device, wherein the one or more outlet openings face away from the secondary bypass channel and wherein the secondary bypass channel has a smaller cross-sectional area than the first bypass channel; optionally, the mixing assembly is configured to receive one or more sensors and to position the one or more sensors in a flow path connected to the secondary bypass passage. Exhaust system with the mixer arrangement according to one of Claims 13 until 15 . vehicle with the exhaust system Claim 16 .

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