KR20090094457A - Fluid injecting and mixing systems for exhaust after-treatment devices - Google Patents

Abstract

A system for applying secondary fluids to vehicular exhaust after-treatment apparatus utilizes a mixing chamber coupled for receipt of a portion of the vehicle's exhaust flow. A source of secondary fluid is coupled to the mixing chamber and a fluid distribution element is positioned in a mean exhaust flow conduit upstream of the exhaust after-treatment apparatus. The fluid distribution element presents a preselected pattern of fluid flow toward an upstream face of the after-treatment apparatus.

Description

FLUID INJECTING AND MIXING SYSTEMS FOR EXHAUST AFTER-TREATMENT DEVICES

This application claims priority to US patent application Ser. No. 11 / 862,293, filed September 27, 2007, and US provisional application 60 / 874,921, filed December 14, 2006, which is incorporated herein by reference.

The present invention relates to exhaust gas aftertreatment devices, and more particularly, to the regeneration, oxidation or reduction of exhaust gas by such devices.

The descriptions in this paragraph only provide background information relating to the present invention and do not constitute prior art.

Exhaust aftertreatment systems for upcoming model years of high speed diesel engines typically include diesel particulate filters (DPF), nitrogen oxide (NOx) absorbers (LNT) and selective catalytic reduction (SCR) systems. do. Regenerative oxidizing or reducing fluids (secondary fluids) are required for proper operation and / or maintenance of the substrates used in each of these devices. In most applications, diesel particulate filters (DPFs) require the injection of hydrocarbons, such as diesel fuel, for periodic regeneration or oxidation of soot trapped in the filter. SCR systems rely on the injection of a reducing agent (typically urea) upstream of the catalyst for the reduction of the nitrogen oxides emitted. LNTs generally require periodic regeneration using hydrocarbon or carbon monoxide rich exhaust gases, provided by injecting excess diesel fuel into the exhaust stream.

Currently a common method for the injection of these hydrocarbon fuels and urea is to inject them into the exhaust pipe upstream of the aftertreatment device. Such injection must be done at a very sufficient upstream location of the device, in particular a linear distance upstream of at least 10 times the diameter of the pipe, to ensure proper mixing, evaporation and / or hydrolysis of the fluid being injected.

Disadvantages of conventional methods arise when SCR, LNT, and / or DPF systems must be packaged into limited space or combined together in a common housing. Insufficient exhaust pipe lengths available for proper mixing, evaporation, and / or hydrolysis of the injected fluid, or the use of sufficient exhaust pipe lengths, can result in an unacceptable total back pressure for the aftertreatment system. Due to packaging constraints, aftertreatment parts may also be present in the exhaust pipe paths required for spraying, mixing, evaporating, and / or hydrolysis, but this would interfere with the proper functioning of the aftertreatment devices.

Accordingly, there is a technical need for an apparatus for facilitating proper mixing, evaporation, and / or hydrolysis of secondary fluids injected where no appropriate length of exhaust pipe is available.

The present invention provides auxiliary piping, alternative pipe routing and auxiliary devices required to facilitate the injection, mixing, evaporation and / or hydrolysis of secondary fluids required for automotive exhaust aftertreatment systems. Turned to. Such secondary fluids are, for example and without limitation, regenerating fluids or oxidizing fluids or reducing fluids.

In one aspect of the invention, the pipes provided along the aftertreatment device run parallel to the exhaust gas flow. The pipe enters from the side of the aftertreatment device, upstream from the device substrate requiring a secondary fluid. Before and during injection, the pipe supplies compressed air to obtain a pressure higher than the pressure at which it enters the exhaust flow and to obtain a flow rate sufficient for proper mixing, evaporation and / or hydrolysis of the secondary fluid. Will receive. At the point where the mixing tube enters the exhaust flow, the valve maintains this positive pressure in the tube. The secondary fluid is injected into the tube and the valve is opened as needed.

In another aspect of the invention, at least one of the pipes parallel to the main exhaust pipe between the engine and the aftertreatment device is located within the aftertreatment system from a position away from the turbocharger upstream of the exhaust manifold or turbine inlet. It passes up to the point directly upstream of the part requiring the injected secondary fluid.

In another aspect of the invention, the exhaust aftertreatment apparatus is provided with a central channel or conduit extending through the apparatus substrate comprising a mixing chamber for exhaust gas / secondary fluid.

Further fields of applicability will become apparent from the detailed description provided. It is to be understood that the following detailed description and examples are for illustrative purposes only and are not intended to limit the scope of the invention.

The drawings described below are for illustrative purposes only and do not limit the scope of the present invention in any way.

Objects and features of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

1 is a cross-sectional view of an exhaust aftertreatment system comprising various aftertreatment devices in one housing, the system comprising a parallel path secondary fluid mixing system arranged in accordance with the present invention.

2 is a partial side cross-sectional view of a first alternative embodiment of an exhaust aftertreatment system arranged in accordance with the principles of the present invention.

3 is a partial cross-sectional view of a second alternative embodiment of an exhaust aftertreatment system arranged in accordance with the principles of the present invention.

4A and 4B show side and cross-sectional views, respectively, of the post-treatment apparatus of FIG. 3, depicting a regenerative fluid distribution element disposed in accordance with the principles of the present invention.

5 is a cross-sectional view of a third embodiment of an exhaust gas aftertreatment system arranged in accordance with the principles of the present invention;

6 is a perspective view of an alternative exhaust aftertreatment device having an internal mixing chamber with an external shell removed and arranged in accordance with the principles of the present invention.

The following description is illustrative only and is not intended to limit the invention, application, or uses.

Referring to FIG. 1, the exhaust aftertreatment system 100 includes a versatile exhaust aftertreatment apparatus that includes several elements. The input exhaust for the device is shown by arrow 130 and the output exhaust from the device is shown by arrow 132. The multipurpose aftertreatment device comprises a first diesel oxidation catalyst or NOx absorber substrate 102a, an optional catalytic reduction substrate 104, a second diesel oxidation catalyst or NOx absorber substrate 102b, a diesel particulate filter substrate 106 and a first 3 diesel oxidation catalyst or NOx absorber substrate 102c. Each of these substrates is separated by an inter-substrate gap for receiving a secondary fluid distribution element described below.

Urea mixing conduit 106 communicates substantially parallel to the exhaust gas flow along the exhaust aftertreatment and input 108 for mixing in chamber 116 of conduit 106. Accepts a combination of urea and compressed air. Valve 120a is positioned between substrates 102a and 104 and has a plurality of radial holes or inlets 123 for directing secondary fluid from conduit 106 to the input surface of substrate 104. Compressed air and the urea mixture are introduced (inserted) into the first regenerative fluid distribution element 122a that carries.

The hydrocarbon mixing tube 110 also extends substantially parallel to the exhaust gas flow and receives a mixture of hydrocarbons such as diesel fuel and compressed air at the input 112 for mixing in the chamber 118 of the conduit 110. It is. Optionally, a glow plug or other auxiliary thermal component 114 may extend into the mixing chamber 118. The valve 120b is used to meter the mixture of exhaust gas and secondary fluid flowing into the dispensing element 122b. Conduits 106 and 110 enter from the side of the aftertreatment device upstream from the individual substrate requiring the secondary fluid. Prior to and during the injection, these tubes are used to obtain a higher pressure than the pressure at the point where the fluid / exhaust gas mixture enters the exhaust flow through the device and for proper mixing, evaporation and / or hydrolysis of the secondary fluid. Additional compressed air is supplied for a sufficient flow rate for decomposition. At the point where the secondary fluid enters the exhaust flow, a valve maintains this amount of pressure in the tube. The secondary fluid is injected and the valve is opened as needed.

These parallel tubes are blown with air into the exhaust aftertreatment inter-substrate chamber upstream of the substrate through a series of orifices adjusted to provide the required flow pattern across the face of the substrate to be treated. The secondary fluid mixture.

Heating devices to assist in the evaporation of secondary fluids, burners to assist in the regeneration of LNTs and / or DPFs, and / or other devices to generate laminar or turbulent aspects or to assist in the mixing of exhaust gases and secondary fluids. Auxiliary devices can also be incorporated into this parallel piping system. Instead, conduits 106 and 110 may be physically attached to a shell of the aftertreatment housing in such a way that heat transfer from the aftertreatment device aids in heating the air / secondary fluid mixture. .

In the embodiment of FIG. 2, the exhaust gas aftertreatment system 200 utilizes auxiliary piping to establish a parallel exhaust gas flow stream through which the secondary fluid is injected. The diesel engine 202 has an exhaust manifold 204 that is emptied into the turbocharger 206. The exhaust gas is then sent to the input 222 of the exhaust gas aftertreatment device 220 via the exhaust pipe 208. Substantially parallel to the exhaust gas flow through conduit 208 is similarly a conduit that carries the exhaust gas from exhaust manifold 204 or optionally turbocharger 206 to second input 224 of aftertreatment device 220. (210). Injector 212 injects the secondary fluid required into the exhaust gas stream flowing through conduit 210 for introduction into device 220 at input 224. This mixture flows through the substrate 226 of the aftertreatment device 220 and exits the output 228 to be received by a tailpipe or additional exhaust pipe 230. Accordingly, conduit 210 may be located at any point on the exhaust manifold 204 or at any point in the aftertreatment system from the turbocharger 206 upstream of the turbine inlet, directly to the substrate component requiring the injected secondary fluid. Upstream. As conduit 210 begins at a position that has a pressure that is much higher than the pressure just upstream of the substrate 226, exhaust gas flow through conduit 210 passes past injector 212 and of conduit 210. It is ensured through the mixing length.

In another possible configuration, such as shown in FIG. 3, the tube or tubes carry exhaust gas along a path parallel to the flow through the aftertreatment substrate, bypass and spray the secondary fluid, proper mixing, evaporation, and / or Or allow a sufficient diameter-to-length ratio for hydrolysis. The exhaust aftertreatment system 300 includes an aftertreatment device 306 positioned between an exhaust pipe 304 and a tailpipe 332. Exhaust gas flow is indicated by arrow 302.

Exhaust gas enters the apparatus 306 from the inlet 308 into the input chamber 310. Exhaust gas from chamber 310 flows through substantially parallel conduit 312 past injector 316 for injecting secondary fluid into the exhaust gas flow, as indicated by substrate 326 and arrow 322. This mixture then flows into the chamber 311 of the device 306 where it flows through the substrate 328 and back through the second parallel tube 314 past the second injector 318. The mixture flows back into the chamber 310 for processing of the substrate 326 as indicated by arrow 324. This configuration may not necessarily transport gas from the higher pressure region to the lower pressure region, so that the secondary pumping device 320 may facilitate proper flow and proper mixing, evaporation and / or hydrolysis of the secondary fluid. ) May be made part of system 300.

4A and 4B, the embodiments of FIGS. 2 and 3 provide a series of mixtures of exhaust gas and injected secondary fluids in a donut or helical ring 402 adjacent to the outer skin of the chamber. Through holes 404 orifices are released into the chamber upstream of the aftertreatment substrate component to be processed. In cases where injection is only required on a periodic basis (eg LNT or DPF regeneration), at least one valve may be arranged in the system to start and stop the exhaust flow through the parallel pipe or tubes. have.

A third embodiment of an exhaust aftertreatment system arranged in accordance with the principles of the invention is shown in FIG. 5. The exhaust aftertreatment system 500 includes an input exhaust 502 having an injector 504 for injecting secondary fluid into the exhaust gas stream entering the input 518 of the aftertreatment apparatus 510. In this embodiment, the mixing chamber is contained within the aftertreatment device 510 by forming a channel for receiving a mixing conduit 508 extending through the substrate 512. In the individual device shown in FIG. 5, the exhaust gas outlet 520 of the apparatus 510 is located at the same end as the exhaust gas inlet. Swivel chamber 516 receives the mixture of exhaust gas and secondary fluid, rotates it in reverse and flows through the substrate apertures to outlet chamber 514 for discharge from outlet 520.

An alternative embodiment of the post-processing device 510 shown in FIG. 5 is shown in FIG. 6. In the arrangement of FIG. 6, two tubes pass from the chamber in front of the aftertreatment substrate to the backside through the aftertreatment apparatus. The first of these tubes carries the exhaust gas through the catalyst substrate to the back side of the substrate where the flow is reversed and passes back through the substrate itself. The second tube carries the gas after the emergence of gas from the front portion of the substrate and reversed backward through the internal channel of the substrate to the chamber in front of the second downstream substrate. One example would be an SCR system with DPF, where secondary fluids must be injected and mixed before each aftertreatment device. The arrangement of FIG. 6 by conveying, bypassing, or permitting a full length diameter ratio for spraying and proper mixing, evaporation, and / or hydrolysis along the path parallel to the flow through the aftertreatment component. Otherwise enables the proper introduction of the secondary fluid in situations that are otherwise impractical.

Further, where injection of secondary fluid is required only on a periodic basis, at least one valve may be located in the system to prevent the injectors from the exhaust flow.

The apparatus 600 of FIG. 6 receives the exhaust gas flow indicated by arrow 604a from the exhaust pipe 602. Exhaust gas input conduit 606 defines a first mixing chamber for secondary fluid that is injected into the input volume defined by a first partition 608 on one side therefrom via the exhaust and injector. . The exhaust / secondary fluid mixture is then turned around on the downstream side of the substrate 616, defined by the second partition 618, under the conduit 606 as shown by arrow 604b. Proceed to the chamber. The exhaust / secondary fluid mixture then proceeds backward through the structure of the substrate 616 itself via arrow 604c to a second injection zone defined between the substrate 616 and the partition 608. Wherein the second injector is reversed through the substrate 616 via a second internal conduit 614 for downstream use by another post-treatment device located to the left of the partition 618 shown in FIG. 6. Inject another secondary fluid into the exhaust stream for delivery. This output flow of exhaust / secondary fluid is represented by arrow 604d.

Systems deployed in accordance with the principles of the present invention provide packaging advantages in that the envelope for the aftertreatment system is small and the combination of aftertreatment devices must be coupled together in a common housing shell. Likewise, the systems according to the invention provide an easy arrangement even in situations where the length of the main exhaust pipe to support proper mixing, evaporation, and / or hydrolysis of the secondary fluid is insufficient. In addition, such systems provide more effective mixing and uniformity of the mixture in cases where mixing conduits can be made to have a better straight line diameter ratio and / or a more straight path than the main exhaust pipe. Moreover, into the upstream region of the aftertreatment component to be treated, an adjustable entry path of the secondary fluid-rich mixture is provided. Finally, the systems according to the present invention allow the use of larger diameter catalyst substrates (carriers) (for better flow uniformity and lower system back pressure), which in many cases are such substrates (carriers). The length of the tube between the substrates (carriers), the cone of the tip, etc., which would otherwise be suitable for the injection and proper mixing of the secondary fluid in use and the exhaust gas stream in other cases. Remove it.

The invention has been described with reference to the examples presented for purposes of example only. The invention is described with reference to the properly interpreted claims.

Claims (12)

A mixing chamber coupled to receive a portion of the exhaust flow at the mixing chamber inlet; A source of secondary fluid in fluid communication with the mixing chamber; And A fluid distribution element located upstream of the main exhaust flow conduit of the exhaust aftertreatment device and coupled to the output of the mixing chamber and operative to exhibit a preselected flow pattern towards the upstream face of the aftertreatment device. A system for applying secondary fluids to a vehicle aftertreatment device. The method of claim 1, And the mixing chamber is separate from the main exhaust flow conduit. The method of claim 2, And the mixing chamber includes a passage extending parallel to the main exhaust gas flow conduit. The method of claim 1, And a secondary fluid injector for injecting a secondary fluid received from the source of the secondary fluid into the mixing chamber under pressure. The method of claim 1, And a valve located at the output of the mixing chamber, the valve selectively allowing and inhibiting fluid exchange between the mixing chamber and the fluid dispensing element. The method of claim 1, Wherein said exhaust aftertreatment device comprises a particulate filter and said secondary fluid comprises a filter regenerative fluid. The method of claim 1, Wherein said exhaust aftertreatment device comprises a selective catalytic reduction catalytic converter and said secondary fluid comprises a reducing agent. The method of claim 1, Wherein said exhaust aftertreatment device comprises a nitrogen oxide absorbent and said secondary fluid comprises a transducer substrate regenerative fluid. The method of claim 1, And the mixing chamber is located within the housing of the aftertreatment device. The method of claim 3, wherein The mixing chamber input is coupled to an exhaust manifold of the vehicle, wherein the secondary fluids are applied to a vehicle aftertreatment device. The method of claim 1, And the fluid distribution element comprises perforated conduits having a series of holes disposed about an upstream face of the aftertreatment device to exhibit the preselected aspect. The method of claim 11, And the perforated conduit is toroidal.

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