Flow Distributor For Engine Exhaust Aftertreatment Component

- CATERPILLAR INC.

An engine exhaust aftertreatment component includes a housing defining an exhaust flow from an exhaust inlet to an exhaust outlet. An exhaust aftertreatment substrate is positioned within the housing between the exhaust inlet and the exhaust outlet and has an upstream face, which includes an inner region surrounded by an outer region. A flow distributor is positioned in the housing upstream from the exhaust aftertreatment substrate and divides the exhaust flow into a first portion directed toward the inner region through a first set of perforations and a second portion directed toward the outer region serially through a second set of perforations and a third set of perforations.

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Description
TECHNICAL FIELD

The present disclosure relates generally to a flow distributor for distributing exhaust flow across an upstream face of an exhaust aftertreatment substrate, and more particularly to a flow distributor for directing a first portion of the exhaust flow through a first set of perforations and directing a second portion of the exhaust flow serially through second and third sets of perforations.

BACKGROUND

Toxic emissions produced by internal combustion engines are the subject of environmental concern and have prompted increasingly stringent emissions regulations by the government. Toxic emissions produced by diesel engines, for example, include hydrocarbons, nitrogen oxides, carbon monoxide, and particulate matter. To reduce these toxic emissions and comply with governmental regulations, a number of exhaust aftertreatment components, including particulate filters and catalytic converters, have been developed. Exhaust aftertreatment systems may also include a number of other devices, including exhaust gas recirculation components and devices for regenerating other of the aftertreatment components. As such, exhaust aftertreatment systems, which may include components required for compliance with governmental regulations, may occupy a significant footprint of an engine or machine system in which the exhaust aftertreatment system is utilized. As further engine and machine development occurs, there is a continuing need to increase efficiency and reduce size of engine and machine components.

With particular regard to exhaust aftertreatment components, there is a similar need to increase efficiency and reduce component size. However, most aftertreatment components have detailed performance requirements that, oftentimes, require a specific amount of space to achieve. U.S. Patent Application Publication No. 2005/0223703 to Wagner et al. is directed to a muffler including a catalytic converter for a diesel engine. In particular, the catalytic converter portion of the muffler is positioned between the muffler inlet and a sound attenuation portion of the muffler. An inlet tube operates as a flow distribution element and, according to one embodiment, includes a perforated tube terminating in a crimped or folded end. According to other configurations, the flow distribution element may include a perforated cylindrical tube terminating in a perforated curved cover, or a domed perforated baffle positioned between a non-perforated inlet tube and the catalyst. Although the combination muffler and catalytic converter of Wagner et al. may provide acceptable performance for some applications, there remains a continuing need to improve efficiency and reduce spatial requirements.

The present disclosure is directed to one or more of the problems or issues set forth above.

SUMMARY OF THE DISCLOSURE

In one aspect, an engine exhaust aftertreatment component includes a housing defining an exhaust flow from an exhaust inlet to an exhaust outlet. An exhaust aftertreatment substrate is positioned within the housing between the exhaust inlet and the exhaust outlet and has an upstream face, which includes an inner region surrounded by an outer region. A flow distributor is positioned in the housing upstream from the exhaust aftertreatment substrate and divides the exhaust flow into a first portion directed toward the inner region through a first set of perforations and a second portion directed toward the outer region serially through a second set of perforations and a third set of perforations.

In another aspect, a method of distributing exhaust flow in an engine exhaust aftertreatment component is provided. The engine exhaust aftertreatment component includes a housing defining an exhaust flow from an exhaust inlet to an exhaust outlet, and an exhaust aftertreatment substrate positioned within the housing between the exhaust inlet and the exhaust outlet. The exhaust aftertreatment substrate has an upstream face, which includes an inner region surrounded by an outer region. A flow distributor is positioned in the housing upstream from the exhaust aftertreatment substrate. The method includes a step of dividing the exhaust flow into a first portion and a second portion using the flow distributor. The first portion is directed toward the inner region of the upstream face of the exhaust aftertreatment substrate through a first set of perforations, and the second portion is directed toward the outer region of the upstream face of the exhaust aftertreatment substrate serially through a second set of perforations and a third set of perforations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of an engine system including a plurality of exhaust aftertreatment components, according to the present disclosure;

FIG. 2 is a sectioned perspective view of an exemplary embodiment of an engine exhaust aftertreatment component having a flow distributor positioned therein, according to one aspect of the present disclosure;

FIG. 3 is a front view of an upstream face of an exhaust aftertreatment substrate of the engine exhaust aftertreatment component of FIG. 2;

FIG. 4 is a front view of the engine exhaust aftertreatment component of FIG. 2;

FIG. 5 is a cross sectional view taken along lines 5-5 of FIG. 4;

FIG. 6 is a perspective view of portions of the flow distributor of FIGS. 2 and 5, according to another aspect of the present disclosure; and

FIG. 7 is another perspective view of portions of the flow distributor of FIGS. 2 and 5, according to another aspect of the present disclosure.

 DETAILED DESCRIPTION

Referring to FIG. 1, there is shown a schematic view of an engine system 10, according to the present disclosure. The engine system 10 may include an internal combustion engine 12, which, for purposes of illustration, and not limitation, may be that of a four-stroke, compression ignition engine and may include an engine block 14 defining a plurality of combustion chambers or cylinders 16. The internal combustion engine 12 may be any type of engine (e.g., internal combustion, gas, diesel, gaseous fuel, natural gas, propane, etc.), may be of any size, with any number of cylinders, any type of combustion chamber (e.g., cylindrical, rotary spark ignition, compression ignition, 4-stroke and 2-stroke, etc.), and in any configuration (e.g., “V,” in-line, radial, etc.). In the exemplary internal combustion engine 12, six combustion chambers 16 are shown, however, those skilled in the art will appreciate that any number of combustion chambers may be applicable. The internal combustion engine 12 may also include an intake manifold 18 in communication with the combustion chambers 16 and capable of providing air to the internal combustion engine 12, and an exhaust manifold 20 also in communication with the combustion chambers 16 and capable of expending exhaust gas from the engine block 14.

Generally speaking, the engine system 10 may include an intake air conduit 22, or passageway, extending from an air inlet 24 to the intake manifold 18, and an exhaust conduit 26, or passageway, extending from the exhaust manifold 20 to an exhaust outlet 28. According to some embodiments, an exhaust gas recirculation (EGR) conduit 30, or passageway, may have an inlet 32 in fluid communication with the exhaust conduit 26 and an outlet 34 in fluid communication with the intake air conduit 22, and may provide a path for a portion of the exhaust expended through the exhaust conduit 26 to be rerouted to the intake manifold 18 via the intake air conduit 22. The engine system 10 may also include a turbocharger of standard design, shown generally at 40. The turbocharger 40 may include a compressor 42, disposed along the intake air conduit 22, connected to a turbine 44, disposed along the exhaust conduit 26 downstream from the inlet 32 of the EGR conduit 30, via a shaft 46. The rotation of a wheel of the compressor 42, caused by exhaust gas rotating a wheel of the turbine 44, pulls in ambient air through the intake air conduit 22 and compresses it. As should be appreciated, the ambient air may be filtered using one or more air filters 48.

The compressed, or charged, intake air may be very hot and, thus, it may be desirable to route the compressed intake air through a heat exchanger, such as an air-to-air after cooler (ATAAC) 50. The ATAAC 50 may be configured to cool the intake air in the intake air conduit 22 prior to induction into the internal combustion engine 12. The ATAAC 50 may be of standard design and may be positioned at any location along the intake air conduit 22 for receiving ambient air, which may, according to some embodiments, be pushed or drawn through the ATAAC 50 using a fan. It should be appreciated that in order to comply with environmental regulations, especially regulations regarding NOx production, it may be desirable to maintain the temperature of the air passing into the intake manifold 18 below a predetermined temperature.

The engine system 10 may also include one or more aftertreatment components disposed along the exhaust conduit 26. According to the exemplary embodiment, the engine system 10 may include a plurality of aftertreatment components. For example, the aftertreatment components may include a catalyst-based device 52. The catalyst-based device 52 may include a catalyst brick configured to convert, such as via oxidation or reduction, one or more gaseous constituents of the exhaust gas produced by the internal combustion engine 12 to a more environmentally friendly gas and/or compound to be discharged into the atmosphere. For example, the catalyst may be configured to chemically alter at least one component of the exhaust flow. Catalyst-based device 52 may be configured for one or more various types of conversion, such as, for example, selective catalytic reduction (SCR), diesel oxidation (e.g., a diesel oxidation catalyst, DOC), and/or adsorption of nitrous oxides (NOx; e.g., a NOx adsorber).

The engine system 10 may also include a particulate trap, such as, for example, a diesel particulate filter (DPF) 54. The DPF 54 may include any type of aftertreatment device configured to remove one or more types of particulate matter, such as soot and/or ash, from an exhaust flow of the internal combustion engine 12. The DPF 54 may include a filter medium configured to trap the particulate matter as the exhaust gas flows through it. The filter medium, which may be coated with a catalyst, may consist of a mesh-like material, a porous ceramic material (e.g., cordierite), or any other material and/or configuration suitable for trapping particulate matter. One or more similar aftertreatment components may be disposed along the EGR conduit 30 for a similar purpose. Regenerating means, such as well known active and/or passive regeneration means, may also be provided to periodically or continuously oxidize trapped particulate matter in the DPF 54. A regeneration system, which may also be generally referred to as an aftertreatment component, is shown generally at 56.

According to the exemplary embodiment, the engine system 10 may also include a muffler 58 for reducing the amount of noise emitted by the exhaust of the internal combustion engine 12. The muffler 58, as referenced herein, may also be referred to generally as an aftertreatment component. It should be appreciated that the engine system 10 may include any number and/or combination of aftertreatment components, such as components 52-58, for treating or otherwise affecting the exhaust, and, further, any one or more aftertreatment components may be packaged together within a common module. Although the aftertreatment components 52-58 are shown positioned downstream from the turbine 44 of the turbocharger 40, it should be appreciated that one or more of the components 52-58 may be positioned upstream from the turbine 44. Further, similar and/or additional components may be positioned along the EGR conduit 30.

Turning now to FIG. 2, an engine exhaust aftertreatment component 70, which may represent one or more of the aftertreatment components 52-58 discussed above, may be disposed along the exhaust conduit 26. The engine exhaust aftertreatment component 70 may include a housing 72, such as a cylindrical housing, oriented along a longitudinal axis A and defining an exhaust flow 74 from an exhaust inlet 76 to an exhaust outlet 78. An exhaust aftertreatment substrate 80, which may include a catalyst brick or filter medium, such as those described above, may be positioned within the housing 72 between the exhaust inlet 76 and the exhaust outlet 78. The exhaust aftertreatment substrate 80 may be secured within the housing 72 using known means and, according to the exemplary embodiment, may be secured to or positioned adjacent to an annular flange 82. The exhaust aftertreatment substrate 80 includes an upstream face 84, which, as shown in FIG. 3, has an inner region 86 surrounded by an outer region 88.

Returning to FIG. 2, a flow distributor 90 according to the present disclosure is positioned in the housing 72 upstream from the exhaust aftertreatment substrate 80. According to the exemplary embodiment, the flow distributor 90 includes a flow distribution conduit 92 oriented along the longitudinal axis A and extending from the exhaust inlet 76 toward the inner region 86. The flow distributor 90 also includes a flow distribution plate 94 oriented perpendicularly to the longitudinal axis A and positioned downstream from the flow distribution conduit 92. The flow distributor 90 is configured to divide the exhaust flow 74 into a first portion 96, which is directed toward the inner region 86 through a first set of perforations 98, and a second portion 100, which is directed toward the outer region 88 serially through a second set of perforations 102 and a third set of perforations 104. More specifically, for example, the first portion 96 is directed in an axial flow direction, which is substantially parallel to axis A, and the second portion 100 is directed first in a radial flow direction, which is substantially perpendicular to axis A, and is then directed in the axial flow direction. As shown in the exemplary embodiment, the flow distribution conduit 92 may include the second set of perforations 102, while the flow distribution plate 94 may include the first and third sets of perforations 98 and 104.

Referring now to FIGS. 3-5, exemplary dimensions of the components of the engine exhaust aftertreatment component 70 are provided. Referring specifically to FIG. 3, the upstream face 84, or outer region 88, of the exhaust aftertreatment substrate 80, which may be cylindrical in shape, may have an overall diameter d1 of approximately 275-285 millimeters (mm), while the inner region 86 may have a diameter d2 of about 120-130 mm. The upstream face 84 may also have an outer perimeter p1, or circumference, and an inner perimeter p2, which defines the inner region 86 of the exhaust aftertreatment substrate 80. Dimensions of the exhaust aftertreatment substrate 80 and upstream face 84 may vary, depending on the particular application.

Turning now to FIG. 4, a view of the inlet end of the cylindrical housing 72 illustrates an overall housing diameter d3 of about 365-375 mm. A cross section through the housing 72, as indicated at line 5-5 in FIG. 4, is shown in FIG. 5. The exhaust inlet 76 may have a diameter d4 of about 120-130 mm, while the exhaust outlet 78 may have a similar diameter d5 of about 120-130 mm. According to the exemplary embodiment, the flow distribution conduit 92 may define or extend inwardly from the exhaust inlet 76 and, thus, may have a similar diameter as the exhaust inlet 76. As such, the diameter d1 of the upstream face 84 may be about two times the diameter of the flow distribution conduit 92, which, according to the exemplary embodiment, is substantially the same as diameter d4. An annular flow guard 106, which may be a component of the flow distributor 90, may have a diameter d6 of about 275-285 mm, which substantially matches the diameter d1 of the exhaust aftertreatment substrate 80. An axial length l1 of the annular flow guard 106, which may define an axial length of the flow distributor 90, may be approximately 55-65 mm. As such, the axial length l1 of the flow distributor 90 may be less than the diameter d4 of the exhaust inlet 76.

A distance l2 between an inlet end cap 108, defining a portion of the housing 72, and the annular flange 82 supporting the exhaust aftertreatment substrate 80 is about 75-85 mm and, thus, the axial distance l3 between the flow distributor 90 or, more specifically, the flow distribution plate 94, and the upstream face 84 may be about 10-15 mm. As shown, the exhaust aftertreatment substrate 80, which may be coated in a catalyst, such as a diesel oxidation catalyst, may have an axial width or thickness tx1 of approximately 85-95 mm. As should be appreciated, the dimensions of all of the components are provided for exemplary purposes only and, according to alternative embodiments, may vary. Further, although a cylindrical configuration is shown, alternative configurations may benefit from the flow distributor 90 described herein.

Referring also to FIGS. 6 and 7, which depict views of the flow distributor 90, a perimeter p3 of an outlet opening 110 of the flow distribution conduit 92 may match the perimeter p2 of the inner region 86 of the upstream face 84, while a perimeter p4 of the flow distribution plate 94 may match the perimeter p1 of the upstream face 84 or, more particularly, the outer region 88 of the upstream face 84. Additionally, and/or alternatively, a perimeter p5 defined by a tangent to a peripheral set of perforations 112 of the third set of perforations 104 may match the perimeter p1 of the upstream face 84. As used herein, “matching” means to substantially correspond to, such that, for example, one perimeter may be the same as another perimeter or may be within an acceptable range.

The flow distribution conduit 92 may include the second set of perforations 102, which may open through walls defining the conduit 92 along the length of the conduit 92 between the inlet end cap 108 and the outlet opening 110. The second set of perforations 102 may be dimensioned and arranged to provide a preferred total flow area. In particular, a sum of the second set of perforations 102 may define a total flow area, or percent open area, of between about 40% and 60%. According to a specific embodiment, the second set of perforations 102 may provide or define a 50% total flow area. The first set of perforations 98, which may open through the flow distribution plate 94 within a region defined by the perimeter p3, and the third set of perforations 104, which may open through the plate 94 within a region between the perimeters p3 and p4, may also be dimensioned and arranged to provide a preferred total flow area. According to some embodiments, a sum of the first set of perforations 98 may define a 10-30% total flow area, while a sum of the third set of perforations 104 may define a 20-40% total flow area. According to a specific embodiment, the first set of perforations 98 may provide a 20% open area, while the third set of perforations 104 may provide a 30% open area.

Preferably, the total flow area defined by the sum of the second set of perforations 102 is greater than the total flow area defined by the sum of the first set of perforations 98. Further, the total flow area defined by the sum of the second set of perforations 102 may preferably be greater than the total flow area defined by the sum of the third set of perforations 104. The number, size, and arrangement of the perforations of each of the sets of perforations 98, 102, and 104 is preferably selected such that the flow distributor 90 provides a flow rate per unit area at the inner region 86 that is of the same order of magnitude of a flow rate per unit area at the outer region 88. Preferably, according to flow distribution results at or near the upstream face 84 of the exhaust aftertreatment substrate 80, the flow rates per unit area at the inner and outer regions 86 and 88 are substantially similar.

INDUSTRIAL APPLICABILITY

The present disclosure may be applicable to machines and/or engine systems having an engine exhaust aftertreatment component. Further, the present disclosure may be applicable to engine systems having an engine exhaust aftertreatment component that includes an exhaust aftertreatment substrate. Yet further, the present disclosure may be applicable to means for evenly distributing exhaust flow across an upstream face of the exhaust aftertreatment substrate.

Referring generally to FIGS. 1-7, an engine system 10 may include an internal combustion engine 12 having an engine block 14 defining a plurality of combustion chambers or cylinders 16. An intake system may generally include an intake air conduit 22 extending from an air inlet 24 to an intake manifold 18, with an air filter 48, compressor 42 of a turbocharger 40, and ATAAC 50 disposed along the conduit 22. The engine system 10 may be configured to route exhaust gases produced by the internal combustion engine 12 away from the engine 12 via the exhaust conduit 26, which may be configured to direct the exhaust flow from the internal combustion engine 12 through the turbine 44 of the turbocharger 40, through aftertreatment components 52-58, and ultimately release the exhaust flow to the atmosphere through the exhaust outlet 28.

During engine manufacture, or at any point thereafter, it may be desirable to install a flow distributor 90 in one of the aftertreatment components 52-58 and/or provide aftertreament components, such as exemplary component 70, preconstructed with a flow distributor 90, as described herein. During engine operation, exhaust 74 enters the aftertreatment component 70 through the exhaust inlet 76 and travels through the flow distribution conduit 92 of the flow distributor 90. The exhaust flow 74 is then divided by the flow distributor 90 into first and second portions 96 and 100, respectively. The first portion 96 is directed toward the inner region 86 of the upstream face 84 of the exhaust aftertreatment substrate 80 through the first set of perforations 98, and the second portion 100 is directed toward the outer region 88 of the upstream face 84 of the exhaust aftertreatment component 70 serially through the second set of perforations 102 and the third set of perforations 104.

In particular, the first portion 96 is directed axially through the flow distribution conduit 92 and through the first set of perforations 98 of the flow distribution plate 94. The second portion 100 is directed axially into the flow distribution conduit 92, radially through the second set of perforations 102 of the flow distribution conduit 92, and is then directed axially through the third set of perforations 104 of the flow distribution plate 94. As should be appreciated, the second portion 100 may be re-directed from the radial flow direction to the axial flow direction in the area defined by the inlet end cap 108 and the annular flow guard 106. The total flow area provided by each of the sets of perforations 98, 102, and 104 is selected to ultimately achieve a flow rate per unit area at the inner region 86 that is about the same as the flow rate per unit area at the outer region 88. The first and second portions 96 and 100 of the exhaust flow 74 are then passed through the exhaust aftertreatment substrate 80, which, as stated, above, may include a catalyst coating.

The flow distributor described herein provides a compact means for distributing exhaust flow evenly across the upstream face of the exhaust aftertreatment substrate. As such, the exhaust aftertreatment substrate may be more effectively utilized and may have an extended useful life. In addition, the size of the engine exhaust aftertreatment component and, thus, the footprint required by the exhaust aftertreatment system, may be reduced.

It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will appreciate that other aspects of the disclosure can be obtained from a study of the drawings, the disclosure and the appended claims.

Claims

1. An engine exhaust aftertreatment component, comprising:

a housing defining an exhaust flow from an exhaust inlet to an exhaust outlet;
an exhaust aftertreatment substrate positioned within the housing between the exhaust inlet and the exhaust outlet and having an upstream face, wherein the upstream face includes an inner region surrounded by an outer region; and
a flow distributor positioned in the housing upstream from the exhaust aftertreatment substrate, wherein the flow distributor divides the exhaust flow into a first portion directed toward the inner region through a first set of perforations and a second portion directed toward the outer region serially through a second set of perforations and a third set of perforations.

2. The engine exhaust aftertreatment component of claim 1, wherein the flow distributor includes:

a flow distribution conduit oriented along a longitudinal axis of the housing, extending from the exhaust inlet toward the inner region, and including the second set of perforations; and
a flow distribution plate oriented perpendicularly to the longitudinal axis and including the first and third sets of perforations.

3. The engine exhaust aftertreatment component of claim 2, wherein the first and third sets of perforations define an axial flow direction, and the second set of perforations define a radial flow direction.

4. The engine exhaust aftertreatment component of claim 2, wherein a flow rate per unit area at the inner region is of a same order of magnitude of a flow rate per unit area at the outer region.

5. The engine exhaust aftertreatment component of claim 4, wherein a total flow area defined by a sum of the second set of perforations is greater than a total flow area defined by a sum of the first set of perforations.

6. The engine exhaust aftertreatment component of claim 5, wherein the total flow area defined by the sum of the second set of perforations is greater than a total flow area defined by a sum of the third set of perforations.

7. The engine exhaust aftertreatment component of claim 4, wherein a perimeter of an outlet opening of the flow distribution conduit matches a perimeter of the inner region.

8. The engine exhaust aftertreatment component of claim 7, wherein a perimeter defined by a tangent to a peripheral set of perforations of the third set of perforations matches a perimeter of the upstream face.

9. The engine exhaust aftertreatment component of claim 4, wherein an axial length of the flow distributor is less than a diameter of the exhaust inlet.

10. The engine exhaust aftertreatment component of claim 9, wherein a diameter of the upstream face is about two times a diameter of the flow distribution conduit.

11. The engine exhaust aftertreatment component of claim 2, wherein the exhaust aftertreatment substrate is coated in a diesel oxidation catalyst.

12. A method of distributing exhaust flow in an engine exhaust aftertreatment component, the engine exhaust aftertreatment component including a housing defining an exhaust flow from an exhaust inlet to an exhaust outlet, an exhaust aftertreatment substrate positioned within the housing between the exhaust inlet and the exhaust outlet and having an upstream face, wherein the upstream face includes an inner region surrounded by an outer region, and a flow distributor positioned in the housing upstream from the exhaust aftertreatment substrate, the method comprising:

dividing the exhaust flow into a first portion and a second portion using the flow distributor;
directing the first portion toward the inner region of the upstream face of the exhaust aftertreatment substrate through a first set of perforations; and
directing the second portion toward the outer region of the upstream face of the exhaust aftertreatment substrate serially through a second set of perforations and a third set of perforations.

13. The method of claim 12, further including directing the first portion through a flow distribution conduit of the flow distributor and through the first set of perforations of a flow distribution plate of the flow distributor.

14. The method of claim 13, further including directing the second portion into the flow distribution conduit, through the second set of perforations of the flow distribution conduit, and through the third set of perforations of the flow distribution plate.

15. The method of claim 14, wherein directing the first portion through the first set of perforations and directing the second portion through the third set of perforations includes directing the first and second portions in an axial flow direction; and wherein directing the second portion through the second set of perforations includes directing the second portion in a radial flow direction.

16. The method of claim 13, further including providing a flow rate per unit area at the inner region that is a same order of magnitude of a flow rate per unit area at the outer region.

17. The method of claim 16, further including dimensioning and arranging the first and second sets of perforations such that a total flow area defined by a sum of the second set of perforations is greater than a total flow area defined by a sum of the first set of perforations.

18. The method of claim 17, further including dimensioning and arranging the second and third sets of perforations such that a total flow area defined by the sum of the second set of perforations is greater than a total flow area defined by a sum of the third set of perforations.

19. The method of claim 12, further including performing the dividing and directing steps along an axial length of the flow distributor that is less than a diameter of the exhaust inlet.

20. The method of claim 12, further including directing the first and second portions through the exhaust aftertreatment substrate having a diesel oxidation catalyst coating.

Patent History
Publication number: 20130333352
Type: Application
Filed: Jun 19, 2012
Publication Date: Dec 19, 2013
Applicant: CATERPILLAR INC. (Peoria, IL)
Inventor: Rajdeep S. Pradhan (Edwards, IL)
Application Number: 13/526,910
Classifications
Current U.S. Class: Anti-pollution (60/274); Divider, Collector, Valve Means, Or Boundary Layer Device Controlling Exhaust Gas Flow (60/324)
International Classification: F01N 3/28 (20060101);