Dosing and mixing arrangement for use in exhaust aftertreatment

Description of equivalent WO 2015038897 A1

DOSING AND MIXING ARRANGEMENT FOR USE IN EXHAUST AFTERTREATMENT

0002CROSS-REFERENCE TO RELATED APPLICATION^)

0003This application is being filed on September 12, 2014, as a PCT International Patent application and claims priority to U.S. Patent Application Serial No. 61/877,749 filed on September 13, 2013, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

0005Vehicles equipped with internal combustion engines (e.g., diesel engines) typically include exhaust systems that have aftertreatment components such as selective catalytic reduction (SCR) catalyst devices, lean NOx catalyst devices, or lean NOx trap devices to reduce the amount of undesirable gases, such as nitrogen oxides (NOx) in the exhaust. In order for these types of aftertreatment devices to work properly, a doser injects reactants, such as urea, ammonia, or hydrocarbons, into the exhaust gas. As the exhaust gas and reactants flow through the aftertreatment device, the exhaust gas and reactants convert the undesirable gases, such as NOx, into more acceptable gases, such as nitrogen and water. However, the efficiency of the aftertreatment system depends upon how evenly the reactants are mixed with the exhaust gases. Therefore, there is a need for a flow device that provides a uniform mixture of exhaust gases and reactants.

0006SCR exhaust treatment devices focus on the reduction of nitrogen oxides.

0007In SCR systems, a reductant (e.g., aqueous urea solution) is dosed into the exhaust stream. The reductant reacts with nitrogen oxides while passing through an SCR substrate to reduce the nitrogen oxides to nitrogen and water. When aqueous urea is used as a reductant, the aqueous urea is converted to ammonia which in turn reacts with the nitrogen oxides to covert the nitrogen oxides to nitrogen and water. Dosing, mixing and evaporation of aqueous urea solution can be challenging because the urea and by-products from the reaction of urea io ammonia can form deposits on the surfaces of the

0008aftertreatment devices. Such deposits can accumulate over time and partially block or otherwise disturb effective exhaust flow through the aftertreatment device. An aspect of the present disclosure relates to a method for dosing and mixing exhaust gas in exhaust aftertreatment. Another aspect of the present disclosure relates to a dosing and mixing unit for use in exhaust aftertreatment More specifically, the present disclosure relates to a dosing and mixing unit including a mixing tube configured to direct exhaust gas flow to flow around and through the mixing tube to effectively mix and dose exhaust gas within a relatively small area.

0009In accordance with some aspects, the mixing tube includes a slotted region and a non-slotted region. In examples, the slotted region extends over a majority of a circumference of the mixing tube. In examples, the slotted region extends over a majority of an axial length of the mixing tube. In examples, a circ mferential width of the non- slotted region is substantially larger than a circumferential width of a gap between slots of the slotted region.

0010In accordance with some aspects, the mixing tube includes a louvered region and a non- louvered region. The louvered region extends o ver a majority of a circumference of the mixing tube. In examples, the louvered region extends over a majority of an axial length of the mixing tube. In examples, a circumferential width of the non-slotted region is substantially larger than a circumferential width of a gap between louvers of the louvered region.

0011In accordance with some aspects, the mixing tube is offset within a mixing region of a housing. For example, the mixing tube can be located closer to one wall of the housing than to an opposite wall of the housing.

0012A variety of additional aspects will be set forth in the description that follows. These aspects can relate to individual features and to combinations of features. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictiv e of the broad concepts upon which the embodiments disclosed herein are based.

DRAWINGS

0014The accompanying drawings, which are incorporated in and constitute part of the description, illustrate several aspects of the present disclosure. A brief description of the drawings is as follows: FIG. 1 is a schematic representation of a first exhaust treatment system incorporating a doser and mixing unit in accordance with the principles of the present disclosure;

0015FIG. 2 is a schematic representation of a second exhaust treatment system incorporating a doser and mixing unit in accordance with the principles of the present disclosure;

0016FIG. 3 is a schematic representation of a third exhaust treatment system incorporating a doser and mixing unit in accordance with the principles of the present disclosure;

0017FIG. 4 is a perspective view of an example doser and mixing unit configured in accordance with the principles of the present disclosure;

0018FIG. 5 is a cross-sectional view of the doser and mixing unit of FIG. 4 taken along the plane 5 of FIG. 4;

0019FIG. 6 is a cross-sectional view of the doser and mixing unit of FIG. 4 taken along the housing axis C shown in FIG. 5:

0020FIG. 7 is a perspective vie w of an example mixing tube arrangement suitable for use with the doser and mixing unit of FIG. 4;

0021FIG. 8 is a side elevational view of the mixing tube arrangement of FIG. 7; and

0022FIG, 9 is an end vie of the mixing tube arrangement of FIG. 7.

DETAILED DESCRIPTION

0024Reference will now be made in detail to the exemplary aspects of the present disclosure that are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like structure.

0025FIGS. 1-3 illustrate various exhaust flow treatment systems including an internal combustion engine 201 and a. dosing and mixing unit 207. FIG. 1 shows a first treatment system 200 in which a pipe 202 carries exhaust from the engine 201 to the dosing and mixing unit 207, where reactant (e.g., aqueous urea) is injected (at 206) into the exhaust stream and mixed with the exhaust stream, A pipe 208 carries the exhaust stream containing the reactant from the dosing and mixing unit 207 to a treatment substrate (e.g., an SCR device) 209 where nitrogen oxides are reduced to nitrogen and water.

0026FIG. 2 shows an alternative system 220 that is substantially similar to the system 200 of FIG. 1 except that a separate aftertreatment substrate 203 (e.g., a Diesel Particulate Filter (DPF) or Diesel Oxidation Catalyst (DOC)) is positioned between the engine 201 and the dosing and mixing unit 207. The pipe 202 carries the exhaust stream from the engine 201 to the aftertreatment substrate 203 and another pipe 204 carries the treated exhaust stream to the dosing and mixing device 207. FIG. 3 shows an alternative system 240 ihai is substantially similar to the system 220 of FIG. 2 except that the aftertreatment device 203 is combined with the dosing and mixing unit 2.07 as a single unit 205.

0027A selective catalytic reduction (SCR) catalyst device is typically used in an exhaust system to remove undesirable gases such as nitrogen oxides (NOx) from the vehicle's emissions. SCR's are capable of converting NOx to nitrogen and oxygen in an oxygen rich environment with the assistance of reactants such as urea or ammonia, which are injected into the exhaust stream upstream of the SCR through a doser. In alternati v e implementations, other aftertreatment devices such as lean NOx catalyst devices or lean NOx traps could be used in place of the SCR catalyst device, and other reactants (e.g., hydrocarbons) can be dispensed by the doser.

0028A lean NOx catalyst de vice is also capable of converting NOx to nitrogen and oxygen. In contrast to SCR's, lean NOx catalysts use hydrocarbons as reducing agents/reactants for conversion of NOx to nitrogen and oxygen. The hydrocarbon is injected into the exhaust stream upstream of the lean NOx catalyst. At the lean NOx catalyst, the NOx reacts with the injected hydrocarbons with the assistance of a catalyst to reduce the NOx to nitrogen and oxygen. While the exhaust treatment systems 200, 220, 240 are described as including an SCR, it will be understood that the scope of the present disclosure is not limited to an SCR as there are various catalyst devices (a lean NOx catalyst substrate, a SCR substrate, a SCRF substrate (i.e., a SCR coating on a particulate filter), and a NOx trap substrate) that can be used in accordance with the principles of the present disclosure.

0029The lean NOx traps use a material such as barium oxide to absorb NOx during lean burn operating conditions. During fuel rich operations, the NOx is desorbed and converted to nitrogen and oxygen by reaction with hydrocarbons in the presence of catalysts (precious metals) within the traps. FIGS. 4-6 show a dosing and mixing unit 100 suitable for use as dosing and mixing unit 207 in the treatment systems disclosed above. The dosing and mixing unit 100 includes a housing 102 having an interior 104 accessible through an inlet 101 and an outlet 109, A mixing tube arrangement 1 10 is disposed within the interior 104 (see FIGS. 5 and 6). With reference to the treatment systems 200, 220, 240, the inlet 101 receives exhaust flow from the engine 201 (or the treatment substrate 203) and the outlet 109 leads to the SCR 209. In certain implementations, the treatment substrate 203 also can be disposed within the housing 102 to form the combined unit 205 of FIG. 3.

0030As shown in FIG. 5, the housing 102 extends from a first end 105 to a second end 106 along a housing axis C. In an example, the housing axis C (i.e., an inlet axis) defines a flow axis for the inlet 101. The housing 102 also extends from a third end 107 to a fourth end 108 along a longitudinal axis L (i.e., outlet axis) of the mixing tube arrangement 1 10. In certain implementations, the housing axis C is not centered between the third and fourth ends 107, 108. In an example, the housing axis C is located closer to the third end 107. In certain implementations, the longitudinal axis L is not centered between the first and second ends 105, 106. In an example, the longitudinal axis L is located closer to the second end 106.

0031In an example, the longitudinal axis L defines a flow axis for the outlet 109. In certain implementations, the second end 106 is closed. In certain implementations, the second end 106 is curved to define a. contoured interior surface 122. In an example, the second end 106 defines half of a cylindrical shape. In certain implementations, the third end 107 defines a port 140 at which a doser can be coupled (see FIG. 4). In other implementations, a doser can be disposed within the housing 102 at the third end 107.

0032As shown in FIG. 6, the housing 102 also has a first side 123 and a second side 124 that extend between the first and second ends 105, 106 and between the third and fourth ends 107, 108. In certain implementations, the first and second sides 123, 124 are closed. The closed second end 106 contours between the first and second sides 123, 124 (see FIG. 6). As shown in FIG. 6, the interior 104 of the housing 102 defines an inlet region 120 having a first volume and a mixing region 121 having a second, larger volume. The mixing region 121 extends from the inlet region 120 to the second end 106 of the housing 102. The mixing tube arrangement 1 10 is disposed within the mixing region 12.1.

0033As shown in FIG. 6, exhaust gas G flows from the inlet 101 towards the second end 106 of the housing 102. As the exhaust gas G approaches the mixing tube arrangement 1 10, some of the exhaust gas G begins to swirl within the housing interior 104. The mixing tube arrangement 1 10 causes the exhaust gas G to swirl about the longitudinal axis L (FIG. 5) of the mixing tube arrangement 1 10. In certain

0034implementations, the mixing tube arrangement 1 10 defines slots 1 13 (which will be discussed in more detail below) through which the exhaust gas G enters the mixing tube arrangement 1 10. In certain implementations, the mixing tube arrangement 1 10 includes louvers 1 14 (which will be discussed in more detail below) that direct the exhaust gas G through the slots 1 13 in a swirling flow along a first circumferential direction Dl (FIG. 6).

0035A doser (or doser por t ) is disposed at one end of the mixing tube arrangement 1 10 (see FIG. 5). The doser is configured to inject reactant (e.g., aqueous urea) into the swirling flow G. Examples of the reactant include, but are not limited to, ammonia, urea, or a hydrocarbon. The doser can be aligned with the longitudinal axis L of the mixing tube arrangement 1 10 so as to generate a spray pattern concentric about the axis L. In other embodiments, the reactant doser may be positioned upstream from the mixing tube arrangement 1 10 or downstream from the mixing tube arrangement 1 10. The opposi te end of the mixing tube arrangement 1 10 defines the outlet 109 of the unit 100. Accordingly, the reactant and exhaust gas mixture is directed in a swirling flow out through the outlet 109 of the housing 102.

0036In other implementations, the dosing and mixing unit 100 can be used to mix hydrocarbons with the exhaust to reactivate a diesel particulate filter (DPF). In such implementations, the reactant doser injects hydrocarbons into the gas flow within the mixing tube arrangement 1 10. The mixed gas leaves the mixing tube arrangement 110 and is directed to a downstream diesel oxidation catalyst (DOC) at which the hydrocarbons ignite to heat the exhaust gas. The heated gas is then directed to the DPF to burn particulate clogging the filter.

0037In some implementations, the mixing tube arrangement 1 10 is offset within the mixing region 121. For example, the mixing tube arrangement 1 10 can be disposed so that a cross- sectional area of the annuius is decreasing as the flo travels along a perimeter of the mixing tube arrangement 1 10. In the example shown, the mixing tube arrangement is located closer to the second side 124 than to the first side 123. In other implementations, however, the mixing tube arrangement 1 10 can be located closer to the first side 123. In some implementations, offsetting the mixing tube arrangement 1 10 guides the exhaust flow in the first circumferential direction Dl . In some

0038implementations, offsetting the mixing tube arrangement 1 10 inhibits exhaust gases G from flowing in an opposite circumferential direction. For example, offsetting the mixing tube arrangement may create a high pressure zone 125 and a flow zone 126, The high pressure zone 125 is defined where the mixing tube arrangement 1 1 0 approaches the closest side (e.g., the second side 124). As the exterior surface of the mixing tube arrangement 1 10 approaches the housing side 124, less flow can pass between the mixing tube arrangement 1 10 and the side 124.

0039Accordingly, the flow pressure builds and directs the exhaust gases away from the high pressure zone 125. The flow zone 126 is defined along the portions of the mixing tube 1 10 that are spaced farther from the wall (e.g., side wall 123, interior surface 122), thereby enabling flow between the mixing tube arrangement 1 10 and the wail.

0040In certain implementations, a portion of the mixing tube arrangement 1 1 0 contacts the closest side wall (e.g., side wall 124), For example, a distal end of a louver 1 14 (see FIGS. 7-9) of the mixing tube arrangement 1 10 may contact (see 128 of FIG. 6) the closest side wall 124. In such implementations, the contact 128 between the mixing tube arrangement 1 10 and the wail 124 further inhibits (or blocks) flow in the opposite circumferential direction.

0041FIGS. 7-9 illustrate one example mixing tube arrangement 1 10 including a tube body 1 1 1 defining a hollow interior 1 12. The tube body 1 1 1 has a length LI . The tube body 1 1 1 has a slotted region 1 1 5 extending over a portion of the tube body H I . One or more slots 1 13 are defined through a circumferential sui'face of the tube body 1 1 1 at the slotted region 1 15. The slots 1 13 lead from an exterior of the tube body 1 1 1 into the interior 1 12. of the tube body 1 1 1. In some implementations, the slots 1 13 include axially- ex tending slots 1 13. In certain implementations, the tube body i l l defines no more than one axial slot 1 13 per radial position along the circumference of the tube body 1 1 1 , In certain implementations, the slotted region 1 15 includes portions of the tube body 1 1 1 extending circumferentially between the slots 1 13 in the slotted region 1 15.

0042In some implementations, the slotted region 1 15 defines multiple slots 1 13. In certain implementations, the slotted region 1 15 defines between five slots 1 13 and twenty-five slots 1 13. In certain implementations, the slotted region 1 15 defines between ten slots 1 13 and twenty slots 1 13, In an example, the slotted region 1 15 defines about fifteen slots 1 13. In an example, the slotted region 1 15 defines about fourteen slots 1 13. In an example, the slotted region 1 15 defines about sixteen slots 1 13. In an example, the slotted region 1 15 defines about twelve slots 1 13, In other implementations, the slotted region 1 15 can define any desired number of slots 1 13. As shown in FIG. 8, the slotted region 1 15 of the tube body 1 1 1 has a length L2 that is generally shorter than the length LI of the tube body 1 1 1. In some implementations, the length L2 of the axial region 115 is shorter than the length LI of the tube body 11 1. In certain implementations, the length L2 extends along a majority of the length LI. In certain implementations, the length L2 is at least half of the length LI . In certain implementations, the length L2 is at least 60% of the length LI . In certain implementations, the length L2 is at least 70% of the length LI . In certain

0043implementations, the length L2 is at least 75% of the length LI . In some implementations, each slot 113 extends the entire length L2 of the axial region 1 15. In other

0044implementations, each slot 1 13 extends along a portion of the axial region 1 15.

0045In some implementations, a ratio of the length L2 of the slotted region 115 to a tube diameter D (FIG. 9) is about 1 to about 3. In certain implementations, the ratio of the length L2. of the slotted region 115 to the tube diameter D is about 1.5 to about 2. In certain examples, the ratio of the length L2 of the slotted region 1 15 to the tube diameter D is about 1.75. In certain examples, the tube diameter D is about 5 inches and the length L2 of the slotted region 1 15 is a bout 8 inches. In an example, each slot 1 13 of the slotted region 1 15 extends the length L2. of the slotted region 1 15.

0046As shown in FIG. 9, the slotted region 1 15 of the tube body 1 1 1 has a circumferential width Si that is larger than a circumferential width S2 of a non-slotted region i 16 of the tube body i l l . The non-slotted region 1 16 defines a circumferential surface of the tube body 1 1 1 through which no slots are defined. In an example, the non- slotted region 1 16 defines a solid circumferential surface through which no openings are defined.

0047In some implementations, the circumferential width S2 of the non-slotted region 116 is significantly larger than a circumferential width of any portion of the tube body 1 1 1 extending between two adjacent slots 1 13 at the slotted region 1 15. For example, in certain examples, the circumferential width S2 of the non-slotted region 1 16 is at least double the circumferential width of any portion of the tube body 1 1 1 extending between two adjacent slots 1 13 at the slotted region 115. In certain examples, the circumferential width S2 of the non-slotted region 1 16 is at least triple the circumferential width of any portion of the tube body 11 1 extending between two adjacent slots 1 13 at the slotted region 1 15. In certain examples, the circumferential width S2 of the on-slotted region 1 16 is at least four times the circumferential width of any portion of the tube body 1 1 1 extending between two adjacent slots 1 13 at the slotted region 1 15. In certain examples, the circumferential width S2 of the non-slotted region 1 16 is at least five times the circumferential width of any portion of the tube body 11 1 extending between two adjacent slots 1 13 at the slotted region 1 15.

0048In some implementations, the circumferential width SI of the slotted region 1 15 is substantially larger than the circumferential width S2 of the non-slotted region 1 16. In certain implementations, the circumferential width SI of the slotted region 1 15 is at least twice the circumferential width S2. of the non-slotted region 1 16. In certain implementations, the circumferential width S i of the slotted region 1 15 is about triple the circumferential width S2 of the non-slotted region 1 16.

0049In some examples, the slotted region 1 15 extends about 2.00° to about 350° around the tube body 1 1 1 and the non-slotted region 1 16 extends about 10° to about 160° around the tube body i l l . In certain examples, the slotted region 1 15 extends about 210° to about 330° around the tube body 11 1 and the non-slotted region 1 16 extends about 30° to about 150° around the tube body 1 1 1. In an example, the slotted region 1 15 extends about 270° around the tube body 1 1 1 and the non-slotted region 1 16 extends about 90° around the tube body 1 1 1. In an example, the slotted region 1 15 extends about 300° around the tube body 1 1 1 and the non-slotted region 1 16 extends about 60° around the tube body H I . In an example, the slotted region 1 15 extends about 240° around the tube body 1 1 1 and the non-slotted region 116 extends about 120° around the tube body 1 1 1.

0050In some implementations, each slot 1 13 has a common width S3 (defined along the circumference of the tube body 1 1 1 . In some implementations, the width S3 of each slot 113 is less than the circumferential width S2 of the non-slotted region 1 16. In certain implementations, the width S3 of each slot 1 13 is substantially less than the width S 2 of the non-slotted region 1 16. In certain implementations, the width S3 of each slot 1 13 is less than half the width S2 of the non-slotted region 116. In certain

0051implementations, the width S3 of each slot 1 13 is less than a third of the width S2 of the non-slotted region 1 16. In certain implementations, the width S3 of each slot 1 13 is less than a quarter of the width S2 of the non-slotted region 1 16. In certain implementations, the width S3 of each slot 1 13 is less than 20% the width S2 of the non-slotted region 1 16. In certain implementations, the width S3 of each slot 1 13 is less than 10% the width S2 of the non-slotted region 1 16.

0052In some implementations, the tube body 1 1 1 has a ratio of slot width S3 to tube diameter D (FIG. 9) of about 0.02 to about 0.2. In certain implementations, the ratio of slot width S3 to tube diameter D is about 0.05 to about 0.15. In certain implementations, the ratio of slot width S3 to tube diameter D is about 0.08 to about 0.12. In an example, the ratio of slot width S3 to tube diameter D is about 0.1. In certain examples, the slot width S3 is about 0.45 inches and the tube diameter D is about 5 inches. In other implementations, however, the slots 113 can have different widths.

0053In some implementations, the slots 1 13 are spaced evenly around the circumferential width SI of the slotted region 1 15. In such implementations, gaps between adjacent slots 1 13 within the slotted region 1 15 have a circumferential width S4. In certain implementations, the circumferential width S4 of the gaps is larger than the circumferential width S3 of the slots 1 13. In certain implementations, the circumferential width S3 of the slots 1 13 is at least half of the circumferential width S4 of the gaps. In certain implementations, the circumferential width S3 of the slots 1 13 is at least 60% of the circumferential width S4 of the gaps. In certain implementations, the circiEmferential width S3 of the slots 1 13 is at least 75% of the circumferential width S4 of the gaps. In certain implementations, the circumferential width S3 of the slots 1 13 is at l east 85% of the circumferential width S4 of the gaps. In other implementations, however, the gaps between the slots 1 13 can have different widths.

0054In some implementations, the width S4 of each gap is less than the circumferential width 82 of the non-slotted region 1 16. In certain implementations, the width S4 of each gap is substantially less than the width S2 of the non-slotted region 1 16. In certain implementations, the w idth S4 of each gap is less tha n half the w idth S2 of the non-slotted region 1 16. In certain implementations, the width S4 of each gap is less than a third of the width 82 of the non-slotted region 1 16. In certain implementations, the width S4 of each gap is less than a quarter of the width 82 of the non-slotted region 1 16. In certain implementations, the width S4 of each gap is less than 2.0% the width S2. of the non-slotted region 1 16. In certain implementations, the width S4 of each gap is less than 10% the width 82 of the non-slotted region 1 16.

0055In certain implementations, the slots 1 13 occupy about 25% to about 60% of the area of the slotted region 1 15. In certain implementations, the slots 1 13 occupy about 35% to about 55% of the area of the slotted region 1 15. In certain implementations, the slots 1 13 occupy less than about 50% of the area of the slotted region 1 15. In certain implementations, the slots 1 13 occupy about 45% of the area of the slotted region 1 15. In other words, the percentage of open area to closed area at the slotted region 1 15 is about 45%. In some implementations, louvers 1 14 are disposed at the slotted region 1 15. In some implementations, each slot 1 13 has a corresponding louver 1 14. In other implementations, however, only a portion of the slots 1 13 have a corresponding louver 1 14. In some implementations, each louver 1 14 extends the length of the corresponding slot 113. In other implementations, a louver 1 14 can be longer or shorter than the corresponding slot 113.

0056As shown in FIG. 9, each louver 1 14 extends from a base 1 18 to a distal end 119 spaced from the tube body 1 1 1. In some impiementations, the base 1 18 is coupled to the tube body 1 1 1. In other implementations, however, the base 1 18 can be spaced from the tube body 1 1 1 (e.g., suspended adjacent the tube body 1 11). In some implementations, the base 11 8 of each louver 1 14 is disposed at one end of a slot 1 13 so that the louver 1 14 extends at least partially over the slot 1 13 (e.g., see FIG. 9). In certain implementations, the louver 1 14 is sized to extend fully across the width S3 of the slot 1 13. In other implementations, the louver 1 14 extends only partially across the width S3 of the slot 1 13. In some implementations, the distal ends 1 19 of adjacent louvers 1 14 define gaps having a circumferential width 85. In certain implementations, the circumferential width S5 of the gaps is about equal to the circumferential width S3 of the slots 1 13 and the circumferential width 84 of the gaps.

0057In some implementations, each louver 1 14 extends straight from the slot 1 13 to define a plane. In certain implementations, the louvers 1 14 extend from the slot 1 13 at an angle Θ relative to the tube body 1 1 1. In certain implementations, the angle Θ is about 20° to about 70°. In an example, the angle Θ is about 45°. In an example, the angle Θ is about 40°. In an example, the angle Θ is about 50°. In an example, the angle Θ is about 35°. In certain implementations, the angle Θ is about 30° to about 55°. In other implementations, each louver 1 14 defines a concave curve as the louver 114 extends away from the slot 1 13.

0058In some implementations, the tube body i l l has a louvered region over which the louvers 1 14 extend and a non-louvered region over which no louver extends. In some such implementations, the louvered region extends about 200° to about 350° around the tube body 1 1 1 and the non-louvered region extends about 10° to about 160° around the tube body 11 1. In certain examples, the louvered region extends about 210° to about 330° around the tube body 1 1 1 and the non-louvered region extends about 30° to about 150° around the tube body 1 1 1 , in an example, the louvered region extends about 270° around the tube body 1 i 1 and the non-louvered region extends about 90° around the tube body 1 1 1. In certain examples, the louvered region largely corresponds with the slotted region 1 15. In an example, the louvered region overlaps the slotted region 1 15.

0059Various modifications and alterations of this disclosure will become apparent to those skilled in the art without departing from the scope and spirit of this disclosure, and it should be understood ihat the scope of ihis disclosure is not to be unduly limited to the illustrative embodiments set forth herein.