Exhaust duct with flow regulation section

Abstract

An exhaust duct has: a wall having an inner surface that at least partially defines a flow channel; a first fin positioned within the flow channel and attached to the inner surface; and a second fin positioned within the flow channel and attached to the inner surface such that the first fin and the second fin are spaced apart. A support strip is attached to the inner surface, to the first fin at a first location spaced apart from the inner surface, and to the second fin at a second location spaced apart from the inner surface.

Description

[0001] This application is a divisional application of the National Application filed on December 18, 2018, with application number 201811553103.5 and entitled "Exhaust duct with flow regulation section". Technical Field

[0002] The present invention generally relates to exhaust ducts, and more specifically to exhaust ducts having a flow regulating portion. Background Technology

[0003] Many engine systems include exhaust aftertreatment systems for treating exhaust gases leaving the engine. Exhaust aftertreatment systems can include various components and subsystems for treating exhaust gases, such as diesel oxidation catalysts, diesel particulate filters, selective catalytic reduction systems, and ammonia oxidation catalysts.

[0004] In some engine systems, exhaust ducts or pipes used to deliver exhaust gas from the engine to an exhaust aftertreatment system may include internal structures, such as baffles or blades, for regulating exhaust gas flow or aiding in exhaust gas treatment. In the system described in German Patent Publication No. 102012021017A1 by Braun et al., three baffle elements are welded to the delivery pipe or inner wall of a first exhaust duct. These baffle elements are spaced apart and parallel to each other in the direction of the longitudinal axis of delivery. A reducing agent injector is arranged such that the injection flow at least partially impacts the main baffle surface of each baffle. Summary of the Invention

[0005] In one aspect, an exhaust duct includes: a wall having an inner surface that at least partially defines a flow channel; a first fin positioned within the flow channel and attached to the inner surface; a second fin positioned within the flow channel and attached to the inner surface, wherein the first fin and the second fin are spaced apart; and a support band attached to the inner surface, attached to the first fin at a first location spaced apart from the inner surface, and attached to the second fin at a second location spaced apart from the inner surface.

[0006] In another aspect, an engine system includes: an engine, an exhaust aftertreatment system, and an exhaust duct for directing flow from the engine to the exhaust aftertreatment system. The exhaust duct includes: a wall having an inner surface that at least partially defines a flow passage; a first fin positioned within the flow passage and attached to the inner surface; a second fin positioned within the flow passage and attached to the inner surface, wherein the first fin and the second fin are spaced apart; and a support band attached to the inner surface, attached to the first fin at a first location spaced apart from the inner surface, and attached to the second fin at a second location spaced apart from the inner surface.

[0007] In another aspect, a method for supporting a plurality of fins in an exhaust duct includes: attaching a first lateral edge and a second lateral edge of a first fin to an inner surface of the exhaust duct; attaching a first lateral edge and a second lateral edge of a second fin to the inner surface; connecting a first tip on the first fin to a second tip on the second fin, wherein the first tip and the second tip are radially inward from the inner surface; and connecting the first tip to the inner surface at a location spaced apart from the first lateral edge and the second lateral edge of the first fin. Attached Figure Description

[0008] Other features and advantages of the invention will become apparent from the description of the embodiments using the accompanying drawings. In the drawings: Figure 1 This is a schematic diagram of an exemplary engine and exhaust aftertreatment system according to the present invention; Figure 2 It is used for Figure 1 A cross-sectional view of an exemplary embodiment of the exhaust duct of the engine and exhaust aftertreatment system; Figure 3 yes Figure 2 An exploded view of the exhaust duct; and Figure 4 yes Figure 2 A front view of the inlet end of the exhaust duct. Detailed Implementation

[0009] Reference Figure 1 An exemplary embodiment of the engine and exhaust aftertreatment system 10 includes an engine 12 (such as a diesel engine) and an exhaust aftertreatment system 14. The engine 12 may include one or more turbochargers 16 defining one or more exhaust outlets 18. Exhaust gas exiting the turbochargers 16 via the one or more exhaust outlets 18 is directed to the exhaust aftertreatment system 14 via an exhaust duct 20.

[0010] The exhaust aftertreatment system 14 can be configured in various ways. For example, the exhaust aftertreatment system 14 may include, but is not limited to, one or more of the following: a diesel engine oxidation catalyst, a diesel engine particulate filter, a selective catalytic reduction system, and an ammonia oxidation catalyst. The components of the exhaust aftertreatment system 14 may be arranged individually or may be grouped together into one or more modules.

[0011] The exhaust duct 20 can be configured in various ways. For example, the length, size, shape, and material of the exhaust duct 20 may vary in different embodiments. The exhaust duct 20 may include multiple components or a single component. At least a portion of the exhaust duct 20 includes one or more flow regulators configured to regulate the flow rate of exhaust gas entering the exhaust aftertreatment system 14. As used herein, "regulating flow rate" means eliminating or reducing vortices and / or asymmetry in the flow rate. For example, regulating the flow rate of exhaust gas through a bend may include a structure for turning the flow to reduce the amount of vortices in the flow rate compared to the same bend without such a structure.

[0012] In the illustrated embodiment, the exhaust duct 20 includes a flexible portion 22 (such as a bellows) and an elbow 24 positioned at the inlet 26 of the exhaust aftertreatment system 14. In the illustrated embodiment, the elbow 24 includes one or more flow regulators. However, in other embodiments, one or more flow regulators may be positioned in another portion of the exhaust duct 20, such as, for example, in a straight portion or in a flexible portion. One or more flow regulators may be positioned at any suitable location within the exhaust duct 20.

[0013] Reference Figures 2 to 4 The elbow 24 includes one or more cylindrical sidewalls 30, each having an outer surface 32 and an inner surface 34 generally parallel to and opposite to the outer surface 32. The inner surface 34 defines a flow channel 36 having an inlet 38 and an outlet 40. The elbow 24 has a radius of curvature R. In the illustrated embodiment, the radius of curvature is constant and the elbow 24 bends at an angle of 45 degrees. However, in other embodiments, the radius of curvature may not be constant and the elbow 24 may bend at an angle greater than or less than 45 degrees.

[0014] One or more flow regulators associated with elbow 24 can be configured in various ways. Any structure capable of appropriately regulating the flow rate of exhaust gas entering exhaust aftertreatment system 14 can be used. In the illustrated embodiment, one or more flow regulators include multiple curved fins. (As shown in...) Figures 2 to 4 As shown, elbow 24 includes a first fin 50, a second fin 52, and a third fin 54. However, in other embodiments, elbow 24 may include fewer or more than three fins.

[0015] Each fin 50, 52, 54 is typically a thin plate, bent to match the curvature of the bend 24. Fins 50, 52, 54 are positioned within flow channels 36 and are uniformly spaced and parallel to each other. However, in other embodiments, fins 50, 52, 54 may be non-uniformly spaced and / or parallel to each other. For example, in some embodiments, the distance between the first fin 50 and the second fin 52 may be greater than or less than the distance between the second fin 52 and the third fin 54. Furthermore, the distance between any two fins may vary along the length of the fin or along the width of the fin.

[0016] The fins 50, 52, and 54 can be made of any material suitable for regulating exhaust flow. In an exemplary embodiment, the fins 50, 52, and 54 are made of a metal sheet (such as, for example, an 11GA metal sheet).

[0017] The first fin 50 includes a first surface 60, a second surface 62 generally parallel to and opposite to the first surface 60, a leading edge 64 extending between the first surface 60 and the second surface 62, a trailing edge 66 opposite to the leading edge 64 and extending between the first surface 60 and the second surface 62, a first lateral edge 68 extending between the leading edge 64 and the trailing edge 66, and a second lateral edge 70 opposite to the first lateral edge 68 and extending between the leading edge 64 and the trailing edge 66. The first fin 50 has a width W1 that is generally constant along its length. However, in other embodiments, the width W1 of the first fin 50 may vary along its length.

[0018] The first fin 50 may include a portion configured to connect to a support structure that connects the first fin 50, the second fin 52, and the third fin 54 together. The portion on the first fin 50 for connecting to the support structure can be configured in various ways. In the illustrated embodiment, the first fin 50 includes a pair of recesses 72 at a leading edge 64 for receiving the support structure and a pair of recesses 74 at a trailing edge 66 for receiving the support structure. The size, shape, location, and number of recesses for receiving the support structure may vary depending on the embodiment. In the illustrated embodiment, the pair of recesses 72 at the leading edge 64 and the pair of recesses 74 at the trailing edge 66 are typically rectangular slots.

[0019] The first fin 50 can be fixed relative to the cylindrical sidewall 30. The first fin 50 can be fixed relative to the cylindrical sidewall 30 by any suitable component. In the illustrated embodiment, the first fin 50 is attached to the inner surface 34 of the cylindrical sidewall 30 along at least a portion of the first lateral edge 68 and the second lateral edge 70. In the illustrated embodiment, the first fin 50 is attached to the inner surface 34 along both the first lateral edge 68 and the second lateral edge 70 by welds 76. The welds 76 are spaced apart along the first lateral edge 68 and the second lateral edge 70. In one embodiment, the welds 76 are approximately two inches long and are evenly spaced along the first lateral edge 68 and the second lateral edge 70. However, in other embodiments, the first lateral edge 68 and the second lateral edge 70 can be welded along their entire length, or the spacing and length of the welds can vary.

[0020] Similar to the first fin 50, the second fin 52 includes a first surface 80, a second surface 82 generally parallel to and opposite to the first surface 80, a leading edge 84 extending between the first surface 80 and the second surface 82, a trailing edge 86 opposite to the leading edge 84 and extending between the first surface 80 and the second surface 82, a first lateral edge 88 extending between the leading edge 84 and the trailing edge 86, and a second lateral edge 90 opposite to the first lateral edge 88 and extending between the leading edge 84 and the trailing edge 86. The second fin 52 has a width W2 that is generally constant along its length. However, in other embodiments, the width W2 of the second fin 52 may vary along its length.

[0021] The second fin 52 may include a portion configured to connect to a support structure that connects the first fin 50, the second fin 52, and the third fin 54 together. The portion on the second fin 52 for connecting to the support structure can be configured in various ways. In the illustrated embodiment, the second fin 52 includes a pair of recesses 92 at a leading edge 84 for receiving the support structure and a pair of recesses 94 at a trailing edge 86 for receiving the support structure.

[0022] Similar to the first fin 50, the second fin 52 is secured relative to the cylindrical sidewall 30. The second fin 52 can be secured relative to the cylindrical sidewall 30 by any suitable method. In the illustrated embodiment, the second fin 52 is attached to the inner surface 34 by welds 96. The welds 96 may be evenly spaced along both the first lateral edge 88 and the second lateral edge 90. In one embodiment, the welds 96 include: a weld approximately 1.5 inches long along both the first lateral edge 88 and the second lateral edge 90 adjacent to both the leading edge 84 and the trailing edge 86, and one or more welds approximately 1 inch long positioned between the 1.5-inch welds.

[0023] Similarly, the third fin 54 includes a first surface 100, a second surface 102 generally parallel to and opposite to the first surface 100, a leading edge 104 extending between the first surface 100 and the second surface 102, a trailing edge 106 opposite to the leading edge 104 and extending between the first surface 100 and the second surface 102, a first lateral edge 108 extending between the leading edge 104 and the trailing edge 106, and a second lateral edge 110 opposite to the first lateral edge 108 and extending between the leading edge 104 and the trailing edge 106. The third fin 54 has a width W3 that is generally constant along its length. However, in other embodiments, the width W3 of the third fin 54 may vary along its length.

[0024] The third fin 54 may include a portion configured to connect to a support structure that connects the first fin 50, the second fin 52, and the third fin 54 together. The portion on the third fin 54 for connecting to the support structure may be configured in various ways. In the illustrated embodiment, the third fin 54 includes a pair of grooves 112 at its leading edge 104 for receiving the support structure and a pair of grooves 114 at its trailing edge 106 for receiving the support structure.

[0025] Similar to the first fin 50 and the second fin 52, the third fin 54 is fixed relative to the cylindrical sidewall 30. The third fin 54 can be fixed relative to the cylindrical sidewall 30 by any suitable method. In the illustrated embodiment, the third fin 54 is attached to the inner surface 34 by a weld 116 extending along the entire first lateral edge 108 and the second lateral edge 110.

[0026] The elbow 24 includes a support structure that supports and connects the first fin 50, the second fin 52, and the third fin 54. The support structure can be configured in various ways. Any structure capable of increasing the structural length of the fins can be used. In the illustrated embodiment, the elbow 24 includes one or more support strips extending between and connecting the fins 50, 52, and 54. The one or more support strips can be configured and arranged in various ways. For example, the length, thickness, cross-sectional shape, number, and position of the material used for the support strips can vary in different embodiments.

[0027] In the illustrated embodiment, the elbow 24 includes a first support strip 120, a second support strip 122, a third support strip 124, and a fourth support strip 126. However, in other embodiments, more or fewer than four support strips may be used. In the illustrated embodiment, the first support strip 120 and the second support strip 122 are adjacent to the leading edges 64, 84, and 104 of the fins 50, 52, and 54, and the third support strip 124 and the fourth support strip 126 are adjacent to the trailing edges 66, 86, and 106 of the fins 50, 52, and 54. In other embodiments, the first support strip 120 and the second support strip 122 may be formed as a single strip, and the third support strip 124 and the fourth support strip 126 may be formed as a single strip.

[0028] As in Figures 2 to 4 As shown, the first support strip 120 is a generally thin, elongated strip of material having a rectangular cross-section, a curved portion 130 with radius Rs1, and a straight portion 132. The first support strip 120 has a length Ls, a width Ws, and a thickness Ts. In an exemplary embodiment, the width Ws is in the range of about 10 mm to about 14 mm or about 12 mm, and the thickness Ts is in the range of about 2 mm to about 4 mm or about 3 mm.

[0029] The first support strip 120 can be made of any suitable material. In the illustrated embodiment, the first support strip 120 is made of 11GA metal sheet.

[0030] In the illustrated embodiment, the first support band 120, the second support band 122, the third support band 124, and the fourth support band 126 are generally configured identically. Therefore, the description of the first support band 120 also applies to the other support bands 122, 124, and 126. Thus, the second support band 122 includes a curved portion 140 and a straight portion 142, the third support band 124 includes a curved portion 144 and a straight portion 146, and the fourth support band 126 includes a curved portion 148 and a straight portion 150.

[0031] However, in other embodiments, the support bands may be configured to be different from each other. For example, in the illustrated embodiment, the radii of the bends 130, 140, 144, and 148 of the first support band 120, the second support band 122, the third support band 124, and the fourth support band 126 are the same. However, in other embodiments, one or more of the bends 130, 140, 144, and 148 may have radii different from those of the other bends 130, 140, 144, and 148.

[0032] When assembled, the first support band 120 is connected to the inner surface 34 of the elbow 24 and the respective fins 50, 52, 54. The first support band 120 can be connected to the inner surface 34 and the fins 50, 52, 54 in various ways. In the illustrated embodiment, the curved portion 130 of the first support band 120 is connected to the inner surface 34 of the elbow 24 via a weld 160. The straight portion 132 is received in one of the pairs of grooves 72, 92, 112 on the leading edges 64, 84, 104 of the fins 50, 52, 54 and is secured in place by the weld 162. Thus, the first support band 120 connects a first tip on the first fin 50 to a second tip on the second fin 52, and connects the second tip on the second fin 52 to a third tip on the third fin 54. The respective connected tips are spaced apart from the inner surface 34. In the illustrated embodiment, the connected tips are linearly aligned because they are connected by the straight portion 132. However, in other embodiments, the support strip may not be connected to the fin via a straight portion, so the connected tips may not be linearly aligned.

[0033] The first support band 120 attaches the fins 50, 52, and 54 together at their radially inwardly extending tips from the inner surface 34, and also attaches these tips to the inner surface 34 of the elbow 24. The straight portion 132 extends a distance X across the groove 112 in the third fin 54, but does not engage with the inner surface 34 of the elbow 24, while the curved portion 130 is welded to the inner surface 34 at the opposite location.

[0034] Similar to the first support band 120, the curved portion 140 of the second support band 122 is welded to the inner surface 34 of the elbow 24 at or near the same tip as the curved portion 130 of the first support band 120, so that the first support band 120 and the second support band 122 form a U-shape. The straight portion 142 of the second support band 122 is received in another groove of the pair of grooves 72, 92, 112 attached to the first support band 120 and is welded in place. Like the first support band 120, the straight portion 142 of the second support band 122 extends a shorter distance over the groove 112 in the third fin 54, but does not engage with the inner surface 34 of the elbow 24, where the curved portion 140 is welded to the inner surface 34 at the opposite location.

[0035] The groove in a pair of grooves 72 that attaches to the straight portion 132 of the first support band 120 is separated from the first lateral edge 68 of the first fin 50 by a first distance D1. The groove in a pair of grooves 72 that attaches to the straight portion 142 of the second support band 122 is separated from the second lateral edge 70 of the first fin 50 by a second distance D2. The pair of grooves 72 are positioned to be separated from each other by a third distance D3.

[0036] In the illustrated embodiment, the first distance D1 is equal to the second distance D2, and the third distance D3 is greater than the first distance D1 and the second distance D2. However, in other embodiments, the first distance D1 and the second distance D2 may be different, and the third distance D3 may be equal to or less than the first distance D1 or the second distance D2. In an exemplary embodiment, the ratio of D1 to D3 is in the range of 0.75 to 1.25.

[0037] The description of the lateral edges 68, 70 and the spacing between them relative to a pair of grooves 72 also applies to a pair of grooves 74 on the trailing edge, multiple pairs of grooves 92, 94 on the second fin 52, and multiple pairs of grooves 112, 114 on the third fin 54. For example, in one embodiment, the second fin 52 is positioned at or near the middle of the flow channel 36. Therefore, the second fin 52 bisects or nearly bisects the flow channel 36. In this position, the width of the second fin 52 is equal to or nearly equal to the inner diameter of the elbow 24. The multiple pairs of grooves 92, 94 on the second fin 52 are positioned such that each pair of grooves 92, 94 bisects or nearly bisects the width of the second fin 52 at the leading edge 84 and the trailing edge 86, respectively. Therefore, the distance from the first lateral edge 88 to one of the grooves 92 is equal to or nearly equal to the distance from the second lateral edge 90 to the other groove. Further, the distance between two of the grooves in a pair of grooves 92 is equal to the distance from the first lateral edge 88 to one of the grooves 92. By dividing the maximum width of the fin into three or approximately three equal parts, the width of the unsupported fins at the leading and trailing edges is minimized.

[0038] The third support band 124 and the fourth support band 126 are attached to the trailing edges 66, 86, and 106 of the fins 50, 52, and 54 in a manner similar to that of the first support band 120 and the second support band 122, which are attached to the leading edges 64, 84, and 104 of the fins 50, 52, and 54. Therefore, the curved portion 144 of the third support band 124 is connected to the inner surface 34 of the elbow 24 via a weld 174, and the straight portion 146 is received in one of the multiple pairs of grooves 74, 94, and 114 on the trailing edges 66, 86, and 106 of the fins 50, 52, and 54 and welded to that groove. Similar to the first support band 120 and the second support band 122, the straight portion 146 of the third support band 124 extends a shorter distance beyond the groove 114 in the third fin 54, but does not engage with the inner surface 34 of the elbow 24; the curved portion 144 is welded to the inner surface 34 at the opposite location.

[0039] The curved portion 148 of the fourth support band 126 is welded to the inner surface 34 of the elbow 24 at or near the same tip as the curved portion 144 of the third support band 124, so that the third support band 124 and the fourth support band 126 form a U-shape. The straight portion 150 of the fourth support band 126 is received in one of the pairs of grooves 74, 94, 114 on the trailing edges 66, 86, 106 of the fins 50, 52, 54, and is welded in place. Like the third support band 124, the straight portion 150 of the fourth support band 126 extends a shorter distance beyond the groove 114 in the third fin 54, but does not engage with the inner surface 34 of the elbow 24, where the curved portion 144 is welded to the inner surface 34 at the opposite location.

[0040] Industrial applicability The engine and exhaust aftertreatment system 10 can be used in a variety of applications. For example, the engine and exhaust aftertreatment system 10 can be used to power mobile machinery (such as locomotives, boats, construction equipment, off-road trucks, and highway trucks) or in stationary applications (such as generator sets). The exhaust duct 20 directs exhaust gas from the engine 12 to the exhaust aftertreatment system 14 along a designated route. Due to space constraints in many applications, the exhaust duct 20 may have multiple curves and bends. For example, a bend 24 may be positioned at the inlet 26 of the exhaust aftertreatment system 14. Fins 50, 52, and 54 act as flow regulators to reduce the amount of vortices in the exhaust gas that would normally be generated when the exhaust gas flows through bends.

[0041] Due to the type of application and the proximity of elbow 24 to engine 12 and turbocharger 16, elbow 24 and fins 50, 52, 54 are subject to thermal and vibration-related stresses, which could damage fins 50, 52, 54 and the welds 76, 96, 116 used to secure fins 50, 52, 54 to inner surface 34. Support bands 120, 122, 124, 126 and spaced welds 76, 96 on the lateral edges of the first fin 50 and the second fin 52 help to counteract stress in elbow 24.

[0042] For example, support bands 120, 122, 124, and 126 can increase the structural strength of fins 50, 52, and 54 and help reduce stress. Fins that are only connected to the inner surface 34 of the sidewall 30 of the elbow 24 at their lateral edges may experience vibration or resonance in the portion of the fins extending inward from the lateral edges. Support bands 120, 122, 124, and 126 connect fins 50, 52, and 54 together and connect them to the inner surface 34 at locations on fins 50, 52, and 54 radially inward from the lateral edges of the fins. Therefore, support bands 120, 122, 124, and 126 can change the natural frequency of fins 50, 52, and 54 and increase the stiffness of fins 50, 52, and 54, thereby reducing or eliminating vibration.

[0043] Furthermore, the curved portions 130, 140, 144, and 148 of each of the support bands 120, 122, 124, and 126 can counteract thermal expansion and vibration. In contrast to linear supports, the curved portions 130, 140, 144, and 148 can accommodate thermal expansion, resulting in stress concentration in the curved portions of the support bands 120, 122, 124, and 126 rather than in the weld 160 used to attach the support bands 120, 122, 124, and 126 to the inner surface 34. By concentrating stress in the curved portions 130, 140, 144, and 148, the likelihood of stress-induced damage to the weld 160 is reduced.

[0044] Furthermore, welds 76 and 96 for attaching the first fin 50 and the second fin 52 to the inner surface 34 are spaced apart along the lateral edges 68, 70, 88, and 90 of the first fin 50 and the second fin 52. Compared to a continuous weld extending along the entire length of the lateral edge, the spaced welds 76 and 96 can reduce the stress in those welds caused by the thermal expansion of the fins and sidewalls 30.

[0045] Given the many possible embodiments in which the principles of the invention can be applied, it should be understood that the illustrated embodiments are merely preferred examples and should not be considered as limiting the scope of the invention. Rather, the scope of the invention is defined by the following claims.

Claims

1. An engine system, comprising: engine; Exhaust aftertreatment system; as well as Exhaust duct, the exhaust duct comprising: Flexural portion; and The elbow is located at the inlet of the exhaust aftertreatment system. The elbow has a radius of curvature and includes: A cylindrical sidewall having an inner surface that at least partially defines a flow channel; A first fin, positioned within the flow channel and attached to the inner surface, the first fin having a leading edge; A second fin is positioned within the flow channel and attached to the inner surface, the second fin having a second leading edge, wherein the first fin is spaced apart from the second fin; A first support strip, attached to the inner surface, attached to the first fin at a first location adjacent to the leading edge and spaced apart from the inner surface, and attached to the second fin at a second location adjacent to the second leading edge and spaced apart from the inner surface; and A second support strip is attached to the inner surface, and is attached to the first fin at a third position adjacent to the leading edge and spaced apart from the inner surface, and to the second fin at a fourth position adjacent to the second leading edge and spaced apart from the inner surface. The first support strip has a curved portion attached to the inner surface and a straight portion attached to the first fin and the second fin, and the second support strip has a curved portion attached to the inner surface and a straight portion attached to the first fin and the second fin, such that the first support strip and the second support strip form a U-shape.

2. The exhaust duct of claim 1, further comprising a third fin positioned within the flow channel and attached to the inner surface, the third fin having a third leading edge, wherein, The first support strip is attached to the third fin at a fifth position adjacent to the third leading edge and spaced apart from the inner surface, and the second support strip is attached to the third fin at a sixth position adjacent to the third leading edge and spaced apart from the inner surface.

3. The exhaust duct according to claim 2, wherein, The first position, the second position, and the fifth position are linearly aligned.

4. The exhaust duct according to claim 1, wherein, The first support strip is received in a groove in the leading edge.

5. The exhaust duct according to claim 1, wherein, The straight portion of the first support strip is received in a first groove in the leading edge, and the straight portion of the second support strip is received in a second groove in the leading edge.

6. The exhaust duct according to claim 5, wherein, The first fin has a first lateral edge and a second lateral edge opposite to the first lateral edge, wherein the first groove is separated from the first lateral edge by a first distance, and the second groove is separated from the second lateral edge by a second distance, wherein the first distance is equal to the second distance.

7. The exhaust duct according to claim 1 further includes a third support strip, wherein, The first fin has a trailing edge opposite the leading edge, and wherein the third support band is received in a groove in the trailing edge.

8. The exhaust duct according to claim 7 further includes a fourth support strip, wherein, The first fin has a trailing edge opposite the leading edge, and wherein the fourth support band is received in a groove in the trailing edge.

9. The exhaust duct according to claim 8, wherein, The third support band has a curved portion attached to the inner surface and a straight portion attached to the first fin and the second fin, and the fourth support band has a curved portion attached to the inner surface and a straight portion attached to the first fin and the second fin, such that the third support band and the fourth support band form a U-shape.

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