Patent Application
20090023375
1. Field of the Invention
The present invention relates to ductwork for carrying a fluid flow.
2. Discussion of the Background
Ductwork used to carry fluid at high temperatures is subject to stresses due to thermal expansion of the ductwork and/or other components housed within the ductwork. Additionally, in certain applications, the ductwork can be subject to detonation of fuel that is either intentionally or accidentally flowing within the ductwork. For example, if fuel accidentally flows within the ductwork and high temperature conditions are present within the ductwork such that the fuel is raised to a temperature above the auto-ignition temperature of the fuel, then the fuel could detonate within the ductwork. Such a detonation could result in irreversible damage to the ductwork, and could cause harm to people or structures near the ductwork at the time of the detonation.
In an effort to eliminate the above problems associated with ductwork used in high temperature applications, the inventors of the present invention have developed an apparatus and method of providing detonation damage resistance in ductwork, as is described below.
The present invention advantageously provides a ductwork system including a duct having a plurality of ducting panels joined together to define a flow passage extending therethrough, where the duct is provided with structure for resisting damage thereto caused by a detonation within the duct.
In a first aspect of the invention, a structure is provided for resisting damage that includes an internal bracing within and extending across the flow passage of the duct to tie at least two sides of the duct together. An example of such an internal bracing is a reinforcement panel including a mounting frame with one or more elongated members extending from one side of the frame attached to a ducting panel to another side of the frame attached to an opposite ducting panel.
In a second aspect of the invention, which can be implemented as an alternative to or in addition to the structure in the first aspect of the invention, the duct has structure for resisting damage that includes providing the duct with at least one curved or faceted side along an axial length of the duct.
A more complete appreciation of the invention and many of the attendant advantages thereof will become readily apparent with reference to the following detailed description, particularly when considered in conjunction with the accompanying drawings, in which:
Embodiments of the present invention are described hereinafter with reference to the accompanying drawings. In the following description, the constituent elements having substantially the same function and arrangement are denoted by the same reference numerals, and repetitive descriptions will be made only when necessary.
The inventors have determined that when designing ductwork many factors must be taken into account, such as the cost of manufacture and assembly of such ductwork, as well as structural requirements of the ductwork system. Thus, the ductwork configuration and the type of material used to construct the ductwork can be selected based on such factors as the cost of the material, the strength of the material, the amount of material needed to satisfy strength requirements of the ductwork, the reaction of the material to the conditions in which the material will be used, the weight of the material, the ease and costs associated with manufacturing and assembling the ductwork using that material, etc. However, simply providing relatively thick walls in order to provide resistance to detonation damage is not typically advantageous due to the increase in cost and weight of the ductwork. Further, ductwork of extreme thickness disadvantageously has low flexibility. In high temperature applications where temperature gradients exist, such as in heat exchangers and heat exchange reactors it is desirable that the ductwork be flexible as well as strong in order to prevent mechanical failure due to thermal stresses. Also, the inventors have determined that the use of external braces and supports to provide detonation damage resistance for the ductwork is not typically advantageous, since such external braces and supports may be at a lower temperature than the ductwork which could result in thermal expansion problems caused by the uneven expansion of the external braces and supports relative to the ductwork.
The present invention advantageously provides apparatuses and methods to significantly reduce or entirely eliminate damage caused by a detonation within ductwork without the need for providing overly thick walls or external bracing unless such features are otherwise desirable for use therewith. While the present invention is not limited to the configurations of the preferred embodiments described and depicted herein, the preferred embodiments of the present invention use thin, flexible walls of sheet metal in order to withstand stresses caused by thermal expansion, while yet still maintaining a lightweight ductwork configuration, which is flexible and can accommodate substantial temperature gradients without developing undue thermal stresses.
In a first aspect of the present invention, the invention provides an internal bracing that extends across a flow passage of the ductwork in order to provide a reinforcement structure to resist outward forces acting on walls of the ductwork caused by a detonation within that flow passage. For example, such an internal bracing can be an elongated member having a first end attached in any manner to a wall of the ductwork and a second end attached in any manner to an opposite wall of the ductwork. Thus, if a detonation occurs within the flow passage, then the elongated member will provide resistance to the outward forces from the detonation along the length of the elongated member (e.g., the elongated member will be in tension), thereby holding the opposing walls of the ductwork together and preventing damage to the walls.
The internal bracing of the present invention can take many forms and can be attached to the ductwork in many different ways, the preferred embodiments of which are set forth below. For example, the internal bracing can be provided in a reinforcement panel having an outer mounting frame and one or more elongated members extending in one or more directions across an opening through the frame (e.g., plural elongated member in a parallel or a non-parallel arrangement, plural elongated members in a crossing (or grid or net) pattern in a perpendicular arrangement or a non-perpendicular arrangement, etc.). The internal bracing can be elongated members connected to or integrally part of baffle plates in the flow passage of the ductwork. (See, e.g.,
In this embodiment, each of the side portions 14-17 are configured to be clamped and sandwiched between adjacent sections of ducting panels at a joint between the adjacent sections of ducting panels, and mounted to the ducting panels. The side portions 14-17 can be mounted to the ducting panels using, for example, a plurality of mounting holes 18 that are provided about the perimeter of the frame 12, and providing, for example, bolt-and-nut fasteners through the mounting holes and corresponding mounting holes on the ducting panels. Additionally or alternatively, adjacent edges of the frame 12 and ducting panels can be welded together to provide further structural connection therebetween. Alternatively to the above mounting of the frame 12, the frame 12 can be directly attached to an inner surface of the ductwork at any position along the flow path, for example, by welding or other mounting structure or method, and can be provided at or adjacent to a joint or at any other location along the length of the flow path.
In the reinforcement panel 10 depicted in
Numerous different configurations of the internal bracing are possible. For example, the internal bracing can be constructed to include numerous different configurations of one or more of the elongated members 20. The elongated members 20 can be provided across the entire opening, the members 20 can be provided across only a portion of the opening, the members 20 can be evenly spaced apart from one another, the members can be provided with different spacings therebetween, the members 20 can include a combination of evenly spaced and non-evenly spaced elongated members, etc. Additionally, the elongated members 20 can be provided with the same shape, cross-section, and size, with different shapes, cross-sections, and sizes, or any combination thereof. The elongated members 20 can be formed of the same material or material properties, or different materials or material properties. Also, elongated members can also be provided that extend in one or more directions across the opening that are different than elongated members 20 in
The reinforcement panel 10 is preferably mounted at a location within the ductwork where there is a risk that detonation will occur, and the reinforcement panel is preferably mounted within the ductwork in an orientation that provides resistance to detonation forces acting on a weak portion of the ductwork at that location. For example, the reinforcement panel 10 depicted in
The ductwork system 30 depicted in
The ductwork of the ductwork system 30 is constructed using ducting panels 32 of different shapes and sizes, but which are typically formed from sheet metal plates with folded ends 34 that are used to join together adjacent panels, for example, by using bolt-and-nut fasteners through mounting holes in the ends of the panels and/or by welding together abutting edges of adjacent panels. This embodiment of the present invention uses ducting panels 32 that provide thin, flexible walls that withstand stresses caused by thermal expansion, and advantageously provide a lightweight ductwork configuration. However, certain sections of the ductwork may be at risk for detonation of fuel within the gas in the flow passage, and therefore these sections of the ductwork may be susceptible to irreversible mechanical damage to the ductwork caused by such detonations. Therefore, in order to significantly reduce or entirely eliminate damage caused by such a detonation within ductwork, the ductwork system 30 depicted in
Reinforcement panel 60 includes a mounting portion (or outer mounting frame) 62 with an opening 64 extending through the frame 62. A plurality of mounting holes 66 are provided about the perimeter of the frame 62, and are used with bolt-and-nut fasteners to mount the frame 62 to the adjacent ducting panels. A plurality of elongated members 68 extend in parallel to one another across the opening 64. The panel 60 is oriented such that the elongated members 68 are oriented to provide detonation resistance to, for example, panel 37 of duct section 38 (and/or panels adjacent thereto), which is at risk of have a detonation therein. The configuration and number of elongated members 68 are determined based upon the strength requirements of the internal bracing and the flow requirements through the flow passage at this location in the ductwork.
Reinforcement panel 70 includes a mounting portion (or outer mounting frame) 72 with an opening 74, a plurality of mounting holes 76, and a plurality of elongated members 78. The panel 70 is oriented such that the elongated members 78 are oriented to provide detonation resistance to, for example, panel 39 of duct section 38 (and/or panels adjacent thereto), which is at risk of have a detonation therein. The configuration and number of elongated members 78 are determined based upon the strength requirements of the internal bracing and the flow requirements through the flow passage at this location in the ductwork.
Reinforcement panel 80 includes a mounting portion (or outer mounting frame) 82 with an opening 84, a plurality of mounting holes 86, and a plurality of elongated members 88. The panel 80 is oriented such that the elongated members 88 are oriented to provide detonation resistance to, for example, panel 47 of duct section 46 and/or panel 49 of duct section 48 (and/or other adjacent panels), which are at risk of have a detonation therein and form (panel 47 and panel 49 together) a long, flat, otherwise unsupported surface that is very susceptible to damage from a detonation. The configuration and number of elongated members 88 are determined based upon the strength requirements of the internal bracing and the flow requirements through the flow passage at this location in the ductwork.
Reinforcement panel 90 includes a mounting portion (or outer mounting frame) 92 with an opening 94, a plurality of mounting holes 96, and a grid of perpendicularly crossing elongated members 98. The panel 90 is provided with the grid of perpendicularly crossing elongated members 98 that are oriented to provide detonation resistance to, for example, all four panels 51 around the perimeter of duct section 50 and/or the panels around the perimeter of the economizer section 52, which are at risk of having a detonation therein and are otherwise unsupported surfaces that are susceptible to damage from a detonation. The configuration and number of elongated members 98 are determined based upon the strength requirements of the internal bracing and the flow requirements through the flow passage at this location in the ductwork.
The present invention provides a method and structure for providing detonation damage resistance to ductwork in which one aspect of the invention provides internal braces or supports to tie the ducting panels of the ductwork together in order to significantly reduce damage thereto caused by a detonation within the ductwork. Since detonations apply forces in opposing directions on opposite sides of the ducting, the internal bracing, which is sufficiently strong to resist deformation and sufficiently well attached to the walls of the ducting, will eliminate the damage to the walls around the bracing. One or more internal bracings can eliminate damage throughout an entire ductwork system. Also, multiple bracings can be used to dampen a pressure wave caused by the detonation as the pressure wave travels through the ductwork. The bracing can be made from a single piece of sheet metal, as in the reinforcement panels shown in
Based on the shape of ductwork, various configurations of internal bracing can be provided to tie and link together different wall panels. For example, in rectangular ducts, the elongated members of the reinforcement panel depicted in
The second aspect of the invention involves providing ducting panels or walls that avoid long straight profile sections in areas most susceptible to damage during a detonation. Note that the ductwork in
Additionally, the second aspect of the invention can also advantageously eliminate joints by using a single piece of material 230 to form a first baffle section 232, a first ducting wall section 234, and a second ducting wall section 236, where the first ducting wall section 234 is adjacent the first baffle section 232 and a second baffle (which is adjacent to the first baffle section 232), and where the second ducting wall section 236 is adjacent to the second baffle and a third baffle (which is adjacent to the second baffle). By combining a baffle and one or more ducting wall sections into an integral piece of material and thereby eliminating joints therebetween, the ductwork system will be even more damage resistant. Advantageously, this embodiment also reduces the number of individual ducting pieces used to form the flexible ductwork system. Further advantageously, this embodiment reduces the number of joints (which were previously necessary at an upper side and a lower side of each successive pass in the ductwork in order to sandwich each baffle in between two adjacent ducting wall sections). The joints typically provide stiffness to the ductwork and disadvantageously reduce the ability of the ductwork to flex under hot operating conditions. Thus, reducing the number of joints allows the ductwork to flex and reduces stresses in the ductwork. Also, the joints provided in this embodiment are not formed from edges of the ductwork walls formed at ninety degree angles (as are the joints depicted in
For ducting surrounding a baffled tubular heat exchanger (as discussed above and depicted in
The embodiment depicted in
The baffle portions 314 and 324 link the wall of the ductwork 300 to the stiff tube bundle of the tubular heat exchanger 340.
End portions 318, 322, and/or 329 that are adjacent to one another are joined using, for example, a plurality of mounting holes (not shown) provided thereon and bolt-and-nut fasteners. Additionally or alternatively, terminal ends 319, 323, and/or 330 that are adjacent to one another can be welded together to provide further structural connection therebetween. Main ducting portions that are adjacent to one another are provided such that they are at a non-zero angle to one another to provide a faceted outer profile of the duct. The joints formed in this manner provide the ductwork 300 with the ability to flex in a direction along the axial length of the tubular heat exchanger 340 without significant stresses, while providing a strong duct that can withstand and absorb forces caused by detonations within the duct without resulting in significant (or any) damage thereto.
The ductwork system 400 has a flow path with a repeating S-shaped configuration according to the second aspect of the present invention. The sides of the ductwork are formed using faceted or curved wall sections 410, which approximate semi-circular curved portions extending around the open end of the baffles 420. Each wall section 410 can include a lower portion 412 that abuts an upper portion 414 of an adjacent wall section, such that the abutting wall sections can be joined at joint 416.
The ductwork system 400 includes front and rear panels 430 that are joined to the wall sections 410 and to adjacent panels. The panels 430 have two front edges 432 that bend outward to form a flange. The edges 432 of each panel are joined to abutting edges of adjacent panels. The panels 430 also have a faceted or curved outer edge 434 that bend outward to form a flange, which is joined to abutting wall sections that correspond therewith.
The ductwork system of the present invention improves internal pressure resistance and cycle life. The ductwork system 400 includes polygonal side, front, and rear panels, which provide a close approximation to an arcuate wall to assist with pressure loading, by approximating the stress state of a thin-walled cylinder. The side panels and baffle for each pass are made up of either two or three individual pieces that are cut and bent from sheet metal. Each baffle can be welded to the side panels for a pass above and a pass below in order to facilitate weld access to the final assembly. The arcuate front and rear end panel sections can be rosette welded to the baffles along their centerline and then joined to each other by welding along the edges of the perimeter flanges.
The reactor system will experience thermal expansion due to the use of different material and large temperature differences between the burner's inlets at the first pass to the last pass of the reactor as the gas travels to a super-heater at the outlet thereof and large temperature differences between the mean metal temperatures of the ductwork and the heat exchanger tubing. The panels of each pass can be formed of different materials along the length of the ductwork system depending upon the strength requirements are each pass and the thermal and/or corrosion conditions at each pass.
As compared to the rectangular ducting configuration depicted in
It should be noted that the exemplary embodiments depicted and described herein set forth the preferred embodiments of the present invention, and are not meant to limit the scope of the claims hereto in any way. Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
