Patent Application
20120080160
1. Field
The disclosed and claimed concept relates generally to a regenerative heat exchanger and, more particularly, to a regenerative heat exchanger and a seal apparatus that employs a labyrinth seal.
2 Related Art
Regenerative heat exchangers and seals employed therein are generally known in the relevant art, an example of which is presented in U.S. Pat. No. 4,997,028, the disclosures of which are incorporated herein by reference. A regenerative heat exchanger employs the heat of the exhaust gases of a burner, such as in a power plant, to heat the inlet air to the burner to improve the burner's efficiency. A typical regenerative heat exchanger includes a stationary housing within which is disposed a rotating heat exchanging body. The heat exchanging body includes a plurality of fins that each extend radially between a central hub and a cylindrical outer wall, with the cylindrical outer wall typically being disposed in relatively close proximity to a cylindrical wall of the stationary housing. An exhaust gas duct and a separate inlet air duct are connected with the stationary housing and pass exhaust gas and inlet air, respectively, through the housing and into heat exchange contact with the radially extending fins of the rotating heat exchanging body.
In order to resist contamination of the inlet air with exhaust gases, seals are typically mounted to the radially extending fins of the heat exchanging body and extend into contact with the housing, with such seals moving with the heat exchanging body as it rotates within the housing. For example, if the heat exchanging body rotates about a vertical axis, the fins extend horizontally between the hub and the cylindrical outer wall, and the seals extend from upper and lower edges of the fins into contact with flat interior surfaces of the stationary housing.
Additional seals typically extend between the cylindrical outer wall of the heat exchanging body and the cylindrical wall of the housing. Such additional seals are provided in order to resist the exhaust gases and inlet air from flowing through the annular space between the outer wall of the heat exchanging body and the cylindrical wall of the housing, because such flow thought the annular space would undesirably cause the exhaust gases and inlet air to avoid the radial fins of the heat exchanging body, whereby the desired heat transfer would not occur.
The seals themselves typically include a seal element that is formed of a heat resistant material that is at least partially metallic and is typically manufactured from materials such as those that are used to manufacture brake shoes. The seal element typically is mounted to a sheet metal support that is connected with either the heat exchanging body or the housing, with the seal element being sealingly engaged with the other of the heat exchanging body and the housing. Most typically, the seal element is on the order of roughly three or four inches in length, and thus a large number of seal elements and their sheet metal supports are connected together to form an elongated seal assembly that extends about the circumference of a regenerative heat exchanger which may be on the order of twenty feet in diameter.
In order to resist the flow of exhaust gases and air through the small space that may exist between each adjacent pair of seal elements, each individual sheet metal support also includes an outwardly extending lip. The lip is situated close to the seal element and extends parallel with the seal element and at nearly the height of the seal element so that the edge of the lip is disposed in close proximity yet slightly spaced from whichever surface of the heat exchanging body and the housing is engaged by the seal element. The lips thus provide a further barrier to the flow of exhaust gases and air through gaps between the seal elements.
In operation, the exhaust gases flow over and past the radially extending fins of the heat exchanging body and heat the fins. The heated fins then rotate with the heat exchanging body out of communication with the exhaust gas duct and into heat exchange relation with the inlet air flowing within the air duct. The inlet air is thereby heated and flows into the burner of the power plant. The cooled fins are then rotated back into contact with the exhaust gases.
While such seals have been generally effective for their intended purposes, they have not been without limitation. For instance, since the seal element sealingly slides along a surface of either the heat exchanging body or the housing (or on a wear band disposed thereon), the seal elements experience wear due to friction and must be periodically replaced, which is costly. Moreover, the edges of the aforementioned lips are intended to be spaced from the surface that is engaged by the seal elements and are intended to therefore not contact such surface. However, as the seal elements wear they lose material, and the lip can thus become engaged with and wear against the surface of the heat exchanging body or the housing, which is undesirable. It thus would be desirable to provide an improved seal and regenerative heat exchanger that address these and other shortcomings associated with known seals.
An improved regenerative heat exchanger and seal assembly employ a plurality of instances of a seal apparatus, with each seal apparatus including a seal member that includes a seal tab that extends from one end of the seal member and further includes a corresponding notch at the opposite end of the seal member. The seal tab is receivable in a notch of an adjacent seal apparatus, and the engagement of the seal tabs in the notches creates a labyrinth seal by providing a tortuous path that resists the flow of exhaust gases and air past the seal assembly. The improved seal assembly also advantageously avoids the need to provide an additional lip such as has been known in the relevant art to provide a further barrier to the flow of exhaust gases and air through gaps between adjacent seal elements. This reduces cost and also avoids the possibility of destructive wear that sometimes can occur between such a lip and the surface of the heat exchanging body or the housing of the regenerative heat exchanger against which the seal member is sealingly disposed.
Accordingly, an aspect of the disclosed and claimed concept is to provide an improved seal apparatus that provides improved sealing by employing a notch and a tab in each seal member to provide a labyrinth seal.
Another aspect of the disclosed and claimed concept is to provide an improved regenerative heat exchanger employing such an improved seal apparatus.
A further understanding of the disclosed and claimed concept can be gained from the following Description when read in conjunction with the accompanying drawings in which:
Similar numerals refer to similar parts throughout the specification.
An improved seal apparatus 4 is depicted in
As can be understood from
The housing 20 itself includes a first plate 40 and a second plate 44 which, from the perspective of
In the embodiment shown in
As can be understood from Fig. I, each seal apparatus 4 comprises a support 72 and a seal member 76 affixed to the support 72. In the exemplary embodiment depicted herein, the seal member 76 is affixed to the support 72 with a pair of fasteners 80 (
The support 72 is fashioned from a heat resistant sheet metal such as a high chromium content stainless steel, many examples of which are known in the relevant art. The seal member 76 is formed from a material that is resistant to friction wear and is typically manufactured at least partially of metallic materials or ceramic materials or both. The seal member 76 often is formed of materials similar to those which are used for the manufacture of brake shoes.
The seal member 76 itself comprises an elongated seal body 82, at one end of which is disposed a protruding seal tab 84, and at an opposite end which is formed a notch 86. A sealing surface 88 extends across the entirety of the seal member 76 and, in particular, extends across the seal body 82 including the region of the notch 86, and further extends across the seal tab 84. The sealing surface 88 may be substantially planar, at least initially, i.e., prior to wear that may occur from sliding contact with a corresponding surface of the regenerative heat exchanger 8.
As can be further understood from
As mentioned above, a plurality of instances of the seal apparatus 4 can be assembled together to form the seal assembly 12 as is indicated in
As can be understood from
The seal assembly 12 can be assembled with a large quantity of the seal apparatuses 4 into a single piece for installation into the regenerative heat exchanger 8, but it is more likely that the seal assembly 12 will be assembled in a number of pieces, such as by assembling together fifteen or twenty adjacent seal apparatuses 4, by way of example, along with appropriately sized connection plates 110A and 110B. The seal assembly 12, in whatever configuration, is then affixed to the outer wall 32 of the heat exchanging body 16 by receiving it in a number of clamps 118 and tightening a number of fasteners 122, both of which are components of the heat exchanging body 16, as is depicted generally in
The improved seal apparatus 4 with its labyrinth seals 94 advantageously provides improved sealing performance when compared with known seals used in regenerative heat exchangers. Moreover, since the provision of the labyrinth seals 94 avoids the need to additionally provide a lip adjacent the first surfaces 96 of the seal members 76, cost is reduced. Furthermore, by avoiding the need to provide such a lip adjacent the first surface 96 of the seal members 76, the potential for enhanced wear of the connecting wall 48 due to engagement of such a lip against the connecting wall 48 due to wearing away of the seal members 76 is advantageously avoided.
While specific embodiments of the disclosed and claimed concept have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the disclosed and claimed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof.
