FLEXIBLE SEAL FOR A ROTARY REGENERATIVE PREHEATER
A seal assembly includes a leaf assembly and a supplemental leaf assembly. The leaf assembly includes a first leaf having a first base section. The first base section defines a first fastening area for securing the first leaf to a diaphragm of the preheater. The first leaf has a first elongate section extending away from the first base section and terminating at a first distal end thereof. The leaf assembly further includes a second leaf that engages a portion of the first leaf. The second leaf has a second base section. The second base section defines a second fastening area for securing the second leaf to the diaphragm. The second leaf has a second elongate section extending away from the second base section and terminating at a second distal end thereof. The supplemental leaf assembly is secured to the first leaf and slidingly engaging the second leaf.
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This invention relates to a flexible seal for a rotary regenerative preheater, and more particularly to a flexible seal having multiple leafs.
BACKGROUNDAs shown in
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During operation of the preheater 10, a surface 31′ of the sector plates 30A and 30B is spaced apart from a distal end of the seal 40. However, during start-up conditions when the preheater 10 and ducts 22, 24, 26 and 28 are relatively cold, the surface 31 of the sector plates 30A and 30B slidingly engage the respective seal 40. Such sliding engagement causes the flexible seal leaf 42 to wear and results in bypass leakage between the air sector 32 and the gas sector 34. In addition, through laboratory testing, the inventors have surprisingly found that such sliding engagement of the seal 40 with the respective sector plate 30A and 30B results in oscillatory vibration of the seal 40, as indicated by the arrow V, causing fatigue failure thereof. In addition, the inventors have discovered that because the seal 40 is mounted on a leading edge of the diaphragm 18, the edge of the diaphragm 18 acts as an abrupt fulcrum 47 upon which the seal 40 is bent over and causes stress concentrations at the mating portion of the seal 40. Such stress concentrations cause premature failure of the seal 40.
SUMMARY OF THE INVENTIONThere is disclosed herein a seal assembly for a rotary preheater. The seal assembly includes a leaf assembly and a supplemental leaf assembly. The leaf assembly includes a first leaf having a first base section. The first base section defines a first fastening area for securing the first leaf to a diaphragm of the preheater. The first leaf has a first elongate section extending away from the first base section and terminating at a first distal end thereof. The leaf assembly further includes a second leaf that engages a portion of the first leaf. The second leaf has a second base section. The second base section defines a second fastening area for securing the second leaf to the diaphragm. The second leaf has a second elongate section extending away from the second base section and terminating at a second distal end thereof. The supplemental leaf assembly is secured to the first leaf and slidingly engaging the second leaf.
In one embodiment, the second distal end of the second leaf terminates between the first distal end and the first base section of the first leaf.
In one embodiment, the supplemental leaf assembly includes a spacer secured to the first leaf and a third leaf secured to the spacer, for example by one or more rivets or spot welds. The third leaf slidingly engages the second leaf.
In one embodiment, the second distal end of the second leaf terminates between the first distal end and the first base section; the supplemental leaf assembly includes a spacer secured to the first leaf and a third leaf secured to the spacer, the third leaf slidingly engages the second leaf; and the spacer is positioned between the first leaf and the third leaf, the spacer is spaced apart from the second distal end thereby defining a gap between the spacer and the second distal end to accommodate movement of the spacer relative to the second distal end.
In one embodiment, the seal assembly includes a one or more displacement members. Each of the displacement members has a first engagement portion configured to displace a portion of the leaf assembly a predetermined distance. In one embodiment, the each of displacement members has an L-shaped configuration defining a first leg and a second leg. The first leg defines a third base portion that is secured to the diaphragm and the second leg has the engagement portion thereon. The displacement members are arranged to establish a predefined contour of the leaf assembly. The predetermined contour is configured to compensate for movement of the preheater during operation.
In one embodiment, the seal assembly includes a strip (e.g., guard and/or limiter) having fourth base section engaging the second base section such that the second base section is positioned between the first base section and the fourth base section. The strip defines a deflector section extending away from the fourth base section and away from the second leaf.
There is also disclosed herein a preheater assembly. The preheater assembly includes a rotor assembly rotatably mounted on a rotor post and disposed in a housing. The rotor assembly defines diaphragms extending radially from the rotor post to an outer periphery of the rotor assembly. Adjacent pairs of the diaphragms define respective compartments for receiving a heat transfer assembly. Each of the heat transfer assemblies include a plurality of heat transfer sheets stacked upon one another. The housing including a flue gas inlet duct and a flue gas outlet duct for channeling the flow of heated flue gases through the preheater The housing also includes an air inlet duct and an air outlet duct for channeling the flow of combustion air through the preheater. The preheater includes an upper sector plate extending across the housing adjacent to an upper face of the rotor assembly and a lower sector plate extending across the housing adjacent to lower face of the rotor assembly. The upper sector plate extends between and is joined to the flue gas inlet duct and the air outlet duct; and the lower sector plate extends between and is joined to the flue gas outlet duct and the air inlet duct. The upper and lower sector plates, respectively, are joined to one another by a circumferential plate. The upper sector plate and/or the lower sector plate define a leading edge and a trailing edge. One or more of the leading edge and the trailing edge defines a ramped configuration. A seal assembly is positioned on an axial edge of each diaphragm. The seal assembly includes a leaf assembly and a supplemental leaf assembly. The leaf assembly includes a first leaf having a first base section. The first base section defines a first fastening area for securing the first leaf to a diaphragm of the preheater. The first leaf has a first elongate section extending away from the first base section and terminating at a first distal end thereof. The leaf assembly further includes a second leaf that engages a portion of the first leaf. The second leaf has a second base section. The second base section defines a second fastening area for securing the second leaf to the diaphragm. The second leaf has a second elongate section extending away from the second base section and terminating at a second distal end thereof. The supplemental leaf assembly is secured to the first leaf and slidingly engages the second leaf. A portion of the first leaf slidingly engages the leading edge and disengages the trailing edge.
In one embodiment, the second distal end terminates between the first distal end and the first base section.
In one embodiment, the supplemental leaf assembly includes a spacer secured to the first leaf and a third leaf secured to the spacer. The third leaf slidingly engages the second leaf.
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In one embodiment, the first leaf 52, the second leaf 54, the third leaf 62 and/or the fourth leaf 64 are manufactured from an austenitic stainless steel, for example a 301 stainless steel. In one embodiment the first leaf 52, the second leaf 54, the third leaf 62 and/or the fourth leaf 64 are about 0.02 to 0.025 inches thick.
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When the seal assembly rotates about 180 degrees into the area of the sector plate 30A a pressure P1′ (shown on a right hand side of the leaf assembly 50 in
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Through analysis and experimentation, the inventors have surprisingly discovered that as the seal assembly 50 rotates with the rotor assembly 12, the first distal end 52D of the first leaf 52 abruptly and scrapingly engages the leading edge 31L in a scissor-like operation; and abruptly and scrapingly disengages the trailing edge 31T in the scissor-like operation, which causes premature wear of the seal. Contrary to engineering intuition, the inventors have found that the wear is more prominent radially inward towards the rotor post 16.
As prompted by the results of the experimentation and testing, the inventors have modified the sharp leading edge 31L and trailing edge 31T to a ramped configuration as shown in
As a resulted of laboratory test simulations of preheater operation, the inventors have found that the ramped configuration having a 20 degree ramp angle results in a total wear rate of the seal assembly 50 of less than 0.0016 inches per hour at less than 30 percent load operation at locations along the seal assembly between 50 and 150 inches from the axis A; and less than 4×10−4 inches per hour at less than 30 percent load operation at locations along the seal assembly between radially outward of 150 inches from the axis A. While the wear rates are based upon laboratory testing, the inventors expect that they are a reasonable prediction of wear during operation.
Although this invention has been shown and described with respect to the detailed embodiments thereof, it will be understood by those of skill in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed in the above detailed description, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims
1. A seal assembly for a rotary preheater, the seal assembly comprising:
- a leaf assembly comprising: a first leaf having a first base section, the first base section defining a first fastening area for securing the first leaf to a diaphragm of the preheater, the first leaf having a first elongate section extending away from the first base section and terminating at a first distal end thereof; a second leaf engaging a portion of the first leaf and having a second base section, the second base section defining a second fastening area for securing the second leaf to the diaphragm, the second leaf having a second elongate section extending away from the second base section and terminating at a second distal end thereof; and a supplemental leaf assembly secured to the first leaf and slidingly engaging the second leaf.
2. The seal assembly of claim 1, wherein the second distal end terminates between the first distal end and the first base section.
3. The seal assembly of claim 1, wherein the supplemental leaf assembly comprises a spacer secured to the first leaf and a third leaf secured to the spacer, the third leaf slidingly engaging the second leaf.
4. The seal assembly of claim 1, wherein:
- the second distal end terminates between the first distal end and the first base section;
- the supplemental leaf assembly comprises a spacer secured to the first leaf and a third leaf secured to the spacer, the third leaf slidingly engaging the second leaf; and
- wherein the spacer is positioned between the first leaf and the third leaf, the spacer being spaced apart from the second distal end thereby defining a gap between the spacer and the second distal end to accommodate movement of the spacer relative to the second distal end.
5. The seal assembly of claim 1, further comprising at least one displacement member, the at least one displacement member having a first engagement portion configured to displace a first portion of the leaf assembly a first distance and the at least one displacement member having a second engagement portion configured to displace a second portion of the leaf assembly a second distance, wherein the first distance and the second distance are different.
6. The seal assembly of claim 5, wherein each of the at least one displacement member has an L-shaped configuration defining a first leg and a second leg, the first leg defining a third base portion that is configured to be secured to the diaphragm and the second leg comprising one of the first engagement portion and the second engagement portion.
7. The seal assembly of claim 5, wherein the at least one displacement member is arranged to establish a predefined contour of the leaf assembly.
8. The seal assembly of claim 7, wherein the predetermined contour is configured to compensate for movement of the preheater during operation.
9. The seal assembly of claim 3, wherein the spacer protrudes outwardly from at least one of the first leaf and the second leaf.
10. The seal assembly of claim 1, further comprising a strip having fourth base section engaging the second base section, the second base section being positioned between the first base section and the fourth base section and the strip defining a deflector section extending away from the fourth base section and away from the second leaf.
11. The seal assembly of claim 1, further comprising a bar aligned with a portion of the first base section and the second base section.
12. The seal assembly of claim 3, wherein the spacer comprises at least one of a hardened material, a weld, a rivet, a leaf and a bend in one of the first leaf and the third leaf.
13. A preheater assembly comprising:
- a rotor assembly rotatably mounted on a rotor post and disposed in a housing, the rotor assembly defining diaphragms extending radially from the rotor post to an outer periphery of the rotor assembly, adjacent pairs of the diaphragms defining respective compartments for receiving a heat transfer assembly, each of the heat transfer assemblies including a plurality of heat transfer sheets stacked upon one another, the housing including a flue gas inlet duct and a flue gas outlet duct for channeling the flow of heated flue gases through the preheater, the housing including an air inlet duct and an air outlet duct for channeling the flow of combustion air through the preheater, the preheater including an upper sector plate extending across the housing adjacent to an upper face of the rotor assembly and a lower sector plate extending across the housing adjacent to lower face of the rotor assembly, the upper sector plate extends between and is joined to the flue gas inlet duct and the air outlet duct, the lower sector plate extends between and is joined to the flue gas outlet duct and the air inlet duct, the upper and lower sector plates, respectively, are joined to one another by a circumferential plate;
- at least one of the upper sector plate and the lower sector plate defining a leading edge and a trailing edge, and wherein at least one of the leading edge and the trailing edge defines a ramped configuration; and
- a seal assembly positioned on an axial edge of each diaphragm, the seal assembly comprising:
- a leaf assembly comprising: a first leaf having a first base section, the first base section defining a first fastening area for securing the first leaf to a diaphragm of the preheater, the first leaf having a first elongate section extending away from the first base section and terminating at a first distal end thereof; a second leaf engaging a portion of the first leaf and having a second base section, the second base section defining a second fastening area for securing the second leaf to the diaphragm, the second leaf having a second elongate section extending away from the second base section and terminating at a second distal end thereof; and a supplemental leaf assembly secured to the first leaf and slidingly engaging the second leaf; and wherein a portion of the seal assembly engages the leading edge and disengages the trailing edge.
14. The preheater of claim 13, wherein the second distal end terminates between the first distal end and the first base section.
15. The preheater of claim 13, wherein the supplemental leaf assembly comprises a spacer secured to the first leaf and a third leaf secured to the spacer, the third leaf slidingly engaging the second leaf.
Type: Application
Filed: Aug 18, 2015
Publication Date: Feb 23, 2017
Applicant: ARVOS INC. (Wellsville, NY)
Inventor: Jeffrey O'Boyle (Wellsville, NY)
Application Number: 14/829,210