EXHAUSTER FAN BEARING ASSEMBLY AND COOLING SYSTEM FOR PULVERIZER
An exhauster fan bearing assembly for a pulverized solid fuel firing system includes a pedestal housing having an opening at a top portion, the pedestal housing defining an interior space with access thereto through the opening; a bearing housing disposed at the top portion of the pedestal housing, the bearing housing having first and second openings disposed at opposite ends of the bearing housing; first and second bearing assemblies disposed at the first and second openings, respectively; a shaft extending through the bearing housing via the first and second openings, the shaft rotatable about a shaft rotational axis via the first and second bearing assemblies; and a sump housing operably coupled to a bottom of the bearing housing. The sump housing extends through the opening and into the interior space of the pedestal housing. The sump housing defines a reservoir for a lubricant in fluid communication with the first and second bearing assemblies.
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This invention relates to an exhauster employable in solid fuel pulverizing and filing systems for fossil fuel furnaces, and more specifically, to an exhauster fan bearing assembly and cooling system for such solid fuel pulverizing and firing systems.
BACKGROUNDThree basic types of solid fuel pulverizer firing systems find common use. These are the direct-fired system, the semi-direct fired system and the bin storage system. The simplest and most commonly used of these three systems, and the one to which the present invention is directed, is the direct-fired system in which solid fuel, e.g., coal, is fed in a suitable manner along with hot gases to a pulverizer. The solid fuel is simultaneously ground and dried within the pulverizer. The drying of the solid fuel is effected by the hot gases as the latter sweep through the pulverizer. As the hot gases sweep through the pulverizer they are cooled and humidified by means of the evaporation of the moisture contained in the solid fuel. Often, an exhauster is employed for purposes of removing the hot gases and the entrained fine solid fuel particles, i.e., the solid fuel that has been ground within the pulverizer, from the pulverizer. Moreover, this exhauster, when so employed, is located on the discharge side of the pulverizer and is operative to effect the delivery of the mixture of hot gases and entrained fine solid fuel particles to a fossil fuel furnace.
One prior art form of such a direct-fired solid fuel pulverizer firing system is depicted in U.S. Pat. No. 3,205,843 entitled “Pulverized Coal Firing System”, and reproduced in
A prior art form of a typical bearing housing assembly 317 of an exhauster for a solid fuel pulverizer firing system is depicted in
The speed (e.g., approximately 900 rpm) at which the fan shaft 334 rotates is moderate for the bearings 366 specified and should not adversely affect bearing life. The load on the bearings 366 including the radial weights of the overhung fan and other component weights, plus a small thrust load due to differential pressure on the fan, the drive shaft 334 and coupling are very small compared to the dynamic load capacity of the bearings 366.
However, the relatively small oil reservoir and small convective surface area of the housing 360 are not capable of dissipating the desired amount of heat generated by the bearings 366 and the heat conducted through the shaft 334 from the hot air supply to the fan casing. This causes an increase in the operating temperature of the oil 370 in the sump and in the bearing operating temperatures. The increased oil and bearing operating temperatures can be high enough to result in inadequate lubricant film separation of the bearing races and rollers, e.g., inadequate elastohydrodynamic (EHL) lubrication, thus resulting in a shortened lifespan of the bearings and lubricant.
Although solid fuel pulverizer firing systems constructed in accordance with the prior art to which reference has been made heretofore have been demonstrated to be operative for the purpose for which they have been designed, there has nevertheless been evidenced in the prior art a need for such solid fuel pulverizer firing systems to be further improved, and more specifically, a need for the exhauster employed therein to be improved. A limiting factor insofar as the operating efficiency of exhausters is concerned has heretofore been the need to facilitate cooling of the lubricant and bearings of the fan assembly. To this end, a need has thus been evidenced in the prior art for a new and improved solid fuel pulverizer firing system, and more specifically for a new and improved exhauster fan bearing assembly for such solid fuel pulverizer firing systems that would ensure proper cooling of the bearings and lubricant, thus requiring relatively less maintenance than known exhausters.
SUMMARYAccording to the aspects illustrated herein, there is provided an exhauster fan bearing assembly for a pulverized solid fuel firing system. The exhauster fan bearing assembly includes a pedestal housing having an opening at a top portion, the pedestal housing defining an interior space with access thereto through the opening; a bearing housing disposed at the top portion of the pedestal housing, the bearing housing having first and second openings disposed at opposite ends of the bearing housing; first and second bearing assemblies disposed at the first and second openings, respectively; a shaft extending through the bearing housing via the first and second openings, the shaft rotatable about a shaft rotational axis via the first and second bearing assemblies; and a sump housing operably coupled to a bottom of the bearing housing. The sump housing extends through the opening and into the interior space of the pedestal housing. The sump housing defines a reservoir for a lubricant in fluid communication with the first and second bearing assemblies.
According to the other aspects illustrated herein, there is provided an exhauster for a pulverized solid fuel firing system. The exhauster includes a housing; an exhauster fan for exhausting coal through an exhauster fan housing, the exhauster fan being mountable within the housing on a shaft rotatable about a shaft rotational axis and the housing having an inlet generally aligned with the shaft rotational axis such that coal entering the housing through the inlet contacts the rotating exhauster fan and is redirected thereby along a radial outlet path, the exhauster fan including a plurality of blades; and an exhauster fan bearing assembly. The exhauster fan bearing assembly includes a pedestal housing having an opening at a top portion, the pedestal housing defining an interior space with access thereto through the opening; a bearing housing disposed at the top portion of the pedestal housing, the bearing housing having first and second openings disposed at opposite ends of the bearing housing; first and second bearing assemblies disposed at the first and second openings, respectively, the shaft extending through the bearing housing via the first and second openings, the shaft rotatable about the shaft rotational axis via the first and second bearing assemblies; and a sump housing operably coupled to a bottom of the bearing housing. The sump housing extends through the opening and into the interior space of the pedestal housing. The sump housing defines a reservoir for a lubricant in fluid communication with the first and second bearing assemblies.
The above described and other features are exemplified by the following figures and detailed description.
Referring now to the figures, which are exemplary embodiments, and wherein the like elements are numbered alike:
Referring now to the figures, and more particularly to
Considering first the furnace 12, it is within the furnace 12 that in a manner well known to those skilled in this art combustion of the pulverized solid fuel and air is initiated. To this end, the pulverized solid fuel and air is injected into the furnace 12 through a plurality of burners 18, which are schematically depicted in
The hot gases that are produced from construction of the pulverized solid fuel and air rise upwardly in the furnace 12. During the upwardly movement thereof in the furnace 12, the hot gases in a manner well-known to those skilled in the art give up heat to the fluid passing through the tubes 20, which are schematically depicted in
A description of the mode of operation of the solid fuel pulverizer firing system 10 will be described with reference to
A more detailed description of the exhauster fan assembly 26 now follows with reference to
The exhauster fan 32 includes a plurality of blades 42 and a hub 44. The hub 44 has an outer surface 46, a free end 48, and a bore 50 for receiving therein the free end 52 of the shaft 34 in an orientation in which the free end 52 of the shaft 34 and the free end 48 of the hub 44 are oriented in the same axial direction relative to the shaft rotational axis SRA. The outer surface 46 of the hub 44 is radially outwardly spaced from the bore 50 of the hub 44 and the blades 32 are mounted to outer surface 46 of the hub 44 at uniform angular spacings therearound and project radially outwardly therefrom.
The bearing housing 60 includes first and second openings 67 and 69 disposed at opposite ends of the bearing housing 60. First and second bearing assemblies 64 are disposed at the first and second openings 67, 69, respectively. The opposite end of the free end 52 of the shaft 34 extends through the bearing housing 60 and through the first and second openings 67 and 69. The shaft 34 is rotatable about a shaft rotational axis SRA via the first and second bearing assemblies 64. In an exemplary embodiment as illustrated, the first and second bearing assemblies each include a fan shaft bearing 66 and a bearing cap 68.
A sump housing 80 is operably coupled to a bottom of the bearing housing 60. The sump housing 80 extends through the opening 63 and into the interior space 65 of the pedestal housing 62. The sump housing 80 defines a reservoir for a lubricant (e.g., oil 70) in fluid communication with the first and second bearing assemblies 64.
In exemplary embodiments, the sump housing 80 is defined by a first end of a wall 82 extending substantially perpendicular from a base 84 of the sump housing 80 and defining a reservoir for the oil 70. A mounting flange 86 extends substantially perpendicular from an opposite second end of the wall 82 and is substantially parallel to base 84. The mounting flange 86 includes a plurality of mounting apertures to receive corresponding mechanical fasteners 88 to fasten the sump housing 80 to the bearing housing 60. In exemplary embodiments, the mechanical fasteners 88 include threaded fasteners, for example, but are not limited thereto. The sump housing 80 is retrofitable to an existing bearing housing 360 as illustrated in
Referring again to
An oil level indicated by reference numeral 90 is observed by sight gauges 92 (only one shown) on opposite sides of the housing 60. The oil level 90 is maintained at approximately the centerline of the lowest roller in each of the bearings 66. However, there are a pair of different bearings 66 used in the assembly, and the position of their respective lowest rollers may vary. Therefore, the oil level 90 is set at the higher of the two lowest roller centerline positions. This oil level 90 is intended to provide good lubrication conditions for the bearings 66, prevent excessive heat generation due to lubricant viscous shear effects and oil leakage out of the labyrinth-type, housing end caps 68.
Referring now to
The external cooling system 200 includes a cooling medium (not shown) in thermal communication with the lubricant (e.g., oil 70) in the sump housing 80 to remove heat from the lubricant, thereby maintaining a lower temperature of the lubricant to lubricate the bearings 66. The external cooling system 200 includes one tube 202 within the sump housing 80. The single tube is coiled and includes a tube inlet 204 at a first end and a tube outlet 206 at an opposite second end. In alternative exemplary embodiments, an array of tubes 202 is contemplated within the sump housing. In an exemplary embodiment, the cooling medium includes an on-site water source. The on-site water source provides cool water to the tube inlet 204 and heated water is returned to the on-site water source via tube outlet 206.
The arrangements disclosed in
The present invention having the improved bearing housing, as in the above described exemplary embodiments, incorporates a larger oil sump attached to the existing bearing housing and occupies the open space in the housing pedestal housing directly beneath the bearing housing. The new oil sump provides increased oil capacity and convective surface area to dissipate the heat generated during exhauster fan operation. It also allows for the addition of an optional water cooling system, for example, if desired or needed. In an exemplary embodiment, the optional water cooling system may be an array of water tubes within the larger oil sump, used to remove heat from the oil using an on-site water source as the cooling liquid.
The larger volume of oil in the enlarged sump increases the time it takes before the oil and bearings reach an undesirably high operating temperature, thus allowing more heat to be absorbed and time for the heat to be dissipated. In addition to this sump wall-to-air convection method, the oil-to-water convection method from a system of at least one submerged cooling tube can carry away heat internal to the sump. The amount of heat removed by the water-cooled tubing depends on the tube surface area and the flow rate and temperature of the water that is circulated. These factors can be selected to optimize heat removal from the oil for the desired end purpose.
While the invention has been described with reference to various exemplary embodiments, it will be understood by those skilled 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, many 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 embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims
1. An exhauster fan bearing assembly for a pulverized solid fuel firing system, comprising:
- a pedestal housing having an opening at a top portion, the pedestal housing defining an interior space with access thereto through the opening;
- a bearing housing disposed at the top portion of the pedestal housing, the bearing housing having first and second openings disposed at opposite ends of the bearing housing;
- first and second bearing assemblies disposed at the first and second openings, respectively;
- a shaft extending through the bearing housing via the first and second openings, the shaft rotatable about a shaft rotational axis via the first and second bearing assemblies; and
- a sump housing operably coupled to a bottom of the bearing housing, the sump housing extending through the opening and into the interior space of the pedestal housing, the sump housing defining a reservoir for a lubricant in fluid communication with the first and second bearing assemblies.
2. The exhauster fan bearing assembly of claim 1, wherein the first and second bearing assemblies each include a fan shaft bearing and a bearing cap.
3. The exhauster fan bearing assembly of claim 2, wherein each fan shaft bearing includes a plurality of rollers, and a level of the lubricant in the sump housing extends substantially to a centerline of a lowest roller of the rollers in each fan shaft bearing.
4. The exhauster fan bearing assembly of claim 2, wherein each bearing cap includes a labyrinth-type housing end cap configured to prevent leakage of the lubricant from the first and second openings of the bearing housing.
5. The exhauster fan bearing assembly of claim 1, wherein the sump housing is retrofitable to an existing bearing housing to increase lubricant capacity and increase a convective surface area for cooling the lubricant.
6. The exhauster fan bearing assembly of claim 1, further comprising an external cooling system having a cooling medium in thermal communication with the lubricant to remove heat from the lubricant.
7. The exhauster fan bearing assembly of claim 6, wherein the external cooling system includes one tube or an array of tubes within the sump housing.
8. The exhauster fan bearing assembly of claim 7, wherein the cooling medium includes an on-site water source.
9. The exhauster fan bearing assembly of claim 1, wherein the sump housing includes a mounting flange extending substantially perpendicular from a wall defining the reservoir, the flange including a plurality of mounting apertures to receive mechanical fasteners to fasten the sump housing to the bearing housing using mechanical fasteners.
10. The exhauster fan bearing assembly of claim 9, wherein the mechanical fasteners include threaded fasteners.
11. An exhauster for a pulverized solid fuel firing system, comprising:
- a housing;
- an exhauster fan for exhausting coal through an exhauster fan housing, the exhauster fan being mountable within the housing on a shaft rotatable about a shaft rotational axis and the housing having an inlet generally aligned with the shaft rotational axis such that coal entering the housing through the inlet contacts the rotating exhauster fan and is redirected thereby along a radial outlet path, the exhauster fan including a plurality of blades; and
- an exhauster fan bearing assembly, comprising: a pedestal housing having an opening at a top portion, the pedestal housing defining an interior space with access thereto through the opening; a bearing housing disposed at the top portion of the pedestal housing, the bearing housing having first and second openings disposed at opposite ends of the bearing housing; first and second bearing assemblies disposed at the first and second openings, respectively, the shaft extending through the bearing housing via the first and second openings, the shaft rotatable about the shaft rotational axis via the first and second bearing assemblies; and a sump housing operably coupled to a bottom of the bearing housing, the sump housing extending through the opening and into the interior space of the pedestal housing, the sump housing defining a reservoir for a lubricant in fluid communication with the first and second bearing assemblies.
12. The exhauster of claim 11, wherein the first and second bearing assemblies each include a fan shaft bearing and a bearing cap.
13. The exhauster of claim 12, wherein each fan shaft bearing includes a plurality of rollers, and a level of the lubricant in the sump housing extends substantially to a centerline of a lowest roller of the rollers in each fan shaft bearing.
14. The exhauster of claim 12, wherein each bearing cap includes a labyrinth-type housing end cap configured to prevent leakage of the lubricant from the first and second openings of the bearing housing.
15. The exhauster claim 11, wherein the sump housing is retrofitable to an existing bearing housing to increase lubricant capacity and increase a convective surface area for cooling the lubricant.
16. The exhauster of claim 11, further comprising an external cooling system having a cooling medium in thermal communication with the lubricant to remove heat from the lubricant.
17. The exhauster of claim 16, wherein the external cooling system includes one tube or an array of tubes within the sump housing.
18. The exhauster of claim 17, wherein the cooling medium includes an on-site water source.
19. The exhauster of claim 11, wherein the sump housing includes a mounting flange extending substantially perpendicular from a wall defining the reservoir, the flange including a plurality of mounting apertures to receive mechanical fasteners to fasten the sump housing to the bearing housing using mechanical fasteners.
20. The exhauster of claim 19, wherein the mechanical fasteners include threaded fasteners.
Type: Application
Filed: Jun 7, 2007
Publication Date: Dec 11, 2008
Applicant: ALSTOM TECHNOLOGY LTD (Baden)
Inventors: Jeffrey A. Case (East Granby, CT), Mark A. Fuller (Canton, CT), Daniel J. Hayden, JR. (Enfield, CT)
Application Number: 11/759,474
International Classification: F23K 3/00 (20060101);