Patent Application
20050121263
This invention relates to a system and method for circulating and/or cooling lubricant associated with a rotating member and a stationary member.
Conventional lubricating arrangements associated with rotary machines often utilize lubricant that has not been properly circulated, thus resulting in a diminished useful life of the rotary machine due to improper lubrication. It is therefore desirable to provide circulated lubricant to the rotary machine such that the lubricant provides greater protection against the general wear and tear that occurs within the rotary machine. However, due to the increased cost and space constraints associated with providing pumps to circulate lubricant in a rotary machine, it is difficult to provide circulated lubricant to the rotary machine in an economical and efficient manner.
Referring to
The bearing assembly 10 includes a bearing case 14, which is supported in any conventional manner by a bearing support 16. A pair of fixed annular labyrinth seals 18, 20 are disposed between the bearing case 14 and the shaft 12 to prevent leakage of lubricant in both axial directions of the shaft beyond the bearing case. The labyrinth seals 18, 20 are affixed to the bearing case 14 in any conventional manner such as via annularly-spaced bolts (not shown). A pair of axially-spaced annular flanges 24, 26 of the bearing case 14 extend around a journal bearing 28 of the bearing assembly 10 to position the bearing adjacent the shaft 12. The bearing 28 is affixed to the flanges 24, 26 in any conventional manner including via annularly-spaced bolts (not shown). A small annular clearance 29 is defined at the interface between the bearing 28 and the shaft 12.
The bearing 28 is designed for ring-oiled and/or pressure lubrication, and as such, includes a circumferentially formed slot 30 for accommodating an oil ring 32. The width of the slot 30 is slightly greater than the width of the oil ring 32 such that the oil ring is maintained in substantially the same axial position relative to the bearing case 14. A radially-extending pressure lube feed port 34 is formed through the bearing 28 and is axially spaced from the slot 30. The axially-spaced flanges 24, 26 of the bearing case 14 define a circumferential slot 36 (
A portion of the oil ring 32 extends through the slot 30 in contact with the shaft 12. The oil ring 32 has a diameter that is greater than that of the shaft and is eccentrically positioned relative to the shaft so that a portion of the ring extends into a sump 38 defined in the case 14. The oil ring 32 is in a light frictional engagement with the shaft 12 so that rotation of the shaft 12 causes rotation of the oil ring 32 about its axis at a speed that is lower than that of the shaft. As a result, rotation of the shaft causes the oil ring 32 to rotate through, and draw lubricant from the sump 38 so that a film of oil accumulates on the oil ring. The lubricant drawn from the sump 38 by the oil ring 32 is delivered to the clearance 29 and is distributed in a manner to be described.
As better shown in
The above arrangement defines a closed-loop circulation path P1 extending from the sump 38, to the oil ring 32, through the axial feed slot 42, through the clearance 29, through the radial pressure lube port 34, through the conduit 40, and back to the sump.
In operation, rotation of the shaft 12 causes rotation of the oil ring 32, which dips into the sump 38 to draw lubricant from the sump causing a thin lubricant film to form on the inner circumferential surface of the oil ring 32. This lubricant is delivered from the oil ring 32, via the slot 30, to the lubricant feed slot 42 where the lubricant collects. Continual collection of lubricant in the lubricant feed slot 42 causes lubricant to overflow the slot, and pass from the slot, through that portion of the clearance 29 extending between the slot and the port 34, and to the port. This latter flow is promoted by the pressure generated by rotation of the shaft 12 that causes a differential in the relatively high pressure in the clearance 29 and the relatively low atmospheric pressure in the conduit 40. The lubricant thus enters the conduit 40 and flows down the conduit to the lower portion of the sump 38, thereby completing the circulation of this portion of the lubricant through the path P1.
It is understood that while a portion of the lubricant follows the circulation path P1 as described above, another portion of the lubricant drawn from the sump 38 generally lubricates the interface between the bearing 28 and the shaft 12, while yet another portion of the lubricant drawn from the sump 38 spills over the oil ring slot 30 and returns to the lubricant sump without having followed the circulation path P1 or provided general lubricating functions.
Thus, by utilizing the pressure generated between the shaft 12 and the bearing 28, the above-described system effectively circulates lubricant through the bearing assembly 10 without having to employ costly and bulky pumps. Furthermore, the lubricant in the sump 38 is mixed with lubricant that is circulated through the bearing 28. Thus, problems such as stagnation of lubricant in lower portions of the sump 38 are effectively avoided and a majority of the lubricant in the lubricant sump is circulated rather than only a top layer of lubricant.
The embodiment of
In this embodiment, an external cooler 52 is provided for cooling the lubricant, and a conduit 62 is provided for circulating lubricant from the clearance 29 to the cooler 52. In the latter context it is understood that, although not shown in
The cooler 52 is of conventional design, and, as such, includes an outer annular chamber 64 that contains cooling water and an inner reservoir portion 66 for receiving the lubricant. A conduit 68 connects the cooler 52 to the lower portion of the sump 50.
Thus, a closed-loop lubricant circulation path P2 is defined that extends from the sump 50 to the oil ring 32, from the oil ring through the clearance 29, through the conduit 62, through the cooler 52, through the conduit 68, and back to the sump 50.
In operation, lubricant is circulated from the sump 50 to the clearance 29, via the oil ring 32, in the same manner as described with reference to the embodiment of
The embodiment of
A bearing assembly 10′, identical to the bearing assembly 10, is axially displaced from the bearing assembly 10. The bearing assembly 10′ includes a bearing 28′ surrounding the shaft 12 and defining a clearance (not depicted) and an oil ring 32′ positioned on the shaft. The remaining portions of the bearing assembly 10′ have been omitted in the interest of clarity and a sump 82 is defined in the case corresponding to the bearing assembly 10′.
In this embodiment, a single reservoir 84 is provided, and a conduit 86, depicted schematically in the interest of clarity, is provided for circulating lubricant from the clearance 29 to the sump 82. A conduit 88, also depicted schematically, is provided for circulating lubricant from the clearance associated with bearing assembly 10′ to the sump 82. It is understood that, although not shown in
A conduit 90 connects the sump 82 and the reservoir 84, with the end of the conduit 90 that extends into the sump 82 terminating at a sufficient height to act as a standpipe, thereby maintaining the lubricant level in the sump 82 at a greater height (represented by H1) than the lubricant levels in the reservoir 84 and the sump 80.
A conduit 92 connects the sump 80 and the reservoir 84, with the end of the conduit 92 that extends into the reservoir 84 terminating at a sufficient height to act as a standpipe so that lubricant in the reservoir rising above the end of the conduit 92 will enter the conduit and circulate to the sump 80. The end of the conduit 92 that terminates in the sump 80 has a substantially equivalent height as the end of the same conduit that terminates in the reservoir 84, thereby maintaining substantially equivalent lubricant levels in the reservoir and the sump 80 for reasons to be described. Thus, the above-described arrangement defines a closed-loop lubricant circulation path P3 generally extending from the sump 80, to the oil ring 32, through the clearance 29, through the conduit 86, through the sump 82, through the conduit 90, through the reservoir 84, through the conduit 92, and back to the sump 80.
In operation, lubricant is circulated from the sump 80 to the clearance 29 between the shaft 12 and the bearing 28 in the same manner as described with reference to the embodiment of
Lubricant circulates from the sump 82 to the clearance associated with bearing assembly 10′, via the oil ring 32′, in the same manner as described with reference to
When the lubricant level in the sump 82 rises above the end of the conduit 90 that terminates in the sump 82, lubricant enters the conduit 90 and circulates to the reservoir 84, causing the lubricant level of the reservoir 84 to rise. When the lubricant level in the reservoir 84 rises above the end of the conduit 92 that terminates in the reservoir, the lubricant enters the conduit 92 and circulates to the sump 80 of the bearing assembly 10. As the ends of the conduit 92 terminate at substantially the same height, gravity causes the lubricant levels in the reservoir 84 and the sump 80 to seek the same level. Thus, the lubricant circulates from the reservoir 84 to the sump 80, thereby completing circulation of the lubricant through the closed-loop lubricant circulation path P3.
By utilizing the single external reservoir 84 to accommodate a lubricant circulation system between the two bearing assemblies 10, 10′, the cost and size restraints normally associated with using one reservoir per bearing assembly are effectively eliminated. Furthermore, the extent of the circulation of the lubricant through the above-described arrangement ensures proper circulation of the lubricant without the use of a pump, thereby increasing the useful life of the lubricant, which in turn, reduces the wear and tear on the bearing assemblies 10, 10′.
It is understood that several variations may be made in the foregoing without departing from the scope of the invention. For example, although described with reference to a turbine shaft, the lubricant circulation system according to the present invention may be applied to any arrangement involving a rotating member and a stationary member. Moreover, the cooler 52 of the embodiment of
Moreover, while it has been described that pressurization of the lubricant promotes flow of the lubricant in the above-described circulation systems, it will be understood that gravity may also assist in the flow of lubricant depending on the physical location of the various components defining the flow paths.
Furthermore, references to specific structure of various elements of the bearing assemblies and the external cooler and reservoir are meant for example purposes only. For example, various types of seals may be substituted for the labyrinth seals 18, 20 and the cooler 52 may alternatively employ cooling coils for cooling the lubricant passing therethrough. Still further, the bearing assemblies 10, 10′ may be any type of ring-oiled bearing assemblies.
Moreover, the conduits in the above-described lubricant circulation systems are not limited to a specific arrangement, and they may be attached to the various bearing assemblies in any conventional manner. Furthermore, in some embodiments, the conduits may be removed. Still further, the lubricant feed slot 42 may lead directly to the pressure lube feed port 34 (
Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures.
