Circumferential flow channel for carbon seal runner cooling

A fluid cooled seal arrangement for a gas turbine engine including a first sealing element coupled to a mechanical housing of the engine, and a second sealing element connected to a shaft rotatable within the housing. The first and second sealing elements are arranged radially adjacent to one another to form a rubbing interface therebetween. A lubrication system for delivering cooling fluid to the second sealing element through a passageway arranged along the rotating shaft. The cooling fluid is discharged through a plurality of openings formed in one end of the passageway. During normal operation of the engine the centrifugal force from the rotation of the shaft flings the oil radially outward to a channel formed on the underside of the second sealing element. The channel receives the cooling fluid therein, and allows for the escape of the cooling fluid onto the underside of the second sealing element to provide a uniform thickness of cooling fluid thereon. A uniform film of cooling fluid will result in the more uniform transfer of heat from the second sealing element.

BACKGROUND OF THE INVENTION 
The present invention relates generally to the design and construction of 
seal systems useful in a gas turbine engine. More particularly, the 
present invention has one application with a carbon seal system having a 
rotating seal runner with a flow channel for uniformly distributing 
cooling fluid. Although the invention was developed for use in a gas 
turbine engine, certain applications may be outside of this field. 
It is well known that a gas turbine engine integrates a compressor and a 
turbine that have components that rotate at extremely high speeds relative 
to each other, and across which there are pressure differentials that make 
the provision of seals for minimizing fluid leakage very important. Prior 
designers of seal systems have generally used a sealing device consisting 
of a plurality of arcuate carbon material segments arranged to form a 
stationary carbon ring that forms a rubbing interface with a rotating seal 
runner. 
The rubbing interface between the rotating seal runner and the carbon ring 
minimizes or prevents the leakage of fluid through the seal, however if 
the heat generated by the rubbing interface is not adequately dissipated 
the resulting fluid leakage at the seal interface may become excessive. A 
failure to control the temperature of the rotating seal runner can result 
in thermal distortion of the seal runner and a corresponding degradation 
of the seal's performance that is manifested by an excessive fluid 
leakage. 
A carbon seal system requires the precise geometric fit between the 
stationary carbon ring and the rotating seal runner to assure that an 
intimate rubbing interface is obtained between the mating components. The 
rubbing interface between the mating components is critical to the 
performance of the seal, and certain tolerances associated with the seal 
components are measured in millionth of an inch. In order to maintain the 
precision geometric fit between the mating components of the rubbing 
interface, prior designers of carbon seal systems have typically utilized 
a fluid cooling medium to extract excessive heat from the seal runner. 
The conventional technique utilized to minimize the overheating of the seal 
interface includes the delivery of a cooling fluid onto the underside of 
the rotating seal runner. One approach to delivering the cooling fluid 
onto the underside of the rotating seal runner is to spray the cooling 
fluid from a stationary nozzle that is positioned proximate the seal 
runner. The relative motion between the rotating seal runner and the 
stationary nozzle causes a uniform film of cooling fluid to be deposited 
on the seal runner that results in a uniform extraction of thermal energy 
from the runner. Stationary nozzles provide a consistently even film of 
cooling fluid on the underside of the rotating seal runner, however their 
applicability on many gas turbine engines is limited by physical 
constraints that prevent the nozzle from being located proximate the seal 
runner. 
A second approach to delivering the cooling fluid utilizes a rotating 
distributor to deliver the cooling fluid onto the underside of the 
rotating seal runner. The rotating distributor is typically affixed to the 
seal runner, and a steady stream of cooling fluid is delivered through a 
central passageway in the rotating distributor to the underside of the 
seal runner. A series of openings in the rotating distributor dispense the 
cooling fluid onto the seal runner. Inherently, because of the absence of 
relative motion between the distributor and the seal runner there is an 
inevitable uneven distribution of cooling fluid on the underside of the 
seal runner. Prior designs have utilized a greater quantity of openings 
formed at one end of the central passageway in order to produce a more 
even distribution of cooling fluid on the underside of the rotating seal 
runner. 
It is generally well known that a carbon seal system having a rotating 
distributor must include a large quantity of openings in order to deliver 
an even film of cooling fluid on the underside of the seal runner. If this 
design parameter is not satisfied, an uneven film of cooling fluid is 
distributed across the seal runner, which causes an uneven extraction of 
heat. 
This uneven extraction of heat can lead to the warping and deformation of 
the seal runner that will result in gaps between the seal runner and the 
carbon sealing element. Any voids, openings, or gaps in the rubbing 
interface of the seal system will cause excessive fluid leakage through 
the seal. A carbon seal system design having a large quantity of cooling 
fluid dispensing openings can be utilized, however as the quantity of 
openings increase there arises significant complexity in interconnecting 
the components. Manufacturing concerns will serve to limit the quantity of 
cooling fluid dispensing openings that can be utilized, this in turn will 
effect the evenness of the distribution of cooling fluid on the seal 
runner and the associated heat transfer therefrom. 
Even with a variety of early designs there remains a need for an improved 
sealing system. The present invention satisfies this need in a novel and 
unobvious way. 
SUMMARY OF THE INVENTION 
One embodiment of the present invention contemplates a fluid cooled seal 
arrangement. The apparatus comprises: a mechanical housing; a shaft 
rotatably mounted within the housing; a first sealing element coupled to 
the housing; a second sealing element connected to the shaft; the second 
sealing element arranged adjacent to the first sealing element to form 
rubbing interface therebetween; a channel on the radially inward side of 
the second sealing element for receiving cooling fluid therein and 
allowing escape of received cooling fluid at a plurality of points along 
its length and preferably uniformly along its entire length; and a 
passageway along the shaft for delivering cooling fluid to the channel for 
cooling the second sealing element. 
One object of one form of the present invention is to provide an improved 
carbon seal system for a gas turbine engine. 
Related objects and advantages of the present invention will be apparent 
from the following description.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
For the purposes of promoting an understanding of the principles of the 
invention, reference will now be made to the embodiment illustrated in the 
drawings and specific language will be used to describe the same. It will 
nevertheless be understood that no limitation of the scope of the 
invention is thereby intended, such alterations and further modifications 
in the illustrated device, and such further applications of the principles 
of the invention as illustrated therein being contemplated as would 
normally occur to one skilled in the art to which the invention relates. 
Referring to FIG. 1, there is illustrated a gas turbine engine 10 which 
includes a compressor 11, a combustor 12, and a power turbine 13. The 
three components have been integrated together to produce an aircraft 
flight propulsion engine. One aircraft engine of this general type is 
model AE2100, that is produced by Allison Engine, Inc., of Indianapolis, 
Ind. It is important to realize that there are a multitude of ways in 
which the components could be linked together. Additional compressors and 
turbines could be added, with intercoolers connecting between the 
compressors, and reheat combustion chambers could be added between the 
turbines. Further, a gas turbine engine is equally well suited to be used 
for industrial applications. Historically, there has been widespread 
application of industrial gas turbine engines, such as pumping sets for 
gas and oil transmission lines, electricity generation, and naval 
propulsion. 
With reference to FIGS. 2 and 3, there is illustrated a fragmentary 
sectional view of the gas turbine engine 10 of FIG. 1. A tubular shaft 15 
is rotatably mounted within the gas turbine engine 10 about a longitudinal 
axis Y of the engine 10. The shaft 15 is supported on a plurality of 
bearings that are disposed between the shaft 15 and a rigid housing that 
forms a portion of the engine 10. One of the plurality of bearings is a 
bearing 16 that is coupled to a mechanical housing 17 of the engine 10. 
The volume defined between the shaft 15 and the mechanical housing 17 is a 
sump 18 in which the bearing 16 is disposed. 
The sump 18 functions as a reservoir for cooling fluid that is utilized to 
cool and lubricate the mechanical components of the gas turbine engine 10 
such as bearing 16. An annular barrier 19 is attached to the rear of 
mechanical housing 17, to close one end of the sump 18, and includes a 
plurality of seals which minimize or prevent the leakage of cooling fluid 
between the shaft 15 and the barrier 19. The sump 18 is closed at its 
forward end by a second annular barrier 20 that is affixed to the 
mechanical housing 17. A plurality of seals are disposed between 
mechanical housing 17 and the shaft 15 that is rotatably mounted within 
mechanical housing 17. One of the plurality of seals is a fluid cooled 
seal arrangement 21. In the preferred embodiment the fluid cooled seal 
arrangement 21 is a carbon seal system that includes a stationary 
component and a rotating component. 
The stationary component has a first sealing element 22 that is coupled to 
the mechanical housing 17. While the rotating component has a second 
sealing element 23 that is mechanically connected to the rotating shaft 
15. It is well known that the rotating component of this sealing 
arrangement is known as a seal runner. The first sealing element 22 is 
positioned axially concentric with and radially outward from the second 
sealing element 23. In the preferred embodiment the sealing elements 22 
and 23 are arranged adjacent to each other to form a rubbing interface 
therebetween. A first cylindrical surface 25 is formed on the radially 
inward side of the first sealing element 22, and a second cylindrical 
surface 26 is formed on the radially outward side of the second sealing 
element 23. At least a portion of the cylindrical surfaces.25 and 26 are 
maintained in rubbing contact to form a fluid tight seal at the rubbing 
interface 9. 
The lubrication system, which normally provides cooling fluid under 
pressure to lubricate and cool the moving parts of the engine, such as the 
bearing 16 and the second sealing element 23, delivers its fluid through 
nozzle 27. The cooling fluid is pressurized by a pump (not illustrated) to 
a pressure of about 30 pounds per square inch gage. The pump discharges 
the fluid from the nozzle orifice 28 with sufficient kinetic energy to 
traverse the cavity 8 that is positioned between the nozzle orifice 28 and 
the nut 31. The nozzle 27 is connected to the mechanical housing and is 
disposed within the oil sump 18. In the preferred embodiment the cooling 
fluid is an engine oil having a viscosity that is suited for the high 
temperatures associated with a gas turbine engine 10. The nozzle 27 
includes a discharge orifice 28 which directs the cooling fluid into a 
passageway 29 that is positioned along the tubular shaft 15. In the 
preferred embodiment the passageway 29 has oil flowing through it for use 
as a cooling fluid. Further, before the cooling fluid enters the 
passageway 29 it passes through a pathway 30 in nut 31 and adjacent 
the-bottom side 16a of bearing 16. In an alternate form of the present 
invention the discharge orifice 28 discharges the cooling fluid directly 
into the passageway 29. 
The bearing 16 has an inner race 16b that is retained on the tubular shaft 
15 by the nut 31 that is threaded on the shaft 15. The nut 31 captures the 
inner race 16b of bearing 16, a spacer 32, the second sealing element 23, 
and a pair of other sealing devices 33 and 34 against a shoulder 35 of the 
shaft 15. The spacer 32 and the second sealing element 23 rotate together 
with the tubular shaft 15. 
With reference to FIGS. 3 and 4, the components which comprise the fluid 
cooled seal arrangement 21 will be described in further detail. In the 
preferred embodiment the passageway 29 is formed adjacent the tubular 
shaft 15 between the radial inward cylindrical surface 36 of spacer 32 and 
the circumferential surface 15a of tubular shaft 15. The passageway 29 
provides a pathway for the axial flow of cooling fluid to a substantially 
solid planar surface 38 that forms a portion of the second sealing element 
23. In the preferred embodiment the substantially solid planar surface 38 
extends radially outward from the tubular shaft 15. This planar surface 38 
prevents any further axial flow of the cooling fluid and helps direct the 
fluid to flow in a substantially radial direction. Alternatively, the 
surface may contain contours to aid in the addition of a circumferential 
flow component. In the preferred embodiment a plurality of openings 39 are 
formed on one end of passageway 29 that is disposed adjacent to the 
substantially solid planar surface 38. In an alternate embodiment (not 
illustrated) the openings may be formed at an axial distance from the 
planar surface 38. 
In the preferred embodiment the openings 39 are formed by machining a 
rectangular opening or slot through the cylindrical wall 32a of spacer 32. 
In alternate embodiments the geometric shape of the openings formed in the 
spacer 32 corresponds to other polygons, circular or other geometric 
shapes. In one form of the present invention there are at least four 
openings formed on the passageway. In the preferred embodiment there are 
at least about sixteen openings 39 formed about the circumference of the 
passageway 29. The openings 39 are spaced symmetrically about the 
circumference 29a of the passageway 29. Further, the openings are axially 
aligned and spaced a radial distance from a channel 45 that is machined in 
the second sealing element 23. Alternatively, the channel 45 can be formed 
by any other means which provide the desired geometric relationships. 
The channel 45 is formed on the radially inward side 23a of the second 
sealing element 23 and preferably has an axial width that is about twice 
as wide as its radial depth. The channel 45 extends uninterrupted around 
the second sealing element. It is understood that the geometric 
relationship between the width and depth of the channel 45 will vary 
depending upon other parameters of the seal system, such as the number of 
openings 39 in the passageway, the size and shape of the openings, and the 
volumetric flow rate of the cooling fluid. The channel 45 is designed and 
constructed for receiving cooling fluid therein that has been released 
through the plurality of openings 39 in passageway 29. As the cooling 
fluid exits the openings 39 of passageway 29 it is thrown radially outward 
by centrifugal forces during normal engine operation. 
As the cooling fluid is received in the channel 45 it flows 
circumferentially through the channel until the channel is full. When the 
channel 45 is completely full of cooling fluid it allows the cooling fluid 
to escape at a plurality of points along its length. In the preferred 
embodiment the plurality of points define a continuous line that 
corresponds to the entire circular edge 47 of channel 45. After the 
cooling fluid has escaped from channel 45 it flows across the radially 
inward surface 23a that is formed adjacent the channel 45 of second 
sealing element 23. 
The radially inward surface 23a defines an outwardly sloping surface that 
is axially concentric with the first sealing element 22 and the second 
sealing element 23. This outwardly sloping surface preferably has a slope 
of about two degrees as measured from a reference line parallel to the 
central axis Y of the gas turbine engine 10. See FIG. 3, angle .PHI.. The 
cooling fluid is evenly distributed on the radially inward surface 23a of 
the second sealing element and provides for substantially uniform 
dissipation of thermal energy therefrom. As the cooling fluid is released 
from the second sealing element it is returned to the oil lubrication 
system. 
The second sealing element 23 has an extended portion 50 extending a 
further distance from the first sealing element 22 than the channel 45 is 
located from the first sealing element 22. Extended portion 50 is designed 
to minimize the volume of oil that engages the first sealing element 22. 
In the preferred embodiment the first sealing element 22 includes a carbon 
seal element 51. The carbon seal element 51 defines an annular ring that 
is formed from la plurality of arcuate carbon material segments arranged 
in an abutting relationship. It is important to minimize the volume of 
cooling fluid that reaches the carbon seal element 51 so as to not 
saturate this sealing element with cooling fluid. 
While the invention has been illustrated and described in detail in the 
drawings and foregoing description, the same is to be considered as 
illustrative and not restrictive in character, it being understood that 
only the preferred embodiment has been shown and described and that all 
changes and modifications that come within the spirit of the invention are 
desired to be protected.