U.S. patent application number 13/313988 was filed with the patent office on 2012-04-12 for interdependent lubrication systems.
This patent application is currently assigned to UNITED TECHNOLOGIES CORPORATION. Invention is credited to Jorn A. Glahn, Frederick M. Schwarz.
Application Number | 20120085528 13/313988 |
Document ID | / |
Family ID | 39092073 |
Filed Date | 2012-04-12 |
United States Patent
Application |
20120085528 |
Kind Code |
A1 |
Schwarz; Frederick M. ; et
al. |
April 12, 2012 |
INTERDEPENDENT LUBRICATION SYSTEMS
Abstract
A heat exchange system for use in operating equipment having a
plurality of subsystems in each of which one of a plurality of
working fluids is utilized to provide selected operations with
there being an air and working fluid heat exchanger providing
controlled cooling to cool at least one of the plurality of working
fluids in its corresponding subsystem. In addition, a coupling heat
exchanger is also provided connected to two of the subsystems to
pass there working fluids therethrough, including the subsystem
with the air and working fluid heat exchanger, to allow one of the
connected subsystems to aid in cooling the other.
Inventors: |
Schwarz; Frederick M.;
(Glastonbury, CT) ; Glahn; Jorn A.; (Manchester,
CT) |
Assignee: |
UNITED TECHNOLOGIES
CORPORATION
Hartford
CT
|
Family ID: |
39092073 |
Appl. No.: |
13/313988 |
Filed: |
December 7, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11595185 |
Nov 9, 2006 |
|
|
|
13313988 |
|
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|
Current U.S.
Class: |
165/287 |
Current CPC
Class: |
Y02T 50/60 20130101;
Y02T 50/675 20130101; F02C 7/14 20130101; F05D 2260/205 20130101;
F05D 2270/303 20130101; F05D 2220/76 20130101; Y02T 50/671
20130101; F05D 2220/36 20130101; F01D 25/08 20130101; F01D 25/20
20130101 |
Class at
Publication: |
165/287 |
International
Class: |
F28F 27/00 20060101
F28F027/00 |
Claims
1. A method for cooling lubricating liquid, the method comprising:
flowing a first lubricating liquid through a first conduit of a
first lubrication system having a first heat exchanger; flowing a
second lubricating liquid through a second conduit of a second
lubrication system having a second heat exchanger; sensing
temperature of both the first and second lubricating liquids;
transferring heat from the first lubricating liquid to the second
lubricating liquid via a coupling heat exchanger when the
temperature of the first lubricating liquid exceeds a first
threshold; and transferring heat from the second lubricating liquid
to the first lubricating liquid via the coupling heat exchanger
when the temperature of the second lubricating liquid exceeds a
second threshold.
2. The method of claim 1, and further comprising: cooling turbine
engine parts via the first lubricating liquid; and cooling an
electrical generator via the second lubricating liquid.
3. The method of claim 1, and further comprising: flowing air over
the first heat exchanger to cool the first lubricating liquid; and
flowing air over the second heat exchanger to cool the second
lubricating liquid.
4. The method of claim 3, and further comprising: transferring heat
from the first lubricating liquid to a fuel via a fuel and oil heat
exchanger coupled to the first conduit.
5. The method of claim 4, wherein heat is transferred from the
second lubricating liquid to the first lubricating liquid via the
coupling heat exchanger, from the first lubricating liquid to the
air via the first heat exchanger, and from the first lubricating
liquid to the fuel via the fuel and oil heat exchanger when the
temperature of the second lubricating liquid exceeds the second
threshold.
6. The method of claim 4, wherein the fuel passing through the fuel
and oil heat exchanger does not pass through a heat exchanger
coupled to the second conduit.
7. The method of claim 3, wherein the first heat exchanger is
positioned in a turbine engine fan duct.
8. The method of claim 7, and further comprising: actuating a
movable flap to selectively vary fan airstream flow over the first
heat exchanger as a function of temperature of the second
lubricating liquid.
9. The method of claim 3, wherein the first and second heat
exchangers are positioned in first and second turbine engine fan
ducts, and further comprising: actuating a first movable flap to
selectively open or close at least a portion of one end of the
first turbine engine fan duct to selectively increase or limit fan
airstream flow over the first heat exchanger; and actuating a
second movable flap to selectively open or close at least a portion
of one end of the second turbine engine fan duct to selectively
increase or limit fan airstream flow over the second heat
exchanger.
10. The method of claim 9, and further comprising: at least
partially opening both the first and second movable flaps in
response to one of the first and second lubricating liquids
exceeding the first and second thresholds.
11. The method of claim 1, and further comprising: bypassing the
coupling heat exchanger, via a bypass valve, by at least one of the
first and second lubricating liquids when the temperature of the
first and second lubricating liquids are below the first and second
thresholds, respectively.
12. The method of claim 2, and further comprising: pumping the
first lubricating liquid via a first pump, wherein the first
lubricating liquid flows from the first heat exchanger to the
coupling heat exchanger to a selected one of the turbine engine
parts and the first pump.
13. The method of claim 12, and further comprising: transferring
heat from the first lubricating liquid to a fuel via a fuel and oil
heat exchanger coupled to the first conduit, wherein the first
lubricating liquid flows from a selected one of the turbine engine
parts and the first pump to the fuel and oil heat exchanger to the
first heat exchanger.
14. A method for using a coupling heat exchanger connected in
thermally coupled first and second subsystems having first and
second air and working fluid heat exchangers to cool first and
second working fluids therein at selectively variable rates in
airstreams occurring with uses of operating equipment, the method
comprising: sensing temperature of both the first and second
working fluids; passing the first and second working fluids through
the coupling heat exchanger to transfer heat from the first working
fluid to the second working fluid, and increasing the cooling
provided by the second air and working fluid heat exchanger in
response to temperature of the first working fluid nearing a first
predetermined limit; and passing the first and second working
fluids through the coupling heat exchanger to transfer heat from
the second working fluid to the first working fluid, and increasing
the cooling provided by the first air and working fluid heat
exchanger in response to temperature of the second working fluid
nearing a second predetermined limit; and bypassing the coupling
heat exchanger by at least one of the first and second working
fluids when the temperature of the first and second working fluids
are substantially below the first and second predetermined limits,
respective.
15. The method of claim 14, and further comprising: transferring
heat from the first working fluid to a fuel via a fuel and oil heat
exchanger coupled to the first subsystem.
16. The method of claim 15, wherein the fuel passing through the
fuel and oil heat exchanger does not pass through a heat exchanger
coupled to the second subsystem.
17. The method of claim 14, wherein the first air and working fluid
heat exchanger is positioned in a turbine engine fan duct.
18. The method of claim 17, and further comprising: actuating a
movable flap to selectively vary fan airstream flow over the first
and working fluid heat exchanger as a function of temperature of
the second working fluid.
19. The method of claim 14, and further comprising: cooling turbine
engine parts via the first working fluid; and cooling an electrical
generator via the second working fluid.
20. A method for using a coupling heat exchanger connected in both
of two thereby thermally coupled subsystems in operating equipment
to cool one with the other in each of which subsystems a working
fluid is utilized in providing selected operations where at least
one of those subsystems has an air and working fluid heat exchanger
to cool the working fluid therein at selectively variable rates in
airstreams occurring with uses of the operating equipment, the
method comprising: sensing that the working fluid in one of the
coupled subsystems has a temperature nearing a predetermined limit;
passing this temperature limited working fluid through the coupling
heat exchanger to transfer heat therefrom to the cooler working
fluid in the other coupled subsystem; and increasing the cooling
provided by the air and working fluid heat exchanger.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a divisional application of U.S. patent application
Ser. No. 11/595,185, entitled "INTERDEPENDENT LUBRICATION SYSTEMS,"
filed Nov. 9, 2006 by Frederick M. Schwartz et al.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to lubrication systems for
turbine engines and for associated integrated drive electrical
power generator systems and, more particularly, to various outside
fluid and lubricant heat exchangers for use in maintaining desired
temperatures of the lubricants in such engines and systems.
[0003] Lubrication systems for turbine engines and associated
equipment, such as a turbofan engine and an associated integrated
drive electrical power generator, provide pressurized lubricant, an
oil, to lubricate, cool and clean the engine main bearings, gearbox
gears, and the like. Similarly, pressurized oil is used for the
lubrication of bearings and other parts in an associated integrated
drive generator system. During such lubrications, heating of the
lubricant is caused to occur due to mechanical energy losses in the
lubricated apparatus. Thermal management of such lubricants is very
important for continued successful operation of such lubrication
systems in the apparatus lubricated thereby.
[0004] The amount of heat necessary to be ejected from lubricants
in such systems is increasing in evolving engines and associated
systems because of the use of larger electrical generators, for
instance, in aircraft turbine engines due to increasing consumption
of electrical power in the aircraft powered thereby, and because of
the advances in aircraft turbine engines such as the use of geared
turbofans for such aircraft with large fan-drive gearboxes. Despite
the added heat generated by the such modified and expanded
equipment, the necessary lubricating oil operating temperature
ranges to provide satisfactory lubricating performance have not
changed for the most part and, in some instances, the upper
operating temperature limits have been reduced.
[0005] The lubrication system for a turbofan engine in an aircraft
typically has a first heat exchanger providing lubricating oil
passing through passageways in that heat exchanger that is cooled
by the fuel stream flowing past these passageways. This arrangement
permits the lubricating oil to reject heat therein to the fuel
being burned by the engine thereby heating that fuel to help
recover some of the energy lost in the combustor of the engine.
[0006] Because, in some flight situations, more heat is generated
in the lubricating oil than is needed for warming the fuel, a
portion of the lubricating oil can be forced to bypass the heat
exchanger for the fuel and the lubricating oil, and the oil can be
directed to a further heat exchanger where the heat therein is
transferred to the air in the secondary airstream provided by the
fan of the turbofan engine. In a typical arrangement, a duct is
provided in the fan cowling through which a portion of the
airstream is diverted, or, more recently, provided in a fan duct
bifurcation structure, and the air and lubricating oil heat
exchanger is placed in this duct so that the lubricating oil
passing through passageways in that heat exchanger is cooled by the
duct airstream flowing past these passageways in the exchanger. If
such additional cooling of the oil is not needed in a flight
situation, the air can again be forced to bypass this air and
lubricating oil heat exchanger.
[0007] An integrated drive generator system that is powered by the
associated turbofan engine also has a lubrication system in which
the oil used as a lubricant therein is forced by a pump through a
heat exchanger where the heat therein is transferred to the air in
the secondary airstream provided by the fan of the turbofan engine.
Here, too, a duct is typically provided in the generator structure
through which a portion of the airstream is diverted with the
generator air and lubricating oil heat exchanger placed therein so
that the lubricating oil passing through passageways in that heat
exchanger is cooled by the duct airstream flowing past these
passageways in the exchanger.
[0008] Any of the fan airstream that is diverted to pass through
the lubricating oil and air heat exchangers in such duct systems
may be regulated by some air valve or stream limiting door in the
duct containing the exchanger, and the exchanger must be large
enough, insofar as assuring that a sufficient part of the cooling
engine fan airstream flows over a sufficient amount of lubricating
oil flowing in passageways therein, to provide adequate oil cooling
for the most extreme preflight or flight conditions encountered, or
both. This is true even though this heat exchanger size is not
needed for many, or even most, of these preflight or flight
conditions. Such a larger sized exchanger correspondingly requires
larger fairings about that exchanger leading to a) possible
detachment of the fan streams therefrom and the resulting vortex
losses absent further preventive measures, b) a larger inlet to the
duct possibly resulting in the "spilling" out of incoming air and
the accompanying eddy and mixing losses, and to c) a larger range
of required motion for the required larger size duct outlet flaps
possibly leading to this flap interfering more with the fan
airstream passing the outside of the flap when in the range of
being nearly fully open to being fully closed. These three
consequences, even in an optimally configured arrangement, will
result in pressure losses. Thus, such an air and lubricating oil
heat exchanger duct based system continually leads to thrust losses
in the turbofan engine despite being unnecessary for cooling the
lubricating oil in many flight situations. Hence, there is a strong
desire for a lubricating oil thermal management system to control
fuel and oil temperatures that also reduces such thrust losses and
additionally reduces the volume required therefor in the more
compact available spaces in advanced turbofan engines and
associated equipment arrangements.
BRIEF SUMMARY OF THE INVENTION
[0009] The present invention provides a heat exchange system for
use in operating equipment having a plurality of subsystems in each
of which a corresponding one of a plurality of working fluids is
utilized to provide selected operations in that subsystem with the
heat exchange system providing air and working fluid heat exchanges
to cool at least that working fluid utilized in its corresponding
subsystem at selectively variable rates in airstreams occurring
with uses of the operating equipment. The system has an airstream
heat exchanger that is connected in an air cooled one of the
plurality of subsystems to have the working fluid utilized therein
pass therethrough to cool that working fluid at selectively
variable rates in the airstreams passing thereby. A coupling heat
exchanger is connected in both the air cooled one of the plurality
of subsystems and another of the plurality of subsystems as a
coupled subsystem to have the corresponding working fluid utilized
in each of the air cooled and coupled subsystems pass therethrough
to permit one of these subsystems to cool the other. A control
system operates the coupling heat exchanger to determine the amount
of heat exchanged therein between the air cooled subsystem and the
coupled subsystem working fluids.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 shows a schematic diagram of an integrated drive
electrical generator lubrication system and a turbofan engine
lubrication system,
[0011] FIG. 2 shows a schematic diagram of an integrated drive
electrical generator lubrication system and an alternative turbofan
engine lubrication system,
[0012] FIGS. 3A and 3B show schematic diagrams of a thermally
coupled lubrication system and the coupling device therefor
embodying the present invention,
[0013] FIG. 4 shows a schematic diagram of an alternative thermally
coupled lubrication system embodying the present invention,
[0014] FIG. 5 shows a schematic diagram of an alternative thermally
coupled lubrication system embodying the present invention,
[0015] FIG. 6 shows a schematic diagram of an alternative thermally
coupled lubrication system embodying the present invention, and
[0016] FIG. 7 shows a schematic diagram of an alternative thermally
coupled lubrication system embodying the present invention.
DETAILED DESCRIPTION
[0017] Lubrication systems typically in use currently with turbofan
engines and associated integrated drive generator systems are
represented in the schematic diagram shown in FIG. 1 where there is
a lubrication system for the turbofan engine that is shown entirely
separate from the lubrication system for the generator. Thus, on
the left is shown a lubrication system, 10, for an integrated drive
generator system having therein an electrical generator, 11, with a
rotor that is forcibly rotated by the associated turbofan engine,
and an air and oil heat exchanger, 12, interconnected to generator
11 with oil conduits, 13, allowing therethrough the circulation of
the system lubricant, or the oil, through the moving parts of the
generator such as bearings and through the plurality of oil
carrying passageways of the exchanger about and between which
secondary airstreams from the engine fan can flow, the oil being
selectively forced to so circulate by a pump, 14, internal to
generator 11.
[0018] Air and oil heat exchanger 12 has a moveable flap, 15,
controlled by a computer controller, 16, through appropriately
operating a motor and associated position sensor device, 15', to
limit the fan airstream flow past this exchanger at its location as
positioned in a duct, 17. A temperature sensor, 18, senses the
temperature of the oil as it enters generator 11 and returns this
information to computer 16.
[0019] On the right side of FIG. 1 is shown a lubrication system,
20, for a turbofan engine having a lubricant or oil reservoir, 21,
for storing quantities of oil not then being circulated through the
remainder of the lubrication system out of which a pump, 22, forces
oil first through one of a plurality of oil conduits, 23, through a
filter, 24, and then through others of conduits 23 first to a
bypass valve, 25, and then to the lubricated parts in the remainder
of the lubrication system. An exception is any fraction of the oil
forced through the suitably dimensioned orifice in a trim conduit,
23', which conveys back to reservoir 21 any oil not accepted
through bypass valve 25 that results from overpressure in the oil
as generated by pump 22.
[0020] The oil exiting filter 24 not entering trim conduit 23' goes
under pressure to computer controlled bypass valve 25 by which a
computer controller, 26, can direct a selected fraction of this oil
flow to be forced through a fuel and oil heat exchanger, 27, to
further heat the fuel flowing in a fuel line, 27', in which
exchanger 27 is included and to further cool that fraction of the
oil provided thereto. The oil flow fraction in exchanger 27, if
any, is recombined in a combiner arrangement, 28, with any of the
oil exiting filter 24 that computer controller 26 caused to bypass
exchanger 27. Exchanger 27 is typically of a relatively small size
because of the more efficient heat transfers between liquids due to
their greater mass density as compared to the transfer between a
liquid and a gas in a air and oil heat exchanger, for example, as a
result of the substantially smaller mass density of that gas or
gases.
[0021] The combined oil from combiner 28 is forced under pressure
through oil carrying tubes (not explicitly shown in FIG. 1) of an
air cooled heat exchanger, 29. The degree of air cooling of the oil
flowing through exchanger 29 due to secondary airsteams from the
engine fan flowing past and between those tubes is controlled by
the position of a moveable flap, 30, as selected by computer
controller 26 through appropriately operating a motor and an
associated position sensor device, 30', to control air flow through
a duct, 31, in which exchanger 29 is positioned.
[0022] The oil emerging from exchanger 29 is then forced through
relatively low temperature sensitivity parts, 32, to be lubricated
typically including roller bearings, seals and gears. The oil that
gathers in the corresponding sump following this lubrication
thereby is then returned by a scavenger pump, 33, to reservoir 21.
A temperature sensor, 34, senses the temperature of the oil as it
proceeds to parts 32, and another temperature sensor, 35, senses
the temperature of the oil as it enters reservoir 21, and they both
returns their respective information to computer controller 26.
[0023] A variation in the typical lubrications systems arrangement
shown in FIG. 1 is shown in the schematic diagram of FIG. 2 in
which some of higher temperature sensitivity parts, 36, to be
lubricated must have the oil providing such lubrication being at a
significantly lower temperature than the oil lubricating the other
parts 32 having a tolerance for higher temperatures. Such
temperature sensitive parts 36 could be, for example, journal
bearings for the gears operating the fan in a geared turbofan
engine. In this situation, air and oil heat exchanger 29 is
positioned in conduits 23 ahead of low maintained temperature parts
36, as is temperature sensor 34, to assure that the oil temperature
can be controlled by computer controller 26 to the smaller
necessary value and that such control of temperature there will be
sufficient to leave the oil lubricating the other parts to be
lubricated 32 cool enough for those purposes. A further scavenger
pump, 37, is added to return the oil that gathers in the
corresponding sump following this lubrication thereby. The return
oil pumped by both of scavenger pumps 33 and 37 is combined in a
further combiner arrangement, 38, and returned to reservoir 21.
[0024] As indicated above, air and oil heat exchangers 12 and 29
must each be capable of providing adequate oil cooling for the most
extreme preflight or flight conditions encountered by their
respective lubrication systems. That is, they must be large enough
to assure that a sufficient part of the cooling engine fan
airstream flows over a sufficient amount of lubricating oil flowing
through passageways therein per unit time. Typically, however, the
extremes of the preflight or flight conditions encountered by air
and oil heat exchanger 12 in generator lubrication system 10 is not
the same as the extremes of the preflight or flight conditions
encountered by air and oil heat exchanger 29 in turbofan engine
lubrication system 20.
[0025] Typically, for the turbofan engine, the likely most extreme
heating increase of the lubricant to be encountered by its
lubrication system in relation to the cooling capability of the air
flow thereabout occurs in the conditions of the aircraft fuel
being, or having become, relatively hot while the aircraft was on
the ground followed immediately thereafter by operation at very
high altitude so that the heat in the lubricant can not be
significantly further transferred to the fuel in the aircraft fuel
and oil heat exchanger. In this circumstance, the aircraft takes
off with the engine developing high thrust to subsequently reach
the top of its climb after the takeoff, and during which climb the
engine is generating considerable heat in its lubricant.
[0026] At this top of the climb, if the engine thrust is
considerably reduced to end such climbing and, thereby,
significantly reduce the engine fan secondary airstream used by the
engine lubrication system air and oil heat exchanger to cool the
lubricant, an extreme in the heating of the engine oil occurs. This
is compounded by the cooling there depending on the much lower heat
transfer efficiency provided by air cooling due to the relatively
small mass density of air. The engine lubrication system at this
extreme condition will need to be sufficiently capable to limit the
temperature of its lubricant to not exceed some value, typically
225.degree. F. This system capability need to deal this very
infrequent operating conditions occurrence thus leaves the engine
lubrication system with extra cooling capacity during times the
aircraft is on the ground with the engine merely idling during all
preflight conditions and during all other flight conditions.
[0027] The generator lubrication system, on the other hand, is
likely to encounter its most extreme heating increase of its
lubricant in relation to the available air cooling capability on
the ground on a hot day. The generator in this circumstance will
typically supply its greatest load, and generate the most heat in
its lubricant in doing so, as the aircraft interior is cooled for
example by electrically operated air conditioning and has its
lights and instruments also operating to thereby provide some
maximum electrical load. In this situation, the engine will be just
idling so that there will not be much of an engine fan secondary
airstream to be used by the generator lubrication system air and
oil heat exchanger to cool the lubricant. Here, too, the
lubrication system at this extreme condition will need to limit the
temperature of its lubricant to not exceed some value typically
200.degree. F. However, the aircraft taking off greatly increases
the engine fan secondary airstream so that, even though the
generator heat output will increase somewhat compared to being on
the ground with the engine idling, the cooling capacity of the
generator air cooled oil and air heat exchanger is increased much
more thereby also leaving extra cooling capacity in this
lubrication system in this situation.
[0028] In most preflight and flight situations both generator
lubrication system 10 and engine lubrication system 20 of FIGS. 1
and 2 would be able to have the temperatures of the lubricants used
therein kept below their respective limits with relatively small
cooling capacities in air and lubricant heat exchangers 12 and 29,
respectively, thus allowing use of correspondingly relatively small
structural volumes therefor were those the only conditions
encountered. But, as indicated above, each of these lubrication
systems must instead be sized to be capable of keeping the
temperatures of the lubricants therein within those limits in these
extreme conditions described therefor above to avoid damage to the
generator and engine no matter how seldom such conditions are
encountered. Such larger heat exchangers thus necessarily require
larger ducts 17 and 31, respectively, which, if kept open to the
engine fan secondary airstream, will add significant drag and the
corresponding loss in efficiency. Thus, flaps 15 and 30 are used to
enable the closing off of those ducts when little cooling is needed
from air and lubricant heat exchangers 12 and 29. Nonetheless, drag
losses remain through the ducts compounded by the additional losses
caused by the larger ducts protruding into the fan airstream, and
there is substantial difficulty in finding sufficient volume in the
engine nacelle of engine fan bifurcation structure to accommodate
such larger exchangers and ducts.
[0029] However, the occurrence of the extremes of lubricant heating
in the two lubrication systems at different times in preflight and
flight situations, and the resultant availability of extra cooling
capacity in the opposite system at times of extreme heating of one
of these two lubrication systems, allows use of thermally coupled
generator lubrication system 10 and engine lubrication system 20 to
transfer heat from one to the other when either one or the other is
in or near its extreme lubricant heating condition. This other
system will not at that time be in or near its extreme lubricant
heating condition but will have available therein extra cooling
capacity. Hence, if these two lubrication systems are thermally
coupled to one another, either of air and lubricant heat exchangers
12 and 29, or both, may be "undersized". That is, each may be sized
smaller than necessary for the air and lubricant heat exchangers
that would otherwise needed in generator lubrication system 10 and
engine lubrication system 20 of FIGS. 1 and 2 if they are required
individually to be capable of always maintaining the lubricant in
its corresponding system below its temperature limit.
[0030] Thus, one of the thermally coupled lubrication systems,
served by a smaller exchanger than that which is necessary to be
individually capable of keeping the system lubricant always within
its temperature limits, can transfer heat occurring in its
lubricant at or near its extreme lubricant heating condition, in
excess of that which can be dissipated by this smaller exchanger,
to the other system to which it is thermally coupled to be
dissipated there by the exchanger in this second system. If this
second lubrication system can likewise transfer heat in its
lubricant at or near its extreme lubricant heating condition,
occurring at a different times than do the extremes in the first
system, to the first system through that thermal coupling, both of
heat exchangers 12 and 29 may be sized smaller than otherwise
necessary in generator lubrication system 10 and engine lubrication
system 20 of FIGS. 1 and 2.
[0031] FIG. 3A shows in a schematic diagram a thermally coupled
generator and engine lubrication system, 10', 20', that are under
operational control of a common computer controller, 26', with this
thermal coupling of generator lubrication system 10 and engine
lubrication system 20 of FIG. 2 to each other being provided by a
shell and tubes lubricant-to-lubricant, i.e. oil-to-oil, heat
exchanger, 40. The same numerical designations are used in FIG. 3A
as were used in FIG. 2 for the same system components present in
each. Selectively eliminating this thermal coupling of these
systems to one another that is provided by use of exchanger 40,
i.e. decoupling these otherwise separate generator and engine
lubrication systems to permit them to be independently operated, is
made an available choice by an associated computer controlled
bypass valve, 41. This bypass valve allows computer 26' to direct
the engine oil from air and oil heat exchanger 29 directly to
higher temperature sensitivity parts 36 thus bypassing heat
exchanger 40 to thereby prevent heat in the engine oil and heat in
the generator oil from being transferred from one to the other.
[0032] Heat exchanger 40 is shown in more detail in a
representative diagrammatic side view in cross section in FIG. 3B.
There, a pair of tube ports, 42, each open to a corresponding one
of a pair of outer cavities, 43, having tubes, 44, extending
therebetween. to carry a lubricating oil from one tube port to the
other through the outer cavities. A pair of shell ports, 45, open
to an interior cavity, 46, therebetween. to carry another
lubricating oil from one shell port to the other through the
interior cavitity while flowing about the outsides of tubes 44
guided by baffles, 47, to thereby permit heat exchange across the
walls of those tubes.
[0033] In coupled system 10', 20', oil-to-oil heat exchanger 40
receives the hottest oil from pump 14 of generator 12 in which this
oil has been heated which then passes through the tubes of that
exchanger and on to air and oil heat exchanger 11 in the generator
lubrication system portion. Thus, for the generator lubrication
system portion, oil therein that has been heated in generator 12 is
either further heated or cooled in exchanger 40 (depending on the
heat transfer direction arranged between the two lubrication
systems) before possibly being significantly cooled in air and oil
heat exchanger 11 depending on the position of flap 15.
[0034] Similarly, oil-to-oil heat exchanger 40 in coupled system
10', 20' receives oil from air and oil heat exchanger 29 in the
engine lubrication system portion through bypass valve 41, assuming
that valve has not been directed to divert oil around exchanger 40,
which then passes through the shell of exchanger 40 to be
transferred on to higher temperature sensitivity parts 36. Hence,
for the engine lubrication system portion, oil therein first cooled
in fuel cooled oil and fuel heat exchanger 27, if not diverted
therearound by bypass valve 25, is then possibly significantly
cooled further in air and oil heat exchanger 29, depending on the
position of flap 30, and thereafter is either further cooled or
heated in exchanger 40 (again depending on the heat transfer
direction arranged between the two lubrication systems), if not
bypassed by bypass valve 41, before being sent to lubricate higher
temperature sensitivity parts 36. This configuration choice in FIG.
3A for coupled system 10', 20' in thermally coupling generator
lubrication system 10 and engine lubrication system 20 of FIG. 2 to
one another is not unique, as will be shown below, and can depend
on many factors including the space available for heat exchangers
and their ducts, if any, with respect to their sizes and relative
positions in the engine nacelle or the duct bifurcation structure,
the presence or not of higher temperature sensitivity parts to be
lubricated and the concomitant temperature limit imposed thereby on
the corresponding lubricant as well as other temperature limits on
the lubricants in use, the efficiencies of the heat exchangers,
etc.
[0035] An alternative configuration for thermally coupling the
generator and engine lubrication systems is coupled system, 10'',
20'', shown in the schematic diagram of FIG. 4 in which oil-to-oil
heat exchanger 40 retains the same position in the generator
lubrication system but is now ahead of air and oil heat exchanger
29 in receiving oil in the engine lubrication system. Again, the
same numerical designations are used in FIG. 4 as were used in
FIGS. 2 and 3A for the same system components present in each.
[0036] Exchanger 40 in FIG. 4 receives oil there from oil and fuel
heat exchanger 27, if not diverted therearound by bypass valve 25,
through combiner arrangement 28 and bypass valve 41, again assuming
that valve has not been directed to divert oil around exchanger 40,
which then passes through the shell of exchanger 40 to be
transferred on to air and oil heat exchanger 29 to thereafter reach
higher temperature sensitivity parts 36. If heat is being
transferred from the generator lubrication system to the engine
lubrication system, this arrangement results in hotter oil going
into air and oil heat exchanger 29 which will increase the heat
rejected into the fan secondary airstream because of the greater
heat transfer efficiency coming about with the resulting greater
temperature difference between the oil and the cooling airstream.
Heat transfers in the opposite direction results in heat from
hotter oil in the engine lubrication system being transferred
directly to air and oil heat exchanger 12 in the generator
lubrication system.
[0037] Heat transfer efficiency can possibly be further improved by
allowing for a possible further increase in the oil temperature
before it enters air and oil heat exchanger 29 in another
configuration which again leaves oil-to-oil heat exchanger 40 in
the same position in the generator lubrication system but now ahead
of fuel and oil heat exchanger 27 in receiving oil in the engine
lubrication system as shown in a further coupled system, 10''',
20''', presented in schematic diagram form in FIG. 5. Here, too,
the same numerical designations are used in FIG. 5 as were used in
FIGS. 2, 3A and 4 for the same system components present in
each.
[0038] Thus, exchanger 40 in FIG. 5 receives oil there from
reservoir 21 through pump 22 and filter 24 and then bypass valve
41, once more assuming that valve has not been directed to divert
oil around exchanger 40, which then passes through the shell of
exchanger 40 to be transferred through oil and fuel heat exchanger
27, or diverted around that exchanger by bypass valve 25, and then
through combiner arrangement 28 and air and oil heat exchanger 29
to thereafter reach higher temperature sensitivity parts 36. In
those instances when the fuel has accepted all of the heat that
should be transferred to it, bypass valve 25 diverts the oil from
exchanger 40 to combiner arrangement 28 and then to air and oil
heat exchanger 29 without any cooling of that oil by oil and fuel
heat exchanger 27 so that heat transferred by the generator
lubrication system is added to the heat in the engine oil stored in
reservoir 21 that has been provided thereto by parts 32 and 36 and
sent to air and oil heat exchanger 29 (a fairly similar result can
be obtained in the configuration of FIG. 4 also by using bypass
valve 25 to divert oil around exchanger 27). Heat transfers in the
opposite direction results in heat from the nearly hottest oil in
the engine lubrication system being transferred directly to air and
oil heat exchanger 12 in the generator lubrication system.
[0039] Rather than working with the nearly hottest oil in the
generator lubrication system as in FIGS. 3A, 4 and 5, a further
coupled system, 10.sup.iv,20.sup.iv, is shown in the schematic
diagram of FIG. 6 working with the coolest oil in that system using
the same numerical designations there that were used in FIGS. 2,
3A, 4 and 5 for the same system components present in each. That
is, coupled system, 10.sup.iv,20.sup.iv in FIG. 6 is the same as
coupled system 10''', 20''' in FIG. 5 except for oil-to-oil heat
exchanger 40 in FIG. 6 receiving oil from air and oil heat
exchanger 12 in the generator lubrication system rather than from
generator 11 and pump 14. This reduces the heat transferred from
the generator lubrication system to the engine lubrication system
for heat transfers in that direction. However, for heat transfers
in the opposite direction, the heat from the engine lubrication
system is added to the heat generated in generator 11 in the oil of
the generator lubrication system in the generator so this
configuration is likely to be rarely used except in otherwise
difficult circumstances.
[0040] In the situation of a relatively small engine and a
correspondingly small engine lubrication system, but with an
associated integrated drive generator system having substantial
extra cooling capacity, an air and oil heat exchanger can be
dispensed with altogether in the engine lubrication system as shown
in yet another coupled system, 10.sup.v,20.sup.v, in the schematic
diagram of FIG. 7. Here, also, the same numerical designations are
used in FIG. 7 as were used in FIGS. 2, 3A, 4, 5 and 6 for the same
system components present in each. The coupled system of FIG. 7 is
the same as coupled system 10''', 20''' of FIG. 5 except for air
and oil heat exchanger 29 and associated flap 30 along with flap
motor 31' and duct 31 all having been removed. This removal will
significantly reduce the volume in the engine that must be devoted
to the engine lubrication system even though exchanger 12 will need
to at least be sized to be capable of always maintaining the
lubricant in its corresponding system below its temperature limit
even at its extreme operating condition. Thus, the engine
lubrication system heat required to be removed from the oil therein
to stay within its oil temperature limit must all be transferred
through oil-to-oil heat exchanger 40 to the generator lubrication
system to be dissipated through air and oil heat exchanger 12. The
alternative of having only air and oil heat exchanger 29 of FIG. 5
present in the coupled system so to allow dispensing with air and
oil heat exchanger 12 is an alternative configuration that is also
available.
[0041] Controlling the operation of any of the foregoing thermally
coupled systems in which a generator lubrication system and an
engine lubrication system are thermally coupled together, and
without any mixing of the lubricants used in either with that of
the other, is accomplished through using computer controller 26' to
that end which controller may be provided by the Electronic Engine
Control or by a separate lubrication systems controller. Computer
controller 26' operates based on temperature inputs obtained from
temperature sensors 18, 34 and 35, typically provided as
thermocouples, and further based on position inputs of airflow
flaps (or valves) 15 and 30 obtained from the position sensors in
motor and associated position sensor devices 15' and 30'.
[0042] Independent measurement of these variables in the generator
lubrication system and in the engine lubrication system is
necessary since generator heat rejection requirements and engine
heat rejection requirements are variables that are independent of
the other to some degree even though there is some common
dependence between them as a result of having the engine shaft also
rotate the generator rotor in the integrated drive electrical power
generator system at various rates during engine operation. Although
these measurements are taken independently in the two lubrication
systems, the controller acts to assure that both lubrication
systems operate about or below their temperature set point values
under normal operating conditions by controlling the airflows to
the air and oil heat exchanger present in one or both systems
through its positionings of the corresponding duct flaps and the
oil flows heat couplings between them in the oil-to-oil heat
exchanger thermally coupling each to the other through its
positionings of the bypass valve around that exchanger.
[0043] At or near the operating extreme of one of the thermally
coupled generator and engine lubrication systems, computer
controller 26' will detect, through its sampling of the output
values of the sensors in these systems, that the system
experiencing such an extreme is exceeding its set point oil
temperature value even though the controller has previously forced
the corresponding duct flap controlling the airflow over the air
and oil heat exchanger in that system to be maximally open to
thereby permit maximum airflow past that exchanger. Computer
controller 26' then will in turn react by closing bypass valve 41
around oil-to-oil heat exchanger 40 sufficiently further to draw
enough heat into the other system not at or near an extreme through
heat exchanger 40 from the system operating at or near an extreme.
In addition, computer controller 26' will in turn also react by
forcing the corresponding duct flap controlling the airflow over
the air and oil heat exchanger in the other lubrication system not
at or near an operating extreme to open sufficiently further to
cool the oil in this system drawing the heat from the system at or
near an extreme to oil temperature values sufficiently under its
set point oil temperature until the oil temperature value of the
lubrication system experiencing an operating extreme, or a near
extreme, drops sufficiently to be within a suitably selected
temperature range.
[0044] The situation of a small engine where the thermally coupled
generator and engine lubrication system are cooled by using only
one air and oil heat exchanger such as shown, for example, in FIG.
7, is somewhat different. Computer controller 26' will typically
use heat exchanger 40 to a) draw heat from the one of the generator
and engine lubrication systems not having an air and oil heat
exchanger when that system is operating at or near an extreme
operating condition, into b) the other system having such an air
and oil heat exchanger while controlling its duct flap to provide
adequate cooling (and perhaps will need to do so even if the system
without an air and oil heat exchanger is operating relatively far
from an extreme condition as it may have little opportunity to
dissipate heat generated therein even at or near normal operating
conditions).
[0045] Computer controller 26' may also be able to use heat
exchanger 40 to operate in the opposite direction to i) send heat
from the one of the generator and engine lubrication systems having
therein an air and oil heat exchanger when that system is operating
at or near an extreme operating condition, into ii) the other
system not having such an air and oil heat exchanger if this latter
system nevertheless has a significant capability to dissipate heat
generated therein. Any such heat transfers are likely to be
limited, however, to being relatively small because of the likely
relatively small heat dissipation capability present in the
lubrication system without an air and oil heat exchanger.
[0046] Thus, the air and oil heat exchanger in the system having
same is likely to be sized to at least be capable of providing all
of the oil cooling required by the system in which it is provided
at its extreme, if not even larger to also provide some oil cooling
for the other lubrication system at the time. Typically, the heat
transfers through exchanger 40 will be set to satisfy the oil
temperature set point value of at least one of these lubrication
systems with the oil of the other system to being cooled
substantially below its temperature set point value. In this
situation, one lubrication will almost always be optimally cooled
whereas the other will be overcooled.
[0047] Although the present invention has been described with
reference to preferred embodiments, workers skilled in the art will
recognize that changes may be made in form and detail without
departing from the spirit and scope of the invention.
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