DESCRIPTION
FIELD OF THE INVENTION
The present disclosure relates generally to gas turbines such as in particular,
but not exclusively, to aeroderivative gas turbines. More specifically, the disclosure
relates to industrial applications of aeroderivative gas turbines, for power generation,
natural gas liquefaction or similar industrial applications.
DESCRIPTION OF THE RELATED ART
Aeroderivative gas turbines are widely used as power sources for mechanical
drive applications, as well as in power generation for industrial plants, pipelines,
offshore platforms, LNG applications and the like.
Fig. 1 illustrates a schematic representation of a system including a gas turbine
and a load mechanically driven by said gas turbine. More specifically, in the
diagrammatic representation of Fig. 1 reference 1 indicates a gas turbine which drives
a load, for example a compressor or a compressor train for a natural gas liquefaction
line, schematically shown at 3. The gas turbine 1 is connected to the load 3 by means
of a load coupling 5. The load coupling 5 comprises a shaft 7 and a joint 9. In the
£ example of Fig.l the shaft 7 rotatingly driven by the gas turbine 1 is connected to a
gear box 11. An output shaft 13 of said gear box 11 connects the gear box 11 to the
load 3. The load 3 can include a single rotary machine, e.g. a compressor, or an
electric generator, or else a set of rotary machines on the same shaft. A further gear
box can be arranged between two adjacent rotary machines driven by the turbine 1.
The gas turbine 1 comprises a gas generator 15 and a power turbine 17. The
gas generator 15 comprises in turn a compressor 19, a combustion chamber 21 and a
high pressure turbine 23. The air entering the compressor 19 is compressed at high
pressure and added with a liquid or gaseous fuel in the combustion chamber 21. The
compressed and high temperature combustion gases are expanded first in the high
2
pressured turbine 23, which is connected through an internal shaft 25 to the
compressor 19. The expansion of the combustion gasses in the high pressure turbine
23 generates mechanical power, which drives into rotation the compressor 19. The
partly expanded combustion gasses exiting the high pressure turbine 23 enter the
power turbine 17 and further expand to generate mechanical power, which drives the
load 3 through the load coupling 5. The exhausted combustion gasses are collected by
a collector-diffuser and discharged through a discharge line 27.
In the example shown in Fig. 1 the gas turbine is a single shaft gas turbine, i.e.
a gas turbine wherein a single internal shaft 25 connects the high pressure turbine 23
to the compressor 19 of the gas generator 15. The power turbine, sometimes also
Wf named low pressure turbine, is supported by a shaft that is separate from the internal
shaft 25 such that the gas generator 15 can rotate independently of and at a different
speed than the power turbine 17. Other gas turbine embodiments provide for a
different number of internal shafts and the gas generator can comprise a different
number of compressors and turbines driving the compressors.
These turbines are typically aeroderivative turbines.
In the exemplary embodiment of Fig. 1 the load 3 is connected through the
load coupling 5 to the so-called hot end of the gas turbine 1, i.e. the gas turbine side
where the power turbine 17 is arranged, to be distinguished from the cold end,
corresponding to the side of compressor 19.
^ ^ The load-coupling 5 is subject to temperature deformations due to high
temperature at the hot end of the gas turbine 1. Thermal deformation of the shaft 7
must be sagged, i.e. measures must be adopted to prevent the thermal expansion of the
shaft 7 to damage the load bearings of either the power turbine 17 or the machinery
arranged on the load side, i.e. the bearings of the gear box 11 (if present) and/or of the
rotary machines 3 driven by the gas turbine 1. Commonly adopted measures include
arranging a joint which can compensate for the thermal expansion of the shaft.
Thermal expansion of the shaft nevertheless generates axial forces on the bearings on
both sides of the joint, i.e. on the turbine bearings and on the gearbox or rotary
machine bearings.
3
SUMMARY OF THE INVENTION
As will be described here below, reference being made to some embodiments
of the invention, by delivering a stream of cooling air in a volume at least partly
surrounding at least a portion of the load coupling connecting the gas turbine and the
load, heat is actively removed by forced air convection from the load coupling, thus
reducing the thermal deformation of the load connection and therefore reducing the
axial load on the turbine and load bearings.
According to some embodiments of the subject matter disclosed therein, a gas
turbine is provided, said gas turbine comprising at least: a compressor; a power
Jfe turbine; a load coupling connecting the gas turbine to a load; a load-coupling guard at
least partly surrounding the load coupling; a cooling air channeling designed and
arranged to circulate cooling air flow in said load-coupling guard sufficient to remove
heat from said load coupling. The forced air convection provided in the load-coupling
guard removes heat from the load coupling and maintains the load coupling at low
temperature, thus reducing the overall thermal deformation of the load coupling. In
this way axial loads generated by thermal expansion of the load bearing are reduced
also when the gas turbine is connected to the load via said load coupling on the hot
end of the gas turbine, i.e. on the side of the power turbine rather than on the side of
the compressor.
Further embodiments and advantageous features of a gas turbine according to
the subject matter disclosed herein are described here below.
In some preferred embodiments, the gas turbine is an aeroderivative gas
turbine. The gas turbine can be a single-shaft gas turbine, i.e. a gas turbine wherein
the compressor is mechanically driven by a high pressure gas turbine, wherein the
compressor and the high pressure gas turbine are supported on a common shaft. The
compressor and high pressure gas turbine form a gas generator. The exhaust
combustion gases exiting the high pressure turbine are further expanded in the power
turbine. The power turbine is supported on an independent shaft and drives into
rotation a load. In some embodiments a gear box is arranged between the power
turbine and the load.
4
In other embodiments the gas turbine can be a dual-shaft or a three-shaft gas
turbine, comprising two or three compressors and two or three turbines, with co-axial
shafts connecting the turbines and shafts to one another.
Irrespective of the number of compressors and turbines, and from the number
of co-axial shafts, a load coupling is provided between the power turbine, i.e. the
turbine providing power to drive the load, and the load, with possible interposition of
a gear box to drive the load and the power turbine at different rotational speeds. The
load coupling commonly comprises at least a shaft and one or more joints. The shaft
can be comprised of one or more shaft sections or shaft portions, connected to one
another.
•
In some embodiments the load coupling and the load-coupling guard extend
through an exhaust gas plenum or exhaust collector-diffuser assembly, which at least
partly surrounds said load coupling and said load-coupling guard. The exhaust
collector-diffuser assembly develops around the axis of the gas turbine and collects
the exhausted and expanded combustion gases to discharge them in the environment
or convey the expanded, high temperature combustion gases e.g. towards a steam
turbine or another section of a co-generation plant.
In some embodiments, the gas turbine is at least partly arranged in a gas
turbine package comprised of a turbomachinery compartment housing said gas
turbine. In some embodiments, an air circulation system is further provided, for
circulating cooling air in the turbomachinery compartment. A load compartment is
^ P preferably arranged downstream the turbomachinery compartment. The load
compartment is arranged on a side of the turbomachinery compartment. An opposite
air intake plenum is arranged on the opposite side of the turbomachinery
compartment, to allow air in the compressor of the gas turbine and in the
turbomachinery compartment, to cool the exterior of the turbomachinery casing. The
load coupling which connects the gas turbine and the load preferably extends through
the load compartment. The load-coupling guard may receive air from the cooling air
circulation system or other dedicated sources.
The cooling air channeling can comprise an air port, wherein cooling air from
said cooling air circulation system is forcedly circulated. At least a first ventilation
5
duct fluidly connects said air port to said load-coupling guard and in some
embodiments a second and possibly a third ventilation duct is provided, in fluid
communication with the load compartment to allow forced air circulation in said load
compartment.
The load-coupling guard can be open ended at both ends, such that the air
forcedly circulating in the volume delimited by the load-coupling guard can escape at
both ends of the load-coupling guard. This enhances cooling of the load coupling also
in portions thereof extending outside the load-coupling guard.
According to a further aspect, the subject matter disclosed herein relates to a
^k method of reducing heat and mechanical stresses on a load coupling in a gas turbine,
said gas turbine comprising: at least a compressor; a power turbine; and a load
coupling connecting said gas turbine to a load. According to some embodiments, the
method comprises removing heat from the load coupling by forcing cooling air around
said load coupling.
In some embodiments, the method comprises the steps of: defining a confined
volume at least partly surrounding the load coupling; and forcedly circulating cooling
air in said confined volume to remove heat from the load coupling. It shall be
understood that heat is usually removed from one portion of the load coupling only,
i.e. the portion nearest to the hot end of the gas turbine, since thermal expansion is
concentrated in said section of the load coupling.
^ ^ In an exemplary embodiment of the subject matter disclosed herein the method
comprises the steps of: arranging a load-coupling guard at least partly surrounding the
load coupling, the confined volume being at least partly delimited by the loadcoupling
guard; and forcedly circulating cooling air between said load coupling and
said load-coupling guard, whereby removing heat from said load coupling.
In further embodiments, the method can additionally comprise the step of
causing cooling air to escape from the confined volume at at least a first end of said
load-coupling guard facing said power turbine, whereby a stream of cooling air
exiting said confined volume at said first end of said load-coupling guard is directed
against said power turbine. In some embodiments the method can further comprise the
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step of causing cooling air to escape from said confined volume at at least a second
end of said load-coupling guard facing said load, whereby a stream of cooling air
exiting said confined volume at said second end of said load-coupling guard is
directed away from said power turbine and towards said load. The second end of the
load-coupling guard can open toward the environment, i.e. outside die turbine
package.
According to some exemplary embodiments, the method comprises the steps
of: arranging the gas turbine in a gas turbine package; generating a cooling air stream
to cool a casing of said gas turbine; deviating a fraction of said cooling air stream
towards the confined volume partly surrounding the load coupling.
The gas turbine package usually also comprises a load compartment between
the gas turbine and the load. The load coupling and the confined volume surrounding
said load coupling can be arranged at least partly in said load compartment and
cooling air can be circulated partly also in said confined volume and partly in said
load compartment.
Features and embodiments are disclosed here below and are further set forth in
the appended claims, which form an integral part of the present description. The above
brief description sets forth features of the various embodiments of the present
invention in order that the detailed description that follows may be better understood
and in order that the present contributions to the art may be better appreciated. There
are, of course, other features of the invention that will be described hereinafter and
l P which will be set forth in the appended claims. In this respect, before explaining
several embodiments of the invention in details, it is understood that the various
embodiments of the invention are not limited in their application to the details of the
construction and to the arrangements of the components set forth in the following
description or illustrated in the drawings. The invention is capable of other
embodiments and of being practiced and carried out in various ways. Also, it is to be
understood that the phraseology and terminology employed herein are for the purpose
of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception, upon which
the disclosure is based, may readily be utilized as a basis for designing other
7
structures, methods, and/or systems for carrying out the several purposes of the
present invention. It is important, therefore, that the claims be regarded as including
such equivalent constructions insofar as they do not depart from the spirit and scope of
the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete appreciation of the disclosed embodiments of the invention
and many of the attendant advantages thereof will be readily obtained as the same
becomes better understood by reference to the following detailed description when
considered in connection with the accompanying drawings, wherein:
^ * Fig. 1 illustrates a gas turbine and compressor arrangement according to the
state of the art;
Fig.2 illustrates a gas turbine and compressor arrangement embodying the
subject matter disclosed herein;
Fig.3 illustrates a schematic section according to a vertical plane of the
arrangement of Fig.2;
Fig.4 illustrates a cross-section according to line III-III in Fig.3.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
The following detailed description of the exemplary embodiments refers to the
^ h accompanying drawings. The same reference numbers in different drawings identify
the same or similar elements. Additionally, the drawings are not necessarily drawn to
scale. Also, the following detailed description does not limit the invention. Instead,
the scope of the invention is defined by the appended claims.
Reference throughout the specification to "one embodiment" or "an
embodiment" or "some embodiments" means that the particular feature, structure or
characteristic described in connection with an embodiment is included in at least one
embodiment of the subject matter disclosed. Thus, the appearance of the phrase "in
one embodiment" or "in an embodiment" or "in some embodiments" in various places
throughout the specification is not necessarily referring to the same embodiment(s).
8
Further, the particular features, structures or characteristics may be combined in any
suitable manner in one or more embodiments.
Fig. 2 schematically illustrates a system embodying the subject matter
disclosed herein. The system comprises a gas turbine and a load connected to the gas
turbine by means of a load coupling. More specifically in the diagrammatic
representation of Fig. 2, a gas turbine package 31 comprising a gas turbine 33 is
connected by means of a load coupling 35 to a load 37. In the exemplary embodiment
illustrated in Fig. 2 the load 37 is represented as a compressor, such as a compressor
for a refrigerant of a natural gas liquefaction system. In the exemplary embodiment
illustrated in Fig.2 a gearbox 38 is arranged between the gas turbine and the
^ r compressor 37. The compressor 37 can be one of a series of compressors forming a
compressor train driven by the same gas turbine 33. It shall be understood that a
different kind of load can be driven by the gas turbine. For example the load can be an
electric generator of a power generation plant. The load coupling can include one or
more gearboxes and/or one or more rotary machines, such as electric machines or
turbomachines.
In the exemplary embodiment shown in Fig. 2, the gas turbine package 31
comprises an air intake plenum 39 in fluid communication with an air intake line 41
and with the inlet side of a compressor 43 of the gas turbine 33. The gas turbine 33
can be comprised of a high pressure turbine 45 and a power turbine 47. The high
pressure turbine 45 is drivingly connected to the compressor 43 by an internal shaft
^ ^ (not shown). Combustion gases generated in the combustion chamber of the gas
turbine expand sequentially in the high pressure turbine 45 to generate the power
required to drive the compressor 43 and subsequently in the power turbine 47, to drive
the load 37. Different gas turbine arrangements can be used, for example including
two or more compressor in sequence and more than two turbines in series on the hot
side of the gas turbine 33. In general terms, the gas turbine 33 comprises a gas
generator comprised of at least one compressor 43 and a high pressure turbine 45, said
gas generator providing combustion gases at high temperature and high pressure,
which are expanded in one or more turbines 47.
In some embodiments the gas turbine 33 can be an aeroderivative gas turbine.
9
The overall structure and layout, including the number of compressors, the number of
turbines, the number of shafts, the number of compression and expansion stages of the
aeroderivative gas turbine can vary from one aeroderivative gas turbine to the other.
Suitable aeroderivative gas turbines are LM2500+G4 LSPT or LM2500
aeroderivative gas turbines, both commercially available from GE Aviation, Evendale,
Ohio, USA. Other suitable aeroderivative gas turbines are the PGT25+G4
aeroderivative gas turbine commercially available from GE Oil and Gas, Florence,
Italy, or the Dresser-Rand Vectra® 40G4 aeroderivative gas turbine commercially
available from Dresser-Rand Company, Houston, Texas, USA, for example. In other
embodiments, the aeroderivative gas turbine can be a PGT16, a PGT 20, all
A commercially available from GE Oil and Gas, Florence, Italy or an LM6000
aeroderivative gas turbine, commercially available from GE Aviation, Evendale,
Ohio, USA.
The expanded and exhausted combustion gases are collected in an exhaust
diffuser-collector assembly 49 and discharged towards the environment through a
discharge line 51.
In the exemplary embodiment shown in the drawings, the exhaust diffusercollector
assembly 49 is arranged in a load compartment 53. The load compartment 53
is arranged at the opposite side of the gas turbine package 31 with respect to the intake
plenum 39, i.e. at the hot end side of the gas turbine. The load coupling 35 extends
from the power turbine 47 through the exhaust diffuser-collector assembly 49 which
^ ^ therefore at least partly surrounds the load coupling 35.
Part of the air sucked through the air intake plenum 39 at the cold end side of
the gas turbine 33 flows through the gas turbine package 31 and more specifically
through a turbomachinery compartment 55 forming the intermediate portion of the gas
turbine package 31 and housing at least partly the gas turbine 33. The air circulating in
the turbomachinery compartment 55 cools the casing of the turbine machinery and is
exhausted through an exhaust cooling air line 57.
In some embodiments, part of the cooling air sucked in the turbomachinery
compartment 55 is deviated in an air duct 59 which is in fluid communication with an
air port 61.
10
In the exemplary embodiment shown in the drawing, an air ventilation duct 63
fluidly connects the air port 61 with a load-coupling guard 65, the structure of which
can best be seen in Fig. 3. In some embodiments the load-coupling guard 65 is
comprised of a cylindrical shell or sleeve 67 surrounding at least partly a shaft 69
forming part of the load-coupling 35.
In some embodiments the load-coupling guard 65 comprises a first end 65A
facing towards the gas turbine 33 and a second end 65B facing the load 37. At least
one end and preferably both ends 65A and 65B can be open such that cooling air
which is forcedly circulated through the air port 61 and the ventilation duct 63 escapes
from a confined volume or space delimited by the cylindrical shell or sleeve 67 of the
QP load-coupling guard 65, said volume being indicated with reference number 70. In
some embodiments the first end 65 A of the load-coupling guard is oriented such that
air escaping the first end 65A is forced against the exhaust diffuser-collector assembly
49. In some embodiments the second end 65B of the load-coupling guard 65 can be
open towards the environment, outside the turbine package, such that a part of the
cooling air forcedly circulating in the confined volume surrounding the load coupling
is vented in the environment.
In some embodiments the air port 61 is additionally in fluid communication
with a second ventilation duct 64 and possibly with a third ventilation duct 66 (see
Fig. 4).
The second and third ventilation ducts 64 and 66 comprise open ends arranged
^ B in the load compartment 53, such that air forced into the ventilation ducts 64, 66 is
vented in the load compartment 53. The air circulating in the load compartment cools
the load compartment 53 and any apparatus arranged therein.
•
With the above described arrangement, cooling air forced by the cooling air
circulating system through the air duct 59 is caused to enter the first ventilation duct
63 as well as the second and/or third ventilation ducts 64 and 66, if present. The air
stream conveyed by the first ventilation duct 63 into the volume 70 surrounding the
load coupling 35 cools the load coupling 35 and more specifically the shaft 69
surrounded by the load-coupling guard 65. An air flow escaping from both ends 65A
and 65B of the load-coupling guard 65 is forced to remove heat also from both
ll
portions of the shaft 69 extending from the load-coupling guard 65 and of one or more
joints arranged on said shaft 69 outside of the load-coupling guard 65. Additionally,
the air escaping from the open end 65A of the load-coupling guard 65 is oriented
towards the exhaust diffuser-collector assembly 49, maintaining the temperature in the
area surrounding the load-coupling 35 at a reduced temperature.
The temperature of the cooling air and the rate of the cooling air flow are
advantageously such as to maintain the temperature of the load coupling 35 and more
specifically of the shaft 69 at such a value to reduce substantially the axial load on the
bearings of the shaft both on the turbine sides as well as on the load side.
^ ^ As can be appreciated in particular from Fig. 3 in some embodiments the open
end 65A of the load-coupling guard 65 is arranged within the hollow part of the
exhaust diffuser-collector assembly 49 through which the load coupling 35 extends. In
this manner an efficient cooling air stream exiting the tubular load-coupling guard 65
is directed along the proximal end of the shaft 69, and possibly a joint 69A arranged
between the shaft 69 and the hot end of the gas turbine 33 just in that area where the
highest heat load is present, said heat load being caused by the hot exhausted gasses
collected by the exhaust diffuser-collector assembly 49 and deviated towards the
discharge line 51.
Fig. 4 schematically illustrates a further joint 69B arranged on the load
coupling 35 in the area of the second open end 65B of the load-coupling guard 65.
Also in this area, the forced cooling air stream escaping the open end 65B provides for
^ P an efficient cooling of this area of the load coupling 35.
While the disclosed embodiments of the subject matter described herein have
been shown in the drawings and fully described above with particularity and detail in
connection with several exemplary embodiments, it will be apparent to those of
ordinary skill in the art that many modifications, changes, and omissions are possible
without materially departing from the novel teachings, the principles and concepts set
forth herein, and advantages of the subject matter recited in the appended claims.
Hence, the proper scope of the disclosed innovations should be determined only by
the broadest interpretation of the appended claims so as to encompass all such
modifications, changes, and omissions. In addition, the order or sequence of any
12
process or method steps may be varied or re-sequenced according to alternative
embodiments.

WE CLAIM:
1. A gas turbine (33) comprising: a compressor (43); a power turbine
(47); a load coupling (35) connecting said gas turbine (33) to a load (37); a loadcoupling
guard (65) at least partly surrounding said load coupling (35); a cooling air
channeling (51, 61, 63) designed and arranged to circulate a cooling air flow in said
load-coupling guard sufficient to remove heat from said load coupling (35).
^ » 2. Gas turbine according to claim 1, wherein said gas turbine is an
aeroderivative gas turbine.
3. Gas turbine according to claim 1 or 2, wherein said load coupling (35)
is connected to a hot end of said gas turbine.
4. Gas turbine according to claim 3, wherein said load coupling (35) and
said load-coupling guard (65) extend through an exhaust collector-diffuser assembly
(49), which at least partly surrounds said load coupling and said load-coupling guard
(65).
5. Gas turbine according to one or more of the preceding claims,
comprising: a gas tmbine package (31) comprised of a turbomachinery compartment
^ ^ (55) housing said gas turbine (33); a cooling air circulation system for circulating
cooling air in said turbomachinery compartment (55); and a load compartment (53),
said load coupling (35) extending through said load compartment (53).
6. Gas turbine according to claim 5, wherein said turbine package (31)
comprises an air intake plenum (39), said turbomachinery compartment (55) being
arranged between said air intake plenum (39) and said load compartment (53).
7. Gas turbine according to claim 5 or 6, wherein said cooling air
charmeling comprises an air port (61), wherein cooling air from said cooling air
circulation system is forcedly circulated; and wherein at least a first ventilation duct
(63) fluidly coimects said air port (61) to said load-coupling guard (65) and a second
14
ventilation duct (64; 66) feeds cooling air in said load compartment (53).
8. Gas turbine according to claim 7, comprising a third ventilation duct
(66; 64) feeding cooling air in said load compartment (53).
9. Gas turbine according to claim 8, wherein said second ventilation duct
(64) and said third ventilation duct (66) are arranged substantially symmetrically at
opposite sides of said first ventilation duct (63).
10. Gas turbine according to one or more of the preceding claims, wherein
said load-coupling guard (65) has a first end (65A) facing the power turbine (47) and
a second end (65B) facing said load (37) connected to said load coupling (35), and
^ P wherein at least said first end (65A) is open, whereby cooling air escaping from said
load-coupling guard (65) is directed towards said power turbine (47).
11. Gas turbine according to claim 10, wherein said second end (65B) is
open, whereby cooling air escaping from said load-coupling guard (65) is directed
towards said load (37).
12. Gas turbine according to claims 4 and 10 or 4 and 11, wherein said first
end (65A) of said load-coupling guard (65) is arranged in a hollow space at least
partly surrounded by said exhaust collector-diffiiser assembly (49), whereby cooling
air exiting said load-coupling guard (65) cools the exhaust collector-diffuser assembly
(49).
^ ^ 13. Gas turbine according to claim 10 or 11 or 12, wherein said load
coupling (35) comprises at least a mechanical joint (69A; 69B) and a shaft (69).
14. A system comprising a gas turbine (33) according to one or more of the
preceding claims, and a load (37) driven by said gas turbine, wherein said load (37) is
connected to said gas turbine by said load-coupling (35).
15. A method of reducing heat and mechanical stresses on a load coupling
(35) in a gas turbine (33), said gas turbine comprising at least a compressor (43), a
power turbine (47) and a load coupling (35) connecting said gas turbine (33) to a load
(37); said method comprising removing heat from said load coupling (35) by forcing
cooling air around said load coupling (35).
15
16. Method according to claim 15, comprising the steps of: defining a
confined voliune (67) at least partly surrounding said load coupling (35); forcedly
circulating said cooling air in said confined volume to remove heat from said load
coupling (35).
17. Method according to claim 16, comprising the step of: arranging a
load-coupling guard (65) at least partly surroimding said load coupling (35), said
confined volume (67) being at least partly delimited by said load-coupling guard (65);
and forcedly circulating cooling air between said load coupling (35) and said loadcoupling
guard (65), whereby removing heat fi-om said load coupling.
^ ^ 18. Method according to claim 17, fiirther comprising the step of causing
cooling air to exit said confined volume (67) at at least a first end (65A) of said loadcoupling
guard (65) facing said power turbine (47), whereby a stream of cooling air
exiting said confined volume at said first end (65 A) of said load-coupling guard (65)
is directed against said power turbine (47).
19. Method according to claim 17 or 18, further comprising the step of
causing cooling air to exit said confined volume (67) at at least a second end (65B) of
said load-coupling guard (65) facing said load (37), whereby a stream of cooling air
exiting said confined volume at said second end of said load-coupling guard (65) is
directed away from said power turbine (47) and towards said load (37).
20. Method according to one or more of claims 16 to 19, comprising the
^ ^ steps of: arranging said gas turbine (33) in a gas turbine package (31); generating a
cooling air stream to cool a casing of said gas turbine (33); deviating a firaction of said
cooling air stream towards said confined volume (65).
21. Method according to one or more of claims 16 to 20, comprising the
steps of: providing a load compartment (53) between said gas turbine (33) and said
load (37); arranging said load coupling (35) and said confined volume (67)
surrounding said load coupling (35) at least partly in said load compartment (53);
feeding said cooling air partly in said confined volume and partly in said load
compartment (53)