Note: Descriptions are shown in the official language in which they were submitted.
CA 02245049 1998-09-24
A POWER GENERATION SYSTEM
RELATED APPLICATION
This application is a division of co-pending
Canadian Patent Application Serial No. 2,169,779 filed on
February 19, 1996, which is a division of Canadian Patent
Application Serial No. 2,009,120 filed February 1, 1990.
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to a combined
power generator system comprising a generator driven by
both a steam turbine and a gas turbine.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present
invention there is provided a steam turbine having a
rotor provided with a mono-block rotor shaft, multi-stage
blades fixed on the mono-block rotor shaft from a high
pressure side at which a steam inlet temperature of first
stage blades is not less than 530°C to a low pressure
side at which are provided final stage blades having a
length not less than 40 inches for a shaft rotated at
3000 rpm or a length not less than 33.5 inches for a
shaft rotated at 3600 rpm, said final stage blades
comprising a Ti-based alloy.
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CA 02245049 1998-09-24
In accordance with another aspect of the
present invention there is provided a steam turbine
having a rotor provided with a mono-block rotor shaft,
multi-stage blades fixed on the mono-block rotor shaft
from a high pressure side at which a steam inlet
temperature of first stage blades is not less than 566°C
to a low pressure side at which are provided final stage
blades having a length not less than 30 inches and
comprising a Ti-based alloy.
In accordance with yet another aspect of the
present invention there is provided a steam turbine
having a rotor provided with a mono-block rotor shaft,
multi-stage blades fixed on the mono-block rotor shaft
from a high pressure side at which a steam inlet
temperature of first stage blades is not less than
566°C to a low pressure side at which are provided final
stage blades having a length not less than 30 inches
and comprising a martensitic steel containing 10 to
13 wt.o Cr.
In accordance with still yet another aspect of
the present invention there is provided a steam turbine
having a rotor provided with a mono-block rotor shaft,
multi-stage blades fixed on the mono-block rotor shaft
from a high pressure side at which a steam inlet
temperature of first stage blades is not less than 530°C
to a low pressure side at which are provided final stage
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CA 02245049 1999-08-03
blades having a length not less than 40 inches for a
shaft rotated at 3000 rpm or a length not less than 33.5
inches for a shaft rotated at 3600 rpm.
BRIEF DESCRIPTION OF THE INVENTION
Figures 1, 8 and 9 are partial cross sectional
views of a steam turbine using a rotor shaft integrating
high and low pressure portions;
Figure 2 is a graph showing a relationship
between a ratio (V + Mo)/(Ni + Cr), and creep rupture
strength and impact value;
- lb -
CA 02245049 1998-09-24
Figure 3 is a graph showing a relationship
between creep rupture strength and oxygen;
Figure 4 is a graph showing a relationship
between creep rupture strength and Ni; and
Figure 5 to Figure 7 are graphs showing
relationships between a V-shaped notch impact value, and
Ni, Mn, Si + Mn, a ratio Mn/Ni, and a ratio (Si + Mn)/Ni.
PREFERRED EMBODIMENTS OF THE INVENTION
EXAMPLE 1
A turbine rotor is described below with reference
to examples. Table 1 shows chemical compositions of
typical specimens subjected to toughness and creep rupture
tests. The specimens were obtained in such a manner that
they were melted in a high frequency melting furnace, made
to an ingot, and hot forged to a size of 30 mm square at a
temperature from 850 to 1150°c. The specimens Nos. l, 3
and 7 to 11 are materials according to the present
invention. The specimens Nos. 2, 4 to 6 were prepared for
the comparison with the invented materials. The specimen
No. 5 is a material corresponding to ASTM A470 Class 8 and
the specimen No. 6 is a material corresponding to ASTM A470
Class 7. These specimens were quenched in such a manner
that they were made to have austenitic structure by being
heated to 950°C in accordance with a simulation of the
conditions of the center of a rotor shaft integrating high
and low pressure portions of a steam turbine, and then
cooled at a speed of 100°C/h. Next, they were annealed by
- 2 -
CA 02245049 1998-09-24
being heated at 665°C for 40 hours and cooled in a furnace.
Cr-Mo-V steels according to the present invention included
no ferrite phase and were made to have a bainite structure
as a whole.
An austenitizing temperature of the invented
steels must be 900 to 1000°C. When the temperature is
- 3 -
CA 02245049 1998-09-24
less than 900°C, creep rapture strength is lowered,
although superior toughness can be obtained. When the
temperature exceeds 1000°C, toughness is lowered,
although superior creep rapture strength can be
obtained. An annealing temperature must be 630 to
700°C. If the temperature is less than 630°C, superior
toughness cannot be obtained, and when it exceeds 700°C,
superior creep strength cannot be obtained.
Table 2 shows the results of a tensile
strength test, impact test, and creep rupture test.
Toughness is shown by Charpy impact absorbing energy of
a V-shaped notch tested at 20°C. Creep rupture strength
is determined by Larason Mirror method and shown by a
strength obtained when a specimen was heated at 538°C
for 100,000 hours. As apparent from Table 2, the
invented materials have a tensile strength not less than
88 kgf/mm2 at a room temperature, a 0.2~ yield strength
not less than 70 kgf/mm2, an FATT not more than 40°C, an
impact absorbing energy not less than 2.5 kgf-m both
before they were heated and after they had been heated,
and a creep rapture strength not less than about 11
kg/mmz, and thus they are very useful for a turbine
rotor integrating high and low pressure portions. In
particular, a material having a strength not less than
15 kg/mm2 is preferable to plant long blades of 33.5
inches.
- 4 _
CA 02245049 1998-09-24
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_ 6 _
CA 02245049 1998-09-24
Fig. 2 shows a relationship between a ratio
of a sum of V and Mo acting as carbide creating elements
to a sum of Ni and Cr acting as quenching ability
improving elements, and creep rupture strength and
impact absorbing energy. The creep rupture strength is
increased as the component ratio (V + Mo)/(Ni + Cr) is
increased until it becomes about 0.7. It is found that
the impact absorbing energy is lowered as the component
ratio is increased. It is found that the toughness
(vE20 z 2.5 kgf/m) and the creep rupture strength (6R z
11 kgf/mm2) necessary as the characteristics of a
material forming the turbine rotor integrating high and
low pressure portions are obtained when (V + Mo)/(Ni +
Cr) - 0.45 to 0.7. Further, to examine the brittle
characteristics of the invented material No. 2 and the
comparative material Nos. 5 (corresponding to a material
currently used to a high pressure rotor) and 6
(corresponding to a material currently used to a low
pressure rotor), an impact test was effected to
specimens before subjected to a brittle treatment for
3000 h at 500°C and those after subjected to the treat-
ment and a 50$ fracture appearance transition tempera-
ture (FATT) was examined. An FATT of the comparative
material No. 5 was increased (made brittle) from 119°C
to 135°C (D FATT = 16°C), an FATT of the material No. 6
was increased from -20°C to 18°C (~FATT = 38°C) by the
brittle treatment, whereas it was also confirmed that an
FATT of the invented material No. 3 remained at 38°C
_ 7 _
CA 02245049 1998-09-24
before and after the brittle treatment and thus it was
confirmed that this material was not made brittle.
The specimens Nos. 8 to 11 of the invented
materials added with rare earth elements (La - Ce), Ca,
Zr, and Al, respectively, have toughness improved by
these rare earth elements. Tn particular, the addition
of the rare earth elements is effective to improve the
toughness. A material added with Y in addition to La -
Ce was also examined and it was confirmed that Y was
very effective to improve the toughness.
Table 3 shows the chemical compositions and
creep rapture strength of the specimens prepared to
examine an influence of oxygen to creep rapture strength
of the invented materials. A method of melting and
forging these specimens were the same as that of the
above-mentioned specimens Nos. 1 to 11.
_ 8 -
CA 02245049 1998-09-24
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9 _
CA 02245049 1998-09-24
_ The specimens were quenched in such a manner
that they were austenitized by being heated to 950°C and
then by being cooled at a speed of 100°C/h. Next, they
were annealed by being heated at 660°C for 40 hours.
Table 4 shows 538°C creep rapture strength in the same
manner as that shown in Table 2. Figure 3 is a graph
showing a relationship between creep rupture strength
and oxygen. It is found that a superior creep rupture
strength not less than about 12 kgf/mm2 can be obtained
by making 02 to a level not more than 100 ppm, further,
a superior creep rupture strength not less than 15
kgf/mm2 can be obtained by making 02 level thereof be
not more than 80 ppm, and furthermore, a superior creep
rupture strength not less than 18 kgf/mm2 can be
obtained by making 02 level thereof be not more than
40 ppm.
Table 4
Specimen Mn Si+Mn V+Mo Creep rupture
No. strength
Ni Ni Ni+Cr ( kgf/mm2 )
15 0.047 0.076 0.55 19.9
16 0.063 0.088 0.57 21.0
17 0.056 0.087 0.56 20.3
18 0.073 0.103 0.57 18.5
19 0.065 0.089 0.51 15.6
0.052 0.087 0.52 14.3
-10 -
CA 02245049 1998-09-24
Figure 4 is a graph showing a relationship
between 538°C, 105 hour creep rupture strength and an
amount of Ni. As shown in Figure 4, the creep rupture
strength is abruptly lowered as an amount of Ni is
increased. In particular, a creep rupture strength not
less than about 11 kgf/mm2 is exhibited when an amount
of Ni is not more than about 2~, and in particular, a
creep rupture strength not less than about 12 kgf/mm2 is
exhibited when an amount of Ni is not more than 1.9~.
Figure 5 is a graph showing a relationship
between an impact value and an amount of Ni after the
specimens have been heated at 500°C for 3,000 hours. As
shown in Figure 5, the specimens of the present
invention in which a ratio (Si + Mn)/Ni is not more than
0.18 or in which another ratio Mn/Ni is not more than
0.1 can bring about high impact value by the increase in
an amount of Ni, but the comparative specimens Nos. 12
to 14 in which a ratio (Si + Mn)/Ni exceeds 0.18 or in
which another ratio Mn/Ni exceeds 0.12 have a low impact
value not more than 2.4 kgf-m, and thus an increase in
the amount of Ni is little concerned with the impact
value.
Likewise, Figure 6 is a graph showing a
relationship between impact value after being subjected
to heating embrittlement and an amount of Mn or an
amount of Si + Mn of the specimens containing 1.6 to
1.9$ of Ni. As shown in Figure 6, it is apparent that
Mn or (Si + Mn) greatly influences the impact value at a
- 11 -
CA 02245049 1998-09-24
particular amount of Ni. That is, the specimens have a
very high impact value when an amount of Mn is not more
than 0.2~ or an amount of Si + Mn is not more than
0.25$.
Likewise, Figure 7 is a graph showing a
relationship between an impact value and a ratio Mn/Ni
or a ratio (Si + Mn)/Ni of the specimens containing 1.52
to 2.0~ Ni. As shown in Figure 7, a high impact value
not less than 2.5kgf-m is exhibited when a ratio Mn/Ni
is not more than 0.12 or a ratio Si + Mn/Ni is not more
than 0.18.
EXAMPLE 2
Table 5 shows typical chemical compositions
(wt~) of specimens used in an experiment.
The specimens were obtained in such a manner
that they were melted in a high frequency melting
furnace, made to an ingot, and hot forged to a size of
30 mm square at a temperature from 850 to 1250°C. The
specimens Nos. 21 and 22 were prepared for the
comparison with the invented materials. The specimens
Nos. 23 to 32 are rotor materials superior in toughness
according to the present invention.
The specimens Nos. 23 to 32 were quenched in
such a manner that they were austenitized being heated
to 950°C in accordance with a simulation of the
conditions of the center of a rotor shaft integrating
high and low pressure portions of a steam turbine, and
- 12 -
CA 02245049 1998-09-24
then cooled at a speed of 100°C/h. Next, they were
annealed by being heated at 650°C for 50 hours and
cooled in a furnace. Cr-Mo-V steel according to the
present invention included no ferrite phase and was made
to have a bainite structure as a whole.
An austenitizing temperature of the invented
steels must be 900 to 1000°C. When the temperature was
less than 900°C, creep rupture strength was lowered,
although superior toughness can be obtained. When the
temperature exceeded 1000°C, toughness was lowered,
although superior creep rapture strength was obtained.
An annealing temperature must be 630 to 700°C. If the
temperature is less than 630°C superior toughness cannot
be obtained, and when it exceeds 700°C, superior creep
strength cannot be obtained.
Table 6 shows the results of a tensile
strength test, impact test, and creep rupture test.
Toughness is shown by Charpy impact absorbing energy of
a V-shaped notch tested at 20°C and 50~ fracture
transition temperature (FATT).
The creep rupture test by a notch was effected
using specimens each having a notch bottom radius of 66
mm, a notch outside diameter of 9 mm, and a V-shaped
notch configuration of 45° (a radius of a notch bottom
end) "r" is 0.16 mm).
-13 -
CA 02245049 1998-09-24
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_15 _
CA 02245049 1998-09-24
Creep rupture strength is determined by a
Larson Mirror method and shown by strength obtained when
a specimen was heated at 538°C for 105 hours. As
apparent from Table 6, the invented materials have a
tensile strength not less than 88 kgf/mm2 at a room
temperature, an impact absorbing energy not less than 5
kgf/mm2, a 50~ FATT not more than 40°C, and a creep
rupture strength of 17 kgf/mm2, and thus they are very
useful for a turbine rotor integrating high and low
pressure portions.
These invented steels have greatly improved
toughness as compared with that of the material
(specimen No. 21) corresponding to a material currently
used to a high pressure rotor (having a high impact
absorbing energy and a low FATT). Further, they have a
538°C, 105 hour.notch creep rupture strength superior to
that of the material (specimen No. 22) corresponding to
a material currently used to a low pressure rotor.
In the relationship between a ratio of a sum
of V and Mo as carbide creating elements to a sum of Ni
and Cr as quenching ability improving elements, and
creep rapture strength and impact absorbing energy, the
creep rupture strength is increased as the component
ratio (V + Mo)/(Ni + Cr) is increased until it becomes
about 0.7. The impact absorbing energy is lowered as
the component ratio is increased. The toughness (vE20 >
2.5 kgf-m) and the creep rupture strength (R > 11
kgf/mm2) necessary as the turbine rotor integrating high
- 16 -
CA 02245049 1998-09-24
and low pressure portions are obtained when (V + Mo)/(Ni
+ Cr) is made to be in the range of 0.45 to 0.7.
Further, to examine brittle characteristics of the
invented materials and the comparative material No. 21
(corresponding to a material currently used to a high
pressure rotor) and the comparative material No. 22
(corresponding to a material currently used to a low
pressure rotor), an impact test was effected to
specimens before subjected to a brittle treatment at
500°C for 3000 h and those after subjected to the
treatment and a 50~ fracture transition temperature
(FATT) was examined. As a result, an FATT of the
comparative material No. 21 was increased (made brittle)
from 119°C to 135°C (oFATT = 16°C), an FATT of the
material, No. 2 was increased from -20°C to 18°C (oFATT
38°C) by the brittle treatment, whereas it was also
confirmed that an FATT of the invented materials were
39°C both before and after subjected to the brittle
treatment and thus it was confirmed that they were not
made brittle.
The specimens Nos. 27 to 32 of the invented
materials added with rare earth elements (La - Ce), Ca,
Zr, and A1, respectively, have toughness improved
thereby. In particular, an addition of the rare earth
elements is effective to improve the toughness. A
material added with Y in addition to La - Ce was also
examined and it was cohfirmed that Y was very effective
to improve the toughness.
- 17 _
CA 02245049 1998-09-24
As a result of an examination of an influence
of oxygen to creep rupture strength of the invented
materials, it is found that a superior strength not less
than about 12 kgf/mm2 can be obtained by making 02 to be
in a level not more than 100 ppm, further, a superior
strength not less than 15 kgf/mmz can be obtained at a
level thereof not more than 800 ppm, and, furthermore, a
superior strength not less than 18 kgf/mm2 can be
obtained at a level thereof not more than 400 ppm.
As a result of an examination of the
relationship between 538°C, 105 hour creep rupture
strength and an amount of Ni, it is found that the creep
rapture strength is abruptly lowered as an amount of Ni
is increased. In particular, a strength not less than
about 11 kgf/mm2 is exhibited when an amount of Ni is
not more than about 2~, and in particular, a strength
not less than about 12 kgf/mm2 is exhibited when an
amount of Ni is not more than 1.9~.
Further, as a result of an examination of a
relationship between impact value and an amount of Ni
after the specimens have been heated at 500°C for 3000
hours, the specimens according to the present invention
in which the ratio (Si + Mn)/Ni is not more than 0.18
bring about high impact values by the increase in an
amount of Ni, but the comparative specimens in which the
ratio (Si + Mn)/Ni exceeds 0.18 have a low impact value
not more than 2.4 kgf/mm2, and thus an increase in the
amount of Ni is little concerned with the impacts value.
-18 -
CA 02245049 1998-09-24
As a result of an examination of a relation-
ship between impact value and an amount of Mn or an
amount of Si + Mn of the specimens containing 1.6 to
1.9g of Ni, it is found that Mn or Si + Mn greatly
influences the impact value at a particular amount of
Ni, and the specimens have a very high impact value when
an amount of Mn is not more than 0.2~ or an amount of Si
+ Mn is in a range from 0.07 to 0.25.
As a result of an examination of a relation-
ship between impact value and a ratio Mn/Ni or a ratio
(Si + Mn)/Ni of the specimens containing 1.52 to 2.0~ of
Ni, a high impact value not less than 2.5 kgf/mm2 is
exhibited when the ratio Mn/Ni is not more than 0.12
or the ratio (Si + Mn)/Ni is in a range from 0.04 to
0.18.
EXAMPLE 3
Figure 1 shows a partial cross sectional view
of a steam turbine integrating high and low pressure
portions. A conventional steam turbine consumes high
pressure and temperature steam of 80 atg and 480°C at the
main steam inlet thereof and low temperature and pressure
steam of 722 mmHg and 33°C at the exhaust portion thereof
by a single rotor thereof, whereas the steam turbine
integrating high and low pressure portions of the
invention can increase an output of a single turbine by
increasing a pressure and temperature of steam at the
_ 19
CA 02245049 1998-09-24
main steam inlet thereof to 100 atg and 536°C,
respectively. To increase an output of the single
turbine, it is necessary to increase a blade length of
movable blades at a final stage and to increase a flow
rate of steam. For example, when a blade length of the
movable blade at a final stage is increased from 26
inches to 33.5 inches, an ring-shaped band area is
increased by about 1.7 times. Consequently, a
conventional output of 100 MW is increased to 170 MW,
and further when a blade length is increase to 40
inches, an output per a single turbine can be increased
by 2 times or more.
When a Cr-Mo-V steel containing 0.5~ of Ni is
used for a rotor integrating high and low pressure
portions as a material of the rotor shaft having blades
of a length not less than 33.5 inches, this rotor
material can sufficiently withstand an increase in a
steam pressure and temperature at the main stream inlet
thereof, because this steel is superior in high
temperature strength and creep characteristics to be
thereby used at a high temperature region. In the case
of a long blade of 26 inches, however, tangential stress
in a low temperature region, in particular, tangential
stress occurring at the center hole of the turbine rotor
at a final stage movable blade portion is about 0.95 in
a stress ratio (operating stress/allowable stress) when
the rotor is rotated at a rated speed, and in the case
of a long blade of 33.5 inches, the tangential stress is
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CA 02245049 1998-09-24
about 1.1 in the stress ratio, so that the above steel
is intolerable to this application.
On the other hand, when 3.5~ Ni-Cr-Mo-V steel
is used as a rotor material, the above stress ratio
thereof is about 0.96 even when long blades of 33.5
inches are used, because this material has toughness in
the low temperature region, and tensile strength and
yield strength which are 14~ higher than those of the
Cr-Mo-V steel. However, long blades of 40 inches are
used, the above stress ratio is 1.07, and thus this
rotor material is intolerable to this application.
Since this material has creep rupture stress in the high
temperature region which is about 0.3 times that of the
CR-Mo-V steel and thus it is intolerable to this
application due to lack of high temperature strength.
To increase an output as described above, it
is necessary to provide a rotor mateial which
simultaneously has both superior characteristics of the
Cr-Mo-V steel in a high temperature region and superior
characteristics of the Ni-Cr-Mo-V steel in a low
temperature region.
When a long blade of a class from 30 to 40
inches is used, a material ahving a tensile strength not
less than 88 kgf/mm2 is necessary, because conventional
Ni-Cr-Mo-V steel (ASTM A470 Class 7) has the stress
ratio of 1.07, as described above.
Further, a material of a steam turbine rotor
integrating high and low pressure portions on, which
_ 21 _
CA 02245049 1998-09-24
long blades not less than 30 inches are attached must
have a 538°C, 105 h creep rapture strength not less than
15 kgf/mm2 from a view point of securing safety against
high temperature breakdown on a high pressure side, and
an impact absorbing energy not less than 2.5 kgf-m (3
kg-m/cm2) from a view point of securing safety against
breakdown due to brittleness on a low pressure side.
From the above view point, in the invention
there was obtained heat resisting steels which can
satisfy the above requirements and which increase an
output per a single turbine.
The steam turbine includes thirteen stages of
blades 4 planted on a rotor shaft 3 integrating high and
low pressure portions, and steam having a high tempera-
I5 ture and pressure of 538°C and 88 atg, respectively, is
supplied from a steam inlet 1 through a steam control valve
5. The steam flows in one direction from the inlet 1 with
the temperature and pressure thereof being decreased to
33°C and 722 mmHg, respectively and then discharged from an
outlet 2 through final stage blades 4. Since the rotor
shaft integrating high and low pressure
portions 3 according to the present invention is exposed
to a steam temperature ranging from 538°C to 33°C,
forged steel composed of Ni-Cr-Mo-V low alloy steel
having the characteristics described inthe example 1 is
used. The portions of the rotor shaft 3 where the
blades 4 are planted are formed to a disk shape by
- 22 -
CA 02245049 1998-09-24
integrally machining the rotor shaft 3. The shorer the
blade is, the longer the disk portion, whereby the
vibration thereof is reduced.
The rotor shaft 3 was manufactured in such a
manner that cast ingot having the alloy compositions of the
specimen No. 16 shown in the example 1 and the specimen No.
24 shown in the example 2, respectively was electro-slug
remelted, forged to a shaft having a diameter of 1.2 m,
heated at 950°C for 10 hours, and then the shaft was cooled
at a cooling speed of 100°C/h by spraying water while it is
rotated. Next, the shaft was annealed by being heated at
665°C for 40 hours. A test piece cut from the center of
the rotor shaft was subjected to a creep test, an impact
test of a V-shaped notch (a cross sectional area of the
specimen: 0.8 cmz) before the specimen was heated and after
it had been heated (after it had been heated at 500°C for
300 hours), and a tensile strength test, and values
substantially similar to those of the examples 1 and 2 were
obtained.
Each portion of the present examples are
fabricated from a material having the following
composition.
(1) Blade
Blades composed of three stages on a high
temperature and pressure side have a length of about 40
mm in an axial direction and are fabricated from forged
martensitic steel consisting, by weight, of 0.20 to
_23 _
CA 02245049 1998-09-24
0.30 C, 10 - 13~ Cr, 0.5 to 1.5$ Mo, 0.5 to 1.5~ W, 0.1
to 0.3~ V, not more than 0.5~ Si, not more than 1~ Mn,
and the balance Fe and incidental impurities.
Blades at an intermediate portion, of which
length is gradually made longer as they approach a low
pressure side, are fabricated from forged martensitic
steel consisting, by weight, of 0.05 to 0.15 C, not
more than 1$ Mn, not more than 0.5~ Si, 10 to 13~ Cr,
not more than 0.5$ Mo, not more than 0.5~ Ni, and the
balance Fe and incidental impurities.
Blades having a length of 33.5 inches at a
final stage, ninety pieces of which were planted around
one circumference of a rotor were fabricated from forged
martensitic steel consisting, by weight, of 0.08 to
0.15 C, not more than 1~ Mn, not more than 0.5~ Si, 10
to 13$ Cr, 1.5 to 3.5~ Ni, 1 to 2$ Mo, 0.2 to 0.5~ V,
0.02 to 0.08 N, and the balance Fe and incidental
impurities. An erosion-preventing shield plate
fabricated from a stellite plate was welded to the
leading edge of the final stage at the terminal end
thereof. Further, a partial quenching treatment was
effected regarding portions other than the shield plate.
Furthermore, a blade having a length not less than 40
inches may be fabricated from Ti alloy containing 5 to
~$ A1 and 3 to 5$ V.
Each of 4 to 5 pieces of these blades in the
respective stages was fixed to a shroud plate through
tenons provided at the extreme end thereof and caulked
- 24 _
CA 02245049 1998-09-24
- to the shroud plate made of the same material as the
blades.
The 12~ Cr steel shown above was used to
provide a blade which was rotated at 3000 rpm even in a
case of its length of 40 inches. Although Ti alloy was
used 'when a blade having a length of 40 inches was
rotated at 3600 rpm, the 12~ Cr steel was used to
provide a blade having a length up to 33. 5 inches and
being rotated at 3600 rpm.
(2) Stationary blades 7 provided in the first to third
stages at the high pressure side were fabricated from
martensitic steel having the same composition as those
of the corresponding movable blades and stationary
blades other than those of the first to third stages
were fabricated from martensitic steel having the same
composition as those of the movable blades at the
intermediate portion.
(3) A casing 6 was fabricated from Cr-Mo-V cast steel
comprising by weight 0.15 to 0.3~ C, not more than 0.5~
Si, not more than 1$ Mn, 1 to 2~ Cr, 0.5 to 1.5~ Mo,
0.05 to 0.2~ V, and not more than O.lg Ti.
Designated at 8 is a generator capable of
generating an output of 100,000 to 200,000 KW. In the
present examples, a distance between bearings 12 of the
rotor shaft was about 520 cm, an outside diameter of a
final blade was 316 cm, and a ratio of the distance
between bearings to the outside diameter was 1.65. The
_ 25 -
CA 02245049 1998-09-24
generator had a generating capacity of 100,000 KW. A
distance between the bearings was 0.52 m per 10,000 KW.
Further, in the present examples, when a blade
of 40 inches was used at a final stage, an outside
diameter thereof was 365 cm, and thus a ratio of a
distance between bearings to this outside diameter was
1.43, whereby an output of 200,000 KW was generated with
a distance between the bearings being 0.26 m per 10,000
KW.
In these cases, a ratio of an outside diameter
of a portion of the rotor shaft where the blades were
planted to a length of the final stage blade is 1.70 for
a blade of 33.5 inches and 1.71 for a blade of 40
inches.
In the present examples, steam having a tem-
perature of 566°C was applicable, and pressures thereof
of 121, 169. or 224 atg were also applicable.
EXAMPLE 4
Figure 8 is a partially taken-away sectional
view of an arrangement of a reheating type steam turbine
integrating high and low pressure portions. In this
steam turbine, steam of 538°C and 126 atg was supplied
from an inlet 1 and discharged from an outlet 9 through
a high pressure portion of a rotor 3 as steam of 367°C
and 38 atg, and further steam having been heated to
538°C and to a pressure of 35 atg was supplied from an
inlet 10, flowed to a low pressure portion of the rotor
- 26 -
CA 02245049 1998-09-24
3 through an intermediate pressure portion thereof,
and discharged from an outlet 2 as steam having a
temperature of about 46°C and a pressure of 0.1 atg. A
part of the steam discharged from the outlet 9 is used
as a heat source for the other purpose and then again
supplied to the turbine from the inlet 10 as a heat
source therefor. If the rotor for the steam turbine
integrating high and low pressure portions is fabricated
from the material of the specimen No. 5 of the example
1, the vicinity of the steam inlet l, i.e., a portion a
will have sufficient high temperature strength, however,
since the center of the rotor 3 will have a high
ductility-brittle transition temperature of 80 to 120°C,
there will be caused such drawback that, when the
vicinity of the steam outlet 2, i.e., a portion b has a
temperature of 50°C, the turbine is not sufficiently
ensured with respect to safety against brittle fracture.
On the other hand, if the rotor 3 is fabricated from the
material of the specimen No. 6, safety against brittle
fracture thereof at the vicinity of the steam outlet 2,
i.e., the portion b will be sufficiently ensured, since
a ductility-brittle transition temperature at the center
of the rotor 3 is lower than a room temperature,
however, since the vicinity of the steam inlet 1, i.e.,
the portion a will have insufficient high temperature
strength and since the alloy constituting the rotor 3
contains a large amount of Ni, there will be such a
drawback that the rotor 3 is apt to become brittle when
- 27
CA 02245049 1998-09-24
it is used (operated) at a high temperature for a long
time. More specifically, even if any one of the
materials of the specimens Nos. 5 and 6 is used, the
steam turbine rotor integrating high and low pressure
portions made~of the material composed of the specimens
No. 5 or 6 has a certain disadvantage, and thus it
cannot be practically used. Note that, in Figure 8, 4
designates a movable blade, 7 designates a stationary
blade, and 6 designates a casing, respectively. A high
pressure portion was composed of five stages and a low
pressure portion was composed of six stages.
In this example, the rotor shaft 3, the
movable blades 4, the stationary blades 7, and the
casing 6 were formed of the same materials as those of
the above-mentioned example 3. The movable blade at a
final stage had a length not less than 33.5 inches and
was able to generate an output of 120,000 KW. Similar
to the example 3, 12~ Cr steel or Ti alloy steel is used
for this blade having length of not less than 33.5
inches. A distance between bearings 12 was about 454
cm, a final stage blade of 33.5 inches in length had a
diameter of 316 cm and a ratio of the distance between
the bearings to this outside diameter was 1.72. When a
final stage blade of 40 inches in length was used, an
output of 200,000 KW was generated. The blade portion
thereof had a diameter of 365 cm and a ratio of a
distance between bearings to this diameter was 1.49. A
distance between the bearings per a generated output of
28
CA 02245049 1998-09-24
10,000 KW in the former of 33.5 inches was 0.45 m and
that in the latter of 40 inches was 0.27 m. The above
mentioned steam temperature and pressures were also
applicable to this example.
EXAMPLE 5
The rotor shaft integrating high and low pressure
portions was also able to be applied to a single flow type
steam turbine in which a part of steam of an intermediate
pressure portion of a rotor shaft was used as a heat source
for a heater and the like. The materials used in the
example 3 were used regarding the rotor shaft, movable
blades, stationary blades and casing of this example.
EXAMPLE 6
The steam turbines described in the examples 3
to 5 were directly connected to a generator, and a gas
turbine was directly connected to the generator. A steam
turbine of this example was applied to a combined
generator system, wherein steam was generated by a
waste-heat recovery boiler using exhaust combustion gas
occurring in the gas turbine and the steam turbine was
rotated by the steam. The gas turbine generated an
output of about 40,000 KW and the steam turbine
generated an output of about 60,000 KW, and thus this
combined generator system generated a total output of
- 29 -
CA 02245049 1998-09-24
100,000 KW. Since the steam turbine of this example was
made compact, it was manufactured at a cost lower than
that of a conventional large stem turbine supposing that
they have the same generating capacity and it has an
advantage of being economically operated when an output
to be generated fluctuates.
In the gas turbine, air compressed by a
compressor was fed in a burner to produce a combustion
gas having a high temperature not less than 1100°C and a
disc on which blades were planted was rotated by the
combustion gas. The disc was formed of three stages,
wherein a movable blade was fabricated from Ni base cast
alloy containing by weight 0.04 to 0.1$ C, 12 to 16~ Cr,
3 to 5~ A1, 3 to 5~ Ti, 2 to 5~ Mo, and 2 to 5~ Ni and a
stationary blade was fabricated from Co base cast alloy
containing by weight 0.25 to 0.45 C, 20 to 30~ Cr, 2 to
5~ at least one selected from the group consisting of Mo
and W, and 0.1 to 0.5g at least one selected from the
group consisting of Ti and Nb. A burner liner was
fabricated from FE-Ni-Cr austenitic alloy containing by
weight 0.05 to 0.15 C, 20 to 30% Cr, 30 to 45~ Ni, 0.1
to 0.5~ at least one selected from the group consisting
of Ti and Nb, and 2 to 7$ at least one selected from the
group consisting of Mo and W. A heat shielding coating
layer made of a Y202 stabilizing zirconia sprayed onto
the outer surface of the liner was provided to the flame
side of the liner. Between the Fe-Ni-Cr austenitic
alloy and the zirconia layer was disposed a MCrAlY alloy
- 30 -
CA 02245049 1998-09-24
layer consisting, by weight, of 2 to 5$ A1, 20 to 30g
Cr, 0.1 to 1~ Y, and at least one selected from the
group~consisting of Fe, Ni and Co, that is, M is at
least one selected from the group consisting of Fe, Ni
and Co.
An A1-diffused coating layer was provided on
the movable and stationary blades shown above.
A material of the turbine disc was fabricated
from a martensitic forged steel containing by weight
0.15 to 0.25 C, not more than 0.5~ Si, not more than
0.5~ Mn, 1 to 2~ Ni, 10 to 13~ Cr, 0.02 to 0.1~ at least
one selected from the group consisting of Nb and Ta,
0.03 to 0.1~ N, and 1.0 to 2.O~S Mo; a turbine spacer,
distant piece and compressor disc at a final stage being
fabricated from the same martensitic steel,
respectively.
EXAMPLE 7
Figure 9 is a partially sectional view of a steam
turbine integrating high and low pressure portions. A
rotor shaft integrating high and low pressure portions 3
used in this example was fabricated from the Ni-Cr-Mo-V
steel having the bainite structure as a whole described in
the example 3. The left side is a high pressure side and
the right side is a low pressure side in Figure 9, and a
final stage blade had a length of 33.5 or 40 inches.
Blades on the left high pressure side were made of the
_ 31 _
CA 02245049 1998-09-24
same material as that described in the example 3 and
final stage blades were made of the same material as
that described in the Example 3. Steam of this example
had a temperature of 538°C and a pressure of 102 kg/cm2
at an inlet and had an temperature no more than 46°C and
a pressure not more than an atmospheric pressure at an
outlet, which steam was supplied to a condenser as shown
by numeral 2. A material of the rotor shaft of this
example had an FATT not more than 40°C, a V-shaped notch
impact value at a room temperature not less than 4.8
kgf-mm2 (a cross sectional area: not less than 0.8 cm2),
a tensile strength at a room temperature not less than
81 kgf/mm2, a 0.2 yield strength not less than 63
kgf/mm2, an elongation not less than 16~, a contraction
of area not less than 45 percent, and a 538°C, 105 hour
creep rupture strength not less than 11 kgf/mm2. Steam
was supplied from an inlet 14, discharged from an outlet
15 through high pressure side blades, again supplied to
a reheater 13, and supplied to a low pressure side as
high temperature steam of 538°C and 35 atg. Designated
at 12 are bearings disposed at the opposite sides of the
rotor shaft 3, and a distance between bearings was about
6 m. The rotor of this example rotated at 3600 rpm and
generated an output of 120,000 KW. Blades 4 were
composed of six stages on the high pressure side and ten
stages on the low pressure side. In this example, a
distance between bearings was 0.5 m per a generated
output of 10,000 KW, and thus the distance was about 40~
- 32
CA 02245049 1998-09-24
shorter than a conventional distance of 1.1 m.
Further, in this example, a final stage blade
of 33.5 inches had a diameter of 316 cm and thus a ratio
of a distance between the bearings to this outside
diameter was 2.22. In another case, a final stage blade
of 40 inches having a diameter of 365 cm was used, a
ratio of the distance between the bearings to the
diameter being 1.92, which enables an output of 200,000
KW to be generated. As a result, a distance between the
bearings per a generated output of 10,000 KW was 0.3 m
in this another case, whereby the steam turbine was able
to be made very compact.
_ 33 _
