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Патент USA US3033010

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May 8, 1962
Filed Nov. 4, 1958
U ite States atent
Patented May 8, 1962
speed gearwheel 34 geared to the pinion 30 and two
medium-speed gearwheels 35 and 36 both geared to the
Allan William Davis, Bearsden, Glasgow, Scotland, as
signor to The Fairiield Shipbuilding and Engineering
other pinion 31; three secondary pinions 37, 38 and 39
which are connected to the gearwheels 34, 35 and 36,
respectively; the large slow-speed gearwheel 40 on the
propeller shaft 41 with which gearwheel all three second
Company Limited, Glasgow, Scotland
Filed Nov. 4, 1958, Ser. No. 771,916
Claims priority, application Great Britain Nov. 8, 1957
2 Claims. (Cl. 60—102)
ary pinions 37, 38 and 39 mesh. The axes of the primary
pinion 31 and the gearwheels 35, 36 geared to it are in
the same plane or nearly in the same plane; that is to
10 say, these two gearwheels mesh with the primary pinion
This invention relates to marine propulsion steam
turbine installations of the type in which associated tur
bines working at different steam pressure stages transmit
at more or less diametrally opposite sides of it.
In such a two-turbine installation, it is an economic
necessity that the high-pressure turbine shall rotate at a
propulsive power through double-reduction gearing in
much higher speed than the low-pressure turbine; for
cluding a large slow~speed propeller-driving gearwheel 15 instance, the speed ratio may be 5 to 3. Seeing that
to which the turbine shafts are geared.
the teeth of the secondary pinions 37, 38 and 39 must all
In such installations, especially where there is reheating
have the same linear speed, the gearing must be designed
of the steam passing from one ahead stage to another,
to take into account the different primary-pinion rota
it is customary to have three associated ahead steam
tional speeds. Thus, in the example, the low-pressure
turbines—viz. high-pressure, intermediate-pressure and 20 turbine double-reduction gear pairs 31, 35 and 38, 40
low-pressure turbines-in orderto take full advantage
or 31, 36 and 39, 40 have lower gear ratios than the
of the available temperature range of the steam.
corresponding high-pressure-turbine gear pairs 30, 34 and
The object of this invention is to devise for an installa
tion of the type described an arrangement of double
reduction gearing by virtue of which it will be practicable 25
and economical to have only two ahead steam turbines,
namely a high-pressure turbine and a low-pressure turbine,
37, 40.
The lower speed of the low-pressure-turbine primary
pinion 31, in comparison with the other primary pinion
30, requires that the low-pressure turbine shall have pro
portionately more than twice the high-pressure-turbine
and by so doing reduce substantially the overall capital
power in order to give an approximation to equality in
and operating costs of such an installation.
Therefore, the invention is a marine propulsion steam
turbine installation of the type described comprising a
torque between each of the low-pressure-turbine second
ary pinions 38 and 39 on the one hand and the corre
sponding high-pressure-turbine ‘secondary pinion 37 on
high-pressure steam turbine, a low-pressure steam turbine
the other hand. For instance, the power ratio between
designed to develop considerably more power than the
the turbines may be about 2 to 5 in the case instanced
high-pressure turbine, a steam reheater through which
where the speed ratio is 5 to 3.
passes the steam exhausted by the high pressure turbine 35
This considerable difference in power between the
to the low pressure turbine, two high-speed primary
turbines of a two-turbine installation is practicable only
pinions driven by the two turbines, respectively, three
by reason of the virtually extended temperature range
medium-speed gearwheels of which one meshes with the
derived from the re-heat system. Moreover, the trans
high-pressure-turbine primary pinion and the other two
mission of the relatively great torque from the low
mesh with the low-pressure-turbine primary pinion at
opposite sides of it, and three secondary pinions which
pressure-turbine primary pinion 31 is practicable mainly
by reason of the “locked train” arrangement derived from
are connected to the medium-speed gearwheels, respec
the opposed medium-speed gearwheels 35, 36 insofar that
the total low-pressure-turbine torque is divided equally
between them and the heavy radially outward thrusts
An example of the marine propulsion steam turbine
against them by the teeth of the pinion 31 are balanced
installation is illustrated by the accompanying diagram
or nearly balanced.
matic drawing, which is a plan of the installation.
From the preceding description it will be apparent
tively, and which all mesh with the large slow-speed
In the example shown, the boiler and turbine installa
tion comprises the following combination of components,
that despite the considerable difference between the tur
bines in power and the substantial difference between
namely: two steam boilers It) and 11, with superheaters
60 them in speed, the various gearing components of the
10A and 11A, respectively; a re-heater 12, the tubes 13
installation can be designed to avoid any serious inequality
of which are shown located in the path of the combus
in the gear-tooth pressures transmitted to the large gear
tion gases in their ?ow from the furnace of the boiler 11
wheel 40 by the secondary pinion 37 driven from the
to the atmosphere; a high-pressure ahead turbine 14, to
relatively low-powered higher-speed high-pressure turbine
which a high-pressure astern turbine 15 is directly con
55 and by each of the secondary pinions 38 and 39 driven
nected; a low-pressure ahead turbine 18, to which a
from the relatively high-powered low-speed low-pressure
low-pressure astern turbine 17 is directly connected; high
pressure steam piping 18 from the superheaters 10A and
In an example of the installation, it is estimated that
MA by way of stop—valves 19 and the ahead manoeuver
the following data will be obtained, the ?gures being
ing valve 20 to the high-pressure ahead turbine 14; low
rough approximations given by way’of illustration.
pressure steam piping 21 from the high-pressure turbine 60
14 to the re-heater 12 and further piping 22 from the
Turbine Turbine
re-heater to the low-pressure turbine 16; high-pressure
steam piping 23 from a stop-valve 24 on the valve 20
and the astern manoeuvering valve 25 to the high-pressure
astern turbine 15; low-pressure steam piping 26 extending 65
from the high-pressure astern turbine directly to the low
pressure astern turbine 17.
The double-reduction gearing consists of the following
combinations of components, namely: high-speed primary
(i) Inlet steam gauge pressure, in lbs. per sq. in. __
(111) Inlet steam temperature, in ° F _____________ _.
(iv) Exhaust steam temperature, in ° F__.(v) Shaft horse power __________________ __
(vi) Speed, in rpm _____________________________ _.
5, 400
5, 500
14, 600
3, 300
unit, in r.p.m _________________________________ _.
(vu) ‘Speed of medlum-speed gearwheel and pinion
pinions 30 and 31 respectively on the shafts 32 and 33 70
- of the high-pressure and low-pressure turbines; a medium
(n) Exhaust steam gauge pressure, in lbs. per sq. in_
l 28% inches of mercury, vacuum.
In the example, the difference in speed between the
turbines is taken into account not only in the three pri
mary gear pairs 36-64, 31%35 and 3i-—-36 but also in
the secondary gear pairs 37-40, 38—4€l and 39—-4t};
that is to say, the secondary pinion 37 is‘smaller than
each of the secondary pinions 38 and 3% and is rotated
at a higher speed. Nevertheless, it is practicable to have
three secondary pinions all of the same size, in which
event the primary gear pairs are designed to take into
account the whole of the di?erence in speed between the 10
In the example, the steam re-heater 12 is incorporated
in the structure of the boiler 11 and derives its heat from
the combustion gases. Any other appropriate type of
rotatable turbine shaft; speed reduction gear trains oper
atively associated with each 05 said turbine shafts to
transmit rotational motion from the turbine shafts to
said propeller shaft; the speed reduction gear train for
the high-pressure turbine comprising a primary pinion
mounted on said high-pressure turbine shaft, said primary
pinion meshing with a ?rst speed reduction gear, a sec
ondary pinion driven by said ?rst speed reduction gear
for rotational movement in conjunction therewith, a
second speed reduction gear mounted on said propeller
shaft and meshing with said secondary pinion; the speed
reduction train for the low-pressure turbine comprising a
primary pinion mounted on said low-pressure turbine
shaft, said primary pinion meshing with a pair of ?rst
re-heater may be used. For instance, the re-heater may 15 speed reduction gears along substantially diametrical por
tions of said primary pinion, a secondary pinion driven
be arranged separate from the boiler structure, or parti
by each of the said pair of ?rst speed reduction gears for
tioned from the ?ue-gas system and may derive its heat
rotational movement in conjunction‘ therewith and mesh
from high temperature steam, which may be led through
ing with said second speed reduction gear mounted on
by-pass piping from the superheater 11A of the boiler 11.
Such piping might branch from a point near the outlet 20 the propeller shaft.
of the superheater- and return from the re-heater to a
point near the superheater inlet.
2. The steam turbine marine propulsion installation
of claim 1, wherein the high-pressure turbine is adapted
to rotate at a speed of rotation greater than the speed
of rotation of the low-pressure turbine, the speed reduc
l. A two turbine steam marine propulsion installation
for driving a propeller shaft comprising, in combination: 25 tion gear train associated with the high-pressure turbine
shaft being further adapted to provide an overall speed
only two steam turbines, one of said turbines being a
reduction ratio greater than the overall speed reduction
high-pressure turbine and the other of said turbines being
ratio of the speed reduction gear train associated with
a low-pressure turbine, said low-pressure turbine being
the low-pressure turbine shaft.
adapted to receive exhaust steam from said high-pressure
I claim:
turbine, and said low-pressure turbine being further
adapted to develop more output power than that devel
oped by the high-speed turbine; a steam reheater arranged
to receive exhaust steam from said high-pressure turbine
References Cited in the ?le of this patent
to increase the temperature of said exhaust steam and
from which the steam is introduced directly into said low 35
pressure turbine; the low-pressure turbine being adapted
to produce at least twice as much output power as the
high-pressure turbine; each of said turbines having a
Pavlides ____________ __ July 30, 1918
‘Eggenberger et a1 _____ __ May 29, 1-956
Great Britain ________ __ Feb. 3, 1952
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