Improvements in Steam Turbines.
Year: 1898

page_text: Date of Application, 16th Nov., 1898-Accepted, 21st Jan., 1899
COMPLETE SPECIFICATION,
Improvements in Steam Turbines.
I, SYDNEY PITT, of Sutton, in the County of Surrey, Gentleman, do hereby
declare the nature of this invention (which has been communicated to me from
abroad by August Camille Edmond Rateau, Engineer, of St. Etienne, and Sautter,
Harlé and Company, Electrical Engineers, of 26, Avenue Suffren, Paris, both in
the Republic of France), and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement:-
This invention has for its object a multiple disc steam turbine.
The application of the power of steam by utilising its momentum rather than
its pressure, has for several years past led to the construction of various apparatus
known as steam turbines.
Experiments made by my correspondents with this class of apparatus, the results
of which agree with the indications of theory, have led to the construction of the
novel steam turbine hereinafter described.
This steam turbine is distinguished from the turbines now in use, such as the
Laval type, by the use of a series of discs which are successively traversed by the
same flow of steam.
The idea of employing several discs mounted upon the same shaft and arranged
in series is not of itself novel; it was indicated by Tournaire 45 years ago and
applied in the Parsons motor turbine 15 years ago. In these turbines, as in the
apparatus made according to this invention, the several discs are mounted upon the
same shaft and contained in a cylindrical casing. The steam enters at one end of
the casing, successively passes each disc, being suitably directed by distributors
interposed between the moveable blades, and passes out at the other end.
It is not therefore intended to claim the principle of multiple disc steam
turbines.
The present arrangement however differs in essential particulars from the pre-
ceding which differences constitute the invention. The first point is the preven-
tion of leakage of steam.
The difficulty with multiple disc turbines consists in preventing the steam, issuing
from one of the rotating discs, from passing either between the casing and the
distributor of the next disc, or between the shaft and the same distributor, an
reaching the next disc undirected, which produces only a prejudicial effect. This
loss of steam which takes place at each disc is greater in proportion to the play
between the parts.
In the present apparatus it has been sought by a novel construction, to diminish
as much as possible the amount of this play, and consequently the leakage of
steam. This leakage of steam, which has a very prejudicial effect on the efficiency
of the machine, is almost completely prevented. It is this which constitutes the
first fundamental différence between the present arrangement, and all the arrange-
ments of multiple disc turbines hitherto devised.
Again in the new apparatus full supply of steam is not given to all the discs.

page_text: The first discs only receive steam upon a portion of their circumferences, the arc
included by the distributors increasing little by little, from one disc to the next,
usually in such a manner as at last to occupy the whole circumference, so that
the first discs of the series are partially supplied with steam and the last ones are
fully supplied.
The construction of the moveable disc as well as of the fixed steam distributors,
is also peculiar and has been devised with the object of decreasing the weight of
the rotating parts as much as possible in order to facilitate the balancing of these
parts which rotate at a somewhat high speed.
In view of certain special applications, such as the propulsion of ships, this novel
arrangement has been carried out in such a manner, that an arrangement which
allows of reversing, by the mere opening of a cock, can be easily added. Lastly,
my correspondents have designed a new bearing with hydraulic packing, by means
of which the entrance of air into the condenser, or the leakage of steam around
the shaft, to which very quick rotary motion is given, is prevented.
I will now successively describe each of these arrangements.
Figure 1 is a longitudinal section of the turbine, and Figures 2, 3, 4 and 5
are four transverse half sections on the lines XX¹³, X X X X³, X* X' Figure 1.
The apparatus is contained in a metal casing D¹ generally of cast iron or steel.
This casing is provided with ribs for resisting the internal pressure. In the
apparatus shown, which is only an illustration of the system, the casing is in
three pieces D¹ D' and D³. D¹ and D³ are casings of different diameter, connected
together by the intermediate casing D³.
The turbine is closed at one end by a plate F generally of cast iron or steel.
The steam inlet pipe A terminates in this end plate. Steam passages a¹ al are
formed in the end plate for the purpose of leading the steam to the first dis-
tributor B' of the first rotating disc C¹.
The first distributor B is made up of a series of blades cast or connected together,
which occupy a portion of the inner circumference of the casing.
The turbine being on the axial system, the curvature of these blades is calculated
in such manner as to direct the steam upon the blades of the first rotating disc in
the direction of motion.
The angles and dimensions of the blades of the fixed distributor, as also those
of the blades of the rotating discs, are calculated according to theory, the co-
efficients given by practice being taken into account.
The sectional area of the passage for the steam in the first distributor, as also
in all the succeeding distributors, is calculated according to the effect to be
obtained.
The section in the several distributors goes on increasing from the first to the last
disc of the turbine, the expansion of the steam increasing its volume.
The first rotating disc and also the succeeding discs, is formed of a hub keyed
upon the shaft and upon which a conical disc c¹ of spun or raised steel, is rivetted.
The periphery of this disc is flanged parallel to the axis and the curved blades C
are rivetted to this flange. The whole is of light construction, and may be
balanced to the greatest nicety and any required strength can be given to it.
On passing the blades of the first disc e, the steam meets the blades of the
second distributor B. This distributor, as also the succeeding one, is constructed
in a different manner from the first distributor 13; the blades are fixed to the
interior of a casting fixed inside the casing. This casting is connected by arms
to a hub which surrounds the shaft without touching it, because the distributor
remains fixed. This hub is connected to the periphery B of the distributor by
a steel plate m³ suitably rivetted.
The second (and likewise the succeeding ones) distributor forms therefore a true
diaphragm, which does not allow steam to pass from the first rotating disc to the
next, by any other path than past the blades B of the distributor.
The leakage of steam is therefore reduced to a minimum, the only other path
open to the steam apart from that offered to it by the distributor, is that produced

page_text: by the play, between the hub 62 of the distributor and the shaft H of the machine
which play can be made as small as desired.
The distributor B with its hub and the diaphragm m2 forms a structure
capable of resisting the difference of steam pressure on the two sides of the dis-
tributor. This difference of pressure goes on decreasing in proportion to the
distance from the steam inlet pipe, because the steam expands in the apparatus.
The dimensions of this diaphragm, with its arms and hub, should therefore be
calculated for each rotating disc if the maximum economy in weight is desired.
In proportion as it is removed from the steam inlet, the orifice of the distributors
for each disc, should increase in size in proportion to the increase in volume of the
steam. This increase may be obtained in two ways either by increasing the arc
embraced by the blades of the distributor or by suitably increasing their height;
both methods are indicated in the drawing. The are embraced by the blades of the
distributor should as far as possible increase in a continuous manner from one end
of the turbine to the other. The steam coming from a dise to pass into the next
distributor is thus prevented from striking against a solid portion of the dis-
tributor and thereby losing the velocity it still possesses at its exit from each
rotating disc. This residual velocity should on the contrary, be utilized as much
as possible, for it increases the efficiency of the the apparatus.
In the drawing 15 successive discs are of the same size and are enclosed in the
casing D. The remaining ten discs are of much larger size and are enclosed in
the casing D³. The increase in diameter is rendered necessary by the increase
in volume of the steam which expanda. By increasing the diameter, the orifices
of the distributors are enlarged without the necessity of increasing the height of
the blades of this distributor in an exaggerated manner which it would be necessary.
to do if the same diameter of disc were employed throughout.
In the casing D³, for the first five discs Nos. 16 to 20 the construction of the
distributor is the same as those in the first turbine, the arc embraced by the blades
increasing from one to the other. The height of the blades may also be modified
if it be deemed necessary. The steam, at its exit from the last small disc No. 15,
passes to the first large disc No. 16 through a passage formed inside the casing D³,
it passes from dise to disc until the end of the turbine, and then passes out into
the condenser or into the atmosphere through an outlet K, the dimensions of
which should be calculated according to the expanded volume to be exhausted.
In the apparatus shown as illustrating the invention, the five last large discs c
to are constructed in a different manner, the moveable blades instead of being
fixed separately upon each disc, are all fixed upon a single drum keyed upon the
shaft and carry two plates and forming ends. It results that this drum is
submitted to the difference of the pressures existing behind the disc and in front
of the last disc. The latter pressure is the exhaust pressure. By means of this
drum therefore which is subjected to a longitudinal thrust, another equal thrust
produced on the shaft of the machine can be balanced. This case arises when the
turbine is employed to propel a ship.
The thrust of the screw may in this manner be balanced by combining together
a suitable number of the last discs of the machine.
This method of construction thus allows the thrust of the block screw to be
dispensed with or at least allows of its size being in a great measure reduced.
In the particular case just enunciated and which is shown in the drawing, the
construction of the last distributors B to B is different. The distributors are
merely fixed to the easing, they no longer carry either a hub or diaphragm. The
consequence is that the leakage of steam which is reduced to a great extent by
the before described method of construction now becomes of greater importance.
This leakage takes place at the inner periphery of each of the distributors. But in
reality the sectional area of the orifices of the distributors being much larger by
reason of the expanded volume of the steam itself being greater, the relative amount
of leakage for these latter distributors remains about the same.
This consideration allows therefore a turbine to be made for the propulsion of

page_text: ships, in which the thrust of the screw is balanced without the efficiency of the
apparatus being greatly affected.
At the other end of the turbine there is placed a supplementary wheel N which
is arranged for reversing. The blades of this wheel are fixed in the annular
trough which is in one piece with the end of the drum and receive the steam
from a series of cylindrical distributors or tuyeres M supplied from a cylindrical
collector L.
The blades of the reversing disc are directed in the contrary direction to those
for the direct movement, it is sufficient therefore to open the cock of the collector L
in order to rotate the machine in the contrary direction. The power thus developed
in the backward motion is less than that produced in the forward motion but this
consideration is not of great importance; in general especially when the propulsion
of ships is in question, reverse working is never carried out at a speed equal to that
of the forward movement.
The steam after passing out from the blades of the reversal wheel, is guided by
the curvature of the annular trough into the exhaust collector K.
The single shaft H of the turbine is carried by three bearings, one bearing G
at the end of the machine where steam is admitted is supplied with oil under
pressure, the intermediate bearing G is placed nearly in the middle of the machine,
and is fed with oil under pressure through a pipe g² and lastly a third bearing Ga
is placed at the exhaust end of the machine. This bearing is of peculiar construc-
tion. It is supplied with oil under pressure through pipes gs. The oil goes into
an annular channel in the bush and its pressure is calculated in such a manner as
to make a hydraulic joint between the two ends of the bearing. These two ends
are submitted to two different pressures, on one hand to the atmospheric pressure
and on the other hand the vacuum if working with a condenser. The hydraulic
joint thus prevents the entry of air into the condenser. If however the exhaust
leads to the open air the two ends of the bearing are usually at the same pressure.
However if this pressure were slightly greater on the inside of the machine, steam.
would leak which leakage is prevented by the hydraulic joint.
The oil admitted by the pipe escapes at both ends of the bearing through the
pipes g and g connected by a pipe with reservoirs from which oil is drawn by
means.of a pump.
This arrangement of bearing does away with the use of metal joints or graphite
bearings which are extremely difficult to adjust at the speeds at which steam
turbines run.
The working of the steam turbine is easily understood.. A cock or valve is
placed upon the steam inlet. This cock may be actuated automatically or by hand.
As soon as it is open the steam penetrates successively past the several discs and
puts the turbine in motion; the steam expands little by little and passes outwards
through the orifice K at the predetermined pressure of exhaust. The speed may
be regulated by the pressure that is to say by opening the steam inlet cock more or
less.
To reverse, it suffices to close the inlet cock on the pipe A and to open the cock
on the pipe L. The reversal disc, which when rotated forward has no propelling
effect, now receives steam in such a manner as to rotate in the opposite direction,
drawing with it all the other dises which in this direction have no motor effect.
The steam which passes out from the reversal disc passes directly into the exhaust
orifice K. It will therefore be seen that in this arrangement, the the forward
running or the reversal is obtained solely by the action of two cocks.
Turbines on this system may be applied for driving dynamo machines, the pro-
duction of electric energy, the propulsion of ships and the like, in a word all the
applications to which a steam engine is put.
Having now particularly described and ascertained the nature of the said in-
vention and in what manner the same is to be performed, I declare that what I
claim is:
1. A multiple diso steam turbine in which each disc is preceded by a distributor

page_text: having fixed wings, the orifices of which are suitably calculated; this distributor
itself forming a diaphragm separating each disc from the next, thus reducing
to a minimum the leakage of steam and the loss in efficiency which results from it.
2. In the construction of such turbines the use of moveable discs of spun or
raised metal supporting curved blades rivetted to the periphery in such a manner
as to produce a light and perfectly balanced whole, the steam being distributed
by means of fixed distributors the blades of which are attached to the metal piece
which serves as their support.
3. The combination with the preceding arrangement of a reversal disc placed
at the end of the steam outlet and receiving the steam under pressure from a special
distributor fixed upon the end at the rear of the machine, this reversal disc being
calculated in such a manner as to give to the apparatus a suitable speed, especially
in the case of marine propulsion.
4. The combination with the preceding arrangement or with any other system,
of bearings with automatic lubrication under pressure placed inside the turbine
and of a bearing likewise under pressure which prevents by an annular hydraulic
joint either the entrance of air to the condenser or the outlet of steam as described
above.
All substantially as described and illustrated in the drawings annexed.