Improvements in Reversing Steam Turbines.
Year: 1897

page_text: Date of Application, 12th Jan., 1897
Complete Specification Left, 12th Oct., 1897-Accepted, 12th Jan.,
1898
Improvements in Reversing Steam Turbines.
We, The Honourable CHARLES ALGERNON PARSONS, Engineer, of Heaton Works,
Newcastle-on-Tyne, in the County of Northumberland, and ALAN ARCHIBALD
CAMPBELL SWINTON, Engineer, of 66, Victoria Street, Westminster, London, S.W., do
hereby declare the nature of this invention to be as follows:-
Our Invention relates to steam turbines which require to be reversed, such as
turbines for marine propulsion, locomotives, auto-cars, and for other purposes where a
reversing turbine is required.
In steam turbines as at present constructed certain difficulties are found in
effectively reversing the direction of rotation. In one method of reversing already
adopted by one of the present applicants a special set of reversing jets and blades are
applied to a marine steam turbine, and when it is desired to reverse the engine the
steam supply is cut off from the main turbine, and sent through the reversing blades
or jets only. This device enables the turbine to be reversed, but the reversing power
is not great, as it is impossible to use any great number or series of reversing
turbines without increasing complexity and diminishing the efficiency of the turbine
when running in its normal direction.
The object of our invention is to overcome the difficulties and complexities of the
ordinary method, and to obtain a powerful reversal of a steam turbine without
appreciable complication of its mechanical construction.
Our invention consists in reversing the direction of flow of steam through a steam
turbine when it is desired to reverse the direction of its rotation, and further in the
suitable arrangement of turbine parts and steam directing valves to produce the
desired reversal in the best way.
In carrying our invention into effect according to one modification as it would be
applied to engines at present operating a high speed torpedo boat, where we have
arranged three screw propeller shafts, each of these shafts being rotated by a separate
turbine, and where these turbines are arranged in series, and the rotating and fixed
blades in each turbine are arranged to produce the now well known expanding action
from one set of blades to another. We reverse by reversing the direction or flow of
steam in each turbine, that is, we so arrange our valve connections that in the first
or high pressure turbine the high pressure steam enters at the low pressure end,
passes through the turbine, and out at the high pressure end, from whence it flows to
the low pressure end of the next turbine, and so on, until the steam has passed from
turbine to turbine through the series of three. We have found that by this reversal
of the flow of steam the turbines are reversed with considerable power. In the
present case, however, the steam flows through each turbine from larger area blades
to sinaller area blades, and consequently considerable power is lost. The arrangement,
however, is extremely simple, and in many cases is sufficiently effective for the purpose
of reversing.
In the case, however, where there are four turbines operating four shafts the
proportioning of the blades is more favourable, and so also for still larger numbers of
turbines. Sometimes also the turbines may be arranged two or more on one shaft,

page_text: and a larger or smaller number of stages in the expansion may be included in the
reversals.
In an effective modification of our invention we arrange our steam passages and
ports so as to reverse between each set of blades, or each step in the series of blades,
so that on the whole, speaking broadly, when reversing the steam passes from a set
of blades of smaller area to a set of larger area. This arrangement gives increased
power in reversing but increases of course the complexity of the steam
connections.
The invention is based upon our discovery that when the direction of the flow
of steam is reversed in turbines now well known as the Parson's turbines, that
a reverse rotary motion is imparted to the motor. This reversing power of the
motor is, however, dependent on the form of turbine blades or steam apertures, as
well as upon the proportional dimensions of the turbines of the series, and we find
that it is desirable to somewhat modify the form of blade usually adopted on the well
known Parsons turbine when a considerable amount of reversing power is
required.
In ordinary turbines the leading edges of the rotating blades are generally well
hooked to catch the steam when going forward, that is, the space between the blades
is narrowed towards each ejecting edge, and widened at the place where impact occurs
from the previous set of blades. This construction however, tends to stop the
rotating action of the issuing steam when it is caused to flow in the reverse direction,
and in reversing turbines we prefer to use generally a flatter form of blade than is
usually adopted. In some cases we use a blade with one side quite flat or with a very
small curvature in either direction, and the other side suitably curved in order to
give as great rotary motion as possible in either direction of steam flow.
:
We are, careful, however, in so modifying our blades to minimise the loss of
efficiency when going forwards to the utmost. Where very great reversing power is
desired, however, we sometimes purposely sacrifice some of the economy on the
forward rotation for the purpose of obtaining great reversing power.
Thus where moderate backing power is required we retain a moderate curve or book
at the leading edge. Where greater backing power is required we somewhat diminish
the opening at the same edge, and where the maximum backing power is required we
arrange to give equal force forwards and backwards by straight blades having equal
taper at both edges.
In some cases we shape the edges of the blades at the usual discharge aperture so
that when backing is required the steam impinged upon concavitives formed in the
back of each blade, and by this device we improve our efficiency when reversing.
It is to be distinctly understood that generally speaking we prefer that even
in reversing, the flow of steam may pass from one series of blades to another series,
always from a series of smaller area to a series of larger area. Sometimes, however, for
the sake of simplicity, we do not do this, but simply pass the steam in a reverse
direction right through the turbine from the low pressure end to the high pressure
end.
When two or more motors are worked in series or series parallel on the steam, then
by reversing the direction of flow of steam in any one or more of these motors we can
produce reversing power. Three motors, for instance, working three separate screw
shafts may be so arranged that by reversing the flow in one or more the ship may be
manoeuvred in order to turn sharply, in the same way as ordinary twin or triple screw
vessels with ordinary engines are manoeuvred.
Additional valves may also be added between any motor and the main steam supply
or condenser so that any motor may be independantly worked.
Reversing valves are arranged to control the flow of steam as we have described,
and sometimes we arrange reversing valves of the butterfly type so that in mid
position they form a direct bye pass for the steam. By placing the reversing valve
in mid position the motor will be stopped or cut out in case of accident, because the
steam will have free access to both sides of the blades, or the motor may be completely
cut off from the steam, and the steam will pass right through that valve to the next

page_text: motor without operating the blades. The aperture of the bye pass may be full, or it
may be so constructed that the resistance to the steam in mid position may be equal
to that of the turbine cut out.
Any form or governor may be used to operate the valves singly or in groups, or
altogether, steam relays or other relays or any form of marine governor may be used
in combination with these valves. *
The valve we have described as a reversing valve may be a simple two-way butterfly
valve so arranged that when the steam passes on one side it flows through the turbine
in the correct direction, and the exhaust from the turbine passes away by the other
side.
When the valve is placed in a mid position, as we have described, the steam
flows through the valve without passing the turbine, and when the valve is placed
in the opposing diagonal position the steam flows in the reverse direction.
A piston valve or ordinary D slide valve may also be used instead of the butterfly
valve.
Suitable levers and controlling gear, and hydraulic or steam power is used for
operating the valves.
We, The Honourable CHARLES ALGERNON PARSONS, Engineer, of Heaton Works,
Newcastle-on-Tyne, in the County of Northumberland, and ALAN ARCHIBALD
CAMPBELL SWINTON, Engineer, of 66, Victoria Street, Westminster, London, S.W.,
do hereby declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:
Our invention relates to steam turbines which require to he reversed, such as
turbines for marine propulsion, locomotives and auto-cars, and it is applicable to
other purposes where a reversing turbine is required.
In steam turbines as at present constructed certain difficulties are found in
effectively reversing the direction of the rotation. In one method of reversing
already adopted by one of the present applicants a spécial set of reversing jets and
blades is applied to a marine steam turbine, and when it is desired to reverse the
engine the steam supply is cut off from the main turbine, and sent through the
reversing blades or jets only. This device enables the turbine to be reversed, but
the reversing power is not great, as it is impossible to use any great number or series of
reversing turbines without increasing complexity and diminishing the efficiency
of the turbine when running in its normal direction.
The object of our invention is to overcome the difficulties and complexities of the
ordinary method, and to obtain a powerful reversal of a steam turbine without
appreciable complication of its mechanical construction.
Our invention consists in reversing the direction of flow of steam through a steam
turbine when it is desired to reverse the direction of its rotation, and further in the
suitable arrangement of turbine parts and steam directing valves to produce the
desired reversal in the best way.
In carrying our invention into effect according to one modification as it would be
applied to engines at present operating a high speed torpedo boat; where we have
arranged three screw propeller shafts, each of these shafts being rotated by a separate

page_text: turbine, and where these turbines are arranged in series, and the rotating and
fixed blades in each turbine are arranged to produce the now well known expanding
action from one set of blades to another; we reverse by reversing the direction or
flow of steam in each turbine that is, we so arrange our valve connections that in
the first or high pressure turbine the high pressure steam enters at the low
pressure end, passes through the turbine, and out at the high pressure end from
whence it flows to the low pressure end of the next turbine, and so on, until the
steam has passed from turbine to turbine through the series of three. We have
found that by this reversal of the flow of steam the turbines are reversed with
considerable power. In the present case, however, the steam flows through each
turbine from larger area blades to smaller area blades, and consequently considerable
power is lost. The arrangement however however, is extremely simple, and in many
cases is sufficiently effective for the purpose of reversing.
In the case, however, where there are four turbines operating four shafts, the
proportioning of the blades is more favourable, and so also for still larger numbers
of turbines. Sometimes also the turbines may be arranged two or more on one
shaft, and a larger or smaller number of stages in the expansion may be included in
the reversals.
In an effective modification of our invention we arrange our steam passages and
ports so as to reverse between each set of blades, or each step in the series of blades;
so that on the whole, speaking broadly, when reversing, the steam passes from a set
of blades of smaller area to a set of larger area. This arrangement gives increased
power in reversing, but increases of course the complexity of the steam connections.
The invention is based upon our discovery that when the direction of the flow of
steam is reversed in turbines now well known as the Parsons' turbines, that a reverse
rotary motion is imparted to the motor. This reversing power of the motor is
however, dependent on the form of turbine blades or steam apertures, as well as
upon the proportional dimensions of the turbines of the series, and we find that it is
desirable to somewhat modify the form of blade usually adopted on the well known
Parsons' turbine when a considerable amount of reversing power is required.
In ordinary turbines the leading edges of the rotating blades are generally well
hooked to catch the steam when going forward, that is, the space between the
blades is narrowed towards each ejecting edge, and widened at the place where
impact occurs from the previous set of blades. This construction however, tends to
stop the rotating action of the issuing steam when it is caused to flow in the reverse
direction, and in reversing turbines we prefer to use generally a flatter form of
blade than is usually adopted. In some cases we use a blade with one side quite
flat or with a very small curvature in either direction, and the other side suitably
curved in order to give as great rotary motion as possible in either direction of steam
flow.
We are careful, however, in so modifying our blades, to minimise the loss of
efficiency when going forwards to the utmost. Where very great reversing power is
desired, however we sometimes purposely sacrifice some of the economy on the forward
rotation for the purpose of obtaining great reversing power.
Thus where moderate backing power is required we retain a moderate curve or
hook at the leading edge. Where greater backing power is required we somewhat
diminish the opening at the same edge, and where the maximum backing power is
required we arrange to give equal force forwards and backwards straight blades having
equal taper at both edges.
In some cases we shape the edges of the blades at the usual discharge aperture so
that when backing is required the steam impinges upon concavities formed in the
back of each blade, and by this device we improve our efficiency when reversing.
It is to be distinctly understood that generally speaking we prefer that even in revers-
ing the flow of steam may pass from one series of blades to another series, always from a
series of smaller area to a series of larger area. Sometimes, however, for the sake of
simplicity, we do not do this, but simply pass the steam in a reverse direction right
through the turbine from the low pressure end to the high pressure end. When two

page_text: or more motors are worked in series or series parallel on the steam, then by
reversing the direction of flow of steam in any one or more of these motors we can
produce reversing power. Three motors, for instance, working three separate screw
shafts may be so arranged that by reversing the flow in one or more the ship may
be manoeuvred in order to turn sharply, in the same way as ordinary twin or triplė
screw vessels with ordinary engines are manoeuvred.
Additional valves may also be added between any motor and the main steam
supply or condenser, so that any motor may be independently worked.
Reversing valves are arranged to control the flow of steam as we have described,
and sometimes we arrange reversing valves of the butterfly type so that in mid
position they form a direct bye-pass for the steam. By placing the reversing valve in
mid position the motor will be stopped or cut out in case of accident, because the
steam will have free access to both sides of the blades, or the motor may be
completely out off from the steam, and the steam will pass right through that valve
to the next motor without operating the blades. The aperture of the bye-pass may
be full, or it may be so constructed that the resistance to the steam in mid position
may be equal to that of the turbine cut out.
Any form of governor may be used to operate the valves singly or in groups, or
altogether, steam relays or other relays, or any form of marine governor may be used
in combination with these valves.
The valve we have described as a reversing valve may be a simple two-way.
butterfly valve so arranged that when the steam passes on one side it flows through
the turbine in the correct direction, and the exhaust from the turbines passes away
by the other side. When the valve is placed in a mid position as we have described;
the steam flows through the valve without passing the turbine, and when the valve is
placed in the opposing diagonal position the steam flows in the reverse direction.
A piston valve or ordinary D slide valve may also be used instead of the
butterfly valve.
Suitable levers and controlling gear, and hydraulic or steam power is used for
operating the valves.
Referring to the three accompanying sheets of drawings ;-
Figure 1 is a plan part in section illustrating the application of our invention to
two turbines operating in series and actuating twin screws.
Figure 1 shows a reversing valve in middle position.
Figure 2 is a diagram illustrating blades with a moderate curvature, and showing
the path of the steam while going ahead and reversing.
Figure 3 is a similar diagram, showing blades with less curvature.
Figure 4 is a similar diagram showing straight blades.
Figure 5 is a diagram showing straight blades with hollows upon which the steam
impinges while the motor is revolving in either direction.
Figure 6 is a plan illustrating the application of our invention to three turbines
operating in series, and actuating three screw shafts.
Figure 7 is a plan illustrating the application of governors to the three turbines
shown in Figure 6.
In Figure 1, A is the high pressure turbine, and B the low pressure; the high
pressure steam from the boiler is admitted to the turbine A by way of the pipe H,
and for going ahead the steam passes on one side of the reversing valve A¹ which is
of the butterfly type, to end of the steam turbine, by way of the passage E, as shown
by the arrow a. The steam then passes through the various sets of moving and
fixed turbine blades to the opposite end of the turbine, and thence it discharges to
the passage E¹, and passes the other side of the reversing valve A' as shown by the
arrow to the pipe D communicating with the low pressure turbine B. The steam
passes through that turbine for going ahead by one side of the reversing valve B¹
to one end of the turbine B as shown by the arrow c, thence through the fixed and
moving blades of the turbine to the other end, from which end it discharges by the
passage F past the opposite side of the reversing valve B¹ to the exhaust pipe G
as indicated by the arrow d. The reversing valves A¹ B¹ thus direct the steam in

page_text: combination with the passages E E and F F! so that the steam admitted to each
turbine passes on one side of the reversing valve while the steam discharged from it
passes on the other.
When it is desired to reverse both turbines the reversing valves A¹ B1 are placed
in the positions indicated in dotted lines, and then the steam passes to the low
pressure end of each of the turbines shown, and discharges at each high pressure end.
When one of the turbines is required to go ahead while the other reverses, one
reversing valve is operated for that purpose. When it is desired to cut one turbine
out of action the reversing valve is moved to its middle position as shown in Figure 1^.
When in this position the steam passes on both sides of the valve A¹ or B¹ without
entering the ports E or FF1 as determined by the particular turbine to be cut out
of action. When the turbine A is so cut out of operation the steam from the boiler
passes by way of both sides of the valve A¹ to the pipe D, and thence to the turbine B.
The dimensions of the valve A' are preferably so proportioned that when it is placed
in the middle position the steam is throttled on its way to the pipe D to an extent
equal or nearly equal to the resistance of the turbine A when in action. The same
remarks apply to the proportioning of the reversing valve B¹. A² and B2 are the
propeller shafts.
Figure 2 shows diagramatically part of a row of fixed blades f and rotating blades r;
these blades are moderately curved, and converge in the direction in which the steam
flows when the turbine is going ahead. When so rotating in the normal direction
the steam passes between the fixed blades f in the direction of the arrow l, impinges
upon the concave sides of the rotating blades 7, and discharges from them continuing
in the direction of flow. The moving blades then rotate in the direction of the
arrow 3:
When the turbine is to be reversed the steam is caused to flow in the direction of
the arrow 2, and then it impinges on the convex sides of the blades, and travels in
the direction in which the blades diverge. The turbine then rotates in the direction
of the arrow 4. The power developed during reverse running with blades as in
Figure 2 is sufficient for some purposes, but is much less than the power obtained
when running forwards.
Figure 3 shows blades less curved having less converging and therefore less
diverging effect, so that a greater power is developed while reversing. In
Figures 2, 3, 4 and 5 the fixed row of blades is indicated by f, and the rotating
by ; the arrows are also numbered similarly when the direction of flow of steam
and rotation of turbine are similar.
In Figure 4 the blades are straight and parallel to each other so that equal power
is developed while rotating in both directions.
Some loss of effect is occasioned by the straight or nearly straight blades, and the
form of blade shown at Figure 5 is intended to obtain greater economy while at the
same time giving equal power in both directions. Here the blades are straight, but
opposite convexities g h are formed on each blade, so that in either direction of flow
the steam jets impinge on a concavity. This is shown by the arrow 1 splitting up
as it impinges on the concave surface g of one of the row of moving blades r. The
turbine rotates in the direction of the arrow 3 when the steam flows as indicated by
the arrow 1, and in the direction of the arrow 4 when the steam flows, as shown by
the arrow 2. In both cases it will be observed that the steam impinges on a concave
surface.
Figure 6 shows in plan three turbines A B C, arranged with regard to the steain
flow, in series. A is the high pressure B the intermediate, and C the low pressure
turbine. The reversing valves A¹ B' and C¹ control the direction of flow through
the respective turbines in the manner already described. The high pressure steam
enters by the pipe H to either end of the turbine A as determined by the position of
the reversing valve A¹; from A it passes by the pipe D to the turbine B similarly
controlled by the reversing valve B¹, and thence by the pipe G to the low pressure
turbine C directed by the reversing valve C¹. From the turbine C it passes to the

page_text: condenser K by the pipe I. A2 B2 C² are the propeller shafts; E'E' and F F are the
steam passages controlled by the reversing valves; similar passages are provided for
the low pressure turbine C, but they are not marked.
The reversing valves A¹ B¹ C¹ are operated together by links A3 B³ connected to
suitable levers. The valves may however, be separately operated. In Figure 6 the
valves are set for going ahead and the direction of the flow of steam for this condition
is shown by the arrows.
Figure 7 shows three turbines actuating three shafts as in Figure 6 similar parts
are similarly lettered. The turbines however are governed in accordance with my
invention.
Three centrifugal governors A+ B+ and C+ are shown on the plan, they are operated
from the shafts A B C by worm gearing or in any usual manner. They control
steam valves by means of the valve stems A5, B5 and C5, these valves supply steam
cylinders L LL2 and they operate levers M, M M² in either direction. The lever M
controls a throttle valve admitting steam to the high pressure turbine A. The
levers M M2 control the reversing valves B¹ C¹ and so determine whether the steam
actuates, passes by or tends to reverse the respective turbines.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :-
1, The method of reversing the direction of rotation of a steam turbine by
reversing the direction of flow of the steam through the blades; the same blades
being used for actuating the turbine in both directions, as herein set forth.
2,--A reversing steam turbine, reversed by the method claimed in the preceding
claim, and having two, three or more turbines arranged in series or compound parallel
on the steam, provided with reversing valves which may either operate together or
reverse the direction of steam flow in one or more of the turbines substantially as
described.
3, In steam turbines reversed by the method claimed in the first claim, blades
constructed of a moderately concave form, substantially as and for the purposes
herein before described.
4,-In steam turbines reversed by the method claimed in the first claim, straight
blades to provide equal force in both directions of steam flow, substantially as and
for the purposes herein before described.
5, In steam turbines reversed by the method claimed in the first claim, blades
having opposite concavities to secure equal force in both directions of steam flow
while providing concave surfaces for the impingement of the steam jets in both
directions, substantially as herein before described with reference to Figure 5 of the
drawings.
6, In steam turbines reversed as claimed in the first claim a two way valve of the
butterfly type so arranged that when placed in either of two extreme positions steam
is applied to the turbine on one side of the valve, and discharged on the other, but
in which the direction of flow of the steam through the turbine depends on the
particular position; the valve being also arranged so that when in mid-position the
steam flows past both sides of the valve and does not flow through the turbine,
substantially as described.
7, In a reversing steam turbine having a valve or valves as claimed in Claim 6,
arranging the valve so that while in mid-position it throttles the steam to the same
extent as the turbine would, so that the steam is supplied to the next turbine in
series as if the turbine which has been cut out were in operation, substantially as
hereinbefore described.
8, The combination of turbines and valves herein before described with any known
form of "Marine" governor or ordinary governor worked from the engine shaft; the
valves being so arranged that each or any number of the turbines can be governed
independently for the purpose of preventing racing at sea.
9, The reversing steam turbines hereinbefore described and illustrated at

page_text: Figures 1 and 6 either with the reversing valves linked together, or operating
independently.
Dated this 11th day of January 1898.
.
MARKS & CLERK,
18, Southampton Buildings, London, W.C., and
13, Temple Street, Birmingham,
Agents.