US2684227A

US2684227A - Hydraulic turbine

Info

Publication number: US2684227A
Application number: US217778A
Authority: US
Inventors: Seewer Paul Werner
Original assignee: English Electric Co Ltd
Current assignee: English Electric Co Ltd
Priority date: 1950-04-14
Filing date: 1951-03-27
Publication date: 1954-07-20
Anticipated expiration: 1971-07-20

Description

July 20, 1954 P. w. SEEWER HYDRAULIC TURBINE Filed March 27. 1951 Patented July 20, 1954 HYDRAULIC TURBINE Paul Werner Seewer, Rugby, England yassignor to :The English Electric Company Limited, London, England, a British company Application March 27, 1951, Serial No. 217,778

Claims priority, application Great Britain April 14, 1950 3 Claims.

The invention relates to hydraulic turbines of the impulse Wheel type, and has the object of limiting the runaway speed of such turbines.

According to the main feature of the invention the portions of the water jet which traverse the runner unused at overspeeds thereof are deflected towards the backs of the runner buckets by means of a duct having its entrance in the line of the jet and its exit directed against the back of the buckets, i. e. in the direction opposite to their rotation, which duct is closed or sealed during ordinary operation of the turbine at its entry by a bursting diaphragm which is so dimensioned as to withstand the action of spray water but to be burst open by the impact of the portions of the jet passing through the buckets of the runner unused at a predetermined overspeed. Thereby spray water is prevented from being directed unintentionally against the backs of the buckets and from producing an adverse effect on the efiiciency of the turbine in normal operation, while a powerful braking action is exerted on the latter upon reaching a predetermined overspeed condition.

In order that the invention may be better understood and readily carried into effect an embodiment thereof will now be described by way of example with reference to the accompanying drawing which is a diagrammatic side elevation of the relevant part of an impulse wheel type hydraulic turbine.

In the casing I the runner 2 is journalled on its shaft 3 and carries buckets 4. A jet of water is directed tangentially on to the buckets 4 from a nozzle 5 attached to the casing I which nozzle is controlled by a needle valve 6. A curved duct 1 is arranged in the casing l opposite the nozzle 5 the entrance of which duct lies in the projected path of the water jet, and the exit of which is directed against the back of the buckets 4.

The entrance of the duct 1 is sealed by a bursting diaphragm 8 which is so dimensioned as to withstand the action of the spray of water hitting it incidentally, but to be burst open by the portions of the jet passing unused through the buckets at a predetermined overspeed.

These portions of the water are then directed by the duct 1 against the back of the rotating buckets 4 and exert a powerful braking action on the runner 2 which prevents it from attaining an excessive and dangerous overspeed. For example, the runaway speed of an impulse type turbine which has been hitherto of the order of 80% above the normal speed, can now be re- 2 duced to or even 50% of the latter, whereby the stresses in the runner, the buckets and the fixtures are reduced to 80% and even Thereby it is made possible to build impulse wheel type turbines of high output (say 140,000 kw.) for an ordinary operational speed of 300 R. P. M. instead of 200 R. P. M. whereby considerable savings in first costs both of the turbine and of an electric alternator driven by it can be made.

Impulse wheel type turbines having more than one jet per runner can be provided with a deflecting duct for each jet, or alternatively such ducts are provided for one or some of these jets only, as indicated in chain dotted lines in the drawing.

The bursting diaphragm is preferably made up of a material which does not splinter or is much softer than the material of the runner or of the casing, so that it cannot damage these components. Wood, artificial plastics, rubber or soft metal such as lead are considered suitable materials.

While I have described hereinabove what may be considered a suitable embodiment of my invention, I do not wish to be limited to the exact dimensions and constructions shown, for obvious modifications will occur to a person skilled in the art.

What I claim as my invention and desire to secure by Letters Patent is:

1. A hydraulic turbine comprising in combination: a casing, an impulse wheel journalled for rotation inside the said casing, a plurality of buckets fixedly connected to said impulse wheel, a nozzle attached to said casing and directed towards the concave side of the said buckets tangentially to the said impulse wheel, a curved duct fixed to the said casing with its entrance in alignment with the said nozzle and with its exit directed towards the convex backs of the said buckets, and a diaphragm sealing in normal operation the entrance to the said curved duct and consisting of a material resisting the action of the spray of water hitting it incidentally but to be burst open by the portions of the jet of water passing through the buckets at a predetermined overspeed.

2. A hydraulic turbine as claimed in claim 1 wherein the said bursting diaphragm consists of a splinter-free material softer than the material of the said casing.

S. A hydraulic turbine comprising in combination: a casing, an impulse wheel journalled for rotation inside the said casing, a plurality of buckets fixedly connected to said impulse Wheel, at least two nozzles attached to the said casing each directed towards the concave side of the said buckets at difierent positions tangentially to the said impulse Wheel, at least one curved duct fixed to the said casing with its entrance in alignment with one of the said nozzles and with its exit directed towards the convex backs of the said buckets, and a diaphragm sealing in normal operation the entrance to the said curved duct and consisting of a material resisting the action of the spray of water hitting it incidentally but to be burst open by the portions of the jet of water passing through the buckets at a predetermined overspeed.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,307,703 Sagberg et a1 June 24, 1919 1,498,096 Herr June 17, 1924 1,837,570 Moody Dec. 22, 1931 FOREIGN PATENTS Number Country Date 46,083 Switzerland Apr. 8, 1909