US2751190A - Hydraulic turbines - Google Patents

Description

June 19, 1956 P. DERIAZ HYDRAULIC TURBINE-S Filed April 5. 1954 AITORNEY:

2,751,190 HYDRAULIC TURBINES Paul Driaz, Rugby, England, assignor to The English Electric Company Limited, London, England, a British company Application April 5, 1954, Serial No. 420,987 Claims priority, application Great Britain April 24, 1953 7 Claims. (Cl. 253-143) The invention relates to hydraulic turbines. Such turbines of the fixed propeller type or of the feathering runner vane type which have a high specific speed are liable to attain runaway speeds in the order of magnitude up to three times and even more the normal speed within a few seconds after a complete relief from load when the speed governor is out of action. This would involve an increase in centrifugal stresses to about nine times or more the normal stresses at synchronous speed which might cause complete destruction or at least severe damage to the turbine and to the electric generator driven by the same, as well as to the building.

tracted in the propeller body but which emerge therefrom when the centrifugal loads exceed a limit defined by some breaking link, and which then receive from the water vortex fiowmg to the propeller vanes a torque which draulic turbine showing a hydro-brake vane according to the invention,

Fig. 2 is a cross section along the line 2-2 of Fig. 1,

and

Fig. 3 is a part plan view in section along the line 3-3 of Fig. 1.

Figs. 4 and 5 are part-sections corresponding to Figs. 1

and 3 respectively and showing the ends of the hollow hydro-brake vanes in a slight modifications.

The runner body 1 is attached to the vertical turbine shaft 2 and carries a numbe of hydro-brake ring segis opposed-to the torque applied to the latter whereby an effective limitation .of the overspeed is attained.

Retaining the hydro-brake vanes in the retracted position until a predetermined overspeed condition is reached, and automatically retracting the said vanes when the speed has dropped to a considerably lower value, by means of springs, has also been proposed.

According to the present invention the hydro-brake vanes of a hydraulic vertical shaft turbine are made hollow and are partly filled with an easily movable inertia medium, for example a heavy liquid or small solid bodies, mercury being a typical example of a heavy fluid, and steel balls of small solid bodies. This medium, on the turbine reaching a predetermined overspeed condition, assembles by centrifugal force on the inwardly sloping inner face of the outer wall of the hollow hydro-brake vane and tilts the same into the operative position, in which the said medium assembles inside the tip of the hollow hydro-brake vane and retains the latter in its operative position, until the speed of rotation has dropped to a predetermined low value at which the said medium can flow by gravity to a position inside of the said pivot point, and tilt the hydro-brake vane back into the retracted position.

Preferably the braking torque opposite the driving torque on the propeller blades is produced by making the hydro-brake vanes box-shaped with a flange at one of its upstream edges only, for the deflection of the water vortex.

'Ihe hydro-brake vanes are preferably hinged each about an axle mounted in a separate segment of a hydrobrake ring, each such segment being individually attached to, and removable from, the turbine runner body.

In order that the invention may be clearly understood and readily carried into effect, an embodiment thereof will now be described by way of example with reference to the accompanying drawing, in which:

Fig. l is an axial part section of the runner of a hyments 3 which are attached to it by screws 4 individually detachable. In each segment 3 an axle 5 is pivoted which is fixedly connected to a hollow hydro-brake vane 6 of box-shape (Fig. 2), having one edge, 6' chamfered and the other provided with a flange, 6", whereby the deflection of the water vortex is effected in the projected position required for producing the braking torque. The outside wall 6" of the hollow-brake vane slopes down intially below the pivot'axis of the hydro-brake vane 6,

and consequently does not produce any appreciable mo As the turbine rotates at ordinary speed, the medium assumes by centrifugal force a free surface 8 indicated the medium climbs up the inner face of the outside wall 6" of the vanes 6 by centrifugal action and assumes a free level 9 indicated in chain-dotted lines. In this The stops 3 and 3", respectively, movement of the hydro-brake vane 6.

Instead of mercury another liquid of high density could be used, the quantity required being proportionally larger as the density is lower than of mercury.

Alternatively, as shown in Figs. 4 and 5 small and easily movable solid bodies 10', for example steel balls as used for ball hearings, or shot, could be used, which for the purposes of the present invention behave substantially alike to a liquid.

Adjustment of the steeply inclined sloping position of the inner surface 6" in the retracted position of the vane 6 fixes the tripping speed at which the hydrobrake vanes come out, and of the moderately inclined sloping posilimit the tilting Patented- June 19, 1956 tiorr of the-same surfzicefi at-the projected position determines the speed 1 at. which? the said .-hydro-brake.vanes\ easily movable inertia medium partly filling the saidfhol low'hydro-brake vanes, each-of 'the saidvanes having an outside wall sloping inwardly at a very steep-angle ina normal working position in'wh'ich the said medium assumesa position below the pivot pin of the hydro-brake vanes and keepsthe-same retracted in the said runner, anoverspeed' conditionv in whi'ch the said medium rises along the said. steeplv'slopingwall above the said pivotpin andtilts-the saidhydro-brake vane out of the said' runner into the water vortex; aibraking position in which the said medium accumulates in thehollow tip ofthe hydro-brake vane and keeps it in the tilted-position, and a restoring positionin which-thesaidouter wall slopes inwardly at a moderate'angle-inwhich the said medium upon reduction of speed flowsxfrorn the' said hollow'tip" along said wall-to a'position inside of the said pivot; re storing the said hydro-brake vaneto its said normal working position.

2. A hydraulic turbine as'clairnedin claim 1, whereinthe'said inertia medium ismercury:

3. A hydr'aulic-turbineasclrimed'iir claim, 1, wherein the said inertia mediumconsists-ofismall ballsiofa'heavy metal.

4. A hydraulic turbine asf'claimedin claim" 1, wherein the" said hollow hydro-bral e vanes .are box-shaped and,

have aflange atone upstream .edge only for. the. asym.

metrical deflection ofthe water vortex .in'the saidbraking position.

5. A hydraulic,turbinetasclaimed. in .claim.-4,- wherein the upstream edge of. the saidrhollow-hydroebrakewane opposite the/said flange. isschamfereda 6. A hydraulic vertical shaft. turbine comprising-in:

combination: a runner, runner;vanes attached toithesaid runner, hollow segments-individually attachedlremovably to. the said runnen-and1 forming. a segment ring, a

pivot pin attached in each of the said segments, a hollow hydro-brakevane'pivoted on each X of the' said" pivot pins; and an easily movable inertia medium partly filling the said hollow hydro-brake vanes, each of the said vanes having an outside wall sloping inwardly at a very steep angle in a normal working position in which the said medium assumes a position below the pivot pin of the hydro-brake vanesrandkeeps the same retracted in the said. runner, an. overspeed condition. inwhichdhesaid medium risesalong thesaidst'eeply sloping. walls-above the said'pivot pin and tilts the said hydro-brake-Nane out of the said runner into the water vortex, a braking position in which' the said mediumaccumulates-in the hollow tip ofrthe hydro-brakevaneand keeps-itinthetilted. position, and a restoring position in which the said outer wall slopes inwardlyatamoderate-angle in which the said medium upon reduction of speed flows from the said hollow tip along said wall.to a position inside .of the said" pivot, restoring the said hydro-brake vane. to'its said normal workinggposition'.

7; Ahydraulic vertical shaft turbine comprising in com-- bination: a runner; runner"vanes'attachedto the said runner; hollow'hydrorbrakewanes, pivot pins articulat ingthe saidhydro-hrake'vanesto'the said runner arranged; tangentially to a pitch circle; and, an easily movable inertia medium: partly 'fillingithe said hollow brake vanes, 7 each" of the said"vanes*having aniouter wallrurming in the retractedposition' oftbersaid vane'outside the saidpit'ch circle with its'inn'er wall surface sloping; inwardly at'a'.

very steep, angle, and'a' pocket'at theilower end'ofsaid" outer'wall' containing; the said'inertia medium at'the rest and'low speedof'the. said runner, thesaidpoclc'et lying,

in the extendedpositioni of'tlie saidvanesrinsidethesaidi pitch circle and .inatlie retracted positionof the said. vanes:

outside the said pitch circle:

ReferencesiCitedin -.the; file. of. this: patent UNITED STATES? PATENTSs 771,771 Dysterud' .Oct: 4; 1904- 2382;108' Seewer -Aug, 14, 1945. 2,407',45 4 Seewer Sept. 10, 1946 FOREIGN PATENTS 629;7,76" Gireat Britain .Sp, t;-28 ,'.19.Z9

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