US1803220A - Water turbine - Google Patents

Description

T. THOMPSON WATER TURBINE April 28, 1931.

9, 1929 2 Sheets-Sheet 1 Filed Nov.

FIG. I.

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Ap 1931- I l THOMPSON 1,803,220

WATER TURBINE Filed Nov. 9, 1929 2 SheetsSheet 2 R 41:1 9 h d 777% 3 V c a f lrnreniar TllafllllsWOmfason Patented Apr. 28, 1931 THOMAS "THOMPSON, or Lennon, ENGLANb WATER TURBINE Application file'd Novem er 9, 1929; ser al No.

This invention relates to water turbines for either high or low pressure water falls and concerns especially machines of'thfekind wherein the water forming the driving mediam enters a stator at or near one endof the turbine and acts upon a rotor whilst travelling through the turbine in a direction substantially parallel to the axis of rotation of the machine leaving finally by way of a 10 draught or exhaust tfube.

The present invention has for its object to provide an improved construction of such turbines adapted to utilize the head of water available to the fullest possible advantage and with this object in view the invention consists in utilizing stream lin'ed means as hereinafter described, for'the purpose of directing the water in such a manner that its propulsive effect is concentrated more especially upon those portions of the rotor blades of greatest diameter, i. e.- the outer portions of the blades or those parts furthest from the turbine shaft. p

In carrying the invention into practical effect, there is provided centrally of the inlet end of the turbine a-boss containing a bearing for the rotor shaft and having a hollow waisted substantially part-toroidal external surface which co-acts with a correspondingly shaped internal surface of the casing in diverting the water from its initial inward direction of flow to a downward direction of flow diverging slightly from the axis of the turbine. The bladed rotor is disposed adjacent said boss and the water after passing between the surface of the boss and the opposed part of the casing impinges upon the outer parts of said blades, where the turning moment is greatest.

The invention will be better understood by referring to t-helaccompanying drawing. in which Figure 1 is a longitudinal section of a turbine constructed in accordance with my invention. Figure 2 is alike View to Figure 1 but showing a slight modificationin the draft tube. r

Referring to these drawings it will beseen thatthe casing or stator of the turbine shown comprises upper and lower sections a and b, the lower section constituting a-draft tube,

406,028, and in Great Britain July 24, 1929.

the twosections being adapted to be bolted together, the upper section a being formed wih radial Water inlets c gated by adjustable vanes d and said upper section having a cap e closing its top end.

Disposed beneath the cap and centrally within the upper part of the casing is a dependingcentral fixed hub f which contains a bearing 9 for the rotor shaft h and is shaped eXtern-allyso that its profile. has a substantially part-toroidal form, this concavely curvedprofile being coincident at its upper end with the upperwall of thewater inlet 0 vandatits lower end extendingin a direction ly divergent from the axis of the turbine.

The rotor z' of the turbine which in this instance is of the propeller blade type is disposed immediately. below the hub f and its blades j project in a downwardly and outwardly sloping direction across the annular water. channel of the turbine at about the point-of juncture of the upper and lower sections a and bof the casing where the diameter is somewhat enlarged.

As'may be seen the water before impinging upon these blades is first subjected to the guiding influence;,of the vconcavely curved outersurface of'the hub f and the complementarily curved opposite wall of the casing whichtogether direct the water axially and outward towards the outer parts of the blades j where it will operatejwith greater leverage upon theshaft h. v j

i The lower part I) of the casing mayconverge towards the axis and diverge again gradually as shown inFigure 1, or its walls maybe cylindrical as indicated in Figure 2. The hub of the rotor 71 may conveniently be 'of theshape of an inverted coneand a Moody spreader or other form of diffuser maybe provided beneath the rotor on the longitudinal axis of the turbine as indicated at in. It will be noticed from Figure 1 that the lower end of the inner surface of the outer wall of the section a curves downward and outward and then straight downward. The same is true of the construction shown in Figure 2. In Figure 1 the draft tube 5 extends centrally 1n ward and axially while in Figure 2, the draft tube is cylindrical. In both cases, the roots of the blades are disposed. coincident with the lower end of the outer surface of the hub so that the water is discharged away from the roots of the blades j and outward toward the extremities of the blades 9'. In my invention no outer bands are used engaged with the extremities of the blades, but the flow is guided entirely by the curve in the stator or outer casing wall only. In order to obtain the full value of the weight and head of water, it is necessary for the blades to extend at a downward and outward angle to the axis in order to secure the full impingement of the flowing water against the surfaces at their most effective point.' This is secured. only by the use of the downwardly divergent blades. i

Above and below the horizontal center line of the machine, that is, the dotted'line extending between the upper andlower sections of the casing in Figure 1, the stator has a return curve, that is, the stator has its inner surface extending downwardly and centrally. This produces an equal area of flow through the usual cavitation space, below the body of the propeller, and this reduces the-volumetric capacity of that space and thus reduces cavitation effects previous to the expansion of the lower end of the stator to reduce the velocity.

It is reiterated that in this turbine, the fiow of water is guided not into the narrowest spaces between the blades at the roots thereof, but is guided away from the roots of the blades toward the outer ends of the-blades so that the whole weight and force of the stronger stream lines of the flow are directed against the outer portions of the blades. It results'from this that there is no congestion of the flow at the center of the rotor. Where there is congestion of the flow at the center of the rotor, a surge of turbulent water is set up which resists the passage of the flow through'the blades andfforms a curtain of resistant water at and around the roots of the blades just above the same and tends to create a vacuum in the space immediately beneath the rotor and blades, thus increasing the tendency to cavitation below the rotor body. Under these circumstances, the only flow which does reach the outer ends of the blades is that flow which is repelled outwardly by the rebutting action of the turbulent barrier of surging water, churning immediately 'around the inner ends of the blades where they join the recess body. Cavitation, as is well-known, is the greatest enemy of efficiency in propeller turbine design and the churning of the water at the roots of the blades tends to liberate any dissolved gases and so intensifies the cavitation effect below the rotor body. In my construction, the setting of the blades at a downward angle, allows the flow to follow the lines of least resistance through the blades in the direction of the blades and on to the outer ends of the blades with, therefore, a minimum-result in cavitation efiect, this desirable result being further assisted by the return curve in the lower portion of the stator or casing which reduces the volumetric capacity of the usual cavitation space and at the same time maintains an equal area of flow through the region of that space before the flow of water is allowed to again expand to reduce its velocity.

It will be noted that in my construction,

there is no outer ring or runner for the blades,

nor are there any guides or like devices employed above the blades which would set up friction and resistance to the water.

The turbine may be arranged with its axis vertical, inclined or horizontal according to requirements, and the water inlets may be radial or tangential if a whirling motion is required or in some cases may be of volute form. The rotor which may have blades adustable and/or reversible as to pitch is preferably constructed without anyexternal ring or muff. Any desired form of propeller or rotor may however be employed.

I claim 1. In a hydraulic turbine, an outer casing having inlets at its upper end, a centrally disposed fixed hub carried by the outer casing, a rotor shaft extending through the hub carrying a rotor disposed beneath the hub the rotor having a central hub and downi wardly and outwardly extending blades, the outer surface of the fixed hub and the inner surface of the casing defining an annular passage withinwhich the blades operate, which passage extends inward, downward and outwardi V 2. In a hydraulic turbine, an outer casing having inlet-s at its upper end, a centrally disposed fixed hub carried by the outer casing, a rotor shaft extending through the hub carrying a rotor disposed beneath the hub, the rotor having a central hub and downwardly and outwardly extending blades, the outer surface of the fixed and rotatable hub and the inner surface of the casing defining an annular passage within which the blades operate, which passage extends inward, downward and outward, and then inward to a point below the end of the rotatable hub.

3. In a hydraulic turbine, an outer casing having inlets at its upper end, a centrally disposed fixed hub carried by the casing, a rotorshaft extending through the hub and carrying a rotor disposed beneath the hub, said rotor having downwardly and oution Lin

point below the lower end of the tapering portion of the rotatable hub.

4. In a hydraulic turbine, an outer casing, a centrally disposed element and a bladed rotor disposed beyond the centrally disposed element, said casing and element 7 being formed to produce water guiding surfaces having profiles sloping away from the axis of the rotor, and discharging the water toward the outer ends of the blades, the outer ends of the rotor blades being unconnected and extending outward and downward.

5. In a hydraulic turbine, an outer casing, a centrally disposed element and a bladed rotor disposed beyond the centrally disposed element, said casing and element being formed to produce water guiding surfaces having profiles sloping away from the axis of the rotor, and discharging the Water toward the outer ends of the blades, the outer ends of the rotor blades being unconnected and extending outward and downward, the lower portion of the rotor casing being extended inward and downward, the lower end a: of the body of the rotor being tapering downward and axially.

6. In a hydraulic turbine, an outer casing having inlets for the water and an inner surface having a curvature adapted to direct the water. downwardly and outwardly, a fixed central hub carried by the outer casing and likewise having a curvature adapted to direct the water downwardly and outwardly, a shaft extendingthrough the central hub, and

a. rotor of the screw propeller type disposed beneath said hub and having blades arranged to receive the full force of the water on. the outer portions where the turning moment is most effective.

In testimony whereof he has afiixed his signature.

THOMAS THOMPSON.

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