GB2413828A

GB2413828A - Control of fluid driven turbines.

Info

Publication number: GB2413828A
Application number: GB0410058A
Authority: GB
Inventors: Evans Rupert John Armstrong
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-05-06
Filing date: 2004-05-06
Publication date: 2005-11-09
Also published as: GB0410058D0

Abstract

A turbine is driven by a jet of fluid from a nozzle 3 impinging on blades 4 of a rotor 5, the nozzle 3 can be axial separated from the blades 4 so that the amount of fluid hitting the blades 4 can be varied and thus the rate at which the turbine is driven can be altered.

Description

241 3828

Description

Title: Control of fluid driven turbines

FIELD OF THE TNVF,NTION

The present invention relates generally to the control of the working fluid (typically water) within a fluid turbine for the purpose of regulating the power output and to prevent over- pressure of the supply pipe or over-speed of the turbine in the event of 'load rejection'.

BACKGROUND TO THE INVENTION

Water turbines of the reaction and impulse type have been known since the early part of the 19 century. Adjustable vanes and gates are frequently employed to regulate the flow through such turbines but few have systems are able to control the flow of liquid to the working runner vanes without altering the flow rate. This invention relates to an inlet nozzle assembly that can be displaced axially relative to the turbine runner so that the issuing flow can bypass the runner without doing work on the runner and also without changing the flow rate through the turbine.

KNOWN ART

Engineers including Benoit Fourneyron and Girard designed turbines with inlet nozzles that could be adjusted so as to control the flow of water to the turbine runner. In a known version of a Fourneyron turbine the position of the runner could be altered for the purpose of adjusting the point that the jet impinged upon the runner vanes but not adjusted so that the flow bypassed the runner.

A known turbine by I,ewis Ferry Moody GB 214423 (fig 7) has a separate deflector ring interposed between the nozzle and the runner for the purpose of diverting the flow when the power was not required, the disclosed invention has no separate deflector.

The Pelton turbine which is used on high heads, operates in a similar fashion to the disclosed invention but employs a separate deflector or in some early designs, a pivoted nozzle that allows a discrete jet to be swung out of line with the runner.

Recent patents JP8200197 and EP 0676544 show variations on earlier designs but without the capability for the jet to bypass the runner without interrupting the inlet flow.

The disclosed invention relates specifically to an axially movable nozzle assembly and a turbine runner that allows the inlet flow to be directed at the runner or progressively displaced until it bypasses the runner altogether. This transition is achieved without blocking or interfering with the flow because the supporting ring at the open end of the runner, is in the form of a sharp edge which parts the flow into 'working flow' and 'bypassed flow'.

OBJECT OF AND ADVANTAGES OF THIS INVENTION

i) It is a very simple design because it does not require a separate deflector element and the runner and shaft are fixed axially.

ii) The axially movable nozzle can be combined with a variable orifice to achieve both flow control (power control) and speed control. These functions can be operated independently. The flow can be set according to the water availability or demand, while the 'deflector' capability can be used to regulate the speed of the turbine without altering the flow setting.

iii) The turbine is easy to manufacture than known designs with separate deflector elements, such as the Moody turbine. All the main components are concentric and parallel making machining relatively easy.

iv) The transition between running and bypassing can be achieved rapidly and without causing pipeline surges. This is important if the load on the turbine is rejected and there is no other 'load governing system'.

SUMMARY OF THE INVF,NTION

The present invention comprises an axially movable inlet nozzle in a fluid turbine that allows the issuing fluid jet to impinge on the working runner blades or to bypass the runner, partly or completely, so that work is not done on the runner. Modifications are envisaged to the turbine runner blade supporting ring that include a taper, chamfer or curved portion to the non-drive end ring of the runner. This feature would reduce the disturbance to the jet flow during the transition from working runner vane to bypassing the runner.

It is envisaged that either the runner or jet assembly may be moved relative to the body of the turbine as it is the relative positions of the jet and runner that determine the work done by the jet on the runner. The nozzle opening which may be adjustable by varying the effective width, determines the flow rate and hence the power available to the runner. The axial position of the runner relative to the jet determines the proportion of that power that is converted into shaft power and dissipated into the turbine outlet casing.

Several different flow paths for the fluid issuing from the nozzles are envisaged, inward-flow, outward-flow and axial-flow.

Inward-flow paths are most suitable for low head open flume sites Fig (8) with the axially adjustable nozzle submerged within the intake flume and the runner discharging downwards into a draft tube. Axial displacement of the nozzle directs the flow under the runner and into the draft tube. Adjustable nozzles which change the aperture axially or radially to change the flow rate are envisaged. A foot-step bearing to support the bottom of the turbine shaft is envisaged in combination with the nozzle system.

Outward-flow layouts could be used on low head sites Fig (1). On high head sites the pressurized inlet section is strong and easy to manufacture when compared to a spiral cased design.

An axial-flow version is envisaged Figs (5 6) where the nozzle forms an angled jet or swirling cone of water such that any axial displacement of the runner or nozzle assembly would cause the flow to miss the runner all together.

The nozzle system typically comprises an outer body to which guide vanes are attached, and which is machined accurately so that it can slide within a similarly machined portion of the inlet pipe. A second component comprises an end plate or casting which prevents the water from bearing directly on the turbine runner and forms the lower edge of the radial jet. This plate would typically be fixed to a sleeve or shaft so that it can be moved together with the outer sleeve or relative to it, from outside the turbine casing. The plate as described, would have slots of the same profile as the guide vanes, so that they can pass through it as the nozzle is closed up to reduce the cross-section and jet size. When moved together the jet maintains the same cross-sectional area. When the assembly is moved axially the jet bypasses the runner partly or completely and produces less or no power at all. An alternative arrangement that is envisaged has the vanes attached to a movable end plate and the inlet ends of the vanes sliding within the nozzle body.

Pressure compensation is envisaged to resist the hydrostatic pressure acting on the end-plate of the sliding nozzle. This could be achieved with a spring or equalising piston. The position of the piston and hence the nozzle assembly can be altered by adjusting the differential pressure across the compensating piston.

A vertical layout is possible using the components already described or by introducing the water from the same side as the runner supporting shaft. In such an arrangement the bearing nearest to the runner will have to be sealed against the ingress of water or be of a water lubricated type. The nozzle controls would have to be in the form of concentric sleeves outside the shaft or a combination of sleeve and control links outside the water inlet tube.

Another vertical shaft embodiment would have the water entering from under the runner in a known fashion but with the nozzle controlled via a rod within a hollow main shaft and or linkages within the water inlet passages.

A further vertical embodiment is envisaged where there is an open flume and the turbine is attached to the floor of the flume and the sleeves and linkages controlling the nozzle are brought above the water and are operated by means of a yoke and bunions on the wall of the sleeves.

An inward flow version with a circular or volute pressure casing is envisaged.

It is envisaged that there may be situations where the setting of the turbine will require an airtight casing with an outlet tube continuing below the tail-water so as to draw a vacuum to increase the effective head. It is also envisaged that there may be situations where the setting of the turbine will require an airtight casing which is situated below the tail-water level and air under pressure is introduced so at to prevent the runner from being drowned.

The materials envisaged for the disclosed invention include cast and fabricated elements in a range of materials from cast ferrous and nonferrous metals and plastics.

It is envisaged that most of the turbines described will be of the impulse type, with the runner passages being partly filled with water. It is also envisaged that the passages may be completely filled for all or part of their length and that under certain circumstances the turbine may be operating partly or completely as a reaction turbine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiment of this invention comprises an outward flow impulse turbine runner attached to one end of a shaft that is supported in anti-friction bearings so that it can rotate. Said runner is designed with an eye that accommodates a nozzle assembly which discharges water radially onto the runner vanes. The endplate of the runner that surrounds the nozzle is machined to a sharp edge to part the flow cleanly and without shock when the nozzle assembly is withdrawn from the runner. The nozzle assembly slides within a ring that is attached to the base of the inlet flume. a/

DESCRIPTION OF DRAWINGS

Fig 1 Shows the detailed internal layout of the preferred embodiment of a vertical shaft open flume turbine with an outward flow arrangement.

It has a fixed aperture nozzle assembly (1) that is axially movable in the foundation ring (2) so as to alter the alignment of the water jet that is being forced out tangentially through the nozzle passages (3) and into the runner vanes (4).

The turbine runner (5) is fixed to shaft (6), which rotates in bearing (7) which is in turn supported by the nozzle assembly and located by the foundation ring in the base of the inlet flume (8).

A control tube (9) is attached to the nozzle assembly for the purpose of raising or lowering it in relation to the runner. In position 9(a) the nozzle is raised fully so that the issuing flow (10) bypasses the runner completely. In position (9b) the issuing flow (11) is directed onto the turbine runner (4) to make it rotate.

A chamfer (12) is provided on the top edge ofthe end-ring (13) of the runner, so as to reduce the 'shock' and splash as the nozzle assembly moves from the running to the bypass positions.

Fig 2 Shows a turbine as illustrated in Fig 1 but with the addition of a flow controlling capability.

The guide vanes (5) may be attached to and move with the nozzle base plate (4) and slide relative to support spider (10) and nozzle top ring (7) so as to reduce the height of the flow issuing from the nozzle.

The guide vanes may alternatively be attached to the nozzle top ring (7) and pass through close fitting slots in the nozzle base plate (4) The base of the nozzle (4) is attached to and moves with control tube (12) The nozzle top ring and supporting spider (10) are attached to and move with control tube (1 1) so that the complete nozzle assembly and issuing flow may be moved out of line with the runner, without altering the flow, by keeping the relative positions of the top ring and base plate of the nozzle constant.

The nozzle assembly slides in foundation ring (9) that is secured to the base of the inlet flume (8) Fig 3 Shows a horizontal shaft cased version of a turbine fated with the control valve.

The water enters through an elbow pipe fitting (1) with the control tubers) passing out through the wall of the bend at (2).

The water passes through movable nozzle assembly (3) and onto the runner (4) and then into the case (5) A draft tube (6) is shown taking the water away from the case.

The turbine shaft (8) rotates in bearings (7) Fig 4 Shows an elbow layout of outward-flow turbine with the water entering the 'eye' of an outward-flow turbine from above.

The water enters from the penstock (1) through the nozzle assembly (2) and into the runner (3) and out into the tail-race (5) The control tubes are shown around the main shaft at (4) Fig 5 Shows a single jet axial-flow turbine where the vertical movement 'd' of the nozzle moves the jet from the running position (1) to the bypass position (2) so that it bypasses the turbine runner (3). The outer support-ring of the runner is brought to a sharp edge (4) to reduce the splash and shock during the transition from running to bypassing. 5/

Fig 6 Shows an axial flow turbine with a full admission jet that is conical. Moving the nozzle assembly (2) upwards 'd' will cause the cone of water (3) issuing from the nozzle to pass outside the runner (5). The outer runner support ring is brought to a sharp edge (4) to reduce splash during transition from running to bypass.

Fig 7 Shows an inverted siphon layout with the water entering the 'eye' of an outward-flow turbine from below. The inlet is via the penstock (1) which feeds the movable nozzle assembly (2) from below. The flow issuing from the nozzle (3) is bypassing the runner (4).

This particular arrangement shows the control rod (5) and control tube (6) passing up through the hollow main shaft (7). The tail-water level is shown at (8) Fig 8 Shows the internal layout of an inward-flow vertical shaft turbine installed in an open flume. The head-water (1) acts to force the water through the inlet nozzle passages (2) onto the runner blades (3) which are carried on shaft (4). The shaft turns in steady bearing (5) or on a footstep bearing (Sa). The bypass flow is controlled by raising or lowering the nozzle assembly that has a sliding skirt (6) that locates within the draft tube (7) that is attached to the bottom of the flume (8). The foot ring of the runner is curved (9) to direct the bypass water into the draft tube. Adjustment of the nozzle opening is achieved with rods (10) that draw the inlet vanes up through the top cap, which in turn is supported on the movable control tube (12). The water discharges to the tail-water level (13). \

Claims

D Cuts

Having now particularly described and ascertained the nature of our said invention and in what mane" the same is to be performed, we declare that what we claim is: 1. A fluid driven turbine comprising a non-rotating inlet nozzle part and a bladed rotating runner part, the two of which can be moved apart axially by mechanical or hydraulic means so that the fluid flowing from the nozzle part can partly or totally bypass the runner part causing more or less energy to be transferred to the runner part.
2. A fluid driven turbine as described in claim I in which the runner part is fixed axially relative to the casing and foundations of the plant and where the nozzle part can move axially relative to the runner part.
3. A fluid driven turbine as described in claim 1 in which the nozzle part is fixed axially relative to the casing and foundations of the plant and the runner part can move axially relative to the nozzle part.
4. A fluid driven turbine as described in claim 1 in which the nozzle part can be adjusted to vary the fluid flow towards the turbine runner blades.
S. A fluid driven turbine as described in claim 1 in which the flow passes inwards through the nozzle part towards the runner part.
6. A fluid driven turbine as described in claim 1 in which the flow passes outwards through the nozzle part towards the runner part.
7. A fluid driven turbine as described in claim I in which the flow passes axially through the nozzle part towards the runner part.
8. A fluid driven turbine as described in claiTn I in which modifications are made to the turbine runner part in the form of a chamfered, tapered or curved inlet edge that allows the fluid jet from the nozzle part to be move out of line with the runner part without causing significant back pressure in the inlet flow.
9. A fluid driven turbine as described in claim I in which the sliding nozzle assembly is attached to a compensating piston or spring element in order to partly or totally balance the forces resulting from the inlet fluid pressure.
10. A fluid driven turbine as described in claim I in which the nozzle assembly is attached to a compensating piston which is also used to move the nozzle axially by applying unequal pressures to each side of the piston.
11. A fluid driven turbine as described in claim I in which the nozzle has vanes that impart a swirl to the issuing jet relative to the turbine runner vanes.
12. A fluid driven turbine as described in claim 1 in which the inlet part is in the form of a volute which imparts a swirl to the issuing flow.
13. A fluid driven turbine as described in claim I in which the guide vanes of the nozzle project through slots in the movable end plate of the nozzle when the nozzle is adjusted.
14. A fluid driven turbine as described in claim I in which the guide vanes in the nozzle assembly are attached to the movable Ed plate and slide within the main body of the nozzle.
IS. A fluid driven turbine as described in claim I in which the nozzle opening is adjusted with a cylindrical gate with a sharp edge.
16. A fluid driven turbine as described in claim I in which the fluid flow is adjusted by bringing the two sides of the nozzle together.
17. A fluid driven turbine as described in claim I in which the output shaft is vertical.
18. A fluid driven turbine of the radial flow type as described in claim 1 in which the output shaR is horizontal.
19. A fluid driven turbine as described in claim I in which the output shaft is hollow.
20. A fluid driven turbine as described in claim 1 in which the nozzle canponents are castings.
21. A fluid driven turbine as described in claim I in which the nozzle components are fabrications.
22. A fluid driven turbine as described in claim 1 in which the casing is airtight and Vacuum is generated in the outlet tube to increase the power.
23. A fluid driven turbine as described in claim I in which the inlet passages Are in the form of a pressurized casing. ^
24. A fluid driven turbine as described in claim I in which the runner space is pressurized with air so that it can be operated below the level of the outlet stream.
25. A fluid driven turbine as substantially described herein with reference to FIG.1 of the accompanying Drawings