GB2486297A - Pelton turbines with funnel shaped separator - Google Patents

Abstract

A near sonic nozzle Pelton turbine, especially for hydro-electric power generation, has a horizontal turbine rotor located above a funnel shaped plenum 5 causing saturated vapour and water droplets from the turbine rotor to be centrifugally separated so that the water is discharged from the bottom of the casing and the vapour exits through the turbine rotor shaft which is hollow. Optionally there are radial turbines 9, 18 located to extract energy from and to reduce the rotation of the discharging water and vapour steams. Also described (figure 2) is a water discharge for use in hydroelectric dams which has a curved lower lip to cause the discharged water to flow down the dam s outer face.

Description

NEW', HYDRO-ELECTRIC NEAR-SONIC NOZZLE' PELTON TYPE TURBINES with SECONDARY RADIAL TURBINES.

This invention relates to H-E (hydro-electric) turbines that extract more power from water from high dams than conventional near-sonic nozzle' Pelton type turbines (originally a Pratt & Whitney technological break-through') do. Such turbines, by definition, being applicable to dams of such height that tur- bine inlet static head pressure water gauge exceeds the near-sonic' velocity pressure in their nozzles (including high H-E dammed waterfalls -patent application filed). In particular, it relates to generating spirally energised water and vapour (which can be condensed) from the vapour and spray emanating from the rotors of such Pelton type turbines such that recovery of spiral and discharge kinetic energy is enabled, and water vapourand spray evaporation losses are virtually eliminated.

16 H-E turbines without near near-sonic nozzles conventionally discharge water horizontally from a dam's face such that upon such abrupt exit 100% of it's significant kinetic energy is lost, and such that, post discharge, there is break-up of the discharged water causing evaporation loss. Such would be the case with this invention in which spray (and optionally vapour) becomes an homogenous water discharge, excepting where it is significantly velocity reduced prior to being non-abruptly dis-charged -with minimal energy loss. (Such velocity reduction regains static pressure such that, in effect, the dam's power generating static head pressure is increased equal to the re-duced kinetic energy loss -not applicable to conduits from turbines having separate vapour and water content).

Extracting more H-E power per unit of mass flow reduces dam de-pletion for given power generation such that with dams, such as the Hoover Dam, suffering reduced water levels their original water level can be restored without reducing current power gen-erating capacity. Once dam water level is fully restored, power generating capacity would then exceed the original system's.

The jets of water sprayed from the near-sonic nozzles of such Pratt & Whitney' turbines impact upon the rotating Pelton ro-tor blades, losing velocity and breaking-up into a cascade of droplets and micro droplets of water in suspension (ie satura-ted vapour). Friction efficiency losses in the flow of water to, and through, the nozzles and upon the Pelton bucket' rotor blades are manifested as heat input and, as such, mostly evapo-rates water from droplets (such evaporation being approximately equal to such heat input, divided by the water's latent heat of evaporation -less an efficiency factor) to generate vapour.

Vapour bubbles are also propagated by the transition edges in the near-sonic nozzles' -which also propagate turbulence in the nozzle jet spray which, together with the bubbles, promotes break-up of the jet spray, resulting in vapour being shed from from such spray; both of which issues are addressed in this new' system, as is the issue of vapour cavitation in the flow arrangement to the nozzles.

In this invention water droplets in the mix of broken-tip nozzle jet spray and vapour emanating from the rotor blades of a hori- zontal near-sonic nozzle' Pelton type turbine are separated-out by an open-ended inverted funnel shaped extension of the inner rotor chamber. Such funnel shaped plenum vortexes the ro-tating fluid liquid/vapour mix emanating from the rotor such that the water droplets in it centrifuge-out and agglomerate into a spirally rotating stream of water discharging from it's open end -with displaced rotating vapour being vented via, a so provided, hollow rotor shaft. (Such centrifugal separation being motivated by high rpm rotation of the Pelton rotor blades and the semi-tangentially angled jets of water sprayed from the nozzles.) In this way spray carryover to atmosphere and evapo- ration thereof is obviated -which, otherwise, can only be re- duced by pressure and power dropping eliminator plates -con-serving water for possible downstream useful use. Also, in this way separated-out water vapour can be refrigeration condensed and sub-cooled to generate a water supply that can be used to cool air and/or the H-E system electrical equipment and, in any case, be discharged separately, or together with the separated- out water, into the dam's downstream river course, or into con-duit to flow (without evaporation) by gravity for remote useful use and/or to increase the turbine's power generation by means of the engendered syphon suction effect addition to the dam's static head pressure. Particularly where there may be 100's of feet of elevation difference down to such a conduit's exit, use of one (I), or more secondary terminal/intermediate turbines may be required -or similarly, such conduit could flow water downstream directly from the dammed waters, eq of a low rise dam, to a remote turbine (that may be a near-sonic nozzle' Pelton type), or turbines.

in such a centrifugal separation system rotor rotation direc-tion should, ideally, be in the same direction as the natural whirlpool, or plug hole', drain rotation that occurs in the earth's hemisphere in which the system is located.

To facilitate separated-out vapour venting requires that the turbine rotor has an adequately sized hollow shaft, or a co-axial pipe in it, that extends through the H-E generator rotor and terminates at it's casing with a ball bearing that would interface with the (non-rotating) vapour vent flow pipework -affixed to the generator casing. In this way, cool vapour would then be cooling the the generator interior, reducing winding resistances, which increases electrical efficiency. Most sim-ply, and efficiently, the vapour vent pipe would be common with the generator rotor core -and have a bell-mouthed entry.

Discharging the spirally rotating water from the funnel open end into a radial outlet volute dr-rotates such flow prior to atmospheric discharge such that post discharge spiral ciisper-sion evaporation is obviated, conserving water for downstream useful use. Such a volute also efficiently changes water dis-charge flow direction and, in doing so, converts the entering water's spiral energy into outgoing static pressure such that static pressure at the funnel's open end is lowered, in effect drawing water out of it -such pressure being further reduced where the volute has a larger outlet than inlet and/or diver-ging transition1 such as a highly efficient SPR Foil (Patent no:G82381835) type1 at it's outlet. Where there may be one (1), or more SPA (static pressure regain) transitions that, for ex- ample, result in a doubling of discharge outlet size, the dis- charge velocity would reduce by 75% and velocity pressure po- tential energy loss by 93.75% (less negligible efficiency loss-es with volute and SPA Foil transitions).

Flow from the funnel's open end should be controlled to ensure minimisat ion of carryover of vapour bubbles, eg manually via a downstream regulating valve (with constant flow systems), or automatically by a motorised valve, or by a variable speed sec-ondary turbine (see later) such that water is backed-up into the separator funnel -commissioning being via a viewport near the bottom of the funnel, with automatic control being via a pressure sensor in the funnel (optimum power generation corre-sponding to incipient vapour bubble carryover). Separated-out vapour vent discharge should be be similarly parallel control-led via self-learning computer software. Other possible control means include water level sensing and laser sensing of vapour bubbles in the separated-out water.

Alternatively, a secondary speed variable radial flow turbine (or any flow de-rotating turbine) directly connected to the funnel open end can, not only fulfil the functions of providing for waterflow de-rotation and direction change, but also derive power output from the static pressure regain engendered by such spiral energy de-rotation (patent application filed).

Similarly, rotating separated-out saturated vapour vented from the hollow turbine rotor shaft can be used to power a secondary adiabatic expansion cooling turbine-generator. Although vapour mass flow would be much less than the water's, a vapour expan-sion turbine outputs much more power per unit of mass flow per unit of pressure difference than a liquid turbine. Such an adiabatic expansion cooling turbine could be a reversed low pressure DIDW (double-inlet-double-width), or medium pressure 919W (single-inlet-single-width) centrifugal fan (thereby with a reverse rotating impeller' and motor' that acts as a qener-ator) of which there are many such fans commercially available (requiring re-rating to suit high density vapour rather than standard air'), or, turbocharger type compressors for higher pressure differentials. Such turbine can also be used to con- trol sub-cooling of the refrigeration cooled separated-out yap-our condenser where so provided by means of varying it's speed.

NB 1 Ideally, secondary turbines should have larger outlets than inlets such that power generating SPA is efficiently re-gained, or have SPA divergences fitted to their outlets.

NEt 2 In practice, some water, particularly from the funnel open end, condenser or secondary turbines, may contain small amounts of vapour bubbles, which would be so highly saturated such that such water can, effectively, be considered to be wholly liquid.

Reducing the velocity of water upstream of, and/or at, an exit discharge outlet, having a so curved/SPA Foil shaped lower lip that it facilitates, by Coanda effect, water to flow over it down a dam's vertical, or sloping face, would so reduce dis-charge kinetic energy loss that it would be negligible -and it would also reduce exit discharge waterfall' sound power level to attest to the efficacy of such discharge. NB I The top sur-face lip of the conduit at such an outlet would require to have shallow downward SPR Foil type curve to obviate unstablising cavitation breakaways. NB 2 Conduit sides at such an outlet can also be laterally SPR Foil or shallow angle diverged, or steep-er if diverging splitters are also used. NB 3 In any case, CFD (computational fluid dynamics) should be used to verify/design such outlets and to quantify SPR. In addition to energy saving, such discharge outlets would reduce post disharge evaporation to a negligible level, further conserving water that may be usefully used downstream. NB If waterflow was rotating (ie not de-rotated) such a diverging outlet would require to be circu-lar, not rectangular, to enable SPR and reduction of exit loss.

Downstream secondary turbines may be any type of turbine, in-cluding near-sonic nozzle' Pelton types. However, reversible radial turbines are classically simple, and benefit from volute inlet flow pre--rotation, or discharge de-rotation (according to flow direction). Radial turbines are, in effect, reversed, or excess flowed direct or belt-drive centrifugal pumps -of which a wide range are available (though requiring re-rating for vo-volute pre-, or de-rotation, as may be determined by CED.

conventionally, water discharging H-E turbines discharge water from a dam face with significant velocity (and kinetic energy) such that it gushes out horizontally, The kinetic energy of such being proportional to it's velocity pressure, or the squa-re of it's velocity (it has no gauge static pressure since the discharge outlet is open-ended to atmosphere). Therefore, redu-cing discharge velocity reduces kinetic energy loss, and such velocity would reduce where a turbine has a larger outlet than inlet, and more so where there are subsequent divergant tran- sitions. Ideally, velocity should be so reduced at the dam out-let that where it' has a curved lower lip it would flow over the lip, by Coaflda effect, without separation -and where such lip terminates tangentially with the dam's face it would flow down it such that the power of gravity draws water out of the outlet such that power generation would be higher than when otherwise discharged -such effect applying, to a lesser extent,, when exit flow discharge is less than horizontal (or negatively if such disharge were angled upwards).

Velocity reduction static pressure regain is equivalent to in-creasing the dam's height to increase power generation such that, for example, if discharge velocity pressure was reduced from 50 psig (36.6 m wg) to, say, 5.0 psig (3.66 m wg), this would be equivalent to adding, after deducting SPR transition efficiency losses, about 30 metres (100 ft) to dam height.

To understand the SPR effect on water discharging from an H-E turbine via open-ended conduit consider that, a) static press-ure at a turbine's outlet (without an outlet SPR transition) equals friction pressure drop down the discharge conduit - -s -which with likely short conduit would be low -but, b) SPR with a turbine outlet SPR Foil transition doubling conduit cross-sectional area would be 75% (less a negligible loss with such a transition) of it's outlet velocity pressure -with conduit friction pressure drop then 25% of what it otherwise would be -such that there would now likely be a negative/suction pressure at the turbine's outlet -in effect drawing water out of it.

NB Water, or even a fluid water droplet/vapour mix, could be discharged below the downstream river's surface, but would re- quire to be discharged horizontally at the same velocity as ri- ver current (ie via a river-size outlet) to obviate power re-ducing back pressure (water being more viscous than air).

Applying SPR to the flow of water from existing water dischar- ging H-E turbines would increase flow and static pressure diff-erence across the turbine such that power output increases. If such improvement would exceed turbine-generator optimum, or maximum operating limits, this can be addressed via the use of secondary H-E turbines to absorb such SPR such that flow would be unchanged. Where increasing existing turbine discharge con-duit size may be problematic, it may be feasible to open-up the dam discharge outlet sufficiently to generate significant SPR.

It is known that water flowing from a dam via conduit to the near-sonic nozzles' of such Pelton type turbines contains vap-our bubbles by the time it reaches them, and that they are propogated by abrupt, or poorly flowing, conduit size and flow direction changes. Such cavitation being due to the water's mo-mentum causing continuous, or momentary break-aways from the conduit's surface. Conventionally1 Pratt & Whitney near-sonic nozzles' have inlet perforated plates to break-up such vapour bubbles and turbulate water to mix-in the vapour, such that li-quid flow is not sufficiently interrupted by a vapour bubble that it causes a backpressure shockwave in the nozzle throat from the following inrush of water. However, junctures causing cavitation generate high static pressure loss, and perforated plates also generate a static pressure loss, which, together reduce H-E system efficiency and power output. Such flow ineff-iciencies can, not only be eliminated, but nozzle flow can also be positively boosted. Conventionally, water flows from the dam into an annular collector ring via multiple peripheral abrupt exit inlets, and then into the abrupt entry orifices of the no- zzle inlet plates. However, the collector ring can be substitu- ted with a snakl-like volute that smoothly rotates flow direct-ly into the (angled) inlets of the nozzles, and intakes water via conduit directly from a dam face bell-mouthed entry in such a way that there are no junctures upstream of the nozzles that might possibly cause vapour bubbLe cavitations. Therefore, there would be no need to have nozzle inlet perforated plates (that break-up vapour bubbles) -freeing-up the design of the inlets such that, instead of being semi-abrupt and straight si-ded, their entry leading edges could be elongated and their trailing edges have ram' scoops (extending above the volute's inner surface boundary layer, and designed by means of CFD -allowing for upstream scoops. With, a) elimination of abrupt junctures that cause pressure loss, b) elimination of nozzle perforated plate pressure drop, c) a volute that generates vel-ocity pressure at nozzle inlets and d) improved design inlets to nozzle throats, the static pressure upstream of nozzle thro-ats would increase such that the nozzles could flow a greater S volume of water and/or nozzle throat size could be reduced (in-creasing pressure drop), such that water jet velocity and power output of the Pelton type rotor would increase.

In lieu of an inlet volute there could be separately piped connections to the peripheral, semi-tangentially angled, nozz-le inlets of the Pelton rotor chamber. Such multiple flow pipes should draw water from the dam in such a way that cavitation generating velocities/junctures are obviated, eg via header/s having bell-mouthed dam inlets and with acutely angled pipework take-offs or refrigeration type distributors, or directly via bell-mouthed take-offs from a dam face diaphragm plate, and be continuous braided hose or soft copper pipe. This enables tur-bine flow/power to be varied by sequentially operating electric valves in the multiple flow pipes (obviating cavitation that would occur with modulating valve/s and reduced nozzle inlet pressures at reduced flows), such that as rotor rpm slows the velocity difference between rotor blades and the jet sprays of active nozzles would increases, increasing power generation per unit of mass flow, such that dam depletion rate would be less than conventionally at reduced power generating outputs -con- serving water for peak demand periods such that a higher capa-city increased draw-off system might be used.

Nozzles with separate flow connections can, similarly, also have their flows stopped in such a way that their spray jets onto the Pelton rotor's blades are interrupted short of blade tip edges s*ch that edge interference losses would be reduced and, as such, would be particularly advantageous with elongated nozzles (see later). Also, the duration of such nozzle flows can be varied, to vary turbine flow in such a way that mid-du-ration flow occurs during maximum perpendicularity of nozzle flow to the rotor blades such that, not only would nozzle jet-to-blade velocity be higher the lower turbine flow was, but also the higher average perpendicularity is the higher the force exerted, and power generation, would be per rotor blade per unit of reduced mass flow -particularly where there are other parallel turbines whose flows are similarly parallel re-duced, and where standby' units are actively used (reducing average duty loading per unit).

Conventional Pratt & Whitney' nozzles have a straight sided divergance after their throats, and such divergance generates SPR equal to the difference between the, considerable, throat and nozzle outlet velocity pressures -less a transition effi-ciency loss. Such transition loss would be significantly lower with an SPR Foil shaped divergance such that nozzle flow effi- ciency and power generation per unit of mass flow would in-crease, reducing dam depletion for given power generation. Or, for given throat velocity, increase rotor chamber static press-are -increasing the power output of secondary turbines.

Conventional Pratt & Whitney nozzles also have a circular th-roat and discharge spray. However, linear or elongated nozzles (eq flat oval), angled and curved to match the pitch and pro-jected camber of the turbine's rotor blade tips, would spray 100% of their spray volume for a Longer duration upon the ro-tor's blades than the spray from circular one's such that power generation per blade per unit of mass flow would be higher than conventionally. Blade edge interference losses would also redu-ce for the converse such reason. Also, more than one (1) such nozzle could be grouped line abreast such that that they can be sequentially controlled in such a way that blade edge losses would be less. Having such nozzles with jet spray spanning bla-de tip chord width makes it advantageous to have blades that are other than straight along their span, and, in particular are SPR Foil forward curved at their tips (both front and back -meeting *in a finite edge) such that, a) a spanwise Bayram bucket' effect is generated -in addition to the chordwise Pelton one -and, b) nozzle jet sprays, by Coanda effect, wrap-around the tips to generate lift to generate more power per blade per unit of mass flow than conventionally.

Pratt & Whitney' Pelton type turbines use rotors that operate with circular, continuous flow, nozzles -not with pulsed flow from elongated nozzles and, as such, new' rotors should be de-signed for such purpose by means of CFD. In any case, Gurney type flaps (as used on racing car wings) can be added to rotor blades to increase the Pelton bucket' effect.

In addition to the foregoing descriptions of variations of the invention, a specific example will now be described by way of reference to the two (2) accompanying drawings in which: Figure 1 shows a near-sonic nozzle' Pelton type H-E turbine with a pre-rotaing peripheral radial inlet volute, a centri-fugal separator and de-rotating water and vapour turbines.

Figure 2 shows the de-rotated water flow from the Figure 1 sys- tem non-abruptly discharging at a H-E dams' face via a diver-ging SPR Foil curved lower lip down the dam's face.

In Figure 1: waterflow I enters from a dam via volute 2 to ann-ular nozzle block 3, from which high velocity jets of water are sprayed onto the Pelton bucket' type blades of rotor 4 such that it rotates and discharges a spirally rotating mass of wa- ter droplets and water vapour into funnel 5. Funnel 5 concen-trates said water droplets such that they agglomerate into a rotating mass of water in funnel S's neck, and such that less dense water vapour £ is displaced upwards and vented out of funnel S via bell-mouthed outlet 7. The rotating water B dis-charged from funnel 5 is de-rotated by radial flow turbine 9 such that it generates a power output derived from the static pressure difference between that in funnel S and discharge con-duit 10 (increased by turbine 9's de-rotating static pressure regain effect). Bell-mouthed outlet 7 is an extension of the rotating shaft 11 of hydro-electric power generator 12, onto which magnetic rotor 13 and nozzle jet powered Pelton type ro-tor 4 is mounted, and which runs in permanently lubricated ball-bearings 14 and 15. Conduit 16 is flange connected to gen- erator 1115 casing, containing electric stator 17. Rotating wa- ter vapour 6 is de-rotated by adiabatic expansion cooling ra- dial flow turbine 18 such that it generates a power output de-rived from the static pressure difference between that in funn S el 5 and conduit 19 (that is increased by radial turbine 18's de-rotating static pressure regain effect). The speed of radial Flow turbines 9 and 18 is parallel controlled via self-learning computer software from pressure sensor 20 such that waterflow is backed-up into funnel 5 when turbine 9 is slowed down and/or turbine 17 is sped up, or vice versa -being commissioned with the aid of viewport 20.

In Figure 2: separated-out water flow conduit 10 (as per con-duit 10 in the Figure 1 system) connects to circular-to-square transformation section 21 such that it is efficiently diverged to wider cross-section 22 via splitters 23 and 24, incorporated in conduit section 25. Conduit section 26, having an SPA Foil curved lower lip, turns water flow such that, with the aid of much reduced velocity and Coanda effect, it flows down the dam's outer face 27. In this example the exit discharge velo-city at dam face 27 is approximately 14% of that in conduit IC) such that, power generating, static pressure regain of such ve- locity (pressure) reduction would be 98% (velocity pressure be-ing a function of the square of the velocity) of the velocity pressure in conduit 10 (less transition efficiency losses) - which would otherwise be 100% lost at a conventional abrupt ex-it outlet. Also, shear friction forces in the gravitationally pulled flow of water out of the discharge conduit down the dam face generate a negative static pressure in the flow of water in the mouth of conduit section 26 -further increasing power generation per unit of river sass flow into the dam (+ or -any precipitation/evaporation and seepage). Top lip 28 is downward curved to obviate possible oscillating water cavitation break-away from the top surface of the discharge conduit: the design of any such outlets should, in any case, be by means of ad-vanced CFD.

Claims (6)

1. CLAIMS; 1) A near-sonic nozzle' Pelton type turbine comprising of a conventional horizontal such turbine, unconvenventionally having an open-ended hollow rotor shaft, and an open-ended inverted funnel shaped plenum into which the rotating mix of saturated vapour and water droplets eàanating from it's ro-tor are discharged and centrifugally separated such that separate, spirally rotating, water and vapour streams are discharged from said open ends for possible useful use, and such that there is no spray discharge and evaporation there-of to conserve water for possible downstream useful use.
2. 2) A Pelton type turbine according to claim 1, in which dis- charged water is de-rotated by a volute to obviate centri-fugal spiral dispersion evaporation of the discharged water.
3. 3) A Pelton type turbine according to claims I or 2, in which a valve regulates the presence of vapour bubbles in discharged waterflow to minimise discharge foaming evaporation.
4. 4) A Pelton type turbine according to claim 1, in which a ra-dial turbine fulfills claims 2 and 3's functions such that it derives power from such functions.
5. 5) A Pelton type turbine according to any of the preceding claims, in which a radial turbine derives power from the vented vapours spiral energy and funnel static pressure.
6. 6) A Pelton type turbine according to any of the preceding claims, in which vented vapour is refrigeration condensed and sub-cooled to generate a chilled water supply and/or conserve water for useful useS 7) A Pelton type turbine according to claims S and 6, in which the turbine's speed is controlled to control condenser sub-cooling such that it derives power from such function.8) A Pelton type turbine according to any of the preceding claims, or a conventional near-sonic nozzle' such turbine, in which the flow arrangement to the nozzles obviates cavi- tation and the pressure drop of their otherwise required in-let perforated plates, increasing power generation per unit of mass flow.9) A Pelton type turbine according to any of the preceding claims, and any parallel such unit, in which flow is varied by sequentially interrupting nozzle flows such that nozzle jet-to-rotor blade velocity difference of the active nozzles increases the lower total flow is, increasing power genera-tion per unit of sum total mass flow. so10) P'elton type turbines according to claim 9, in which active nozzle flows are interrupted in such a way that rotor blade edge losses would be less than those of nozzles that contin-uously flow when active such that power output per unit of -It) -sum total mass flow would be higher than in claim 9's case.11) Pelton type turbines according to claim 10, and alternative to claim 9's means of varying flow, in-which such variation S is occurred by varying duration of nozzle flows upon rotor blades in such a way that blade edge losses would be lower the lower mass flow is such that power generation per unit of sum total mass flow would be higher than in claim 10.12) Pelton type turbines according to any of the preceding claims, in which nozzle entries and/or exits are so shaped such that, per unit of mass flow, their pressure drop would be less than the straight-sided one's of the conventional near-sonic nozzle' type's, increasing power generation per unit of mass flow.13) Pelton type turbines according to any of the preceding claims, in which nozzles are elongated in such a way that dwell time of 100% of nozzle spray flow upon rotor blades would be of longer duration than a conventional circular nozzles', increasing power output per unit of mass flow.14) Pelton type turbines according to any of the preceding claims, in which rotor blades are forward curved in such a way that power output per blade per unit of mass flow would be higher than with conventional straight span blades.15) Pelton type turbines according to any of the preceding claims, in which rotor blades have Gurney' type flaps to increase Pelton blade bucket' effect such that power output per blade per unit of mass flow increases.16) Water discharging turbines according to any of the pre-ceding claims, and others, in which their water discharge exits via an outlet lower than their inlet such that power generation per unit of mass flow increases.17) Water discharging turbines according claim 16, in which there are one (1), or more, secondary turbines to obviate otherwise excessively required turbine pressure drop/s.18) Water discharging turbines according to any of the pre-ceding claims, in which conduit outlet discharge is less than horizontal such that exit flow is gravity accelerated.19) Water discharging turbines according to any of the pre-ceding claims, in which discharge water is flowed down the dam's face in such a way that exit flow gravity acceleration is maximised and there is no discharge break-up evaporation.