WO2020060387A1

WO2020060387A1 - Impulse hydro turbine system

Info

Publication number: WO2020060387A1
Application number: PCT/MY2019/000039
Authority: WO
Inventors: Abdul Bahari BIN OTHMAN; Mohd Haffis BIN UJIR
Original assignee: TNB Res Sdn Bhd; TNB Research Sdn Bhd
Current assignee: TNB Res Sdn Bhd; TNB Research Sdn Bhd
Priority date: 2018-09-19
Filing date: 2019-09-19
Publication date: 2020-03-26
Anticipated expiration: 2021-03-19

Abstract

In one aspect, the present invention discloses an impulse hydro turbine comprising: a rotatable turbine wheel mounted to a shaft comprising a rim to which a plurality of buckets being attached radially, the buckets being spaced apart from each other and distributed on said rim at a predetermined distance; at least one nozzle means spaced from the turbine wheel, the nozzle means having an opening for discharging jet stream of water towards the turbine wheel; wherein: the nozzle's opening is non-circular shape and producing a narrow jet stream thickness as it travels across the bucket to the opposite side. Further, the hydro turbine in accordance with the preferred embodiments of the present invention has smallest bucket area of contact for every kJ/s of the delivered kinetic power of the nozzle jet stream and the highest deflected jet stream angle relative to the bucket tangential velocity among the impulse hydro turbines; hence ultimately it will be able to improve turbine output and turbine efficiency of the impulse hydro turbines.

Description

IMPULSE HYDRO TURBINE SYSTEM

FIELD OF INVENTION

[0001] The present invention generally relates to a component of water turbines. And more particularly to a component of the impulse hydro turbine systems, to achieve operational efficiency

BACKGROUND

[0002] Among the various types of turbines, hydro-powered, more particularly impulse turbines use fast-moving fluid - commonly, water, to rotate the series buckets and generate energy. Generally described, for these type of turbines, the conversion of energy involves kinetic (by a fluid source) to mechanical (rotation of buckets), and subsequently converted to electrical energy with the aid of an electrical generator. One of the preferred types of impulse hydro turbines is the Pelton turbine, especially in high-head and relatively low discharge applications. A typical Pelton turbine comprises a rotatable wheel equipped with a plurality of blades, whereby the blades are usually in bucket/spoon-form, two spoons attach together, sharing the common splitter ridge at the centre of the attachment, adapted to catch the moving fluid from at least one nozzle and direct in at an angle during the process. Following this mechanism, the moving fluid in the form of fast moving jet stream thereby impinges upon the contoured buckets on top of the splitter ridge, before the jet is divided into two streams. One jet stream is directed to the other half the bucket and the other is directed toward the other half. Perceptibly, the directions of jet streams and velocities change or vary to follow the contours and surface of the buckets.

[0003] The buckets are designed such that the moving fluid (commonly, water), typically referred as jet-stream is deflected at an angle, and if possible without the exiting jet-stream interfering the oncoming jet-stream. The working concept of impulse turbines therefore relies heavily on the velocity of the jet-stream and the direction of the jet-stream entering and deflected out of the bucket, causing the rotation of the turbine shaft to create power, while variations on the contour, size and/or shape of the buckets may play a pivotal role in the power conversion efficiency. For conventional Pelton turbines, one of the primary challenges in maintaining turbine output is to reduce the jet-stream thickness (by means of reducing the nozzle’s diameter via plurality of nozzles) for a given nozzle velocity and discharge, which is dictated by the available hydraulic head at site and the maximum discharge suitable for nozzle water jet application. The nozzle jet stream thickness approximately equals to the design nozzle aperture diameter divide by two, i.e. the nozzle jet radius, which in turn limits the minimum Pelton turbine bucket span across one side of the bucket. Currently, this span which is essentially must be kept at least three times of the nozzle jet aperture radius. In practice this one side bucket span could be as high as 3.4 times for 5 and 6 nozzles Pelton turbine application. The minimum half bucket span is essential to enable the nozzle jet stream to retain smooth stream as it travels from the inlet at the centre splitter ridge, then being cut into two jet streams, before deflecting close to the opposite direction at the angle between about 155 and 170° relative to the bucket tangential velocity. If the width of the half bucket is inadequate the jet stream continuity will be broken at the bottom most of the bucket, i.e. half way toward the exit end since the jet stream does not have sufficient radius to make a smooth turn. If such scenario occurs, loss of turbine output will be significantly high due to the jet stream will be slowed down prematurely. Therefore, it has to be prevented even at the expense of the production cost for a Pelton turbine has to be much higher as opposed to accepting shorter half bucket span.

[0004] Another important aspect of the limitation of a Pelton turbine is it cannot take more than 6 nozzles per turbine wheel for a vertical shaft configuration to preserve minimum rotational angle 60° before the following nozzle starts to enter the same bucket. Otherwise collision of two jet streams from two successive duty nozzles will occur. Hence significant loss of turbine output will occur. [0005] Further limitation of conventional Pelton as described. An impulse hydro turbine that utilizes kinetic power injected by a water jet stream could not take relatively high discharge as oppose to better option for this condition, namely Francis turbine, another type of hydro turbine that is a reaction hydro turbine. For a site that requires high design flow per unit turbine, Pelton turbine utilizes multi nozzles arrangement. The design flow can be divided into 1 , 2, 3, 4, 5 and 6 nozzle jets per turbine wheel is suitable for a vertical shaft configuration only. If such divisive is inadequately small for the impulse turbine application, then the design discharge has to be divided into two units. This leads to tremendous increase in plant up cost since the civil structures have to be designed to meet two hydro turbine units instead of one. In most cases it losses out its competitive advantage to a Francis turbine or a Turgo turbine, which can take higher discharge per unit.

[0006] The limitation to 6 nozzle jet streams in the above is due to the observed fact that the in-bucket nozzle jet stream collusion will occur if the two consecutive nozzle jet streams are spaced less than 60° rotational angle. The critical sections of the two jet streams that are going to collide are the last remaining jet stream from the current duty nozzle that is about to exit the bucket and the incoming jet stream of the following duty nozzle that is just entering the bucket. These two jet streams pass at the same section of the bucket but almost opposite in direction. This scenario is called jet interference.

[0007] Therefore, it is apparent that maintaining an optimum impulse hydro turbine output or improving its operational efficiency has been a difficult task. It is further equally difficult to reduce impulse hydro turbine size to meet the desired site hydraulic condition, as well as adapting the current impulse turbine to have wider hydraulic condition and over maintaining its competitive advantage over its able competitors such as Francis turbine and Turgo impulse turbine.

SUMMARY OF INVENTION

[0008] In one aspect, the invention discloses a hydro turbine comprising: a turbine wheel rotatably mounted to a shaft comprising a rim to which a plurality of buckets being attached radially, the buckets being spaced apart from each other and distributed on said rim at a predetermined distance; single bucket type; a nozzle means having an opening for discharging jet stream of water towards the turbine buckets; at least one end being thinner than the other; and that the nozzle is adapted in a manner such that it thinner side serves as the jet stream thickness as the jet stream travels across the bucket.

[0009] In a preferred embodiment, the nozzle jet stream could be 1 to up 7 per turbine wheel; 2 wheels can be attached to a shaft for a vertical turbine shaft configuration wherein: the nozzle’s opening is non-circular shape. [0010] In the other aspect, the invention discloses the design of its non-circular nozzle aperture; ability to further reduce the jet stream thickness (film thickness in axial direction), where the Pelton turbine circular nozzle aperture area has reached practically the smallest possible; by further dividing it into two equal circular aperture areas; then the desired non-circular nozzle can be formed.

[0011] Preferably, the nozzle’s opening is adapted such that the nozzle produces or discharges a narrow water jet stream in axial direction.

[0012] Preferably, the nozzle’s opening is rectangular in shape.

[0013] Advantageously, the nozzle’s opening is elliptical in shape.

[0014] Preferably, each bucket comprises an elliptical shaped member with downward sloping walls connected to a base, and a splitter knife, located close vicinity to the topmost tip of the elliptical shaped bucket measured from the bucket Base Circle Diameter (BCD).

[0015] The nozzle jet stream geometry arrangement is its thickness, whereby the shorter side of the nozzle jet aperture while its width is the longer side of the nozzle jet aperture.

[0016] Preferably, the jet stream thickness is within the range of 0.2 to 0.4 times of its width for both elliptic and rectangular nozzle aperture.

[0017] Advantageously, the bucket width measured between the jet stream inlet side and exit side at the longest path, is less than 3.5 times of the nozzle jet stream thickness.

[0018] Preferably, the bucket width is, at most of a Pelton turbine half bucket axial

3

width for the same design pressure and the total turbine design discharge.

[0019] Advantageously, with the system of the present invention, the required jet stream thickness at most 2 of the Pelton half jet stream thickness, which ultimately

3

allows the hydro turbine of the present invention to have shorter bucket width for the same total nozzle pressure and total turbine discharge, whereby this can be achieved without compromising the minimum turning radius required for a smooth jet stream to turn while on its way exiting the bucket.

[0020] Preferably, a bucket height measured from topmost tip to the bucket BCD within the range of 1.20 to 2.5 times the nozzle jet width.

[0021] Advantageously, the nozzle aperture or opening and said bucket width, could developed 99.2 and 99.9% of the nozzle jet hydraulic energy to the bucket, for jet stream inlet offset angle 3° and jet deflected jet angle 170 to 177°, relative to the bucket tangential velocity respectively.

[0022] Advantageously, the bucket friction loss for the hydro turbine of the present invention is lowered to within the range of 0.9 to 2.9%, owing to its bucket has smaller wetted area than that of a conventional Pelton bucket for the same input pressure and turbine discharge, as opposed to Pelton bucket friction loss within 2 to 6%.

[0023] In another aspect of the present invention, an impulse turbine wheel assembly comprising: a turbine wheel rotatably mounted to a shaft comprising a rim to which a plurality of buckets being attached radially, the buckets being spaced apart equally from each other according to the design requirement and distributed evenly on said rim at a predetermined distance; whereby about 17 to 26 buckets around the wheel.

[0024] In a further aspect, the present invention discloses a method of mounting an impulse turbine wheel assembly comprising: attaching a plurality of buckets secured at a uniform distance about a wheel rim; providing at least one nozzle having a rectangular or an elliptical shape opening adjacent to the wheel rim in a manner such that a jet stream discharged through the nozzle hits at least one of the buckets thereby rotating the wheel rim;

BRIEF DESCRIPTION OF DRAWINGS

[0025] FIG.1A: Nozzle sizing for Pelton 1 ,2, 3, 4 and 5 nozzles and their equivalent sizing for innovation impulse hydro turbine nozzles.

[0026] FIG.1B: Nozzle sizing for Pelton for 6,7 and 8 nozzles and their equivalent sizing for innovation impulse hydro turbine [0027] FIG.2: An overview of the turbine wheel assembly in accordance with an embodiment of the present invention; [0028] FIG.3: A perspective and top views of a scoop of a bucket provided in accordance with an embodiment of the present invention;

[0029] FIG.4: Comparison between a single circular nozzle aperture/opening for a Pelton bucket and two elliptic nozzle/opening (FIG 4A) with respect to bucket sizes and nozzle aperture shapes and the same comparison for two rectangular nozzle apertures opening (FIG 4B);

[0030] FIG.5: A diagram illustrating an exemplary assembly of the turbine in accordance with an embodiment of the present invention;

[0031] FIG. 6: An illustration depicting the comparison for incoming and deflected jet stream between a Pelton bucket and the bucket in accordance with an embodiment of the present invention;

[0032] FIG. 7: A schematic diagram for the turbine in accordance with a preferred embodiment of the present invention installed in a system accommodating two turbines operating with water sources from two different intake elevations;

[0033] FIG. 8A-8C: An illustration of sliding friction force between a moving fluid and a stationary surface; a Pelton jet-bucket contact area and the jet-bucket contact area using the bucket of the present invention;

[0034] FIG.9: An exemplary assembly - particularly a set up for a vertical shaft impulse hydro turbine.

[0035] FIG.10: Alternative bucket embodiment to work in tandem with an elliptic or a rectangular nozzle aperture. DETAILED DESCRIPTION

[0036] The following description of the preferred and alternative embodiments is provided to understand the inventive features of the present invention. It shall be apparent to one skilled in the art, however that this invention may be practiced without such specific details. Some of the details may not be described at length so as not to obscure the invention. For ease of reference, common reference numerals will be used throughout the figures when referring to the same or similar features common to the figures.

[0037] The impulse hydro turbine in accordance with the embodiments of the present invention operates similarly to that of a Pelton turbine, with significant efficiency improvements and advantages over the conventional Pelton. Understandably, the water jet stream hits the buckets, generating force on the buckets, whereby the mechanical power output from the turbine is derived from the kinetic energy of the water jet stream.

[0038] In accordance to the embodiments of the present invention there is provided an assembly and system that is adapted and enabled as a hydro-based turbine; broadly defined, the assembly comprising significantly improved bucket hydraulic, geometry and nozzle means. The components of the turbine to be elucidated in accordance with an embodiment of the present invention are adapted such that it does not exclude the possibility of the assembly to be implemented on other types of hydro-powered turbines in particular the bucket design. It is anticipated that with the assembly of the present invention, the efficient operating range of the Pelton-alike turbines can be extended, and its bucket size can be made smaller than Pelton. [0039] The turbine described in accordance with the embodiments of the present invention may be interchangeably referred herein as“Bahari Impulse Hydro Turbine” or "BIHT”. The technical terms used throughout the description have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs, unless defined otherwise. The term “comprising” used in the context of the present invention generally refers to various components, elements or steps that can be additionally employed in practicing the present invention. [0040] In accordance with a first aspect, broadly defined, the present invention provides a hydro-powered turbine comprising: a turbine wheel (10) rotatably mounted to a shaft (10A) comprising a rim (12) to which a plurality of buckets (14) being attached radially, the buckets (14) being spaced apart from each other and distributed on said rim at a predetermined distance; at least one nozzle means (16) spaced from the turbine wheel, and whereby the nozzle means having an opening for discharging jet stream of water towards the turbine buckets.

Nozzle Dimension

[0041] FIG. 1A depicts the preferred nozzle dimension in accordance with a preferred embodiment of the present invention. With reference to FIG.1A, circular nozzle aperture shown therein can be taken as the smallest single nozzle jet aperture that a Pelton turbine can use as the basis of Pelton turbine bucket design with (1 ) diameter‘d’, or otherwise its start to lose turbine efficiency and hence its output (2) aperture area A (3) nozzle jet thickness t_p,, a BIHT elliptical nozzle aperture (also applicable for a rectangular aperture) in accordance with the present invention is formed smaller beyond by dividing the aperture into two equal area circular aperture nozzles, i.e. aperture area (4) 0.5A each and later (5) it formed an elliptical shape for each for the same area of 0.5A.

[0042] Then for each nozzle jet width, referred herein as (6) w_b is formed to have aperture thickness (7) t_b and hence a stream it produces will have to have thickness close to t_b too where t_b can be made less than 0.67t_p i.e. the width, w_b of the nozzle jet is adapted such that the aperture area remains at 0.5A. Using elliptical nozzle aperture thickness and width denote as t_b and w_b the corresponding BIHT buckets can be designed and constructed.

[0043] In another embodiment, preferably for a multi-nozzle Pelton that has (8) the nozzle aperture area, A for each nozzle: to end up with (9) 4 times 0.25A for a BIHT nozzles for number of initial nozzles are two (10a) 6 times 0.33A for a BIHT nozzles for number of initial nozzles are three (11a) 8 times 0.125A for a BIHT nozzles for number of initial nozzles are four. (12a) 10 times 0.125A for the BIHT nozzles for number of initial nozzles are five. For the total number of nozzles 8 nozzles to 14 nozzles for a BIHT, two wheels can be attached one above the other, to a single vertical shaft orientation BIHT, which the nozzles will be fairly distributed between the two wheels. [0044] In another embodiment for a 6-nozzle jet configuration in FIG.1B, preferably for (13a) aperture area A, ended up with (14a) 12 times 0.0833A, for the initial 7- nozzle configuration to end up with (15a) 14 times 0.0714A, for the initial 8-nozzle configuration to end up with (16a) 16 times 0.0625A. In the case of the number of nozzles is 16 per turbine shaft of a vertical shaft orientation BIHT, consideration will be given to divide the nozzles into two units of vertical shaft orientation BIHT, for number of the desired nozzles above 16 preferably they will be divided into two units of vertical shaft orientation BIHT.

[0045] Now referring to FIG. 2, the turbine wheel FIG.2 (10) and FIG.2A(10) which may be rotatable; coupled to a torque transfer shaft as shown in FIG. 2A (18), comprises between 17 to 26 buckets, in FIG.2 (14) and in FIG. 2A (20A), distributed on the periphery portion of the rim (12).

[0046] In accordance with a preferred embodiment, the bucket width across, W_b in FIG.3 (14F) is at most 3.5 times of the nozzle jet stream thickness, t_b in FIG. 3 (14H). In one example, each bucket’s width, W_b is within the range of 3 to 3.5t , while the bucket height FIG.3 (14G) from the outermost tip to the interfacing with the wheel is within the range of 1.25 to 2.5 times the nozzle jet width, w in FIG 3 (14J). The bucket comprises an elliptical shaped member, with downward sloping walls connected to a base, and a splitter knife (14E) at one end of the elliptical shaped member. A clearer drawing of the bucket is as shown in FIG. 3. [0047] A connecting extension (14C) is provided on one end of each bucket (14A), said extension (14C) comprising at least one opening (14D) - ideally, two openings sized accordingly to receive or insertion of a bolt or suitable fastening/locking elements for attachment of bucket and for securement of the bucket (14) to the peripheral portion of the rim (12). Understandably, when bucket (14A) is in contact at the central edge (14B), a gap (shown in FIG. 8B) is formed there between. The gap distance is preferably sufficient for engagement to the peripheral portion of the rim (12) and to avoid deflected jet back splashing and thereby secure each bucket (14) to the rim (12). [0048] In another preferred embodiment, for the case of two wheels per shaft assembly, the same approach can be adopted; the two wheels will be spaced as close as possible limiting by the required gap for insertion of the nozzles; while the jet streams are deflected in such a manner that the deflected jet streams will not to cause interference along the buckets rotational path; and a locking element i.e. bolt or screw is respectively inserted in the openings (14D), traverses the peripheral portion of the rim (12), thereby acting as central axis for the bucket (14). It is understood that in this position the two buckets are substantially aligned on the median axes/central edge (14B) of the bucket (14). Each bucket (14A) further includes a splitter knife portion (14E) to serve as a jet splitter to distribute the jet stream efficiently between two successive buckets, namely the duty and the approaching buckets during operation.

[0049] The nozzle means (16) as shown in FIG. 4 includes an opening (16A) accordingly adapted such that the nozzle produces or discharges high velocity jet, corresponding to pressure head of water source and delivering narrow stream of water. It is preferred that the nozzle’s opening comprises a rectangular or elliptical shaped member, whereby the preferred nozzle dimensions, thickness t_b , while nozzle width is 1.20 to 2.5 of its thickness, and the nozzle jet aperture area is made sufficiently large to pass the desired discharge of the hydro turbine.

[0050] With the nozzle means (16) in accordance with a preferred embodiment of the present invention, a thinner jet stream is produced owing to the lower aspect ratio of the nozzle aperture or opening. Perceptibly, this geometrical modification presents an additional advantage over the Pelton turbines due to the jet stream already made or adapted such that it produces a thinner stream as opposed to Pelton jet stream by the order 0.2-0.4 times thinner. The turbine of the present invention, as described in the preceding sections includes a thinner nozzle jet stream so that it can have shorter bucket width to fulfil minimum width of to be between 3- 3.5 times the nozzle jet stream thickness for the same discharge as per a Pelton’s half bucket or one spoon section of the bucket.

[0051] The efficiency of the turbine in accordance with the preferred embodiments of the present invention therefore can be significantly improved predominantly because of these three reasons; (i) relatively smaller wetted area for a BIHT bucket thus reduces contact friction power loss (ii) thinner nozzle jet stream enables the deflected jet angle can be made closer to the ideal 180° relative to the bucket tangential velocity, as opposed to Pelton jet deflected angle (iii) smaller buckets yields smaller weight to be supported by its supporting bearings, thus reducing bearing friction power loss. The improvement can be realized without a need to modify the conventional Pelton turbine or otherwise is expensive even if it is possible to do so. The differences between a single nozzle Pelton bucket and the bucket in accordance with a preferred embodiment of the present invention - with two elliptical or rectangular apertures or with thinner nozzle thickness, openings are more particularly apparent in FIG. 4A and FIG. 4B.

[0052] Still referring to FIG. 4A, comparison of two turbine buckets to serve the same pressure head and total hydro turbine discharge; the nozzle opening of the present invention, taking d as the smallest nozzle jet diameter for a Pelton turbine design for the given head and total discharge - a BIHT nozzle being elliptical-shaped has a thickness, t_b of about 0.20 to 0.4d, while the bucket width is about 0.6 to 1.2d, while for a rectangular shaped nozzle opening, thickness, t_b and width, w of the opening is similar to that of elliptical shaped version, but with a slight change in the half bucket width about 0.5 to 1.2d. The bucket height is about 1.25 to 2.5d as shown in the same figure.

[0053] When assembled, the wheel (10) is mounted to a turbine shaft, in particular to one end of the shaft of said turbine. The attachment or securement to the turbine or the process of making may be by conventional or standard means. In an exemplary assembly, as shown in FIG. 5, there are two nozzles arranged adjacent to the wheel (10) for a horizontal shaft configuration, at least one being positioned above the other at the selected angles to minimize deflected jet-bucket interference; similar to the current practices for putting two Pelton nozzles for a horizontal shaft configuration. Water will be channelled and discharged through the nozzles producing jet streams that spins or rotates the wheel of the turbine.

[0054] It is anticipated that the assembly of the present invention can be installed with the following variants (not shown):

• One or single nozzle disposed adjacent to the wheel;

• Horizontal or Vertical shaft configurations

• Two turbine wheels system coupled to a single shaft for vertical shaft configuration;

• Two or more wheels system coupled to a single shaft for horizontal shaft configuration. [0055] In another possible variation, the turbine of the present invention may include a side-entry -once- through -forward pass impulse hydro turbine buckets to replace the standard BIHT buckets as described above, whereby an exemplary is shown in FIG.10. For this variation, the buckets are either the simple half cylinders preferably for the twisted half cylinders, to account for increases in tangential velocity of the buckets as the point of a jet stream-bucket contact region has moved further away from the axis of rotation. The twisted half cylinder buckets are required to ensure incoming jet streams can be made to hit the buckets almost at the same time even though the blades tangential velocity increases as the regions of jet -bucket contact move further away radially from the axis of rotation. To facilitate efficient jet streams flow across the blades, the blades path will be made gradually shorter from the bases to their topmost tips. This is desired so as to ensure despite of local bucket tangential velocity increase, as the point of jet-bucket contact moving closer to the topmost bucket tip, bucket water jet stream retention period will be made to be the same at any distance of the bucket measured from the axis of rotation. By doing so, the formation of pressure gradient is kept to the minimum. Therefore, the formation of eddy-current is minimized too and hence reducing bucket power loss. The nozzle jet stream sizing, the wheel and shaft design configurations remain the same as the standard BIHT design approach.

[0056] It is understood that the components of the assembly and system in accordance with the present invention are operably interconnected to each other so as to achieve the purpose and primary objectives of the present invention. It is understood that the stationary parts and the turbine accommodating the wheel in accordance with an embodiment of the present invention; may include other components which are not part of this invention to make the invention operational such as but not limiting to the components as described herein.

[0057] It is further understood that the water supply for rotating the turbine wheel from higher elevation source than the nozzles centreline, is channelled to intakes, then through conduits or pipes (also commonly known as penstock) that carry water down to the hydro turbine, in which pressure head rises along the way down to the discharge opening due to gravity.

[0058] The following are experimental examples reflecting the operational aspects of a turbine accommodating the nozzle and bucket assembly in accordance with the embodiments of the present invention. It should be understood that these examples (in relation to both design and output results) serve as evidential support to the features of the embodiments of the present invention and should not be construed as limiting the scope of claims.

EXAMPLES

Design and Performance Comparison of Conventional Pelton and Turbine of the Present Invention

Number of Buckets

[0059] Generally, both conventional Pelton and the turbine of the present invention accommodate optimum number of buckets per wheel between 17 to 26 buckets. However, for a very small hydro turbine, the number of buckets may be reduced to a fewer number, for instance, less than 17 buckets.

Hydraulic power developed and Euler turbine efficiency (PETE)

[0060] With reference to FIG. 6 the Euler’s turbine equation for power developed by a bucket assuming the inlet jet enters at 0° relative to the bucket tangential velocity is:

P = pQ{\ - k cos b){n_{c -}u)ϋ (1)

The nozzle jet stream input kinetic energy after leaving the nozzle:

V ²

R = pQ (2)

And Euler’s turbine efficiency denotes as HETE, defined as the ratio between the power developed by water jet kinetic after crossing the bucket and kinetic power of jet stream after leaving the nozzle.

Where

P = Power developed by buckets (Watts)

R = Input kinetic energy (Watts)

Euler turbine efficiency of the jet stream within the bucket (Fraction) p = Water density (kg/m³)

Q = Nozzle discharge (m³/s)

b = Jet deflected angle (Degree)

, = Jet inlet velocity (m/s)

U - Bucket tangential velocity (m/s)

k = Bucket exit velocity factor (Fraction)

[0061] For the same pressure head, Vi, U, and p are practically the same for a Pelton and a BIHT hydro turbine. Whilst nozzle jet stream discharge for the turbine in accordance with the present invention shown in FIG. 4B is representing half of the Pelton turbine discharge to complement a single nozzle jet representation out of two the true number the actual number of nozzle jet streams to be used.

[0062] Ideally, Eq (3) has the maximum value of unity when, b is 180°, k factor is unity, indicating bucket friction power loss is ignored and U/Vi is 0.5 for the maximum power being transferred to the turbine shaft.

[0063] TABLE 2 below shows the estimated G)ETE for a Pelton turbine bucket within the normal designed deflected jet stream angles b the minimum angle 155° and the maximum angle 170° For the first case in TABLE 2, for b of 155°, the maximum h_Ete assuming k factor is unity is 0.9524 (95.24%). On the other hand, TABLE 3, for the designed b of 170°, assuming k factor of unity the maximum G|ETE is 0.9917 (99.17%). Theoretically HETE will not be affected by the design jet velocity for both cases. TABLE 4 and TABLE 5 show the same results for the equivalent BIHT bucket. For k factor taken as unity, the minimum b of 170°, h_Ete is 0.9924(99.24%), and for the maximum b of 177°, k factor taken as unity, G|ETE is 0.9993 (99.93%). Figure 5(a) and (b) show jet stream trajectory paths for Pelton bucket and BIHT bucket respectively to illustrate a BIHT bucket has higher b than a Pelton bucket. From these tables, they showed that h_Ete for a BIHT bucket are 3.5% and 0.69% higher than its equivalent Pelton turbine bucket for lower and higher b respectively.

TABLE 2

The maximum HETE for Pelton buckets for k=1 , b=155°, Vi=30m/s U=15m/s, and

Vi=100m/s and U=50m/s

Velocity Jet stream h_Ete Velocity Jet stream h_Ete type_ velocity _ type_ velocity (m/s) (Fraction) (m/s) (Fraction)

V 30 0.9532 Vi 100 0.9532

U 100 0.9532 U 50 0.9532

TABLE 3

The maximum h_Ete for Pelton buckets for k=1 , b=170°,, V_i=30m/s U= 15m/s, and

Vi=100m/s and U= 50m/s.

Velocity Jet stream Velocity Jet stream

PETE HETE

type velocity type velocity

(m/s) (Fraction) (m/s) (Fraction)

Vi 30 0.9924 Vi Ϊ00 0.9924

U 100 0.9924 U 50 0.9924

TABLE 4

The maximum h_Ete for BIHT for k=1 , b=170°, Vi=30m/s U=15m/s, and Vi=100m/s and U=50m/s

Velocity Jet stream h_Et_E Velocity Jet stream h_ETE type _ velocity _ type _ velocity _

(m/s) (Fraction) (m/s) (Fraction

_ L_

Vi 30 0.9924 V, 100 0.9924

U 100 0.9924 U 50 0.9924

TABLE 5

The maximum h_Ete for BIHT for k=1 , b=177°, Vi=30m/s U=15m/s, and Vi 100m/s and U=50m/s

Velocity Jet stream PETE Velocity Jet stream PETE type velocity type velocity

(m/s) (Fraction) (m/s) (Fraction

)

Vi 30 0.9993 V₁ 100 0.9993

U 100 0.9993 U 50 0.9993 [0064] FIG. 6 provides a clearer comparison for deflected angle b for Pelton turbine bucket and its equivalent BIHT in accordance with an embodiment of the present invention.

Exemplary Assembly - Two Turbine Wheels Sharing One Vertical Orientation Shaft

[0065] FIG. 7 shows a schematic diagram for the turbine in accordance with a preferred embodiment of the present invention installed in a system accommodating two BIHT turbine wheel taking the water from two different intake elevations. It is known for a Pelton wheel turbine to accommodate two wheels to a vertical shaft can be expensive, due to the requirements for many wheels and buckets and a need to dig its base further down to accommodate the second wheel, without compromising the available gross head. Alternatively adopting the much better the prior art solution, i.e. pumping from the lower elevation water intake to the higher elevation water intake and then channel the water to only one wheel will add up huge capital and operation expenditures. An additional building structure, pumps motors and step-down transformers are required to perform the task. On top of that pumping cost will add up to the operation expenditures. In contrast, a BIHT, the split buckets and split nozzles concept has natural ability to be designed to have the two turbine bucket wheels to share a common vertical orientation turbine shaft.

[0066] In this exemplary assembly to assess the operational capabilities of the turbine in accordance with the present invention, the optimal requirements to couple the two turbines within a single shaft are: (1 ) The two turbines have to rotate at the same angular speed (RPM) and (2) the bucket linear velocity (U) has to be theoretically 0.5 of its water jet velocity at nozzle exit (Vi), to maximize power transfer and hence to maximize turbine efficiency, denotes as q_tur. These two requirements can be achieved by controlling the diameters of the two turbine wheels at design stage. High pressure turbine should have bigger wheel diameter than the low-pressure turbine since it has higher V_\. For this arrangement as depicted in FIG.7, bottom turbine wheel belongs to low pressure turbine and the top turbine wheel belongs to high pressure turbine.

Bucket Friction Loss

[0067] FIG. 8A shows a moving fluid surface sliding over a stationary surface. The sliding friction force between the two surfaces can be expressed as the following:

Where

F Sliding friction force ( N)

C Prandtl number (Dimensionless)

P Fluid density (kg/m³)

K Fluid or jet stream velocity (m/s)

A Fluid contact area with bucket (m²)

[0068] Variable A is the multiplication of wL Taking the fluid flow is fully turbulent, C_f in turn can be expressed as the following:

0.027

^C/ = (5) Re }ⁿ

Re_x in Eq (5) is Reynolds number, defined along the x axis. The power loss due to sliding friction, denotes as P_Sf becomes:

[0069] From Eq (6) it can be seen for the same jet stream velocity, there are two parameters that dictating power loss due to bucket friction, namely Rex and wL. For a fully developed flow, i.e. high turbulent flow, where Rex has become very large, therefore its effect can be taken the same for both buckets. Therefore, determination of relative power loss for both buckets can be done based on the ratio for jet-bucket contact areas between both cases. The ratio is given by A_B/A_P in FIG. 8B-8C.

[0070] From FIG. 8B-8C, At/A_p ratio can be approximated as follows:

Where w and L are the width of jet stream and the length of jet stream travelling path respectively. Subscripts b and p are referring to BIHT and Pelton respectively. From FIG. 8B-8C:

Wt>= 1.2d, L_b= 0.6d, Wp=0.5d , L_p=1.5c/

1.2 x 0.6

- 0.48

1.5 [0071] Re-written Eq (6) in term of bucket friction power loss ratio, yields: 0.48

=> /> = 0.48^ (8)

[0072] Eq (8) concludes that bucket friction power loss for the bucket provided in accordance with a preferred embodiment of the present invention is 0.48 of the power loss experienced by Pelton bucket for the same pressure head and jet stream discharge. It should however be noted that in practice, the true value could be higher than 0.48 of the Pelton power loss, considering R_x for the two cases will not be similar and taking the true ratio of A_b/A_p could be higher than 0.48.

[0073] In practice Pelton bucket friction power loss ranging from 2 to 6%. Based on Eq (8) the turbine of the present invention should able to reduce approximately within the range to between 0.96 and 2.88%.

Gross Head Utilization

[0074] The gross head denotes as H_g for an impulse hydro turbine is defined as static head between intake water level elevation and nozzle centreline. For a horizontal shaft with more than one nozzle, average centreline can be taken as the referenced centreline. FIG. 9 shows H_g set up for a vertical shaft impulse hydro turbine.

[0075] Assuming the objective to maximize H_g for a Pelton turbine can be achieved by setting its nozzle centreline elevation at NCE in FIG.9, where NCE is nozzle average centreline elevation. At this elevation, the margin AH_m shall be sufficient to meet the plant maximum discharge, Q_max, while downstream water level elevation is at the maximum design flood elevation, denotes as DFE. DFE aka the design maximum probable plant discharge (inclusive downstream flood contribution) usually is used to define the discharge side the design probable maximum water level elevation could rise. The rise of downstream water level elevation under this scenario shall be kept just below the bottommost of the turbine buckets. FIG. 9 shows the hypothetical NCE for Pelton turbine marked by dashed line in the middle of right-hand corner.

[0076] In this exemplary assembly, the bucket of the present invention has shorter bucket width of 0.6 d as opposed to 1.5cf for Pelton equivalent. Therefore, for every NCE for Pelton turbine, NCE for the turbine of the present invention can be lowered further by 0.9d. It is shown that with the assembly of the present invention, the H_g increases significantly comparing to its equivalent Pelton turbine.

[0077] For a Pelton nozzle diameter 0.20m, the turbine assembled in accordance with the present invention provides additional gross head, denotes as AH_g by 0.18m. This advantage comes without any associated cost. Percentage improvement of H_g above the Pelton turbine, for the same nozzle diameter, d depends upon its design gross head. For the design H_g of 100, 200 and 300m, their percentage improvements are 0.18, 0.09 and 0.06% respectively.

[0078] The described advantage in relation to the gross head for the present turbine in the previous section over its equivalent Pelton turbine above applies for a vertical shaft configuration only.

[0079] It is anticipated that the advantages of the turbine in accordance with the embodiments of the present invention lies generally in the features of the bucket and nozzle opening/aperture which results to the producing jet stream to be consistent and increases bucket efficiency (refer: experimental examples). The use of nozzles (elliptical or rectangular) of the present invention is therefore totally advantageous relative to the hydro-power, more particularly, impulse turbines of the prior art.

[0080] It is understood that the operational control of the turbine system in accordance with embodiments of the present invention, i.e. velocity, speed, other parameters may be implemented using conventional/standard electronic components. Similarly, the signal exchange, voltage regulation and signals (if required) are implemented using electronic components or modules.

[0081] It is also further understood that the turbine described in accordance with embodiments of the present invention will work along with the existing hydro power turbine systems.

[0082] As would be apparent to a person having ordinary skilled in the art, the afore- described methods and components may be provided in many variations, modifications or alternatives to existing devices and systems. The principles and concepts disclosed herein may also be implemented in various manner which may not have been specifically described herein but which are to be understood as encompassed within the scope and letter of the following claims.

Claims

1. A hydro turbine comprising:

- a turbine wheel rotatably mounted to a shaft comprising a rim to which a plurality of buckets being attached radially, the buckets being spaced apart from each other and distributed on said rim at a predetermined distance; at least one nozzle means spaced from the turbine wheel, the nozzle means having an opening for discharging jet stream of water towards the turbine wheel, and at least one end thinner than the other; wherein:

the nozzle is adapted in a manner such that it thinner side serves as the jet stream thickness as the jet stream travels across the bucket.

2. The hydro turbine as claimed in Claim 1 , wherein the turbine utilizes a plurality of elliptic or rectangular nozzle aperture.

3. The hydro turbine as claimed in Claim 1 , wherein the nozzle’s opening is adapted such that the nozzle produces or discharges a narrow stream of water jet.

4. The hydro turbine as claimed in Claim 1 , wherein the nozzle’s opening is rectangular.

5. The hydro turbine as claimed in Claim 1 , wherein the nozzle’s opening is oval or elliptical in shape.

6. The hydro turbine as claimed in Claim 1 , wherein each bucket comprises an elliptical shaped member with downward sloping walls connected to a base, and a splitter knife portion on at least one end of the bucket.

7. The hydro turbine as claimed in Claim 1 , wherein the nozzle jet stream thickness is 0.2 to 0.5 times of its width.

8. The hydro turbine as claimed in Claim 1 , wherein the nozzle jet stream width is 1.2 to 2.5 times of its thickness.

9. The hydro turbine as claimed in Claim 1 , can be either elliptical or rectangular nozzle aperture.

10. The hydro turbine as claimed in Claim 1 , wherein the bucket width is within the range of 3 to 3.5 times the nozzle jet stream thickness, and the bucket height is within the range of 1.2 to 2.5 times the nozzle jet stream width.

11. The hydro turbine as claimed in Claim 1 , wherein it can have the jet stream deflected angle within 165 to 177° measured from the bucket tangential velocity.

12. An impulse turbine wheel assembly comprising:

- a turbine wheel rotatably mounted to a shaft comprising a rim to which a plurality of buckets being attached radially, the buckets being spaced apart from each other and distributed on said rim at a predetermined distance;

- at least one nozzle means spaced from the turbine wheel, the nozzle means having an opening for discharging jet stream of water towards the turbine wheel;

wherein:

the nozzle producing relatively shorter jet stream travelling path across the bucket.

13. A method of mounting an impulse turbine wheel assembly comprising: attaching a plurality of buckets secured at a uniform distance about a wheel rim;

- providing at least one nozzle having a non-circular shape opening adjacent to the wheel rim in a manner such that a jet stream discharged through the nozzle hits at least one of the buckets thereby rotating the wheel rim.

14. A method of mounting an impulse turbine wheel assembly comprising:

- mounting a plurality of the twisted or non-twisted half cylindrical buckets; secured its root on a wheel base; attaching a plurality of buckets at a uniform distance about a wheel rim; providing at least one nozzle having a non-circular shape opening adjacent to the wheel rim in a manner such that a jet stream discharged through the nozzle hits at least one of the buckets thereby rotating the wheel rim; wherein:

one side of each cylinder bucket arranged such that the nozzle jet stream hits at offset angle less than 15° measured from the bucket tangential velocity; while the nozzle width is aligned to enter the half cylinder inlet edge;

- the jet stream is deflected at the other end of the half cylinder bucket at the deflection angle within 170 to 177°, align accurately to avoid back splashing of the approaching bucket.