|Title of Invention||
"AN IMPROVED PELTON RUNNER BUCKET DEVICE"
|Abstract||This invention relates to an improved pelton runner bucket device for converting hydraulic energy of water to rotational mechanical energy of a hydroturbine, the device comprising a plurality of buckets, each bucket having atleast two sculptured bowl-like bucket faces (4) adjoined by a splitter (2), each of the bucket faces (4) being configured indentically defining a surface along which the input jet water flows after blfurcation at the splitter (2), the bucket faces (4) each having a flank (t) defined by its lateral end the flank (i) constitutes of an inner segment (1 A) and a tip segment (IB). The tip segment (IB) is configured to locate at a lower elevation than the inner segment (lA), thereby increasing the bucket width (B) without increasing the bucket diameter (D) which allows accommodating additional buckets in the device to achieve hydraulic performance. [Fig. 1]|
|Full Text||FIELD OF THE INVENTION
This invention relates to an improved Pelton runner buoket divece used in high performance Pelton Turbine system.
BACKGROUND OF THE INVENTION
Pelton runners are impulse type of hydro turbine prime movers particularly suited for operation in the water head range of 400m and beyond. A Pelton turbine system consists of the prime mover - which is the runner assembly, nozzles, which in turn are supplied water at a particular pressure & rate By a distributor pipe and a casing which encloses the runner & nozzles. Each nozzle directs a jet of water at the runner. The water jet interacts with the rurmer and imparts its kinetic energy to the runner. The runner is thus the most important part of the whole turbine system responsible for converting the hydraulic energy of water to rotational mechanical energy of the turbine, which in turn drives an electric generator to produce electrical energy. A typical runner consists of 15 to 25 buckets held axi-symmetrically around the turbine axis.
Pelton runner bucket is shaped like two symmetric semi paraboloidal-like sculptured bowls joined together at the plane of symmetry, which is typically a sloping elevated ridge called splitter. The flanks on either side are planar of almost uniform thickness. The tip zone (away from axis) is tnmcated by a relief somewhat shaped like a 'W with rounded edges, called cutout while the inner zone (near to axis) is filleted to a solid disc.
A jet of water strikes this bucket symmetrically at the splitter edge, gets split into two and glances along the two bowl like portions to flow out along the flanks.
Many (typically 15 to 25) such identical buckets made of suitable metal are firmly fixed, either integrally or releasably, depending on the assembly, to be located axi-symmetrically all around the central axis of rotation and the whole assembly rotates due to action of the water jet on bucket.
The Pelton runner is the prime mover and rotates on account energy transfer due to impact of the jet with the ruimer bucket as well as change of momentum as the water flows along the curved bucket surface. A jet of water is issued from a nozzle fed by a pipeline called distributor. Typically there are one, two, three, four, five or six jets impacting the ruimer axisymmetrically from six nozzles all of which are fed water in equal quantity by the distributor pipeline.
The head and discharge available at the power plant site dictate the hydrodynamic phenomena governing the selection of geometric proportions of a Pelton rurmer bucket. While higher discharge calls for larger nozzle diameter & bucket width, higher head in turn will require a higher pitch circle diameter of the turbine runner. Thus the selection of Pelton runner diameter & bucket width is governed by the site hydraulic parameters.
While higher diameter to width ratio and higher number of buckets can increase the hydrodynamic performance & the efficiency of energy conversion, there is a limit upto, which these parameters can be raised because of the problems associated with increase in size, such constraints being the higher cost and the problem of rebound water jet interference with the rear side of adjacent bucket.
The water jet after impacting the runner has to change direction through an angle as near 1800 as possible, with respect to the incoming jet, in order to maximize momentum exchange. But this can lead to interference of the rebounding (out-flowing) jet with the backside of adjacent bucket.
Thus there is a limit on the increase in efficiency that can be achieved by increasing the diameter to width ratio or by increasing the number of buckets.
Thus, an object of the invention is to propose an improved Pelton runner bucket assembly, which overcomes the jet interfetence problem.
Another object of the invention is to propose an improved Pelton runner bucket assembly, which can be provided with an increased number of buckets for a given diameter to width ratio.
Yet another object of the invention is to propose an improved Pelton runner bucket assembly, which achieves higher hydrodynamic performance.
A further object of the invention is to propose an improved Pelton runner bucket assembly, which has two levels in the flank face of the bucket.
Still a further object of the invention is to propose an improved Pelton runner bucket assembly in which the bucket width (B) of each Pelton runner bucket is increased without increasing the bucket diameter (D) and without any drop in efficiency.
Yet a further object of the invention is to propose an improved Pelton runner bucket assembly, which increases the turbine efficiency, thereby achieving higher-output (MW) for a power plant without any increase in size and cost of the power plant.
The nature of the invention, its objective, and further advantages residing in the same will be apparent from the following description.
An improved Pelton runner bucket assembly for converting the hydraulic energy of water to rotational mechanical energy of a hydro turbine, comprising a plurality of Pelton runner buckets, each bucket comprises of two sculptured bowl like bucket faces each being an exact mirror image of the other, disposed on either side of a splitter, the splitter representing a shape of an elevated inclined ridge, the bucket face defining a surface along which the water flows after bifurcation of jet of water at the splitter, the lateral end of each bucket face defined as flank comprises two longitudinal ends, an inner-end integrating rigidly with a segment of a solid disk and a tip-end being truncated by a notch
to define a cutout, the position of the Pelton bucket relative to its rotational axis represents the pitch circle diameter, the maximum distance between two opposite flanks defines the bucket width, in that each flank comprises two segments, the portion starting from the inner end and extending up to the position of maximum bucket width is defined as an inner segment, the remaining portion being represented as a tip segment, and in that the tip segment of the flank is configured to locate at a lower elevation than that of the inner segment of the flank thereby increasing the air traversing distance between two adjacent buckets, number of buckets are increased accommodating therein an additional bucket in the assembly to increase the hydraulic performance of the Pelton runner bucket assembly.
According to this invention is provided an improved Pelton runner bucket having a proprietary "stepped flank" profile, in which the height of the side flanks is reduced by an extent varying from zero mm near about the pitch circle (jet incidence) location, to a value almost equal to the reduction in peripheral spacing due to increased number of buckets, at the tip zone, while maintaining the outflow angles almost exactly at all such locations where the flanks have been lowered. Thus there are provided two levels in the flank face of the bucket.
The stepped flank typically starts from around the mid (maximum width section) of the bucket and smoothly progresses to a maximum value which is maintained upto the tip side.
By lowering the flanks, the traversing distance between two adjacent buckets, for the water going out of one bucket is increased by an amount by which the flank has been lowered. This additional space is utilized for accommodating an additional bucket in the assembly. The additional bucket, thus accommodated in the space created by lowering the flanks, contributes to increasing the hydraulic performance of the turbine. The angles of the various sections at the outflow edge along which the water leaves the bucket, is maintained almost as it were, at the corresponding un-lowered point earlier. Thus flow dynamics are maintained unaltered and better performance obtained by increasing number of buckets without any increase in diameter to width ratio.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 is an isometric view of one bucket of the prior-art design listing the various parts
Fig. 2 shows three views of an improved Pelton runner bucket highlighting the difference compared to prior art buckets.
Fig. 3 shows two isometric views of the improved Pelton runner bucket showing the superimposed linework of prior-art bucket.
Fig. 4 is an isometric view showing a typical assembly featuring only three adjacent runner buckets in order to highlight the plurality.
Fig. 5a & 5b show a close-up view and a long shot of an assembled Pelton turbine runner according to the invention.
Fig. 6 shows comparison of a typical cross section for the prior-art and invented Pelton runner bucket in the lowered flank domain.
Fig. 7 shows the improved Pelton runner assembly at the test stand.
DETAILED DESCRIPTION OF THE PREFFERED EMBODIMENT OF THE
Referring now to the accompanying drawings and initially to Fig. 1, the prior-art design is shown in an isometric view depicting the various parts. It is symmetric about the splitter (2), which is shaped like an elevated inclined ridge. Each sculptured bowl like surface, called bucket face (4), on either side of the splitter, is an exact mirror image of the other and is the surface along which the water flows after bifurcation of the jet of water at the splitter. The lateral end of both the bucket faces is a planar flat surface of almost uniform thickness called the flank (1). One longitudinal end of the bucket faces integrates firmly with a segment of solid disk (5). This end happens to be the inner end and is nearer to the rotational axis. The position of the bucket relative to the axis, which is determined by the length of the segment of solid disk, fixes the pitch circle diameter (D), which is the diameter of the circle in a plane passing through the splitter and crossing through all the buckets at the point of impact of the jet, while having its center at the center of rotation of the turbine. The maximum distance between opposite flanks is the bucket width (B). A smooth "U" shaped notch, truncates the other longitudinal end of the bucket face. This end of the bucket faces is called the tip end. The truncated end of both the adjacent bucket faces put together resembles a "W" with rounded edges called the cutout (3). Portions of the flank on either side, starting from the near end and extending almost upto the position of maximum width of the bucket are called the inner segment of flank (lA), whereas the remaining portions of the flank are called the tip segment of flank (1B). Both the segments are located at the same elevation.
Fig. 2 shows three views of the present invention, (a) shows view from the top, (b) shows view from the side and (c) being an isometric view. The tip segment of the flank (1B) (shown shaded for clear identification) is located at a lower elevation than the inner segment of the flank (1 A).
Fig. 3 shows two isometric views of the present invention from different viewing points. The tip segment of flank of the invention is clearly shown shaded with the tip segment of flank of the prior art also superimposed over it as line-work along its edges.
Fig. 4 shows three adjacent buckets according to the invention positioned as they would be in the assembly to highlight the plurality of the buckets in the runner assembly.
Fig. 5a and 5b show a close-up view and an overall view of the actual assembled Pelton turbine runner assembly of the invention, clearly showing the features.
Fig. 6 shows comparison of a typical transverse cross section for the prior-art and invented Pelton turbine runner bucket in the zone tip segment of flank where the lowering of flank is clearly shown. Additionally it highlights the change in cross-section profile to exihibit the unaltered value of the outflow angles along the flank edges of the bucket face to maintain consistency of flow hydrodynamics along the bucket.
Fie. 7 shows the Pelton runner device of the invention at the test stand.
1. An improved Pelton runner bucket device comprising a plurality of buckets, each bucket having atleast two sculptured bowl-like bucket faces (4) adjoined by a splitter (2), each of the bucket faces (4) being configured identically defining a surface along which the input jet water flows after bifurcation at the splitter (2), the bucket faces (4) each having a flank (1) defined by its lateral end, the flank (1) constitutes of an inner segment (lA) and a tip segment (IB), characterized in that the tip segment (18) is configured to locate at a lower elevation than the inner segment (lA), thereby increasing the bucket width (B)iAfithout increasing the bucket diameter (D) which allows accommodating additional buckets in the device to achieve hydraulic performance.
2. The device as claimed in claim 1, where each bucket face (4) is disposed on either side of the splitter (2).
3. The device as claimed in claim 1, wherein the splitter (2) defines a shape of an elevated inclined ridge.
4. The device as claimed in claim 1, wherein the inner segment (lA) is rigidly integrated to a solid disc (5) provided at a bottom end of the bucket.
5. The device as claimed in claim 1^, wherein the tip end (IB) is truncated by a notch to define a cutout (3).
6. The device as claimed in claim 1, wherein the maximum distance between the flanks (1) of two oppositely disposed buckets defines the bucket width (B). ,
7. The device as claimed in claim 1, wherein the bucket diameter (D) defines the pitch circle diameter being the diameter of a circle in a plane passing through the splitter (2) and passing through all the plurality of buckets at a points of impact of the jet water.
8. The device as claimed in claim 1, wherein height of the flanks (1) of each bucket is reduced corresponding to the existing peripheral spacing of adjacent buckets in a direction Of the tip segnnent (IB).
9. The device as claimed in claim 8, wherein the flank (1) is provided with a stepped profile.
lO.The'device as claimed in claim 9, wherein the stepping of the flank profile (1) originates from the middle of the bucket and reaches the maximum value at the tip segment (IB).
11. An improved Pelton runner bucket device as substantially described herein and illustrated.
|Indian Patent Application Number||1012/DEL/2003|
|PG Journal Number||05/2009|
|Date of Filing||18-Aug-2003|
|Name of Patentee||BHARAT HEAVY ELECTRICALS LIMITED.|
|Applicant Address||BHEL HOUSE, SIRI FORT, NEW DELHI-110049, INDIA.|
|PCT International Classification Number||F03B 1/02|
|PCT International Application Number||N/A|
|PCT International Filing date|