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Research Papers: Flows in Complex Systems

Out With the Old, in With the New: Pelton Hydro Turbine Performance Influence Utilizing Three Different Injector Geometries

[+] Author and Article Information
S. Petley

Lancaster University Renewable Energy Group
and Fluid Machinery Group,
Engineering Department,
Engineering Building, Bailrigg,
Lancaster, Lancs LA1 4YR, UK

A. Židonis

Lancaster University Renewable Energy Group
and Fluid Machinery Group,
Engineering Department,
Engineering Building, Bailrigg,
Lancaster, Lancs LA1 4YR, UK

A. Panagiotopoulos

Lancaster University Renewable Energy Group
and Fluid Machinery Group,
Engineering Department,
Engineering Building, Bailrigg,
Lancaster, Lancs LA1 4YR, UK;
School of Mechanical Engineering,
National Technical University of Athens,
Athens 15780, Greece

D. Benzon

Mott MacDonald, Ltd.,
Victory House, Trafalgar Place,
Brighton BN1 4FY, UK

G. A. Aggidis

Lancaster University Renewable Energy Group
and Fluid Machinery Group,
Engineering Department,
Engineering Building, Bailrigg,
Lancaster, Lancs LA1 4YR, UK
e-mail: g.aggidis@lancaster.ac.uk

J. S. Anagnostopoulos, D. E. Papantonis

School of Mechanical Engineering,
National Technical University of Athens,
Athens 15780, Greece

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received July 5, 2018; final manuscript received December 10, 2018; published online January 30, 2019. Assoc. Editor: Satoshi Watanabe.

J. Fluids Eng 141(8), 081103 (Jan 30, 2019) (14 pages) Paper No: FE-18-1458; doi: 10.1115/1.4042371 History: Received July 05, 2018; Revised December 10, 2018

In previous works, the authors presented computational fluid dynamics (CFD) results, which showed that injectors with noticeably steeper nozzle and needle tip angles 110 deg & 70 deg and 150 deg & 90 deg, respectively, attain higher efficiency than the industry standard, which, according to available literature on the public domain, ranges from 80 deg to 90 deg for nozzle and 50–60 deg for needle tip angles. Moreover, experimental testing of the entire Pelton system showed that gains of about 1% in efficiency can be achieved; however there appears to be an upper limit beyond which steeper designs are no longer optimal. This study aims at providing further insight by presenting additional CFD analysis of the runner, which has been coupled with the jet profile from the aforementioned injectors. The results are compared by examining the impact the jet shape has on the runner torque profile during the bucket cycle and the influence this has on turbine efficiency. It can be concluded that the secondary velocities, which contribute to the development of more significant free-surface degradations as the nozzle and needle tip angles are increased, result in a nonoptimal jet runner interaction.

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Figures

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Fig. 1

Schematic 2D sketch of the injector geometry highlighting the geometric and operational variables [15]

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Fig. 2

Contours indicating the losses as a result of different nozzle and needle (spear) angles at flow rates 20 kg/s (left) and 40 kg/s (right) [19]

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Fig. 3

Three-dimensional geometry indicating planes used in the analysis

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Fig. 4

Hybrid mesh model of the standard Pelton injector with views showing refinement at (1) needle tip and (2) nozzle outlet

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Fig. 5

Three-dimensional CFD injector losses at different planes from nozzle exit

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Fig. 6

Fluid power from conversion of static to dynamic pressure components for the three designs

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Fig. 7

Static pressure contours for standard and novel 2 designs

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Fig. 8

Dynamic pressure contours for standard and novel 2 designs

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Fig. 9

Gilkes twin jet Pelton turbine operating at NTUA

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Fig. 10

Pelton efficiency curves for standard and novel injectors at different speeds

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Fig. 11

Secondary velocity vectors developed before reaching the guide vanes

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Fig. 12

Secondary velocity vectors developed after reaching the guide vanes

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Fig. 13

Comparing the secondary velocity vectors at different planes from nozzle exit

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Fig. 14

Experimental photograph showing upper jet detachment

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Fig. 15

Vertical velocity profile comparison for standard and novel injector designs at plane z/D = 1

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Fig. 16

Vertical velocity profile comparison for standard and novel injector designs at plane z/D = 4

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Fig. 17

Comparing the 3D vertical, 3D horizontal, and 2D axisymmetric axial velocity profiles for the standard injector design at plane z/D = 2

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Fig. 18

Three-dimensional injector domain indicating the plane used for analysis

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Fig. 19

Two-dimensional runner domain indicating the corresponding plane used for analysis

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Fig. 20

Moment monitor wall zone definition—inside (light gray) and outside (dark gray)

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Fig. 21

Grid convergence study: efficiency with respect to grid spacing

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Fig. 22

Torque developed on inside and outside bucket surfaces for four configurations

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Fig. 23

Pressure coefficient distribution on the inside surface of bucket 1 at 80 deg rotation for two configurations

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Fig. 24

Volume fraction (free-surface) isoplots for the different designs at 100 deg rotation

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Fig. 25

Volume fraction (free-surface) and vertical velocity vectors for standard design

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