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Nozzles & Jets for Pelton Wheels A Special Device to implement Pure Momentum based Energy Exchange……. P M V Subbarao Professor Mechanical Engineering Department

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Key Parts of Pelton Turbine

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Design Of Intake for High Release of Power p atm H

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Multi Jet Distributors for Pelton Wheels

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Discharge Distribution And Flow Energy Losses In the Distributor Q/Q BEP

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CFD Analysis of Free Jets & Flows In Air A Consultancy Project Sponsored By BHEL, Bhopal 2008 -- 2009

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The set of governing equations solved were primarily the continuity and the momentum equations. These basic equations in Cartesian coordinate system for incompressible flows are given below, Governing Differential Equations

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Arrangement of Jets

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CAD Model of Distributor

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Pelton Wheel Flow Distributor

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Static Pressure Distribution

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Distribution of Velocity Magnitude

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Exit Velocities The area averaged values for the various critical sections are listed below, Inlet:20.77 ms-1 Outlet 1: 25.37 ms-1 Outlet 2:18.13 ms-1 Outlet 3:17.05 ms-1 Outlet 4:16.91 ms-1 Outlet 5:15.22 ms-1 Outlet 6: 9.75 ms-1

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Feedback It is evident from the area averaged values of velocity and the mass fluxes at the outlet that the flow distribution is not exactly uniform. The flow at outlets 2, 3, 4, 5 is almost equal, however, flow at outlet -1 is high and outlet -2 is low. The uniformity of flow distribution may be restored by employing variable openings using the spears provided inside the injection nozzle along with possible alterations in the rate of curvature of distributor especially in the region of outlet-6.

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Closing Remarks : Multi Jet Pelton Wheel Higher rotational speed Smaller runner Simple flow control possible Redundancy Can cope with a large range of flows But Needs complex manifold May make control/governing complex

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A Complex Engineering Micro Alternate To Simple Gigantic Natural System

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Flow Control using Spear & Nozzle System

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Free Surface Expansion Shape for Maximum Power

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Simplification of Nozzle Shape d0d0 d jet,VC The nozzle and spear are perfectly streamlined to reduce friction losses and achieve perfect circular jets.

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Geometrical Relations for Nozzle The values of α varies between 20 to 30° whereas β varies from 30 to 45°.

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Industrial Correlations for Jet Area variation with stroke Optimal value of Outlet jet area, a o s is the displacement of spear

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Discharge through a Spear Nozzle if a o is the jet area at nozzle outlet section and knowing that this is dependable on the stroke s of the needle tip, the water velocity for this section is: Then, the corresponding flow rate is:

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Discharge Control using Spear Nozzle

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Linear Rate of Change Discharge w.r.t Stroke

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Geometrical Relations for Nozzle dOdO 2d O – 2.4d O 5d O – 9d O 0.8d O – 0.9d O 1.2d O – 1.4d O 1.1d O – 1.3d O

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Performance Analysis of Nozzle-Spear Valve Ideal Nozzle-spear Valve: Along flow direction Real Nozzle-spear Valve:

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Pipe MaterialAbsolute Roughness, e micron (unless noted) drawn brass1.5 drawn copper1.5 commercial steel45 wrought iron45 asphalted cast iron120 galvanized iron150 cast iron260 wood stave0.2 to 0.9 mm concrete0.3 to 3 mm riveted steel0.9 to 9 mm

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Numerical Computation of Total Pressure Variation

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Jet carrying a discharge of Q to deliver a power P To generate a discharge of Q, we need a least jet diameter of Acceptable Performance of Nozzle

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Diameter of the Jet at the outlet, d o It is important to find out the VC and outlet jet diameters/areas The Diameter of Jet before Reaching Bucket

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