Jets Buckets for Pelton Wheels P M

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Jets & Buckets for Pelton Wheels P M V Subbarao Professor Mechanical Engineering Department Means to Complete the Second Law of Power Retrieval…….

Geometrical Relations for Nozzle 1. 1 d. O – 1. 3 d. O 2 d. O – 2. 4 d. O 0. 8 d. O – 0. 9 d. O 5 d. O – 9 d. O 1. 2 d. O – 1. 4 d. O

Numerical Computation of Total Pressure Variation

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

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

A Set of Relations • A jet of finite velocity needs to have a relation with peripheral velocity of wheel. • A jet of finite area need to have a relation with dimensions of bucket. • A bucket of finite dimensions and shape should have a relation with wheel.

Jet Vs Mean Diameter of Pelton Runner Mean diameter or Pitch circle diameter: Dwheel D wheel Circumferential velocity of the wheel, Uwheel

Jet Power & Conditions for Maximum Power Define, Blade Speed Ratio as

Implication of Maximum Power Condition

For maximum efficiency

Optimal values of Wheel diameter to jet diameter 30 25 20 15 10 5 0 0 5 10 15 20 25 30 Ns 35 40 45 50

Experimental values of Best values of Wheel diameter to jet diameter Dwheel /djet, VC 6. 5 7. 5 10 20 Ns (rpm) 35 0. 82 32 0. 86 24 0. 89 10 0. 90 hturbine P in hp, H in meters and N in rpm Essential to have a minimum of 10 for acceptable turbine efficiency.

Extreme Engineering Conditions The highest ratio used in the world is 110 (Kt. Glauraus Power House in Switzerland). Specifications of this Pelton wheel are: Power 3000 HP (2. 24 MW) Dwheel= 5. 36 m Head =1, 650 m Speed: 500 rpm djet, VC=48. 77 mm

The Second Relation : Jet Vs Bucket

External stroboscopic flow visualization

Runner with Advanced Buckets

Bucket Displacement Diagram

• A notch made near the edge of the outer rim of each bucket is carefully sharpened to ensure a loss-free entry of the jet into the buckets, • i. e. , the path of the jet is not obstructed by the incoming buckets.

BUCKET GEOMETRIC DEFINITIONS

Geometric Details of Bucket The hydraulic efficiency depends more on the main bucket dimensions (length (A), width (B) and depth (C)). The shape of the outer part of its rim or on the lateral surface curvature also has marginal effect on hydraulic efficiency.

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