3Parts of Pelton Turbine The main components of a Pelton turbine are:(i) water distributor and casing,(ii) nozzle and deflector with their operating mechanism,(iii) runner with buckets,(iv) shaft with bearing,(v) auxiliary nozzle.Auxiliary nozzle is used as brake for reducing the speed during shut down.The runner is located above maximum tail water to permit operation at atmospheric pressure.
5Runner with BucketsThe runner consists of a circular disc with a number (usually more than 15) of buckets evenly spaced around its periphery.Each bucket is divided vertically into two parts by a splitter that has a sharp edge at the centre and the buckets look like a double hemispherical cup.The striking jet of water is divided into two parts by the splitter.
6A 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.
7Bucket Displacement Diagram Design of Nozzle is of Prime importance in Pelton Wheel
10The Nozzle and Jet : A Key Step in Design bad0djet,VCVelocity of the jet at VC:
11Jet carrying a discharge of Q to deliver a power P To generate a discharge of Q, we need a least jet diameter of
12Diameter of the Jet at the outlet, do It is important to find out the VC and outlet jet diameters/areas
13A Consultancy Project Sponsored By BHEL, Bhopal CFD Analysis of Free Jets & Flows In AirP M V SubbaraoProfessorMechanical Engineering DepartmentA Consultancy ProjectSponsored ByBHEL, Bhopal
14The 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,m Turbulent Viscosity
23Pelton Wheel Distributor - CFD Analysis The distributor to the Pelton wheel for the given geometry has been simulated using Fluent in a 3-d viscous incompressible flow simulation.The set of governing equations solved were primarily the continuity and the momentum equations.The given geometry was meshed using the unstructured tetrahedral meshes due to geometrical complexity.An optimized tetrahedral mesh size of 25 was employed resulting in a a total of tetrahedral elements.
31Experimental values of Wheel diameter to jet diameter Dwheel /djet,VC6.57.51020Ns (rpm)353224hturbine0.820.860.890.90P in hp, H in meters and N in rpm
32For maximum efficiency, the ratio should be from 11 to 14. The highest ratio used in the world is 110 (Kt. Glauraus Power House in Switzerland).Specifications of this Pelton wheel are:Power 3000HP (2.24MW) Speed: 500 rpmDwheel= 5.36m djet,VC=48.77mmHead =1,650 m
34Number of bucketsThe number of buckets for a given runner must be determined so that no water particle is lost.Minimize the risks of detrimental interactions between the out flowing water particles and the adjacent buckets.The runner pitch is determined by the paths of;the bucket tip (diameter Dpelton), the Wheel diameter (DWheel).and the relative paths of the water particles stemming from the upper and lower generators of the jet.The bucket pitch must be selected so that no particle stemming from the lower generator of the jet can escape the runner without encountering any bucket.
36Zones of Bucket Duty Cycle i) Approach of the tip to the jet (θj < −40◦).ii) Initial feeding process : (θj = −40◦...−10◦).iii) Entire separation of the jet (θj = −10◦...0◦)iv) Last stage of inflow (θj = 0◦...15◦)v) Last stage of outflow (θj = 15◦...50◦).vi) Series of droplets (θj = −50◦...∞).
49Geometric 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.
52Empirical Geometry of Bucket Shape IVIIIIIVC2biDWSAbeB
53Empirical Relations for Bucket Geometry A = 2.8 djet,VC to 3.2 djet,VCB = 2.3 djet,VC to 2.8 djet,VCC= 0.6 djet,VC to 0.9 djet,VCbi = 50 to 80be is varied from section I to section VI: 300 to 460II: 200 to 300III: 100 to 200IV: 50 to 160V: 00 to 50