Presentation on theme: "Design Analysis of Parts of Pelton Wheel Turbine P M V Subbarao Professor Mechanical Engineering Department Selection of right parts and right geometry."— Presentation transcript:
Design Analysis of Parts of Pelton Wheel Turbine P M V Subbarao Professor Mechanical Engineering Department Selection of right parts and right geometry to execute Pure Impulse…..
HEPP with Pelton Wheel
Parts 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.
Key Parts of Pelton Turbine
Runner with Buckets The 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.
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 Displacement Diagram Design of Nozzle is of Prime importance in Pelton Wheel
Nozzle used in 62.5 MW Pelton Wheel
Mechanism of Control of Jet dimensions
The Nozzle and Jet : A Key Step in Design d0d0 d jet,VC Velocity of the jet at VC:
Jet carrying a discharge of Q to deliver a power P To generate a discharge of Q, we need a least jet diameter of
Diameter of the Jet at the outlet, d o It is important to find out the VC and outlet jet diameters/areas
CFD Analysis of Free Jets & Flows In Air P M V Subbarao Professor Mechanical Engineering Department A Consultancy Project Sponsored By BHEL, Bhopal
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, Turbulent Viscosity
Computational Grid : Nozzle
Contours of Volume Fractions : Nozzle Air Domain : 0.15m
Contours of Static Pressure : Nozzle Air Domain : 0.15m
Contours of Velocity Magnitude : Nozzle Air Domain : 0.15m
Contours of Volume Fractions : Air Domain : 0.3m
Contours of Volume Fractions : Air Domain : 1.0 m
Industrial Correlations for Jet Area Optimal value of Outlet jet area, a o s is the displacement of spear
Pelton 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.
CAD Model of Distributor
Pelton Wheel Flow Distributor
Static Pressure Distribution
Distribution of Velocity Magnitude
Mean Diameter of Pelton Runner Mean diameter or Pitch circle diameter: D wheel Circumferential velocity of the wheel, U wheel
Experimental values of Wheel diameter to jet diameter D wheel /d jet,VC N s (rpm) turbine P in hp, H in meters and N in rpm
For 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 rpm D wheel = 5.36md jet,VC =48.77mm Head =1,650 m
Path Lines of Jet D wheel D pelton dOdO V j,O
Number of buckets The 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 D pelton ), the Wheel diameter (D Wheel ). 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.
Bucket Duty Cycle Reference Position
Zones 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◦...∞).
Minimum Number of Buckets 1B 1C R wheel R pelton D j,O, V j,O 1A 1D The axis of the jet falls on Pitch Circle
Minimum Number of Buckets 1B 1C 1E R wheel R Pelton d j,O, V j,O
Minimum Number of Buckets R Wheel R Pelton d O, V j,O ljlj t j : Time taken bye the jet to travel l j t b : Time taken by first bucket to travel
RWRW RPRP d O, V j,O ljlj t j = l j /V jet,O t b =
For better working t j < t b The minimum allowable value of
RWRW RPRP d O, V j,O ljlj
Maximum allowable angle between two successive buckets Minimum number of buckets Dr Taygun has suggested an empirical relation for z
Bucket Power Distribution P( j) Total
Bucket Energy Distribution E j,k
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.
Shape variations of Buckets
Design 1 Design 2
Empirical Geometry of Bucket Shape A B C 2i2i ee S I IV II III V DWDW
Empirical Relations for Bucket Geometry A = 2.8 d jet,VC to 3.2 d jet,VC B = 2.3 d jet,VC to 2.8 d jet,VC C= 0.6 d jet,VC to 0.9 d jet,VC i = 5 0 to 8 0 e is varied from section I to section V I: 30 0 to 46 0 II: 20 0 to 30 0 III: 10 0 to 20 0 IV: 5 0 to 16 0 V: 0 0 to 5 0