Design Analysis of Parts of Francis Turbine P M V Subbarao Professor Mechanical Engineering Department Provision of Features to Blend some Reaction into Impulse…
Spiral Casing Spiral Casing : The fluid enters from the penstock to a spiral casing which completely surrounds the runner. This casing is known as scroll casing or volute. The cross-sectional area of this casing decreases uniformly along the circumference to keep the fluid velocity constant in magnitude along its path towards the stay vane/guide vane.
Design of Spiral Casing dpenstock Rcasing Q Risv How to select Q ?
Spiral Casing for 35 MW Vertical Francis Turbine
Design of Spiral Casing dpenstock Rcasing Q Select a suitable value of discharge per unit: Q Risv But maximum allowable value is 10 m/s Maximum allowable head loss in Penstock =2 to 4% of available head
At any angle q, the radius of casing is: A full spiral is generally recommended for high head 300m, semi-spiral is recommended for low head < 50m. In general k =1.0, however corrected using CFD.
Flow Distribution Analysis of Casing Stay vanes or Guide vanes
Static Pressure Distribution in Casing.
Mega Civil Works for Mechanical Power Generation
Parts of A Francis Turbine
Geometrical Description of A Francis Turbine Parts
Stay Vanes & Guide Vanes The basic Purpose of the stay vanes & guide vanes is to convert a part of pressure energy of the fluid at its entrance to the kinetic energy and then to direct the fluid on to the runner blades at the angle appropriate to the design. Moreover, the guide vanes are pivoted and can be turned by a suitable governing mechanism to regulate the flow while the load changes. The guide vanes are also known as wicket gates. The guide vanes impart a tangential velocity and hence an angular momentum to the water before its entry to the runner. The guide vanes are constructed using an optimal aerofoil shape, in order to optimize off-design performance.
Design of Guide Wheel (Stator): Low Specific Speed
Design of Guide Wheel (Stator): High Specific Speed
Design of the Guide Vanes Diameter of guide vane shaft
Design of the Details of Stay & Guide Vane Wheels Theory of Relatively free Whirling flow: Bsi Bgi The inlet angle can be calculated by assuming a free vortex from the flow coming from the spiral casing rinlet Stay Vane rinlet Guide Vane
Pressure drop versus discharge Pressure drop versus Flow Rate Pressure drop versus discharge
Global Symmetric Flow Domain through Statinary Vanes
Operational Configurations of Guide Vanes
The correlation between the turbine discharge and the guide vane opening angle.
Pressure drop versus guide vane angle
Design of the Guide Vanes How to choose the guide vane maximum angle a0 at full load ? ao
Design of the Guide Vanes Level of Overlapping of the guide vanes
Design of Guide Vanes . L: length of vane L=15 to 30% of Dgo
Max. Opening Position Closed Position Runner inlet (Φ 0.870m) Guide vane outlet for designα) (Φ 0.913m) Max. Opening Position Closed Position
Design of the Guide Vane Outlet Angle The outlet angle can be calculated by assuming a free vortex from the flow in the gap between the runner and the guide vanes Dg0 Bg0 rri
Design of the Guide Vanes How to choose the number of vanes The number of guide vanes has to be different from the number of runner vanes.
Water particle Water from spiral casing
Number of guide vanes
Number of Guide Vanes Ns Z=8 10 12 14 16 18 20 24 <200 <250 Dge,mm Z=8 10 12 14 16 18 20 24 <200 <250 250 - 400 400 - 600 600 - 800 800 - 1000 1000 1250 1250 1700 >1700 >200 <300 300 - 450 450 - 750 750 - 1050 1050 1350 1350 1700 1700 2100 >2100
The Runner
Mean Velocity triangles Across Runner
Velocity triangles rri rre Uri Vwi Vri Vfi Vai Ure Vwe Vre Vfe Vae bi be ae
The transposition of the profiles for all the 11 streamlines
Ub Vwi Vai Vfi Vri Ub Vwi Vai Vfi Vri Vwi Ub Vai Vfi Vri