Design of Components of Francis Turbine P M V Subbarao Professor Mechanical Engineering Department Detailing to Infuse Reaction….

Specific speed in rpm P in hp & H in meters

Selection of Speed of A Turbo Machine Zp : Number of pairs of poles of the generator

Design of Any Selected Francis Turbine Unit Different capacities for each sub-group. Design for Normal Head. Assume an overall efficiency: 94 – 96% Calculate the required flow rate.

General Layout of A Hydro Power Plant Power Tunnel: Diameter: 15000mm Length= 746m Slope= 1 in 120 Actual velocity: 5.563m/s

Power Tunnel Channel Bed Slope

Penstock : Consider Velocity equal to Actual Site Velocity

Estimate net Head available at the inlet turbine casing Pipe Material Absolute Roughness, e micron (unless noted) drawn brass 1.5 drawn copper commercial steel 45 wrought iron asphalted cast iron 120 galvanized iron 150 cast iron 260 wood stave 0.2 to 0.9 mm concrete 0.3 to 3 mm riveted steel 0.9 to 9 mm Estimate net Head available at the inlet turbine casing

Dimensions of Guide Vane Wheel Group NO. Unit Size MW Degree of Reaction, % Dpenstock m Vpenstock m/s Head loss 1 135.9 35 2 40 3 45 4 203.9 5 6

Design of Spiral Casing dpenstock Rcasing Q Risv Inlet to Stay vanes

Runner Guide vanes Ring Stay vanes Ring

Design of the Guide Vanes How to choose the guide vane angle aegv at full load

Specifications of Guide Vanes Slow Runner: Ns=60 to 120 Begv/Dmgv=0.033 – 0.04 Normal Runner: Ns = 120 – 180 Begv/Dmgv=0.125 to 0.25 Fast Runner: Ns = 180 to 300 Begv/Dmgv=0.25to 0.5 L: length of vane L=15 to 30% of Degv

Dimensions of Guide Vane Wheel Group NO. Unit Size MW Degree of Reaction, % Digv, m Degv, m Bgv, m 1 135.9 35 2 40 3 45 4 203.9 5 6

Design of the Guide Vane Outlet Angle The outlet angle can be calculated by assuming a vortex from the flow in the gap between the runner and the guide vanes rigv Begv regv Select appropriate value of n

Design of the Details of Stay Vanes Theory of Relatively Whirling flow: Bisv rinlet Stay Vane Besv rexit stay Vane

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 heat <50m. In general k =1.0, however corrected using CFD.

Performance of Casing : Loss of Total Pressure Rcasing Risv dpenstock Q The losses in the spiral casing as a sum f distributed losses and the exit losses

Friction losses Friction losses in the spiral casing and stay vanes Guide vane losses Gap losses Runner losses Draft tube losses

Number of Guide/stay Vanes Ns Z=8 10 12 14 16 18 20 24 <200 Dge,mm <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

Validation of the Guide Vanes Design Degree Overlapping of the guide vanes High Overlap Low Overlap

Specifications of Guide Vanes L: length of vane L=15 to 30% of Degv

Minimum Number of Guide/stay Vanes Ns Z=8 10 12 14 16 18 20 24 <200 Dge,mm <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

Velocity triangles rri rre Uri Vwi Vri Vfi Vai Ure Vwe Vre Vfe Vae bi be ae

Water particle Water from spiral casing

Diameter of guide vane shaft Vs Runner Inlet Diameter DRI DRE Dmgv

Design of the Runner Vanes How to choose the number of vanes The number of guide vanes has to be different from the number of runner vanes.

Ub Vwi Vai Vfi Vri Ub Vwi Vai Vfi Vri Vwi Ub Vai Vfi Vri

Inlet Velocity Triangles Vs Ns Low Specific Speed : Slow Francis Runner Vwi Vai Vfi

Inlet Velocity Triangles Vs Ns Low Specific Speed : Normal Francis Runner Vwi Vai Vfi

Inlet Velocity Triangles Vs Ns High Specific Speed : Fast Francis Runner Vwi Vai Vfi

Specifications of Runner Slow Runner: Ns=60 to 120 ai = 150 to 250 Kui = 0.62 to 0.68 bi = 900 to 1200 Bgv/Dmgv=0.04 – 0.033 Normal Runner: Ns = 120 – 180 ai = 250 to 32.50 Kui = 0.68 to 0.72 bi = 900 Bgv/Dmgv=0.125 to 0.25 Fast Runner: Ns = 180 to 300 ai = 32.50 to 37.50 Kui = 0.72 to 0.76 bi = 600 to 900 Bgv/Dmgv=0.25to 0.5

Velocity triangles rri rre 13o < be < 22o Uri Vwi Vri Vfi Vai Ure Vwe Vre Vfe Vae bi ai be ae 13o < be < 22o

Design for Maximum Power

Net Positive Suction Head, NPSH

NPSH required

Dimensions of the outlet 13o < be < 22o 1,05 < a < 1,15 0,05 < b < 0,15 Highest value for highest head

Remaining head to be used : Extra head to be converted into kinetic energy: Preferred Exit Velocity Triangle: DRI DRE 13o < bRE < 22o

Available Inlet velocity Triangle

Runner Design