Guide vanes in Francis turbines El Cajon HONDURAS

Guide vanes in Francis turbines

El Cajon, HONDURAS

Revelstoke, CANADA

La Grande 3, Canada P = 169 MW H = 72 m Q = 265 m 3/S D 0 = 6, 68 m D 1 e = 5, 71 m D 1 i = 2, 35 m B 0 = 1, 4 m n = 112, 5 rpm

La Grande 3, Canada

Guide vane cascade, Francis

Guide Vane End Seals • High efficiency • Less erosion • Less leakage in closed pos.

Guide vanes Main function: Adjust the turbine load The guide vanes consist of number of blades that can be adjusted in order to increase or reduce the flow rate through the turbine. The vanes are arranged between two parallel covers normal to the turbine shaft.

Pressure distribution and torque L D L Torque D Arm

Guide vanes in closed position

Guide vanes in open position Pressure distribution can be found using Bernoulli’s equation: Contour of the guide vane Trailing edge Pressure distribution along the contour of the guide vane:

Pressure distribution along the contour of the guide vane: Stagnation. Point at Leading Edge Guide vane contour Small flow rate Large flow rate

Variation of the torque when the guide vane opening changes: a 0 2 3 1 4 Sin a 0

cm 1 c m 1 Powerplant ns a 0 Skjærka 66 12 Dynjafoss 208 27, 5 Nedre Vinstra 69 12 Oltesvik 264 38, 5 Hol I 72 13 Iverland 269 31, 5 Mesna 78 13 Fiskumfoss 308 40, 5 Røssåga 104 18 Fiskumfoss 308 36, 5 Grønsdal 113 23 Gravfoss 346 37 Nore II 198 34 Solbergfoss 365 38

The guide vane maximum angle a 0 at full load Powerplant ns a 0 1 Skjærka 66 12 2 Nedre Vinstra 69 12 3 Hol I 72 13 4 Mesna 78 13 5 Røssåga 104 18 6 Grønsdal 113 23 7 Nore II 198 34 8 Dynjafoss 208 27, 5 9 Oltesvik 264 38, 5 10 Iverland 269 31, 5 11 Fiskumfoss 308 40, 5 12 Fiskumfoss 308 36, 5 13 Gravfoss 346 37 14 Solbergfoss 365 38 NB: This is for Norwegian designed GE-turbines Guide vane angle Specific speed, ns

The servo’s work

The servo has to: Take care of the torque from all guide vanes for all guide vane angles The torque consist of: Hydraulic torque Friction torque

Hydraulic torque The hydraulic torque can be found from a CFD -analysis

Friction torque ff (W, a)= empirical value m = friction factor H = Head d

Opening Cl ing Friction Stroke Hy dra uli c Op eni ng High head Francis turbine Measurements of the servo’s work for ces Fully open Force in 1000 kg os

Horse shoe vortex damage

Cavitation damage

Sand erosion in the guide vanes Jhimruk Hydro Power Plant

Head cover Guide kvane shaft Bottom cover

The deflection of the head cover H = 435, P = 25 MW 1 2

Reduction of clearance

Efficiency of repaired turbine [MW] H = 430 m

Design of the Guide Vane Inlet Angle • The inlet angle can be calculated by assuming a free vortex from the flow coming from the spiral casing B Dinlet Guide Vane rinlet Stay Vane

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 B 0 r 1 D 0

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.

Design of the Guide Vanes How to choose the guide vane maximum angle a 0 at full load a

Design of the Guide Vanes Overlapping of the guide vanes

Design of the Guide Vanes Number of guide vanes

Design of the Guide Vanes Diameter of guide vane shaft D 1 D 2

Statement of Problem Givens Net head…………. . …. 201. 5 m Flow rate…………. . . 2. 35 m 3/s Turbine speed…. 1000 rpm Work out Design of Runner, Guide vanes, Stay vanes, Spiral casing and. Draft tube Compare. Design output with Jhimruk turbines Design Considerations Calculations - based on hydraulic principles only, Thickness of runner blades - neglected, Designs of components - done for the best efficiency point, Other several assumptions - mentioned locally in calculations.

Design of Guide Vanes Chosen: Nos. of guide vanes z =20 D 1 Diameter of guide vane axis D 0 = D 1 (0. 29 Ω+1. 07) D 2 .

Design of Guide Vanes Tangential and meridional velocities Assuming gap between runner and guide vanes 5% of the runner inlet diameter. . tan α(gvo) = Cm(gvo)/Cu(gvo) α(gvo) = 12. 210 Value of αgvo in full guide vane open position is selected 180

Design of Guide Vanes Velocities at outlet, axis and inlet of guide vanes (depending on varing values of α and t) Outlet agvo=12. 210 tgvo=5 mm Cm(gvo) = 8. 582 m/sec Cu(gvo) = 39. 65 m/sec Cgvo = 40. 56 m/sec Axis Inlet agvc=28. 040 tgvc=30 mm Cm(gvc) = 9. 521 m/sec Cu(gvc) = 17. 87 m/sec Cgvc = 20. 25 m/sec agci=340 tgvi=15 mm Cm(gvi) = 7. 864 m/sec Cu(gvi) = 11. 65 m/sec Cgvi = 14. 06 m/sec . L = 204

Design of Guide Vanes .

Runner inlet (Φ 0. 870 m) Guide vane outlet for designα) (Φ 0. 913 m) Closed Max. Opening Position

Water particle Water from spiral casing