1 part b2: hydropower b2.2 hydropower system design

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  • Slide 1
  • 1 Part B2: Hydropower B2.2 Hydropower system design
  • Slide 2
  • 2 B2.2 Hydropower system design Topics: System design Entry arrangements Forbays, penstock inlets Penstocks and surge control Size of the penstock, pressure forces, anchoring the penstock, water hammer and its control Exit arrangements draft tubes Turbine selection Force triangles, Turbine types, specific speed, cavitation and its prevention Electronics and control Types of generator, Turbine control, transmission
  • Slide 3
  • 3 B2.2.1 Hydropower system design Entry arrangements: Anatomy of a forebay
  • Slide 4
  • 4
  • Slide 5
  • 5 B2.2.1 Hydropower system design Entry arrangements: Trash rack losses Values for K t
  • Slide 6
  • 6 B2.2.1 Hydropower system design Entry arrangements: trash racks
  • Slide 7
  • 7 B2.2.1 Hydropower system design Entry arrangements: Alternatives to trash racks
  • Slide 8
  • 8 B2.2.1 Hydropower system design Entry arrangements: Velocity into the penstock v1v1 v3v3 p1p1 p3p3 Energy line v2v2 p2p2 htht Typical values for penstock velocities 2-5 m/s
  • Slide 9
  • 9 B2.2.1 Hydropower system design Entry arrangements: Entry losses into the penstock
  • Slide 10
  • 10 TypeKeKe Hooded1.0 Projecting0.8 Sharp corner0.5 Slightly rounded0.2 Bell mouth (r>0.14D)0 B2.2.1 Hydropower system design Entry arrangements: Entry losses into the penstock
  • Slide 11
  • 11 B2.2.2 Hydropower system design Penstocks: Comparison of penstock materials MaterialFriction loss WeightCorrosion resistance CostEase of Jointing Pressure resist Ductile iron Asbestos cement Concrete Wood staves GRP uPVC Mild steel HDPE MDPE PoorExcellent
  • Slide 12
  • 12 B2.2.2 Hydropower system design Penstocks: Installation
  • Slide 13
  • 13 B2.2.2 Hydropower system design Penstocks: Friction losses in penstocks Darcys formula See B2.1.1 Typical penstock losses are 5-10%
  • Slide 14
  • 14 B2.2.2 Hydropower system design Penstocks: Multiple penstocks
  • Slide 15
  • 15 B2.2.2 Hydropower system design Penstocks: Losses in bends
  • Slide 16
  • 16 B2.2.2 Hydropower system design Penstocks: Losses in bends r/DKbKb 10.6 20.5 30.4 40.3 For 45 use K x 0.75 For 2 use K x 0.5 r D
  • Slide 17
  • 17 B2.2.2 Hydropower system design Penstocks: Other Losses Contractions Valves D 1 /d 2 KcKc 1.50.25 20.35 2.50.40 50.50 TypeKvKv Spherical0 Gate0.1 Butterfly0.3
  • Slide 18
  • 18 B2.2.2 Hydropower system design Penstocks: Energy lines
  • Slide 19
  • 19 B2.2.2 Hydropower system design Penstocks: Anatomy of a penstock
  • Slide 20
  • 20 B2.2.2 Hydropower system design Penstocks: Slide blocks
  • Slide 21
  • 21 F e = Force due to extension C e = Coefficient of extension = Change in temperature E = Youngs modulus D = Penstock diameter t = Wall thickness B2.2.2 Hydropower system design Penstocks: Thermal expansion FeFe FeFe
  • Slide 22
  • 22 B2.2.2 Hydropower system design Penstocks: Expansion joints
  • Slide 23
  • 23 B2.2.2 Hydropower system design Penstocks: Forces on bends Hydrostatic Velocity F = fluid density g = gravity h = total head A = penstock area Q = discharge v = velocity
  • Slide 24
  • 24 B2.2.2 Hydropower system design Penstocks: Bends
  • Slide 25
  • 25 B2.2.2 Hydropower system design Penstocks: Forces on bends: Thrust blocks
  • Slide 26
  • 26 B2.2.2 Hydropower system design Penstocks: Anatomy of a penstock
  • Slide 27
  • 27 B2.2.2 Hydropower system design Penstocks: Water hammer
  • Slide 28
  • 28 T c =critical time (s) L =pipe length (m) C p =speed of sound in the pipe C w = speed of sound in water (1420m s -1 ) G = bulk density of water (2GPa) E =Youngs modulus D =diameter of the pipe (m) t =wall thickness (m) h =additional pressure due to water hammer (m of water) g = gravity v =Change in flow velocity (m s -1 ) B2.2.3 Hydropower system design Penstocks: Water hammer
  • Slide 29
  • 29 B2.2.2 Hydropower system design Penstocks: Water hammer: Dealing with it
  • Slide 30
  • 30 B2.2.2 Hydropower system design Penstocks: Water hammer: Dealing with it: Surge tanks
  • Slide 31
  • 31 B2.2.2 Hydropower system design Penstocks: Getting it wrong
  • Slide 32
  • 32 B2.2.3 Hydropower system design Draft tubes Parallel sidedTapered Allows turbine to be set above water level but uses vacuum pressure on underside to increase effective head Recovers part of the velocity head by diffusion action Limited by the vapour pressure of water
  • Slide 33
  • 33 B2.2.3 Hydropower system design Draft tubes: Exercise Using Bernoulli's equation and mass continuity, show how a tapered turbine regains velocity head and converts it to pressure reduction at the turbine p 2 v 2 p 1 v 1
  • Slide 34
  • 34 B2.2.3 Hydropower system design Draft tubes: configurations
  • Slide 35
  • 35 B2.2.3 Hydropower system design Draft tubes
  • Slide 36
  • 36 B2.2.3 Hydropower system design Draft tubes
  • Slide 37
  • 37 Nextturbines