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by David L. F. Gaden Department of Mechanical and Manufacturing Engineering University of Manitoba

An Investigation of River Kinetic Turbines: Performance Enhancements, Turbine Modelling Techniques, and a Critical Assessment of Turbulence Models. by David L. F. Gaden Department of Mechanical and Manufacturing Engineering University of Manitoba. Committee Members.

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by David L. F. Gaden Department of Mechanical and Manufacturing Engineering University of Manitoba

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  1. An Investigation of River Kinetic Turbines: Performance Enhancements,Turbine Modelling Techniques, and a Critical Assessment of Turbulence Models by David L. F. Gaden Department of Mechanical and Manufacturing Engineering University of Manitoba

  2. Committee Members • Dr. E. Bibeau (departmental advisor) • Dr. A. Gole (Electrical Engineering) • Tom Molinski (Manitoba Hydro) • Dr. S. Ormiston (Mechanical Engineering) External Reviewer • Mr. P. Vauthier (UEK)

  3. Outline • Introduction • Technology overview • Recent kinetic hydro developments • Wind energy literature review • Shroud Optimisation • Anchor Experiment • Validation • Conclusion • Future Study

  4. IntroductionTechnology Overview Geographic location with a natural flow restriction

  5. To Power Distribution Turbine, Hub and Generator Shroud (cut away) Anchoring System IntroductionTechnology Overview

  6. IntroductionTechnology Overview ≈ 8 ft Example of a kinetic turbine

  7. IntroductionTechnology Overview • Advantages • No reservoir or spillway – minimal environmental impact • Site selection far less restrictive • No dams or powerhouses – low cost installation • Fast deployment times • Modular – easily scalable energy output • Steady flow rates, steady energy production

  8. IntroductionTechnology Overview • Disadvantages • Possibly dangerous flow conditions • No control over upstream conditions • Turbulence, foreign debris • Unknown fish mortality rate

  9. IntroductionRecent kinetic hydro developments • Little in open literature for river kinetic turbines • Purpose: • To develop modelling techniques for river kinetic turbines • To understand the reliability of these models • Use these models to evaluate performance enhancements for kinetic turbines

  10. Coriolis Program (Gulf Stream) ITDG / IT Power (Sudan) IntroductionRecent kinetic hydro developments* 1970 1980 1990 2000 UEK (Various) Nova Energy, NRC (3 sites) Nihon University (Japan) Scottish Nuclear, IT Power (Scotland) Northern Territory University (Australia) Marine Current Turbines (UK) Horizontal axis turbine Vertical axis turbine Ducted turbine *Adapted from Segergren, 2005

  11. Ontario Power Generation, UEK (Ontario) Hammerfest Strøm AS (Norway) Exim & Seapower (Sweden / Scotland) Hydro Venturi (Various) Stingray Tidal Stream, Eng Business Ltd. TidEl Generator (Unspecified) New Energy (Alberta) Pearson College, et al. (B.C.) Starkraft Development (Norway) IntroductionRecent kinetic hydro developments* 1990 2000 Horizontal axis turbine Vertical axis turbine Ducted turbine *Adapted from Segergren, 2005

  12. Helmy Lewis et al. Igra Phillips et al. Grassmann et al. Helmy Bet et al. IntroductionWind energy literature review 1980 1990 2000 THEORY THEORY E x 3 N x 4 THEORY N x 3.2 E x 1 N x 5 E x 1.3 E x 1.25 THEORY N x 2 THEORY – Paper covers ducted turbine theory N – Numerical study N x 2 x 3 – Results show a power increase by a factor of 3 E – Experimental results

  13. Pa < 60% P∞ Betz limit (Betz, 1926) Shroud OptimisationTheory Conventional turbine Small power available

  14. Greater power available (Lewis et al., 1977) Shroud OptimisationTheory Shrouded turbine

  15. Open passage • Does not capture pressure drop, swirl • Non-linear response to pressure not modelled • Not used Shroud OptimisationTurbine Modelling Four turbine modelling strategies: 1. No model 2. Momentum source 3. Averaging rotating reference frame 4. Sliding mesh rotating reference frame

  16. Open passage • Models turbine as block of momentum • Captures pressure drop • Avoids complex geometry • Does not capture pressure drop, swirl • Non-linear response to pressure not modelled • Not used k – Momentum source factor Shroud OptimisationTurbine Modelling Four turbine modelling strategies: 1. No model 2. Momentum source 3. Averaging rotating reference frame 4. Sliding mesh rotating reference frame

  17. Models turbine as block of momentum • Captures pressure drop • Avoids complex geometry • Does not account for power curves, mechanical losses • Close to Betz theory • ≈ 5% over-prediction of power k – Momentum source factor Shroud OptimisationTurbine Modelling Four turbine modelling strategies: 1. No model 2. Momentum source 3. Averaging rotating reference frame 4. Sliding mesh rotating reference frame

  18. Does not account for power curves, mechanical losses • Close to Betz theory • ≈ 5% over-prediction of power • Models rotor geometry • Averages along circumference of rotation for pseudo steady-state • Streamwise axis-symmetric only Shroud OptimisationTurbine Modelling Four turbine modelling strategies: 1. No model 2. Momentum source 3. Averaging rotating reference frame 4. Sliding mesh rotating reference frame

  19. Models rotor geometry • Averages along circumference of rotation for pseudo steady-state • Streamwise axis-symmetric only • Rotates and interpolates mesh at each time step • Computationally intensive; large output • Fully transient solution Shroud OptimisationTurbine Modelling Four turbine modelling strategies: 1. No model 2. Momentum source 3. Averaging rotating reference frame 4. Sliding mesh rotating reference frame

  20. Shroud OptimisationMomentum Source Design variables: 1. Diffuser Angle

  21. Shroud OptimisationMomentum Source Design variables: 1.Diffuser Angle 2.Area ratio

  22. Shroud Optimisation Momentum Source Model dimensions Flow domain Surface mesh

  23. Shroud OptimisationMomentum Source Variable: Area ratio 15

  24. Shroud OptimisationMomentum Source Variable: Angle ■Power increase by a factor of 3.1 ■ Drag increase by a factor of 3.9

  25. Shroud OptimisationMomentum Source Streamlines for 45° diffuser Streamlines for 20° diffuser

  26. Shroud OptimisationMomentum Source No diffuser versus diffuser

  27. Shroud OptimisationMomentum Source

  28. Diameter: 3.0 m Diameter: 2.4 m Output: 25.6 kW Output: 51.3 kW Shroud OptimisationMomentum Source • If area is limited, shroud will reduce turbine size • Shroud is still beneficial

  29. Shroud OptimisationRotating Reference Frame Tetrahedral mesh Flow domain Hexahedral mesh

  30. Shroud OptimisationRotating Reference Frame A. B. C. D.

  31. Shroud OptimisationRotating Reference Frame Relative power output B. D. A. C. (standard) 84.7% 39.3 kW 95.8% 44.4 kW 100% 46.4 kW 105.5% 48.9 kW

  32. Shroud OptimisationRotating Reference Frame

  33. Power P/P∞ Anchor Experiment • Boundary-layer causes power loss Velocity y/δ U/U∞

  34. To Power Distribution Turbine, Hub and Generator Shroud (cut away) Anchor Experiment Anchoring System

  35. Anchor Experiment • Four anchor models ≈ 3 m A. B. C. D.

  36. Anchor Experiment At 7.5 m downstream from Anchor P / P∞ y / δ

  37. Anchor Experiment Midstream velocity contours

  38. Validation • Particle Image Velocimetry (PIV) used • Six experimental runs: • 2 configurations (nozzle & diffuser) • 3 flow speeds (0.5 m/s, 0.8 m/s and 1.0 m/s) • For each, four CFD simulations performed: • 2 Eddy-viscosity turbulence models (k-ε & SST) • 2 Reynolds stress transport models (SSG & BSL)

  39. Validation Water tunnel test section Ruler (for alignment) Model Laser Mirror Camera

  40. Validation PIV Apparatus TEST SECTION AND MODEL FLUID WITH SEEDING PARTICLES LASER AND OPTICS CAMERA COMPUTER AND SOFTWARE DATA ACQUISITION AND CONTROL SYSTEM

  41. Validation Frame 1 Frame 2 d2 d1 d3 Raw Image Both frames

  42. Validation PIV Streamlines & velocity contours Diffuser, 1 m/s Nozzle, 1 m/s

  43. Validation k-ε streamlines & velocity contours Diffuser, 1 m/s Nozzle, 1 m/s

  44. Validation SSG streamlines & velocity contours Diffuser, 1 m/s Nozzle, 1 m/s

  45. Validation k-ε velocity error Diffuser, 1 m/s Nozzle, 1 m/s

  46. Validation SSG velocity error Diffuser, 1 m/s Nozzle, 1 m/s

  47. Validation Full-field validation results: ■ Root mean square error (RMSE) used to evaluate each model across the entire field:

  48. Validation • PIV Experimental error • Seeding particle density too low • 5 particles / IA recommended (Dantec 2000) • ≈ 3 particles / IA • Velocity up to 55% under-read (Keane et al. 1992) • Field of view too large • Poor handling of high velocity gradients • 60% probability of valid detection (Keane et al. 1992) • Regions with high gradients cannot be trusted

  49. Validation • CFD inlet conditions inadequate • Modelled as uniform flow, but it was not:

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