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Matimba Case Study

Fan installation and test results.

Fan Design

  • EU H2020 funded project – MinwaterCSP
    • Design, build and install a 30 ft diameter axial flow fan
    • Primary goal: reduction in water usage through increased efficiency
  • Matimba – Lephalale, South Africa
    •  Owner – Eskom
    • 6 x 625 MWe
    • 6 x 48 axial flow fans – 30 ft in diameter
  • Additional design criteria for new fan
    • Protection against wind effects
    • Operate away from harmful excitation frequencies
    • Reduce fan blade weight
    • Ensure blade weight and mass distributions are accurate
    • Blades must be completely interchangeable
  • Duty point
  • Higher fan static efficiency
  • Protection against wind
  • R-fan based on a 1994-design
  • Research demonstrates superior performance of R-fan
  • Aerodynamic force – Computational Fluid Dynamics (CFD)
  • Strength analysis – Finite Element Analysis (FEA)
  • High safety factor combats fatigue
  • FEA – Modal analysis
  • Experimental data from in situ tests at Matimba
  • Large scale to model scale
  • Accurate blade setting angle reduces vibration
  • Consistent weight of fan blades
  • Consistent weight distribution of fan blades

Static Test Results

  • Confirmed that fan blade weight and weight distribution is repeatable and accurate (<0.8% deviation)
  • Fan blade weight 50% reduction on current fan installed at Matimba
  • Confirmed that natural blade frequencies avoid resonance frequencies as identified at Matimba
  • Maximum moment before structural failure measured

In Situ Test Results

  • Fan produces same volumetric flow rate as conventional fans
  • Power consumption is reduced by 16 – 21%
  • Alternatively flow rate can be increased by 10 – 15%
  • Fan operates away from excitation and natural frequencies – no resonation
  • Steeper fan pressure characteristics offers protection against wind

Results Summary:

Aerodynamic improvement:

  • Reference fan consumes 16 – 21 % less power than current Matimba fan for similar flow displacement
  • Alternatively: volume flow rates can be increased by 10 – 15%
  • Greater protection against detrimental effects of wind

Structural improvement:

  • Negligible blade excitation due to favourably designed modal characteristics
  • Fatigue on blades and gearboxes greatly reduced
  • Fan blade weight is reduced by ½
  • Dramatically reduces stress on blades and gearboxes during start-up
  • Blade shape and structure is consistent (within 0.8 % by weight and 0.6 % by natural modes)
  • Blades are interchangeable and vibrational loads due to imbalance negligible
  • Maximum operational load far below yield point (safety factor 2.8) Fatigue negligible.

Flow rates
increased by
10 – 15%

Stress reduced
on blades and

Fan blade
weight reduced
by 50%

16 – 21%
less power