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
- Independent reports from Eskom
- ACCUG 2017
- IAHR 2017
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.
