Centrifugal Blowers:

Notes (will format into a better document later):

  • inWC (inches of water column): Pressure unit, frequently used in fans to represent small changes in pressure
  • What is static pressure?
    • Relative pressure to ATM?
    • fans produce positive static pressure
  • Air moving through a pipe (constant diameter) will have max air velocity at center and zero at pipe walls
  • Flow rate is calculated as : Q (flow rate) = A (cross-sectional area) x V (average velocity of the fluid)
    • Avg velocity is 90% the max velocity of the velocity
  • Find Reynold's Number of the fluid:
    • Needed to see if the flow is laminar or turbulent
      • If Re < 2000, laminar flow
      • If higher turbulent
  • Total Pressure: Static Pressure + Velocity Pressure 
    • Used to calculate mech efficiency
  • Bernoulli's principle of continuity:
    • When air velocity increases, the static pressure decreases.
    • When air velocity decreases, the static pressure increases.
  • Centrifugal fans with FC Blades (Forward Curved)

  • Vacuum Cleaners centrifugal fans usually have 6-8 blades
  • 50 > CFM is needed to transport sand
    • Have at least a safety factor of 1.5-2 to account for frictional pressure drops in the pipes.
  • In suspended flow of particles in air, the particle's velocity is 80% of that of average air velocity in horizontal pipeline
  • Material to air ratio, 2:1
  • Vacuum cleaners use diffusers
  • Performance of a typical vacuum cleaner
  • Motor and Drive Arrangements for centrifugal fans
  • One Big Disadvantage of FC Fans:
    • Brake horsepower overloading during free delivery, hence oversize motor is used as a precaution.
  • Mitigate static pressure
  • Fan Laws?
  • Specific Speed and Specific Size?
  • Understand static pressure better



Resources:

Bleier-FanHandbook.pdf (Great resource to understand on how centrifugal blowers/fans work and what design considerations to make)

https://www.engineeringtoolbox.com/pneumatic-solids-transports-d_134.html

https://www.cedengineering.com/userfiles/Pneumatic%20Conveying%20Systems-R1.pdf