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
- Needed to see if the flow is laminar or 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