Moment of Momentum

1
Moment of Momentum
This is the torque exerted on the fluid.
2
Compressor Configuration
W1
V1
U
U
Vu1
W1.5
V1.5
Vu1
U
Vu1.5
Vu1.5
W relative to blades, V absolute velocity, Vu
tangential compenent
3
Compressor Pressure Ratio
4
Surge

• Surge Strong flow instability induced as a
  result of a massive flow reversal in one or
  several compressor stage(s)?flow reversal ?reduce
  volume flow ?adverse pressure drop ? flow
  reattaches?volume increase ?adverse pressure
  re-establishes ?flow reversal and cycle repeats
  itself

Pressure
Volume
5
Rotating Stall

• One or several blades experience massive flow
  separation, i.e., stalled. This package of
  stalled fluid then propagates around the blade
  row and very large structural vibrations can be
  induced as the blades periodically enter and
  depart from stalled state.

• Effective angle attack increases and new cell
  stalls

• Mass flow is redirected to other neighboring
  blades

stalled
Stalled cell shifted