the meaning term of surging and stall in centrifugal compressor

[Masdede]

can anyone explain about the meaning of surging and stall? why surging only happened in centrifugal compressor not in other type of compressor? what factors that could be caused of surging?

[Lowrider]

Surging is started by the controller in cause of a fault. When the compressors starts to get overheated, by what ever cause, the controller will start the surge, meaning opening and closing the vanes to try and cool the compressor. If this last to long the compressor will be shut down.

Only centri's have vanes!

[ptsac]

Read this for decent info.

http://www.mcquaybiz.com/mcquaybiz/l.../AG_31_002.pdf

[Magoo]

Vane opening to harsh verus load, slow and easy. Sudden evap loads and rapid vane opening equals overcurrent, compressor overload, if a stall happens, your current protection is out of spec., re-calibrate the whole system to design set-up. The alternative is killing the thrust assembly, snapping shafts, burning out drive motors.
magoo

[gary cato]

stall is the beginning of surge no flow or limited flow. surge is the reversal of flow in the comp. causes are high condenser pressures or low load.

[Thermodynamic]

The forces that act on the refrigerant vapor within the centrifugal compressor impeller can be broken down into 2 components. One component acts to move the refrigerant away from the impeller in a radial direction. This component is called radial velocity (Vr).
The second component acts to move the refrigerant in the direction of impeller rotation. This component is called tangential velocity (Vt).
Together, these components generate the resultant velocity vector (R), the length of which is proportional to the amount of kinetic energy in the refrigerant. Recall that kinetic energy is converted to static energy, or static pressure.
Consider a given-diameter compressor impeller that rotates at a constant speed. As the load on the chiller decreases, the inlet vanes partially close and the flow rate of refrigerant through the compressor drops. Radial velocity (Vr), which is proportional to refrigerant flow, decreases as well.
Even though the speed of rotation and diameter of the impeller are constant, the tangential velocity (Vt) (which is proportional to the product of impeller rotational speed and impeller diameter) drops because of the pre-swirling of the refrigerant caused by the inlet vanes.
The result is a shorter resultant velocity vector (R), which means that less static pressure is generated.
As the load and the corresponding refrigerant flow rate continue to fall, the radial velocity (force) drops, too. At some point, the radial force becomes smaller than the generated static pressure, letting the pressurized refrigerant vapor flow backward from the diffuser passages into the impeller. This instantaneously reduces the pressure within the passages below the radial force and the compressor is able to re-establish the proper direction of refrigerant flow.
This condition is known as surge. So long as this unstable load condition exists, the refrigerant alternately flows backward and forward through the compressor impeller, generating noise and vibration.

[Thermodynamic]

Only centrifugal compressor surge because they are not positive displacement devices. Recips, screws and the like are postive displacement and are not subject to surges. They will perform lift requirements until thier HP cannot overcome the lift or they overload the drive motor.

[Peter_1]

Surging is started by the controller in cause of a fault. When the compressors starts to get overheated, by what ever cause, the controller will start the surge, meaning opening and closing the vanes to try and cool the compressor. If this last to long the compressor will be shut down.

Only centri's have vanes!

Surging is in my opinion a phenomena which is stopped by the controller and not provoked by it.
Surging has nothing to do with the vanes.
It's the same phenomena, the same forces can be applied when an airplane stalls.
The explanation of Themodynamic was for my 2 cents spot on it.