Compressor failures
Introduction
Compressor surge or Compressor stall is an abnormal situation that is the result of the occurrence of the stall phenomenon on the compressor blades of a gas turbine jet engine. This loss occurs mainly in turbojets with dynamic axial compressors, although it can also appear in turbostarters.
Due to the appearance of this loss in the compressor blades, it loses the ability to correctly compress the air necessary for combustion, which causes a sudden drop in power that can only be suppressed by the decrease in fuel flow to the combustion chamber. There are cases in which the phenomenon manifests itself imperceptibly.
Modern compressors are carefully designed to avoid or reduce the appearance of pumping within the operating range (regimes) of the engine. This phenomenon was very common in the first jet engines, which had simple aerodynamics and manual or mechanical control of fuel consumption. These deficiencies were eliminated with the arrival of automatic aggregates, whether hydromechanical or electrical. An example of this is the FADEC system.
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Rotational losses
Rotational losses are a local disturbance of the compressor's air flow, in which, despite the fact that it continues to compress the air, a group of blades of any rotor fall into a stall without destabilizing the work of the compressor. These blades create turbulent zones that rotate in the direction in which the rotor stage in which the affected blades are located rotates. These zones, however, rotate at 50 to 70% of the rotor speed and as such are capable of affecting all the blades of the same rotor.
Rotational losses can be momentary, resulting from an external disturbance, or they can be constant, in the event that a balance results between affected and unaffected areas. Local losses greatly reduce the compression ratio, affecting the efficiency of the compressor and increasing the structural loads to which the blades are subjected. In many cases, the compressor blades lose the ability to stabilize disturbances and the turbulent areas grow and become a complete loss of the compressor.