surge in gas turbine

Surge is caused when the airfoils that make up the compressor stages stall. They stop generating lift, which means they can't maintain a positive pressure gradient through the compressor. At the moment of stall, you have high pressure gas in the combustor. Without the compressor maintaining the pressure gradient, that gas heads back out through the compressor. Surging is also called "compressor stall". Just search that term on google and you'll find a bunch of stuff.
On commercial jet engines, surging is audible as a "bang" or "pop" noise from the engine. A bad surge may cause the engine to burp flames out the front.
Surging is typically very bad for the engine, since the compressor section isn't built to withstand the gas temperature coming out of the combustor.
Tom.

To add to your comments--you also have the stagnation (hung stalls). These are unrecoverable, results in speed unwind to sub-Idle and if allowed to continue, even for a short period of time.will quickly generate turbine overtemperatures to the point of hot section component failures. At the higher altitudes, low flight speeds, they generally don't produce the big loud bang associated with the POP stall. In these cases the pilot might not even recognize that the engine.is in a stall condition. He notices the speed rollback to sub Idle, the lack of throttle response and then the overtemperature. Throttle chop to off becomes the only option at this point MLD

To be simplyfied, the air flow is not smooth, but the compresser still works at a normal condition, so the unsmoothly air flow goes worse....
Will you tell me what kind of ur gas turbine is? What work for? How many stages the compresser is?

thanks for your help.but I need some more information about this mater . I want to know : 1- How surge phenomenon is initiated ? 2- How it can be diagnosed? 3- How it can be provided ? 4- what are side effects of surge in gas turbine performance?
thanks for your help

Dear mohammad.hamze:
Google surge cause diagnosis "gas turbine"
13,500 hits, the first page-full appears to be applicable to your questions.
David A. Smith

Surge (stall) in a jet engine is caused by many factors: First, the compressor map is a plot of compressor pressure ratio vs air flow. The engine has both steady sate and transient operating lines. Also, on the same map is the compressor stall line. The difference between them is "stall margin". If the engine SS or Transient operation hits the stall line then you get the typical POP stall. High operating lines can be the result of engine hardware downstream of the compressor--such as, effective turbine nozzle area, small exhaust nozzle area, overfueling the engine etc., damage to the compressor--FOD. In addition, an improper stator vane schedule can force the operating line to the stall point as well as drive the compressor blading into an "instability boundary". If you penetrate the instability boundary blades break off in fractions of a second. No problem diagnosing a stall. The POP (or recoverable) stall produces a very loud bang. At times, a burst of flame comes out of the engine inlet and at other times a significant flame out the tailpipe. If you were to record the compressor discharge pressure you would see it drop to as much as 1/3 its initial value and recover to its original value. The total time would be in the order of .020 to 050 seconds. Side effects: sometimes nothing, other times damage to various components. Hung stall, Speed unwind to below Idle, exceedence of turbine temperature limits, hot section damage, no throttle response. In a single engine application, a hung stall can result in loss of the aircraft if the pilot cannot shut the engine down and get a relight in time. As an aside, I've seen both engines in a twin engine installation go into a hung stall resulting in a crash. Recognize that my comments are rather basic in attempting to keep things simple. MLD