Hi
I am looking for a generic information about surge in gas turbine .
but I didn't find any suitable facts.
well I need your help for this mater .
thanks for your help.
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
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