Gas Turbine Compressor Blades

[jimbo1]

Can anyone tell me the effect of leading edge radii on stall margin? I.E.- How does the stall margin change as leading edge radii get larger from erosion? Can this be put in terms of the % stall margin loss/gain versus leading edge change in per cent?

 

[ferdo]

Hi,

I don't know if somebody will tell you a relation between stall margin loss/gain versus leading edge but I'm sure about followings facts:

The blades are serviceable if there are no loss of coating. no change in color, no evidence of sulphidation on adjacent blades, geometrical deviations do not exceed the limits which are imposed by manufacturer

The condition of blades and tips is critical to obtain rated power. Most significant blade tip defects (rubs and oxidation) increase interturbine temperature (T5). Even if T5 is below maximum, an HSI may be recommended
In the same time, you will probably have a decresed Ng, and whole of these because of a CT stator vanes burned/flow area increased or a CT blade tip oxidation/rub.

For example, when a compressor turbine stator examination reveals trailing edge burning has resulted in a loss of airfoil area of more than manufacturer indicates in his maintenance manual, on any one vane, and the burnt area can be seen from the leading edge of the stator vane when viewed parallel to longitudinal axis of the engine, the entire set of CT blades must be scrapped.

Engines operating in sandy or dusty environments or in smog or salt-laden atmospheres should be subjected to additional inspections for corrosion and compressor erosion.

Anyway, each manufacturer will tell you the same words: change the blades when the engine performances are affected (if the blades are the cause of performance losses) sending the whole bladed disk assembly to an approved overhaul facility.

Hope this will help you (sorry for disappointing you with that relation). Regards
Fernando

 

[DickHovey]

Talk with Praxair's Airfoil Management Division. They'll give you lots of background. They do a lot of the world's compressor blade refurbishment, restoring L/E radii and profile.