Limiting TGTs for engine life
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Limiting TGTs for engine life
Flying what is a fairly new type, we have introduced a TGT limit for normal operation to limit the amount of wear, which has been noticed, on the hot end of the engine.
This figure, from what I can ascertain, has just been plucked out of the air and is some 80% of MCT. But still the engines are falling short of their expected life by 20% due to excessive wear of the turbine blades. These engines are FADEC controlled and P&W have changed the fuel nozzle spray pattern to try and help matters, but to be honest there seems to have been little affect.
The manufacturers don't seem to think that this reduced TGT is going to make any difference, but then follow that statement by remarking they have collated little data or evidence as the engines are too new/young. I think what they are trying to say is they don't want to commit themselves.
So anyway to my question.....
It stands to reason that treating engines carefully will increase ther life and not flying around at MCT is going to reduce centrifugal faorces and temperature extremes in the engine. But what if this limit is too low, can that have a detrimental affect on the engine. My point being is there a theory out there that if the engines are run continuously "too cold" could this lead to hot spots being formed as the mass flow through the engine is not sufficient and in turn causing damage. How about formation of deposits on the blades etc etc.
I would be very interested to hear your views.
This figure, from what I can ascertain, has just been plucked out of the air and is some 80% of MCT. But still the engines are falling short of their expected life by 20% due to excessive wear of the turbine blades. These engines are FADEC controlled and P&W have changed the fuel nozzle spray pattern to try and help matters, but to be honest there seems to have been little affect.
The manufacturers don't seem to think that this reduced TGT is going to make any difference, but then follow that statement by remarking they have collated little data or evidence as the engines are too new/young. I think what they are trying to say is they don't want to commit themselves.
So anyway to my question.....
It stands to reason that treating engines carefully will increase ther life and not flying around at MCT is going to reduce centrifugal faorces and temperature extremes in the engine. But what if this limit is too low, can that have a detrimental affect on the engine. My point being is there a theory out there that if the engines are run continuously "too cold" could this lead to hot spots being formed as the mass flow through the engine is not sufficient and in turn causing damage. How about formation of deposits on the blades etc etc.
I would be very interested to hear your views.
Prof. Airport Engineer
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Got some details on the particular engine model, thrust rating, and the numbers? In particular, what type of operation - average flight hours per flight cycle, takeoff environment (hot or cool, sea-level or mountains), and if possible installed EGT margin?
Got some details on the particular engine model, thrust rating, and the numbers? In particular, what type of operation - average flight hours per flight cycle, takeoff environment (hot or cool, sea-level or mountains), and if possible installed EGT margin?
Reduced operating temperatures will increase engine turbine life without negative engine performance or structural impact on other areas.
The reasons for the increased turbine wear could be poor turbine blade material properties, excessive turbine tip gap clearances or more likely excessive tip gap clearances in the compressor.
The tip gap clearances are often associated with bending and/or ovalization of the engine case structure (Thermals, manuevers etc.)
There are plenty of performance curves available to the tech side of your house to show you what you will get if your crank back on the throttle and EGT at cruise
The reasons for the increased turbine wear could be poor turbine blade material properties, excessive turbine tip gap clearances or more likely excessive tip gap clearances in the compressor.
The tip gap clearances are often associated with bending and/or ovalization of the engine case structure (Thermals, manuevers etc.)
There are plenty of performance curves available to the tech side of your house to show you what you will get if your crank back on the throttle and EGT at cruise
