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Old 06-01-2004, 07:35 PM
Brian Carlton Brian Carlton is offline
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Join Date: May 2002
Location: Blue Point, NY
Posts: 25,396
Peter,

The exhaust gas temperature of a gas turbine will behave in similar manner to a piston engine. When the gas turbine is brand new, and all the internal seals are just about perfect, the engine will have an EGT margin of about 30 degrees C. What this means is that the engine, at maximum takeoff power, will be running 30 degrees less than the maximum allowable temperature. As the engine gets older, and things begin to wear, and the compression ratio drops, the EGT margin will erode and the EGT will climb. The engine can continue in service until the EGT margin gets to 0 degrees C. At this point, the engine will be at the maximum allowable EGT at maximum takeoff power. Any further erosion in the internal clearances for the engine will result in a negative EGT margin. Normally, this is when the engine requires removal for a rebuild.

A typical temperature for the exhaust of a large turbofan is about 600 C. (1112 F.). Their compression ratios typically run up to about 40:1 or so.
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