Overview

Seals ^[*] are found within the gas turbine's internal air system. In summary, the seals serve to separate hot (working) gases from the cooling air required to ensure that the lubricating oil and bearings stay cool. Fully understanding their function in any one engine involves knowing the internal air system thoroughly.

Some manufacturers are known for their superior cooling design. Better cooling adds cost to the overall engine both in terms of manufacture and performance efficiency. With manufacture, items such as laser-drilled internal passages on blades and vanes would add to the overall cost of cooling seen in the cost of manufacture. With performance, any air used for cooling is not available to be part of the working gases (that turn the turbine and develop the power). This then reduces the efficiency possible for any given air mass intake at the compressor inlet. (Note also that nonworking air is also used for subsidiary systems other than cooling. In the case of aircraft engines, for instance, the air may be used for, among other uses, the cabin air-conditioning system).

The priorities that different manufacturers set on this item are well known among seasoned gas turbine engineers who have worked with every major manufacturer's engines. They are also well known to overhaul and repair shops that see the results of less cooling. It is the operators who wear the final results.