What type of air is the source of bearing pressure seal air and bleed air for cooling?

The accurate answer for the type of air that serves as the source of bearing pressure seal air and bleed air for cooling is secondary air. In gas turbine systems, different types of air are designated based on their function and location within the system.

Secondary air is typically sourced from the compressor stage of the turbine and is responsible for providing necessary cooling and pressurization for various components, including seals in the bearings. This air helps maintain the integrity of the bearing system and prevents contamination from the hot gases present in the turbine's operational environment. The controlled input of secondary air also aids in the efficient functioning of the turbine by ensuring that components remain within optimal temperature and pressure ranges, enhancing performance and reliability.

In contrast, primary air is generally used for the combustion process itself, while tertiary air may refer to additional air that acts in more specialized roles, usually not directly related to the primary cooling or pressurization functions. Residual air would not typically be designated as a source of cooling or sealing air, as it implies remnants from previous processes or stages rather than actively controlled air used for operational purposes.