A NUMBER of aircraft are now being designed, or are actually flying, with auxiliary power systems utilizing the expansion of air bled from the compressors of main propulsion gas turbines. These include systems which heat the bleed air through the agency of a combustion chamber on the auxiliary power motor.
The design requirements for machinery of this class are very unusual, and are believed to be unique in the field of turbine engineering. These factors are particularly prominent with respect to range of gas supply conditions and control characteristics.
The influence of these factors on practical design requirements is discussed in this paper. Emphasis is placed on the comparative advantages and limitations of turbine systems with these characteristics in view.