This paper discusses the results of analytical studies supported by current development efforts and research paths to implement fast start technology for small gas turbine APU's, using non-metallic rotor components.
APU start system weights can be a significant fraction of the total installed APU weight, especially if fast starts are demanded under sub-Arctic environments. It is shown that both start system weight, and rotor containment armor weight are proportional to the product of rotational speed squared and rotating assembly inertia. Significant weight savings are therefore feasible with rotating assemblies using lower density materials such as ceramics and composites.
Recent tests are described at the authors affiliation wherein a modified T20 small gas turbine was accelerated from zero to 100% speed in 2 1/2 seconds.