Evolution of the Allison Model 250 Engine

Evolution of the Allison Model 250 gas turbine engine is traced from model inception to the more recent 250-C28B, C28C and C30 models. The application of advances in compressor, combustor and turbine aerodynamics, coupled with the application of newly developed analytical techniques, has resulted in production engine models with improved performance and a high degree of confidence.

Recent aerodynamic and structural advances have permitted the evolution of a single stage 8.5:1 centrifugal compressor from a multi-stage 7:1 axial-centrifugal compressor characteristic of earlier 250 models. This increase in pressure ratio is accomplished without loss of compressor efficiency, resulting in a 6% improvement in SFC.

The application of improved analytical techniques also has permitted a more accurate assessment of the stress and vibratory state of recontoured turbine airfoils resulting in reduced losses and increased aerodynamic efficiency.