Performance uncertainty propagation analysis for control-oriented model of a turbine-based combined cycle engine

Uncertainty sources in an integrated turbine-based combined cycle propulsion system considered in this study are located at the air intake system, containing a forebody, a splitter and a cowl. These components endure aerothermodynamic loading and variational pressure distribution due to oblique shocks, which cause them to deform and vibrate. Those deformations and vibrations are largely determined by the local flow field and structural characteristics of the propulsion system in real time, which are hardly to be modeled. The unanticipated uncertainties bring in fluctuations on performance, and may even lead to inlet unstart, compressor surge, or combustor overtemperature, and bring about difficulties in designing control systems that can meet certain requirements on performance. Therefore, uncertainty propagation is made to figure out the effects of uncertainties associated with the three components on control-oriented performance analysis of a turbine-based combined cycle engine. A control-oriented loosely coupled aircraft/propulsion integrated turbine-based combined cycle engine model is built. Monte Carlo Method is utilized to propagate the uncertainties. The results reveal that uncertain sources may bring about failure in mode transition because of the possibility that the gross thrust with uncertainties exceeds the limits. Further analyses indicate that the principal contributor to the uncertainties of outputs in low speed flow path varies from the forebody to the splitter as transition process goes on.