The windmilling characteristics of twin-spool, high bypass ratio turbofan engine have been analyzed. This analysis is an extension of the previously reported analysis for a single-spool turbojet engine. As before, the aerodynamic performances of engine components are determined by incorporating the available cascade loss correlations. For a given flight condition, the steady-state windmilling conditions are determined by iteratively balancing the mass flow rate and angular momentum through the two spools. Compared to the turbojet analysis, the new analysis requires determination of bypass ratio and work split between the two spools. Some of the calculation results have been compared against the limited data available for a CF-6 engine, and the two show good agreement. The present method is thus shown to be capable in predicting turbofan engine’s windmilling characteristics during its design stage.

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