Windmill Modelling of Advanced Turboprop Engines

This thesis work, developed in collaboration with AvioAero - A GE Aviation Business, has the goal to analyze the behavior of an engine in windmill conditions. The windmilling phenomenon is among the sub-idle conditions of an aircraft engine. Windmilling is in far off-design conditions, because of this, the aero-thermal processes within the components are extremely complicated and neither fully understood nor simple to predict. The objective of this thesis project is the prediction of the core speed curve after engine shutdown earlier with a mathematical model. The mathematical model is based on a simple learning algorithm and consists of two different regressions. The mathematical model was built from experimental flight data obtained during the Denali aircraft test flight campaign. Prediction of the behavior of the engine during the shutdown was studied also using NPSS (Numerical Propulsion System Simulation). NPSS is a component-based object-oriented engine cycle simulator that allows the analysis of the transient performance prediction of the engine. An integrated model was used, and some power extraction elements were analyzed and corrected