Turbojet Analytical Model Development and Validation

This paper describes the modeling and validation procedure of a single shaft turbojet engine. The model aim is to provide detailed predictions of the flow’s properties at nozzle outlet. Those predictions will be used to design a thrust vectoring system for the engine, and the flight dynamics control laws of the aircraft. The first phase of the analysis explains the design and development a more detailed engine deck. The engine to model is a single shaft turbojet. The software developed calculates the turbojet performances in steady state; boundary conditions of the turbojet may be modified according to the engine-operating envelope. During the second phase of the analysis, the transient model was developed. Dropping the work compatibility equation, and introducing the angular acceleration and inertial moments allow to model the engine vs. time behavior. By using the data calculated through the steady state and transient 1-D models, the CFD model could be properly designed. The model defines the flow field going from the turbine’s outlet through the nozzle to the turbojet plume downstream. In this way the estimation of the forces and moments acting on the thrust vectoring vanes can be calculated. The three models were validated using test bench data, synthetic data (previous steady state engine decks) and flight test data.