Individual Effects of Components on Cycle/Propulsive Efficiency for Variable Cycle Engines

Abstract

The present paper presents a quantification method for the potential benefits of applying geometrically variable components to an UCAV aero engine concept. The method includes thermodynamic modeling techniques for a set of geometrically variable components as well as an optimization strategy to find the optimal schedule of the geometry variations in dependence of flight condition, figure of merit and engine constraints. First, a conventional generic two-spool mixed-flow turbofan engine comprising state-of-the-art component technology is designed as a baseline configuration. Then this cycle is used to study the influence of individual geometrically variable components on the thermodynamic cycle and finally to quantify the performance gain at selected off-design conditions. This examination serves as a preliminary study for the design of an optimal variable cycle engine (VCE). It does not investigate the optimal design of variable components for a specific task. An optimization process chain based on the commercial software framework ModelCenter™ is developed and applied to find the optimal settings of the geometrically variable components for different figures of merit at certain flight conditions. Finally, the baseline configuration without variable components is compared to the variable cycle configuration and the benefits of the geometrically variable components are assessed for a generic UCAV mission.