Design of a turbofan engine cycle with afterburner for a conceptual UAV

A study of two turbofan engine types has been carried out. The purpose was to find a suitable engine to serve as a propulsion unit for a conceptual UAV. The working tool for the preliminary design of the engines was a computer code called Gasturb10. The engines were equipped with afterburners with convergent/divergent nozzles. First a variable cycle engine was studied. This type of engine includes a technique called variable area bypass injection (VABI), whose purpose is to funnel a part of the air either as bypass flow or core engine flow. The simplified flying mission, used as a base for judging the suitability of the engine parameters, consisted of one cruise/loiter part with the afterburner unlit and an afterburner-on dash segment. The total fuel consumption served as an overall target function for optimization. After extensive testing of various settings of bypass ratios and compressor pressure ratios the emerging numbers for these ratios indicated that a standard engine would be equally useful for this particular purpose. This conclusion came as a surprise. The continued effort was focused on a fixed cycle turbofan engine whose characteristics were similar to those of the more complicated VABI engine. The final result consisted of the thrust and fuel consumption tables for different Mach numbers and altitudes valid for the fixed cycle engine. Furthermore, some length dimensions, critical for installation, and weight are included.