Experimental Investigation of a Mini Turbofan Engine with Respect to Turbojet for its Thrust Modulation

Abstract

Gas turbine engines have been used in power houses, ships and aircrafts in general for propulsion. They are extremely powerful for their size and have very high thermal efficiency. Large airliners and military aircrafts use turbofans while small scale aircrafts such as mini UAVs and ultralight jet still use turbojets which are not as fuel efficient as turbofans. The purpose of this research is to investigate whether a mini turbofan should be developed for UAVs or not. Would it be more fuel efficient than the similar sized-turbojet as is the case in large scale turbofans? For this purpose, a mini turbofan was developed by taking off-the-shelf turbojet, installed a fan on the turbojet via a secondary turbine and a gearbox. A K60-TP engine manufactured by KingTech was used. A fan was attached to the engine inside a shroud and mounted on a test stand. The engine was run at different throttle positions where the fan’s RPM, fuel consumption, and thrust were recorded. With the available data, the Thrust Specific Fuel Consumption (TSFC) was calculated and was compared to a turbojet of the comparable size and thrust. It was observed that the turbofan came out to be 38% more fuel efficient than the turbojet. The results indicate that a mini turbofan would be more economical to operate than a turbojet of its comparable size, hence development of mini turbofan engines for commercial purpose is desirous. Mini turbofans, if commercially produced, would eventually phase out mini turbojets currently in use