Design of a Geared Turbofan Module for Small, Unmanned Aircraft Applications

This paper provides detailed analysis and considerations for the design, manufacturing, and testing of a fan module for a small, geared turbofan. The purpose of this research is to design a fan module to fill an operational gulf in small unmanned aircraft propulsion systems: to produce higher thrust and lower thrust specific fuel consumption than a turbojet, but also operate at higher air speeds and altitudes than a turboprop, while maintaining a higher propulsive efficiency. An optimized fan design that increases the range, endurance, and flight envelope for unmanned aircraft could significantly advance the applications of such aircraft in society. The fan module will be designed to integrate with a KingTech K45TP 5 kW turboshaft engine, of which its operating conditions will be used to size the fan. The design will start with a parametric cycle analysis to determine an optimal bypass ratio and fan compression ratio based on desired values and improvements of specific thrust and thrust specific fuel consumption. AEDsys software was utilized to verify the results of the parametric cycle analysis and later determined the geometry and sizing of two different fan designs: including airfoil shape, blade twist and length, number of blades, and overall fan diameter. The fan modules were modeled in SolidWorks and manufactured using a 3D printer in hopes to gain experimental data in future work. This would include testing the fan modules on an 5 kW electric system in Oklahoma State University’s wind tunnel and compared to the experimental results found in the design process. The analysis results showed promise for the implementation of a ducted turbofan propulsive system for added range and endurance of unmanned aircraft.