Aerodynamic Analyses of an Integrated Low-Pressure Compression System for Adaptive-Cycle Micro Turbofan Type Jet Engine

Abstract

Unmanned Aerial Vehicles (UAVs) are commonly propeller-driven and low-speed. The concept of cost-efficient, much higher speed and longer range applications of micro jet engines was previously addressed such that an existing basic turbojet engine was converted into a single spool turbofan without using additional components of booster and low pressure turbine. Normally, this situation emerges matching problems since two spools are required to adjust the fan speed independently. A simple solution was to use a Continuously Variable Transmission (CVT) gearbox to adjust optimal speed for the fan. As a result, missing of the positive functionality of the booster would lump into the fan root to form a unified low pressure compression system (unified-LPC). Such a unified-LPC demands unique characteristics of having an extreme twist, very high pressure ratio and mass flux at the root section than at the tip section, despite the exact opposite is being enforced due to the wheel speed rise with radius. In light of these challenges, this work aims to investigate detailed aerodynamics of an existing design previously made and reported by the authors. It is shown that, despite the aerodynamic loading contrast throughout the span, the unified-LPC can still have a wide operating range and acceptable off-design aerodynamics. Complementing the previous design- oriented work, this paper aims to provide guidelines for such unified compression systems.