Analysis of the Propulsion System of an Electric Aircraft
Examensarbete för masterexamen
Electric power engineering (MPEPO), MSc
Kollara Pradeep, Chandrima
Abstract This thesis focuses on the design and development of control laws, specially crafted for the propulsion system of the ES-30 aircraft, a creation of Heart Aerospace AB. The ES-30 distinguishes itself as a hybrid electric aircraft, designed for regional travel and outfitted to accommodate 30 passengers. This study unfolds the intricate relationship between the propulsion system and the electrical counterparts, outlining the control laws and the effective functioning of this aircraft. The control function is a network that feeds on the thrust request and air data as its inputs and provides RPM and pitch angle as outputs. This strategic combination is designed to deliver the requested thrust while concurrently maximizing the efficiency of the propulsion system. This idea is taken one step further by accounting for electrical losses that pervade through the propulsion system. These losses are primarily attributed to motor and inverter losses, which vary across different operational phases and time duration. They are integrated into the system-wide considerations to determine the final propeller pitch and motor RPM. Such a holistic approach guarantees a comprehensive understanding of the system’s functioning and the implementation of the most efficient control laws. From our analysis, it has been determined that the optimal RPM - pitch combinations for the Take off, Climb and Cruise flight phases are 1750 rpm and 20.3°, 1650 rpm and 29.15°, 1350 rpm and 31.7°respectively. These combinations offer optimal efficiency during the associated flight phases, a conclusion derived from thorough analysis. The average efficiency of the flight across the Take off, climb and cruise phases for when optimizing for the the propeller efficiency alone was noted to be 82.43 % and compared to 82.49 % when optimizing for the entire propulsion system efficiency. It was also observed that the propeller’s and the entire propulsion system’s optimum operating point is at the same RPM for flight phases with higher thrust demand - Take Off and Climb, while they are different for the phases with lower thrust demand, Cruise. Since the aircraft is in Cruise for the longest time, it makes a difference in the performance of the aircraft.
Keywords: Electrical aircraft, thrust, efficiency, thermal, motor, pitch, RPM, algorithm, comparison. v