The Impact of Electric Machine and Propeller Coupling Design on Electrified Aircraft Noise and Performance

Abstract

Novel propulsion systems have been studied in literature to reduce aircraft emissions with hydrogen or other electrical energy sources. Hybrid Electric Propulsion (HEP) system consists of electric machines as an alternative way to provide power for propulsion resulting in the reduction of aircraft fuel consumption. While reduction of emission is the main driver of new HEP designs, aircraft noise reduction and performance improvement will also need to be investigated. Much quieter electrified aircraft than conventional aircraft is explored with considering the benefits of coupled design between the propeller and electric machines. In this study, several electric machine designs have been explored and coupled with the propeller design to study the trade-off between the aerodynamic and acoustic performance of the propeller. Aerodynamic optimization is used as a baseline to minimize the energy consumption to find the aerodynamics optimum subject to constraints on the thrust levels during the mission. The propeller aerodynamic optimizer considers the electric machine efficiency map, which is a function of propeller torque and rotational speed, to find the optimum combination of propeller and electric machine designs. The objective function of the acoustic optimizations is to reduce the cumulative noise level over the entire mission. It is shown that a wider envelope of peak motor efficiency in the efficiency map provides acoustics and aerodynamic performance benefits. The trade-offs between reducing noise or increasing aerodynamic efficiency to reduce energy consumption are demonstrated.

The Impact of Multi-Stack Fuel Cell Configurations on Electrical Architecture for a Zero Emission Regional Aircraft

“…For this study fundamental equations and finite element Compressor adiabatic efficiency 85% Table 2 PEMFC system specifications analysis have been employed for electric motor modelling. The integration of electric motor to the propeller have been explored in [23], where a similar architecture have been used. The design decisions for the electric motor and the propeller are explained to reduce noise and energy consumption.…”

Integrated Mission Performance Analysis of Novel Propulsion Systems: Analysis of a Fuel Cell Regional Aircraft Retrofit

“…However, such high power (2MW) and low rpm (1212rpm) make the combination of torque requirement and low rpm very demanding, and the motor design becomes more challenging, resulting in heavier machines. In [28], the torque demand and rpm were calculated for a different number of propellers and a fixed maximum aircraft power requirement. The 8-propeller configuration is selected because it favors motor design at 500kW power requirement per propeller/motor and 2224rpm propeller speed without the need for using a gearbox.…”

“…The power electronic is modeled based on existing component models and the efficiency contours are obtained [29]. More details on the motor design by the authors are presented in [28] Voltage selection The selection of system voltage for the electric powertrain has been studied with considering the trade-offs between, weight reduction (ex. cable's weight, where lower total weight is expected for higher voltages), and at higher voltage and increasing altitude the occurrence of arcing increases as a result of the decrease in the breakthrough voltage with decreasing surrounding air pressure, or the reduction of conduction and Ohmic losses in power electronics and electric machines but with an increase of switching losses due to high voltage demand, and lack of high power density protection systems for high voltage distribution.…”

“…On the other side, if the motor power was designed with a power limit very close to the rated power of the propulsion system (~500kW), around 800kg or total mass could have been saved but at take-off, there would be a risk of overheating and constraints should be imposed regarding the continuous operating time at this power. A motor design trade-off study between efficiency across the mission and motor mass is included in [28]. Further work should investigate the design trade-off between motor efficiency (related to motor power limit), motor mass and operational constraints, and how the optimum trade-off may shift toward choosing higher motor power limit as the technology advances and higher motor power densities are achieved.…”

Set-Based Design Space Exploration to Investigate the Effect of Energy Storage Durability on the Energy Management Strategy of a Hybrid-Electric Aircraft

“…Currently, few studies have been published targeting this specific problem but limited to the Urban Air Mobility (UAM) sector [5,6]. This gap falls within the scope of the FutPrint50 project [7], which aims to identify and assess the role of the key technologies required for the successful implementation of hybrid-electric propulsion for regional turboprop airplanes [8][9][10]. Alongside this technical goal, the project aims to develop a design space exploration and optimization framework that takes into consideration the uncertainty of a new design and provides multiple alternatives in deciding which concept to pursue for a given set of top level requirements.…”