Abstract
Current environmental policies for the aviation sector motivate the use of cleaner propulsion alternatives in order to reduce their CO2 footprint and noise pollution in the coming years. In this context, hybrid propulsion systems have emerged as a potential solution, as they have demonstrated a good trade-off between performance and low pollutant emissions. The present work carries out a comparison between parallel and series hybrid propulsion systems using heterogeneous and homogeneous distributed propulsion architectures. In order to highlight the opportunities of distributed propulsion systems and validate the methodology developed, a single propulsion hybrid configuration is used as baseline case for this study. For the propulsion system sizing, this work uses a parametric modelling tool, which includes a constraint analysis coupled with a weight estimation module to determine suitable configurations for a environmental monitoring mission. The latter module includes semi-empirical correlations to size the electric and mechanical components for each propulsion setup. From the results, it has been found that for the representative case of monitoring in the Galapagos Islands, which requires an endurance of approximate 7 h, the parallel hybrid system using three distributed propulsors presents the best performance features in terms of fuel savings, showing a 34% reduction compared with the baseline case. To summarize, the main contribution of this study lies on the development of a methodology to set potential hybrid distributed propulsion configurations for UAVs aimed for determined monitoring missions.
Highlights
During the last decade, Unmanned Aerial Vehicles (UAV) have been used for different civil applications, such as ecosystem monitoring, marine patterns surveillance, and search– rescue missions [1,2], among others
The study compared three different parallel hybrid-electric system designs, each with three unique battery discharging profiles using a constrained static formulation based on traditional aircraft designs, which shows it is possible to achieve up to 40% fuel saving compared to conventional systems using a clutch configuration
In 2015, Friedrich [6] proposed a design and sizing process for a hybrid-electric propulsion, using experimental data from the ICE and electric motor (EM) linked with PC software packages, which shows that a 210 MTOM single seat prototype aircraft can achieve a fuel saving of 37%
Summary
During the last decade, Unmanned Aerial Vehicles (UAV) have been used for different civil applications, such as ecosystem monitoring, marine patterns surveillance, and search– rescue missions [1,2], among others. In 2015, Friedrich [6] proposed a design and sizing process for a hybrid-electric propulsion, using experimental data from the ICE and EM linked with PC software packages, which shows that a 210 MTOM single seat prototype aircraft can achieve a fuel saving of 37%. In 2019, researchers from Delft University [10] presented a preliminary sizing method suitable for the conceptual design of hybrid-electric aircraft, which uses the power train architecture and the associated propulsion air-frame integration effects by modifying the flight performance. Hybrid propulsion systems are combined with other new technologies, such as distributed propulsion, which increases the performance of the aircraft [13,14,15] This versatility comes with the complexity of defining the proper hybrid architecture for a determined mission profile (see Figure 1)
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