Abstract

The development of hybrid-electric propulsion technologies for aircraft is believed to be a stepping stone for the aerospace industry to reduce greenhouse gas emissions and achieve 50% of the levels of 2005 by the year 2050. However, the introduction of batteries and power electronics significantly impacts the weight and size of new aircraft concepts that integrate these propulsion units. The traditional design techniques need to be adapted to account for this added weight and allow a more rapid evaluation and comparison between concepts and trade-off studies. New models and methods need to be developed to perform these concept studies in a multidisciplinary design, analysis, and optimization (MDAO) environment, to estimate the size, weight, and performance of non-conventional aircraft. This thesis proposes one such tool, focusing on the aircraft fuel system. The methodology to develop the tool is based on analyzing typical fuel system architectures across a wide range of conventional aircraft and how this approach can be adapted for hybrid-electric propulsion applications. This thesis breaks the system into four major groups (engine fuel feed, fuel transfer, fuel quantity & indicating, and tank venting) and how the weight of each can be estimated from existing component data. For conventional modern turboprop regional aircraft such as the ATR42, the methodology predicts the system weight within 10% of published data. The increased detail built into the tool implementation allows analysis of the variation in system weight arising from major changes to the fuel system architecture encountered in hybrid-electric aircraft. Two case studies of hybrid-electric variants of existing aircraft (the Dornier 228 and ATR42) are investigated to demonstrate the application of the tool. These studies also compare the estimated weight of the fuel system in the hybrid-electric aircraft architecture to that of the conventional propulsion variant, highlighting a reduction in system mass by approximately 10 to 15% relative to the conventional fuel system mass. Limitations and possible improvements of the proposed tool are also discussed. In summary, this thesis contributes to developing the design tool required for sizing the fuel system in conventional and hybrid-electric aircraft.