Performance Assessment of an Integrated Parallel Hybrid-Electric Propulsion System Aircraft

Abstract

Hybrid-electric propulsion system promises avenues for a greener aviation sector. Ground research work was performed in the past for the feasibility assessment, at the system level, for such novel concepts and the results showed were promising. Such designs, however, possess unique challenges from an operational point of view, and for sizing of the sub-system components; necessitating further design space exploration for associating with an optimal operational strategy. In light of the above, the paper aims at presenting an operational analysis and performance assessment study, for a conceptualised parallel hybrid design of an advanced geared turbofan engine, based on 2035 timeframe technology level. It is identified that the hybrid power operation of the engine is constrained with respect to the requirement of maintaining an adequate surge margin for the low pressure side components; however, a core re-optimised engine design with consideration of electrical power add-in for the design condition, relieves such limit. Therefore such a design, makes it suitable for implementation of higher degree of hybridisation. Furthermore, performance assessment is made both at engine and engine-aircraft integrated level for both scenarios of hybrid operation and the benefits are established relative to the baseline engine. The performance at engine level engine specific fuel consumption (SFC), thrust specific power consumption (TSPC), and overall efficiency, shows improvement in both hybridised scenarios. Improvement in SFC is achieved due to supply of the electrical power, whereas, the boost in TSPC, and overall efficiency is attributed to the use of higher efficiency electrical drive system. Furthermore, it is observed that while the hybridised scenario performs better at engine level, the core re-optimised design exhibits a better saving for block fuel/energy consumption, due to the considerable weight savings in the core components.

A Review of Concepts, Benefits, and Challenges for Future Electrical Propulsion-Based Aircraft

“…Under the scenario, it gives an opportunity for sizing the core for a lower thrust requirement condition and benefit from a more efficient cruise operation. The study performed by Sahoo et al [33], highlights the beneficial aspect of a core resizing scenario on the surge margin, relative to a baseline design, when hybridized for same level of power. Furthermore, this concept benefits from requiring a reduced size conventional engine to meet operational requirement under one engine inoperative (OEI) condition [34].…”

“…For a fully electric or a hybrid electric configuration, where battery is used as the energy source, successful application is largely attributed to a higher battery specific energy [16,17,104]. Furthermore, the inefficiencies in the electrical system components limits the amount of energy delivered to the propulsor and hence impacts the amount of fuel that the system can offset [33]. Understanding of the key performance parameters (KPPs) are essential in order to define the parameters necessary for operation and understand the likelihood of technology infusion.…”

“…Furthermore, parallel hybrid electric design gives an opportunity for choosing the engine cycle for optimum performance benefits [39,90]. An engine design with a core sized accounting electric power addition, however, expands the surge margin limitation and allows for a higher degree of hybridization [33]. Along this line, a concept of discrete parallel hybrid electric operation was proposed in which both turbo fans and electric ducted fans (EDFs) are meant to operate independently without any serial or parallel connections [44].…”

Enabling the Potential of Hybrid Electric Propulsion Through Lean-Burn-Combustion Turbofans

“…A non-electrified, two-and-a-half-shaft geared turbofan engine configuration with 2035 EIS year technology assumptions (Zhao et al, 2019a;Sahoo et al, 2019) is employed as baseline engine for the purposes of this study. As previously mentioned, a multi-point synthesis method is used for gas turbine engine design and steady-state performance, where synthesis variables at hot-day top-of-climb (TOC) are varied to achieve the synthesis targets at hot-day end-ofrunway take-off (EOR T/O) and Cruise operating conditions.…”

Assessment of a Turbo-Electric Aircraft Configuration with Aft-Propulsion Using Boundary Layer Ingestion

“…The circuit breakers are projected to an efficiency level of 99.5% with a near specific power of 200 kW/kg [35]. The specific heat rejection capacity in the thermal management system was found to vary widely in the literature: In the range between 0.68 kW/ kg [35] and 1.5 kW/kg [36]. Details on the performance parameters and weight estimation as being used in the next chapter are presented in Table A3 in Appendix A.…”