Thermal management system for a hybrid-electric aircraft: parametric models for physical characterisation

The thesis focuses on the preliminary design of the Thermal Management System (TMS) for a hybrid-electric aircraft. Initially the state-of-art review is widely investigated, identifying the objective of the system as well as technologies currently available. Thus, it is demonstrated that Meredith Effect and Vapor Cycle Machine are key elements for next generation aircraft. Subsequently, case study is shown, in order to drive the TMS design towards right aims. The case study is the European funded project named HERA, which aims to develop a 80 passenger hybrid-electric aircraft. Following this chapter a preliminary analysis is led, involving analytical analysis of technologies previously identified as those with the most potential. Hence, this phase allows to ensure strong analytical basis, to size systems, while also pointing out critical points. Finally, robust and accurate parametric models are proposed, to show feasibility and to first sizing systems by means of simulations. Overall, the experimental phase is run with different software. Meredith Effect model is built in MATLAB, while Vapor Cycle Machine is simulated respectively in Simcenter Amesim and Aspen HYSYS. Considering the fuel cells heat load, the first result is Meredith Effect provides thrust level which equals cooling drag. Subsequently, the work demonstrated the unfeasibility of cooling fuel cells with a single-stage vapor compression cycle. Furthermore, Vapor Cycle Machine is studied for Environmental Control System and for Battery Thermal Management System (BTMS) purposes, applying the worst case scenario: hot day and degraded conditions. The work provides simulations of the correct vapor compression cycle in HYSYS for cabin air conditioning, thus identifying the correct refrigeration loop. Whereas BTMS is simulated in Amesim, sizing each component in great detail as well as identifying the right refrigeration loop. Results are presented both graphically, using plots and also analytically, by means of tables. To sum up, this work initially involves a deep analytical analysis that allowed to build four main parametric models concerning the TMS of a hybrid-electric aircraft. These models concern Meredith Effect and vapor compression cycle per each system, respectively for cooling fuel cell, cabin and batteries. Ultimately, some future work aspects for this thesis are discussed, outlining how the work can be carried out in the future.