The energy management strategy of a hybrid-electric aircraft is coupled with the design of the propulsion system itself. A new design space exploration methodology based on Set-Based Design is introduced to analyse the effects of different strategies on the fuel consumption, ${\mathrm{NO}}_{\mathrm{x}}$ and take-off mass. Probabilities are used to evaluate and discard areas of the design space not capable of satisfying the constraints and requirements, saving computational time corresponding to an average of 75%. The study is carried on a 50-seater regional turboprop with a parallel hybrid-electric architecture. The strategies are modelled as piecewise linear functions of the degree of hybridisation and are applied to different mission phases to explore how the strategy complexity and the number of hybridised segments can influence the behaviour of the system. The results indicate that the complexity of the parametrisation does not affect the trade-off between fuel consumption and ${\mathrm{NO}}_{\mathrm{x}}$ emissions. On the contrary, a significant trade-off is identified on which phases are hybridised. That is, the least fuel consumption is obtained only by hybridising the longest mission phase, while less ${\mathrm{NO}}_{\mathrm{x}}$ emissions are generated if more phases are hybridised. Finally, the maximum take-off mass was investigated as a parameter, and the impact to the trade-off between the objectives was analysed. Three energy management strategies were suggested from these findings, which achieved a reduction to the fuel consumption of up to 10% and a reduction to ${\mathrm{NO}}_{\mathrm{x}}$ emissions of up to 15%.

Propeller performance is traditionally represented by a performance map that gives propeller efficiency as a function of the flight Mach number, the power coefficient $C_P$, and the advance ratio $J$. This work aims to demonstrate how this map changes when the design $C_P$ and $J$ change and to propose a novel map format that is able to capture the performance of different propeller designs. For this purpose, the propeller performance is simulated using a propeller lifting-line method validated for the SR3 propfan. Subsequently, the propeller model is used within a sequential quadratic programming framework to optimize the blade twist and chord distribution for different sets of design $C_P$ and $J$. A complete propeller performance map is then generated for each one of the optimized designs. The results demonstrate that all the investigated propellers can be modeled by a common map, which determines separately the ideal efficiency and the viscous losses. The ideal efficiency is given in the traditional format of ${\eta }_i=f(C_P,J)$, whereas the viscous losses are represented as a function of the relative variables $C_P/C_{P\mathrm{des}}$ and $J/J_{\mathrm{des}}$.

Engine maintenance costs for civil aircraft largely depend on the life consumption of critical parts like high-pressure turbine blade and disk. Severity (defined as a measure of relative damage) can be used to characterize the degree of life consumption for the parts subjected to low cycle fatigue, creep, and oxidation as predominant life-limiting modes under normal engine operation. In this context, a numerical tool has been developed to study the impact of engine-aircraft operational parameters on engine severity. This is accomplished by combining aircraft performance, gas turbine performance, component sizing, heat transfer calculation, thermal analysis, structural analysis, life and severity estimation for the high-pressure turbine, and the disk components of jet engines. Operational parameters such as take-off (TO) derate, climb derate, outside air temperature, and airport altitude have been studied for lower thrust and larger thrust engines. The observations from the study show that TO derate and outside air temperature are dominant parameters in terms of engine severity. The use of climb derate also lowers the severity and is more beneficial for larger thrust engines, while airport altitude effects could be minimized by the use of suitable TO derate. The severity characteristics estimated through the numerical tool can provide an enhanced perspective on aircraft engine maintenance.

Conventional propulsion systems are typically represented as uninstalled systems to suit the simple separation between airframe and engine in a podded configuration. However, boundary layer ingesting systems are inherently integrated, and require a different perspective for performance analysis. Simulations of boundary layer ingesting propulsions systems must represent the change in inlet flow characteristics, which result from different local flow conditions. In addition, a suitable accounting system is required to split the airframe forces from the propulsion system forces. The research assesses the performance of a conceptual vehicle, which applies a boundary layer ingesting propulsion system—NASA's N3-X blended wing body aircraft—as a case study. The performance of the aircraft's distributed propulsor array is assessed using a performance method, which accounts for installation terms resulting from the boundary layer ingesting nature of the system. A “thrust split” option is considered, which splits the source of thrust between the aircraft's main turbojet engines and the distributed propulsor array. An optimum thrust split (TS) for a specific fuel consumption at design point (DP) is found to occur for a TS value of 94.1%. In comparison, the optimum TS with respect to fuel consumption for the design 7500 nmi mission is found to be 93.6%, leading to a 1.5% fuel saving for the configuration considered.