Assessment of Aircraft Surface Heat Exchanger Potential

Providing sufficient cooling power for an aircraft will become increasingly challenging with the introduction of (hybrid-) electric propulsion. To avoid excessive drag from heat exchangers, the heat sink potential of the aircraft surface is evaluated in this study. Semi-empirical correlations are used to estimate aircraft surface area and heat transfer. The impact of surface heating on aircraft drag is qualitatively assessed. Locating surface heat exchangers where fully turbulent flow is present promises a decrease in aircraft drag. Surface cooling potential is investigated over a range from small regional aircraft to large wide body jets and a range of surface temperatures. Four mission points are considered: Take-off, hot day take-off, climb and cruise. The results show that surface heat exchangers can provide cooling power in the same order of magnitude as the waste heat expected from (hybrid-) electric drive trains for all sizes of considered aircraft. Also, a clear trend favouring smaller aircraft with regards to the ratio of available to required cooling power is visible

Optimality considerations for propulsive fuselage power savings

The paper discusses optimality constellations for the design of boundary layer ingesting propulsive fuselage concept aircraft under special consideration of different fuselage fan power train options. Therefore, a rigorous methodical approach for the evaluation of the power saving potentials of propulsive fuselage concept aircraft configurations is provided. Analytical formulation for the power-saving coefficient metric is introduced, and, the classic Breguet–Coffin range equation is extended for the analytical assessment of boundary layer ingesting aircraft fuel burn. The analytical formulation is applied to the identification of optimum propulsive fuselage concept power savings together with computational fluid dynamics numerical results of refined and optimised 2D aero-shapings of the bare propulsive fuselage concept configuration, i.e. fuselage body including the aft–fuselage boundary layer ingesting propulsive device, obtained during the European Union-funded DisPURSAL and CENTRELINE projects. A common heuristic for the boundary layer ingesting efficiency factor is derived from the best aero-shaping cases of both projects. Based thereon, propulsive fuselage concept aircraft design optimality is parametrically analysed against variations in fuselage fan power train efficiency, systems weight impact and fuselage-to-overall aircraft drag ratio in cruise. Optimum power split ratios between the fuselage fan and the underwing main fans are identified. The paper introduces and discusses all assumptions necessary in order to apply the presented evaluation approach. This includes an in-depth explanation of the adopted system efficiency definitions and drag/thrust bookkeeping standards.Flight Performance and Propulsio

Study of a Regional Turboprop Aircraft with Electrically Assisted Turboshaft

Hybrid-Electric Propulsion (HEP) could be part of the solution to decrease emissions associated with regional commercial aviation. This study presents results for the aircraft level fuel reduction potential of a regional turboprop concept with an HEP architecture and Entry-Into-Service (EIS) in 2035+. The configuration specifically tackles the elaborated challenges of introducing an additional electrical energy source to the configuration by employing a twofold electrical assistance to a turboshaft engine in combination with an innovative thermal management concept. Relevant components and disciplines were modeled and incorporated into an integrated aircraft design environment. The behavior and interaction of the HEP architecture with the aircraft was thoroughly investigated. A best-performing configuration was derived and compared with a conventional reference configuration following a State-of-the-Art (SoA) reference aircraft approach. For a typical mission with 200 nmi range, a block fuel reduction of 9.6% was found. However, the assumed battery performance characteristics limited the reduction potential and led to a fuel burn increase for the 600 nmi design mission. Furthermore, sourcing the non-propulsive subsystems directly from the on-board battery was detrimental. The innovative Thermal Management System (TMS) located in the propeller slipstream showed a synergistic effect with the investigated configuration

Proof of concept study for fuselage boundary layer ingesting propulsion

Key results from the EU H2020 project CENTRELINE are presented. The research activities undertaken to demonstrate the proof of concept (technology readiness level-TRL 3) for the so-called propulsive fuselage concept (PFC) for fuselage wake-filling propulsion integration are discussed. The technology application case in the wide-body market segment is motivated. The developed performance bookkeeping scheme for fuselage boundary layer ingestion (BLI) propulsion integration is reviewed. The results of the 2D aerodynamic shape optimization for the bare PFC configuration are presented. Key findings from the high-fidelity aero-numerical simulation and aerodynamic validation testing, i.e., the overall aircraft wind tunnel and the BLI fan rig test campaigns, are discussed. The design results for the architectural concept, systems integration and electric machinery pre-design for the fuselage fan turbo-electric power train are summarized. The design and performance implications on the main power plants are analyzed. Conceptual design solutions for the mechanical and aerostructural integration of the BLI propulsive device are introduced. Key heuristics deduced for PFC conceptual aircraft design are presented. Assessments of fuel burn, NOx emissions, and noise are presented for the PFC aircraft and benchmarked against advanced conventional technology for an entry-into-service in 2035. The PFC design mission fuel benefit based on 2D optimized PFC aero-shaping is 4.7%.Flight Performance and Propulsio