Approach to Modeling Boundary Layer Ingestion using a Fully Coupled Propulsion-RANS Model

Abstract

Airframe-propulsion integration concepts that use boundary layer ingestion have the potential to reduce aircraft fuel burn. One concept that has been recently explored is NASA's Starc-ABL aircraft configuration, which offers the potential for 12% mission fuel burn reduction by using a turbo-electric propulsion system with an aft-mounted electrically driven boundary layer ingestion propulsor. This large potential for improved performance motivates a more detailed study of the boundary layer ingestion propulsor design, but to date, analyses of boundary layer ingestion have used uncoupled methods. These methods account for only aerodynamic effects on the propulsion system or propulsion system effects on the aerodynamics, but not both simultaneously. This work presents a new approach for building fully coupled propulsive-aerodynamic models of boundary layer ingestion propulsion systems. A 1D thermodynamic cycle analysis is coupled to a RANS simulation to model the Starc-ABL aft propulsor at a cruise condition and the effects variation in propulsor design on performance are examined. The results indicates that both propulsion and aerodynamic effects contribute equally toward the overall performance and that the fully coupled model yields substantially different results compared to uncoupled. The most significant finding is that boundary layer ingestion, while offering substantial fuel burn savings, introduces throttle dependent aerodynamics effects that need to be accounted for. This work represents a first step toward the multidisciplinary design optimization of boundary layer ingestion propulsion systems.

Performance bookkeeping for aircraft configurations with fuselage wake-filling propulsion integration

“…Drag and thrust were calculated as net forces integrated over aircraft and propulsion system surfaces, respectively. The overall net force in axial direction was determined as the sum of the integrated pressure and viscous forces over all body surfaces and the pressure and momentum flux contributions on the fan face and fan exit [65][66][67][68]. In a similar manner, Ordaz et al carried out an adjoint-based numerical design and optimization of BLI concepts (NASA STARC-ABL and MTA450-business jet with aft fan) with the objective of minimized flow distortion at the propulsor [69,70].…”

Modeling hybrid polymer–nanometal lightweight structures

“…In the aerodynamics field, dramatically increased use of aerodynamic shape optimization [15] and the use of unconventional aircraft configurations, such as blended wing bodies [16], will be essential. With respect to propulsion, open rotor engines [3] or boundary-layer ingestion [10] is promising options that significantly increase fuel efficiency. Electric propulsion [6], which may be distributed [5], is also attractive options.…”

Simultaneous Propulsion System and Trajectory Optimization

“…8 Boundary layer ingestion and distributed propulsion systems introduce strong propulsion-aerodynamic coupling that motivates a more coupled modeling approach. 9 Hybrid electric propulsion systems, in addition to potential propulsion-aerodynamic coupling, can also introduce a strong coupling to the trajectory analysis as well. This coupling occurs as power split between the gas and electric power sources must be scheduled throughout a mission and the schedule has a strong impact on the overall design of the propulsion system.…”