Computational Fluid Dynamics-Based Analysis of Boundary Layer Ingesting Propulsion

A computational fluid dynamics-based analysis has been performed to assess propulsive efficiency benefits of a boundary layer ingesting propulsion system. This analysis is based on a full-scale configuration at relevant flight conditions defined in previous vehicle-level system studies and component designs and includes the full propulsor geometry. A method to calculate the net thrust, equivalent power, and propulsive efficiency of boundary layer ingesting propulsion systems is presented and applied to the computational fluid dynamics solutions. It was found that the boundary layer ingesting system results in a propulsive efficiency benefit of 4.2–4.5% over that of a conventional propulsion system for the case of a fan designed primarily for aerodynamic performance. These results compare favorably to those predicted by engine cycle-based system studies and boundary layer ingesting theory and do not account for anticipated additional nacelle drag reduction benefits. It is recognized that future design work will be required to impart aeromechanics capability to the fan, and thus that the subject results provide an estimate of the upper benefit bound for a full-scale boundary layer ingesting propulsor in a relevant environment.