Session: 31-06 Fan & Propulsor Design

Paper Number: 152500

Aft Fuselage Boundary Layer Ingesting Propulsion System Design 

In this paper, we present conceptual design and its performance for non-axisymmetric aft fuselage and tail-integrated distributed propulsors (DP) with boundary layer ingestion (BLI) for future turbo-electric aircraft. The idea is to design non-axisymmetric aft fuselage to induce circumferential pressure gradient to yield axial vorticity in the tail-BLI propulsor inflow. The inflow axial vorticity at the bottom of the fan annulus, in the same direction as the rotor rotation, reduces local large incidence caused by boundary layer (BL) velocity non-uniformity. The rotor incidence variation is hence reduced. A near-optimum propulsor configuration (number, size, location) is determined to take advantage of the aft fuselage design to maximize the aircraft fuel burn benefit. It is shown that rotor efficiency penalty due to inlet distortion can be eliminated without using inlet guide vanes or stator exit swirl (pressure perturbations). The assessment of BLI benefits incorporates CFD and TASOPT analyses, both to characterize the underlying mechanisms and thus establish the physical rationale for resolving these challenges.

 

The conceptual design has six tail-BLI propulsors, installed on a single-aisle mid-range aircraft with twin underwing turbofans and a T-tail. The propulsors are inclined from the aircraft longitudinal direction to reduce the tail cone size and weight. No propulsor is installed adjacent to the vertical tail because the propulsor weight penalty exceeds the propulsive improvement from ingesting the local BL kinetic energy defect. A fan pressure ratio (FPR) of 1.4 for integrated propulsors gives near-optimum aircraft fuel consumption, as a trade between the propulsor weight and the propulsive efficiency. A robust fan design achieves an overall 1.5% stage efficiency penalty with a common stator design for the six integrated propulsors. Although using stator exit swirl can improve the stage efficiency, it can cause streamwise vortices at the nozzle exit plane which increases jet dissipation. The stator exit swirl is hence not applied to the fan design.

 

The benefit of the defined tail BLI and twin underwing turbofan aircraft configuration is 8.5% in Payload Range Fuel Consumption (PRFC) at a cruise Mach number of 0.8, compared to a baseline conventional aircraft. Zero fan efficiency penalty can only increase the benefit by approximately 0.4%. The defined tail-BLI aircraft configuration is hence close to optimal in terms of fuel burn.

Presenting Author: Zhibo Chen Massachusetts Institute of Technology

Presenting Author Biography: Zhibo Chen is a Ph.D. candidate at the MIT Gas Turbine Laboratory. He received his S.M. in Aeronautics and Astronautics from MIT in 2022. Before coming to MIT, he received his B.S.E. in Aerospace Engineering from the University of Michigan and his B.S. in Mechanical Engineering from Shanghai Jiao Tong University in 2020. His research interests include turbo-electric propulsion, aerodynamics, and turbomachinery.

Authors:

Zhibo Chen Massachusetts Institute of Technology
Marshall Galbraith Massachusetts Institute of Technology
Zoltán Spakovszky Massachusetts Institute of Technology
Edward Greitzer Massachusetts Institute of Technology