Design and Optimization of a Boundary Layer Ingesting Propulsor

Pritesh Mandal

Justin Holder

Mark G. Turner

University of Cincinnati

 

Mark L. Celestina

NASA Glenn Research Center

 

            The boundary layer ingestion concept has the potential to improve propulsion efficiency that will lead to better fuel economy of commercial aircraft. This design concept has been explored by NASA as the Single-aisle Turboelectric Aircraft with Aft Boundary-Layer propulsor “STARC-ABL.” This paper discusses the 1D-3D aerodynamic design and optimization process as well as the structural analysis of the rotor of a propulsor with incoming distortion. The propulsor is at the tail of the fuselage, and consists of an Inlet Guide Vane (IGV), rotor, and Outlet Guide Vane (OGV). The design process presented accounts for only the large radial distortion and not the circumferential distortion.  The paper also describes a pragmatic way of choosing orthogonal design parameters to proceed with the optimization process using a genetic algorithm.

            The final optimized design is highly dependent on the objective function to be optimized.  A Modified Adiabatic Efficiency (MAE) has been defined to account for the loss of kinetic energy at the OGV.This lost kinetic energy is essentially an approximation of the mixing loss of the tangential, axial and radial components of velocity at the OGV exit.The threeblade-row adiabatic efficiency and MAE for an intermediate design case was 88.91% and 86.10% respectively.  Upon further optimization and a different incoming distortion, using MAE as the objective function improved the MAE to 87.63% with an 88.52% adiabatic efficiency for final design case. The rotor only adiabatic efficiency for this case is 94.19%, the IGV-Rotor two blade-row efficiency is 92.06% and the Rotor-OGV two blade-row efficiency is 90.66%. The IGV is necessary to support the nacelle in this configuration.  It also allows for the rotor work distribution to be optimized.  MAE as the objective function leads to a decrease in Kinetic Energy Variation at the OGV exit.

            The resulting rotor blade satisfies the static structural limit of a 1.1 safety factor for titanium at 110% speed. It also includes the pressure loads from the design point.  A Campbell diagram shows that key natural frequencies are avoided.  The process uses an open source parametric blade generator whose source and input files for this geometry are on GitHub.


Design and Optimization of a Boundary Layer Ingesting Propulsor

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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