Investigation of Boundary Layer Ingestion technology for small commuter hybrid-electric aircraft
Title: Investigation of Boundary Layer Ingestion technology for small commuter hybrid-electric aircraft
SNIC Project: SNIC 2021/22-69
Project Type: SNIC Small Compute
Principal Investigator: Dimitra Eirini Diamantidou <dimitra.eirini.diamantidou@mdh.se>
Affiliation: Mälardalens högskola
Duration: 2021-02-05 – 2022-03-01
Classification: 20304
Keywords:

Abstract

Minimizing aviation fuel consumption has been one of the key objectives in optimizing aircraft design and air transportation and it is driven by both environmental and economic considerations. One of the concepts that are gaining increasing attention is the Boundary Layer Ingestion (BLI) which is based on the principle of placing a propulsor inside the boundary layer generated at the aircraft surface as opposed to the conventional designs where the engines are typically placed away from the aircraft’s body to avoid aerodynamic interference. The BLI concepts are targeting in ingesting part of the drag generated of the aircraft’s body, thus, reducing of wasted kinetic energy in the aircraft’s wake. However, this concept results in a tightly integrated propulsion system in which the conventional definition of thrust and drag as separate forces becomes invalid. Placing the propulsor in the boundary layer generated on the fuselage alters the surface forces on the airframe. Instead of using the conventional thrust and drag forces, the BLI concept requires to introduce another metric, the Net Propulsive Force (NPF) naming the net force required to keep the aircraft in motion. The NPF is a figure of merit that accounts for the skin friction drag, the pressure drag, the ingested boundary layer and the additional nacelle drag introduced by the BLI propulsor. The investigation of this novel airframe concept leads to many unexplored aerodynamic interaction effects for which empirical/experimental data may are not available. The evaluation of the concept is based on the accurate estimation of the boundary layer along the airframe surface for the calculation of the NPF. Therefore, higher fidelity models, such as Computational Fluid Dynamics (CFD) simulations, must be employed. The initial CFD cases will be based on a 2D model of the fuselage along with the BLI propulsor. Several geometrical and operational parameters are going to be tested. The geometrical parameters are related to the fuselage shape, BLI propulsor size and position. On the other hand, operational parameters include the flight speed and altitude which affect the corresponding freestream Reynolds number. A Design of Experiment (DOE) of different cases will be generated using the Latin Hypercube sampling (LHS) method. Initial mesh generation process, using the condition y+<1, showed that the mesh size will consist of approximately 2 million cells. For the simulations, the OpenFOAM v7 or v2006 with the simpleFoam solver is intended to be used. The decomposition of the mesh will be required. A study based on the number of processors used will be conducted to ensure fast simulation times. Finally, a grid independence study will take place to determine the ‘correct’ mesh size selected in the numerical simulations. Therefore, an estimation of the total core hours for the purposes of this work is approximately 5000 core-hours/month after conducting tests on a local machine.