Low-fidelity Aerodynamic Integration of Distributed Electric Propulsion on a Blended Wing Body including Boundary Layer Ingestion
Creators: name:  J. AALBERS 
name:   J. VAN MUIJDEN 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: HYBRID ELECTRIC PROPULSION
AVIATION
EMISSIONS

description: To meet with the demand for a reduced carbon footprint of commercial aircraft, an increasing interest has been taken by the scientific and industrial community to consider disruptive, radical new technologies and configurations[1,2]. One of the options, hybrid-electric propulsion, is currently being investigated within the European project IMOTHEP (Investigation and Maturation Of Technologies for Hybrid-Electric Propulsion) for its merits to reduce fuel consumption. Specifically, a concept that is considered within IMOTHEP is ONERAs SMILE Blended Wing Body (BWB)[3], with distributed electric propulsion. In this paper a low-fidelity methodology will be presented how to model Boundary Layer Ingestion (BLI) in conjunction with distributed propulsion, allowing for quick evaluation of a configuration. To model the boundary layer ingestion, a Parallel Compressor Method [4-6] is employed. In this method, the flow is divided in an averaged boundary layer flow and a free flow. The propulsor ingests the boundary layer stream thus reenergizing it. The proposed benefit is a reduced wake loss of the boundary layer. Contrary to classical propulsion without BLI, thrust and drag are now highly coupled. Therefore, to keep track of the thrust and drag terms a Power Balance method is employed[7,8]. The low-fidelity aero integration methodology addressed in this paper comprises the following main elements: BLI module for a single thrusters: a novel boundary layer substitution model which takes into account compressibility of the boundary layer flow. A parametric study to evaluate the power savings coefficient of a single thruster in BLI with a fixed thrust value, by means of varying the Fan Pressure Ratio. A baseline computation of the BWB SMILE configuration to compute the boundary layer and obtain the terms for induced, wave and viscous drag on the configuration without the presence of any thrusters. This is done using NLRs in-house developed flow solver MATRICS-V[9], which is a viscous-inviscid interaction solver based on full potential theory. The power balance methodology is used to supplement the baseline aerodynamic data with BLI thrusters in DEP configuration, accounting for ingested drag and adding cowling and propulsor jet losses. An iterative routine will be introduced to solve for the Power Balance Equation by varying the inlet mass flow (i.e. inlet fan area) or Pressure Ratio setting of the propulsors. Several DEP configurations, varying with the number of thrusters, location of thrusters and different flow conditions, will be evaluated and compared to podded engine configurations (i.e. no BLI applied to the thrusters). Low-fidelity analysis inevitably comes with simplifications and assumptions. For instance, the baseline flow computed by MATRICS-V never feels the presence of a propulsor, nor that there are any flow interactions among the thrusters. Additionally, the boundary layer substitution model is a significant simplification of a complex turbulent flow. Nonetheless, this methodology provides a crude estimation of the performance of BLI in conjunction with DEP. The perspective towards the near future is to synthesize the findings of the low-fidelity analysis with high-fidelity analyses, and being able to select the most suitable set-up for this type of configurations.