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Parametric study of aerodynamic integration issues in highly coupled blended wing body configurations implemented in UAVs

Abstract:

The numerous applications of unmanned aerial vehicles (UAV’s) flying at low speeds for monitoring purposes in the Andean region have motivated the investigation and evaluation of more effcient concepts, in order to enhance their payload and range. In this context, alternative propulsion concepts that present higher synergy with electrical systems have been studied. In a previous work, a preliminary configuration with distributed propulsion using a blended wing body (BWB) aircraft was assessed using a parametric analysis and intake pressure losses were identified as main aerodynamic integration issue. This work aims to refine the model developed previously for distributed propulsion performance assessment using different approaches to model intake pressure losses. For this purpose, semi-empirical correlations for incompressible flow accounting for duct geometry and flow characteristics were utilized. Furthermore, the suitability of implementing boundary layer ingestion (BLI) with thrust split in distributed propulsion configurations has been evaluated. The case of study takes place in the Andean region and hence the cruise altitude for the study has been set at 3000 m above sea level. Results show that intake losses are small and do not overweight BLI benefits, however BLI induced distortion affects largely this latter, specially for high fan pressure ratios. Furthermore, the suitability and design space of BLI and thrust split were determined. From this analysis for the best case scenarios improvements of around 9 % in propulsive effciency and a reduction in power consumption of 19 % due to BLI implementation were found. Finally, a weight analysis shows that thrust split for non homogeneous propulsion configurations does not exhibit benefits in terms of weight reduction.