Propulsion system analsysis using a parametric and the parallel compressor approach to model distortion in Boundary Layer Ingestion systems

摘要

The performance benefits of boundary layer ingestion in the case of air vehicles powered by distributed propulsors have been documented and explored extensively by numerous studies. Therefore, it is well known that increased inlet flow distortion due to boundary layer ingestion (BLI) and intake pressure losses can dramatically reduce the expected benefits. In this paper a parametric and quasi-two dimensional studies at component and at system level are carried out, such that the effects of these two aerodynamic issues over the system performance can be assessed. The figure of merit in this study is TSFC and the system parameters examined are: thrust split between propulsors and engines, capture height and core engine parameters. For the purpose of this study the N3-X NASA aircraft concept is selected as baseline configuration due to its TeDP with BLI. From preliminary analysis it is observed that ingesting BL produces drops in fan efficiency and pressure ratio in the order of 1-2% and 2-2.5% respectively, when parallel compressor method is used. Through system analysis it is observed that splitting the thrust between propulsors and core-engines could have a beneficial effect in fuel savings. Preliminary results found optimum configurations at around 60-90% thrust split ratio, when intake pressure losses of 2% were assumed for the distributed propulsors and installation effects were neglected. To summarize the key contribution of this study is the determination of the sensitivity of the propulsion system to the level of fidelity utilized to model BLI associated distortion and further highlights the importance of using alternative methods such as parallel compressor to determine the detriment in propulsor performance due to BLI.