A modelling approach of Boundary Layer Ingesting (BLI) propulsion systems is presented. Initially, a distorted compressor model is created utilizing the parallel compressor theory to estimate the impact of inlet distortion on fan performance. Next, a BLI propulsor model is developed considering both distortion effects and reduced inlet momentum drag caused from boundary layer ingestion. Finally, a Turbo-electric Distributed Propulsion (TeDP) model is set up, consisting of the BLI propulsor model, the associated turboshaft engine model and a representation of the relevant electrical system. Each model is validated through comparison with numerical and/or experimental data.
A design point calculation is carried out initially to establish propulsor key dimensions for a specified number of propulsors and assuming common inlet conditions. Parametric design point analyses are then carried out to study the influence of propulsors number and location under different inlet conditions, by varying fan design pressure ratio between 1.15 and 1.5. BLI and non BLI configurations are compared at propulsion system level to assess the BLI benefits. The results show that maximum BLI gains of 9.3% in TSFC and 4.7% in propulsive efficiency can be achieved with 16 propulsors and FPR = 1.5, compared to podded propulsors, while further benefits can be achieved by moving the propulsor array backwards in the airframe.