AbstractsEngineering

Boundary Layer Ingestion (BLI) is a concept in which the fuselage boundary layer is ingested by the engine to produce benefits like improved fuel efficiency, reduction of ram drag and lower structural weight of the configuration. Blended Wing Body (BWB) concept has been researched on and studied in various forms over the years as an efficient alternative to the conventional transport configurations. Past studies have concluded that of the podded and embedded engine configurations, the BWB architecture is particularly suited to flush mounted embedded engines, as the balance requirements already place them near the aft of the airframe. Despite the benefits, effect of BLI on engine performance is also known to be detrimental because BLI increases pressure distortion and reduces total pressure recovery at the engine fan face. Most of these drawbacks are caused by secondary flow losses (vortices created due to boundary layer separation) due to an adverse pressure gradient in the S-Duct and a non-uniform mass flow ratio. An improved inlet design becomes necessary to reduce these limitations. The aim of this research is to design an inlet embedded on a BWB that ingests significant amount of fuselage boundary layer and produces minimum pressure loss and distortion in the process. Two major consequences of BLI are vital in this regard namely, loss of total pressure recovery and increased total pressure distortion at the Aerodynamic Interface Plane (AIP) or the engine fan-face. Hence the inlet performance is measured by the total Pressure Recovery Factor (PRF) and Distortion Coefficient (DC60). Therefore, this research work aims to design an embedded inlet on a BWB that produces maximum value of PRF and minimum DC60. An extensive literature study was carried out in order to understand the effects of BLI on inlet performance and research work conducted in the past to minimize the losses associated with BLI. Many of these studies focus on S-Ducts ingesting boundary layer and minimization of the losses using flow control techniques. Few studies have focussed on design of a novel inlet configuration that produces best results in terms of PRF and DC60. This thesis has focussed on the design of the inlet based on computational analysis of different inlet configurations to achieve an optimum design. The framework of this report first follows description of criteria and parameters for embedded inlet design. This is followed by an elaboration on the numerical methodology and approach to be used for the Computational Fluid Dynamics (CFD) simulations. The CFD simulations and analyses conducted in this thesis are divided into 2 main stages. The first stage deals with the computational analysis of a BWB in clean configuration (without engines) to obtain velocity profiles over aft fuselage, where the inlets will be embedded. The second stage comprises of the main inlet design. Three main geometrical parameters are chosen for the geometrical design of the inlet, namely inlet aspect ratio (ratio of inlet ellipse major axis length and…