Experimental Study of Boundary-Layer Ingestion into a Diverterless S-Duct Intake

Abstract

AN INGESTION of fluid of reduced velocity like that of wake flows and boundary layers can increase the efficiency of engines [1,2]. This is exploited with torpedoes, where the propulsion system is usually placed in the wake of the body. Recent studies [3–6] have shown that benefits resulting from an ingestion of boundary layers are also possible in the case of blended-wing bodies, with the distortion of the flow and reduced stagnation pressures at the engine face being the main problem. The topic of this Note is a parametric study of the combined effect on flowconditions at the engine face of boundary-layer ingestion into intakes and an S-duct diffuser. Previous studies used boundary layers formed on the walls of a wind tunnel [7]. In this study, a boundary layer of well-defined thickness is formed on a flat plate within the wind tunnel. The intake is placed at a certain distance from the leading edge of the plate. By changing the length of the plate, the boundary-layer thickness can be varied independently of other flow properties. Intake performance is assessed based on circumferential distortions and losses in total pressure at the aerodynamic interface plane (AIP). Experiments were performed in the cryogenic blowdown tunnel–Göttingen (DNW-KRG) of the German–Dutch Wind Tunnels. Impulse facilities like the DNW-KRG are well suited for intake tests. For example, air intake studies have been successfully performed in a light piston tunnel for which the test time is on the order of 1 s, similar to that of the DNW-KRG [8]. The blowdown tunnel DNW-KRG allows the variation of the Reynolds and Mach numbers, as well as boundary-layer thickness and mass flux through the intake independent of each other.