Inviscid design of the inlet for the LAPCAT Mach 8 configuration

Abstract

The air inlet for the airbreathing propulsion system of the LAPCAT Mach 8 vehicle has been designed in accordance to geometric constraints and to requirements to the flow stemming from the combustion chamber. The design tools included in-house tools featuring one dimensional gas dynamic analysis, method of characteristics (MOC) and computational fluid dynamics (CFD). The resulting inlet, dubbed LC01k, consists of two external compression ramps and a cowl that causes two internal compression shocks. The flow at the inlet exit is aligned with the free stream. The LC01k features amixed bleed/diverter channel at the end of the second external compression ramp, which mainly serves two purposes. First, the bleed channel allows a "fresh" boundary layer to develop behind the expansion corner, and second the bleed channel controls the separation of the boundary layer upstream of the expansion corner. At the design point the inlet performance fulfils (or exceeds) all flow requirements, i.e. mass flow, static temperature and static pressure. At lower Mach numbers the static temperature required for combustion is no longer reached due to the much lower total temperature of the flow.