Mach 4 Performance of a Fixed-Geometry Hypersonic Inlet with Rectangular-to-Elliptical Shape Transition
Wind-tunnel testing of a hypersonic inlet with rectangular-to-elliptical shape transition has been conducted at Mach 4.0. These tests were performed to investigate the starting and back-pressure limits of this fixed-geometry inlet at conditions well below the Mach 5.7 design point. Results showed that the inlet required side spillage holes in order to self-start at Mach 4.0. Once started, the inlet generated a compression ratio of 12.6, captured almost 80% of available air and withstood a back-pressure ratio of 30.3 relative to tunnel static pressure. The spillage penalty for self-starting was estimated to be 4% of available air. These experimental results, along with previous experimental results at Mach 6.2 (Smart, M.K, “Experimental Testing of a Hypersonic Inlet with Rectangular-to-Elliptical Shape Transition”, Journal of Propulsion and Power, Vol. 17, No. 2, pp 276-283, 2001)indicate that fixed-geometry inlets with rectangular-toelliptical shape transition are a viable configuration for airframe-integrated scramjets that operate over a significant Mach number range.
Hypersonic Inlet for a Laser Powered Propulsion System
Propulsion within the lightcraft concept is produced via laser induced detonation of an incoming hypersonic air stream. This process requires suitable engine configurations that offer good performance over all flight speeds and angles of attack to ensure the required thrust is maintained. Stream traced hypersonic inlets have demonstrated the required performance in conventional hydrocarbon fuelled scramjet engines, and has been applied to the laser powered lightcraft vehicle. This paper will outline the current methodology employed in the inlet design, with a particular focus on the performance of the lightcraft inlet at angles of attack. Fully three‐dimensional turbulent computational fluid dynamics simulations have been performed on a variety of inlet configurations. The performance of the lightcraft inlets have been evaluated at differing angles of attack. An idealized laser detonation simulation has also been performed to validate that the lightcraft inlet does not unstart during the laser powered propulsion cycle.
Combustion Processes in Supersonic Flow
Three general classes of models that describe the processes occurring in diabatic flow in ducts having supersonic entry conditions are discussed. They are: integral techniques, finite-difference methods, and exact two-dimensional planar flame models formulated on the basis of instantaneous heat release. All three methods rigorously satisfy the conservation equations. The first two methods provide a basis for predicting and analyzing supersonic combustor performance. The careful interpretation and judicious use of experimental observations are crucial for the successful application of these methods. Comparisons of analytical and experimental results are presented, and generalized parametric studies are included. The third method is based on an idealized mixing and combustion model that may not be achievable, but nonetheless serves as a valuable analytical tool for explaining complex processes involving shock waves and heat addition. Results from four types of flow structures are discussed. Nomenclature A = cross-sectional area Af = projected area of inlet Aw = wall area