The design of optimized 3D tip-to-tail scramjet engines

Worldwide, significant research efforts are in progress towards the development of scramjet engines. These efforts are primarily focused on the integration of the scramjet to either 'a blended body' or 'a waverider derived' hypersonic vehicle configurations; one of which may become the candidate for the first access to space air vehicle. The design of the scramjet is a complicated process due to many technical constraints, such as, aerothermodynamics, materials and mechanical. Examples of aerodynamic constraints include inlet-unstarts, mass capture, isolator characteristics, boundary layer separation, and constraints on combustor entrance flow profiles and operating temperatures. Examples of mechanical constraints include variable geometry flexibility and cooling system limits. All in all, the design of the scramjet is influenced greatly by its flight constraints. If the flight conditions were fixed, then the scramjet design problem became deterministic. As such, with a few assumptions, the engine configuration that will produce minimum drag and maximum thrust may be determined directly. However, the design problem under consideration for many practical applications requires extensive variability in altitude and Mach number, and as such, its solution can only be obtained through an optimization process. Additionally, this analysis assumed that the scramjet powered vehicle or missile is launched with an external propulsion source to some 'pre-determined' Mach number and altitude. At that point, the scramjet engine is started and propels the system until freestream flight conditions once again preclude further operation of the engine. The research efforts described in this paper focused on the design of an optimized scramjet configurations that are decouple for the hypersonic vehicle. Efforts are focused on the derivation of efficient compression forebodies, isolators, combustion chambers, and nozzle after-bodies and their integration into optimized scramjet configurations.