TBCC hypersonic performance: Effect of inlet entropy

In this paper, focus is posed on the hypersonic airbreathing vehicles propulsion system and in particular on the scramjet module sizing: the vehicle undersurface geometry, the engine flow path and performance are performed. This work is carried out within the LAPCAT 2 European project, whose mission requirements are: 300 passengers, 18,728 km of range, un-refueled, Mach 8 as nominal speed at cruise, hydrogen as fuel and an airbreathing propulsion system. Given the large impact of the fuel weight and volume on total vehicle size, the propulsion system is a critical point to define a successfully vehicle configuration. In fact, past studies showed that as the speed increases, the propulsion system becomes a critical point to be properly addressed to get a successful configuration. In particular, in order to obtain a optimum configuration, a fully integrated vehicle has to be defined; at higher and higher flight Mach number, differences between propulsion system and aerodynamic airframe become less and less significant and the lifting body becomes the propulsion system. This means that once defined a configurations space solution that meets mission requirements, the propulsion system must be integrated within the vehicle: i.e., the inlet and nozzle of the engine must be as long as the vehicle and the length of the vehicle is defined by the propulsion system. In fact, the entire undersurface of the vehicle is part of the propulsion system: thus, the vehicle forebody has been designed to increase the pressure before entering the engine, and the aft portion of the vehicle has been designed to promote expansion of the combustion products. The forebody geometry is designed in order to have lower entropy increase still keeping a higher pressure recovery. Copyright © 2009 by A.ingenito and C. Bruno.