Modeling and simulation of RBCC engine cycle

Rocket-based combined-cycle engine combine the most desirable characteristics of airbreathing engines and rockets into a single, integrated engine, which could be used as potential propulsion system for aerospace plane. Along a typical SSTO ascent trajectory a RBCC engine operates in five modes: ducted rocket, ramjet, scramjet, scramjet/rocket, and pure rocket outside the atmosphere. Different engine cycle are needed for various engine operating modes, include propellant and oxygen feed systems. Modeling and simulation of a RBCC engine cycle were undertaken considering smooth transitions between these modes. RBCC engines use liquid hydrogen as fuel to propel the aerospace plane ascends in atmosphere. When outside the atmosphere, liquid oxygen and hydrogen are feed into pure rocket which push the vehicle insert orbit. During the ducted rocket mode, the engine's fuel side is powered by a fuel-rich gas generator. The oxygen side is powered by an oxidizer-rich staged combustion cycle. During pure airbreathing modes, the engine's entire oxygen feed system is inactive. The fuel side operates in a expander cycle mode using heat available from required cooling of the engine structure. In the Scramjet/Rocket mode the fuel remains operating in the expander cycle and the oxidized is restarted in the stage combustion cycle. A reference aerospace plane was selected to provide air flow flux enter RBCC engine for calculating fuel flow flux. Fuel/oxygen turbopumps, fuel-rich gas generator, oxygen-rich preburner, and pipes were modeled. Fule and oxygen turbopump should satisfy requirements of flow mass flux for each mode, thus ducted rocket mode which have bigger combustor pressure and flow mass flux were choice as design conditions. Balance equations of mass flux, pressure and power were built to determine parameters of each part, include flow mass flux, power, and pressure ratios of turbopumps, etc. Some advices were given to engine cycle according simulation results. In pure rocket mode, fuel turbopump should be driven by gas generated by oxygen-rich preburner instead of expander cycle. Fuel-rich gas generator only operate in ducted rocket mode, thus could be removed replaced with oxygen-rich preburner gas drive fuel and oxygen turbopumps together. Improved engine cycle can satisfy various engine operating modes and reduces mass of engine cycle system.