Development of a Control Oriented Scramjet Engine Inlet Model

Controller design for a realistic scramjet (Supersonic Combustion Ramjet) model is an extremely computationally intense process. To mimic the real-time scramjet performance, several researchers have developed linear models, nonlinear models, computational fluid dynamic (CFD) based models, etc. The linear models or nonlinear models based on ordinary differential equations are not sufficient to capture the complete dynamics of the scramjet; whereas CFD based models are highly computationally intense - which may vary from hours to days to complete one full closed-loop simulation of a realistic test case. The scramjet engine model can be divided in to three parts; inlet, combustor and exhaust. In this paper, the key focus is to develop the inlet model from the CFD simulations for various test cases and then capture vital scramjet engine parameters, which are later required for controller design for the scramjet engine. The models developed from the captured vital scramjet parameters has two advantages; high fidelity model and are less computationally intensive. The simulations are performed for various test cases at operating Mach numbers of 7, 6.5 and 6, angle of attack of 0 deg, ±1 deg, and ±2 deg, and various cowl angles. Control oriented polynomial inlet models are developed from the CFD data for all the operating points, the accuracy of the developed polynomial models is observed in terms of low residual errors.