Control-Oriented Study On One-Dimensional Modeling For Scramjet Engine

Scramjet (Supersonic Combustion Ramjet) is the first choice in the hypersonic flight regime, commonly considered to begin when velocities exceed Mach 6. Compared with any other conventional propulsion system, scramjet is an extremely complicated thermodynamic system. Control system of scramjet becomes the critical factor in the scramjet operation safely and economically and so the need of control-oriented model of scramjet emerged. The control-oriented one-dimensional modeling of scramjet was investigated in detail in this paper.Firstly, with the review of the development history of the scramjet concept and its modeling and control, the significance and distinctiveness of the scramjet control was obtained. The characteristic of the scramjet was studied exhaustively and it found what makes its control difficult is the distributed parameter characteristic of the scramjet. With the requirement of the control system design, the necessity of control-oriented one-dimensional modeling of the scramjet was put forward and the motivation of this study was clarified.Secondly, the flow mechanism of the scramjet inlet and combustor were analyzed carefully. According to this, the flow path of the scramjet was divided into four sections:Fanno flow, shock compression, combustion detach and combustion attach. The dominant physical effects were analyzed and which provided the basis of the one-dimension modeling of the scramjet.Then, the modeling method of the physical effects which affect the performance of the scramjet combustor was presented and the one-dimensional model of scramjet combustor was developed based on it. The model can represent the several of combustion modes of scramjet and the transform boundary of them. Finally, with the one-dimensional model of the scramjet developed above, the distributed parameter control of the scramjet was simulated. The main influence factors of the performance of scramjet, such as the condition of the free stream, the position of the fuel injection and the fuel injection distribution proportion, were studied. Control laws of equal thrust force and equal margin of inlet unstart were developed.