Studies on the Resonant, Combusting Flow Phenomena in a Small-Scale Quartz Glass Valveless Pulsejet Engine by High-Speed Flame Imaging using Chemical Tracers

The pulsejet, as a small-scale propulsion module, has great potential, and finds many applications, particularly in micro air vehicles. The valveless pulsejet engine has no moving parts and so has many attributes for scaling down for such applications. Presently, the design of a pulsejet is carried out by empirical methods in the absence of accurate physics-based prediction models. Evolving a design methodology calls for a clear understanding of the complex resonant combusting flow. Optimization of the critical parts such as the inlet aerodynamic valve, combustion chamber and exhaust pipe calls for a clear understanding of the coupled flow structures and movement of the flame front inside the pulsejet engine. Hence, an experimental study using high-speed imaging, of the internal operation of an ingeniously constructed fully transparent inline intake quartz glass valveless pulsejet engine has been carried out. Using a fully transparent engine and by capturing the complex coupled flame and flow structures has resulted in a better understanding of the flow physics of resonant combustion inside a pulsejet engine. The transparent quartz glass valveless pulsejet engine has been specially designed and fabricated and successfully test run with hydrogen as the fuel to observe the unsteady flame front movement. Since a hydrogen flame is non-luminous, chemical tracers were specially developed to enhance the luminosity of the hydrogen flame and thus improve its visibility in order to track the movement of the heat release zones. The non-intrusive flame imaging technique developed has been successfully demonstrated in capturing the resonant, combusting flow field in an inline intake valveless pulsejet engine