Valveless pulsejet engines are viable propulsion devices for MAVs. Since no accepted design methodologies are available for such propulsors, except for empirical rules, it is essential that a deep knowledge of the complex flow phenomena within such engines is gathered so as to evolve sound designs. An experimental study has been carried out to understand the unsteady acoustically coupled combusting flow phenomena in a hydrogen fuelled inline intake miniature valveless pulsejet engine. The engine chosen for the experiment was a 2D model which was little more than pen size. A novel way of allowing optical access in constructing a 2D valveless pulsejet by sandwiching three metal plates of predesigned shape in-between the two quartz glass panes was adopted. The model was fabricated in such a way that Schlieren / shadowgraph high-speed visualisation could be employed in capturing the unsteady flow structures of the complete engine including the regions around the intake and the exhaust. The unsteady acoustically coupled combustion and flow fields at the intake and the exhaust and inside the engine were simultaneously captured by using a FASTCAM PHOTRON SA4 monochrome high-speed camera. Time resolved shadowgraph images revealed that coupled flow structures at the inlet, within the combustion chamber and the tail pipe were essential for the stable operation of the pulsejet engine.
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