A Preliminary Investigation of the Secondary Flame and Operational Properties of an Actively-valved Pulse Jet

Due to their complex nature, a clear and comprehensive understanding of the mechanisms driving the combustion dynamics of pulse jets is not yet available. The present work intends to fill this gap by shedding some light on general operational properties of an active valve resonant pulse combustor as well as fundamental mechanisms. Pressure sensors and ion probes were used to quantify the global performance of the pulse combustor in naturallyaspirated mode or for different forced air flow-rates. It was shown that performance, here indicated by the pressure gain, improves when the forced air flow-rate increases. For a subset of operating conditions, infrared and thermocouple thermometry was used to measure side wall temperatures. Gas sampling was also used to infer species concentrations inside the combustor and along its main axis. These measurements highlighted the presence of a secondary flame located in the tail pipe, near the exhaust. A possible mechanism responsible for this secondary flame was proposed.