Residence Time Measurement in a Swirl Type Combustor with Helium Tracer

Abstract

Residence time measurements were carried out in a recirculation zone of a swirl type combustor. Helium gas was mixed as a tracer into combustion air and residence time distribution in the recirculation zone was determined by measuring an attenuation curve of the helium concentration with time after cutting off the mixing of the helium. The residence time was not affected by the swirl number, as long as the recirculation zone was tightly formed by the swirling flow. The residence time in a hot state (with flame) was shorter than a cold state (without flame). Further, in the analysis of the attenuation curve of the tracer, a simple modular model was used to obtain a flow rate of a reverse flow in the recirculation zone. Then, it was concluded that the flow rate of the reverse flow in the hot state was smaller than the cold state.