An Experimental Study of the Stability and Nearfield Structure of Oxyfuel Jet Flames at Elevated Pressures

This study presents experimental results of the stability limit and the nearfield structure of oxy-methane jet flames at pressures ranging from 2–5 bar. The oxidizer used in this campaign consists of 40% O2 and 60% CO2. Two sets of cases were studied: one where pressure increase was achieved by keeping the fuel Reynolds number constant and the other where the velocity was kept constant while increasing pressure. Stability limits (lift-off velocity) are reported for various coflow velocities at different operating pressures. Natural flame luminosity imaging with a DSLR camera and combined CH* chemiluminescence using an ICCD (PIMAX 4) are used to characterize the nearfield structure of the flame. The CH* results were then processed to extract the attachment location, defined in terms of attachment height and radius. The study mainly investigates the effect of pressure on the flame attachment height and radius. The DSLR images complement the study with qualitative information on the flame appearance and sooting propensity. Results show that at constant Reynolds number, the attachment height decreases with pressure for all cases considered while the attachment radius increased with pressure increase. At constant velocity, however, both the attachment height and radius were observed to decrease with increased pressure.