Passive Mitigation of Noise in a Duel Fuel Combustor Using Porous Inert Media

Abstract

In the past, we have utilized porous inert media (PIM) to suppress noise and thermo-acoustic instabilities in swirl-stabilized combustion systems operated on gaseous fuels. The same concept will also be shown to work in liquid fueled combustion systems. This study presents experimental results to evaluate the PIM concept for suppressing combustion noise in a duel fuel combustor. Experiments for gaseous fuel combustion are performed using natural gas premixed with air upstream of the combustor dump plane. Experiments for liquid fuel combustion are performed using kerosene fuel supplied through a commercial air-blast atomizer. In this combustor, the flame stabilizes downstream of the dump plane by central and corner recirculation zones. Multiple ring shape PIM pieces are inserted into the combustor to alter the flow field in an advantageous manner. Each PIM piece has the same outer diameter but different inner diameters. Results are presented to investigate the effects of equivalence ratio and heat release rate for gaseous fuel combustion and air to liquid mass ratio and heat release rate for liquid fuel combustion. Attempts were also made to create thermo-acoustic instabilities by positioning four loudspeakers radially around the primary air flow upstream of the combustor. Measurements of sound pressure levels (SPL), and CO and NOx emissions were taken to characterize the combustion process. Results show that PIM can passively mitigate combustion noise in a duel fuel combustor without adversely affecting the emissions.