Acoustic Effects of Porous Inert Media on Lean Premixed Combustion at Elevated Pressures

Abstract

Swirl-stabilized, lean-premixed (LPM) combustion is one method for producing relatively clean flames; however, these systems generate acoustic instabilities when operating at typical gas turbine flow, temperature, and pressure conditions. In this study, the concept of swirl-stabilization is combined with that of porous inert medium (PIM) stabilization such that the porous insert serves as a passive control device to suppress combustion instabilities and noise in the LPM combustor. The diffuser-shaped annular ring of PIM is placed at the combustor inlet where it directly influences the turbulent flow field and vortical and/or shear layer structures. Combustion experiments were conducted at several elevated pressures using SiC/HfC coated, high-strength, high-temperature resistant open-cell foam materials. Measurements of sound pressure level (SPL) were taken for different equivalence ratios and reactant flow rates. Experiments show that the porous insert can mitigate combustion instabilities and noise encountered at high pressures and reactant flow rates.