Time-Resolved PIV Measurements in Lean Premixed Swirl-Stabilized Combustor without and with Porous Inert Media for Acoustic Control

摘要

Combustion noise is of primary importance in highly critical applications such as rocket propulsion, power generation, and aviation. Mechanisms for combustion noise are extremely complex because they often involve interactions among several different physical phenomena such as unsteady flame propagation leading to unsteady flow field, acoustic wave propagation, natural and forced hydrodynamic instabilities, etc. In the past, we have utilized porous inert media (PIM) to mitigate combustion noise and thermo-acoustic instabilities in both lean premixed (LPM) and lean direct injection (LDI) combustion systems. While these studies demonstrated the efficacy of the PIM concept to mitigate noise and thermo-acoustic instabilities, the actual mechanisms involved have not been understood. The present study utilizes time-resolved particle image velocimetry to measure the turbulent flow field in a LPM swirl-stabilized combustor without and with PIM. Although the flow field inside the annulus of the PIM could not be observed, measurements immediately downstream of the PIM provide insight into the turbulent behavior. Results were analyzed using the Proper Orthogonal Decomposition (POD) and show that the PIM alters the flow field in an advantageous manner by redistributing the turbulent energy, convecting vortical disturbances out of the flow domain, and eliminating the corner recirculation zones, which affect the acoustic behavior of the combustor in a favorable manner.