Investigation of Combustion Instability in Augmentors Using High-Speed PIV and PLIF

The objective of this Phase-II effort is to build and deliver a high-speed laser system for performing particle-image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) of OH at rates of 5 to 10 kHz in augmentor test facilities. This state-of-the-art laser system will allow velocity and 2-D flame radical measurements for understanding the complex spatio-temporal development of instability modes leading to local and global flame extinction. Acquisition of PIV and PLIF images at 5 to 10 kHz will be sufficient to capture the interaction of small- and large-scale structures responsible for initiating or sustaining most of the phenomena that affects augmentor stability. Initial demonstration measurements will be performed in a laboratory turbulent flame where the interaction of vortices (i.e., the instabilities) can be controlled in systematic way for optimizing system performance. Data from these measurements will be used to demonstrate the ability to track instability modes and their spatio-temporal interaction. These laboratory experiments will be followed by the installation of the system at WPAFB for performing measurements under various augmentor conditions dictated by AFRL scientists. Successful implementation of this effort will pave the way for AFRL scientists to address instabilities in other combustors with the state-of-the-art laser diagnostic system.