High-Bandwidth Laser-Based Measurements and Modeling for Thermoacoustic Instabilities in High-Pressure Combustors for Aerospace Fuels and Emerging Alt

ABSTRACT: The objectives of this Phase-II research effort are to perform various advanced laser-based measurements in a swirl stabilized combustor test cell, in a high-pressure combustor, and turbulent laboratory flames for various hydrocarbon fuels in order to identify suitable technologies as well as to develop a mathematical model for investigating various combustion instabilities with the aim of devising intelligent control strategies. This effort addresses the need for non-intrusive diagnostic approaches that can provide high-speed, planar, spatio-temporally resolved images of velocity, temperature, and species concentrations over data sets of several thousand images. The proposal also addresses the need for combustion instability model for various alternative fuels based on the high-bandwidth data acquired with non- invasive laser-based measurements. Two unique modeling approaches (Flamelet Dynamics Model and Chaos Theory Based Model) will be carried out for providing guidance on combustion instability and their growth phenomena with the aim of devising proper control strategies. These measurements along with the model(s) will pave the way for the development of a combustion instability model related to high-pressure combustors/augmentors utilizing alternative jet fuels during the Phase-II research effort. In particular, these experiments will shed light on to the influence of C/H ratio in modifying the dominant combustion instability behavior. BENEFIT: Instrumentation and instability models for measuring temperature and species concentrations in combusting flows has proven to be critical in the deployment of propulsion systems for the warfighter. Qualitative optical techniques, such as high-speed imaging, have, in some cases, proven to be instructive and have helped to guide measurement efforts. However, specific design details may require quantitative, spatio-temporally resolved information such as heat release rate, temperature, and equivalence ratios at a rate of 1 kHz or greater. Hence, the optical sensors and the instability models proposed here offer a significant potential impact through reductions in development time and the improved reliability of propulsion devices for the DoD mission. This research effort will lead to a new and improved design of advanced combustion systems for propulsion applications. The optical sensing technologies should be very valuable to various engine manufacturers as well as to power- plant manufacturers.