The Beauty and the Beast: Modeling the Multi-faceted Nature of Chemically Reacting Flows
Speaker: Matthias Ihme, University of Michigan
Department: Mechanical & Aerospace Engineering
Location: Engineering Quadrangle J223
Date/Time: Thursday, March 1, 2012, 4:00 p.m. - 5:00 p.m.
Combustion in gas turbines and propulsion systems is often accompanied by unstable conditions. Examples of this are thermo-acoustic instabilities in lean premixed gas-turbines, autoignition in oxygen-diluted furnaces, and flame lift-off in high-speed propulsion systems. While such conditions provide unique opportunities for improving fuel efficiency and reducing pollutant emissions, the accurate characterization and control of such combustion-dynamic processes introduces significant challenges.
This talk discusses current and ongoing research efforts on the fundamental analysis and high-fidelity modeling of unstable chemically reacting flows. Beginning with the stability analysis of laminar flames (the beauty), effects of wall-heat losses, chemical kinetics, and molecular transport properties on the flame-dynamics in a buoyancy-driven jet diffusion flame are investigated. The second part of this presentation addresses the modeling of turbulent flames (the beast), and large-eddy simulations (LES) of a hydrogen jet in a crossflow at gas-turbine relevant operating condition are conducted. Using data from a direct numerical simulation (DNS) database, fundamental modeling assumptions of LES combustion models are investigated. It is shown that flamelet-based combustion models accurately predict the post-reaction zone, and model extensions are discussed to account for flame-stabilization by heat- recirculation in low-strain regions.
The presentation concludes by discussing the potential of utilizing active control for flame-stabilization, and by providing an overview of other research efforts on the modeling of rocket-combustion and detonation waves.