Unsteady Turbulent Jet Flames
Combustion processes are critical to the performance of engines for aeropropulsion (as well as numerous industrial applications). By understanding the behavior of turbulent combustion, the control of its turbulent flame structure will enable the decrease of emissions, and will improve the efficiency of fuel utilization. The latter is of central importance, given that even a percent-level increase in fuel efficiency would considerably decrease fuel consumption in the world.
The research project studies the fuel/air mixing and combustion characteristics of a non-premixed pulsed (unsteady) and unpulsed (steady) flame configuration for both normal- and microgravity conditions. The unsteady flames are fully-modulated, with the fuel flow completely shut off between injection pulses using an externally controlled valve, resulting in the generation of puff-like flame structures. Conducting experiments in normal and microgravity environments clarify the influence of buoyancy on the flame behavior, its mixing, and its structure. Experiments are performed in normal gravity in the laboratory at the University of Washington and in microgravity using the NASA GRC 2.2-second Drop Tower facility. Non-intrusive optical diagnostics (lasers) and temperature and emissions probes are used to determine the large-scale structure dynamics, the details of the flame structure and oxidizer entrainment, the combustion temperatures, and the exhaust emissions of the pulsed and steady flames. Of particular interest is the impact of changes in flame structure due to pulsing on the combustion characteristics of this system.
- Ying-Hao Liao