Aerospace Engineering Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2737
Browse
2 results
Search Results
Item NUMERICAL SIMULATION OF THE BLUE WHIRL: A REACTING VORTEX BREAKDOWN PHENOMENON(2019) Chung, Joseph Dong il; Oran, Elaine S; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The blue whirl is a small, stable, spinning blue flame that evolved spontaneously in recent laboratory experiments while studying turbulent, sooty fire whirls. It burns a range of different liquid hydrocarbon fuels cleanly with no soot production, presenting a new potential way for low-emission combustion. This thesis uses numerical simulations to present, for the first time, the flame and flow structure of the blue whirl. These simulations show that the blue whirl is composed of three different flames - a diffusion flame and a premixed rich and lean flame - all of which meet in a fourth structure, a triple flame which appears as a whirling blue ring. The results also show that the flow structure emerges as the result of vortex breakdown, a fluid instability which occurs in swirling flows. This thesis also presents the development and testing of the numerical algorithms used in the simulation of the blue whirl. This work is a critical step forward in understanding how to use this new form of clean combustion.Item Quasi-One-Dimensional Modeling of an Adiabatic-Compression Preheated Ludwieg Tube(2015) Chung, Joseph Dong il; Laurence, Stuart J; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A novel hypersonic facility is proposed that will reproduce the high pressures and temperatures necessary for the accurate simulation of hypersonic flight conditions. It will provide sufficient test times for investigating unsteady, transient flow effects while maintaining high flow quality due to the absence of vitiation contaminants and shocks in the generating flow. An electrically preheated Ludwieg tube provides the initial means of heating while the piston-compression is used to further increase the pressure and temperature. Preliminary constraints on the design space for optimal operation are presented through the method of characteristics (MOC). Further characterization is performed with quasi-one-dimensional Euler computations. The MOC approach shows the optimal operating condition constrains the compression ratio and Ludwieg tube to nozzle exit diameter ratio, assuming proper simulation of flight conditions. The unsteady Euler computations predict the presence of pressure oscillations generated during the piston-compression process. Methods are investigated to mitigate these oscillations.