MS, University of Cincinnati, 2015, Engineering and Applied Science: Aerospace Engineering

An experimental investigation of response characteristics of a liquid jet in oscillating crossflow is undertaken to understand the behavior of a liquid fuel spray in the presence of combustion instabilities. The effect of crossflow oscillations on the liquid jet is studied in the near-field (within x/d˜8) and the far-field (x/d˜50) spray region. Experiments are conducted in bag breakup, multimode and shear breakup regimes by varying crossflow Weber number from 18 to 250, while momentum flux ratio is varied between 10 and 30. The crossflow is modulated in the frequency range of 90 Hz to 450 Hz, with modulation level varying between 5% and 20%, using a mechanical modulating device. High speed shadowgraph is employed to study the near-field and far-field spray movement while intensified high-speed camera images of laser Mie-scattering intensity are utilized in studying the spray cross-section in the far-field. A technique to extract time-varying momentum flux ratio from the windward trajectory of liquid jet in the near-field is developed. The response of near-field spray is quantified in terms of a ratio of the observed momentum flux ratio extracted from a correlation of upper penetration to the expected momentum flux ratio corresponding to the instantaneous crossflow velocity. The liquid jet penetration is found to respond to oscillations in the crossflow at all oscillation frequencies in the near-field. The strength of the response is found to be mainly dependent on the crossflow oscillation frequency, with the strength of response decreasing with increase in frequency. The momentum flux ratio and the modulation level are found to have relatively negligible effects on the level of normalized spray response. The spray response in the far-field is studied by observing the high-speed shadowgraphs and Mie-scattering intensity images at an axial distance of x/d=50. The spray field in the axial location is divided into ten bins and the intensity change in each bin is analy (open full item for complete abstract)

Committee: Jongguen Lee Ph.D. (Committee Chair); Milind Jog Ph.D. (Committee Member); Mark Turner Sc.D. (Committee Member) Subjects: Aerospace Materials