14 research outputs found
Shock accelerated vortex ring
The interaction of a shock wave with a spherical density inhomogeneity leads
to the development of a vortex ring through the impulsive deposition of
baroclinic vorticity. The present fluid dynamics videos display this phenomenon
and were experimentally investigated at the Wisconsin Shock Tube Laboratory's
(WiSTL) 9.2 m, downward firing shock tube. The tube has a square internal
cross-section (0.25 m x 0.25 m) with multiple fused silica windows for optical
access. The spherical soap bubble is generated by means of a pneumatically
retracted injector and released into free-fall 200 ms prior to initial shock
acceleration. The downward moving, M = 2.07 shock wave impulsively accelerates
the bubble and reflects off the tube end wall. The reflected shock wave
re-accelerates the bubble (reshock), which has now developed into a vortex
ring, depositing additional vorticity. In the absence of any flow disturbances,
the flow behind the reflected shock wave is stationary. As a result, any
observed motion of the vortex ring is due to circulation. The shocked vortex
ring is imaged at 12,500 fps with planar Mie scattering.Comment: For Gallery of Fluid Motion 200
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DOE Project: Optimization of Advanced Diesel Engine Combustion Strategies "University Research in Advanced Combustion and Emissions Control" Office of FreedomCAR and Vehicle Technologies Program
The goal of the present technology development was to increase the efficiency of internal combustion engines while minimizing the energy penalty of meeting emissions regulations. This objective was achieved through experimentation and the development of advanced combustion regimes and emission control strategies, coupled with advanced petroleum and non-petroleum fuel formulations. To meet the goals of the project, it was necessary to improve the efficiency of expansion work extraction, and this required optimized combustion phasing and minimized in-cylinder heat transfer losses. To minimize fuel used for diesel particulate filter (DPF) regeneration, soot emissions were also minimized. Because of the complex nature of optimizing production engines for real-world variations in fuels, temperatures and pressures, the project applied high-fidelity computing and high-resolution engine experiments synergistically to create and apply advanced tools (i.e., fast, accurate predictive models) developed for low-emission, fuel-efficient engine designs. The companion experiments were conducted using representative single- and multi-cylinder automotive and truck diesel engines
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