Studies of a confined rectangular jet -in -crossflow
Abstract
Jets in crossflow are common in many engineering applications including: V/STOL aircraft in transition flight, dilution zones in gas turbine combustors, cooling of turbine blades, gaseous state fuel injection, and numerous manufacturing processes. Despite the extensive research over several decades, basic understanding of the flow physics of even the simplest configuration is still incomplete. One reason for the lack of understanding is the highly turbulent, three-dimensional nature of the flow field including: complex separation and reattachment, shear, and curvature. This experimental investigation of a confined, rectangular jet-in-crossflow is unique for several reasons. Firstly, the rectangular jet spans almost 80% of the crossflow duct, rather than issuing into a semi-infinite crossflow. Secondly, the jet is confined in the cross-stream direction because it issues into a relatively narrow duct. Thirdly, the flow rate of the secondary jet is large (up to 50% of the crossflow flow rate) which also influences the jet-crossflow interaction. This complicated geometry is encountered in a variety of different industrial manufacturing processes used to mix product streams. A systematic variation of the three pertinent parameters, i.e. momentum ratio, injection angle and development length was performed. A full factorial experiment was run using three velocity ratios (Vr = 0.5, 1.0, 1.5), three downstream distances (x/Dh = 6, 10, 19) and six injection angles (α = 18°, 24°, 30°, 48°, 60°, 90°). A planar Mie scattering technique was used to evaluate the relative mixing effectiveness at various conditions within the parameter space studied. Three regimes for the jet-crossflow interaction and the resulting scalar concentration field were revealed: “wall jet”, “fully lifted jet”, and “reattached jet”. To understand the flow physics in these regimes, velocity field data were obtained using laser Doppler velocimetry (LDV). Integrating the scalar concentration and velocity field data has provided an understanding of the large-scale mixing and the role of coherent structures and their evolution. The investigation revealed that the flow does not necessarily develop symmetrically and also highlighted some of the effects of severe confinement.
Degree
Ph.D.
Advisors
Sojka, Purdue University.
Subject Area
Mechanical engineering
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