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Aravind Chandh
(Advisor: Prof. Timothy Charles Lieuwen)
will propose a doctoral thesis entitled,
Coupled Dynamics of an Array of Transverse Jets
On
Thursday, November 10 at 10 a.m.
Montgomery Knight Building 317
Abstract
The jet in crossflow (JICF) is a canonical flow configuration, used extensively in a number of industrial applications like axially staged gas turbine systems, industrial boilers and afterburners. Despite its simple implementation, incorporating this flow configuration in most high-performance systems requires an in-depth understanding of how the flow topology alters macro-phenomena like mixing and flame stabilization. Past studies analyzing the behavior of non-reacting jets have noted that many overall performance features of JICF configurations can be tied to the behavior of the shear layer, which influences both near-field and far-field jet dynamics. As a result, techniques used to manipulate jet mixing and penetration, such as active jet modulation, require an understanding of the dominant instability characteristics of the shear layer.
Although there is a good understanding of the non-reacting and reacting flow field of the single JICF, actual engineering systems typically employ multiple of them spaced closely to each other. For instance, combustors with Rich Burn-Quick Quench-Lean Burn (RQL) architecture, use the multiple JICF (MJICF) topology for rapid mixing of the diluent/quench air with hot combustion gases. The resulting hydrodynamics of the MJICF topology can be very different from the single JICF due to competing pressure gradient effects and multiple interacting concentrated vortex regions. The stability of these flows plays a significant role in controlling many combustor phenomena such as mixing, entrainment, flashback, and blow off. In addition, they also form a feedback mechanism between the acoustics and heat release and, thus, are very important in combustion instability problems.
This proposal seeks to characterize the rich dynamics of the MJICF topology using non-intrusive high-speed laser diagnostics such as Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF). Its overall goal is to determine how the number (e.g., 2, 3, etc.), relative configuration (e.g., axially staged or transversely staged), and spacing between JICF influence its stability. High-speed time-resolved (with respect to the instabilities) and spatially well-resolved PIV measurements will identify the characteristic frequencies and mode shapes of relevant high-frequency structures. Detailed PLIF measurements in the jet centerplane will help provide valuable information regarding the coupling between heat release and hydrodynamics by identifying the dominant heat release modes in a reacting environment. We will also characterize the relative phase, symmetry, and mode shapes between the individual jets. Finally, we will use complex systems approach to investigate collective dynamics of an array of turbulent jets in crossflow.
Committee
