Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session J24: Impinging and Swirling Jets |
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Chair: Jonathan Naughton, University of Wyoming Room: 251 B |
Sunday, November 24, 2024 5:50PM - 6:03PM |
J24.00001: Primary and Secondary Stage Emissions Characterization for Ammonia RRQL Configuration Renee Cole, Cristian Avila Jimenez, David Wu, Benjamin L Emerson, David Noble, Tim Lieuwen Ammonia is actively being considered as a carbon-free energy source, however, there are significant challenges with the fuel from an emissions perspective. Rich, Relaxation, Quench, Lean (RRQL) is a staged combustion strategy designed to reduce NOx emissions from ammonia combustion by taking advantage of the reduced NOx levels at equilibrium in rich ammonia combustion and allowing them a considerable residence time to relax to equilibrium levels. Excess ammonia or hydrogen is then burned off in a short lean secondary stage, to prevent fuel slip and minimize second-stage NOx production. A new experimental facility for Rich, Relaxation, Quench, Lean (RRQL) combustion of ammonia-air premixed swirl flames in a 0.7 kW atmospheric burner is characterized by emissions measurements and flame imaging. The facility features a modular swirl burner, a long quartz primary stage, and a quench stage with modular jet injection geometries. This presentation presents emissions characterization of the primary stage to find the optimal equivalence ratio which minimizes NOx production and ammonia slip, and preliminary emissions characterization of the various jet injection geometries in the quenching stage. The basic jet-injection quench geometries have produced sub 50 ppm NOx emissions when using optimal primary and global equivalence ratios. |
Sunday, November 24, 2024 6:03PM - 6:16PM |
J24.00002: Investigating the Influence of Swirl on an Axisymmetric Shear Flow using Proper Orthogonal Decomposition Mostafa Ojaghloo, Eric J DeMillard, Jonathan W Naughton Understanding the effects of the addition of swirl to the turbulence structure of axisymmetric shear flows such as wakes and jets is important from both practical and fundamental points of view. Studies have shown that the addition of swirl creates a secondary direction of shear that interacts with the primary shear, leading to higher turbulence levels and increased decay rates. In this study, spectral-spatial Proper Orthogonal Decomposition (POD) is used to identify the large-scale structures[JWN1] in an axisymmetric jet flow with and without swirl. The dataset used in this study consists of Stereoscopic Particle Image Velocimetry (SPIV) measurements of three components of velocity at various cross-sections downstream of the jet exit. The axisymmetric nature of the flow was exploited to simplify the interpretation of the POD results and cross-case comparisons. The results show that the addition of swirl has a significant impact on both the shape of the modes and the energy distribution across the modes. Specifically, the introduction of a tangential component of velocity seems to slightly bend the modes in the direction of swirl, while also shifting the energy towards lower azimuthal modes. |
Sunday, November 24, 2024 6:16PM - 6:29PM |
J24.00003: Experimental Investigation of Coherent Structures in a Generic Dual Swirl Burner Under Broadband Noise Excitation Neha Vishnoi, Aditya Saurabh, Lipika Kabiraj Swirling flows in gas turbine (GT) combustors, used for flame stabilization, are prone to precessing vortex core (PVC), a self-excited global hydrodynamic instability associated with vortex breakdown. This instability leads to large-scale coherent structures and significant flame fluctuations, potentially causing thermoacoustic instability. While previous studies have explored PVC excitation and suppression under single-frequency acoustic excitation, GT combustors exhibit inherent noise dynamics that vary with operating conditions and combustor designs. It is thus essential to examine how these coherent structures interact with inherent combustor noise. This study experimentally investigates the flow features and coherent structures of an unconfined counter-rotating dual swirl burner. The aim is to understand the interaction between PVC and broadband noise excitation, to develop strategies for mitigating thermoacoustic instability. Schlieren image velocimetry captures mean flow characteristics, while proper orthogonal decomposition analysis identifies dominant coherent structures. The study examines two excitation types: (i) frequencies lower than natural PVC frequency, and (ii) broadband noise excitation at varied amplitudes. Preliminary results show natural flow includes single and double helical PVC modes at St = 0.53. Low-frequency acoustic actuation (St = 0.46) suppresses PVC, while broadband noise excites both PVC modes. |
Sunday, November 24, 2024 6:29PM - 6:42PM |
J24.00004: Upstream Sound Generation Mechanisms in Supersonic Impinging Jets Nathan Baber, Jacob Nalagan, Chitrarth Prasad A supersonic jet impinging on a flat plate is a fundamental problem with applications ranging from launch vehicles to cold spray manufacturing. The flow field is characterized by a self-sustaining aeroacoustic resonance between the downstream convecting shear layer structures and upstream travelling acoustic waves generated by their impingement. Despite extensive investigations into the feedback process, the precise mechanisms by which upstream travelling acoustic waves are generated remain unclear. This investigation aims to enhance our understanding of the generation of upstream acoustic waves upon jet impingement by employing two well-resolved numerical databases of Mach 1.27 and Mach 3.7 jets at different impingement heights. The databases are subsequently decomposed into their exact hydrodynamic, acoustic, and thermal components using Doak’s Momentum Potential Theory, allowing a straightforward examination of the downstream convecting and upstream radiating components of the feedback loop. By visualizing the hydrodynamic and acoustic components simultaneously, we gain insights into the sound generation mechanisms at the impingement zone. At both Mach numbers, upstream acoustic waves are generated due to the bifurcation and subsequent compression of a hydrodynamic structure between the plate and the preceding shear layer structure. |
Sunday, November 24, 2024 6:42PM - 6:55PM |
J24.00005: Heat and mass transfer of laminar jets impinging a heated surface Thibaut Juhan, Ivana Vinkovic, Serge Simoëns The features of catalytic reactors result from the interplay of catalyst properties and the heat and mass transfer near the active surface. The last one has an important effect on the reaction rate and thus on the reactor efficiency. A multi impinging jet configuration is studied here. The resulting flow dynamics are analyzed with the scope of enhancing the surface heat and mass transfer and thus improving the catalytic reactor efficiency. |
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