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 L34: Reacting Flows: Turbulent Combustion |
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Chair: Martin Rieth, Sandia National Laboratories Room: 255 F |
Monday, November 25, 2024 8:00AM - 8:13AM |
L34.00001: Numerical investigation of the structure of a randomly advected Huygens front using a minimal stochastic model Alan R Kerstein, Jackson R Mayo Theoretical predictions (J. R. Mayo and A. R. Kerstein, J. Stat. Phys. 176:456-477, 2019) of structural features of a Huygens front randomly advected by turbulence, in the limit of vanishing local front propagation speed, are confirmed using an adaptation of the linear-eddy model (LEM). In particular, the 1D numerical simulations confirm that the mean streamwise extent of the advectively dispersed front diverges as the logarithm of the advective fluctuation intensity normalized by the front propagation speed, while the root-mean-square streamwise dispersion of front surface density diverges as the square root of that logarithm. These results support the 3D theoretical framework, which additionally predicted that the bulk front-advancement velocity is finite in the considered limit, implying a propagation anomaly analogous to the turbulent dissipation anomaly. The mean streamwise profiles of the progress variable and its turbulent flux in LEM are found to resemble those of propagating fronts advected by 3D turbulence. This suggests that the present results, focusing on a particular limit of the narrowband advection regime, are relevant to the physically important 3D case. [SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.] |
Monday, November 25, 2024 8:13AM - 8:26AM |
L34.00002: ABSTRACT WITHDRAWN
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Monday, November 25, 2024 8:26AM - 8:39AM |
L34.00003: In-Situ Adaptive Manifolds Beyond Two-Stream, Uni-Modal Turbulent Combustion Israel J Bonilla, Cristian E. Lacey, Michael E Mueller Turbulent reacting flow simulation faces dual challenges due to the broad range of scales as well as the high-dimensionality of the thermochemical state. Manifold-based combustion models reduce the computational cost imposed by those challenges by projecting the thermochemical state onto a lower-dimensional manifold. In-Situ Adaptive Manifolds (ISAM) computes solutions to manifold equations 'on-the-fly' and stores the solutions for reuse by In-Situ Adaptive Tabulation (ISAT) with demonstrated computational cost and memory savings for uni-modal combustion processes featuring two inlet streams over the traditional method of precomputing and pretabulating manifold solutions. In this work, the ISAM approach is further generalized and demonstrated. First, manifold-based models have traditionally been limited to two-stream combustion. Developments of a model for three-stream combustion and beyond are discussed and demonstrated in Large Eddy Simulation (LES). Second, manifold-based models have traditionally presumed a single asymptotic combustion mode. Developments of a model for mode-agnostic manifold-based models are also discussed and demonstrated in LES including the effects of the cross-dissipation rate between the mixture fraction and the generalized progress variable. |
Monday, November 25, 2024 8:39AM - 8:52AM |
L34.00004: Explicit Simulation of Small Scales in Chemically Reacting Turbulent Flows using the Two-Level Simulation Model Reetesh Ranjan, Eli Durant Numerical investigation of chemically reacting turbulent flows tends to be computationally expensive due to the need to capture the multiscale flame turbulence interactions. Although significant advancements have been made in model-based approaches, there is still a need for a robust and predictive model for such flows under different operating regimes and conditions. In this study, we examine the capabilities of the two-level simulation (TLS) model. The model relies on a scale-decomposition strategy to obtain large-scale (LS) and small-scale (SS) governing equations, which is followed by simplification of the SS equations to express them on one-dimensional domains leading to an efficient simulation strategy. Unlike other models where the effects of unresolved SS dynamics are parametrized, in the TLS model, the SS flow field is explicitly simulated in a coupled manner with the LS flow field, thus leading to unique capabilities to capture the SS dynamics. We evaluate the performance of the TLS model by considering two challenging test cases, namely, a freely propagating turbulent premixed flame in the thin reaction regime and a temporally evolving non-premixed jet flame exhibiting local extinction and re-ignition events. First, we assess the validity of the SS modeling assumptions and the ability of the model to capture SS physics such as anisotropy, counter-gradient transport, scalar dissipation rate, etc. Afterward, we perform a posteriori assessment in terms of the evolution of SS quantities. |
Monday, November 25, 2024 8:52AM - 9:05AM |
L34.00005: The impact of nozzle shape on mixing, combustion efficiency, and flame blowout velocity. Ashray Mohit, Jenna E Stolzman, Margaret S Wooldridge, Jesse S Capecelatro Waste gas flares are subjected to a range of turbulent flow conditions that adversely affect combustion efficiency downstream of the nozzle. In extreme cases, this leads to flame extinction due to excessive straining, causing a rapid drop in combustion efficiency and a sharp increase in the concentration of vented waste gases. In this work, methane combustion in a jet in cross-flow is simulated for a range of momentum ratios and canonical nozzle shapes to understand the effect of nozzle geometry on mixing, combustion efficiency, and flame blowout velocity. The simulations are performed using large-eddy simulation (LES) coupled with a flamelet progress variable approach (FPVA). Blow-off velocity and mixing metrics are validated against a range of experiments. This study aims to understand the effect of the nozzle shapes, while holding the exit area constant, and identify the geometries that lead to better global mixing, provide better combustion efficiencies, and sustain flames at stronger crosswinds. |
Monday, November 25, 2024 9:05AM - 9:18AM |
L34.00006: Influence of geometry on interactions between turbulence and premixed flames Katie E VanderKam, Michael E Mueller Many premixed turbulent combustion studies examine planar flame configurations due to their computational and geometric simplicity. However, practical combustion systems feature more complex geometries, and the resulting turbulent premixed flames are not strictly planar. This work compares fuel-rich hydrogen turbulent premixed flames in a planar flame configuration with a strongly sheared configuration to determine whether the configuration used has an impact on the flame structure and properties. The detailed simulations for these configurations are evaluated both statistically and through the lens of a manifold combustion model, looking particularly at the effect of the progress variable dissipation rates and turbulent structures on the flame. The results indicate that the planar configuration may limit the range of turbulent premixed combustion regimes that can be accessed: the strongly sheared configuration at nominally identical flow conditions as the planar configuration yields flames with very different structures. |
Monday, November 25, 2024 9:18AM - 9:31AM |
L34.00007: Chemical analysis of emission characteristics in bluff body stabilized turbulent premixed methane-air flames Anant Girdhar, Sriram P Kalathoor, Jechiel Jagoda The practical operation of gas turbine combustors typically involves a balance between emissions and flame stability. Operating in the lean regime to maximize efficiency comes at the cost of potential blow-off, which can be prevented by employing flameholding devices like bluff-bodies. The flame dynamics and mixing processes in these combustors depend heavily on the flame chemistry and its interaction with the turbulent processes. Modeling the chemistry is therefore paramount in being able to accurately make predictions regarding the operation of these combustors. Most of the work in this space has been focused on studying unconfined flames. In this study, we perform a chemical kinetic analysis of methane-air flames in a confined bluff-body stabilized combustor at similar conditions as Pathania et al (2017). We use OpenFOAM to perform Large Eddy Simulations and compare the reduced 17-species model by Sankaran (2007) and the detailed GRI 3.0 models in their ability to predict CO emissions. We perform simulations over a computational domain of 4.5 million grid points and compare various chemical and flowfield quantities in the upstream, recirculation, and downstream regions to understand their relative strengths and weaknesses. |
Monday, November 25, 2024 9:31AM - 9:44AM |
L34.00008: Numerical simulations of flame structure and soot formation of biodiesel spray combustion Alice Ponet, Miltiadis V. Papalexandris
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Monday, November 25, 2024 9:44AM - 9:57AM |
L34.00009: Modeling strategies and experimental comparison for large-eddy simulations of a laser-ignited rocket combustor Davy Brouzet, Tony Zahtila, Diego Rossinelli, Alboreno Voci, Gianluca Iaccarino, Donatella Passiatore, Ryan Mathew Strelau, Rohan M Gejji, Carson D Slabaugh One of the main goals of the Stanford Predictive Science Academic Alliance Program (PSAAP) III Center is to predict the reliability of laser ignition in a methane and oxygen-fueled rocket combustor under in-flight conditions. This prediction relies on multifidelity ensembles of numerical simulations running on exascale-class, heterogeneous supercomputers (CPUs and GPUs). To evaluate the accuracy and reliability of the Hypersonics Task-based Research (HTR) solver (Di Renzo et al., Computer Physics Communications, 2020), which was developed as part of the Stanford PSAAP-II and PSAAP-III Centers, parallel experimental validation efforts are being conducted in a rocket combustor configuration at the Zucrow Propulsion Laboratory at Purdue University. This study aims to evaluate modeling strategies for performing Large Eddy Simulations (LES) of laser-ignited rocket combustors by comparing numerical results with experimental data. The focus is on three key aspects of the ignition process: 1) the non-reacting coaxial jet in the pre-ignition stage, 2) the hot kernel dynamics resulting from laser energy deposition, and 3) the post-ignition combustion process. First, we quantitatively evaluate the performance of the LES by comparing the mean flow statistics to PIV data. Next, we assess the sensitivity of the hot kernel dynamics, characterized by the formation of an ejecta, to various modeling parameters. By comparing the numerical results with experimental Schlieren imaging, we establish the uncertainty range of these parameters, accounting for shot-to-shot variability. Finally, we demonstrate the benefits of using a dynamic thickened flame combustion model when considering the flame expansion and pressure rise within the combustor. |
Monday, November 25, 2024 9:57AM - 10:10AM |
L34.00010: Effects of Supercritical Carbon Dioxide Dilution on Oxy-Methane Combustion Using a DNS Approach Dorrin Jarrahbashi, Rohit Mishra Supercritical oxy-combustion cycles use supercritical CO2 (sCO2) as a working fluid and diluent with pure oxygen as the oxidizer, providing high efficiency and reduced emissions for power generation with carbon capture. Designing direct-fired oxy-fuel combustors is challenging due to the lack of understanding of combustion at supercritical pressures (~200 bar) influenced by sCO2 dilution. A Direct Numerical Simulation (DNS) framework, incorporating a one-step chemistry mechanism and multispecies real-fluid properties, reveals supercritical mixing and combustion under the operating conditions of Southwest Research Institute's (SWRI) sCO2 oxy-combustor. The results show that CO2 dilution significantly impacts heat release rate, temperature, and flame edge thickness. Optimal heat release rate and lowest CO production occur at 75%-80% CO2 dilution, with a maximum temperature of 2000 K. These findings provide essential insights for designing sCO2 oxy-combustors. |
Monday, November 25, 2024 10:10AM - 10:23AM |
L34.00011: Numerical and experimental study of extinction limits of partially premixed counterflow flames Fuga Sato, Mahmoud Ashour, Owen Fuhr, Francesco Carbone, Xinyu Zhao Combustion involving fuel droplets is widely used in practical combustion systems such as internal combustion engines and aeronautical combustors. A robust and quantitative description of flame extinction in spray flames is crucial for optimal engine design and flame stabilization. One complicating factor in spray flame extinction is the spatially inhomogeneous fuel distribution resulting from multi-physical processes such as evaporation and turbulent fluctuation. In this study, we numerically investigate extinction limits for one-dimensional partially premixed laminar counterflow flames for various fuels, including methane, n-heptane, JetA, and n-dodecane. For a system with a specific global equivalence ratio, we define multiple heterogeneous flames and discuss their extinction limits. Obtained extinction limits for methane/air flames are compared with experimental data and model uncertainties are explored. For methane/air flames, we observe extended extinction limits in rich flames as becomes larger. On the other hand, decreased extinction limits were found in lean and stoichiometric partially premixed methane/air flames, although the reduction is not significant. For large hydrocarbons, although significant increase in the extinction limits was observed in lean flames, extinction limits of stoichiometric and rich flames had almost the same values with the homogeneous flames. Finally, multidimensional quasi-DNS simulations are performed for gaseous and spray flames near the extinction limits using an open-source AMR solver PeleLMeX and compared with the canonical one-dimensional flames. |
Monday, November 25, 2024 10:23AM - 10:36AM |
L34.00012: Simulations of Boundary Layer Flashback in Hydrogen Flames Esaias M Burns, Alex G Novoselov
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