Bulletin of the American Physical Society
75th Annual Meeting of the Division of Fluid Dynamics
Volume 67, Number 19
Sunday–Tuesday, November 20–22, 2022; Indiana Convention Center, Indianapolis, Indiana.
Session T25: Reacting Flows: Turbulent Reacting Flows |
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Chair: Aarthi Sekaran, SUNY Polytechnic Institute Room: 233 |
Monday, November 21, 2022 4:10PM - 4:23PM |
T25.00001: Influence of thermal radiation on laminar coal-dust flames Jose Aguilar, Ryan W Houim A numerical simulations study was performed to examine the influence of thermal radiation on the propagation of coal dust flames. The compressible reacting Navier-Stokes equations coupled to a Eulerian granular multiphase flow model were solved. The geometrical setup consists of a channel with one open end filled with a coal-dust and air mixture. No-slip, adiabatic boundary conditions are used on the top and bottom walls of the channel. Detailed chemical reactions were used to describe the combustion of coal and volatiles. Thermal radiation was included for by solving the radiation transfer equation using a third-order filtered spherical harmonics approximation. The coal dust is ignited with high temperature products placed near the open end of the channel. The flame then propagates stably towards the closed end of the channel. Computational results show that thermal radiation produces a significant preheating effect in the reactants. The results also show that radiation has a large effect on the morphology of the flame. In some cases, a cusp-like flame shape formed when radiation was included, while neglecting thermal radiation produced a completely different flame shape. |
Monday, November 21, 2022 4:23PM - 4:36PM |
T25.00002: a discussion of scaling the blue whirl EBUZER T BALCI, Elaine S Oran The blue whirl (BW) is a small, completely blue, soot-free flame that was originally seen as it evolved from small laboratory-scale fire whirl (FW) measurements of FWs burning liquid hydrocarbons on water. The BWs seen were about 2–2.5 cm in diameter and 6–8 cm in height and sat above the water. They were subsequently shown to be cleaner and safer than FWs. The suggestion, then, was that the soot-free nature of a BW would make it a perfect candidate for a clean energy source, and its burning efficiency could lead to better burners. The next questions, then, involve stability and scaling. Here we consider whether if and how the size of the BW might be changed to increase the rate of fuel consumption. A previous scaling analysis (Hariharan et al., Physical Review Fluids, 2020) based on the small BW data showed that a broad range of parameters could influence its formation and size. These include but are not limited to inflow velocity, type of inflow, fuel injection rate, and inlet area. We now show the implications of this scaling law and particular of the relation between vorticity and buoyancy in changing the size of the BW. |
Monday, November 21, 2022 4:36PM - 4:49PM |
T25.00003: Characterization of Aerobic and Anaerobic Prompt Ignition of Explosively-Dispersed Aluminum Particles Brayden R Roque, Jacob W Posey, Ryan W Houim Numerical simulations on the dispersal, ignition, and combustion of an aluminum (Al) particle shell surrounding a high-explosive (HE) charge were performed. The simulations used a compressible Eulerian granular two-fluid model that accounts for particle collisions and compaction effects. The gas-phase used the Becker-Kistiakowsky-Wilson (BKW) equation of state. Aerobic and anaerobic burning of the Al was modeled using a hybrid diffusion- and kinetic-limited approach based on empirical data. Detailed chemical reactions were used to describe afterburning of fuel-rich detonation products and aluminum sub-oxide species. The detonation of the HE is modeled in the constant-volume explosion limit and using a programmed burn approach. The model is capable of fully coupling the expansion of the detonation products, dispersal of the Al particles, and afterburning. Computed results show the expanding Al particle shell can ignite from the outside due to the shock-heated air when the layer is thin. The particle shell is also shown to ignite anaerobically in the interior due to high-pressure detonation products when a thick layer is used with a stronger HE. |
Monday, November 21, 2022 4:49PM - 5:02PM |
T25.00004: Simulation of the SiConi preclean process to predict uniform oxide removal on Si wafers Aarthi Sekaran, Michael Taber, Domingo Ferrer Luppi Semiconductor wafers are essential in modern-day electronics, typically used for photovoltaics or ICs, and go through multiple processing stages before final deployment. The SiConi preclean is one such remote plasma-assisted dry surface preparation process that involves simultaneous exposure of the wafer substrate with a SiO2 film to NF3, and NH3 reactive plasma. As a result, fluorosilicate salts are generated via a reaction of the NH4F reactive species with the SiO2 film followed by an annealing process where volatile salts are sublimated to SiF4 and NH3. The combined process allows for a damage-free removal of surface oxide, resulting in decreased contact resistance and enhanced reliability of middle-of-the-line (MOL) interconnects. While SiConi is one of the more commonly used dry preclean processes, the role of various physical parameters during the process remains to be determined. This study focuses on carrying out numerical simulations of the SiConi etch process to determine conditions for uniform center-to-edge oxide removal. A 300mm Si wafer is set up under a showerhead that delivers reactants from a remote plasma and the final thickness of the oxide layer is measured. We evaluate the influence of temperature and predict oxide removal for blanket and patterned wafers. |
Monday, November 21, 2022 5:02PM - 5:15PM |
T25.00005: Eulerian-Lagrangian LES analysis of residence time in a scramjet cavity combustor Matthew Bonanni, Andrew Norris, Matthias Ihme One of the principal considerations in the design of scramjet combustors is the residence time associated with the flame stabilization mechanism. This residence time must be long enough to allow for mixing and combustion processes to occur. A traditional approach for numerical evaluation of this quantity involves the injection of a passive scalar into the cavity and subsequent measurements of the decay in its concentration, yielding only a single mean value of the residence time. This work presents a one-way coupled Eulerian-Lagrangian approach in which passive tracer particles are injected into the flow. This enables continuous measurement of residence time with spatially and temporally varying statistics as well as improved analysis of mixing without disturbing the Eulerian field. This approach is applied to large-eddy simulations of a cavity-stabilized scramjet combustor in both non-ignited and ignited states, the effects of combustion on the flow field are evaluated, and implications on combustor design are discussed. |
Monday, November 21, 2022 5:15PM - 5:28PM |
T25.00006: Performance considerations for In-Situ Adaptive Manifolds for turbulent combustion modeling Israel J Bonilla, Cristian E. Lacey, Michael E Mueller Manifold-based combustion models reduce the computational cost of turbulent |
Monday, November 21, 2022 5:28PM - 5:41PM |
T25.00007: Manifold-based Modeling for Supersonic Turbulent Combustion Esteban Cisneros-Garibay, Michael E Mueller A methodology to incorporate high-speed compressibility effects into manifold-based models for supersonic turbulent combustion simulations is presented. The methodology jointly evaluates the simulation equation-of-state (EOS) and the manifold equations to ensure consistency of the thermodynamic state. In practice, the algorithm iteratively adjusts manifold inputs (fuel/oxidizer temperature and pressure) to reflect the non-negligible variations in thermodynamic state (expressed in terms of density and energy in the simulation), and is significantly more accurate (by over a factor of 10) than existing methods that only partially couple the EOS and the manifold, as demonstrated using data from high-speed nonpremixed-flame simulations. The validity of key modeling assumptions, notably a presumed relationship between enthalpy and mixture fraction, is critically assessed in the context of strong compressibility effects, such as shock-flame interactions, to provide potential model improvements. |
Monday, November 21, 2022 5:41PM - 5:54PM |
T25.00008: Data-based modeling of instantaneous dissipation rate profiles in multi-modal turbulent combustion Cristian E. Lacey, Martin Rieth, Jacqueline H Chen, Michael E Mueller Computational modeling approaches must be developed to more accurately and efficiently characterize multi-modal turbulent combustion. The computational cost of turbulent combustion modeling can be reduced considerably by projecting the thermochemical state onto a low-dimensional manifold, but, in traditional approaches, a single manifold coordinate of mixture fraction or progress variable limits model applicability to a single combustion 'mode.' While new approaches with two manifold coordinates (mixture fraction and generalized progress variable) can describe multi-modal combustion, more dissipation rates appear in the manifold equations as coefficients. These dissipation rates vary with mixture fraction and generalized progress variable and must be modeled. This work leverages DNS data of a temporally evolving n-dodecane jet flame to extract instantaneous dissipation rate profiles and interpolate their values in unaccessed regions of manifold space via Gaussian process regression (GPR). A deep neural network (DNN) is then trained to predict the instantaneous profiles as a function of coarse-grained data to provide model closure for the manifold equations, resulting in a hybrid physics-derived and data-derived model applicable to multi-modal combustion. |
Monday, November 21, 2022 5:54PM - 6:07PM |
T25.00009: The influence of scalar dissipation rate fluctuations on turbulent premixed flames at varying Karlovitz number Katie VanderKam, Michael E Mueller Manifold-based combustion models can be utilized to described turbulent premixed combustion using one-dimensional equations in terms of a progress variable. The progress variable dissipation rate appears as a key parameter in the manifold equations dictating the characteristics of premixed combustion from "flamelet" combustion at lower dissipation rates to "distributed" combustion at higher dissipation rates. However, this dissipation rate is constant in neither time nor space, and these fluctuations have a significant effect on the behavior of the flame structure, specifically that of the reaction zone. To better understand the influence of dissipation rate fluctuations, detailed simulations have been conducted for hydrogen premixed flames at a variety of turbulent conditions and Karlovitz numbers, and the variation of progress variable dissipation rate is assessed at a number of locations within the flame. The influence of the dissipation rate fluctuations on the flame behavior is evaluated through an analysis of the subsequent influence on the thermochemical state. |
Monday, November 21, 2022 6:07PM - 6:20PM |
T25.00010: Small-scale intermittency of turbulent premixed flames Amitesh Roy, Jason R Picardo, Benjamin L Emerson, Timothy C Lieuwen, R I Sujith Premixed turbulent flames play a central role in combustion and power generation devices, and are an archetype of randomly advected, self-propagating surfaces. The interaction of premixed flames with turbulence are, thus, of practical and fundamental importance. While much is known about their large-scale behaviour, the dynamics of small-scale fluctuations are not well understood. From temporally resolved experimental data of methane-air V-flame, we reveal self-similar scaling and small-scale intermittency in the fluctuations of the premixed flame. We show that the frequency spectra follows a power-law behaviour with a slope of -2 in the inertial sub-range, which is rationalized in terms of the flame surface passively responding to inertial range eddies. Upon quantifying the higher-order statistics, we find that the structure-functions scale anomalously, with high frequency fluctuations depicting increasingly non-Gaussian behaviour—a signature of small-scale intermittency. Our study have important implications for modeling turbulent flame speeds and heat release rate in premixed flames. |
Monday, November 21, 2022 6:20PM - 6:33PM Author not Attending |
T25.00011: Double period thermoacoustic oscillation in swirl stabilised flame Ankit D Dilip Kumar, James C Massey, Michael Stöhr, Wolfgang Meier, Nedunchezhian Swaminathan A partially-premixed swirl-stabilised CH4-Air flame is studied using Large Eddy Simulation (LES). LES is performed at a thermal load of Pth = 25kW and a global equivalence ratio of Φ = 0.9 using an unstrained flamelet model for sub-grid reaction rate. Simulation results show good agreement with PIV and Raman measurements for velocity, temperature and mixture fraction statistics. A self-excited thermoacoustic instability undergoing a period-2 limit cycle oscillation (LCO) at 314 Hz (f1) and 628 Hz (f2) is observed. The pressure amplitude of the LCO has a time-varying behaviour at f2. Time-evolution of the flame, flow fields and coherent structures are studied during the thermoacoustic cycle to reveal the feedback mechanism. The three-dimensional phase space representation of pressure shows a double-loop attractor. The heat release rate strongly couples with the first mode compared to the second mode resulting in a single-loop attractor. Rayleigh index based on the Rayleigh Criterion [2] is analysed to understand the stronger coupling of the heat release rate and pressure fluctuations at f1 compared to f2. |
Monday, November 21, 2022 6:33PM - 6:46PM |
T25.00012: Numerical Simulations of turbulent non-premixed cool flames at supercritical/high pressures: dual peak structure, pressure scaling and real-gas effects Navneeth Srinivasan, Ramachandran Suryanarayan, Hongyuan Zhang, Taaresh S Taneja, Suo Yang We present adaptive mesh refinement (AMR)-based 2-D DNS-like simulations of a dimethyl ether (DME)-air temporal turbulent reacting mixing layer with detailed chemistry at 80, 120, and 150 atm. The critical pressure for the fuel mixture obtained from a Vapor-Liquid Equilibrium calculation is 147 atm–indicating mixing occurs between two supercritical gas-like fluids at 150 atm and a subcritical gas-like fuel with a supercritical gas-like oxidizer at 120 and 80 atm. The simulations are performed using both ideal gas and Soave-Redlich-Kwong (SRK) equations of state (EoS) to study real-gas effects. Contours of heat release rate (HRR), temperature, mass fractions of LTC-specific species of DME (e.g., CH3OCH2O2) and CH2O reveal the formation of cool flames that subsequently transition into spotty hot flame kernels. Mixture-fraction conditioned averages of the above quantities exhibit a dual-peak structure due to the unsteady nature of the flow and the presence of multiple temperature-dependent reaction pathways. Deviations in the order of 10-20% are observed between real and ideal gas EoS in predicting temperature and density and up to 30-40% for radical mass fractions at both high-pressure subcritical and supercritical pressures. |
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