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Rowan, Steven L., Ismail B. Celik, Albio D. Gutierrez i Jose Escobar Vargas. "A Reduced Order Model for the Design of Oxy-Coal Combustion Systems". Journal of Combustion 2015 (2015): 1–9. http://dx.doi.org/10.1155/2015/943568.
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Oxy-coal combustion is one of the more promising technologies currently under development for addressing the issues associated with greenhouse gas emissions from coal-fired power plants. Oxy-coal combustion involves combusting the coal fuel in mixtures of pure oxygen and recycled flue gas (RFG) consisting of mainly carbon dioxide (CO2). As a consequence, many researchers and power plant designers have turned to CFD simulations for the study and design of new oxy-coal combustion power plants, as well as refitting existing air-coal combustion facilities to oxy-coal combustion operations. While CFD is a powerful tool that can provide a vast amount of information, the simulations themselves can be quite expensive in terms of computational resources and time investment. As a remedy, a reduced order model (ROM) for oxy-coal combustion has been developed to supplement the CFD simulations. With this model, it is possible to quickly estimate the average outlet temperature of combustion flue gases given a known set of mass flow rates of fuel and oxidant entering the power plant boiler as well as determine the required reactor inlet mass flow rates for a desired outlet temperature. Several cases have been examined with this model. The results compare quite favorably to full CFD simulation results.
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Sikorski, K., Kwan Liu Ma, Philip J. Smith i Bradley R. Adams. "Distributed combustion simulations". Energy & Fuels 7, nr 6 (listopad 1993): 902–5. http://dx.doi.org/10.1021/ef00042a029.
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Åkerblom, Arvid, Francesco Pignatelli i Christer Fureby. "Numerical Simulations of Spray Combustion in Jet Engines". Aerospace 9, nr 12 (16.12.2022): 838. http://dx.doi.org/10.3390/aerospace9120838.
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The aviation sector is facing a massive change in terms of replacing the currently used fossil jet fuels (Jet A, JP5, etc.) with non-fossil jet fuels from sustainable feedstocks. This involves several challenges and, among them, we have the fundamental issue of current jet engines being developed for the existing fossil jet fuels. To facilitate such a transformation, we need to investigate the sensitivity of jet engines to other fuels, having a wider range of thermophysical specifications. The combustion process is particularly important and difficult to characterize with respect to fuel characteristics. In this study, we examine premixed and pre-vaporized combustion of dodecane, Jet A, and a synthetic test fuel, C1, based on the alcohol-to-jet (ATJ) certified pathway behind an equilateral bluff-body flameholder, spray combustion of Jet A and C1 in a laboratory combustor, and spray combustion of Jet A and C1 in a single-sector model of a helicopter engine by means of numerical simulations. A finite rate chemistry (FRC) large eddy simulation (LES) approach is adopted and used together with small comprehensive reaction mechanisms of around 300 reversible reactions. Comparison with experimental data is performed for the bluff-body flameholder and laboratory combustor configurations. Good agreement is generally observed, and small to marginal differences in combustion behavior are observed between the different fuels.
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Tamanampudi, Gowtham Manikanta Reddy, Swanand Sardeshmukh, William Anderson i Cheng Huang. "Combustion instability modeling using multi-mode flame transfer functions and a nonlinear Euler solver". International Journal of Spray and Combustion Dynamics 12 (styczeń 2020): 175682772095032. http://dx.doi.org/10.1177/1756827720950320.
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Modern methods for predicting combustion dynamics in high-pressure combustors range from high-fidelity simulations of sub-scale model combustors, mostly for validation purposes or detailed investigations of physics, to linearized, acoustics-based analysis of full-scale practical combustors. Whereas the high-fidelity simulations presumably capture the detailed physics of mixing and heat addition, computational requirements preclude their application for practical design analysis. The linear models that are used during design typically use flame transfer functions that relate the unsteady heat addition [Formula: see text] to oscillations in velocity and pressure ([Formula: see text] and [Formula: see text]) that are obtained from the wave equation. These flame transfer functions can be empirically determined from measurements or derived from theory and analysis. This paper describes a hybrid approach that uses high-fidelity simulations to generate flame transfer functions along with nonlinear Euler CFD to predict the combustor flowfield. A model rocket combustor that presented a self-excited combustion instability with pressure oscillations on the order of 10% of mean pressure is used for demonstration. Spatially distributed flame transfer functions are extracted from a high-fidelity simulation of the combustor and then used in a nonlinear Euler CFD model of the combustor to verify the approach. It is shown that the reduced-fidelity model can reproduce the unsteady behavior of the single element combustor that was both measured in the experiment and predicted by a high-fidelity simulation reasonably well.
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Pries, Michael, Andreas Fiolitakis i Peter Gerlinger. "Numerical Investigation of a High Momentum Jet Flame at Elevated Pressure: A Quantitative Validation with Detailed Experimental Data". Journal of the Global Power and Propulsion Society 4 (18.12.2020): 264–73. http://dx.doi.org/10.33737/jgpps/130031.
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The development of efficient low emission combustion systems requires methods for an accurate and reliable prediction of combustion processes. Computational Fluid Dynamics (CFD) in combination with combustion modelling is an important tool to achieve this goal. For an accurate computation adequate boundary conditions are crucial. Especially data for the temperature distribution on the walls of the combustion chamber are usually not available. The present work focuses on numerical simulations of a high momentum jet flame in a single nozzle FLOX® type model combustion chamber at elevated pressure. Alongside the balance equations for the fluid the energy equation for the solid combustor walls is solved. To assess the accuracy of this approach, the temperature distribution on the inner combustion chamber wall resulting from this Conjugate Heat Transfer (CHT) simulation is compared to measured wall temperatures. The simulation results within the combustion chamber are compared to detailed experimental data. This includes a comparison of the flow velocities, temperatures as well as species concentrations. To further assess the benefit of including the solid domain in a CFD simulation the results of the CHT simulation are compared to results of a CFD computation where constant temperatures are assumed for all walls of the combustion chamber.
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Fooladgar, Ehsan, i C. K. Chan. "Large Eddy Simulation of a Swirl-Stabilized Pilot Combustor from Conventional to Flameless Mode". Journal of Combustion 2016 (2016): 1–16. http://dx.doi.org/10.1155/2016/8261560.
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This paper investigates flame and flow structure of a swirl-stabilized pilot combustor in conventional, high temperature, and flameless modes by means of a partially stirred reactor combustion model to provide a better insight into designing lean premixed combustion devices with preheating system. Finite rate chemistry combustion model with one step tuned mechanism and large eddy simulation is used to numerically simulate six cases in these modes. Results show that moving towards high temperature mode by increasing the preheating level, the combustor is prone to formation of thermalNOxwith higher risks of flashback. In addition, the flame becomes shorter and thinner with higher turbulent kinetic energies. On the other hand, towards the flameless mode, leaning the preheated mixture leads to almost thermalNOx-free combustion with lower risk of flashback and thicker and longer flames. Simulations also show qualitative agreements with available experiments, indicating that the current combustion model with one step tuned mechanisms is capable of capturing main features of the turbulent flame in a wide range of mixture temperature and equivalence ratios.
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Meng, Nan, i Feng Li. "Large-Eddy Simulations of Unsteady Reaction Flow Characteristics Using Four Geometrical Combustor Models". Aerospace 10, nr 2 (6.02.2023): 147. http://dx.doi.org/10.3390/aerospace10020147.
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Combustion instability constitutes the primary loss source of combustion chambers, gas turbines, and aero engines, and it affects combustion performance or results in a sudden local oscillation. Therefore, this study investigated the factors affecting flame fluctuation on unsteady combustion flow fields through large-eddy simulations. The effects of primary and secondary holes in a triple swirler staged combustor on flame propagation and pressure fluctuation in a combustion field were studied. Moreover, the energy oscillations and dominant frequencies in the combustion field were obtained using the power spectral density technique. The results revealed a variation in the vortex structure and Kelvin–Helmholtz instability in the combustion field, along with a variation in the pressure pulsation during flame propagation under the influence of the primary and secondary hole structures. Additionally, the spatial distributions of pressure oscillation and heat release rate amplitude were obtained, revealing that the foregoing increased owing to the primary and secondary holes in the combustion field, reaching a peak in the shear layer and vortex structure regions.
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Thelen, Bryce C., i Elisa Toulson. "A computational study on the effect of the orifice size on the performance of a turbulent jet ignition system". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 231, nr 4 (20.08.2016): 536–54. http://dx.doi.org/10.1177/0954407016659199.
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Fully three-dimensional computational fluid dynamic simulations with detailed combustion chemistry of a turbulent jet ignition system installed in a rapid compression machine are presented. The turbulent jet ignition system is a prechamber-initiated combustion system intended to allow lean-burn combustion in spark ignition internal-combustion engines. In the presented configuration, the turbulent jet ignition prechamber has a volume that is 2% of the volume of the main combustion chamber in the rapid compression machine and is separated from the main chamber by a nozzle containing a single orifice. Four simulations with orifice diameters of 1.0 mm, 1.5 mm, 2.0 mm, and 3.0 mm respectively are presented in order to demonstrate the effect of the orifice diameter on the combustion behavior of the turbulent jet ignition process. Data generated by the simulations is shown including combustion chamber pressures, temperature fields, jet velocities and mass fraction burn durations. From the combustion pressure trace, the jet velocity, and other field data, five distinct phases of the turbulent jet ignition process are identified. These phases are called the compression phase, the prechamber combustion initiation phase, the cold jet phase, the hot jet phase, and the flow reversal phase. The four simulations show that the orifice diameter of 1.5 mm provides the fastest ignition and the fastest overall combustion as reflected in the 0–10% and 10–90% mass fraction burn duration data generated. Meanwhile, the simulation for the orifice diameter of 1.0 mm produces the highest jet velocity and has the shortest delay between the spark and the exit of a jet of hot gases into the main chamber but produces a slower burn duration than the simulation for the larger orifice diameter of 1.5 mm. The simulations for orifice diameters of 2.0 mm and 3.0 mm demonstrate that the combustion speed is reduced as the orifice diameter increases above 1.5 mm. Finally, a discussion is given which examines the implications that the results generated have in regard to implementation of the turbulent jet ignition system in an internal-combustion engine.
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Zhang, Linqing, Juntao Chang, Wenxiang Cai, Hui Sun i Yingkun Li. "A Preliminary Research on Combustion Characteristics of a Novel-Type Scramjet Combustor". International Journal of Aerospace Engineering 2022 (30.12.2022): 1–18. http://dx.doi.org/10.1155/2022/3930440.
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In this work, a new configuration of strut-based scramjet is proposed, and a series of simulations are conducted to investigate its possibility of practical application. The simulation results are verified via the classical DLR ramjet and an experiment conducted on the connected pipe facility. The inlet area ( A in ) and air intake height ( H ) of the combustor are varied independently to investigate their performance. The results indicate that the flow field and shock wave structure of such engine reveal similar characteristics as the classical DLR engine, and the variation in engine geometry can significantly affect its combustion characteristics. Moreover, the combustion efficiency could be enhanced by 2% as the A in varied from 900π mm2 to 1100π mm2; increasing the air intake path ( H ) to 12 mm can increase the combustion efficiency by 25%. In general, the present work proposes a new geometry of the scramjet combustor; this combustor has possibility of practical application, but a further and detailed investigation is still needed.
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Liu, Hao, Wen Yan Song i Shun Hua Yang. "Large Eddy Simulation of Hydrogen-Fueled Supersonic Combustion with Strut Injection". Applied Mechanics and Materials 66-68 (lipiec 2011): 1769–73. http://dx.doi.org/10.4028/www.scientific.net/amm.66-68.1769.
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In order to obtain more accurate simulation results and properties of combustion in supersonic combustion flow fields, modules of large eddy simulation of reactive turbulent flow and fifth-order WENO scheme was developed. Large eddy simulation of hydrogen-fueled supersonic combustion with strut injection was conducted. Simulations results compare were with experimental measurements, which including wall pressure, velocity, velocity fluctuation and temperature.
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Mahesh, K., G. Constantinescu, S. Apte, G. Iaccarino, F. Ham i P. Moin. "Large-Eddy Simulation of Reacting Turbulent Flows in Complex Geometries". Journal of Applied Mechanics 73, nr 3 (9.11.2005): 374–81. http://dx.doi.org/10.1115/1.2179098.
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Large-eddy simulation (LES) has traditionally been restricted to fairly simple geometries. This paper discusses LES of reacting flows in geometries as complex as commercial gas turbine engine combustors. The incompressible algorithm developed by Mahesh et al. (J. Comput. Phys., 2004, 197, 215–240) is extended to the zero Mach number equations with heat release. Chemical reactions are modeled using the flamelet/progress variable approach of Pierce and Moin (J. Fluid Mech., 2004, 504, 73–97). The simulations are validated against experiment for methane-air combustion in a coaxial geometry, and jet-A surrogate/air combustion in a gas-turbine combustor geometry.
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Chambers, Steven, Horia Flitan, Paul Cizmas, Dennis Bachovchin, Thomas Lippert i David Little. "The Influence of In Situ Reheat on Turbine-Combustor Performance". Journal of Engineering for Gas Turbines and Power 128, nr 3 (1.03.2004): 560–72. http://dx.doi.org/10.1115/1.2135812.
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This paper presents a numerical and experimental investigation of the in situ reheat necessary for the development of a turbine-combustor. The flow and combustion were modeled by the Reynolds-averaged Navier-Stokes equations coupled with the species conservation equations. The chemistry model used herein was a two-step, global, finite rate combustion model for methane and combustion gases. A numerical simulation was used to investigate the validity of the combustion model by comparing the numerical results against experimental data obtained for an isolated vane with fuel injection at its trailing edge. The numerical investigation was then used to explore the unsteady transport phenomena in a four-stage turbine-combustor. In situ reheat simulations investigated the influence of various fuel injection parameters on power increase, airfoil temperature variation, and turbine blade loading. The in situ reheat decreased the power of the first stage, but increased more the power of the following stages, such that the power of the turbine increased between 2.8% and 5.1%, depending on the parameters of the fuel injection. The largest blade excitation in the turbine-combustor corresponded to the fourth-stage rotor, with or without combustion. In all cases analyzed, the highest excitation corresponded to the first blade passing frequency.
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Zhu, Zhouyuan, Canhua Liu, Yajing Chen, Yuning Gong, Yang Song i Junshi Tang. "In-situ Combustion Simulation from Laboratory to Field Scale". Geofluids 2021 (14.12.2021): 1–12. http://dx.doi.org/10.1155/2021/8153583.
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In-situ combustion simulation from laboratory to field scale has always been challenging, due to difficulties in deciding the reaction model and Arrhenius kinetics parameters, together with erroneous results observed in simulations when using large-sized grid blocks. We present a workflow of successful simulation of heavy oil in-situ combustion process from laboratory to field scale. We choose the ongoing PetroChina Liaohe D block in-situ combustion project as a case of study. First, we conduct kinetic cell (ramped temperature oxidation) experiments, establish a suitable kinetic reaction model, and perform corresponding history match to obtain Arrhenius kinetics parameters. Second, combustion tube experiments are conducted and history matched to further determine other simulation parameters and to determine the fuel amount per unit reservoir volume. Third, we upscale the Arrhenius kinetics to the upscaled reaction model for field-scale simulations. The upscaled reaction model shows consistent results with different grid sizes. Finally, field-scale simulation forecast is conducted for the D block in-situ combustion process using computationally affordable grid sizes. In conclusion, this work demonstrates the practical workflow for predictive simulation of in-situ combustion from laboratory to field scale for a major project in China.
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Rashkovskiy, Sergey. "Simulation of Gasless Combustion of Mechanically Activated Solid Powder Mixtures". Advances in Science and Technology 63 (październik 2010): 213–21. http://dx.doi.org/10.4028/www.scientific.net/ast.63.213.
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The direct 3D method of numerical simulation of gasless combustion of mechanically activated solid powder mixtures is developed. The method under consideration falls into three stages. On the first stage, a simulation of mixture structure is performed. An analysis of the structure obtained in simulations is carried out. On the second stage, the thermal conductivity of solid powder mixture is calculated. On the third stage of simulation, the ignition and combustion of each particle of the mixture is considered with taking into account of heat exchange between contacting particles. The results of numerical simulations are represented dynamically and compared with the experimental data, obtained by high-speed digital recording of mechanically activated SHS systems combustion.
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Rimár, Miroslav, Ján Kizek i Andrii Kulikov. "Numerical Modelling of Gaseous Fuel Combustion Process with the Stepwise Redistribution of Enriched Combustion Air". MATEC Web of Conferences 328 (2020): 02001. http://dx.doi.org/10.1051/matecconf/202032802001.
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The authors of this paper present the results of simulations for burner system design changes in the smelting aggregate. Based on the analysis of the existing burner system in the experimental aluminium smelting equipment, changes in the burner design were proposed. The obtained results are presented in tables and figures. The properties of the proposed changes were investigated using the simulation software ANSYS. The simulations confirmed the suitability of the proposed system for shortening the flame length and intensification of the mixing of gaseous media.
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Gonzalez-Juez, Esteban. "Numerical Simulations of Combustion Instabilities in a Combustor with an Augmentor-Like Geometry". Aerospace 6, nr 7 (21.07.2019): 82. http://dx.doi.org/10.3390/aerospace6070082.
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With the goal of assessing the capability of Computational Fluid Dynamics (CFD) to simulate combustion instabilities, the present work considers a premixed, bluff-body-stabilized combustor with well-defined inlet and outlet boundary conditions. The present simulations produce flow behaviors in good qualitative agreement with experimental observations. Notably, the flame flapping and standing acoustic waves seen in the experiments are reproduced by the simulations. Moreover, present predictions for the dominant instability frequency have an error of 7% and those of the rmspressure fluctuations show an error of 16%. In addition, an analysis of simulation results for the limit cycle complements previous experimental analyses by supporting the presence of an active frequency-locking mechanism.
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Tao, Feng, Sukhin Srinivas, Rolf D. Reitz i David E. Foster. "Current status of soot modeling applied to diesel combustion simulations(Diesel Engines, Combustion Modeling I)". Proceedings of the International symposium on diagnostics and modeling of combustion in internal combustion engines 2004.6 (2004): 151–57. http://dx.doi.org/10.1299/jmsesdm.2004.6.151.
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Lipatnikov, Andrei N. "Numerical Simulations of Turbulent Combustion". Fluids 5, nr 1 (10.02.2020): 22. http://dx.doi.org/10.3390/fluids5010022.
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Ahmed, E., i Y. Huang. "Flame volume prediction and validation for lean blow-out of gas turbine combustor". Aeronautical Journal 121, nr 1236 (12.01.2017): 237–62. http://dx.doi.org/10.1017/aer.2016.125.
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ABSTRACTLean Blow-Out (LBO) limits are critically important in the operation of aero engines. Previously, Lefebvre's LBO empirical correlation has been extended to the flame volume concept by the authors. Flame volume takes into account the effects of geometric configuration, spatial interaction of mixing jets, turbulence, heat transfer and combustion processes inside the gas turbine combustion chamber. For these reasons, LBO predictions based on flame volume are more accurate. Although LBO prediction accuracy has improved, it poses a challenge associated with Vfestimation in real gas turbine combustors. This work extends the approach of flame volume prediction based on fuel iterative approximation with cold flow simulations to reactive flow simulations. Flame volume for 11 combustor configurations were simulated and validated against experimental data. To make prediction methodology robust, as required in preliminary design stage, reactive flow simulations were carried out with the combination of presumed Probability Density Function (PDF) and discrete phase model (DPM) in Fluent 15.0 The criterion for flame identification was defined. Two important parameters—critical injection diameter (Dp,crit) and critical temperature (Tcrit)—were identified and their influence on reactive flow simulation was studied for Vfestimation. Results exhibit ±15% error in Vf estimation with experimental data.
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Dinde, Prashant, A. Rajasekaran i V. Babu. "3D numerical simulation of the supersonic combustion of H2". Aeronautical Journal 110, nr 1114 (grudzień 2006): 773–82. http://dx.doi.org/10.1017/s0001924000001640.
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Results from numerical simulations of supersonic combustion of H2 are presented. The combustor has a single stage fuel injection parallel to the main flow from the base of a wedge. The simulations have been performed using FLUENT. Realisable k-ε model has been used for modelling turbulence and single step finite rate chemistry has been used for modelling the H2-Air kinetics. All the numerical solutions have been obtained on grids with average value for wall y+ less than 40. Numerically predicted profiles of static pressure, axial velocity, turbulent kinetic energy and static temperature for both non-reacting as well as reacting flows are compared with the experimental data. The RANS calculations are able to predict the mean and fluctuating quantities reasonably well in most regions of the flow field. However, the single step kinetics predicts heat release much more rapid than what was seen in the experiments. Nonetheless, the overall pressure rise in the combustor due to combustion is predicted well. Also, the k-ε model is not able to predict the fluctuating quantities in the base region of the wedge where there is strong anisotropy in the presence of combustion.
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Kang, Yiqin, Chenlu Wang, Gangyi Fang, Fei Xing i Shining Chan. "Flow and Combustion Characteristics of Wave Rotor–Trapped Vortex Combustor System". Energies 16, nr 1 (28.12.2022): 326. http://dx.doi.org/10.3390/en16010326.
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Breaking through the limit of conventional compression and combustion, wave rotor and trapped vortex combustors are able to improve the thermal efficiency of gas turbines. Detailed two-dimensional numerical simulations based on Ansys Fluent were performed to study the flow and combustion characteristics of the wave rotor–trapped vortex combustor system. The calculated pressure characteristics agree with the experimental results giving a relative error for average pressure of 0.189% at Port 2 and of 0.672% at Port 4. The flow stratification characteristics and the periodic fluctuations were found to benefit the zonal organized combustion in the trapped vortex combustor. For the six cases of different rotor speeds, as the rotor speed increased, the oxygen mass fraction at the combustor inlet rose and then fell. The proportion of exhaust gas recirculation fell at first and then rose, and the combustion mode became unstable with the dominant frequencies of the fluctuations increasing.
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Guo, Kangkang, Yongjie Ren, Yiheng Tong, Wei Lin i Wansheng Nie. "Analysis of self-excited transverse combustion instability in a rectangular model rocket combustor". Physics of Fluids 34, nr 4 (kwiecień 2022): 047104. http://dx.doi.org/10.1063/5.0086226.
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A methane/oxygen mixture is considered to be an appropriate propellant for many future rocket engines due to its practicality and low cost. To better understand the combustion instability in methane/oxygen-fed rocket engines, the spontaneous transverse combustion instability in a rectangular multi-element combustor (RMC) was analyzed both experimentally and numerically. Severe combustion instabilities occurred in the RMC during repeatable hot-fire tests. The physical mechanisms were systematically investigated through numerical simulations based on the stress-blended eddy simulation and flamelet-generated manifolds method with detailed chemical mechanisms (GRI Mech 3.0). The numerical results for the frequency spectrum and spatial modes agree well with the theoretical analysis and experimental data. The driven regions of the combustion instability were identified on both sides of the combustion chamber through a Rayleigh index analysis. The longitudinal pressure oscillations in the oxidizer post were found to be coupled with the transverse pressure waves in the combustion chamber and led to periodic oscillations of the mass flow rate of propellant. Moreover, the mixing was highly enhanced when the pressure wave interacted with walls of the combustion chamber. Therefore, a sudden release of heat occurred. The pressure oscillations were enhanced by pulsated heat release. A closed-loop system with positive feedback associated with periodic oscillations mass flow rate of the propellant, and sudden heat release, was believed to account for the present combustion instability.
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Yuan, Yixiang, Qinghua Zeng, Jun Yao, Yongjun Zhang, Mengmeng Zhao i Lu Zhao. "Improving Blowout Performance of the Conical Swirler Combustor by Employing Two Parts of Fuel at Low Operating Condition". Energies 14, nr 6 (18.03.2021): 1681. http://dx.doi.org/10.3390/en14061681.
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Aiming at the problem of the narrow combustion stability boundary, a conical swirler was designed and constructed based on the concept of fuel distribution. The blowout performance was studied at specified low operating conditions by a combination of experimental testing and numerical simulations. Research results indicate that the technique of the fuel distribution can enhance the combustion stability and widen the boundary of flameout within the range of testing conditions. The increase of the fuel distribution ratio improves the combustion stability but leads to an increase in NOx emission simultaneously. The simulation results show the increase of the fuel distribution ratio causes contact ratio increase in the area of lower reference velocity and gas temperature increase. The increased contact ratio and temperature contribute to the blowout performance enhancement, which is identical to the analysis result of the Damkohler number. The reported work in this paper has potential application value for the development of an industrial burner and combustor with high stability and low NOx emission, especially when the combustion system is required to be stable and efficient at low working conditions.
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Krishnamoorthy, Gautham, i Caitlyn Wolf. "Assessing the Role of Particles in Radiative Heat Transfer during Oxy-Combustion of Coal and Biomass Blends". Journal of Combustion 2015 (2015): 1–15. http://dx.doi.org/10.1155/2015/793683.
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This study assesses the required fidelities in modeling particle radiative properties and particle size distributions (PSDs) of combusting particles in Computational Fluid Dynamics (CFD) investigations of radiative heat transfer during oxy-combustion of coal and biomass blends. Simulations of air and oxy-combustion of coal/biomass blends in a 0.5 MW combustion test facility were carried out and compared against recent measurements of incident radiative fluxes. The prediction variations to the combusting particle radiative properties, particle swelling during devolatilization, scattering phase function, biomass devolatilization models, and the resolution (diameter intervals) employed in the fuel PSD were assessed. While the wall incident radiative flux predictions compared reasonably well with the experimental measurements, accounting for the variations in the fuel, char and ash radiative properties were deemed to be important as they strongly influenced the incident radiative fluxes and the temperature predictions in these strongly radiating flames. In addition, particle swelling and the diameter intervals also influenced the incident radiative fluxes primarily by impacting the particle extinction coefficients. This study highlights the necessity for careful selection of particle radiative property, and diameter interval parameters and the need for fuel fragmentation models to adequately predict the fly ash PSD in CFD simulations of coal/biomass combustion.
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Alhumairi, Mohammed, i Özgür Ertunç. "Active-grid turbulence effect on the topology and the flame location of a lean premixed combustion". Thermal Science 22, nr 6 Part A (2018): 2425–38. http://dx.doi.org/10.2298/tsci170503100a.
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Lean premixed combustion under the influence of active-grid turbulence was computationally investigated, and the results were compared with experimental data. The experiments were carried out to generate a premixed flame at a thermal load of 9 kW from a single jet flow combustor. Turbulent combustion models, such as the coherent flame model and turbulent flame speed closure model were implemented for the simulations performed under different turbulent flow conditions, which were specified by the Reynolds number based on Taylor?s microscale, the dissipation rate of turbulence, and turbulent kinetic energy. This study shows that the applied turbulent combustion models differently predict the flame topology and location. However, similar to the experiments, simulations with both models revealed that the flame moves toward the inlet when turbulence becomes strong at the inlet, that is, when Re? at the inlet increases. The results indicated that the flame topology and location in the coherent flame model were more sensitive to turbulence than those in the turbulent flame speed closure model. The flame location behavior on the jet flow combustor significantly changed with the increase of Re?.
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Geigle, Klaus Peter, Wolfgang Meier, Manfred Aigner, Chris Willert, Marc Jarius, Patrick Schmitt i Bruno Schuermans. "Phase-Resolved Laser Diagnostic Measurements of a Downscaled, Fuel-Staged Gas Turbine Combustor at Elevated Pressure and Comparison to LES Predictions". Journal of Engineering for Gas Turbines and Power 129, nr 3 (19.09.2006): 680–87. http://dx.doi.org/10.1115/1.2718222.
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A technical gas turbine combustor has been studied in detail with optical diagnostics for validation of large-eddy simulations (LES). OH* chemiluminescence, OH laser-induced fluorescence (LIF) and particle image velocimetry (PIV) have been applied to stable and pulsating flames up to 8 bar. The combination of all results yielded good insight into the combustion process with this type of burner and forms a database that was used for the validation of complex numerical combustion simulations. LES, including radiation, convective cooling, and air cooling, were combined with a reduced chemical scheme that predicts NOx emissions. Good agreement of the calculated flame position and shape with experimental data was found.
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Li, Jun, Meilin Zhu, Chang Geng, Yingjie Yuan, Zewei Fu, Shu Yan, Rou Feng i in. "A Molecular Understanding of the Flame Retardant Mechanism of Zinc Stannate/Polypropylene Composites via ReaxFF Simulations". Inorganics 11, nr 6 (27.05.2023): 233. http://dx.doi.org/10.3390/inorganics11060233.
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As an important new flame retardant, zinc stannate (ZS) shows wide application prospects due to its many advantages. However, the flame retardant mechanism of composites made with polymer combined with ZS is still unclear. In particular, there is a lack of molecular level description of the micro-scale flame retardant mechanism. The combustion mechanism through molecular simulation technology has become an important research paradigm in the field of fire, which can provide new insights for the development of new materials. This work studied the flame retardant mechanism of composites consistent with polypropylene (PP) and ZS using reactive force field molecular dynamics (ReaxFF MD) simulations. A new force field incorporating Sn/Zn/C/H/O components for ZS/PP composites combustion reactions was developed. Twenty different ZS/PP composites were analyzed for their combustion reactions at various temperatures. To investigate the flame retarding mechanism of ZS in composites, the evolutions of reactants, products, and reaction intermediates at the molecular scale were collected. It was revealed that the combustion temperature controlled the degree of oxidation by regulating the consumption of molecular oxygen during PP cracking. An increased combustion temperature reduced the oxygen consumption rate and overall oxygen consumption. As the PP component of composites exceeded 56%, oxygen consumption increased. Evolutions for carbon-containing intermediates and the products in combustions of PP/ZS composites were analyzed. The small carbon-based fragments were more likely to be produced for composites with low PP contents at high temperatures. These results are beneficial to design ZS/PP composites as flame retardant materials.
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Wang, Xinyan, i Hua Zhao. "Modelling Study of Cycle-To-Cycle Variations (CCV) in Spark Ignition (SI)-Controlled Auto-Ignition (CAI) Hybrid Combustion Engine by Using Reynolds-Averaged Navier–Stokes (RANS) and Large Eddy Simulation (LES)". Energies 15, nr 12 (20.06.2022): 4478. http://dx.doi.org/10.3390/en15124478.
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The spark ignition (SI)-controlled auto-ignition (CAI) hybrid combustion is characterized by early flame propagation combustion and subsequent auto-ignition combustion. The application of combined SI–CAI hybrid combustion can be used to effectively extend the operating range of CAI combustion and achieve smooth transitions between SI and CAI combustion modes. However, SI–CAI hybrid combustion can produce significant cycle-to-cycle variations (CCV). In order to better understand the sources of CCV and minimize its occurrence, the large eddy simulation (LES) and Reynolds-averaged Navier–Stokes (RANS) approaches were employed in this study to model and understand the cyclic phenomenon of SI–CAI hybrid combustion. Both the multi-cycle LES and RANS simulations were analyzed against the experimental measurements in a single cylinder engine at 1500 rpm and a 5.43 bar average indicated the mean effective pressure (IMEP). The detailed analysis of the in-cylinder pressure traces, IMEP, in-cylinder peak pressure (PP), peak pressure rise rate (PPRR) and the crank angles with fuel mass burned fraction at 10%, 50%, 90% and mode transition was performed. The results indicate that overall, the adopted LES simulations could effectively predict the cyclic variations in the hybrid combustion observed in the experiments, while the RANS simulations failed to reproduce the cyclic characteristics at the chosen engine operating conditions. Based on the LES results, the correlation and visualization studies indicate that the cyclic variations in the local velocity around the spark plug lead to the variations in the early flame propagation, which in turn produce temperature fluctuations among the cycles and result in greater variations in the subsequent auto-ignition combustion events.
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Saputro, Herman, Heri Juwantono, Husin Bugis, Danar Susilo Wijayanto, Laila Fitriana, Valiant Lukad Perdana, Aris Purwanto i in. "Numerical simulation of flame stabilization in meso-scale vortex combustion". MATEC Web of Conferences 197 (2018): 08005. http://dx.doi.org/10.1051/matecconf/201819708005.
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A meso-scale vortex combustor has been designed in order to common flame quenching problems in meso/micro scale burning. Numerical simulations using Computational Fluid Dynamic (CFD) Ansys Release 19.0 Academic program was performed to determine a stable combustion flame. Combustor chamber made from two steps, first step diameter 6 mm with 4 mm depth, second step diameter size 8mm with 5 mm depth. This simulation used mixture of propane fuel-air. The fuel is fed through two channels of fuel inlet with 2 mm diameter. The variable of fuel flow rate was investigated in order to get the boundary of extinction limit and blow off limit of flame (stable flame region). The results show that the flame stable limit by using meso-scale vortex combustor more widely than other types of micro combustor. Therefore, the meso-scale vortex combustor that was developed could be used to overcome the flame quenching problems.
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Pandey, Krishna Murari, i Sukanta Roga. "CFD Analysis of Hypersonic Combustion of H2-Fueled Scramjet Combustor with Cavity Based Fuel Injector at Flight Mach 6". Applied Mechanics and Materials 656 (październik 2014): 53–63. http://dx.doi.org/10.4028/www.scientific.net/amm.656.53.
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This paper presents a numerical analysis of the inlet-combustor interaction and flow structure through a scramjet engine at a flight Mach 6 with cavity based injection. Fuel is injected at supersonic speed of Mach 2 through a cavity based injector. These numerical simulations are aimed to study the flow structure, supersonic mixing and combustion for cavity based injection. For the reacting cases, the shock wave pattern is modified which is due to the strong heat release during combustion process. The shock structure and combustion phenomenon are not only affected by the geometry but also by the flight Mach number and the trajectory. The inlet-combustor interaction is studied with a fix location of cavity based injection. Cavity is of interest because recirculation flow in cavity would provide a stable flame holding while enhancing the rate of mixing or combustion. The cavity effect is discussed from a view point of mixing and combustion efficiency.
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Chow, P. H. P., H. C. Watson i T. Wallis. "Combustion in a high-speed rotary valve spark-ignition engine". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 221, nr 8 (1.08.2007): 971–90. http://dx.doi.org/10.1243/09544070jauto407.
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The current paper describes a study of combustion in the Bishop rotary valve engine by means of computation simulations. The combustion model was developed for this research at speeds up to 18 000 r/min and the results from the simulation were compared with experimental data. Sensitivity studies were performed in order to investigate the parametric effects on the combustion simulation of the engine. The major finding of this study was that convection of the flame kernels occurs and has a strong influence on the performance of the engine. The results indicated some insights as to how the combustion process of the engine can be improved.
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Meng, Nan, i Feng Li. "Large-eddy simulation of unstable non-reactive flow in a swirler combustor". Physics of Fluids 34, nr 11 (listopad 2022): 114107. http://dx.doi.org/10.1063/5.0122462.
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A comprehensive study on the influence of the unsteady non-reactive flow characteristics of turbulent flow in a three-stage swirl combustion chamber using power spectral density methods was conducted using large eddy simulations. The results demonstrated that instabilities were observed owing to large-scale vortex structures and periodic oscillations of the non-reactive flow. The boundary of the central recirculation zone (shear layers) enhanced the instability of the Helmholtz mode in the combustor. By considering the power spectral density of different monitoring points, the instability characteristics were accurately determined according to the oscillatory energy obtained in the non-reactive flow field. Large-scale vortex structures and periodic oscillations were the main reasons for the unsteady characteristics of the non-reactive flow field. The large eddy simulation results were compared with the experimental data, and the average absolute relative deviation between the large eddy simulation and experimental velocity components in the combustor were less than 12.04%. The results provide valuable insights into the unstable non-reaction flow characteristics in the combustion chamber.
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Hendricks, R. C., D. T. Shouse, W. M. Roquemore, D. L. Burrus, B. S. Duncan, R. C. Ryder, A. Brankovic, N. S. Liu, J. R. Gallagher i J. A. Hendricks. "Experimental and Computational Study of Trapped Vortex Combustor Sector Rig with High-Speed Diffuser Flow". International Journal of Rotating Machinery 7, nr 6 (2001): 375–85. http://dx.doi.org/10.1155/s1023621x0100032x.
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The Trapped Vortex Combustor (TVC) potentially offers numerous operational advantages over current production gas turbine engine combustors. These include lower weight, lower pollutant emissions, effective flame stabilization, high combustion efficiency, excellent high altitude relight capability, and operation in the lean burn or RQL modes of combustion. The present work describes the operational principles of the TVC, and extends diffuser velocities toward choked flow and provides system performance data. Performance data include EINOx results for various fuel-air ratios and combustor residence times, combustion efficiency as a function of combustor residence time, and combustor lean blow-out (LBO) performance. Computational fluid dynamics (CFD) simulations using liquid spray droplet evaporation and combustion modeling are performed and related to flow structures observed in photographs of the combustor. The CFD results are used to understand the aerodynamics and combustion features under different fueling conditions. Performance data acquired to date are favorable compared to conventional gas turbine combustors. Further testing over a wider range of fuel-air ratios, fuel flow splits, and pressure ratios is in progress to explore the TVC performance. In addition, alternate configurations for the upstream pressure feed, including bi-pass diffusion schemes, as well as variations on the fuel injection patterns, are currently in test and evaluation phases.
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Kurose, Ryoichi, Hiroaki Watanabe i Hisao Makino. "Numerical Simulations of Pulverized Coal Combustion". KONA Powder and Particle Journal 27 (2009): 144–56. http://dx.doi.org/10.14356/kona.2009014.
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Masri, Assaad R., Mohy Mansour i Andrea D'Anna. "Towards Improving Simulations of Combustion Processes". Combustion Theory and Modelling 21, nr 1 (2.01.2017): 1. http://dx.doi.org/10.1080/13647830.2017.1296683.
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Chen, Yen-Sen, T. H. Chou, B. R. Gu, J. S. Wu, Bill Wu, Y. Y. Lian i Luke Yang. "Multiphysics simulations of rocket engine combustion". Computers & Fluids 45, nr 1 (czerwiec 2011): 29–36. http://dx.doi.org/10.1016/j.compfluid.2010.09.010.
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Di Sarli, Valeria, Marco Trofa i Almerinda Di Benedetto. "A Novel Catalytic Micro-Combustor Inspired by the Nasal Geometry of Reindeer: CFD Modeling and Simulation". Catalysts 10, nr 6 (31.05.2020): 606. http://dx.doi.org/10.3390/catal10060606.
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A three-dimensional CFD model of a novel configuration of catalytic micro-combustor inspired by the nasal geometry of reindeer was developed using the commercial code ANSYS Fluent 19.0. The thermal behavior of this nature-inspired (NI) configuration was investigated through simulations of lean propane/air combustion performed at different values of residence time (i.e., inlet gas velocity) and (external convective) heat transfer coefficient. Simulations at the same conditions were also run for a standard parallel-channel (PC) configuration of equivalent dimensions. Numerical results show that the operating window of stable combustion is wider in the case of the NI configuration. In particular, the blow-out behavior is substantially the same for the two configurations. Conversely, the extinction behavior, which is dominated by competition between the heat losses towards the external environment and the heat produced by combustion, differs. The NI configuration exhibits a greater ability than the PC configuration to keep the heat generated by combustion trapped inside the micro-reactor. As a consequence, extinction occurs at higher values of residence time and heat transfer coefficient for this novel configuration.
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Danaila, Sterian, i Constantin Leventiu. "On the Hybrid Combustion Instability". Applied Mechanics and Materials 555 (czerwiec 2014): 72–77. http://dx.doi.org/10.4028/www.scientific.net/amm.555.72.
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In the present paper, a combined method of large eddy simulations for non-premixed combustion in a turbulent flow coupled with proper orthogonal decomposition of instantaneous velocity, pressure and temperature fields is developed in order to identify the effect of coherent structure and to obtain a reduced order model for control model. First we investigate the reacting flow using Large Eddy Simulations technique. This physical model is pertinent to internal flows inside the hybrid rocket motors. The turbulence-combustion interaction is based on a combination of finite rate/eddy dissipation model applied to a reduced chemical mechanism with four reactions. Next, the paper refers to the derivation of a Reduced Order Model (ROM) for the same problem, based on the Proper Orthogonal Decomposition (POD) technique. ROMs are used to obtain fast and accurate results, needed in the areas of flow control. The flow and thermal fields obtained with ROMs are compared with the ones obtained from the full simulation and an analysis on the number of modes required to achieve the desired accuracy is presented. Finally, a static control technique is proposed.
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Sui, Wenbo, i Carrie M. Hall. "Combustion phasing modeling and control for compression ignition engines with high dilution and boost levels". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 233, nr 7 (1.08.2018): 1834–50. http://dx.doi.org/10.1177/0954407018790176.
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Because fuel efficiency is significantly affected by the timing of combustion in internal combustion engines, accurate control of combustion phasing is critical. In this paper, a nonlinear combustion phasing model is introduced and calibrated, and both a feedforward model–based control strategy and an adaptive model–based control strategy are investigated for combustion phasing control. The combustion phasing model combines a knock integral model, burn duration model, and a Wiebe function to predict the combustion phasing of a diesel engine. This model is simplified to be more suitable for combustion phasing control and is calibrated and validated using simulations and experimental data that include conditions with high exhaust gas recirculation fractions and high boost levels. Based on this model, an adaptive nonlinear model–based controller is designed for closed-loop control, and a feedforward model–based controller is designed for open-loop control. These two control approaches were tested in simulations. The simulation results show that during transient changes, the CA50 (the crank angle at which 50% of the mass of fuel has burned) can reach steady state in no more than five cycles and the steady-state errors are less than ±0.1 crank angle degree for adaptive control and less than ±0.5 crank angle degree for feedforward model–based control.
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Shibata, Gen, Kohei Yamamoto, Mikito Saito, Yuto Inoue, Yasumasa Amanuma i Yoshimitsu Kobashi. "Optimization of combustion noise and thermal efficiency in diesel engines over a wide speed and load operational range". International Journal of Engine Research 21, nr 4 (15.08.2019): 698–712. http://dx.doi.org/10.1177/1468087419866069.
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Pre-mixed diesel combustion has the potential of offering high thermal efficiency with low emissions; however, this may result in loud combustion noise because of the high maximum rate of pressure rise. Combustion noise and thermal efficiency work in a trade-off relation, and it has not been possible to achieve high thermal efficiency with low combustion noise, so far. Our laboratory has worked on combustion noise simulations calculated from the heat release history, and it is now possible to calculate a heat release shape for high thermal efficiency with low combustion noise. In this article, the objective of the research is the reduction of combustion noise by multiple fuel injections with high indicated thermal efficiency for a wide range of engine speeds and loads. The engine employed in the simulations and experiments is a supercharged, single-cylinder direct-injection diesel engine, with a high-pressure common rail fuel injection system. The heat release is approximated by Wiebe functions, and the combustion noise and indicated thermal efficiency are calculated in simulations. The engine operational range was divided into 12 conditions, four engine speed conditions each at three engine load conditions, and the optimum heat release shape for low combustion noise with high indicated thermal efficiency was calculated by a genetic-based algorithm method. The parameters for the genetic-based algorithm simulation were the number of injections, each injection timing, the heating value in each heat release, and the combustion period of each injection. The optimum heat release shape is a delta triangle (Δ)-shaped heat release (the heat release increase in the expansion stroke) with a high degree of constant volume for all conditions; however, the optimum number of heat releases and the injection timing are different depending on the engine speed and load conditions. The simulated results were confirmed by engine tests.
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Ashrul Ishak, Mohamad Shaiful, Mohd Amirul Amin Arizal, Mohammad Nazri Mohd Jaafar, A. R. Norwazan i Ismail Azmi. "Numerical Investigation of Combustion Performance Utilizing Envo-Diesel Blends". Advanced Materials Research 647 (styczeń 2013): 822–27. http://dx.doi.org/10.4028/www.scientific.net/amr.647.822.
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Alternative fuel and renewable energy is needed to fulfill the energy demand of the world. The use of envo-diesel fuels for power generation seems a viable solution for the problems of decreasing fossil-fuel reserves and environmental concerns. The use of envo-diesel in gas turbines would extend this application to power generation field. Envo-diesel is considered as better option because of its environmental friendly characteristics while giving almost the same functional properties like a fossil fuels. The gas turbine combustion performance that utilizes palm envo-diesel fuel is investigated. This study is to perform a detailed simulation of combustion and thermal flow behaviors inside the combustor. The simulations are conducted using the commercial Computational Fluid Dynamics (CFD) package software to determine the spray flames and combustion characteristics of commercial diesel fuel, envo-E5 and envo-E10. The diameter and temperature of the fuel droplets; and temperature contour, mass fraction of diesel and mass fraction of carbon dioxide (CO2) of the combustor were obtained for commercial diesel fuel, envo-E5 and envo-E10. Diesel fuel displayed higher rates of droplet evaporation compared to E5 and E10 with SMD differential about 30 to 40 μm while mass fraction for E5 and E10 slightly lower than conventional diesel.
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Menon, Suresh, i Wen-Huei Jou. "Large-Eddy Simulations of Combustion Instability in an Axisymmetric Ramjet Combustor". Combustion Science and Technology 75, nr 1-3 (styczeń 1991): 53–72. http://dx.doi.org/10.1080/00102209108924078.
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Jovanovic, Rastko, Krzysztof Strug, Bartosz Swiatkowski, Sławomir Kakietek, Krzysztof Jagiełło i Dejan Cvetinovic. "Experimental and numerical investigation of flame characteristics during swirl burner operation under conventional and oxy-fuel conditions". Thermal Science 21, nr 3 (2017): 1463–77. http://dx.doi.org/10.2298/tsci161110325j.
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Oxy-fuel coal combustion, together with carbon capture and storage or utilization, is a set of technologies allowing to burn coal without emitting globe warming CO2. As it is expected that oxy-fuel combustion may be used for a retrofit of existing boilers, development of a novel oxy-burners is very important step. It is expected that these burners will be able to sustain stable flame in oxy-fuel conditions, but also, for start-up and emergency reasons, in conventional, air conditions. The most cost effective way of achieving dual-mode boilers is to introduce dual-mode burners. Numerical simulations allow investigation of new designs and technologies at a relatively low cost, but for the results to be trustworthy they need to be validated. This paper proposes a workflow for design, modeling, and validation of dual-mode burners by combining experimental investigation and numerical simulations. Experiments are performed with semi-industrial scale burners in 0.5 MWt test facility for flame investigation. Novel CFD model based on ANSYS FLUENT solver, with special consideration of coal combustion process, especially regarding devolatilization, ignition, gaseous and surface reactions, NOx formation, and radiation was suggested. The main model feature is its ability to simulate pulverized coal combustion under different combusting atmospheres, and thus is suitable for both air and oxy-fuel combustion simulations. Using the proposed methodology two designs of pulverized coal burners have been investigated both experimentally and numerically giving consistent results. The improved burner design proved to be a more flexible device, achieving stable ignition and combustion during both combustion regimes: conventional in air and oxy-fuel in a mixture of O2 and CO2 (representing dry recycled flue gas with high CO2 content). The proposed framework is expected to be of use for further improvement of multi-mode pulverized fuel swirl burners but can be also used for independent designs evaluation.
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Stęchły, Katarzyna, Gabriel Wecel i Derek B. Ingham. "CFD modelling of air and oxy-coal combustion". International Journal of Numerical Methods for Heat & Fluid Flow 24, nr 4 (29.04.2014): 825–44. http://dx.doi.org/10.1108/hff-02-2013-0066.
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Purpose – The main goal of this work was the CFD analysis of air and oxy-coal combustion, in order to develop a validated with experimental measurements model of the combustion chamber. Moreover, the purpose of this paper is to provide information about limitations of the sub-models implemented in commercial CFD code ANSYS Fluent version 13.0 for the oxy-coal combustion simulations. The influence of implementation of the weighted sum of gray gas model (WSGGM) with coefficients updated to oxy-coal combustion environment has been investigated. Design/methodology/approach – The sub-models validated with experimental measurements model for the air combustion has been used to predict the oxy-coal combustion case and subsequently the numerical solutions have been compared with the experimental data, which enclose the surface incident radiation (SIR) and the flue gas temperature. To improve the numerical prediction of the oxy-coal combustion process the own routine for calculating properties of the oxy-combustion product has been implemented. Findings – The results of numerical simulation of combustion in the air environment fitted within the experimental measurements accuracy. However, the air combustion sub-models implemented for the oxy-coal combustion simulations does not predict the SIR within the experimental data accuracy. The implementation of own routine, which uses the coefficients calculated for oxy-coal combustion environment shows improvement in numerical prediction of oxy-coal combustion. Originality/value – The radiative properties of gases in the combustion chamber during oxy-coal combustion calculated using the WSGGM implemented in ANSYS Fluent 13.0 do not predict the SIR within experimental measurement accuracy, however, implementation of WSGGM with updated coefficients provide a reasonable improvement in numerical prediction of SIR in the oxy-coal combustion.
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Jin, Xuan, Chibing Shen, Rui Zhou i Xinxin Fang. "Effects of LOX Particle Diameter on Combustion Characteristics of a Gas-Liquid Pintle Rocket Engine". International Journal of Aerospace Engineering 2020 (15.09.2020): 1–16. http://dx.doi.org/10.1155/2020/8867199.
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LOX/GCH4 pintle injector is suitable for variable-thrust liquid rocket engines. In order to provide a reference for the later design and experiments, three-dimensional numerical simulations with the Euler-Lagrange method were performed to study the effect of the initial particle diameter on the combustion characteristics of a LOX/GCH4 pintle rocket engine. Numerical results show that, as the momentum ratio between the radial LOX jet and the axial gas jet is 0.033, the angle between the LOX particle trace and the combustor axial is very small. Due to the large recirculation zones, premixed combustion mainly occurs in the injector wake region. As the initial LOX particle diameter increases, the LOX evaporation rate and the combustion efficiency decrease until the combustion terminates with the initial LOX particle diameter greater than 110 μm. The oscillation amplitude of the combustor pressure increases significantly along with the increase of the initial LOX particle diameter, and the low-frequency unstable combustion occurs when the initial LOX particle diameter exceeds 60 μm. The combustor pressure oscillation at about 40 Hz couples with the swinging process of spray and flame, while the unsteady LOX evaporation amplifies the combustor pressure oscillations at 80 Hz and its harmonic frequency.
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Liou, Tong-Miin, Po-Wen Hwang, Yi-Chen Li i Chia-Yen Chan. "Flame Stability Analysis of Turbulent Non-Premixed Reacting Flow in a Simulated Solid-Fuel Ramjet Combustor". Journal of Mechanics 18, nr 1 (marzec 2002): 43–51. http://dx.doi.org/10.1017/s172771910000201x.
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ABSTRACTTo investigate the flame stability in a solid-fuel ramjet combustor, time-accurate calculations using a compressible flow solver with a modified Godunov flux-splitting scheme have been performed on high Reynolds number turbulent non-premixed reacting flows over a backward-facing step with mass bleed on one wall. The combustion process considered was a one-step, irreversible, and finite rate chemical reaction. The numerical results for reacting flows show that the two-dimensional (2-D) simulations can provide reasonable predictions on the dimensionless particle number decay rate and residence time in the flame holding recirculation zone, evolutions of both axial and transverse mean velocity profiles, and critical characteristic exhaust velocity separating the sustained combustion from the non-sustained combustion. In addition to the validation of 2-D reacting flow calculations, two- and three-dimensionally computed mean-velocity profiles are compared with existing experimental data for isothermal flows to check the suitability of 2-D simulations on capturing the large-scale mean flows.
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Huang, Y. L., H. R. Shiu, S. H. Chang, W. F. Wu i S. L. Chen. "Comparison of Combustion Models in Cleanroom Fire". Journal of Mechanics 24, nr 3 (wrzesień 2008): 267–75. http://dx.doi.org/10.1017/s172771910000232x.
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AbstractIn this paper, the cleanroom fire simulation in a semi-conductor factory is investigated by using the commercial computational fluid dynamics (CFD) code. We using three different combustion models in the fire simulation. The combustion models including the volume heat source (VHS) model, the eddy break-up (EBU) model and the presumed probability density function (prePDF) model are considered to predict the cleanroom fire. The turbulence models coupled with different combustion models, while the radiation model is coupled with the turbulent combustion processes. Additionally, the discrete transfer radiation method (DTRM) is used in the global radiation heat exchange. For the fire simulation, the different combustion models are evaluated for their performance and compared with the experimental data from the literature to verify. Thus, these numerical simulations can be adopted as a useful tool to design and optimize the smoke control strategy in cleanroom fire.
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Menon, S. "Subgrid combustion modelling for large-eddy simulations". International Journal of Engine Research 1, nr 2 (1.04.2000): 209–27. http://dx.doi.org/10.1243/1468087001545146.
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Next-generation gas turbine and internal combustion engines are required to reduce pollutant emissions significantly and also to be fuel efficient. Accurate prediction of pollutant formation requires proper resolution of the spatio-temporal evolution of the unsteady mixing and combustion processes. Since conventional steady state methods are not able to deal with these features, methodology based on large-eddy simulations (LESs) is becoming a viable choice to study unsteady reacting flows. This paper describes a new LES methodology developed recently that has demonstrated a capability to simulate reacting turbulent flows accurately. A key feature of this new approach is the manner in which small-scale turbulent mixing and combustion processes are simulated. This feature allows proper characterization of the effects of both large-scale convection and small-scale mixing on the scalar processes, thereby providing a more accurate prediction of chemical reaction effects. LESs of high Reynolds number premixed flames in the flamelet regime and in the distributed reaction regime are used to describe the ability of the new subgrid combustion model.
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Hegde, N., I. Han, T. W. Lee i R. P. Roy. "Flow and Heat Transfer in Heat Recovery Steam Generators". Journal of Energy Resources Technology 129, nr 3 (24.03.2007): 232–42. http://dx.doi.org/10.1115/1.2751505.
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Computational simulations of flow and heat transfer in heat recovery steam generators (HRSGs) of vertical- and horizontal-tube designs are reported. The main objective of the work was to obtain simple modifications of their internal configuration that render the flow of combustion gas more spatially uniform. The computational method was validated by comparing some of the simulation results for a scaled-down laboratory model with experimental measurements in the same. Simulations were then carried out for two plant HRSGs—without and with the proposed modifications. The results show significantly more uniform combustion gas flow in the modified configurations. Heat transfer calculations were performed for one superheater section of the vertical-tube HRSG to determine the effect of the configuration modification on heat transfer from the combustion gas to the steam flowing in the superheater tubes.
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Grimm, Felix, Jürgen Dierke, Roland Ewert, Berthold Noll i Manfred Aigner. "Modelling of combustion acoustics sources and their dynamics in the PRECCINSTA burner test case". International Journal of Spray and Combustion Dynamics 9, nr 4 (7.07.2017): 330–48. http://dx.doi.org/10.1177/1756827717717390.
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A stochastic, hybrid computational fluid dynamics/computational combustion acoustics approach for combustion noise prediction is applied to the PRECCINSTA laboratory scale combustor (prediction and control of combustion instabilities in industrial gas turbines). The numerical method is validated for its ability to accurately reproduce broadband combustion noise levels from measurements. The approach is based on averaged flow field and turbulence statistics from computational fluid dynamics simulations. The three-dimensional fast random particle method for combustion noise prediction is employed for the modelling of time-resolved dynamics of sound sources and sound propagation via linearised Euler equations. A comprehensive analysis of simulated sound source dynamics is carried out in order to contribute to the understanding of combustion noise formation mechanisms. Therefrom gained knowledge can further on be incorporated for the investigation of onset of thermoacoustic phenomena. The method-inherent stochastic Langevin ansatz for the realisation of turbulence related source decay is analysed in terms of reproduction ability of local one- and two-point statistical input and therefore its applicability to complex test cases. Furthermore, input turbulence statistics are varied, in order to investigate the impact of turbulence on the resulting sound pressure spectra for a swirl stabilised, technically premixed combustor.