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AIAA SciTech Forum and Exposition
This paper numerically predicts the forced heat release responses of a lean premixed bluff-body stabilized ethylene/air flame, using hybrid Stress-Blended Eddy Simulation (SBES) turbulence model and Flamelet Generated Manifold (FGM) combustion model. The unforced flow field and flame structures are firstly simulated and validated against available experimental data. The forced heat release rate responses of the flame to upstream harmonic velocity fluctuations are then computed and accounted for using the weakly nonlinear Flame Describing Function (FDF), which again match well the experimental measurements. These indicate that the use of SBES and FGM models can accurately predict the forced flame responses and the resulted FDFs, which can be applied to predicting the thermoacoustic instability in realistic gas turbine combustors.
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ASME Turbo Expo 2020
Accurate numerical prediction of surface heat transfer in the presence of film cooling within aero-engine sub-components, such as blade effusion holes and combustor liners, has long been a goal of the aero-engine industry. It requires accurate simulation of the turbulent mixing and reaction processes between freestream and the cooling flow. In this study, the Stress Blended Eddy Simulation (SBES) turbulence model is used together with the Flamelet Generated Manifold (FGM) combustion model to calculate the surface heat flux upstream and downstream of an effusion cooling hole. The SBES model employs a blending function to automatically switch between RANS and LES based on the local flow features, and thus significantly reduces the computational cost compared to a full LES simulation. All simulations are run using ANSYS Fluent, a commercial finite-volume CFD solver. The test case corresponds to an experimental rig run at MIT, which is essentially a flat plate brushed by a uniform freestream of argon with ethylene seeded inside, and is cooled by either a reacting air or non-reacting nitrogen jet inclined at 35 degrees to the freestream. Calculations are performed for both reacting and non-reacting jet cooling cases across a range of jet-to-stream blowing ratios, and compared with the experimental data. The effects of mesh resolution are also investigated. Calculations are also performed across a range of Damkohler number (i.e. flow to chemical time ratio) from zero to 30, with unity blowing ratio, and the differences in the maximum surface heat flux magnitude in the reacting and non-reacting cases at a specific location downstream of the hole are investigated. Results from these analyses show good correlation with the experimental heat flux data upstream and downstream of the cooling hole, including the heat flux augmentation due to local reaction. Results from the Damkohler number sweep also show a good match with the experimental data across the range investigated.
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Thesis by M.I. Resor at Wright State University, 2014 83 pages german keywords: Wankelmotor / Kreiskolbenmotor English Keywords: Wankel Engine / Wankel Rotary Engine / Rotary Piston Engine / Rotary Combustion Engine > Chapter 1: Introduction Background 1 » Rotary Engine 1 » High Temperature Combustion (SI and CI) 3 » Low Temperature Combustion (HCCI/PCCI) 5 » Research Objective 7 » Methodology 8 » Literature Review 9 » Thesis Outline 11 > Chapter 2: Validation 12 » Z19DTH - Piston Engine 12 » Modeling and Meshing 13 » Solver Models and Numerical Settings 15 » Combustion 16 » Turbulence and Wall Heat Flux 17 » Results 17 > Chapter 3: Rotary Engine Model 19 » Modeling and Meshing 19 » Boundary and Initial Conditions 22 » Solver Settings 24 > Chapter 4: Parametric Study on LTC Performance 26 » Rotary Homogeneous Charge Compression Ignition (HCCI) 26 » Parameters 26 » Responses 27 » Held Constant Factors 28 » Results of 3 3 Factorial 28 » Best Fit Case Results from 3 3 Factorial 40 » Equivalence Ratio Single Factor Fitting 41 » Best Fit Case Equivalence Ratio Single Factor Fitting 44 > Chapter 5: Conclusions 48 > Chapter 6: Future Work 50 > References 52 > Appendix 55 » Heat Flux Function UDF 55 » Diagrams » Temperatures + Pressures 58
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Flow, Turbulence and Combustion
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