Turbulent Spray Combustion Modeling Using Various Kinetic Solvers and Turbulence Models

Turbulent spray combustion of n-dodecane was modeled at relevant engine conditions using two combustion models (direct integration of chemistry (DIC) and flamelet generated manifolds (FGM)) and multifidelity turbulence models (dynamic structure large eddy simulation (LES) and renormalization group (RNG) Reynolds-averaged Naiver–Stokes (RANS)). The main objective of this work is to study the effect of various combustion and turbulence models on spray behavior and quantify these effects. To reach these objectives, a recently developed kinetic mechanism and well-established spray models were utilized for the three-dimensional turbulent spray simulation at various combustion chamber initial gas temperature and pressure conditions. Fine mesh with a size of 31 μm was utilized to resolve small eddies in the periphery of the spray. In addition, a new methodology for mesh generation was proposed and investigated to simulate the measured data fluctuation in the CFD domain. The pressure-based ignition delay, flame lift-off length (LOL), species concentrations, spray, and jet penetrations were modeled and compared with measured data. Differences were observed between various combustion and turbulence models in predicting the spray characteristics. However, these differences are within the uncertainties, error, and variations of the measured data.

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Study of Turbulent Spray Combustion of N-Dodecane Fuel

Volume 2: Emissions Control Systems; Instrumentation, Controls, and Hybrids; Numerical Simulation; Engine Design and Mechanical Development ◽

10.1115/icef2015-1018 ◽

2015 ◽

Cited By ~ 1

Author(s):

O. Samimi Abianeh

Keyword(s):

Combustion Chamber ◽

Ignition Delay ◽

Pressure Rise ◽

Chamber Pressure ◽

Spray Combustion ◽

Turbulent Spray Combustion ◽

Temperature Combustion ◽

Time Histories ◽

Turbulent Spray ◽

Lift Off

Turbulent spray combustion of n-dodecane fuel was studied numerically in current paper. The ignition delay, lift-off length, combustion chamber pressure rise, fuel penetration and vapor mass fraction were compared with experimental data. n-Dodecane kinetic model was studied by using a recently developed mechanism. The combustion chamber pressure rise was modeled and compared with experiments; the result was corrected for speed-of-sound to find the ignition delay timing in comparison with pressure-based ignition delay measurement. Species time histories and reaction paths at low and high temperature combustion are modeled and studied at two conditions, 900 K and 1200 K combustion chamber temperatures. The modeled species mass histories were discussed to define the first-stage and total ignition delay timings. Among all of the studied species in this work, including OH, Hydroperoxyalkyl mass history can be utilized to determine the exact timing of luminosity-based ignition delay. Moreover, n-dodecane vapor penetration can be used to determine the luminosity-based ignition delay.

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Investigations of Evaporative Cooling and Turbulence Flame Interaction Modeling in Ethanol Turbulent Spray Combustion Using Tabulated Chemistry

Fluids ◽

10.3390/fluids4040187 ◽

2019 ◽

Vol 4 (4) ◽

pp. 187 ◽

Cited By ~ 4

Author(s):

Fernando Luiz Sacomano Filho ◽

Louis Dressler ◽

Arash Hosseinzadeh ◽

Amsini Sadiki ◽

Guenther Carlos Krieger Filho

Keyword(s):

Evaporative Cooling ◽

Spray Combustion ◽

Flame Surface ◽

Flamelet Generated Manifold ◽

Tabulated Chemistry ◽

Turbulent Spray Combustion ◽

Interaction Modeling ◽

Cooling Effects ◽

Turbulent Spray ◽

Modeling Strategy

Evaporative cooling effects and turbulence flame interaction are analyzed in the large eddy simulation (LES) context for an ethanol turbulent spray flame. Investigations are conducted with the artificially thickened flame (ATF) approach coupled with an extension of the mixture adaptive thickening procedure to account for variations of enthalpy. Droplets are tracked in a Euler–Lagrangian framework, in which an evaporation model accounting for the inter-phase non-equilibrium is applied. The chemistry is tabulated following the flamelet generated manifold (FGM) method. Enthalpy variations are incorporated in the resulting FGM database in a universal fashion, which is not limited to the heat losses caused by evaporative cooling effects. The relevance of the evaporative cooling is evaluated with a typically applied setting for a flame surface wrinkling model. Using one of the resulting cases from the evaporative cooling analysis as a reference, the importance of the flame wrinkling modeling is studied. Besides its novelty, the completeness of the proposed modeling strategy allows a significant contribution to the understanding of the most relevant phenomena for the turbulent spray combustion modeling.

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Simulating Flame Lift-Off Characteristics of Diesel and Biodiesel Fuels Using Detailed Chemical-Kinetic Mechanisms and Large Eddy Simulation Turbulence Model

Journal of Energy Resources Technology ◽

10.1115/1.4007216 ◽

2012 ◽

Vol 134 (3) ◽

Cited By ~ 28

Author(s):

Sibendu Som ◽

Douglas E. Longman ◽

Zhaoyu Luo ◽

Max Plomer ◽

Tianfeng Lu ◽

...

Keyword(s):

Large Eddy Simulation ◽

Turbulence Model ◽

Turbulence Models ◽

Chemical Kinetic ◽

Spray Combustion ◽

Eddy Simulation ◽

Large Eddy ◽

Kinetic Mechanisms ◽

Lift Off ◽

Biodiesel Fuels

Combustion in direct-injection diesel engines occurs in a lifted, turbulent diffusion flame mode. Numerous studies indicate that the combustion and emissions in such engines are strongly influenced by the lifted flame characteristics, which are in turn determined by fuel and air mixing in the upstream region of the lifted flame, and consequently by the liquid breakup and spray development processes. From a numerical standpoint, these spray combustion processes depend heavily on the choice of underlying spray, combustion, and turbulence models. The present numerical study investigates the influence of different chemical kinetic mechanisms for diesel and biodiesel fuels, as well as Reynolds-averaged Navier–Stokes (RANS) and large eddy simulation (LES) turbulence models on predicting flame lift-off lengths (LOLs) and ignition delays. Specifically, two chemical kinetic mechanisms for n-heptane (NHPT) and three for biodiesel surrogates are investigated. In addition, the renormalization group (RNG) k-ε (RANS) model is compared to the Smagorinsky based LES turbulence model. Using adaptive grid resolution, minimum grid sizes of 250 μm and 125 μm were obtained for the RANS and LES cases, respectively. Validations of these models were performed against experimental data from Sandia National Laboratories in a constant volume combustion chamber. Ignition delay and flame lift-off validations were performed at different ambient temperature conditions. The LES model predicts lower ignition delays and qualitatively better flame structures compared to the RNG k-ε model. The use of realistic chemistry and a ternary surrogate mixture, which consists of methyl decanoate, methyl nine-decenoate, and NHPT, results in better predicted LOLs and ignition delays. For diesel fuel though, only marginal improvements are observed by using larger size mechanisms. However, these improved predictions come at a significant increase in computational cost.

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