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

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

ASME 2011 Internal Combustion Engine Division Fall Technical Conference ◽

10.1115/icef2011-60051 ◽

2011 ◽

Cited By ~ 8

Author(s):

Sibendu Som ◽

Douglas E. Longman ◽

Zhaoyu Luo ◽

Max Plomer ◽

Tianfeng Lu ◽

...

Keyword(s):

Turbulence Model ◽

Turbulence Models ◽

Chemical Kinetic ◽

Upstream Region ◽

Spray Combustion ◽

Turbulent Diffusion Flame ◽

Lifted Flame ◽

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 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 9-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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Large Eddy Simulation of High Reynolds Number Nonreacting and Reacting JP-8 Sprays in a Constant Pressure Flow Vessel With a Detailed Chemistry Approach

Journal of Energy Resources Technology ◽

10.1115/1.4032901 ◽

2016 ◽

Vol 138 (3) ◽

Cited By ~ 9

Author(s):

Luis Bravo ◽

Sameera Wijeyakulasuriya ◽

Eric Pomraning ◽

Peter K. Senecal ◽

Chol-Bum Kweon

Keyword(s):

Large Eddy Simulation ◽

Internal Combustion Engines ◽

Constant Pressure ◽

Engine Performance ◽

Spray Combustion ◽

Pressure Flow ◽

Detailed Chemistry ◽

Eddy Simulation ◽

Large Eddy ◽

Lift Off

In military propulsion applications, the characterization of internal combustion engines operating with jet fuel is vital to understand engine performance, combustion phasing, and emissions when JP-8 is fully substituted for diesel fuel. In this work, high-resolution large eddy simulation (LES) simulations have been performed in-order to provide a comprehensive analysis of the detailed mixture formation process in engine sprays for nozzle configurations of interest to the Army. The first phase examines the behavior of a nonreacting evaporating spray, and demonstrates the accuracy in predicting liquid and vapor transient penetration profiles using a multirealization statistical grid-converged approach. The study was conducted using a suite of single-orifice injectors ranging from 40 to 147 μm at a rail pressure of 1000 bar and chamber conditions at 900 K and 60 bar. The next phase models the nonpremixed combustion behavior of reacting sprays and investigates the submodel ability to predict auto-ignition and lift-off length (LOL) dynamics. The model is constructed using a Kelvin Helmholtz–Rayleigh Taylor (KH–RT) spray atomization framework coupled to an LES approach. The liquid physical properties are defined using a JP-8 mixture containing 80% n-decane and 20% trimethylbenzene (TMB), while the gas phase utilizes the Aachen kinetic mechanism (Hummer, et al., 2007, “Experimental and Kinetic Modeling Study of Combustion of JP-8, Its Surrogates, and Reference Components in Laminar Non Premixed Flows,” Proc. Combust. Inst., 31, pp. 393–400 and Honnet, et al., 2009, “A Surrogate Fuel for Kerosene,” Proc. Combust. Inst., 32, pp. 485–492) and a detailed chemistry combustion approach. The results are in good agreement with the spray combustion measurements from the Army Research Laboratory (ARL), constant pressure flow (CPF) facility, and provide a robust computational framework for further JP-8 studies of spray combustion.

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The effects of chemical kinetic mechanisms on large eddy simulation (LES) of a nonpremixed hydrogen jet flame

International Journal of Hydrogen Energy ◽

10.1016/j.ijhydene.2016.04.079 ◽

2016 ◽

Vol 41 (26) ◽

pp. 11427-11440 ◽

Cited By ~ 7

Author(s):

Xuejin Zhou ◽

Xi Jiang ◽

Daniel Mira Martinez

Keyword(s):

Large Eddy Simulation ◽

Chemical Kinetic ◽

Jet Flame ◽

Eddy Simulation ◽

Large Eddy ◽

Kinetic Mechanisms

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Large Eddy Simulation of Film Cooling Involving Compound Angle Holes: Comparative Study of LES and RANS

Processes ◽

10.3390/pr9020198 ◽

2021 ◽

Vol 9 (2) ◽

pp. 198

Author(s):

Seung Il Baek ◽

Joon Ahn

Keyword(s):

Large Eddy Simulation ◽

Film Cooling ◽

Orientation Angle ◽

Turbulence Models ◽

Film Cooling Effectiveness ◽

Injection Angle ◽

Blowing Ratio ◽

Eddy Simulation ◽

Large Eddy ◽

Compound Angle

A large eddy simulation (LES) was performed for film cooling in the gas turbine blade involving spanwise injection angles (orientation angles). For a streamwise coolant injection angle (inclination angle) of 35°, the effects of the orientation angle were compared considering a simple angle of 0° and 30°. Two ratios of the coolant to main flow mass flux (blowing ratio) of 0.5 and 1.0 were considered and the experimental conditions of Jung and Lee (2000) were adopted for the geometry and flow conditions. Moreover, a Reynolds averaged Navier–Stokes simulation (RANS) was performed to understand the characteristics of the turbulence models compared to those in the LES and experiments. In the RANS, three turbulence models were compared, namely, the realizable k-ε, k-ω shear stress transport, and Reynolds stress models. The temperature field and flow fields predicted through the RANS were similar to those obtained through the experiment and LES. Nevertheless, at a simple angle, the point at which the counter-rotating vortex pair (CRVP) collided on the wall and rose was different from that in the experiment and LES. Under the compound angle, the point at which the CRVP changed to a single vortex was different from that in the LES. The adiabatic film cooling effectiveness could not be accurately determined through the RANS but was well reflected by the LES, even under the compound angle. The reattachment of the injectant at a blowing ratio of 1.0 was better predicted by the RANS at the compound angle than at the simple angle. The temperature fluctuation was predicted to decrease slightly when the injectant was supplied at a compound angle.

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Large eddy simulation of n-heptane/syngas pilot ignition spray combustion: ignition process, liftoff evolution and pollutant emissions

Energy ◽

10.1016/j.energy.2021.121080 ◽

2021 ◽

pp. 121080

Author(s):

Shenghui Zhong ◽

Shijie Xu ◽

Xue-Song Bai ◽

Zhijun Peng ◽

Fan Zhang

Keyword(s):

Large Eddy Simulation ◽

Pollutant Emissions ◽

Spray Combustion ◽

Ignition Process ◽

Eddy Simulation ◽

Large Eddy

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Simulation of Vortex Instability in a Pipe Trifurcation

Volume 1: Fora, Parts A, B, C, and D ◽

10.1115/fedsm2003-45438 ◽

2003 ◽

Cited By ~ 1

Author(s):

Albert Ruprecht ◽

Ralf Neubauer ◽

Thomas Helmrich

Keyword(s):

Large Eddy Simulation ◽

Turbulence Model ◽

Model Test ◽

Reasonable Agreement ◽

Navier Stokes ◽

Extended Version ◽

Vortex Instability ◽

Flow Phenomenon ◽

Eddy Simulation ◽

Large Eddy

The vortex instability in a spherical pipe trifurcation is investigated by applying a Very Large Eddy Simulation (VLES). For this approach an new adaptive turbulence model based on an extended version of the k-ε model is used. Applying a classical Reynolds-averaged Navier-Stokes-Simulation with the standard k-ε model is not able to forecast the vortex instability. However the prescribed VLES method is capable to predict this flow phenomenon. The obtained results show a reasonable agreement with measurements in a model test.

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Improving a Two-Equation Turbulence Model for Canopy Flows Using Large-Eddy Simulation

Boundary-Layer Meteorology ◽

10.1007/s10546-013-9850-x ◽

2013 ◽

Vol 149 (2) ◽

pp. 231-257 ◽

Cited By ~ 16

Author(s):

A.Silva Lopes ◽

J. M. L. M. Palma ◽

J. Viana Lopes

Keyword(s):

Large Eddy Simulation ◽

Turbulence Model ◽

Eddy Simulation ◽

Large Eddy ◽

Canopy Flows

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Evaluation of Turbulence Models Using Direct Numerical and Large-Eddy Simulation Data

Journal of Fluids Engineering ◽

10.1115/1.4003425 ◽

2011 ◽

Vol 133 (2) ◽

Cited By ~ 24

Author(s):

Hassan Raiesi ◽

Ugo Piomelli ◽

Andrew Pollard

Keyword(s):

Boundary Layer ◽

Large Eddy Simulation ◽

Eddy Viscosity ◽

Predictive Accuracy ◽

Turbulence Models ◽

Special Treatment ◽

Two Dimensional ◽

Square Duct ◽

Eddy Simulation ◽

Large Eddy

The performance of some commonly used eddy-viscosity turbulence models has been evaluated using direct numerical simulation (DNS) and large-eddy simulation (LES) data. Two configurations have been tested, a two-dimensional boundary layer undergoing pressure-driven separation, and a square duct. The DNS and LES were used to assess the k−ε, ζ−f, k−ω, and Spalart–Allmaras models. For the two-dimensional separated boundary layer, anisotropic effects are not significant and the eddy-viscosity assumption works well. However, the near-wall treatment used in k−ε models was found to have a critical effect on the predictive accuracy of the model (and, in particular, of separation and reattachment points). None of the wall treatments tested resulted in accurate prediction of the flow field. Better results were obtained with models that do not require special treatment in the inner layer (ζ−f, k−ω, and Spalart–Allmaras models). For the square duct calculation, only a nonlinear constitutive relation was found to be able to capture the secondary flow, giving results in agreement with the data. Linear models had significant error.

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Investigation of the velocity field downstream of a benchmark vent using numerical simulation and hot-wire anemometry

EPJ Web of Conferences ◽

10.1051/epjconf/201921302076 ◽

2019 ◽

Vol 213 ◽

pp. 02076

Author(s):

Jan Sip ◽

Frantisek Lizal ◽

Jakub Elcner ◽

Jan Pokorny ◽

Miroslav Jicha

Keyword(s):

Fluid Dynamics ◽

Numerical Simulation ◽

Velocity Field ◽

Flow Field ◽

Large Eddy Simulation ◽

Turbulence Models ◽

Hot Wire ◽

Eddy Simulation ◽

Large Eddy ◽

Precise Prediction

The velocity field in the area behind the automotive vent was measured by hot-wire anenemometry in detail and intensity of turbulence was calculated. Numerical simulation of the same flow field was performed using Computational fluid dynamics in commecial software STAR-CCM+. Several turbulence models were tested and compared with Large Eddy Simulation. The influence of turbulence model on the results of air flow from the vent was investigated. The comparison of simulations and experimental results showed that most precise prediction of flow field was provided by Spalart-Allmaras model. Large eddy simulation did not provide results in quality that would compensate for the increased computing cost.

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