Large-eddy simulations of turbulent flows in internal combustion engines

Banaeizadeh, Araz; Afshari, Asghar; Schock, Harold; Jaberi, Farhad

doi:10.1016/j.ijheatmasstransfer.2012.12.065

Cited by 63 publications

(30 citation statements)

References 73 publications

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“…Previous CFD simulations for RCMs have been based on a laminar model, 2,6,7,9,10 RANS turbulence models, 6,11 and large eddy simulation (LES). 12 …”

Section: Methodsmentioning

confidence: 99%

Simplified Approach to the Prediction and Analysis of Temperature Inhomogeneity in Rapid Compression Machines

et al. 2015

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1Substantial progress has been made in understanding and reducing temperature inhomogeneity in rapid compression machines (RCMs) with the help of computational modelling. To date, however, it has not been possible to investigate and map the full range of possible RCM designs, working gases and operating conditions. In this article, we present a framework which simplifies the task of comprehensive and general RCM performance prediction. A set of thermophysical and geometrical parameters have been defined to characterize the design and operating conditions of a general RCM. Dimensional analysis was applied to reduce the number of variables and a sensitivity analysis, based on computational simulations, was used to rank the dimensionless parameters and eliminate unimportant ones. The results of this analysis show that Reynolds number, Prandtl number, aspect ratio, and crevice volume ratio are the most important parameters determining temperature inhomogeneity.A further set of computational simulations was conducted to predict post-compression temperature inhomogeneity over the full range of RCM design and operating parameters. These results are well represented by a simple power law equation that correlates a dimensionless temperature inhomogeneity parameter (mass-averaged over the main chamber) as a function of post-compression time with just three parameters -Peclet number (the product of Reynolds and Prandtl numbers), aspect ratio, and crevice volume ratio. This equation can serve as a simple and general tool for RCM designers and users who wish to determine optimal configurations that minimise temperature inhomogeneity for combustion experiments.2

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“…Previous CFD simulations for RCMs have been based on a laminar model, 2,6,7,9,10 RANS turbulence models, 6,11 and large eddy simulation (LES). 12 …”

Section: Methodsmentioning

confidence: 99%

Simplified Approach to the Prediction and Analysis of Temperature Inhomogeneity in Rapid Compression Machines

et al. 2015

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“…Accordingly, the majority of SI engine simulations employ LES combustion models that have already been established in this regard within other applications. Specifically, numerous works use the Flame Surface Density (FSD) approach [30,31], the G-equation [32], the Artificially Thickened Flame (ATF) model [33] and also a few applications based on Probability Density Functions (PDF) [34,35] exist.…”

Section: Chaomentioning

confidence: 99%

Evaluation of the flame propagation within an SI engine using flame imaging and LES

Kuenne

Yildar

et al. 2017

Combustion Theory and Modelling

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This work shows experiments and simulations of the fired operation of a spark ignition engine with port-fueled injection. The test-rig considered is an optically accessible single cylinder engine specifically designed at TU Darmstadt for the detailed investigation of in-cylinder processes and model validation. The engine was operated under lean conditions using isooctane as a substitute for gasoline. Experiments have been conducted to provide a sound database of the combustion process. A planar flame imaging technique has been applied within the swirl and tumble plane to provide statistical information on the combustion process to complement the pressure-based comparison between simulation and experiments. This data is then analyzed and used to assess the Large Eddy Simulation performed within this work. For the simulation, the engine code KIVA has been extended by the dynamically thickened flame model combined with chemistry reduction by means of pressure dependent tabulation. 60 cycles have been simulated to perform a statistical evaluation. Based on a detailed comparison with the experimental data, a systematic study has been conducted to obtain insight into the most crucial modeling uncertainties.

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“…Only a very limited number of studies have been performed in engines with DNS [18]. Reynolds Averaged Navier Stokes (RANS) [17] and more recently Large Eddy Simulation (LES) based approaches are typically employed for engine simulations [7,3,22,12]. RANS, which is the industrial standard approach is based on ensemble averaged governing equations.…”

Section: Introductionmentioning

confidence: 99%

A study of the controlling parameters of fuel air mixture formation for ECN Spray A

Vogiatzaki

Crua

Morgan

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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Designing future ultra-high efficiency, ultra-low emission engines requires an in depth understanding of the multiscale, multi-phase phenomena taking place in the combustion chamber. The performance of the fuel delivery system is key in the air fuel mixture formation and hence the combustion characteristics, however in most spray modelling approaches is not considered directly. Thus, it is important to understand how the selection of models that mimic injection process affect predictions. In this paper we present an Eulerian-Lagrangian framework based on OpenFOAM libraries to model spray injection dynamics. The framework accounts for primary droplet formation (based on a parcel method with predefined initial droplet size distribution), secondary droplet breakup, evaporation and heat transfer. In order to account for the interaction of droplets with turbulence, simulations were performed within the LES context with two different turbulence models. A systematic variation of the key injection parameters (parcel number, parcel size distribution) of the parcel method as well as the grid size was considered. Varying the parcel number affects the initial droplet size distribution which in turn, depending on the selection of the turbulence and the evaporation sub-models, affects: spray dispersion; spray penetration; and subsequent droplet size distribution. Results were validated against the baseline experimental data for evaporating ECN Spray A with n-dodecane chosen as a surrogate for Diesel fuel. Keywords ECN Spray A, Eulerian-Lagrangian, LES, OpenFOAM IntroductionIn both Diesel and spark ignition engines fuel is injected into the combustion chamber at elevated pressures. Nowadays realistic injection pressures for common-rail Diesel reach up to 3500 bars. The reason behind the need for such extreme pressures is to promote primary and secondary atomisation until a combustible mixture is formed. The higher the injection pressure the higher the shear between the static air within the combustion cylinder and the liquid. At extreme ambient pressures and temperatures the fuel can even exhibit supercritical behaviour that causes a reduction in its surface tension. Combustion 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 [1,19,14,5,6]. These processes clearly play a critical role in determining the engine combustion and emission characteristics.

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Large-eddy simulations of turbulent flows in internal combustion engines

Cited by 63 publications

References 73 publications

Simplified Approach to the Prediction and Analysis of Temperature Inhomogeneity in Rapid Compression Machines

Simplified Approach to the Prediction and Analysis of Temperature Inhomogeneity in Rapid Compression Machines

Evaluation of the flame propagation within an SI engine using flame imaging and LES

A study of the controlling parameters of fuel air mixture formation for ECN Spray A

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