Large Eddy Simulation of a Two-Phase Staged Swirling Burner Using an Euler-Lagrange Approach: Validation of the Injection Strategy

2018 ◽  
Author(s):  
Léo Cunha Caldeira Mesquita ◽  
Aymeric Vié ◽  
Sébastien Ducruix
Keyword(s):  
Large Eddy Simulation ◽  
Size Distribution ◽  
Droplet Size ◽  
Liquid Velocity ◽  
Droplet Size Distribution ◽  
Injection System ◽  
Numerical Representation ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Input Parameters

A two-staged swirling burner is numerically simulated using Large Eddy Simulation (LES). This combustor uses two types of injection: a multipoint system that consists in 10 holes in a crossflow configuration, and a pilot system that uses a pressure-swirl atomizer. The relation between the rate of fuel injected from each injection system was found to be related with flame shape transition and hysteresis phenomena[4]. Also, the pilot spray was found to have a major role on these transitons, so it is of paramount importance to correctly reproduce its behavior on the numerical modeling, if one is interested in simulating these flame bifurcations. To describe the spray, a point-droplet approximation is used in a Lagrangian framework with the FIM-UR model [1], that has already proven its accuracy for several configurations. However, in this application it fails to reproduce the droplet size distribution, especially in the Central Recirculation Zone (CRZ), as it uses an arbitrary expression to impose the spray opening limits (which are not input parameters). In the present work, the input parameters of the FIM-UR model are modified to enable the recovery of the right droplet size distribution and improve the description of the liquid velocity field, resulting in a better numerical representation of the experimental results, essential for further studies.

scholarly journals A population balance model for large eddy simulation of polydisperse droplet evolution

2019 ◽  
Vol 878 ◽  
pp. 700-739 ◽  
Author(s):  
A. K. Aiyer ◽  
D. Yang ◽  
M. Chamecki ◽  
C. Meneveau
Keyword(s):  
Large Eddy Simulation ◽  
Size Distribution ◽  
Droplet Size ◽  
Droplet Breakup ◽  
Dispersed Phase ◽  
Size Distributions ◽  
Oil Droplets ◽  
One Dimensional ◽  
Eddy Simulation ◽  
Large Eddy

In the context of many applications of turbulent multi-phase flows, knowledge of the dispersed phase size distribution and its evolution is critical to predicting important macroscopic features. We develop a large eddy simulation (LES) model that can predict the turbulent transport and evolution of size distributions, for a specific subset of applications in which the dispersed phase can be assumed to consist of spherical droplets, and occurring at low volume fraction. We use a population dynamics model for polydisperse droplet distributions specifically adapted to a LES framework including a model for droplet breakup due to turbulence, neglecting coalescence consistent with the assumed small dispersed phase volume fractions. We model the number density fields using an Eulerian approach for each bin of the discretized droplet size distribution. Following earlier methods used in the Reynolds-averaged Navier–Stokes framework, the droplet breakup due to turbulent fluctuations is modelled by treating droplet–eddy collisions as in kinetic theory of gases. Existing models assume the scale of droplet–eddy collision to be in the inertial range of turbulence. In order to also model smaller droplets comparable to or smaller than the Kolmogorov scale we extend the breakup kernels using a structure function model that smoothly transitions from the inertial to the viscous range. The model includes a dimensionless coefficient that is fitted by comparing predictions in a one-dimensional version of the model with a laboratory experiment of oil droplet breakup below breaking waves. After initial comparisons of the one-dimensional model to measurements of oil droplets in an axisymmetric jet, it is then applied in a three-dimensional LES of a jet in cross-flow with large oil droplets of a single size being released at the source of the jet. We model the concentration fields using $N_{d}=15$ bins of discrete droplet sizes and solve scalar transport equations for each bin. The resulting droplet size distributions are compared with published experimental data, and good agreement for the relative size distribution is obtained. The LES results also enable us to quantify size distribution variability. We find that the probability distribution functions of key quantities such as the total surface area and the Sauter mean diameter of oil droplets are highly variable, some displaying strong non-Gaussian intermittent behaviour.

scholarly journals Demistify: a large-eddy simulation (LES) and single-column model (SCM) intercomparison of radiation fog

2022 ◽  
Vol 22 (1) ◽  
pp. 319-333
Author(s):  
Ian Boutle ◽  
Wayne Angevine ◽  
Jian-Wen Bao ◽  
Thierry Bergot ◽  
Ritthik Bhattacharya ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Weather Prediction ◽  
Cloud Droplet ◽  
Droplet Size Distribution ◽  
Radiation Fog ◽  
Eddy Simulation ◽  
Cloud Droplet Size Distribution ◽  
Large Eddy ◽  
Single Column ◽  
Les Model

Abstract. An intercomparison between 10 single-column (SCM) and 5 large-eddy simulation (LES) models is presented for a radiation fog case study inspired by the Local and Non-local Fog Experiment (LANFEX) field campaign. Seven of the SCMs represent single-column equivalents of operational numerical weather prediction (NWP) models, whilst three are research-grade SCMs designed for fog simulation, and the LESs are designed to reproduce in the best manner currently possible the underlying physical processes governing fog formation. The LES model results are of variable quality and do not provide a consistent baseline against which to compare the NWP models, particularly under high aerosol or cloud droplet number concentration (CDNC) conditions. The main SCM bias appears to be toward the overdevelopment of fog, i.e. fog which is too thick, although the inter-model variability is large. In reality there is a subtle balance between water lost to the surface and water condensed into fog, and the ability of a model to accurately simulate this process strongly determines the quality of its forecast. Some NWP SCMs do not represent fundamental components of this process (e.g. cloud droplet sedimentation) and therefore are naturally hampered in their ability to deliver accurate simulations. Finally, we show that modelled fog development is as sensitive to the shape of the cloud droplet size distribution, a rarely studied or modified part of the microphysical parameterisation, as it is to the underlying aerosol or CDNC.

Large-Eddy Simulation of Atomizing Spray With Stochastic Modeling of Secondary Breakup

2003 ◽  
Author(s):  
Sourabh V. Apte ◽  
Mikhael Gorokhovski ◽  
Parviz Moin
Keyword(s):  
Large Eddy Simulation ◽  
Droplet Size ◽  
Particle Tracking ◽  
Hybrid Approach ◽  
Computational Cost ◽  
Fuel Injector ◽  
Combustion Dynamics ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Secondary Breakup

Large-eddy simulation (LES) of reacting multi-phase flows in practical combustor geometries is essential to accurately predict complex physical phenomena of turbulent mixing and combustion dynamics. This necessitates use of Lagrangian particle-tracking methodology for liquid phase in order to correctly capture the droplet evaporation rates in the sparse-liquid regime away from the fuel injector. Our goal in the present work is to develop a spray-atomization methodology which can be used in conjuction with the standard particle-tracking schemes and predict the droplet-size distribution accurately. The intricate process of primary atomization and lack of detailed experimental observations close to the injector requires us to model its global effects and focus on secondary breakup to capture the evolution of droplet sizes. Accordingly, a stochastic model for LES of atomizing spray is developed. Following Kolmogorov’s idea of viewing solid particle-breakup as a discrete random process, atomization of liquid blobs at high relative liquid-to-gas velocity is considered in the framework of uncorrelated breakup events, independent of the initial droplet size. Kolmogorov’s discrete model of breakup is represented by Fokker-Planck equation for the temporal and spatial evolution of droplet radius distribution. The parameters of the model are obtained dynamically by relating them to the local Weber number. A novel hybrid-approach involving tracking of individual droplets and a group of like-droplets known as parcels is developed to reduce the computational cost and maintain the essential features and dynamics of spray evolution. The present approach is shown to capture the complex fragmentary process of liquid atomization in idealized and realistic Diesel and gas-turbine combustors.

Effect of Droplet Size and Atomization on Spray Formation: A Priori Study Using Large-Eddy Simulation

2010 ◽  
Vol 86 (3-4) ◽  
pp. 533-561 ◽  
Author(s):  
Ville Anton Vuorinen ◽  
Harri Hillamo ◽  
Ossi Kaario ◽  
Mika Nuutinen ◽  
Martti Larmi ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Droplet Size ◽  
A Priori ◽  
Spray Formation ◽  
Eddy Simulation ◽  
Large Eddy

scholarly journals Large Eddy Simulation of an Ethanol Spray Flame with Secondary Droplet Breakup

2021 ◽  
Author(s):  
S. Gallot-Lavallée ◽  
W. P. Jones ◽  
A. J. Marquis
Keyword(s):  
Liquid Phase ◽  
Large Eddy Simulation ◽  
Droplet Size ◽  
Size Class ◽  
Droplet Breakup ◽  
Fuel Injector ◽  
Low Oxygen ◽  
Stochastic Field ◽  
Eddy Simulation ◽  
Large Eddy

AbstractA computational investigation of three configurations of the Delft Spray in Hot-diluted Co-flow (DSHC) is presented. The selected burner comprises a hollow cone pressure swirl atomiser, injecting an ethanol spray, located in the centre of a hot co-flow generator, with the conditions studied corresponding to Moderate or Intense Low-oxygen Dilution (MILD) combustion. The simulations are performed in the context of Large Eddy Simulation (LES) in combination with a transport equation for the joint probability density function (pdf) of the scalars, solved using the Eulerian stochastic field method. The liquid phase is simulated by the use of a Lagrangian point particle approach, where the sub-grid-scale interactions are modelled with a stochastic approach. Droplet breakup is represented by a simple primary breakup model in combination with a stochastic secondary breakup formulation. The approach requires only a minimal knowledge of the fuel injector and avoids the need to specify droplet size and velocity distributions at the injection point. The method produces satisfactory agreement with the experimental data and the velocity fields of the gas and liquid phase both averaged and ‘size-class by size-class’ are well depicted. Two widely accepted evaporation models, utilising a phase equilibrium assumption, are used to investigate the influence of evaporation on the evolution of the liquid phase and the effects on the flame. An analysis on the dynamics of stabilisation sheds light on the importance of droplet size in the three spray flames; different size droplets play different roles in the stabilisation of the flames.

High Momentum Jet Flames at Elevated Pressure, E: Quantification of Droplet Size Distribution and Transport

2020 ◽  
Author(s):  
Fabian Hampp ◽  
James Dakshina Gounder ◽  
Holger Ax ◽  
Rainer Lükerath ◽  
Oliver Lammel ◽  
...  
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Numerical Models ◽  
Flame Temperature ◽  
Droplet Size Distribution ◽  
Elevated Pressure ◽  
Injection System ◽  
High Momentum ◽  
Water Addition ◽  
Droplet Transport

Abstract The present work investigates a model combustor that approximates a full-scale segment of a high momentum jet stabilised combustion concept with the objective to broaden fuel flexibility limits. The rig features optical access for detailed laser based diagnostics. The current experiments are conducted at a pressure of 8 bar, constant jet velocity and adiabatic flame temperature. Three different injection systems are used to inject oil and oil / water blends. Droplet size distributions and turbulent droplet transport are quantified by means of phase Doppler interferometry. The injection system has a noticeable impact on the droplet size distribution. Water addition affects the fuel placement in radial direction significantly with distinct droplet transport into the reaction zone. The jet core and droplet transport is maintained as far as 7 x/d axial downstream from the nozzle exit. The shear layer shows a turbulent intensity of 12% of the main jet bulk velocity that drives the radial droplet transport into the recirculation zone. Mass flow and number density estimations illustrate the spatial distribution of the liquid loading in the combustion chamber. The present findings are complementary to the work in part A–D, support the development of fuel and load flexible high momentum jets based combustion concepts and the development and validation of numerical models.

Numerical Study on the Adaptation of Diesel Wave Breakup Model for Large-Eddy Simulation of Non-Reactive Gasoline Spray

2021 ◽  
Author(s):  
Ratnak Sok ◽  
Beini Zhou ◽  
Jin Kusaka
Keyword(s):  
Large Eddy Simulation ◽  
Droplet Size ◽  
Fuel Injection ◽  
Numerical Study ◽  
Direct Injection ◽  
Mie Scattering ◽  
Gasoline Direct Injection ◽  
Spray Penetration ◽  
Eddy Simulation ◽  
Large Eddy

Abstract Gasoline direct injection (GDI) is a promising solution to increase engine thermal efficiency and reduce exhaust gas emissions. The GDI operation requires an understanding of fuel penetration and droplet size, which can be investigated numerically. In the numerical simulation, primary and secondary breakup phenomena are studied by the Kelvin-Helmholtz/Rayleigh-Taylor (KH-RT) wave breakup models. The models were initially developed for diesel fuel injection, and in the present work, the models are extended to the GDI application combined using large-eddy simulation (LES). The simulation is conducted using the KIVA4 code. Measured data of experimental spray penetration and Mie-scattering image comparisons are carried out under non-reactive conditions at an ambient temperature of 613K and a density of 4.84 kg/m3. The spray penetration and structures using LES are compared with traditional Reynolds-Averaged Navier-Stokes (RANS). Grid size effects in the simulation using LES and RANS models are also investigated to find a reasonable cell size for future reactive gasoline spray/combustion studies. The fuel spray penetration and droplet size are dependent on specific parameters. Parametric studies on the effects of adjustable constants of the KH-RT models, such as time constants, size constants, and breakup length constant, are discussed. Liquid penetrations from the RANS turbulence model are similar to that of the LES turbulence model’s prediction. However, the RANS model is not able to capture the spray structure well.

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