Atomization Of A Turbulent Layer Of A Mixture

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Unsteady Transport at a Liquid-Gas Interface at Supercritical

Except for final stages in the cascade, the atomization process is weakly dependent on surface tension. Consequently, substantial similarities are found for homogeneous jets (e.g., air-into-air or water -into-water) and liquid jets into gas. Vorticity dynamics explains the cascade which is essentially a turbulent transition process with hairpin

MODELLING OF COMBUSTION PROCESSES OF LIQUID FUELS Antoni

The thickness of boundary layer V is defined with reference to the laminar flow as result of solution of equations of the boundary layer and is described by dependence (8): d dcr. 0.5 0.33 l 5Red Pr d, for Re Re V (8) The thickness of boundary layer V with reference to the flow turbulent is defined on the basis

Simulation of primary atomization with an octree adaptive

Key words: atomization, numerical simulation, Gerris, VOF, two-phase mixing layer, Kelvin-Helmholtz PACS: 47.11.+j 1. Introduction The breakup of liquid masses by high-speed air streams is an amazingly com-plex phenomenon that occurs in many natural and man-made circumstances. For instance, spume formation at the top of sea-wave crests

Paper ID ICLASS06-084 MODELING EFFECT OF SPRAY EVAPORATION ON

droplet-laden turbulent shear layer with one-step chemistry has been conducted. The overall flame structure has been studied, and particular attention is given to the conditional scalar dissipation rate, defined as <χ Z>=2D Z< ∇Z 2>, where Z is the mixture fraction and D Z is the mixture fraction diffusion coefficient. This quantity appears

A two-phase mixing layer between parallel gas and liquid

are immiscible, so the mixing layer here indeed refers to a layer consisting of a mixture of gas and a dispersion of droplets generated from the bulk liquid disintegration. The process where the bulk liquid stream breaks into a large number of small droplets is often referred to as atomization and the resulting gas-droplets mixture as a spray.

Liquid Fuel Evaporation under Supercritical Conditions

Recent experimental works [18, 40] showed that the transition from traditional spray atomization to a continuous turbulent mixing layer can also take place in diesel engine relevant conditions.By creating a liquid n-dodecane thin film surrounded by nitrogen environment, the dynamic evaporation process of n -dodecane is studied

Turbulent Flow And Combustion Ntnu

theoryof turbulence, turbulent premixed and non-premixed flames, andmultiphase flows Covers spray atomization and combustion, solid-propellantcombustion, homogeneous propellants, nitramines, reactingboundary-layer flows, single energetic particle combustion, andgranular bed combustion Provides experimental setups and results

Large Eddy Simulation (LES) Applied to Advanced Engine

diffusion dominated turbulent mixing prior to atomization Interfacial region between jets interact in presence of exceedingly large gradients W. Mayer, et al. (1998). Atomization and breakup of cryogenic propellants under high- pressure subcritical and supercritical conditions. Journal of Propulsion and Power, 14 (5): 835-842.

Development of Discrete Population Balance Mixture

for mixture stress will be employed where is an effec-tive dynamic viscosity containing a turbulent contribu-tion, is the pressure, ̿ is the unit tensor, and a super-posed denoted the transpose of a second order tensor. Substituting (8) into (2) produces ⃗ ⃗ ⃗ ⃗ ⃗⃗ ⃗⃗ (9)

Clustering and entrainment effects on the evaporation of

The prototypal flow for an evaporating spray is constituted by a turbulent free jet which is characterized by the effect of environmental gas entrainment. In more detail, a turbulent jet is constituted by a rotational turbulent core which is continuously entrained by the surrounding irrotational fluid [28].

Numerical investigation of the autoignition of turbulent

Z mixture fraction Greek symbols x scalar dissipation rate 1 dissipation rate of turbulent kinetic energy m eff effective viscosity v k chemical production rate of species k r density s f turbulent Schmidt number for variable f Subscripts llth fictitious particle st stoichiometry Superscripts f~ Favre-averaged (density-weighted) mean f~002

Center for Turbulence Research Annual Research Briefs 2013

mixture, with the combustion stand-off distance being controlled by the interaction of turbulent transport, droplet heating and vaporization, and gas-phase chemical reactions. In this study, conditions are identified under which analyses of laminar flamelets can shed light on aspects of turbulent spray ignition.

STRUCTURE AND BREAKUP PROPERTIES OF SPRAYS

layer in the region where the liquid core is present, followed by a multiphase jet that evolves into a dilute round spray flow. The multiphase mixing layer begins close to the jet exit within the atomization breakup regime. Primary breakup occurs due to the formation of ligaments and other

Large Eddy Simulation of Multi-Component Mixing Layers at

a fully turbulent shear layer by artificial embossed periodic momentum. The present study will focus on the interface area of jets by abstracting them into a shear layer computation, based on the DNS results by Okong o et al [6]. Large Eddy Simulation (LES) technique, known for its computational affordability in comparison to DNS is used

Detonation Initiation in Dispersed Fuel-Air Mixtures

transport of kinetic energy of turbulent pulsations at the same time obeys the deterministic laws being the macroscopic characteristic. Averaging by Favre with the αρweight (α volumetric fraction of the gas phase, ρ gas density) we obtain the system for the gas phase in a multiphase flow [1] The term responsible for

Dispersed-Phase Structure of Pressure-Atomized Sprays at

atomization breakup conditions, considering large-scale (9.5 mm initial diameter) water jets in still-air at ambient pressures of 1, 2, and 4 atm, with both fully developed turbulent pipe flow and nonturbulent slug flow at the jet exit. Drop sizes and velocities and liquid-volume fractions and fluxes were measured using holography.

NASA CR-72532

and atomization but it is assumed that the rate of atomization is very small compared to the rate of vaporization in a turbulent boundary layer. Also, it is assumed that chemical reaction rates are very large compared to the rate of vaporization, These assumptions tacitly imply that the reaction zone ends as soon as the liquid layer is vaporized.

ILASS-Americas 29th Annual Conference on Liquid Atomization

ety of conditions have been studied: non-turbulent [11, 12], turbulent [14], pulsed [15], and injection direction [16], among others. The large number of parameters can result in a number of uncertainties when attempting to replicate a given experiment in a numerical simulation. Furthermore, signi cant dif-

Chapter 9 Atomic Absorption and Atomic Fluorescence Spectrometry

furnace atomization. -During atomization, part of the analyte and matrix apparently diffuse into the surface of the tube, which slows the atomization process, thus giving smaller analyte signals. -To overcome this effect, most graphite surfaces are coated with a thin layer of pyrolytic carbon, which seals the pores of the graphite tube.

NUMERICAL MODELLING OF TURBULENCE EFFECTS WITHIN EVAPORATING

mixture (KJ/kg K) Turbulence constant Binary DiffUsivity (m2/s) Loss coefficient due to nozzle inlet geometry (0.45) Proportionality constant (0.23) Turbulent kinetic energy of the liquid (m2/s2) Latent heat of the fuel at the surface temperature (KJ/kg) Droplet mass (kg) Gas phase Nusselt number Turbulent Prandtl number (0.9)

Turbulent liquid spray mixing and combustion fundamental

the mixture fraction is very close to the most reactive mixture fraction ()f MR = 0.12 and the scalar dissipation rate of mixture fraction ()χ is sufficiently low. Im et al. [4] investigated the ignition of a hydrogen-air in a turbulent mixing layer using a more detailed chemistry mechanism with nine species and 38 reversible reactions.

LES of Diesel Sprays Using Advanced Computational Methods and

Detailed Simulation of Nozzle Influence on Atomization Mixture Formation: Coherent Liquid Fully developed turbulent inflow Actual nozzle inflow Le Chenadec, V., Pitsch, H., A conservative framework for primary atomization computation and application to the study of nozzle and density ratio effects , Atomization and Spray, 23, 2013

The effect of a cross-flow on secondary atomization in

within the turbulent boundary layer limits. Also, fuel vaporization rate appears to be larger for the highest cross-flow velocity used in these experiments. The black area above the surface, at 7 and 12 ms ASOI, show that secondary atomization is enhanced as the cross-flow velocity increases. V c = V5 m/s = 1 m/s t = 3 ms t = 7 ms t = 12 ms

SOE MMMMChE1 - DTIC

The drbqco jag&ing shear layer adjacent to this core exhibits some properties of & loca.y-homogeneou',.,flow, however, large drops were also formed at the liquid surface which probably depart from this behavior.

Size and velocity distributions of droplets in an air-water

towards a better understanding of the atomization and redeposition processes at the interface. We have therefore investigated these characteristics for a horizontal air-water pipe flow. In this work, we will focus on the flow regime where atomization occurs but the flow still remains stratified. The liquid layer flows at the bottom of the

Generation of Multiphase Flows

usually divided into primary atomization and secondary atomization. 1.1. Creation of suspensions of solid particles in a gaseous phase Here we present two very different examples of the generation of flows with solid particles. The first case study is designed as a micro-gravity examination of the combustion of a suspension of wheat starch

Cryogenic, Multiphase, Hydrogen-Oxygen Detonations

hydrogen. There are phenomena that affect the initial state of the mixture which include atomization, turbulent dispersion, vaporization, turbulent mixing, wall-wetting, and heat-transfer. Other phenomena affect the propagation of the detonation through the mixture which include droplet shattering, vaporization, chemical induction time, wall

Investigation of Diesel Spray Primary Break-up and

mixture formation and the mixture formation will be possible with cylinder flow by utilizing fuel injection systems. Undrstanding spray chracteristics and its formation mechanism is very important for diesel engine design and computer modelling. For liquid spray breakup, the jet atomization region is the region of interest in direct diesel

Experimental Valuation Diagnostics of Hydrous Ethanol Sprays

fuel tube and the remaining produces shear layer as it leaves the injector orifi ce enhancing the atomization process. Th e back fl ow of air at the tip of the fuel tube results in a two-phase turbulent fl ow passing through a positive pressure fi eld. Th is mixture undergoes sudden decrease in pressure, while exiting through the injector orifi ce.

Reacting flow modeling and applications in STAR-CCM+

Tabulated Detailed Chemistry for turbulent combustion Precompute chemistry table and retrieve during CFD computation Can use large mechanism Dimension reduction to chemistry Consider turbulence-chemistry interactions. Existing models PPDF with equilibrium PPDF with laminar flamelets PVM (Progress variable model)

Evaluation of StereoPIV measurement of droplet velocity in an

to numerous experiments in aerodynamics (see e.g., [14]), turbulent boundary layer flows (e.g., [15]), and in combustion chambers [2 4, 16, 17]. The application of a PIV system to measure droplet velocity in sprays is, however, different from the typical applications of PIV. In the measurement of a spray velocity

Powder metallurgy basics & applications

1. A hard brittle layer of pure metal which is subsequently milled to obtain powder (eg. iron powder) 2. A soft, spongy substance which is loosely adherent and easily removed by scrubbing 3. A direct powder deposit from the electrolyte that collects at the bottom of the cell Factors promoting powder deposits are, high current density, low metal

Aerospace Sciences Exhibit

pressure-atomized sprays was studied for atomization breakup conditions, considering large-scale (9.5 mm initial diameter) water jets in still air at ambient pressures of I, 2 and 4 atm., with both fully-developed turbulent pipe flow and nonturbulent slug flow at the jet exit. Drop sizes and

Improvedatomization,collisionandsub-gridscale

atomization, which affects momentum transfer to the gas phase through 10 a specific spray cone angle and drop size distribution; turbulent air entrainment, produced by the injected fuel s momentum ex-change and by the local flow field; vaporization, which converts the liquid phase into a gaseous mixture.

Evaporation of nearly monosized droplets of hexane, heptane

turbulent flow vortices. For example, Hardalupas & Horender [8] characterized the cold spray in a swirl stabilized burner by Phase-Doppler technique and measured the concentration fluctuations of the droplets. Two mechanisms were identified as sources of concentration unsteadiness, the liquid break-up process during atomization, which is

Turbulent Flow And Combustion Ntnu

in combustion and multiphaseflows, including laminar premixed and non-premixed flames, theoryof turbulence, turbulent premixed and non-premixed flames, andmultiphase flows Covers spray atomization and combustion, solid-propellantcombustion, homogeneous propellants, nitramines, reactingboundary-layer flows, single energetic particle

International Journal of Heat and Fluid Flow

atomization process and the entrained droplets are formed by the turbulent interaction at the surface of the liquid/vapor interface. In this study, a pressure drop equation for two-phase flow in a mes-ochannel involving (a) vapor core in the center, (b) liquid layer on the wall, (c) spray droplets within the vapor core, and (d) entrained

Fluent Engine Combustion Injection

reactingboundary-layer flows, single energetic particle combustion, andgranular bed combustion Provides experimental setups and results wheneverappropriate Supported with a large number of examples and problems as wellas a solutions manual, Fundamentals of Turbulent and