Sauter Mean Diameter (SMD)

This review paper will deal with capabilities and limitations of available diagnostics and recent advancements of new methods used in spray characterization. Emphasis will be placed upon the quality of measured results when applied to difficult conditions and how these results are evaluated in terms of completeness of information and uncertainty in the measurements. A brief discussion of what information is required to fully characterize the spray will be provided. Argumentation will be presented for integration of experiments and modeling to advance our understanding in this area with greater efficiency. Finally, a criticism of our means of storing and distributing research information will be advanced. In particular, the current approach of publishing technical papers with limited lengths and information will be attacked.

With the aim of expanding the knowledge on liquid ammonia sprays, this paper investigates the injection process of ammonia through Computational Fluid Dynamics (CFD) using the Lagrangian particle method, within the Reynolds Averaged Navier Stokes (RANS) approach for turbulence modeling. Numerical results and experimental data are compared in terms of liquid and vapor tip penetration, local values of Sauter Mean Diameter (SMD) and global spray morphology. This model validation process allows to build a predictive simulation framework for ammonia injection. In order to explore also the flash boiling phenomenon, results of CFD simulations of ammonia spray and the comparison with experimental data are presented for different conditions, ranging from non-flashing regimes to flash boiling conditions. Breakup model constants need to be markedly tuned for each regime, and established values for traditional fuels, like gasoline, appear not to work well with ammonia. Ultimately, this study hi...

A survey of recent research at UTA on detonation waves related to propulsion is presented in this paper. A brief historical review of the early pulse detonation engine (PDE) research at UTA is provided to lay the background for the development of a large-scale PDE Ground Demonstrator. Also current activities related to the development of rotating detonation wave engines (RDE) are reviewed. System integration studies for both PDE-and RDE-based propulsion systems are summarized, followed by a brief description of two programs focusing on application of detonation waves to hypersonic flow simulation and power generation.

This experimental study presents an analysis of the air-water flow in rectangular free-falling jets. The measurements were obtained downstream of a 1.05 m wide sharp-crested weir. The properties of the air-water flow were registered in several cross-sections of the nappe. A conductivity phase detection probe was employed, sampling at 20 kHz. Three different specific flows were considered, with energy head over the crest of 0.080, 0.109 and 0.131 m to avoid scale effects. To analyze the flow properties, air-water parameters during the fall, such as the phase change spatial distribution, air-water phase change of frequency, Sauter mean diameter, bubble chord length, turbulent intensities and spectral analyses, were studied. The jet thickness behaviors (inner jet core and free surface) were also analyzed in the falling jet. The jet thickness related to a void fraction of 90% seems to be similar to the theoretical proposal obtained by , while the jet thickness related to a void fraction of 10% seems to be similar to the jet thickness due to gravitational effects. The results show relative differences in the behavior of the upper and lower sides of the nappe. The experimental data allow us to improve on and complement previous research.

Since the first meeting in Lyon in 1986, the biannual European Turbulence Conferences have provided an informative survey of the international efforts in understanding turbulence in its fundamental and applied aspects. Now integrated into the conference cycles coordinated by the European Mechanics Society the meetings provide a regular forum for the exchange of ideas and the discussion of the latest developments. The more recent conferences in Barcelona (2000), Southampton (2002), Trondheim (2004), and Porto (2007) have attracted several hundred participants from 30 and more countries. The 12th meeting in this series, ETC 12, which was held in Marburg September 7-10, 2009, continues this tradition. Researchers from 34 countries submitted 336 abstracts to the conference. The number of submissions is somewhat lower than for the Porto or Barcelona meetings, but in line with the previous ones in Northern Europe. The contributions that were presented in Marburg were selected by the international advisory board for the European Turbulence Conferences. The committee was chaired by Professor Arne V. Johannson (Stockholm) and consisted of Professors Helge I. Andersson (Trondheim), Konrad Bajer (Warsaw), Luca Biferale (Rome), Claude Cambon (Lyon), Hans-Hermann Fernholz (Berlin), Peter Davidson (Cambridge, UK), Yuri Kachanov (Novosibirsk), Detlef Lohse (Twente), Jose L. Palma (Porto), Jean-Francois Pinton (Lyon) and the local organizer. for oral presentation, corresponding to a record number of almost 75% of the submissions. In addition, 70 papers were selected for presentation in a poster and seminar session. These numbers attest to the healthy state of the field and the reputation the conferences have achieved. in the sections given in the table of contents. Naturally, the level of activity in the subareas varies from conference to conference. For ETC12, the largest numbers of submissions were recorded for the areas of instability and transition, and wall bounded flows. These were closely followed by intermittency Impressed by the high quality of the abstracts the committee selected 250 As in previous years, the papers are grouped by the subfields as reflected v

We investigated experimentally the shape of the final size PDF(D) resulting from the breakup of an air bubble injected into the fully developed region of a high Reynolds number turbulent water jet. It is shown that the PDF(D̂) of the normalized bubble size D̂=D/D32, where D32 is the Sauter mean diameter of the distribution, has a universal single shape independent of the value of the turbulent kinetic energy of the water jet at the bubble injection point and of the air void fraction, α. The shape of the exponential tails characterizing each PDF(D) is shown to be only a function of the initial bubble size D0 and the critical bubble size Dc, defined as Dc=(1.46σ/ρ)3/5ε−2/5, where ε is the value of the dissipation rate of turbulent kinetic energy per unit mass at the air injection point.

Self-excited thermo-acoustic instabilities (sometimes known as rumble) have impeded the development of lean burn low NOx gas turbine combustors. Acoustic waves in the combustor interact with the fuel/air mixing process to modulate fuel field properties e.g. air-fuel ratio (AFR). The fluctuating fuel field properties cause the heat release rate to fluctuate. If the Rayleigh criterion is obeyed i.e. the phase difference between the fluctuating heat release and the acoustic pressure is less than 90 o , the acoustic wave is amplified. The acoustic intensity can cause vibration and enhanced heat transfer sufficient to reduce the lifetime of the mechanical parts, as well as causing the operating noise levels to exceed regulatory limits.

Flow characteristics of bidisperse mixtures of particles fluidized by a gas predicted by the mixture based kinetic theory of Garzo ´et al. (2007a,b) and the species based kinetic theory model of are compared. Simulations were carried out in two-and three-dimensional periodic domains. Direct comparison of the meso-scale gas-particle flow structures, and the domainaveraged slip velocities and meso-scale stresses reveals that both mixture and species based kinetic theory models manifest similar predictions for all the size ratios examined in this study. A detailed analysis is presented in which we demonstrate when the species based theory of Iddir and Arastoopour (2005) will reduce to a mathematical form similar to the mixture framework of Garzo ´et al. (2007a,b). We also find that the flow characteristics obtained for bidisperse mixtures are very similar to those obtained for monodisperse systems having the same Sauter mean diameter for the cases examined; however, the domain-averaged properties of monodisperse and bidisperse gas-particle flows do demonstrate quantitative differences. The use of filtered two-fluid models that average over mesoscale flow structures has already been described in the literature; it is clear from the present study that such filtered models are needed for coarse-grid simulations of polydisperse systems as well.

affecting the combustion performance and emissions of the internal mixing air-assisted atomizers. Air-assisted atomizers are introduced to counter the low-pressure differential of a simplex nozzle, which reduces the atomization quality. The present study aims to determine the effects of Multi Circular Jet (MCJ) plates on the geometrical configurations of internal flows in mixing chamber and the internal flow of plate 3 using different properties of fuel. In this study, the realizable k-ε turbulence model, specifically designed for strongly swirling flows, is validated through numerical simulations. The turbulence model selected is a type of Reynolds averaged Navier-Stokes (RANS) model called the k-ε model. The MCJ plates provide the primary air entrance into the mixing chamber. Additionally, it acts as a turbulence generator and can be adjusted to alter the flow of fuel and air mixtures in a mixing chamber. The study compares several MCJ geometries in terms of pressure, speed, turbulent kinetic energy, and volume fraction and compares the performances of diesel and Crude Palm Oil (CPO) B30 biodiesel fuels. The findings imply that CPO B30 biodiesel has superior atomization and mixing due to its higher density and turbulent kinetic energy. CPO B30 biodiesel was compared to Diesel in terms of maximum pressure, average speed, turbulent kinetic energy per unit mass, and volume fraction. The results indicate that CPO B30 has lower pressure and higher velocity than Diesel, suggesting better fuel atomization and mixing. The higher density of CPO B30 leads to increased turbulent kinetic energy, improving fuel-air mixing inside the combustion chamber. The study demonstrates that the use of MCJ plates can enhance mixing in a mixing chamber. In addition, MCJ plates show the ability to control the spray and atomization. The findings of this study contribute to a better understanding of the relationships between geometry and fuel-air mixing, as well as the characteristics of the internal mixing airassisted atomizer, which will lead to future burner system improvements.

This study investigates numerically the atomization process occurring in a plain jet airblast atomizer. The population balance equation is solved for the dispersed phase coupled with a CFD Eulerian multi-fluid model. The Sauter mean diameter values obtained numerically compare favorably with previous experimental data only at certain flow conditions. Finally, this study proposes some enhancements on using the numerical model which were revealed from the model formulation and the results obtained.

Premix emulsification was investigated using packed beds consisting of micron-sized glass beads; a system that avoids fouling issues, unlike traditional premix membrane emulsification. The effects of emulsion formulation were investigated; most notably the viscosity and the surfactant. The droplet size was reduced by increased shear stress in the emulsion. This was stronger at low viscosity ratios than at high ratios. As expected, the flux was proportional to the overall emulsion viscosity, and emulsions with small droplet size (Sauter mean droplet diameter < 5 μm) could still be produced at up to 60% of dispersed phase provided that sufficient surfactant was available. More uniform emulsions (span ≈ 0.75) were produced with Tween-20 (nonionic) and SDS (anionic) as surfactants than with CTAB (a cationic surfactant), possibly due to a combination of a low equilibrium interfacial tension and electrostatic attractions with the glass surface. Scaling relations were proposed taking into account all investigated product properties that can describe the droplet size successfully.

The weaknesses of liquid propellants have led to special attention to gelled propellants in the last two decades as a way to overcome the weaknesses of these propellants. Previous studies have shown that the addition of gel-forming agents to liquid propellants converts these propellants, mainly Newtonian fluids, into non-Newtonian fluids, which greatly affects the physical properties of these propellants. In order to better understand the changes occurred in the physical properties of liquid propellants due to their gelled structure, on factors such as spraying and atomization, in this study, impinging jet injectors have been used to spray and atomize a non-Newtonian gelled fluid with rheological properties similar to gelled propellants. Analysis of the results of the present study shows that the use of impinging jet injectors causes different regimes of spraying and atomization (due to the jets' high Reynolds number) for non-Newtonian gelled fluids, some of which being fundamentally different from the regimes formed for Newtonian fluids. In general, 4 regimes including stable closed rim, unstable closed rim with the formation of vermicular ligaments, open rim with successive formation of bow-shaped ligaments and a turbulent regime have been identified in this study. The properties of each of these regimes and their details will be explained in this paper.

We investigated experimentally the shape of the final size PDF(D) resulting from the breakup of an air bubble injected into the fully developed region of a high Reynolds number turbulent water jet. It is shown that the PDF(D̂) of the normalized bubble size D̂=D/D32, where D32 is the Sauter mean diameter of the distribution, has a universal single shape independent of the value of the turbulent kinetic energy of the water jet at the bubble injection point and of the air void fraction, α. The shape of the exponential tails characterizing each PDF(D) is shown to be only a function of the initial bubble size D0 and the critical bubble size Dc, defined as Dc=(1.46σ/ρ)3/5ε−2/5, where ε is the value of the dissipation rate of turbulent kinetic energy per unit mass at the air injection point.

The accurate prediction of droplet sizes is fundamental in many industrial applications. In order to be able to simulate the evolution of a size distribution, suitable kernels should be used in the population balance. In this paper we make use of four different breakage kernels in order to predict a size distribution and compare the results among them as well as with experimental data. Two breakage kernels are derived from inverse problems and the other two are derived from physical or empirical interpretations. The Sauter mean diameter, a moments-based error and Gaussian shape factors were used to compare between the resulting distributions.

The efficiency of liquid/liquid dispersion is an important sake in numerous sectors, such as the chemical, food, cosmetic and environmental industries. In the present study, dispersion is achieved in an open-loop reactor consisting of simple curved pipes, either helically coiled or chaotically twisted. In both configurations, we investigate the drop breakup process of two immiscible fluids (W/O) and especially investigate the effect of the continuous phase viscosity, which is varied by the addition of different fractions of butanol in the native sunflower oil. The global Reynolds numbers vary between 40 and 240, so that the flow remains laminar while the Dean roll-cells in the bends develop significantly. Different fractions of butanol are added to the oil in each case to examine the influence of the continuous phase viscosity on the drop size distribution of the dispersed phase (water). When the butanol fraction is decreased, the dispersion process is intensified and smaller drops ...

The efficiency of liquid/liquid dispersion is an important sake in numerous sectors, such as the chemical, food, cosmetic and environmental industries. In the present study, dispersion is achieved in an open-loop reactor consisting of simple curved pipes, either helically coiled or chaotically twisted. In both configurations, we investigate the drop breakup process of two immiscible fluids (W/O) and especially investigate the effect of the continuous phase viscosity, which is varied by the addition of different fractions of butanol in the native sunflower oil. The global Reynolds numbers vary between 40 and 240, so that the flow remains laminar while the Dean roll-cells in the bends develop significantly. Different fractions of butanol are added to the oil in each case to examine the influence of the continuous phase viscosity on the drop size distribution of the dispersed phase (water). When the butanol fraction is decreased, the dispersion process is intensified and smaller drops ...

With the aim of expanding the knowledge on liquid ammonia sprays, this paper investigates the injection process of ammonia through Computational Fluid Dynamics (CFD) using the Lagrangian particle method, within the Reynolds Averaged Navier Stokes (RANS) approach for turbulence modeling. Numerical results and experimental data are compared in terms of liquid and vapor tip penetration, local values of Sauter Mean Diameter (SMD) and global spray morphology. This model validation process allows to build a predictive simulation framework for ammonia injection. In order to explore also the flash boiling phenomenon, results of CFD simulations of ammonia spray and the comparison with experimental data are presented for different conditions, ranging from non-flashing regimes to flash boiling conditions. Breakup model constants need to be markedly tuned for each regime, and established values for traditional fuels, like gasoline, appear not to work well with ammonia. Ultimately, this study highlights that capturing spray local details (such as local SMD values) across all the regimes with a single model or setup is still challenging, especially with a new fuel such as ammonia, whose properties differ by a large amount from more established values for hydrocarbons.

Spray drying is widely applied in many industries, such as the pharmaceutical, food, detergents, polymers, to convert liquids in solid particles. However, it still requires continuous innovation in order to provide more sophisticated particles, which are difficult to design by using only empirical approaches. In this context, a steady-state mathematical model for a co-current spray dryer is developed to give a more phenomenological insight in the production of inhalable particles. The model includes mass, energy and momentum balances for both particulate and gaseous phases. Particularly, and as a model inhalable compound, ciprofloxacin hydrochloride (CIP) aqueous solutions are studied. Several experimental data, obtained in a Mini-Spray Dryer B-290 BÜCHI, were available. In addition, droplet size measurements were carried out by using laser diffraction. The effect of the binary nozzle operating conditions on the mean droplet size was analysed and a correlation to predict the mean Sauter diameter was established. The experimental data are used to fit and validate the proposed model. The validated model is used to perform parametric studies in order to evaluate the effect of the main process variables on the final product properties (e.g., particle size and density, powder moisture content) and to track key powder attributes for pulmonary administration.

Spray drying is widely applied in many industries, such as the pharmaceutical, food, detergents, polymers, to convert liquids in solid particles. However, it still requires continuous innovation in order to provide more sophisticated particles, which are difficult to design by using only empirical approaches. In this context, a steady-state mathematical model for a co-current spray dryer is developed to give a more phenomenological insight in the production of inhalable particles. The model includes mass, energy and momentum balances for both particulate and gaseous phases. Particularly, and as a model inhalable compound, ciprofloxacin hydrochloride (CIP) aqueous solutions are studied. Several experimental data, obtained in a Mini-Spray Dryer B-290 BÜCHI, were available. In addition, droplet size measurements were carried out by using laser diffraction. The effect of the binary nozzle operating conditions on the mean droplet size was analysed and a correlation to predict the mean Sauter diameter was established. The experimental data are used to fit and validate the proposed model. The validated model is used to perform parametric studies in order to evaluate the effect of the main process variables on the final product properties (e.g., particle size and density, powder moisture content) and to track key powder attributes for pulmonary administration.

The effects of air temperature and air pressure on spray quality of a moderately high capacity pressure swirl atomizer (127 kg/h MPa or 23.3 lbm/h psid) spraying jet-A and No. 2 diesel fuel have been examined. Drop-size distributions, in terms of both Sauter mean diameter (SMD) and the width of the distribution as given by the Rosin-Rammler N parameter, and cone angle as measured close to the nozzle (10-mm distance) have been determined over a variety of air conditions. A new correction procedure was developed to extend diffraction-based drop-size measurements in dense sprays from maximum optical opacities of 50% to maximum opacities of 96%, equivalent to an increase in spray density of a factor of five. Drop-size measurements are reported for a temperature range of room temperature (297K) to 589K and air pressures of atmospheric (101 kPa) to 597 kPa. Cone angle data are reported for temperatures to 589K and pressures to 1318 kPa. The maximum operating temperature was limited to the...

When an oil-in-water emulsion is utilized for application in a flat-fan spray, micrometer-sized oil droplets are thought to facilitate hole formation on the spray lamella, leading to an earlier breakup of the spray sheet and an increase in resulting droplet sizes. However, prior work has largely focused on changes to the mean or median droplet size, and has not examined the influence of oil-in-water emulsions on the complete droplet size distribution, as well as other droplet properties such as droplet shape and droplet initial velocity distributions in flat fan sprays. This study concerns the effects of pressure, spatial location, and application of oil emulsions on the resulting droplet size, eccentricity, as well as velocity distributions, all of which are crucial information in determining the dispersion dynamics of the droplets during the spray applications. Experiments were conducted with a TP6515 nozzle, with the abovementioned droplets information measured using digital inline holography (DIH). Results show that the DIH-inferred volumetric droplet size distributions (VDSD) span widely from sub-200 µm to over 2 mm in size. The application of an oil-in-water emulsion results largely in suppression of smaller droplets, while the VDSD is relatively insensitive to increasing the oil volume fraction beyond a critical level. DIH results are consistent with the observation that smaller ligaments are observed only in the breakup regions for the single phase water sprays, which breakup more violently and earlier than larger ligaments. It is these smaller ligaments that are suppressed in the oil-in-water emulsion, and which yield sub-millimeter droplets, some with sizes approaching sub-200 µm dimensions, corresponding to driftable sizes in agricultural settings. DIH additionally enables determination of size dependent droplet eccentricity and velocity measurements. Interestingly, the application of oil-in-water emulsion generally decreases the eccentricity, more significantly at the center than at the edge of the spray fan. We attribute this decrease to the increase in lamella sheet thickness and thus decrease in characteristic shrinkage rates, consistent with the observation using high speed shadowgraphs. In all instances, oil-in-water emulsion droplets have higher velocities than equivalent sized water droplets. We attribute this to the earlier action of the spray breakup process in the oil-in-water emulsion, reduced surface energy generation during breakup (larger droplets), and reduce energy dissipation during breakup with oil-in-water emulsions, leading to increased translational energy after the breakup process. Therefore, it appears that oil-in-water emulsion application simultaneously suppresses small droplet formation and increases droplet velocity, and hence spray penetration in agricultural application.

Modelling of gas-liquid bubbly flows is achieved by coupling a population balance equation with the three-dimensional, two-fluid, hydrodynamic model. For gas-liquid bubbly flows, an average bubble number density transport equation has been incorporated in the CFD code CFX 5.7 to describe the temporal and spatial evolution of the gas bubbles population. The coalescence and breakage effects of the gas bubbles are modeled. The coalescence by the random collision driven by turbulence and wake entrainment is considered, while for bubble breakage, the impact of turbulent eddies is considered. Local spatial variations of the gas volume fraction, interfacial area concentration, Sauter mean bubble diameter, and liquid velocity are compared against experimental data in a horizontal pipe, covering a range of gas (0.25 to 1.34 m/s) and liquid (3.74 to 5.1 m/s) superficial velocities and average volume fractions (4% to 21%). The predicted local variations are in good agreement with the experimen...

Complete modeling of a new ultrasonic atomizer, the Spray On Demand (SOD) printhead, was carried out to enable its optimization. The modeling was focused on various factors, including nozzle vibrations and a theoretical prediction of the SOD drop-size distribution. Assuming that the spray is generated based on Faraday instability, a prediction of the drop-size distribution within the framework of a specific and general Maximum Entropy Formalism (MEF) was developed. This prediction was formulated using the conservation laws of energy and mass, as well as the three-parameter generalized Gamma distribution. After establishing an analytical expression to estimate the Sauter Mean Diameter, a qualitative validation of the model was performed by comparing predictions with experimental measurements of the dropsize distribution. The dynamic model is shown to be sensitive to operating conditions and physical properties of the fluid. The prediction capabilities of the model were found to be adequate, paving the way for optimization of the atomizer. The evolution of the drop-size distribution, under the coalescence effect, was also assessed using a convergent Monte Carlo method to solve the distribution equation. This was formulated in a mass flow algorithm, leading to a more physically relevant distribution.

BIODIESEL SPRAY CHARACTERISTICS. This paper presents analytical evaluation of biodiesel blends with diesel filels using indirect injection spray injector. The biodieselunder study is a 60:40 blend of used frying oil (from palm) and jatropha oil. The reason for selecting this composition is the best trade off for obtaining oxidation stability and saturation properties. Used frying oil is selected for economical reason. The physicochemical properties, i.e. density, suiface tension, and viscosity, are evaluated for B100, B5, B10, B20, and B30. Such data are required for input parameters of a spray modelling which is under preparation. The above properties can be used to predict the spray characteristics under typical injection pressure and air density. In this study, only the Sauter mean diameter (SMD) is evaluted using semi-empirical formulae from other study. It is found that the SMD for the above biodiesel blend is 24.6 f1l1J, compared with 20.4 flm for pure diesel filel. The SMD for other compositions are also evaluated up to B30; in which it is found that the SMD is 21.6 flm. The effect of injection pressure is also studied.

Uniformly sized droplets of soybean oil, MCT (medium-chain fatty acid triglyceride) oil and n-tetradecane with a Sauter mean diameter of d 3,2 = 26-35 µm and a distribution span of 0.21-0.25 have been produced at high throughputs using a 24 × 24 mm silicon microchannel plate consisting of 23,348 asymmetric channels fabricated by photolithography and deep reactive ion etching. Each channel consisted of a 10-µm diameter straight-through micro-hole with a length of 70 µm and a 50 × 10 µm micro-slot with a depth of 30 µm at the outlet of each channel. The maximum dispersed phase flux for monodisperse emulsion generation increased with decreasing dispersed phase viscosity and ranged from over 120 L m -2 h -1 for soybean oil to 2700 L m -2 h -1 for n-tetradecane. The droplet generation frequency showed significant channel to channel variations and increased with decreasing viscosity of the dispersed phase. For n-tetradecane, the maximum mean droplet generation frequency was 250 Hz per single active channel, corresponding to the overall throughput in the device of 3.2 million droplets per second. The proportion of active channels at high throughputs approached 100% for soybean oil and MCT oil and 50% for n-tetradecane. The agreement between the experimental and CFD (Computational Fluid Dynamics) results was excellent for soybean oil and the poorest for n-tetradecane.

In spray studies related to selective catalytic reduction (SCR) systems a common approach is to replace the urea–water solution (UWS) with pure water, even though there is very limited detailed information on the spray properties for these two liquids obtained under the same conditions using the same experimental equipment. Neither is it known how the possible differences in spray properties influence computational fluid dynamics (CFD) simulations. In this study, besides the flow characteristics, we compare both global and local spray parameters measured for UWS and pure water in the same conditions. To our knowledge, this is the first study which examines the influence on the injection process of replacing UWS with water over such a wide range. Moreover, the influence of different spray properties on CFD simulations is also examined. The experimental studies showed differences in almost all considered spray parameters. Moreover, different spray behaviour was noticed in terms of pri...

There have been continuing efforts in the Engine Combustion Network (ECN) community to understand the detailed spray characteristics by investigating several standard diesel injectors. With the increasing interest in the use of alternative and renewable fuels, the present study conducted large eddy simulations with dynamic structure subgrid closure in the Eulerian volume-of-fluid (VOF) framework to identify the characteristics of oxymethylene ethers (OME), which has distinct physical and chemical properties leading to low soot emissions. In particular, the spray features of n-dodecane and OME3 were compared and analyzed in terms of their transient dynamics following the nozzle opening. ECN Spray A, C, and D were considered to assess the effects of nozzle convergence factor and nozzle diameter. The measured nozzle geometries by the Argonne National Laboratory were adopted to mimic the internal flow development. Due to the higher density of OME3, it generates a higher projected density, but a lower injection velocity is obtained. This behavior is attributed to its higher mass inertia. The diverging Spray C injector induces a significantly lower projected density and mass flow rate than the converging Spray D injector owing to cavitation just after the sharp nozzle inlet corner. By comparison, the Spray A injector generates the lowest projected density and mass flow rate for its smallest nozzle diameter. Various fuels demonstrate similar flow fields, evidenced by the significantly similar pressure distribution. The OME3 cases lead to a slightly higher temperature distribution within the nozzle channel, which is attributed to the lower turbulent kinetic energy and thus the slower heat transfer process.

We investigated experimentally the shape of the final size PDF(D) resulting from the breakup of an air bubble injected into the fully developed region of a high Reynolds number turbulent water jet. It is shown that the PDF(D̂) of the normalized bubble size D̂=D/D32, where D32 is the Sauter mean diameter of the distribution, has a universal single shape independent of the value of the turbulent kinetic energy of the water jet at the bubble injection point and of the air void fraction, α. The shape of the exponential tails characterizing each PDF(D) is shown to be only a function of the initial bubble size D0 and the critical bubble size Dc, defined as Dc=(1.46σ/ρ)3/5ε−2/5, where ε is the value of the dissipation rate of turbulent kinetic energy per unit mass at the air injection point.

The aim of this paper is to investigate the influence of physico-chemical parameters on liquid-liquid dispersion at high dispersed phase concentration in Sulzer SMV TM mixer. Four different oil-in-water systems involving two different surfactants are used in order to evaluate the effect of interfacial tension, densities and viscosities ratio on mean droplets size diameters. Moreover the influence of the dispersed phase concentration on the pressure drop as well as on the droplet size distribution is investigated. Two different droplets size distribution analysis techniques are used in order to compare the resulting Sauter mean diameters. The comparison between residence time in the mixer and surfactants adsorption kinetics leads to take into account the evolution of the interfacial tension between both phases at short times. Finally experimental results are correlated as a function of dimensionless Reynolds and Weber numbers.

A series of studies were undertaken to measure various parameters such as velocity, species concentration, and temperature downstream of a shear coaxial injector in an optically accessible uni-element rocket chamber. Techniques applied include: laser Doppler velocimetry (LDV) for velocity; laser light scattering (LLS) for flow visualization and estimating mixture fraction and density; laser induced fluorescence (LIF) of hydroxyl radials (OH) to determine the characteristics and extent of the reaction zone; and Raman spectroscopy to measure major species concentration and temperature.

A single-hole effervescent atomizer spraying light heating oil (LHO) with air as atomizing medium in “outside-in” gas injection configuration was studied using PIV-PLIF. Influence of operation conditions and atomizer internal design on 2D droplet velocity field, liquid phase concentration and liquid flux in the spray was investigated. Inlet pressure and gas-to-liquidratio (GLR) were varied. Several design parameters were modified: size and number of aeration holes, their location, diameter of mixing chamber and discharge orifice shape. Increase of GLR in examined range 2-10 % leads to increase of the droplet velocity in entire radial profile but particularly near the spray axis and to decrease of spray cone half-angle for all atomizer configurations. Increase in atomization pressure in the range 0.1 - 0.5 MPa causes increase of velocity through all radial profile and indistinctive expansion or reduction of the halfangle depending on atomizer design. The spray cone half-angle ranges ...

An analysis is conducted on the effective mean diameter for fluidized beds and other two-phase flows for which the drag and gravitational forces are the primary determinants of particle motion. This work was motivated by Eulerian-based computational treatments of particles which assume a single group velocity for a polydisperse collection of particles within a computational cell. For particles in the inertialdominated regime (e.g. Re p >2000), it is found that the Sauter mean diameter is the effective mean diameter regardless of particle shape, particle size number distribution, particle density distribution, or net volume fraction. However, the effective mean diameter is the volumewidth diameter for particles which are in the creeping flow regime (Re p b1), e.g. in micro-fluidized beds. Expressions for the effective diameter for solid spherical particles at intermediate Reynolds numbers are given for a log-normal probability distribution function and for binary mixtures. Finally, comparison with two experimental data sets shows a qualitative validation of the derived effective diameter for the group motion of polydisperse mixtures.

Experiments were conducted in 0.05 m ID and 0.23 m ID by 3 m tall bubble columns with different types of molten waxes as the liquid medium and nitrogen as the gas, under processing conditions typical or Fischer-Tropsch synthesis over iron catalysts (i.e. gas velocities up to 0.15 m s, and temperatures between 200 and 270°C) to estimate gas liquid

The work presents a numerical investigation of gasoline direct injection and the resulting early development of spray plumes from an eight-hole injector (Engine Combustion Network Spray G). The objective is to evaluate the impact on the droplet size distribution (DSD) statistics from the assumed model physics, particularly for the small scales. Two modelling approaches are compared: Eulerian–Lagrangian spray atomisation with adaptive mesh refinement and a stochastic fields transported probability density function method. The two models simulate the small scales and sub-grid droplet physics with different approaches, but based on the same concept of transport of liquid surface density. Both approaches predict similar liquid distributions in the near-field comparable to experimental measurements. The spray break-up patterns are very similar and both models reproduce quasi-log-normal droplet distributions, with same overall Sauter mean diameters. The Eulerian–Lagrangian spray atomisati...

A stochastic subgrid model for the droplet breakup in large eddy simulation is developed. An Eulerian description of the continuous phase is adopted and fully coupled with a Lagrangian definition of the dispersed phase. A stochastic model is incorporated into the equation describing the evolution of the spray probability density function in order to simulate the atomization of sprays in the framework of uncorrelated breakup events. The results of the simulations are compared with experimental data from a diesel injector and in spray in cross flows.

A nondimensionalized plot, obtained by normalizing the drop‐size distribution in the hydrocarbon phase using the Sauter mean diameter, shows a tendency towards self‐preservation of the distribution. Changes of distribution in time during the course of fermentation, initial dispersed phase fraction, speed of rotation, and reactor size were taken into account. Using this self‐preserving property, an empirical (single parameter) equation has been proposed for drop‐size distribution. Data, available from the literature, are presented for non‐biological and biological systems (gas‐oil, n‐hexadecane, and n‐hexadecane dissolved in dewaxed gas oil as dispersed phases). The parameter, Sauter mean diameter, has been correlated with the operating conditions, and a critical review presented. Cell density was found to have significant effect on Sauter mean diameter. This effect has also been empirically explained. The possibilities of using generalized distribution in predicting the performance ...

There have been continuing efforts in the Engine Combustion Network (ECN) community to understand the detailed spray characteristics by investigating several standard diesel injectors. With the increasing interest in the use of alternative and renewable fuels, the present study conducted large eddy simulations with dynamic structure subgrid closure in the Eulerian volume-of-fluid (VOF) framework to identify the characteristics of oxymethylene ethers (OME), which has distinct physical and chemical properties leading to low soot emissions. In particular, the spray features of n-dodecane and OME3 were compared and analyzed in terms of their transient dynamics following the nozzle opening. ECN Spray A, C, and D were considered to assess the effects of nozzle convergence factor and nozzle diameter. The measured nozzle geometries by the Argonne National Laboratory were adopted to mimic the internal flow development. Due to the higher density of OME3, it generates a higher projected density, but a lower injection velocity is obtained. This behavior is attributed to its higher mass inertia. The diverging Spray C injector induces a significantly lower projected density and mass flow rate than the converging Spray D injector owing to cavitation just after the sharp nozzle inlet corner. By comparison, the Spray A injector generates the lowest projected density and mass flow rate for its smallest nozzle diameter. Various fuels demonstrate similar flow fields, evidenced by the significantly similar pressure distribution. The OME3 cases lead to a slightly higher temperature distribution within the nozzle channel, which is attributed to the lower turbulent kinetic energy and thus the slower heat transfer process.

Particle size is a key design variable in minerals beneficiation. Given declining grades in mineral ore reserves, finer grinding is being used to increase mineral liberation, leading to increased milling energy input. The particle size from the mill also has an effect on water recovery in downstream dewatering systems. This paper presents models for water recovery from the downstream thickening, filtration and tailings permeation and decantation processes, using Sauter Mean Diameter to characterise average particle size. On the basis of these models, a relationship between mill energy consumption and water recovery is established. To test the effect of particle size on these processes, data drawn from an industrial case study is used. The results confirm that as mill energy is increased, the particle size is decreased resulting in lower water recovery from the dewatering systems. This makes it possible to explore the trade-off between energy, liberation and water recovery.

Bubble point (L + V f L) and dew point (L + V f V) pressures were measured for the binary system CO 2 + CHF 3 , using Cailletet equipment. The measurements were carried out for the whole mole fraction range and for temperatures from 263 K up to the mixture critical points. The experimental data were used to determine binary interaction parameters for the Peng-Robinson equation of state with a Stryjek and Vera modification (PRSV) and a Margules-type binary interaction parameter.

Summary In this study we present a review of fluid–particle–size prediction models and a comprehensive database acquired from the open literature. The study is restricted to bubbles and droplets that are also called fluid particles. The data have been classified by flow regimes—namely, bubble, annular, liquid/liquid, and liquid/liquid through a restriction. Only studies in which the particle–size distribution is presented were considered. These distributions were used to calculate the experimental maximum, minimum, and Sauter mean diameters. A lack of experimental data for high–pressure and low–surface–tension systems has been identified. We use the database to evaluate the reviewed models and present the results. On the basis of the comparisons, we recommend models for particle–size predictions for the considered flow regimes.

A critical review on the improvement of penetration theory is presented in this work. The volumetric liquid-phase mass transfer coefficients kLa in seven different liquids (1-butanol, 2-propanol, anilin, decalin, nitrobenzene, tetralin, and ethylene glycol) aerated with air in a small bubble column (BC) (inner diameter: 0.095 m) were measured at ambient conditions and further analyzed. It was found that the kLa values can be predicted satisfactorily on the basis of the classical Higbie’s penetration model. The gas–liquid contact time was defined as the ratio of the Sauter-mean bubble diameter to bubble rise velocity. Moreover, the experimental kLa values were well predicted, not only in the homogeneous regime, but also in the transition and heterogeneous regimes. This is a new finding, since to date, it was considered that the penetration theory needs a correction factor for a successful application to any liquid, even in the homogeneous regime. The predictions of the mass transfer ...

Planar droplet sizing (PDS) is a technique relying on the assumption that laserinduced fluorescence (LIF) and Mie scattering optical signals from spherical droplets depend on their volume and surface area, respectively. In this article, we verify the validity of this assumption by experimentally analyzing the light intensity of the LIF and Mie optical signals from micrometric droplets as a function of their diameter. The size of the droplets is controlled using a new flow-focusing monodisperse droplet generator capable of producing droplets of the desired size in the range of 21 µm to 60 µm. Ethanol droplets doped with eosin dye and excited at 532 nm are considered in this study, and the individual droplets were imaged simultaneously at microscopic and macroscopic scale. The effects of laser power, dye concentration, and temperature variation are systematically studied as a function of LIF/Mie ratio in the whole range of droplet sizes. Finally, a calibration curve at tracer concentration of 0.5 vol% is deduced and used to extract the droplet Sauter mean diameter (SMD) from instantaneous images of a transient ethanol spray. This droplet size mapping is done using structured laser illumination planar imaging (SLIPI), in order to suppress the artifacts induced by multiple light scattering.

In this study, we report on the 3D (three-dimensional) characterization of a spray in terms of its droplet SMD (Sauter Mean Diameter) using the LIF (Laser-Induced Fluorescence)/Mie ratio technique. The spray structure is analyzed for a multi-hole DISI (Direct-Injection Spark Ignition) injector. A calibration curve to convert LIF/Mie ratio to droplet diameter is deduced using LIF/Mie imaging and analysis of single droplets generated by a droplet generator. The DISI spray investigated here is optically sectioned by means of two-phase SLIPI (Structured Laser Illumination Planar Imaging) to suppress the intensity of multiple light scattering from LIF and Mie images prior to their ratio. A series of calibrated LIF/Mie ratio images of spray is then recorded at several depths along the Z-direction following the light sheet scanning of the spray. The droplet SMD is ranging from less than 5 µm up to a maximum of 50 µm in single-shot images. The averaged SMD results (1-30 µm) obtained by using the calibration curve from the droplet generator are compared with measurement results from Phase-Doppler Anemometry (PDA). Finally, a 3D map is reconstructed from the successive 2D layers generated from spray scanning. The resulting 3D representation of the droplet SMD shows a non-symmetric spray structure produced by the studied multi-hole injector, which cannot be resolved by analyzing only one central plane.

This paper reports on the spray structure of the biofuels, ethanol, and butanol generated by a multihole direct-injection spark-ignition injector, which is studied in a constant volume chamber. The spray shape and structure are analyzed using two-phase structured laser illumination planar imaging where both laser-induced fluorescence and Mie-scattering light are recorded simultaneously for the extraction of instantaneous laser-induced fluorescence/Mie-scattering ratio images. Quantitative planar measurements of the droplet Sauter mean diameter are conducted, using calibration data from phase-Doppler anemometry. The resulting Sauter mean diameters are presented for ethanol and butanol at various fuel temperatures at different times after the start of injection. It is found that an increase in fuel temperature results in a faster atomization and higher evaporation rate, which leads to reduced spray tip penetration and smaller droplet Sauter mean diameter. At equivalent conditions, butanol consistently showed larger spray tip penetration in comparison to ethanol. This behavior is due to the higher surface tension and viscosity of butanol resulting in the formation of larger droplets and larger Sauter mean diameters in the whole spray region. Finally, the butanol injection also shows larger cyclic variations in the spray shape from injection to injection which is explained by the internal nozzle flow that is influenced by larger fuel viscosity as well. The Sauter mean diameter distribution is also compared to phase-Doppler anemometry data showing good agreement and an uncertainty analysis of the structured laser illumination planar imaging-laser-induced fluorescence/Mie-scattering technique for planar droplet sizing in direct-injection spark-ignition sprays is presented.

In this work, we report an original experimental approach for measuring the two-dimensional distribution of the droplets Sauter Mean Diameter (SMD) using the SLIPI-LIF/MIE technique. A hollow-cone spray is formed by continuously injecting water mixed with a non-toxic fluorescing dye at 20 bars injection pressure. The spray is illuminated using a continuous wave laser. The illumination wavelength (here, 447 nm) is carefully chosen to excite the injected dye/water mixture, which generates a significant Laser Induced Fluorescence (LIF) signal peaking at 514 nm. The LIF and Mie signals are simultaneously recorded using two CCD cameras and their intensity ratio is used to extract a two-dimensional distribution of the droplets SMD. In this article, we show that even for the case of a dilute hollow-cone spray, where single scattering events are in majority, the LIF/Mie measurement of droplets SMD still remains strongly affected by multiple light scattering. We demonstrate, then, that the use of SLIPI is unavoidable to obtain trustable SMD measurements based on the LIF/Mie ratio, even for optically dilute sprays.

This paper reports on the first realization of two-phase SLIPI (Structured Laser Illumination Planar Imaging) in combination with LIF/Mie ratio imaging for a single shot mapping of relative SMD (Sauter Mean Diameter) in a transient fuel spray. The technique is applied to a non-combusting multi-jet DISI (direct-injection spark-ignition) spray of ethanol fuel injected into an optically accessible constant volume chamber. The organic dye Eosin is added to the fuel as a laser-induced fluorescence (LIF) tracer when illuminated by the 532nm laser sheet. It is found that SLIPI produces more reliable relative SMD distributions in comparison to the conventional LIF/Mieapproach. Multiple scattered light is suppressed by the SLIPI technique and the background spray plumes and artifacts behind the illuminated plane are successfully suppressed. The single-shot SLIPI images give a clear insight into the highly turbulent liquid spray structure and provide reliable information on the spatial droplet distribution.

We demonstrate the use of Light Sheet Fluorescence Microscopic (LSFM) imaging for viewing the dynamic of atomizing sprays with high contrast and resolution. The technique presents several advantages: first liquid fluorescence gives a more faithful representation of the structure of liquid bodies, droplets and ligaments than Mie scattering does. The reason for this is that the signal is emitted by the fluorescing dye molecules inside the liquid itself and not generated at the air-liquid interfaces. Second, despite the short depth of field (~0.2 mm) obtained when using the long range microscope, the contribution of out-of-focus light is much smaller on a light sheet than on a line-of-sight configuration providing more clearly sectioned images. Finally by positioning the light sheet on the spray periphery, toward the camera objective, the effects due to multiple light scattering phenomena can be reduced to some extent. All those features provide, for many spray situations, images with high fidelity of the liquid fluid, allowing the extraction of the velocity vectors at the liquid boundaries. Here, double frame images were recorded with a sCMOS camera with a time delay of 5 µs between exposures. A typical pressure-swirl atomizer is used here producing a water hollow-cone spray which was imaged between 20 bars and 100 bars in liquid injection pressure. Such data are important for the validation of CFD models simulating liquid breakups in the near-field spray region.