Mean Drop Size Research Articles

Liquid-liquid two phase-system stabilized by tween 40 and 80 surfactants: multiparametric study

Abstract The purpose of this study was to investigate the impact of process parameters such as interfacial tension, type of surfactants, and their concentration on simple oil-in-water dispersion. Explored systems were prepared with 5% liquid paraffin oil and aqueous phase with emulsifiers Tween 40 of concentrations from 0.008325 mM to 0.025 mM and Tween 80 with concentrations ranging from 0.00375 mM to 0.011 mM. All systems were characterized in terms of their density and interfacial tension. In the next step analysis of droplet size distributions and mean droplet diameter was performed. The results showed that the size of paraffin droplets decreased as the concentration of surfactants grew. This trend is accompanied by decrease in the interfacial tension between phases. The correlation between mean drop size and the energy input and physical properties of both liquids was developed. The last step provides scientific evidence for the formulation of stable droplets of liquid paraffin.

Forecasting Sauter mean droplet size and examining the range of droplet sizes in a Tenova liquid–liquid extraction column

A new type of Tenova pulsed extraction column was introduced in 2017. It is the newest generation of pulsed columns. Due to the internal equipment of this column and the lack of moving parts and the simplicity and speed of repairs and maintenance, it has been the focus of researchers in recent years. No correlations for predicting the mean drop size and drop size distribution of the Tenova column have been reported. The Sauter mean drop diameter and drop size distribution are investigated for a Tenova pulsed column with a diameter and an active height of 7.4 and 73 cm, respectively. Three standard chemical systems of isobutyl acetate-water, isobutanol-water, and toluene-water have been used. The effects of pulse intensity, dispersed and continuous phase flow rates have been taken into account. In each experiment, 200–300 drops have been analyzed in a total of 10,000 drops. The investigation covered a spectrum of physical properties, notably surface tension (within a range of 1.75–36 mN/m). Operating conditions including pulse intensity (in the range of 0.2–2 cm/s) and the flow rate of continuous and dispersed phases (in the range of 8–30 L/h) have been investigated. Methods based on artificial intelligence (AI) such as multilayer perceptron neural networks and gene expression programming were combined with a dimensional analysis approach to provide a new approach to estimating the mean drop diameter (d32). Experimental results have been compared with the equations found by other researchers in similar columns. The variation of drop size distribution has also been experimentally obtained.Methods based on artificial intelligence (AI) such as multilayer perceptron neural networks and gene expression programming were combined with a dimensional analysis approach to provide a new approach to estimating the mean drop diameter (d32). Experimental results have been compared with the equations found by other researchers in similar columns. The variation of drop size distribution has also been experimentally obtained.

Effects of secondary breakup, collision dynamics, gravity and evaporation on droplet size distribution in a pressure-swirl JET A-1 spray

Size and velocity of droplets in pressure-swirl sprays vary with distance downstream the nozzle. This study aims to explain the phenomena contributing to size-resolved spatial variation of the drop size distribution for Jet A-1 spray from a small pressure swirl atomizer injected into quiescent ambient air at atmospheric conditions. The effects of secondary breakup, droplet collisions, gravity, drag-driven spray dispersion, and evaporation are evaluated. Phase Doppler anemometer (PDA) was used to resolve the velocity and size of the droplets in radial profiles at several axial distances (Z) from the nozzle exit at injection pressures between 0.5 and 1.5 MPa. The droplet motion and collision dynamics were qualitatively characterised by high-speed imaging. The analysis focused on areas along 1) the spray axis and 2) the liquid sheet direction. The first area covers small droplets with marginal evolution, while the mean drop size in the second area significantly increases downstream. The local drop size distribution and its axial evolution results from a combined effect of ballistic filtering (drifting of small droplets from periphery to spray centre and large droplets vice versa), centrifugal and turbulent droplet dispersion, and droplet collisions (increasing drop size with distance). The relative droplet-gas velocity was found at investigated Z positions too small for drag-driven secondary droplet breakup to occur. Evaporation of Jet A-1 sprayed at room temperature and pressure into still atmosphere reduces the drop size marginally. Trajectory of all drop sizes is insignificantly altered by gravity. The smallest droplets are strongly drag-driven to the spray axis, while large ones disperse centrifugally and have sufficient momentum to neglect the gravity. Combining results from imaging and laser diagnostics, various collision outcomes were identified, with a conclusion that these depend on the size and velocity of colliding droplets. Coalescing collisions dominate and strongly increase the mean drop size downstream the spray at off-axis positions while insignificantly contribute along the spray axis. The drop size span factor reduces with Z as separative collisions between large droplets and mixed-type collisions between small and large droplets narrow the drop size distribution. The above effects can be most easily amplified for drop size reduction via modification of physical properties of sprayed liquid by its heating.

Experimental modeling of mean drop size and dispersed phase holdup in rotating disc contactors, using RSM

In this study, the behavior of hydrodynamic parameters was investigated in agitated columns including Asymmetric rotating disc contactor (ARDC), Perforated rotating disc contactor (PRDC), Oldshue–Rushton column (ORC), and Kuhni. The effects of various parameters, including rotor speed (rpm), dispersed and continuous phase velocities, interfacial parameters, and type of RDCs on the dispersed phase holdup and Sauter mean drop diameter were studied. The response surface methodology (RSM) based on the central composite design (CCD) approach was applied for the experimental modeling of three standard systems including toluene-water, butyl acetate-water, and butanol-water. Results showed that the enhancement of rotor speed and dispersed and continuous phase velocities would enhance the dispersed phase holdup. PRDC showed the least enhancement of dispersed phase holdup compared to the other three columns. Our investigation demonstrated that Sauter mean droplet diameter decreased with the rotor speed increase, and this declining trend is more appreciable in ORC and Kuhni columns. Additionally, by increasing dispersed phase velocity in the four columns, the droplet size in the ORC column is larger than the columns. However, by increasing continuous phase velocity, subtle changes in droplet size was observed. Based on the experimental data, new correlations have been presented to predict Sauter mean drop diameter and dispersed phase holdup for agitated columns by analysis of variance (ANOVA). The coefficient of determination (R2) was obtained to be 0.9612 and 0.9495 for Sauter mean drop diameter and dispersed phase holdup, respectively, indicating a good correlation between the predicted and observed values of the models.

Effect of surfactants and interfacial rheology on equilibrium drop size in turbulent liquid-liquid dispersions

Surfactants are often required to stabilize liquid-liquid dispersions produced by high shear mixers. Due to the high power input, drops are deformed rapidly in the dispersion zone so the dynamic interfacial properties governed by the surfactant adsorption rate can have a significant impact on the resulting drop size. The objective of this work is to develop a fundamental link between surfactant adsorption dynamics, interfacial properties, and turbulent emulsification processes. To ensure constant bulk surfactant concentration during dispersion, equilibrium drop size for dilute dispersions produced by a batch rotor-stator mixer were studied. Silicone oils of various viscosity were dispersed in aqueous nonionic surfactant solutions. Drop size distributions (DSD) were measured via a video microscopy/automated image analysis technique. Equilibrium interfacial tension was measured via a pendant drop technique, as a function of surfactant concentration. The dynamic surface tension was similarly measured. The data were fit to the Langmuir adsorption isotherm and the long-times approximation to the Ward – Tordai equation and the adsorption parameters and surfactant diffusivities so obtained were employed, with an estimate of the drop deformation timescale, to estimate the surface dilational modulus (Esd) or Marangoni stress acting on the drop’ surface due to interfacial tension gradients. Trends observed in the measured equilibrium mean drop size and DSD are explained in terms of the interfacial and rheological properties. Below the CMC, Esd peaks and the drop size increases with bulk surfactant concentration, despite a decrease in equilibrium interfacial tension. Above the CMC, Marangoni stresses are small but the presence of the surfactant still modifies the rheology of the interface, increasing the effective viscosity of the drops. A comprehensive set of mechanistic models for drop size in turbulent flows, based on Kolmogorov-Hinze theory, was developed and modified to partially account for the effect of surfactants via an appropriately defined effective viscosity. The approach allows integration of surfactant phenomena into widely accepted correlations for drop size in surfactant free systems.

Emulsions Using a Vortex-Based Cavitation Device: Influence of Number of Passes, Pressure Drop, and Device Scale on Droplet Size Distributions.

Liquid-liquid emulsions are used in a variety of industry sectors, including personal care, home care, food, and nutrition. The development of compact and modular systems and devices for creating emulsions with desired droplet size distribution (DSD) is becoming increasingly important. In this work, we have shown use of vortex-based cavitation devices for producing emulsions at nominal flow rate of 1 LPM and 20 LPM. We present new experimental results providing quantitative information on influence of multiple passes through the vortex based hydrodynamic cavitation (HC) device, type of oil and device scale on the breakage process and resulting DSDs. Multiple pass experiments were performed for generating oil-in-water emulsions containing 5 and 15% of oil. Rapeseed oil (RO) and tetrachloroethylene (TCE) were used as oil phases with densities of 915 and 1620 kg/m3, respectively. The effect of pressure drop across the HC device in the range of 50-250 kPa on DSD was examined. The HC device was shown to exhibit significant higher efficiency compared to alternative emulsion making devices (i.e., homogenizers, venturi, and orifice-based HC devices), and the Sauter mean drop size was found to reduce from 66 μm to less than 2 μm after about 50 passes in all the device scales. The DSD of the RO-water system showed a bimodal nature, whereas monomodal DSD was found for TCE-water system. Preliminary simulations using the computational fluid dynamics-population balance model (CFD-PBM) models developed in the previous work indicated the inadequacy of developed models to capture the influence of cavitation on DSDs. By carrying out Hinze scale analysis of bimodal DSD, we for the first time showed the existence of two different mechanisms (one based on conventional turbulent shear and the other based on collapsing cavities) of droplet breakage in HC devices. The order of magnitude of turbulence energy dissipation rates generated due to collapsing cavity estimated using Hinze scale analysis showed good agreement with the values reported from cavity dynamics models. The presented experimental results and analysis will be useful for researchers and engineers interested in developing computational models and compact devices for producing emulsions of the desired DSD.

Evaluation of spray characteristics of aviation biofuels and Jet A-1 from a hybrid airblast atomizer

Studies on the atomization characteristics of sustainable aviation fuels (SAF) such as drop-in aviation biofuels from aircraft engine atomizers are essential to counter the rise in aviation-caused CO2 emissions in the atmosphere. The present study analyses the drop size characteristics of fuel sprays of camelina- and jatropha-derived drop-in aviation biofuels from a hybrid airblast atomizer (HAA) used in aircraft engines. To begin with salient details of hybrid atomization are studied through experiments using water at different liquid and air flow rates. The spray characterization work of four different drop-in aviation biofuels, derived through the blending of camelina/jatropha HRJ biofuels and Jet A-1, from the HAA is done subsequently. The fuel spray experiments are carried out at six test conditions. The mean drop size (Sauter mean diameter, SMD) variations of the HAA spray are compared with predictions obtained from correlations reported in the literature. Likewise, the SMD trends of the hybrid atomization are compared with that of the simplex swirl atomization. Using the current data of the HAA spray of six experimental fluids, a new correlation for non-dimensionalized SMD in terms of liquid and air Weber numbers and Ohnesorge number is proposed, which facilitates the determination of mean droplet size of futuristic alternative aviation fuel sprays from the hybrid airblast atomizers.

Assessing Raindrop Breakup Parameterizations Using Disdrometer Observations

Abstract An intercomparison of raindrop mean diameter frequency distribution (RDFD) is performed for numerical simulations of precipitating cloud systems using an array of models and microphysics schemes. This includes results from the Regional Atmospheric Modeling System (RAMS) double-moment microphysics, the Hebrew University Cloud Model bin microphysics (HUCM) interfaced to the RAMS parent model, and the Weather Research and Forecasting (WRF) Model with the Thompson, Morrison, double-moment 6-class (WDM6), and National Severe Storms Laboratory (NSSL) double-moment schemes. Simulations are examined with respect to the raindrop size distribution (DSD) volume-number mean diameter (Dm) and intercept parameter (Nw). When compared to a suite of disdrometer observations, the RDFD resulting from each microphysics scheme exhibits varying degrees of mean drop size constraints and peaks in the frequency distribution of Dm. A more detailed investigation of the peaked RDFD from the RAMS simulations suggests that the parameterization of raindrop collisional breakup can impose strong limitations on the evolution of simulated drop growth. As such, a summary and comparison of the drop breakup parameterizations among the aforementioned microphysics schemes is presented. While some drop breakup parameterizations are adjusted toward the observations by modifying the threshold diameter for the onset of breakup, this study explores the use of a modified maximum breakup efficiency. This method permits the parameterization to retain its threshold breakup diameter, while limiting the strength of drop breakup and permitting a broader range of drop sizes. As a result, the simulated mean drop sizes are in better agreement with observations.

The characteristic length scales in direct mode of drop formation from the edges of spinning discs with different surface wetting characteristics

The characteristic length-scales responsible for primary and secondary drop size in direct droplet mode are probed using discs of different surface wettability through exposure controlled high resolution static imaging. The primary drop formation from the edge of a hydrophobic disc is found to be mechanistically different from its hydrophilic counterparts. The disc wetting factor (w) influences primary drop size only at low Weber number (We). A single mean primary/secondary drop size-We relationship represents discs of different surface characteristics. It points to insignificance of surface wettability. For hydrophilic discs the mean primary drop size and the mean incipient bulge size vary as We-0.47 and We-0.5 respectively, which hints at incipient bulge size dependence of primary drop size. The two capillary wave-based length scales tested as characteristic length scales for secondary drops show high size variability, which is a distinctive feature of secondary drops..

Hurricane Laura (2020): A Comparison of Drop Size Distribution Moments Using Ground and Radar Remote Sensing Retrieval Methods

AbstractHurricane Laura was the strongest hurricane to make landfall in Louisiana since 1969 with maximum sustained winds of 130 knots. One University of Oklahoma Shared Atmospheric Mobile and Teaching Polarmetric Radar (SR1‐P), and four portable in situ precipitation stations (PIPSs) equipped with parsivel disdrometers were spatially and temporally collocated with two NASA Global Precipitation Measurement Mission Dual‐frequency Precipitation Radar overpasses. The combined retrieval methods were able to quantify and compare drop size distribution moments and radar‐inferred precipitation processes before, during, and after the storm center made landfall. It was found that the magnitude of collision‐coalescence dominant precipitation decreased from before to after landfall. Further, the presence of a bright‐band becomes more evident across all percentiles in the post‐landfall overpass, indicating an increase in stratiform precipitation compared to convective precipitation after Laura moved inland. The PIPS showed an increase in mean drop size from 1.0 mm before landfall to as high as 4.0 mm in the eyewall, while decreasing to below 1.0 mm as Laura continued to move inland with a decrease in maximum echo top height of 0.5–1.0 km. Last, the Dual‐frequency Precipitation Radar (DPR) algorithm overestimated the normalized intercept parameter by 0.5–1.0 m−3 mm−1 compared to the PIPS implying differences in measured drop number concentration, potentially due to differences in measurement footprint or assumptions in the DPR retrieval algorithm. These findings can potentially be used to improve the DPR particle size distribution algorithm in tropical cyclones.

Effect of emulsification parameters on the rheology, texture, and physical stability of cosmetic emulsions: A multiscale approach

This study presents a multiscale approach for the production of cosmetic emulsions to evaluate the influence of emulsification on the macroscopic and microscopic properties of the product. This study evaluates the effects of the impeller pumping capacity and tip velocity on the rheological and textural properties of the cosmetic emulsions at the macroscopic scale as well as the effect of these parameters on the average drop size and the drop size distribution at the microscopic scale. This study also considers the influence of the pumping capacity and tip velocity on the physical stability of cosmetic emulsions. Two dispersed phase concentrations were used in this study (i.e., 30 % and 80 % w/w) to evaluate the effect of the product formulation on the performance of the cosmetic emulsions. The results showed that the impeller pumping capacity and the tip velocity are key parameters to control the energy demand and drop formation during the emulsification process (mean drop size and drop size distribution). These parameters also govern the microscopic structure of the emulsions, which has a strong influence on the macroscopic performance of the product. Thus, the tip velocity and pumping capacity are proposed as appropriate scale-up factors for the emulsification process.

Atomization model based on the ligament-mediated spray mechanism for coaxial two-fluid air-blast nozzle

The drop size distribution is one of the crucial parameters in liquid atomization. In this study, we develop a ligament-mediated gamma distribution (LMGD) model for coaxial two-fluid air-blast atomization based on cascade breakup and a ligament-mediated spray mechanism that can predict the nonlinear relationship between the drop diameters and drop size distribution at different velocities. The use of a single-parameter gamma distribution for the sizes of fragments produced by liquid ligament breakup is validated by experimental and theoretical results for liquid atomization. The proposed model outperforms the traditional model in enabling the simultaneous calculation of the mean drop size and distribution, as well as the accurate prediction of the nonlinearity of the distribution of drop sizes. The LMGD model has the advantage of being simple and efficient and more realistic than the traditional model.

Emulsion gels loaded with pancreatic lipase: Preparation from spontaneously made emulsions and assessment of the rheological, microscopic and cargo release properties

Emulsion gels are solidified emulsions, which can be used for delivery of both hydrophilic and lipophilic substances. In this research, at first fish oil-in-water (O/W; 10% w/w) emulsions were prepared through the spontaneous emulsification technique. As emulsifier, a blend of the small-molecule surfactant tween 80, and either low-acyl (LaG) or high-acyl (HaG) gellan was used. For making fully stable (100% stability index) emulsions, a 10-fold higher concentration of LaG than HaG in the emulsion aqueous phase was required. The difference in gellan concentration resulted in a bigger mean drop size, as well as lesser consistency coefficient and yield stress for HaG emulsion than LaG emulsion.Subsequently, the fully stable HaG and LaG emulsions were gelled by CaCl2 addition. LaG emulsion gel was self-supporting and had a dense microstructure (as observed by electron microscopy), whereas HaG emulsion gel was not self-supporting. Loading lipase into the emulsions before ionotropic gelation did not lead to unacceptable acid values for fish oil during the emulsion gels storage.When the lipase-loaded fish O/W emulsion gels were immersed in an acid solution which imitated the gastric fluid (yet without digestive enzymes) oil droplets flocculated (as observed by confocal microscopy). The acid immersion also increased the dynamic moduli of the gels. Lipase was not released into the surrounding acid solution from LaG emulsion gel. A subsequent immersion within an alkaline solution imitating the small intestine fluid (yet without digestive enzymes) reduced the dynamic moduli of both kinds of emulsion gels. The alkaline immersion also caused extensive crack propagation in LaG emulsion gel network, which was found associated with diminished value of tan δ (Gʹʹ/Gʹ) as an index of gel energy dissipation. Lipase was released form LaG emulsion gel into the alkaline solution, however, it took a remarkable period of time to begin.

Retrieval of Vertical Structure of Raindrop Size Distribution from Equatorial Atmosphere Radar and Boundary Layer Radar

This work develops an algorithm to retrieve the vertical structure of the raindrop size distribution (DSD) of rain from simultaneous observations of 47 MHz Equatorial Atmosphere Radar (EAR) and 1.3 GHz Boundary Layer Radar (BLR) at Koto Tabang, West Sumatra, Indonesia (0.20°S, 100.32°E, 865 m above sea level). EAR is sensitive to the detection of turbulence, and BLR is susceptible to identifying precipitation echo. The EAR Doppler spectrum broadening effects due to turbulence and finite radar beam width were reduced using the convolution process. The Gaussian function was used to model the turbulence Doppler spectrum. A non-linear least-squares fitting method was applied to retrieve DSD parameters. Subsequently, the equations to estimate DSD using this dual-frequency algorithm assume the gamma DSD model to retrieve the distribution from the Doppler spectrum of precipitation echo. The precipitation events on April 23, 2004 on the Coupling Processes in the Equatorial Atmosphere (CPEA-I) project have been analyzed. Results show that the precipitation spectrum obtained using the dual-frequency method is higher, more precise, and well-fitted than the single-frequency method, meaning the dual-frequency method has great potential to be used in observing the microphysical process and remote sensing application analysis of DSD in Indonesia, particularly at Koto Tabang. The analyses show various microphysical processes that occur in the rain, such as coalescence, evaporation, break-up, and condensation. Furthermore, for the purpose of easier remote sensing application analysis of profile DSD characteristics, we use a DSD ΔΖMP parameter. ΔΖMP is a rain rate insensitive DSD parameter representing mean drop size. The trend of ΔZMP is not totally uniform with regards to rain rate and reflectivity factors, with ΔZMP higher in the first half of the event and becoming lower toward the end. This suggests that we have to use different Z-R relations within the event. Doi: 10.28991/ESJ-2022-06-03-02 Full Text: PDF

Experimental investigation on drop size distribution and mean drop size in an L-shape pulsed packed extraction column

In this study, the mean drop diameter and drop size distribution have been investigated in a pilot plant of a new type of extraction column entitled “L-shaped pulsed packed extraction column” by using two liquid systems of toluene/acetone/water and n-butyl/acetone/water in the presence of mass transfer in two directions. The effects of operational variables, physical properties and mass transfer direction have been considered on the dispersed drop size. It is found that the mean drop diameter and drop size distribution is significantly affected by the pulsation intensity and interfacial tension of liquid system. However, the phases flow rates and mass transfer direction have a weaker impact. Furthermore, it is observed that the mean drops diameter in the horizontal and vertical sections of the used column have mostly the same size and it is considered as a significant advantage. Finally, new correlations are proposed to accurately predict the mean drop size and drop size distribution. Good agreement between predictions and experiments was found for all operating conditions, chemical systems and mass transfer direction that were investigated.

Drop breakage in a single‐pass through vortex‐based cavitation device: Experiments and modeling

AbstractLiquid–liquid emulsions are used in many sectors such as personal care, home care, and food products. There is an increasing need for developing compact and modular devices for producing emulsions with desired droplet size distribution (DSD). In this work, we have experimentally and computationally investigated an application of vortex‐based hydrodynamic cavitation (HC) device for producing emulsions. The focus is on understanding drop breakage occurring in a single‐pass through the considered HC device. The experiments were performed for generating oil‐in‐water emulsion containing 1%–20% rapeseed oil. The effect of pressure drop across the HC device in the range of 50–250 kPa on drop breakage was examined. DSD of emulsions produced through a single pass was measured using the focussed beam reflectance measurements. Comprehensive computational fluid dynamics (CFD) model based on the Eulerian approach was developed to simulate multiphase cavitating flow. Using the simulated flow, population balance model (PBM) with appropriate breakage kernels was solved to simulate droplet breakage in a vortex‐based HC device. The device showed an excellent drop breakage efficiency (nearly 1% which is much higher than other commercial devices such as rotor–stators or sonolators) and was able to reduce mean drop size from 66 to ~15 μm in a single pass. The CFD and PBM models were able to simulate DSD. The presented models and results will be useful for researchers and engineers interested in developing compact devices for producing emulsions of desired DSD.

Enhancing the Vanadium Extraction Performance Using Synergistic Mixtures of D2EHPA and TBP in RDC Column with the Perforated Structure; Case Study: Evaluation Probability Density Functions

The reactive extraction behavior on the mean drop size and distribution for synergistic extraction of vanadium from sulfate medium with di-(2-ethylhexyl) phosphoric acid (D2EHPA) and its mixture with tributyl phosphate (TBP) in kerosene has been interpreted in the modified rotating disc contactor column. In batch experiments, the maximum extraction efficiency was obtained in the single extraction system with 0.29 molar D2EHPA at an equilibrium pH of 2, whereas the extraction percentage was significantly increased by adding 0.3 molar TBP into the same D2EHPA concentration due to the synergistic effect. The solvent extraction process has been optimized by applying the central composition design approach in the column experiments. The influence of operational variables such as agitation rate and both phase flow rates as well as the type of used systems have been investigated on drop behavior. A unified model was provided for modified rotating disc columns. It was found from Monte Carlo simulation for uncertainty analysis that the agitation speed and type of utilized systems, namely reactive or physical systems have more profound impacts on the mean drop size. The optimum conditions were obtained at the agitation rate of 400 rpm, and phase flow rates equal to 26 L/h.

Statistics of Jet Drop Production

AbstractBubbles bursting at the ocean surface are an important source of sea‐spray aerosol. We describe jet drop production, from ensembles of high fidelity numerical simulations of bubble bursting, validated against experimental results. The number of jet drops, their size, and velocity are controlled by the ratio of the bubble size, Rb, and the visco‐capillary length, , where γ is the surface tension, ρw, μw the water density and viscosity. The mean drop size follows and the ejected number of drops , accounting for temperature variations. We confirm that submicrons jet drops are produced by bubbles in the 10–40 microns range. We compute the distribution of jet drops formed by a range of bubbles present under a breaking wave which compares well against laboratory experiments. We discuss the applicability of the proposed formulation in the context of sea spray generation function.

Experimental investigation of spray characteristics of gliding arc plasma airblast fuel injector

High atomization quality plays a vital role in combustion performance enhancement for aero-engines and ramjets. Low enthalpy and low pressure at low flight Mach number result in poor atomization quality of airblast fuel injector. Underlying mechanism of how plasma assisted combustion on spray characteristics still remains unclear. In present study, a novel gliding arc plasma airblast fuel injector is proposed for atomization quality improvement of airblast fuel injector in order to achieve high combustion efficiency, low pollutant emission, and to prolong life of injectors. Spray and atomization characteristics of aviation kerosene (RP-3) under different working conditions which includes gliding arc plasma excitation, air flow velocity and air/fuel ratio were investigated. A string-like gliding arc discharge plasma column was generated between the two electrodes mounted at the exit port plane of plasma airblast fuel injector. Macroscopic and microscopic spray characteristics were studied by simultaneous LIF/MIE technique and particle/droplet image analysis (PDIA) system. Results reveal that mean droplet size were decreased with increase of air flow velocity and air/fuel ratio. Influenced by the thermal and transport effect of gliding arc plasma excitation, more homogeneous fuel spray with smaller mean drop size and greater spray cone angle was witnessed. Sauter mean diameter was decreased by around 50% at 17 m/s, while droplet uniformity index and spray cone angle were increased by up to 24.6% and 35%, respectively. The gliding arc plasma mainly take effect on reducing mean droplet size of kerosene in the near-field spray (<20 mm) which is very near from the ignitor to improve high initial evaporation rates for rapid ignition and combustion efficiency improvement.

Evaluation of mean diameter and drop size distribution of an emulsion liquid membrane system in a horizontal mixer-settler

A W/O emulsion consisting of distillated water, kerosene and Span 80 was prepared to be employed in a horizontal mixer settler. The effect of stirring speed, flow ratio, total flow, Span 80 concentration and the internal to membrane phase volume ratio on the Sauter mean diameter (D32) of emulsion, drop size distribution and also the holdup were investigated without mass transfer effect. The results revealed that, with increasing the stirring speed, the D32 decreased and the emulsion holdup increased. However, the emulsion globules breakage incremented due to producing high shear forces. For the ELM system with the surfactant concentration higher than 3wt.%, the D32 increased due to the emulsion swelling and the holdup reduced. In addition, raising the flow ratio and the total flow increased the drop size which led to the reduction in the holdup. Besides, for the internal to membrane phase volume ratio higher than 0.4, the drop size increased. Empirical correlation was presented to predict the D32 with average absolute relative errors (AAREs) of 3.9%. The drop size distribution was conformed to normal distribution, and α and β parameters have been correlated with AAREs of 3.4% and 3.7%, respectively.