Microemulsions: theoretical estimates of droplet sizes and size distributions

2007 ◽  
pp. 1-9 ◽  
Author(s):  
J. Th. G. Overbeek
Keyword(s):  
Size Distributions ◽  
Droplet Sizes

scholarly journals Theoretical investigation of mixing in warm clouds – Part 2: Homogeneous mixing

2016 ◽  
Vol 16 (14) ◽  
pp. 9255-9272 ◽  
Author(s):  
Mark Pinsky ◽  
Alexander Khain ◽  
Alexei Korolev ◽  
Leehi Magaritz-Ronen
Keyword(s):  
Liquid Water ◽  
Liquid Water Content ◽  
Time Dependent ◽  
Size Distributions ◽  
Conceptual Scheme ◽  
Dimensional Parameter ◽  
Droplet Concentration ◽  
Droplet Sizes ◽  
Droplet Size Distributions ◽  
Analytical Expressions

Abstract. Evolution of monodisperse and polydisperse droplet size distributions (DSD) during homogeneous mixing is analyzed. Time-dependent universal analytical expressions for supersaturation and liquid water content are derived. For an initial monodisperse DSD, these quantities are shown to depend on a sole non-dimensional parameter. The evolution of moments and moment-related functions in the course of homogeneous evaporation of polydisperse DSD is analyzed using a parcel model.It is shown that the classic conceptual scheme, according to which homogeneous mixing leads to a decrease in droplet mass at constant droplet concentration, is valid only in cases of monodisperse or initially very narrow polydisperse DSD. In cases of wide polydisperse DSD, mixing and successive evaporation lead to a decrease of both mass and concentration, so the characteristic droplet sizes remain nearly constant. As this feature is typically associated with inhomogeneous mixing, we conclude that in cases of an initially wide DSD at cloud top, homogeneous mixing is nearly indistinguishable from inhomogeneous mixing.

Sensitivity Analysis on the Effect of D32 and Dv90 on the Evaporation Efficiency of Gas Turbine Inlet Fogging for Power Augmentation

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Mustapha Chaker
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Ambient Air ◽  
Turbine Engines ◽  
Water Volume ◽  
Size Distributions ◽  
Gas Turbine Engines ◽  
Droplet Sizes ◽  
Droplet Size Distributions ◽  
Turbine Output

Gas turbine output is strongly dependent on the ambient air temperature. This decrease usually occurs in the hot afternoon during the peak demand for power. One way to counter this drop in output is to cool the inlet air using one of the available cooling technologies such as the inlet fog cooling of gas turbine engines for power augmentation. This technology is well established with over 1000 fogging systems installed all around the world on gas turbines of various makes and sizes ranging from 5 MW to 250 MW. Two types of statistical droplet diameters are used to characterize the droplet sizes from nozzles used in the fogging systems, namely D32 (Sauter mean diameter) (SMD) and Dv90 (diameter for which 90% of the water volume in the spray is less than or equal to). This paper will show the importance of each diameter on the performance of fogging systems. For this purpose, a heat and mass transfer theoretical model is developed to analyze the dynamics of evaporation of fog droplets. The model will quantify the evaporative efficiency of fog droplets for different D32 and Dv90 values derived from experimentally measured droplet size distributions at two typical ambient psychrometric conditions: hot and dry, and cold and humid.

Sensitivity Analysis on the Effect of D32 and Dv90 on the Evaporation Efficiency of Gas Turbine Inlet Fogging for Power Augmentation

2017 ◽  
Author(s):  
Mustapha Chaker
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Ambient Air ◽  
Turbine Engines ◽  
Water Volume ◽  
Size Distributions ◽  
Gas Turbine Engines ◽  
Droplet Sizes ◽  
Droplet Size Distributions ◽  
Turbine Output

Gas Turbine output is strongly dependent of the ambient air temperature. This decrease is usually occurs in the hot afternoon during the peak demand for power. One way to counter this drop in output is to cool the inlet air using one of the available cooling technologies such as the inlet fog cooling of gas turbine engines for power augmentation. This technology is well-established with over 1,000 fogging systems installed all around the world on gas turbines of various makes and sizes ranging from 5MW to 250MW. Two droplet diameters are used to characterize the droplet sizes from nozzles used in the fogging systems, namely D32 (Sauter mean diameter) and Dv90 (diameter for which 90% of the water volume in the spray is less than or equal to). This paper will show the importance of each diameter on the performance of fogging systems. For this purpose, a heat and mass transfer theoretical model is developed to analyze the dynamics of evaporation of fog droplets. The model will quantify the evaporative efficiency of fog droplets for different D32 and Dv90 values derived from experimentally measured droplet size distributions at two typical ambient psychrometric conditions: hot and dry, and cold and Humid.

Droplet Size Spectrum, Activation Pressure, and Flow Rate Discharged from PWM Flat-Fan Nozzles

2021 ◽  
Vol 64 (1) ◽  
pp. 313-325
Author(s):  
Zhiming Wei ◽  
Heping Zhu ◽  
Zhihong Zhang ◽  
Ramón Salcedo ◽  
Degang Duan
Keyword(s):  
Droplet Size ◽  
Duty Cycle ◽  
Solenoid Valve ◽  
Variable Rate ◽  
Size Distributions ◽  
Flow Rates ◽  
Nozzle Orifice ◽  
Duty Cycles ◽  
Droplet Sizes ◽  
Droplet Size Distributions

HighlightsDroplet sizes, activation pressures acting on nozzle orifices, and flow rates were investigated.Droplet sizes varied with duty cycles, nozzle orifice sizes, and PWM solenoid valve manufacturers.Activation pressures decreased as duty cycles decreased and increased as nozzle orifice sizes decreased.Flow rates increased with increases in both duty cycles and nozzle orifice sizes.Abstract. Pulse width modulated (PWM) spray systems can produce variable spray rates for precision applications of pesticide and fertilizer; however, there are also concerns over their spray performance stability. Droplet size distributions, activation pressures acting on nozzle orifices, and flow rates discharged from nozzles were investigated for test combinations of ten PWM duty cycles (10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%), six flat-fan nozzles with different orifice sizes (XR8001, XR8002, XR8003, XR8004, XR8005, and XR8006), and two PWM solenoid valves from two different manufacturers. Test results showed that the droplet size distribution, activation pressure, and flow rate varied with the duty cycle, nozzle orifice size, and PWM solenoid valve source. For XR8001 and XR8002 nozzles, droplet sizes did not vary significantly with all duty cycles from 10% to 100%. To obtain relatively consistent droplet size distributions, XR8003 and XR8004 nozzles required PWM duty cycles of at least 20%, while XR8005 and XR8006 nozzles required duty cycles of 30% or greater. The activation pressure directly on nozzle orifices increased as the duty cycle increased but decreased as the nozzle orifice size increased. In addition, the same nozzles coupled with PWM solenoid valves from two different manufacturers discharged different flow rates for the same duty cycle in the range of 10% to 90%. Therefore, careful selection of PWM solenoid valves for different orifice nozzles operated at different duty cycles was necessary to achieve consistent variable-rate spray performances. Keywords: Droplet diameter, Variable rate, PWM solenoid valve, Pesticide, Fertilizer, Precision farming.

Spray Characteristics of Rotary Micro Sprinkler Nozzles Used in Orchard Pesticide Delivery

2020 ◽  
Vol 63 (6) ◽  
pp. 1845-1853
Author(s):  
Huseyin Guler ◽  
Zhihong Zhang ◽  
Heping Zhu ◽  
Matthew Grieshop ◽  
Mark A. Ledebuhr
Keyword(s):  
Droplet Size ◽  
Delivery Systems ◽  
Orifice Diameter ◽  
List Type ◽  
Spray Drift ◽  
Operating Pressure ◽  
Size Distributions ◽  
Multiple Variable ◽  
Droplet Sizes ◽  
Droplet Size Distributions

HighlightsDroplet sizes were determined for rotary micro sprinkler nozzles used in solid set canopy delivery systems.An empirical multiple-variable model was developed to predict volume median diameters in spray patterns.Sprinkler nozzles produced medium to coarse droplets to minimize pesticide drift in orchards and trellised systems.Droplet size information can be used to select optimal nozzles for either irrigation or pesticide delivery systems.Abstract. Rotary micro sprinkler nozzles can be used for both irrigation and pesticide applications in orchard systems, but little to no information is available on their droplet size distributions. In this study, the droplet size distributions were investigated and described for rotary micro sprinkler nozzles with five different orifice diameters. A particle/droplet laser image analysis system was used to measure droplet spectra at two pressures (207 and 310 kPa) and two radial distances (0.25 and 0.85 m) from the sprinkler nozzle center. Nozzle orifice sizes, rotational speeds, and flow rates were also measured. Droplet sizes varied with the orifice size, operating pressure, and sampling location. Spiral-shaped spray patterns formed due to the spinning discharge port, within which droplet densities varied with location, orifice diameter, and operating pressure. The volume medium diameters (Dv0.5) for green-black, orange-blue, black-black, blue-black, and red-gray nozzles were respectively 317, 338, 379, 352, and 218 µm at 207 kPa and 283, 250, 283, 270, and 222 µm at 310 kPa. An empirical multiple-variable regression model was developed to predict Dv0.5 in the spray patterns discharged from the nozzles. Test results demonstrated that the rotary micro sprinkler nozzles produced medium to coarse droplets that could be used to minimize spray drift while maintaining efficacy in orchard pesticide applications. Keywords: Chemical application, Droplet size, Irrigation, Rotary nozzle, Spray drift reduction.

scholarly journals Theoretical investigation of mixing in warm clouds – Part 2: Homogeneous mixing

2015 ◽  
Vol 15 (21) ◽  
pp. 30269-30320 ◽  
Author(s):  
M. Pinsky ◽  
A. Khain ◽  
A. Korolev ◽  
L. Magaritz-Ronen
Keyword(s):  
Liquid Water ◽  
Liquid Water Content ◽  
Time Dependent ◽  
Size Distributions ◽  
Conceptual Scheme ◽  
Dimensional Parameter ◽  
Droplet Concentration ◽  
Droplet Sizes ◽  
Analytical Relations ◽  
Droplet Size Distributions

Abstract. The evolution of monodisperse and polydisperse droplet size distributions (DSDs) during homogeneous mixing is analyzed. Time-dependent universal analytical relations of supersaturation and liquid water content, which depend on a sole non-dimensional parameter, are obtained for a monodisperse DSD. The evolution of moments and moment-relation functions in the course of the homogeneous evaporation of polydisperse DSDs is analyzed using a parcel model. It is shown that the classic conceptual scheme, according to which homogeneous mixing leads to a decrease in the droplet mass under constant droplet concentration, is valid only in cases of monodisperse or initially very narrow polydisperse DSDs. In cases of wide polydisperse DSDs, mixing and successive evaporation lead to a decrease of both mass and concentration such that the characteristic droplet sizes remain nearly constant. As this feature is typically associated with inhomogeneous mixing, we conclude that in cases of an initially wide DSD at cloud top, homogeneous mixing is nearly indistinguishable from inhomogeneous mixing.

Effects of Wake Chopping on Droplet Sizes in Steam Turbines

2005 ◽  
Vol 219 (12) ◽  
pp. 1357-1367 ◽  
Author(s):  
F Bakhtar ◽  
A V Heaton
Keyword(s):  
Size Distribution ◽  
Homogeneous Nucleation ◽  
Review Article ◽  
Size Distributions ◽  
Steam Turbines ◽  
Water Droplets ◽  
Droplet Sizes

This paper is a review article and considers the influence of wake chopping on the size distribution of water droplets formed by homogeneous nucleation in steam turbines. The studies by several investigators are summarized. All the studies show that the fluctuations caused by the wakes can broaden the size distributions of the nucleated droplets substantially and account for the polydisperse nature of the droplet distributions and coarse water observed in turbines. The effect of the presence of impurities in steam on its nucleation behaviour is also discussed.

Unsteady sheet fragmentation: droplet sizes and speeds

2018 ◽  
Vol 848 ◽  
pp. 946-967 ◽  
Author(s):  
Y. Wang ◽  
L. Bourouiba
Keyword(s):  
Drop Size ◽  
Size Distributions ◽  
Single Drop ◽  
Population Mean ◽  
Droplet Sizes ◽  
Precision Tracking ◽  
Drop Size Distributions ◽  
Detachment Time ◽  
Ligament Size ◽  
Comparable Size

Understanding what shapes the drop size distributions produced from fluid fragmentation is important for a range of industrial, natural and health processes. Gilet & Bourouiba (J. R. Soc. Interface, vol. 12, 2015, 20141092) showed that both the size and speed of fragmented droplets are critical to transmission of pathogens in the agricultural context. In this paper, we study both the size and speed distributions of droplets ejected during a canonical unsteady sheet fragmentation from drop impact on a target of comparable size to that of the drop. Upon impact, the drop transforms into a sheet which expands in the air bounded by a rim on which ligaments grow, continuously shedding droplets. We developed high-precision tracking algorithms that capture all ejected droplets, measuring their size and speed, as well as the detachment time from, and link to, their ligament of origin. Both size and speed distributions of all ejected droplets are skewed. We show that the polydispersity and skewness of the distributions are inherently due to the unsteadiness of the sheet expansion. We show that each ligament sheds a single drop at a time throughout the entire sheet expansion by a mechanism of end-pinching. The droplet-to-ligament size ratio $R\approx 1.5$ remains constant throughout the unsteady fragmentation, and is robust to change in impact Weber number. We also show that the population mean speed of the fragmented droplets at a given time is equal to the population mean speed of ligaments one necking time prior to detachment time.

Subsea Release of Oil & Gas – A Downscaled Laboratory Study Focused on Initial Droplet Formation and the Effect of Dispersant Injection

2014 ◽  
Vol 2014 (1) ◽  
pp. 283-298
Author(s):  
Per Johan Brandvik ◽  
Øistein Johansen ◽  
Umer Farooq
Keyword(s):  
Droplet Size ◽  
Sea Water ◽  
Droplet Formation ◽  
Size Distributions ◽  
Oil Droplets ◽  
Substantial Impact ◽  
Dispersed Oil ◽  
Laboratory Facility ◽  
Injection Techniques ◽  
Droplet Sizes

ABSTRACT This article describes the SINTEF Tower Basin (located in Trondheim, Norway) and its use for examining droplet formation and the effectiveness of dispersant injection. The Tower Basin is 6 m high and 3 m in diameter, containing 42 m3 of natural sea water. Oil is injected from the base of the basin and oil droplets are monitored by laser diffraction and in-situ camera techniques. Size distributions of oil droplets formed in deep water oil & gas blowouts have a substantial impact on the fate of the oil in the environment. However, very limited data on droplet size distributions from subsurface releases exist. The objective of this study has been to establish a laboratory facility to examine droplet size versus release conditions (flow rates and nozzle diameters), oil properties and injection of dispersants (injection techniques and dispersant types). Changes in the size of oil droplets that result from injection of dispersant are used to assess the effectiveness of the dispersant application (dosage and injection method). This comprehensive dataset is used to develop and calibrate existing algorithms to predict droplet sizes from subsurface releases, and the effect of dispersant treatment. The improved algorithms are implemented in current operational models where they are used to describe subsurface use of dispersant and fate of the dispersed oil in the water column.

scholarly journals Spatial Positioning and Operating Parameters of a Rotary Bell Sprayer: 3D Mapping of Droplet Size Distributions

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 165 ◽  
Author(s):  
Adnan Darwish Ahmad ◽  
Binit B. Singh ◽  
Mark Doerre ◽  
Ahmad M. Abubaker ◽  
Masoud Arabghahestani ◽  
...  
Keyword(s):  
Droplet Size ◽  
Flow Rate ◽  
Rotational Speed ◽  
Operating Parameters ◽  
Size Distributions ◽  
Theoretical Formulation ◽  
Wide Range ◽  
Droplet Sizes ◽  
Spatial Positioning ◽  
The Impact

In this study, we evaluated the fundamental physical behavior during droplet formation and flow from a rotary bell spray in the absence of an electrostatic field. The impact of a wide range of operating parameters of the rotary bell sprayer, such as flow rates, rotational speeds, and spatial positioning, on droplet sizes and size distributions using a three-dimensional (3-D) mapping was studied. The results showed that increasing the rotational speed caused the Sauter mean diameter of the droplets to decrease while increasing flow rate increased the droplet sizes. The rotational speed effect, however, was dominant compared to the effect of flow rate. An increase in droplet size radially away from the cup was noted in the vicinity of the cup, nevertheless, as the lateral distances from the cup and rotational speed were increased, the droplet sizes within the flow field became more uniform. This result is of importance for painting industries, which are looking for optimal target distances for uniform painting appearance. Furthermore, the theoretical formulation was validated with experimental data, which provides a wider range of applicability in terms of environment and parameters that could be tested. This work also provides an abundance of measurements, which can serve as a database for the validation of future droplet disintegration simulations.

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