scholarly journals Planar LIF/MIE ratio droplet sizing using structured laser sheet imaging at elevated ambient pressures

2020 ◽  
Vol 4 ◽  
pp. 38-47
Author(s):  
Andrew Corber ◽  
Wajid Chishty ◽  
Patrizio Vena
Keyword(s):  
Scattered Light ◽  
Laser Sheet ◽  
Jet Fuels ◽  
Sauter Mean Diameter ◽  
Hollow Cone ◽  
Phase Doppler Anemometry ◽  
Mean Diameter ◽  
Planar Maps ◽  
Liquid Flows ◽  
Conventional Laser

LIF/Mie ratio-metric imaging was used to characterize sprays produced by a simple hollow-cone pressure atomizer, operating under elevated ambient pressures up to 10 atm. A structured laser sheet was used as the source of illumination to suppress the multiple scattered light, generating images that are free of the artefacts typically found in conventional laser sheet images. The resulting LIF/Mie ratio-metric images were calibrated using Phase Doppler anemometry to generate axial planar maps of the spray’s Sauter-mean diameter (SMD). This calibration methodology was applied over a range of ambient pressures and liquid flows to assess the robustness of the structured LIF/Mie ratio-metric imaging as a droplet sizing technique. The test fluids consisted of conventional and alternative jet fuels as well as nozzle calibration fluid. Results presented in the paper indicate both the effectiveness and certain limitations of the technique.

Experimental Evaluation of the Nukiyama-Tanasawa Equation for Pneumatically Generated Aerosols Used in Flame Atomic Spectrometry

1992 ◽  
Vol 46 (4) ◽  
pp. 669-676 ◽  
Author(s):  
Coral Robles ◽  
Juan Mora ◽  
Antonio Canals
Keyword(s):  
Organic Solvents ◽  
Liquid Flow ◽  
Experimental Evaluation ◽  
Gas Flow ◽  
Droplet Size Distribution ◽  
Atomic Spectrometry ◽  
Fraunhofer Diffraction ◽  
Sauter Mean Diameter ◽  
Mean Diameter ◽  
Liquid Flows

The Nukiyama-Tanasawa equation has been checked for its applicability to predict the Sauter mean diameter of aerosols generated pneumatically under the conditions usually employed in FAAS. The measurements of droplet-size distribution have been carried out by means of a laser Fraunhofer diffraction system. The effects of both gas and liquid flows, and solvent physical properties, on experimental and calculated Sauter mean diameters of the aerosols have been studied. The results show that this equation, under normal conditions used in FAAS, correctly describes the trends of Sauter mean diameter variation of aerosols generated pneumatically with respect to the flows of nebulizing gas and liquid. Increases in liquid flow or decreases in gas flow give rise to increases in Sauter mean diameters of the aerosols. However, the absolute values predicted according to the equation far exceed the experimental Sauter mean diameters obtained, the divergences being larger at higher liquid flow/nebulizing gas flow ratios. The overestimation for water ranged from 1.8- to 8.1-fold, and for organic solvents and methanol+water mixtures from 3.6- to 13.3-fold. Under the conditions studied, experimental Sauter mean diameter values for the organic solvents and methanol+water mixtures studied were well below those found for water, under comparable conditions. This result contradicts the predictions of the Nukiyama-Tanasawa equation mainly at high liquid flow/nebulizing gas flow ratios. The main reason for this divergence is the overweighting assigned to the second term of the equation.

scholarly journals Measurements in swirling spray flames at blow-off

2018 ◽  
Vol 10 (3) ◽  
pp. 185-210 ◽  
Author(s):  
Ruoyang Yuan ◽  
James Kariuki ◽  
Epaminondas Mastorakos
Keyword(s):  
Heat Release ◽  
Recirculation Zone ◽  
Laser Induced Fluorescence ◽  
Sauter Mean Diameter ◽  
Phase Doppler Anemometry ◽  
Planar Laser Induced Fluorescence ◽  
Spray Flames ◽  
Mean Diameter ◽  
Planar Laser ◽  
Lift Off

Various characteristics of swirling spray flames of ethanol, n-heptane, n-decane, and n-dodecane have been measured at conditions far from and close to blow-off using phase Doppler anemometry and OH* chemiluminescence, OH-planar laser-induced fluorescence, and Mie scattering at 5 kHz. The blow-off transient has also been examined. The OH* showed that the two main heat release regions lie around the spray jet at the inner recirculation zone and along the outer shear layer between the inner recirculation zone and the annular air jet. The heat release region is shortened and more attached as the flame approached blow-off. Mie images and phase Doppler anemometry data showed a wider dispersion of the ethanol spray compared to the other fuels. Similar spatial distributions of the Sauter mean diameter were observed for the four fuels for identical flow conditions, with the Sauter mean diameter value increasing with decreasing fuel volatility, but with the exception of significant presence of droplets in the nominally hollow cone for the ethanol spray. The OH-planar laser-induced fluorescence measurements showed an intermittent lift-off from the corner of the bluff body and the average lift-off height decreased with increasing air velocity, with less extinction along the inner flame branch especially for the heavier fuels. At the blow-off conditions, local extinctions appeared at both flame branches. The blow-off process followed a gradual reduction of the size of the flame, with the less volatile fuels showing a more severe flame area reduction compared to the condition far from blow-off. The average blow-off duration, [Formula: see text], calculated from the evolution of the area-integrated OH* signal, was a few tens of milliseconds and for all conditions investigated the ratio [Formula: see text] /( D/ UB) was around 11, but with large scatter. The measurements provide useful information for validation of combustion models focusing on local and global extinction.

scholarly journals EXPERIMENTAL STUDY OF MEAN DROPLET SIZE FROM PRESSURE SWIRL ATOMIZER

2020 ◽  
Vol 4 (6) ◽  
pp. 49-59
Author(s):  
Sherry Amedorme
Keyword(s):  
Experimental Study ◽  
Liquid Film ◽  
Drop Size ◽  
Injection Pressure ◽  
Size Distributions ◽  
Sauter Mean Diameter ◽  
Hollow Cone ◽  
Mean Diameter ◽  
Drop Size Distributions ◽  
Exit Orifice

This experimental study undertakes the measurements of droplet Sauter Mean Diameter (SMD) at different axial distances for the hollow-cone nozzle and different radial distances from the spray centreline using a laser-diffraction-based drop size analyser in order to validate atomization model. The study also investigates the influence of injection pressure and the evaluation of two exit orifice diameters on the Sauter Mean Diameter (SMD). The drop size distributions along the nozzle centreline as well as the radial drop distributions from spray centreline are also evaluated. To enhance the physics of liquid sheet instability and liquid film breakup mechanisms, visualization of liquid film breakup as a function of injection pressure was carried out. The results show that mean droplet size (SMD) increases in the axial distance on the spray centreline but decreases with an increasing injection pressure on the spray centreline. It was observed that larger sized drops occupy the spray periphery compared to those occupying the spray core. For the nozzle exit orifice diameters of 3.5 mm and 1.5 mm, the results show that the small nozzle exhibits smaller SMDs than the bigger nozzle and the break-up lengths are different for the two nozzles. The drop size distributions at radial positions showed an increase in droplet formation through the spray downstream distances and become more uniform. The visualisation of the spray was carried out using high-speed camera and it was noted that a well-defined hollow-cone spray was captured and that the spray angle increases with the injection pressure but reduces with the liquid film length.

Sauter Mean Diameter Profiles of Droplets in a Continuous Spray Stream

2014 ◽  
Vol 695 ◽  
pp. 473-476
Author(s):  
Muhammad Yasin Naz ◽  
Shaharin Anwar Sulaiman ◽  
Bambang Ari-Wahjoedi
Keyword(s):  
Nozzle Exit ◽  
Ambient Air ◽  
Modified Starch ◽  
Sauter Mean Diameter ◽  
Starch Solution ◽  
Load Pressure ◽  
Phase Doppler Anemometry ◽  
Mean Diameter ◽  
Intrusive Phase

In this study, a modified starch solution was heated upto 80°C and continuously sprayed into ambient air with an axi-symmetric full cone nozzle operated at two different load pressures 3 and 5 bar. The generated sprays were characterized for axial Sauter Mean Diameter (SMD) by using a non-intrusive Phase Doppler Anemometry (PDA) technique. A monotonic decrease in SMD downstream to the nozzle exit was noticed at 5 bar load pressure. At 3 bar load pressure, initially, SMD decreased between 10-20 mm downstream, then increased between 20-40 mm and finally reached to its lowest values at 100 mm downstream. Overall, the SMD measured at 3 and 5 bar load pressures was decreased from 99 to 66 μm and 85 to 57 μm respectively after moving 100 mm downstream.

scholarly journals Atomization Quality of Twin Fluid Atomizers for Gas Turbines

1982 ◽  
Author(s):  
M. M. Elkotb ◽  
M. A. Elsayed Mahdy ◽  
M. E. Montaser
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Gas Turbines ◽  
Cone Angle ◽  
Droplet Size Distribution ◽  
Diameter Ratio ◽  
Air Pressure ◽  
Sauter Mean Diameter ◽  
Flow Number ◽  
Mean Diameter

A detailed investigation of the effect of nozzle/needle diameter ratio, normal fuel area, swirler degree, air pressure, fuel pressure on flow number, cone angle and droplet size distribution of external mixing twin fluid atomizers is given in this paper. Forty atomizers have been constructed to prevent mutual effect of various parameters. Flow number and cone angle are found to increase with nozzle/diameter ratio, and to decrease with the increase of air pressure. Optimum fuel flow is obtained at swirler angle 30-deg, while cone angle increases with increase of swirler angle. Sauter mean diameter decreases with the increase of air pressure and decrease of fuel pressure. Suitable functions are derived for droplet size distribution, Sauter mean diameter, and flow number. They are suitable to predict the geometry of the atomizer and to be used also in a prediction model for the calculation of fuel concentration and heat release.

scholarly journals Prediction of Mean Diameter and Velocity of Droplets in Air-Assisted Hollow-Cone Injection.

1996 ◽  
Vol 62 (593) ◽  
pp. 319-324 ◽  
Author(s):  
Takeshi MIYAMOTO ◽  
Takashi KOBAYASHI ◽  
Yoichiro MATSUMOTO
Keyword(s):  
Hollow Cone ◽  
Mean Diameter

Bubble Entrapment in Sprayed Films

2014 ◽  
Author(s):  
A. Dalili ◽  
S. Chandra ◽  
J. Mostaghimi ◽  
H. T. Charles Fan ◽  
J. C. Simmer
Keyword(s):  
Surface Tension ◽  
Film Thickness ◽  
The Other ◽  
Bubble Motion ◽  
Sauter Mean Diameter ◽  
Glass Substrates ◽  
Buoyancy Forces ◽  
Mean Diameter ◽  
Imagej Software ◽  
Bubble Movement

A compressed air sprayer was used to spray model paint onto two glass substrates at the same time. Afterwards, one glass substrate was placed on a LED light source and still photographs were taken from the top using a DSLR camera with a timer system. The other substrate was put on a balance to record weight. Pictures and weight measurements were taken at 5 second intervals for 15 minutes. The sprayed film thickness was varied. The pictures were analyzed using ImageJ software. Bubble Count vs. Time, Sauter Mean Diameter (SMD) of Bubbles vs. Time as well as Weight vs. Time was plotted. It was seen that the pace of weight loss was faster for thinner films. The rate of bubble escape also depended on film thickness. It took a longer time for thicker films to lose the bubbles entrapped in them. In the first 30 seconds, large bubbles escaped due to buoyancy forces and afterwards surface-tension driven flows became dominant. There was also a lot of bubble movement in thicker films. The effect of gravity was studied as well. Gravity did not affect the bubble escape rate since a downward facing film had the same bubble count as an upward facing film confirming that bubble motion was not due to buoyancy forces alone. However, the SMD of bubbles in a downward facing film was larger than an upward facing film. Buoyancy is not a factor in bubble escape from the downward facing film and only surface-tension driven flows play a role.

Drop Size Measurements in Evaporating Realistic Sprays of Emulsified and Neat Fuels

1983 ◽  
Author(s):  
Lee G. Dodge ◽  
Clifford A. Moses
Keyword(s):  
Drop Size ◽  
Elevated Temperatures ◽  
Jet Fuel ◽  
Sauter Mean Diameter ◽  
Emulsified Fuel ◽  
Fuel Jet ◽  
Mean Diameter ◽  
Detailed Computer ◽  
Particle Sizer ◽  
Additional Point

A comparative study has been performed of the drop-size distribution of sprays of emulsified and neat distillate-type aviation fuels at elevated temperatures (308K to 700K) and pressures (101 kPa to 586 kPa). All drop-size data were obtained with a Malvern Model 2200 Particle Sizer based on the forward angle diffraction pattern produced by the drops when illuminated by a collimated HeNe laser beam. Fuels included a standard multicomponent jet fuel, Jet-A, and a single component fuel, hexadecane, in both neat form and emulsified with 20 percent (by vol.) water and 2 percent (by vol.) surfactant. The initial breakup and atomization of a neat and emulsified fuel were quite similar at all conditions, and the evaporation rates appeared similar at various temperatures for pressures at or below about 300 kPa. At higher pressures with elevated temperatures the emulsified fuels of both types produce drops of significantly smaller Sauter mean diameter than the neat fuels as distance from the nozzle increases. These results are consistent with the microexplosion hypothesis, but there could also be alternative explanations. A detailed computer model which predicts heat up rates, steady state drop temperatures, evaporation rates, and drop trajectories has been used to help interpret the results. An additional point which has been observed is that the initial Sauter mean diameter produced with constant differential nozzle pressure is dependent on the air pressure with an exponent of about −0.4, i.e., SMD ∼ Pair−0.4. Some recent correlations often quoted omit the pressure (density) of air term.

A new model of bubble Sauter mean diameter in fine bubble-dominated columns

2020 ◽  
Vol 393 ◽  
pp. 124673
Author(s):  
Baorong Wang ◽  
Guoqiang Yang ◽  
Hongzhou Tian ◽  
Xiabing Li ◽  
Gaodong Yang ◽  
...  
Keyword(s):  
Sauter Mean Diameter ◽  
New Model ◽  
Fine Bubble ◽  
Mean Diameter
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