Some Effects of Using Water as a Test Fluid in Fuel Nozzle Spray Analysis

1981 ◽  
Vol 103 (1) ◽  
pp. 118-123 ◽  
Author(s):  
H. C. Simmons ◽  
C. F. Harding
Keyword(s):  
Weber Number ◽  
Systematic Investigation ◽  
Test Fluid ◽  
Sauter Mean Diameter ◽  
Liquid Pressure ◽  
Flow Capacity ◽  
Mean Diameter ◽  
Small Flow ◽  
Fuel Nozzle ◽  
Discharge Orifice

A systematic investigation was made of the differences in atomizing performance between water and kerosene fuel for six simplex fuel nozzles of small flow capacity. A large number of tests was run using two methods of spray analysis, to determine the effect of nozzle liquid pressure drop (ΔPF) on Sauter Mean Diameter (SMD). It was found that there is a clearly-defined relationship dependent on both the relative values of surface tension and also on a Weber Number calculated for conditions in the liquid film at the nozzle discharge orifice. It is concluded that large errors in estimating SMD for modeling programs are possible if results observed with water are assumed to be representative of behavior with kerosene fuel.

High Weber Number SMD Correlations for Pressure Atomizers

1986 ◽  
Vol 108 (1) ◽  
pp. 191-195 ◽  
Author(s):  
J. B. Kennedy
Keyword(s):  
Pressure Drop ◽  
Weber Number ◽  
Fuel Temperature ◽  
Sauter Mean Diameter ◽  
Atomization Process ◽  
Fuel Density ◽  
System Of Units ◽  
Nozzle Size ◽  
Mean Diameter ◽  
Shear Type

Published correlations for the Sauter Mean Diameter (SMD) of sprays produced by pressure atomizing injectors have generally taken the form, SMD = Aω˙B ΔPC. The system of units and the fuel properties are reflected by the coefficient A. The exponent of the flow rate term (B) has been found to be approximately 0.20. There has been less agreement relative to the appropriate value of the pressure drop exponent (C). Simmons [1] reported the value of the pressure drop exponent to be 0.354, and this value has been widely used. This paper presents recently acquired experimental data that reveal that for We greater than 10.0 a different atomization process occurs, i.e., “shear-type” breakup, which results in much finer atomization than predicted by previously reported correlations. To accurately represent the high We data, a significantly different SMD correlation form is required and is reported in this paper. The effects of large variations in the nozzle size, fuel density, viscosity, surface tension, and fuel temperature have been included in the derivation of the correlations.

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.

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

scholarly journals Spray and atomization characteristics of gas-centered swirl coaxial injectors

2016 ◽  
Vol 9 (2) ◽  
pp. 127-140 ◽  
Author(s):  
Rahul Anand ◽  
PR Ajayalal ◽  
Vikash Kumar ◽  
A Salih ◽  
K Nandakumar
Keyword(s):  
Rocket Engine ◽  
Cone Angle ◽  
Spray Angle ◽  
Rocket Engines ◽  
Sauter Mean Diameter ◽  
Swirl Number ◽  
Spray Cone ◽  
Mean Diameter ◽  
Atomization Characteristics ◽  
Coaxial Injector

To achieve uniform and efficient combustion in a rocket engine, a fine uniform spray is needed. The same is achieved by designing an injector with good atomization characteristics. Gas-centered swirl coaxial (GCSC) injector elements have been preferred recently in liquid rocket engines because of an inherent capability to dampen the pressure oscillations in the thrust chamber. The gas-centered swirl coaxial injector chosen for this study is proposed to be used in a semi-cryogenic rocket engine operating with oxidizer rich hot exhaust gases from the pre-burner and liquid kerosene as fuel. In this paper, nine different configurations of gas-centered swirl coaxial injector, sorted out by studying the spray angle and coefficient of discharge with swirl number varying from 9 to 20 and recess ratio of 0.5, 1, and 1.5 are investigated for their atomization characteristics. Spray uniformity, spray cone angle, and droplet size in terms of Sauter mean diameter and mass median diameter are studied at various momentum flux ratios for all configurations. Sauter mean diameter is almost independent of recess ratio, whereas cone angle was inversely proportional to the recess ratio. A finer atomization was observed for injectors of high swirl number but the pressure drop also increased to achieve the same flow rate. An injector of medium swirl number and recess ratio of 1.5 is deemed most fit for above-mentioned application.

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 Prediction on Droplet Sauter Mean Diameter in Gas-Liquid Mist Flow Based on Droplet Fractal Theory

2015 ◽  
Vol 2015 ◽  
pp. 1-4
Author(s):  
Jian-Yi Liu ◽  
Xiao-Hua Tan ◽  
Zhou Fan ◽  
Xu-Tao You ◽  
Zhou Li ◽  
...  
Keyword(s):  
Present Model ◽  
Fractal Theory ◽  
Fractal Model ◽  
Droplet Surface ◽  
Superficial Velocity ◽  
Sauter Mean Diameter ◽  
Model Predictions ◽  
Mist Flow ◽  
Mean Diameter ◽  
Fluid Characteristics

We present a fractal model for droplet Sauter mean diameter in gas-liquid mist flow, based on the droplet fractal theory and the balance relationship between total droplet surface energy and total gas turbulent kinetic energy. The present model is expressed as functions of the droplet fractal dimension, gas superficial velocity, liquid superficial velocity, and other fluid characteristics. Agreement between the present model predictions and experimental measurements is obtained. Results verify the reliability of the present model.

scholarly journals Experimental Study of the Effect of Dense Spray on Drop Size Measurement by Light Scattering Technology

1990 ◽  
Author(s):  
Ju Shan Chin ◽  
Wei Ming Li ◽  
Yan Zhang
Keyword(s):  
Experimental Data ◽  
Light Scattering ◽  
Correction Factor ◽  
Drop Size ◽  
Empirical Equation ◽  
Size Measurement ◽  
Sauter Mean Diameter ◽  
Internal Mixing ◽  
Mean Diameter ◽  
Factor Data

The effect of dense spray on drop size measurement by light scattering technology was studied by using Malvern instrument with five duplicated internal mixing airblast atomizers aligned in line with laser beam. The correction factor data for multiple scattering were obtained. By regression analysis, an empirical equation was obtained which correlated the correction factor as a function of obscuration (OBS), Sauter mean diameter under dilute spray condition SMD0. and drop size distribution parameter for Rosin–Rammler distribution under dilute spray conditions N0. The experimental data showed definitely that the correction factor is not only a function of OBS, SMD0, as proposed by Dodge, but also is a function of N0. The correlation fits the experimental data very well, and can be used for practical purposes to correct the data from Malvern drop sizer at high obscuration conditions.

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