scholarly journals The Interdependence of Spray Characteristics and Evaporation History of Fuel Sprays in Stagnant Air

1983 ◽  
Author(s):  
J. S. Chin ◽  
R. Durrett ◽  
A. H. Lefebvre
Keyword(s):  
Size Distribution ◽  
Drop Size ◽  
Simple Calculation ◽  
Drop Size Distribution ◽  
Drop Diameter ◽  
Transient Effects ◽  
Spray Characteristics ◽  
Full Account ◽  
Mass Evaporation ◽  
Time Required

A simple calculation method based on an evaporation analysis proposed previously [1] [2] is used to predict the variation of JP-5 fuel spray characteristics (median drop diameter, Dm, and drop-size distribution parameter, n) with time during evaporation in stagnant hot air. The method takes full account of transient effects occurring during the heat-up period. The results show that Dm increases with time, and so also does n, indicating that the drop-size distribution narrows with passage of time. The time to vaporize any given fraction of the spray mass is found to be proportional to D2mo. The effect of the initial value of n, no, is that a spray having a large value of no will reach its 90% evaporation point faster, but a smaller value of no will give a shorter 20% evaporation time. Based on these calculations, a general method for estimating the time required for any liquid fuel to attain any given percentage of spray mass evaporation in stagnant air is proposed.

The Interdependence of Spray Characteristics and Evaporation History of Fuel Sprays

1984 ◽  
Vol 106 (3) ◽  
pp. 639-644 ◽  
Author(s):  
J. S. Chin ◽  
R. Durrett ◽  
A. H. Lefebvre
Keyword(s):  
Drop Diameter ◽  
Transient Effects ◽  
Gas Turbine Combustor ◽  
Spray Characteristics ◽  
Full Account ◽  
Hot Air ◽  
History Of ◽  
Mass Evaporation ◽  
Time Required ◽  
General Method

Previously developed calculation procedures [1, 2] based on evaporation analysis are used to predict the variation of JP-5 fuel spray characteristics (mean drop diameter, Dm, and drop-size distribution parameter, n) with time during evaporation in hot air. The method takes full account of transient effects occurring during the heat-up period. The results show that both Dm and n increase with time, but the changes are more significant for sprays having small initial values of n. The time to vaporize a certain percentage of spray mass is proportional to the square of the initial mean diameter, Dmo. The effect of the initial value of n, is that a spray having a larger value of no will reach its 90 percent evaporation point faster, but a smaller value of no will give a shorter 20 percent evaporation time. Based on these calculations, a general method for estimating the time required for any liquid fuel to attain any given percentage of spray mass evaporation is proposed. Although the method was developed for quiescent mixtures of fuel drops and air, it can be applied to many practical combustion devices (for example, a gas turbine combustor fitted with airblast atomizers) where it is reasonable and sufficiently accurate to assume a low relative velocity between the fuel drops and the surrounding air or gas.

Influence of Downstream Distance on the Spray Characteristics of Pressure-Swirl Atomizers

1986 ◽  
Vol 108 (1) ◽  
pp. 219-224 ◽  
Author(s):  
J. S. Chin ◽  
D. Nickolaus ◽  
A. H. Lefebvre
Keyword(s):  
Size Distribution ◽  
Drop Size ◽  
Fuel Injection ◽  
Injection Pressure ◽  
Ambient Air ◽  
Drop Size Distribution ◽  
Axial Distance ◽  
Spray Characteristics ◽  
Full Account ◽  
Pressure Swirl

An analytical study is made of the factors that are responsible for the observed changes in fuel spray characteristics with axial distance downstream of a pressure-swirl nozzle. To simplify the analysis the effect of fuel evaporation is neglected, but full account is taken of the effects of spray dispersion and drop acceleration (or deceleration). Equations are derived and graphs are presented to illustrate the manner and extent to which the variations of mean drop size and drop-size distribution with axial distance are governed by such factors as ambient air pressure and velocity, fuel injection pressure, initial mean drop size, and initial drop-size distribution.

An Analysis of Errors in Drop Size Distribution Retrievals and Rain Bulk Parameters with a UHF Wind Profiling Radar and a Two-Dimensional Video Disdrometer

2008 ◽  
Vol 25 (12) ◽  
pp. 2282-2292 ◽  
Author(s):  
Laura Kanofsky ◽  
Phillip Chilson
Keyword(s):  
Error Analysis ◽  
Size Distribution ◽  
Drop Size ◽  
Ambient Air ◽  
Drop Size Distribution ◽  
Rainfall Rate ◽  
Doppler Velocity ◽  
Drop Diameter ◽  
Fall Speed ◽  
Air Motion

Abstract Vertically pointed wind profiling radars can be used to obtain measurements of the underlying drop size distribution (DSD) for a rain event by means of the Doppler velocity spectrum. Precipitation parameters such as rainfall rate, radar reflectivity factor, liquid water content, mass-weighted mean drop diameter, and median volume drop diameter can then be calculated from the retrieved DSD. The DSD retrieval process is complicated by the presence of atmospheric turbulence, vertical ambient air motion, selection of fall speed relationships, and velocity thresholding. In this note, error analysis is presented to quantify the effect of each of those factors on rainfall rate. The error analysis results are then applied to two precipitation events to better interpret the rainfall-rate retrievals. It was found that a large source of error in rain rate is due to unaccounted-for vertical air motion. For example, in stratiform rain with a rainfall rate of R = 10 mm h−1, a mesoscale downdraft of 0.6 m s−1 can result in a 34% underestimation of the estimated value of R. The fall speed relationship selection and source of air density information both caused negligible errors. Errors due to velocity thresholding become more important in the presence of significant contamination near 0 m s−1, such as ground clutter. If particles having an equivalent volume diameter of 0.8 mm and smaller are rejected, rainfall rate errors from −4% to −10% are possible, although these estimates depend on DSD and rainfall rate.

Swirl and Counterswirl Effects in Prefilming Airblast Atomizers

1988 ◽  
Vol 110 (1) ◽  
pp. 105-110 ◽  
Author(s):  
M. Aigner ◽  
S. Wittig
Keyword(s):  
Shear Flow ◽  
Size Distribution ◽  
Nozzle Exit ◽  
Drop Size ◽  
Recirculation Zone ◽  
Drop Size Distribution ◽  
Shear Stresses ◽  
Spray Characteristics ◽  
Air Supply

The performance characteristics of prefilming airblast atomizers depend largely on the shear stresses in each of the two air supply channels. As an extension of previously reported results, experiments were conducted using an atomizer model with separately controlled air ducts and typical prototype nozzles. It was shown that the quality of atomization can be limited due to internal droplet formation. However, the velocity profiles of the atomization air and the properties of the liquid are the dominant parameters that determine the drop-size distribution generated at the atomization edge. The shear flow at the nozzle exit and the recirculation zone depend largely on the swirl or counterswirl of the exiting air. Correlations have been obtained between the spray characteristics and the relevant parameters.

scholarly journals Phase Space Parameterization of Rain: The Inadequacy of Gamma Distribution

2014 ◽  
Vol 53 (2) ◽  
pp. 548-562 ◽  
Author(s):  
Massimiliano Ignaccolo ◽  
Carlo De Michele
Keyword(s):  
Phase Space ◽  
Size Distribution ◽  
Gamma Distribution ◽  
Goodness Of Fit ◽  
Drop Size ◽  
Cartesian Product ◽  
Drop Size Distribution ◽  
Drop Diameter ◽  
Goodness Of Fit Test ◽  
Kolmogorov Smirnov

AbstractThe authors test the adequacy of gamma distribution to describe the statistical variability of raindrop diameters in 1-min disdrometer data using the Kolmogorov–Smirnov goodness-of-fit test. The results do not support the use of this distribution, with a percentage of rejected cases that increases with the sample size. A different parameterization of the drop size distribution is proposed that does not require any particular functional form and is based on the adoption of statistical moments. The first three moments, namely the mean, standard deviation, and skewness, are sufficient to characterize the distribution of the drop diameter at the ground. These parameters, together with the drop count, form a 4-tuple, which fully describes the variability of the drop size distribution. The Cartesian product of this 4-tuple of parameters is the rainfall phase space. Using disdrometer data from 10 different locations, invariant, location-independent properties of rainfall are identified.

Disdrometer Gravitational Sorting Signature in a Mediterranean Environment

2020 ◽  
Author(s):  
Takis Kasparis ◽  
Silas Michaelides ◽  
John Lane
Keyword(s):  
Size Distribution ◽  
Sea Level ◽  
Drop Size ◽  
Meteorological Station ◽  
Drop Size Distribution ◽  
Negative Slope ◽  
Drop Diameter ◽  
Scatter Plot ◽  
Mediterranean Environment ◽  
Mean Sea Level

<p>The motivation behind this research was initially the observation and the subsequent modelling of the gravitational sorting of precipitation in disdrometer-based spectra. The gravitational sorting signature (GSS) is expected to be observed when every drop impact measured by the disdrometer is time tagged and then displayed as a scatter plot diagram of drop diameter (D) versus time (t). The resulting D-t diagrams exhibit marked diagonal features and gravitational sorting signatures are characterized by a negative slope. However, because of the way that manufacturers and researchers process disdrometer data, this signature is typically wiped out. </p><p>This research is based on the assumption that if a rain producing cloud that goes through a complete rain process from start to end, remains fixed (no advection) over a disdrometer site, then some GSS should occur; if advection dominates, then GSS may not be observable.  In this latter case, the precipitating cloud may move over the disdrometer. In this paper, two cases are presented one in which GSS was detected and another in which GSS was absent.</p><p>The disdrometer data used in this study were recorded by using a Joss-Waldvogel impact disdrometer located on the roof of a building of the meteorological station at Athalassa, Cyprus (35.15°N, 33.40°, 161.0 m above Mean Sea Level, MSL). The Joss-Waldvogel impact disdrometer used is able to record drop diameters from 0.3mm to 5.5mm in ten-second intervals, allowing for the establishment of the Drop Size Distribution (DSD) representing this range of drop sizes.</p>

Evaluation of GPM Dual-Frequency Precipitation Radar Algorithms to Estimate Drop Size Distribution Parameters, Using Ground-Based Measurement over the Central Andes of Peru

2021 ◽  
Author(s):  
Carlos Del Castillo-Velarde ◽  
Shailendra Kumar ◽  
Jairo M. Valdivia-Prado ◽  
Aldo S. Moya-Álvarez ◽  
Jose Luis Flores-Rojas ◽  
...  
Keyword(s):  
Size Distribution ◽  
Drop Size ◽  
Central Andes ◽  
Drop Size Distribution ◽  
Dual Frequency ◽  
Precipitation Radar ◽  
Distribution Parameters

Dispersed phase holdup and drop size distribution in pulsed plate columns

1988 ◽  
Vol 66 (2) ◽  
pp. 232-240 ◽  
Author(s):  
A. Prabhakar ◽  
G. Sriniketan ◽  
Y. B. G. Varma
Keyword(s):  
Size Distribution ◽  
Drop Size ◽  
Drop Size Distribution ◽  
Dispersed Phase
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