Experiments on Spray Interactions in the Wake of a Bluff Body

1988 ◽  
Vol 110 (1) ◽  
pp. 86-93 ◽  
Author(s):  
R. C. Rudoff ◽  
M. J. Houser ◽  
W. D. Bachalo
Keyword(s):  
Drop Size ◽  
Bluff Body ◽  
Cone Angle ◽  
Field Interaction ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
General Direction ◽  
Size Classes ◽  
Toroidal Vortices ◽  
Spray Field

The dynamics of spray drop interaction within the turbulent wake of a bluff body were investigated using the Aerometrics Phase Doppler Particle Analyzer, which determines both drop size and velocity. Detailed measurements obtained included spray drop size, axial and radial velocity, angle of trajectory, and size-velocity correlations. The gas-phase flow field was also ascertained via the behavior of the smallest drops. Results showed dramatic differences in drop behavior when interacting with turbulence for the various size classes. Small drops were recirculated in a pair of toroidal vortices located behind the bluff body, whereas the larger drops followed the general direction of the spray cone angle. This was documented via backlit photography. Local changes in number density were produced as a result of lateral convection and streamwise accelerations and decelerations of various drop size classes. The spray field interaction illustrated by these data effectively reveals the complexity associated with the development of the spray and casts some doubts toward attempting to describe sprays via simple integral quantities such as the Sauter mean diameter.

Method of Identifying Injector Coking From the Spray Field of Mechanical and CRDi Injectors Using Intensity of Scattered Light

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Ronith Stanly ◽  
Gopakumar Parameswaran ◽  
Bibin Sagaram
Keyword(s):  
Scattered Light ◽  
Near Field ◽  
Cone Angle ◽  
Angle Measurement ◽  
Field Region ◽  
Fuel System ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Cleaning Procedure ◽  
Spray Field

The influence of injector coking deposits on the spray field of single-hole mechanical port fuel injectors and multihole common rail direct injection (CRDi) injectors was studied using light scattering technique coupled with image processing and analysis. Instead of employing the traditional accelerated coking process to study injector spray field deterioration, in-service injectors were selected and cleaned using a commercial fuel system cleaning procedure. Variation in atomization characteristics of coked and cleaned injectors were observed based on the spatial distribution of fine, medium, and coarse droplets in the near-field region of the injector spray zone and analyzed as a function of the intensity of scattered light. The improvement in the atomization perceived by this method was compared with traditional techniques like spray cone angle measurement, speed characterization of spray jets, and weight reduction of injector nozzles and needles. It was observed that after the fuel system cleaning procedure, a reduction in the number of coarse droplets in the near-field region and an increase in the number of medium and finely sized droplets was observed, suggesting better atomization of fuel in the near field spray zone.

Experimental Study on Spray Pattern of Pressure-Swirl Nozzle in Reactor Containment

2018 ◽  
Author(s):  
Jiawei Bian ◽  
Dalin Zhang ◽  
Rulei Sun ◽  
Yingwei Wu ◽  
Wenxi Tian ◽  
...  
Keyword(s):  
Experimental Study ◽  
Optimization Design ◽  
Flux Distribution ◽  
Cone Angle ◽  
Distribution Models ◽  
Spray Droplet ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Spray Field ◽  
Pressure Swirl

Spraying system plays an important role in the safety of PWR. To ensure homogeneous spraying of the containment, the layout of nozzles on the spray header was taken into consideration in design. In this paper, an experimental study was conducted to obtain spray characteristics data, including spray cone angle and 2-D spray flux distribution for the purpose of achieving optimal design of the spraying system. According to the specialty of the spray field involved, a testing loop with four pressure-swirl nozzles was established for the study. Spray cone angles were obtained by photograph method. The volume flux distribution was measured by collecting the spray droplet along the cross-section diameters. Based on the experimental data, typical spray flux distributions were obtained. The flux distribution results were used to build 3-D coverage models. Then these models were used to calculate the overall spray coverage in the containment. The present work introduces the experimental study of spray behavior of a typical pressure-swirl nozzle in containment and the method to evaluate spray coverage through building 3-D spray flux distribution models. The work is expected to be helpful for the optimization design of spraying systems.

Influence of Ambient Air Pressure on Pressure-Swirl Atomization

1987 ◽  
Author(s):  
X. F. Wang ◽  
A. H. Lefebvre
Keyword(s):  
Drop Size ◽  
Cone Angle ◽  
Ambient Air ◽  
Air Pressure ◽  
Spray Angle ◽  
Flow Number ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Continuous Increase ◽  
Pressure Swirl

The spray characteristics of six simplex atomizers are examined in a pressure vessel using a standard light diffraction technique. Attention is focused on the effects of liquid properties, nozzle flow number, spray cone angle, and ambient air pressure on mean drop size and drop-size distribution. For all nozzles and all liquids it is found that continuous increase in air pressure above the normal atmospheric value causes the SMD to first increase up to a maximum value and then decline. An explanation for this characteristic is provided in terms of the measurement technique employed and the various competing influences on the overall atomization process. The basic effect of an increase in air pressure is to improve atomization, but this trend is opposed by contraction of the spray angle which reduces the relative velocity between the drops and the surrounding air, and also increases the possibility of droplet coalescence.

Atomization Characteristics of Jatropha-Derived Alternative Aviation Fuels From Aircraft Engine Injector

2017 ◽  
Author(s):  
Ramachandran Sakthikumar ◽  
Deivandren Sivakumar ◽  
B. N. Raghunandan ◽  
John T. C. Hu
Keyword(s):  
Size Distribution ◽  
Drop Size ◽  
Cone Angle ◽  
Fuel Spray ◽  
Jet Fuels ◽  
Spray Characteristics ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Atmospheric Air ◽  
Atomization Characteristics

Search for potential alternative jet fuels is intensified in recent years to meet stringent environmental regulations imposed to tackle degraded air quality caused by fossil fuel combustion. The present study describes atomization characteristics of blends of jatropha-derived biofuel with conventional aviation kerosene (Jet A-1) discharging into ambient atmospheric air from a dual-orifice atomizer used in aircraft engines. The biofuel blends are characterized in detail and meet current ASTM D7566 specifications. The experiments are conducted by discharging fuel spray into quiescent atmospheric air in a fuel spray booth to measure spray characteristics such as fuel discharge behavior, spray cone angle, drop size distribution and spray patternation at six different flow conditions. The characteristics of spray cone angle are obtained by capturing images of spray and the measurements of spray drop size distribution are obtained using laser diffraction particle analyzer (LDPA). A mechanical patternator system comprising 144 measurement cells is used to deduce spray patternation at different location from the injector exit. A systematic comparison on the atomization characteristics between the sprays of biofuel blends and the 100% Jet A-1 is presented. The measured spray characteristics of jatropha-derived alternative jet fuels follow the trends obtained for Jet A-1 sprays satisfactorily both in qualitative and quantitative terms.

Influence of Geometric Features on the Performance of Pressure-Swirl Atomizers

1990 ◽  
Vol 112 (4) ◽  
pp. 579-584 ◽  
Author(s):  
S. K. Chen ◽  
A. H. Lefebvre ◽  
J. Rollbuhler
Keyword(s):  
Drop Size ◽  
Cone Angle ◽  
Diameter Ratio ◽  
Working Fluid ◽  
Spray Characteristics ◽  
Spray Cone Angle ◽  
Liquid Distribution ◽  
Spray Cone ◽  
Pressure Swirl ◽  
Discharge Orifice

The spray characteristics of several different simplex pressure-swirl nozzles are examined using water as the working fluid. Measurements of mean drop size, dropsize distribution, effective spray cone angle, and circumferential liquid distribution are carried out over wide ranges of injection pressure. Eight different nozzles are employed in order to achieve a wide variation in the length/diameter ratio of the final discharge orifice. Generally, it is found that an increase in discharge orifice length/diameter ratio (lo/do) increases the mean drop size in the spray and reduces the spray cone angle. The circumferential liquid distribution is most uniform when lo/do=2. If lo/do is raised above or lowered below this optimum value, the circumferential uniformity of the liquid distribution is impaired. The observed effects of lo/do on spray characteristics are generally the same regardless of whether the change in lo/do is accomplished by varying lo or do.

scholarly journals Prediction of the Initial Drop Size and Velocity Distribution in the Cold Cryogenic Spray

2020 ◽  
Vol 38 (3) ◽  
pp. 629-640
Author(s):  
Ahmed Abed Al-Kadhem Majhool ◽  
Noor Mohsin Jasim
Keyword(s):  
Velocity Distribution ◽  
Size Distribution ◽  
Liquid Nitrogen ◽  
Drop Size ◽  
Maximum Entropy Method ◽  
Cone Angle ◽  
Injection Pressure ◽  
Entropy Method ◽  
Spray Cone Angle ◽  
Spray Cone

The polydispersed nature of the spray is captured through the use of probability density functions based on the maximum entropy method to stand for the complete atomization characteristics of spray dynamics. The droplet and velocity size distributions are practical tools for the analysis of sprays cooling. The special benefit of the model is a Eulerian based which is less computationally intensive when compared to models that are based on the Lagrangian approach that tracks droplet parcel. The accuracy of using Lagrangian approach in polydispersed phase is always accurately less than Eulerian approach because it depends on the number of parcels while in Eulerian approach it depends on the proposed continuous distribution function. The main intent of the current work is to evaluate the capability of using the model for the initial predictions of the droplet size and velocity distribution for liquid nitrogen spray of solid-cone pressure swirl nozzle. The use of liquid injection pressure cases of up to 0.6MPa and spray cone angles of just 30◦ from three different sets of experimental data. The results being characterized are spray drop size distribution, liquid volume fraction and spray cone angle values. The unsteady analyses of the effect of injection pressure are studied on the cryogenic liquid nitrogen. The numerical results show that the maximum entropy method applies to liquid cryogenic spray and indicates that the model reacts correctly to changes in different injection pressures. Comparisons are also made with measured drop size distribution data that are reasonably captured and the spray cone angle is found to be in good agreement during initial and far-field spray angles.

Spray Characteristics of a Spill-Return Airblast Atomizer

1989 ◽  
Vol 111 (1) ◽  
pp. 63-69 ◽  
Author(s):  
X. F. Dai ◽  
A. H. Lefebvre ◽  
J. Rollbuhler
Keyword(s):  
Drop Size ◽  
Cone Angle ◽  
Working Fluid ◽  
Air Velocity ◽  
Spray Characteristics ◽  
Spray Cone Angle ◽  
Liquid Distribution ◽  
Spray Cone ◽  
Liquid Injection ◽  
Bypass Ratio

The spray characteristics of a spill-return airblast atomizer are examined using water as the working fluid. Measurements of mean drop size, drop size distribution, spray cone angle, and circumferential liquid distribution are carried out over wide ranges of liquid injection pressures and atomizing air velocities. Generally it is found that an increase in nozzle bypass ratio worsens the atomization quality and widens the spray cone angle. Increase in airblast air velocity may improve or impair atomization quality depending on whether it increases or decreases the relative velocity between the liquid and the surrounding air. Airblast air can also be used to modify the change in spray cone angle that normally accompanies a change in bypass ratio.

Experimental Parametric Analysis of Water-Mist Sprays: An Investigation on Coalescence and Initial Dispersion

2011 ◽  
Author(s):  
Paolo E. Santangelo ◽  
Paolo Tartarini ◽  
Paolo Valdiserri
Keyword(s):  
Parametric Analysis ◽  
Drop Size ◽  
Cone Angle ◽  
Three Dimensional ◽  
Geometric Approach ◽  
Water Mist ◽  
Orifice Diameter ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Flux Measurements

An experimental approach and parametric analysis are here presented to investigate some dynamic aspects of water-mist sprays operating at high supply pressure. An already proposed methodology (P.E. Santangelo, 2010, Exp. Therm. Fluid Sci., 34, pp. 1353–1366) has been extended to a three-dimensional analysis, that emphasizes the characteristic drop-size evolution along the axial coordinate of the spray. Therefore, an evaluation of coalescence and secondary-atomization phenomena along the spray axis results as the ultimate scope of this study. With regard to dispersion, the initial-velocity field has been experimentally determined both as a contour/vector map and as magnitude profiles at different distances from the injector outlet. In addition, some evaluation of the spray-cone angle has been proposed, resulting from a simple geometric approach to the already mentioned maps. Advanced laser-based diagnostics has been employed to perform experimental measurements: a Malvern Spraytec device has been used to measure drop-size distribution and Particle Image Velocimetry has been chosen to evaluate both velocity and cone angle. Moreover, a mechanical patternator has been employed to introduce flux measurements as an averaging quantity. Two nozzles having different orifice diameter have been employed and operative pressure has been set at a value of interest for fire-protection applications.

Gas Turbine Inlet Air Cooling: Determination of Parameters to Evaluate Fogging Nozzle’s Atomizing Performance

2003 ◽  
Author(s):  
Sanjay Mahapatra ◽  
Jeffrey K. Gilstrap
Keyword(s):  
Gas Turbine ◽  
Surface Area ◽  
Drop Size ◽  
Cone Angle ◽  
Air Cooling ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Droplet Distribution ◽  
Turbine Inlet ◽  
Air Stream

Gas turbine inlet air-cooling using a fogging system is accomplished by using an array of high-pressure nozzles that inject micron-sized droplets in air stream. These droplets evaporate and diffuse in the air stream resulting in cooling and humidification of air. The cooled and moist inlet air increases net turbine power output, improves heat rate and reduces Nitrogen Oxides formation (NOx). The evaporation and mass diffusion of these droplets are influenced, among other factors, by its surface area to volume ratio. Large surface area facilitates drop interfacial heat transfer and smaller volume or weight aids higher droplet residence times. A fogging nozzle’s atomizing performance can be evaluated from its spray properties that include a mean drop size, droplet distribution, numerical droplet density, spray cone angle, and spray penetration. The spray industry adopts various definitions of mean drop size that suits its application and objective. Mean drop sizes or more commonly droplet diameters used in the gas turbine inlet air fogging industry are 90% cumulative volume frequency, Dv0.90 and the Sauter Mean Diameter, D32. Two sprays having identical mean or representative diameter are not necessarily similar in performance. Further, a spray from nozzle ‘A’ having a Dv0.90 less than another nozzle ‘B’ does not necessarily imply that ‘A’ is superior to ‘B’. This paper explains why the use of one or both of the above characteristic diameters does not effectively reflect a fog nozzle’ atomizing performance. This paper also analyzes various characteristic diameters and their relevance to evaporative cooling using fog nozzles. In fogging applications, the smallest and/or the largest sized drops in a spray will have significant impact on performance and neither Dv0.90 nor D32 can independently provide this information. Therefore, at least one other parameter such as the droplet distribution must be known in order to qualitatively define a spray from a fogging nozzle. This paper also determines these parameters such as the Relative Span Factor and Dispersion Boundary Factor and analyzes their importance to fogging performance.

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