Experimental Characterization of Sprays in a Recessed Gas-Centered Swirl Coaxial Atomizer

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
A. Joseph ◽  
R. Sakthikumar ◽  
D. Sivakumar
Keyword(s):  
Momentum Flux ◽  
Drop Size ◽  
Flux Ratio ◽  
Experimental Characterization ◽  
Liquid Sheets ◽  
Phase Doppler Interferometry ◽  
Radial Profiles ◽  
Spray Droplets ◽  
The Mean

Abstract The characteristics of sprays from a recessed gas-centered swirl coaxial atomizer (RGCSCA) with gas to liquid momentum flux ratio, J of the spray in the range of 2–66 are studied experimentally through the analysis of spray morphologies and droplets characteristics. The process of fully developed spray (spray free from ligaments/droplets clusters and nonspherical droplets) in the atomizer is quantified. In the RGCSCA, the distance from the atomizer exit to the fully developed spray zone decreases with increase in J. Detailed measurements of size (in the range of 6–378 μm) and velocity (in the range of 35–176 m/s) characteristics of spray droplets are carried out using phase Doppler interferometry (PDI) in the fully developed spray. The spray from the RGCSCA is comprised of two distinct spray morphologies: a central dense spray of finer droplets and an outer coarse spray. The mean drop size of the central spray exhibits a decreasing trend with the increase in J whereas that of the outer coarse spray is independent of J. The radial profiles of the mean velocities of sprays at different J are presented. For the sprays with low inertia liquid sheets, the shape of mean axial velocity profiles is Gaussian.

scholarly journals Drop Size Characteristics of Forward Angled Injectors in Subsonic Cross Flows

2013 ◽  
Author(s):  
Venkat S. Iyengar ◽  
Sathiyamoorthy Kumarasamy ◽  
Srinivas Jangam ◽  
Manjunath Pulumathi
Keyword(s):  
Gas Turbine ◽  
Test Section ◽  
Momentum Flux ◽  
Drop Size ◽  
Cross Flow ◽  
Flux Ratio ◽  
Liquid Jet ◽  
Axial Distance ◽  
Momentum Flux Ratio ◽  
Spray Plume

Cross flow fuel injection is a widely used approach for injecting liquid fuel in gas turbine combustors and afterburners due to the higher penetration and rapid mixing of fuel and the cross flowing airstream. Because of the very limited residence time available in these combustors it is essential to ensure that smaller drop sizes are generated within a short axial distance from the injector in order to promote effective mixing. This requirement calls for detailed investigations into spray characteristics of different injector configurations in a cross-flow environment for identifying promising configurations. The drop size characteristics of a liquid jet issuing from a forward angled injector into a cross-flow of air were investigated experimentally at conditions relevant to gas turbine afterburners. A rig was designed and fabricated to investigate the injection of liquid jet in subsonic cross-flow with a rectangular test section of cross section measuring 50 mm by 70 mm. Experiments were done with a 10 degree forward angled 0.8 mm diameter plain orifice nozzle which was flush mounted on the bottom plate of test section. Laser diffraction using Malvern Spraytec particle analyzer was used to measure drops size and distributions in the near field of the spray. Measurements were performed at a distance of 70 mm from the injector at various locations along the height of the spray plume for a reasonable range of liquid flow rates as in practical devices. The sprays were characterized using the non dimensional parameters such as the Weber number and the momentum flux ratio and drop sizes were measured at three locations along the height of the spray from the bottom wall. The momentum flux ratio was varied from 5 to 25. Results indicate that with increase in momentum flux ratio the SMD reduced at the specific locations and an higher overall SMD was observed as one goes from the bottom to the top of the spray plume. This was accompanied by a narrowing of the drop size distribution.

Liquid Jets in Subsonic Air Crossflow at Elevated Pressure

2014 ◽  
Vol 137 (4) ◽  
Author(s):  
Jinkwan Song ◽  
Charles Cary Cain ◽  
Jong Guen Lee
Keyword(s):  
Weber Number ◽  
Momentum Flux ◽  
Drop Size ◽  
Density Ratio ◽  
Flux Ratio ◽  
Mie Scattering ◽  
Air Pressure ◽  
Scattering Intensity ◽  
Nozzle Orifice ◽  
Momentum Flux Ratio

The breakup, penetration, droplet size, and size distribution of a Jet A-1 fuel in air crossflow has been investigated with focus given to the impact of surrounding air pressure. Data have been collected by particle Doppler phased analyzer (PDPA), Mie-scattering with high speed photography augmented by laser sheet, and Mie-scattering with intensified charge-coupled device (ICCD) camera augmented by nanopulse lamp. Nozzle orifice diameter, do, was 0.508 mm and nozzle orifice length to diameter ratio, lo/do, was 5.5. Air crossflow velocities ranged from 29.57 to 137.15 m/s, air pressures from 2.07 to 9.65 bar, and temperature held constant at 294.26 K. Fuel flow provides a range of fuel/air momentum flux ratio (q) from 5 to 25 and Weber number from 250 to 1000. From the results, adjusted correlation of the mean drop size has been proposed using drop size data measured by PDPA as follows: (D0/D32)=0.267Wea0.44q0.08(ρl/ρa)0.30(μl/μa)-0.16. This correlation agrees well and shows roles of aerodynamic Weber number, Wea, momentum flux ratio, q, and density ratio, ρl/ρa. Change of the breakup regime map with respect to surrounding air pressure has been observed and revealed that the boundary between each breakup modes can be predicted by a transformed correlation obtained from above correlation. In addition, the spray trajectory for the maximum Mie-scattering intensity at each axial location downstream of injector is extracted from averaged Mie-scattering images. From these results, correlations with the relevant parameters including q, x/do, density ratio, viscosity ratio, and Weber number are made over a range of conditions. According to spray trajectory at the maximum Mie-scattering intensity, the effect of surrounding air pressure becomes more important in the farfield. On the other hand, effect of aerodynamic Weber number is more important in the nearfield.

Experimental Characterization of Aerosol Production, Transport, Vaporization, and Atomization Systems. Part II: Factors Controlling Aerosol Size Distributions Produced

1985 ◽  
Vol 39 (6) ◽  
pp. 920-925 ◽  
Author(s):  
R. K. Skogerboe ◽  
S. J. Freeland
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Cross Flow ◽  
Size Distributions ◽  
Experimental Characterization ◽  
Gas Flow Rate ◽  
Mean Size ◽  
The Mean ◽  
Model Equations

The effects of nebulization conditions on the size characteristics of the aqueous aerosol produced have been investigated for a cross-flow nebulizer. It is shown that the nebulizer gas flow rate does not affect the upper limit mean sizes of the aqueous droplets transported from the nebulization chamber but that the mean size of the analyte-containing aerosol itself is affected. Model equations are presented descriptive of the effects of gas flow rate and analyte concentrations on analyte aerosol size characteristics.

Characterization of Spray Formed by Liquid Jet Injected Into Oscillating Air Crossflow

2015 ◽  
Author(s):  
Jinkwan Song ◽  
Jong Guen Lee
Keyword(s):  
Weber Number ◽  
Momentum Flux ◽  
Drop Size ◽  
Flux Ratio ◽  
Mie Scattering ◽  
Liquid Jet ◽  
Velocity Modulation ◽  
Momentum Flux Ratio ◽  
Crossflow Velocity ◽  
Modulation Level

This paper presents experimental results on the characteristics of spray formed by a liquid (Jet-A) jet injected into an oscillating air crossflow. Ambient air pressure is raised up to 15.86 bar, and the corresponding aerodynamic Weber number and liquid-air momentum flux ratio are up to 1000 and 25, respectively. The level of modulated crossflow velocity is kept up to 20% of its mean value. For limited cases, the air crossflow is preheated. Planar Mie-scattering measurements are utilized to visualize changes of the spray penetration and cross-sectional spray area in the oscillating air crossflow, and PDPA measurements are used to measure the mean drop size and drop size distribution. Phase-synchronized PDPA measurement of droplet size under the modulation of crossflow shows that the modulating crossflow results in preferentially larger amount of smaller and bigger droplets than average-sized droplets. Global spray response of spray to modulating crossflow is characterized by using proper orthogonal decomposition (POD) analysis of Mie-scattering images and collecting (and hence determining gain of) Mie-scattering intensity of droplets at a fixed downstream distance. It is found that the dominant behavior of the spray is convective oscillation in the axial direction and the change of vertical penetration of the spray is almost negligible for the level of crossflow velocity modulation up to 20%. The gain of Mie-scattering intensity with respect to crossflow velocity modulation level gradually decreases as liquid-air momentum flux ratio increases. Also, per given momentum flux ratio and Weber number, the gain hardly varies with respect to crossflow modulation level, suggesting the response of spray increases in proportion to crossflow velocity modulation level.

Experimental Investigation of a High Velocity Gaseous Jet Injection Into an Oscillating Crossflow

2021 ◽  
Author(s):  
Jinkwan Song ◽  
Johnathan Wilson ◽  
Jong Guen Lee
Keyword(s):  
Velocity Fluctuation ◽  
Momentum Flux ◽  
Modulation Frequency ◽  
Concentration Field ◽  
Flux Ratio ◽  
Mean Velocity ◽  
Potential Core ◽  
Crossflow Velocity ◽  
The Mean ◽  
Jet Penetration

Abstract This paper presents the experimental results of a gaseous jet injected into an oscillating-air crossflow. The jet to crossflow momentum flux ratios are chosen as 19, 30 and 58, and the mean air crossflow velocities are chosen as 10m/s, 25 m/s, and 60 m/s. The crossflow is modulated at frequencies up to 280 Hz with a maximum crossflow velocity fluctuation of 30% of its mean velocity. Acetone planar laser-induced fluorescence is used to record the instantaneous jet concentration field. Three distinct regions are observed near the injection location (x/d < 18); the jet core, the fast bending zone, and the fully developed plume zone. The location of the end of potential core can be determined primarily by the momentum flux ratio. Based on observations of these three regions, a set of correlations for the trajectory of maximum jet concentration is proposed for the potential core region and for the fully developed plume zone. The potential core responds quasi-steadily to the crossflow oscillation and the fluctuation of penetration of the potential core zone linearly increases with respect to the crossflow velocity fluctuation level. The jet penetration under oscillating crossflow is slightly lower than that under steady crossflow, especially when the mean crossflow velocity is low (10–25 m/s). However, the differences of trajectories between the oscillating and the steady crossflow cases become almost negligible as the mean crossflow velocity increases further. The axial decay of jet concentration under oscillating crossflow occurs at faster rate than that under steady crossflow, indicating that the oscillating air crossflow enhances the mixing between the jet and the crossflow. The vertical jet concentration profile at different axial location confirms that the main effect of crossflow modulation is enhanced mixing of jet with crossflow. However, no noticeable effect of modulation frequency of crossflow on the jet penetration is found.

CFD Modeling of the Atomization of Plain Liquid Jets in Cross Flow for Gas Turbine Applications

2004 ◽  
Author(s):  
Sachin Khosla ◽  
D. Scott Crocker
Keyword(s):  
Momentum Flux ◽  
Drop Size ◽  
Fuel Injection ◽  
Cross Flow ◽  
Flux Ratio ◽  
Wake Flow ◽  
Cfd Modeling ◽  
Liquid Jets ◽  
Momentum Flux Ratio ◽  
Primary Breakup

A numerical model for liquid jet atomization in a subsonic gas cross flow has been developed and incorporated into a CFD code. The model is designed primarily for the shear breakup regime, which is appropriate for many fuel injection applications. The model considers Weber number and momentum flux ratio ranges that are dominated by either jet surface breakup or column breakup. A boundary layer stripping model has been modified to account for both shearing from the column and shear primary breakup of large drops. Further secondary breakup was modeled with the Rayleigh-Taylor model. The effect of drop distortion on the drag is also considered. Results of the model have been compared with experimental data for jet-A liquid jets in air cross flows with varying pressure, air velocity, and liquid-to-gas momentum flux ratio. Comparisons were made for drop volume flux and drop size as a function of distance from the injector wall. Trends were captured for liquid penetration associated with varying momentum flux ratio, and for drop size as a function distance from the wall. In general, agreement between measurements and CFD predictions were quite good. Areas of disagreement could be reasonably explained by the model’s inherent inability to capture the wake flow behind the liquid column.

Liquid Jets in Subsonic Air Crossflow at Elevated Pressure

2014 ◽  
Author(s):  
Jinkwan Song ◽  
Charles Cary Cain ◽  
Jong Guen Lee
Keyword(s):  
Weber Number ◽  
Momentum Flux ◽  
Drop Size ◽  
Density Ratio ◽  
Flux Ratio ◽  
Mie Scattering ◽  
Air Pressure ◽  
Scattering Intensity ◽  
Nozzle Orifice ◽  
Momentum Flux Ratio

The breakup, penetration, droplet size and size distribution of a Jet A-1 fuel in air crossflow has been investigated with focus given to the impact of surrounding air pressure. Data has been collected by Particle Doppler Phased Analyzer (PDPA), Mie-Scattering with high speed photography augmented by laser sheet, and Mie-Scattering with ICCD Camera augmented by nano-pulse lamp. Nozzle orifice diameter, do, was 0.508 mm and nozzle orifice length to diameter ratio, lo/do, was 5.5. Air crossflow velocities ranged from 29.57 to 137.15 m/s, air pressures from 2.07 to 9.65 bar and temperature held constant at 294.26 K. Fuel flow was governed to provide a range of fuel/air momentum flux ratio q from 5 to 25 and Weber number from 250 to 1000. From the results, adjusted correlation of the mean drop size has been suggested using drop size data measured by PDPA as follows; (1)D0D32=0.267Wea0.44q0.08ρlρa0.30μlμa-0.16This correlation agrees well and shows roles of aerodynamic Weber number, Wea, momentum flux ratio, q, and density ratio, ρl/ρa. Change of the breakup regime map with respect with surrounding air pressure has been observed and revealed that the boundary between each breakup modes can be predicted by a transformed correlation induced from above correlation. In addition, the spray trajectory for the maximum Mie-scattering intensity at each axial location downstream of injector was extracted from averaged Mie-scattering images. From these results correlations with the relevant parameters including q, x/do, density ratio, viscosity ratio, and Weber number are made over a range of conditions. According to spray trajectory at the maximum Mie-scattering intensity, the effect of surrounding air pressure becomes more important in the farfield. On the other hand, effect of aerodynamic Weber number is more important in the nearfield.

scholarly journals Effects of Swirl on the Stabilization of Non-Premixed Oxygen-Enriched Flames Above Coaxial Injectors

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
A. Degeneve ◽  
C. Mirat ◽  
J. Caudal ◽  
R. Vicquelin ◽  
T. Schuller
Keyword(s):  
Oxygen Concentration ◽  
Momentum Flux ◽  
Flame Structure ◽  
Flux Ratio ◽  
Operating Conditions ◽  
Momentum Flux Ratio ◽  
Annular Jet ◽  
Finite Distance ◽  
The Mean ◽  
Coaxial Injector

Abstract An experimental study is carried out to analyze the effects of swirl on the structure and stabilization of methane non-premixed oxygen-enriched flames above a coaxial injector in which the two streams are eventually swirled. The mean position of the flame and the liftoff height above the injector lips are investigated with OH* chemiluminescence images. The oxygen enrichment, the momentum flux ratio between the two coflows, the swirl level inside the central jet, and the swirl level in the annular jet are varied over a large range of operating conditions. It is found that, in the absence of swirl in the central stream, the flame is always attached to the lips of the internal injection tube. As the inner swirl level increases, the flame front located at the lips of the internal injection tube disappears. When the annular swirl level is high enough to create a central recirculating bubble, the flame detaches from the nozzle rim and remains lifted at a finite distance above the injector. Increasing the oxygen concentration shifts this transition to smaller momentum flux ratios and smaller annular swirl levels. The liftoff distance can be finely tuned and depends on the inner and outer swirl levels, and on the momentum flux ratio between the two coaxial streams. It is shown that this feature depends neither on the confinement of the injector nor on the thermal stress exerted by the hot burnt gases on the injector back plane. About 1000 configurations were investigated that could be classified into only four distinct stabilization modes, in which the flame structure was shown to follow a similar pathway when the momentum flux ratio between the two streams, the swirl level in the central and external streams, and the quarl angle of the annular stream are varied. It is finally shown how these limits are altered when the oxygen concentration in the annular oxidizer stream is varied from air to oxygen-enriched operation.

scholarly journals Effects of Swirl on the Stabilization of Non-Premixed Oxygen Enriched Flames Above Coaxial Injectors

2019 ◽  
Author(s):  
A. Degeneve ◽  
C. Mirat ◽  
J. Caudal ◽  
R. Vicquelin ◽  
T. Schuller
Keyword(s):  
Oxygen Concentration ◽  
Momentum Flux ◽  
Flame Structure ◽  
Flux Ratio ◽  
Operating Conditions ◽  
Momentum Flux Ratio ◽  
Annular Jet ◽  
Finite Distance ◽  
The Mean ◽  
Lift Off

Abstract An experimental study is carried out to analyze effects of swirl on the structure and stabilization of methane non-premixed oxygen-enriched flames above a co-axial injector in which the two streams are eventually swirled. The mean position of the flame and the liftoff height above the injector lips are investigated with OH* chemiluminescence images. The oxygen enrichement, the momentum flux ratio between the two co-flows, the swirl level inside the central jet and the swirl level in the annular jet are varied over a large range of operating conditions. It is found that, in the absence of swirl in the central stream, the flame is always attached to the lips of the internal injection tube. As the inner swirl level increases, the flame front located at the lips of the internal injection tube disappears. When the annular swirl level is high enough to create a central recirculating bubble, the flame detaches from the nozzle rim and remains lifted at a finite distance above the injector. Increasing the oxygen concentration shifts this transition to smaller momentum flux ratios and smaller annular swirl levels. The lift-off distance can be finely tuned and depends on the inner and outer swirl levels, and on the momentum flux ratio between the two coaxial streams. It is shown that this feature neither depends on the confinement of the injector nor on the thermal stress exerted by the hot burnt gases on the injector back plane. About 1000 configurations were investigated that could be classified into only four distinct stabilization modes, in which the flame structure was shown to follow a similar pathway when the momentum flux ratio between the two streams, the swirl level in the central and external streams and the quarl angle of the annular stream are varied. It is finally shown how these limits are altered when the oxygen concentration in the annular oxidizer stream is varied from air to oxygen-enriched operation.

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