Asymmetric Transverse Acoustic Excitation of a Hollow Cone Spray Sheet With Air Swirl

2019 ◽  
Author(s):  
Rohit R. Bhattacharjee ◽  
Aravind I. Babu ◽  
Satyanarayanan R. Chakravarthy
Keyword(s):  
Cone Angle ◽  
Acoustic Excitation ◽  
Hollow Cone ◽  
Breakup Length ◽  
Swirl Angle ◽  
Transverse Acoustic ◽  
Spray Axis ◽  
Acoustic Forcing ◽  
Pressure Swirl ◽  
Hollow Cone Spray

Abstract The objective of this study was to experimentally observe the effects of externally perturbing a hollow cone spray sheet with acoustic excitation. These effects were quantified by measuring changes in the spray breakup length, swirl angle, and oscillatory behaviour of the sheet edge. We used a pressure swirl nozzle embedded into a swirler with 60° vane angles and a geometric swirl no. of SG = 0.981. Water was used to produce a hollow cone spray sheet and air was used as our swirler agent. For asymmetric forcing, only one side of the spray chamber was attached to a transverse duct (aligned perpendicular to the spray axis) along with two speakers. The duct harmonics were found to be 115 Hz, 204 Hz, and 313 Hz. Our experimental modes were also found to be comparable with results obtained numerically using the acoustic solver package from ANSYS. Our results show that for most cases the spray edges, cone angle, and breakup length responds to the acoustic forcing. While the cone angle increased with air swirl, for some cases without acoustic forcing the breakup length increased with air swirl.

scholarly journals Experimental Study of Spray Characteristics of Kerosene-Ethanol Blends from a Pressure-Swirl Nozzle

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Tao Zhang ◽  
Bo Dong ◽  
Xun Zhou ◽  
Linan Guan ◽  
Weizhong Li ◽  
...  
Keyword(s):  
Discharge Coefficient ◽  
Cone Angle ◽  
Injection Pressure ◽  
Spray Characteristics ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Breakup Length ◽  
Ethanol Blends ◽  
Pressure Swirl ◽  
Spray Velocity

Partial replacement of kerosene by ethanol in a gas turbine is regarded as a good way to improve the spray quality and reduce the fossil energy consumption. The present work is aimed at studying the spray characteristics of kerosene-ethanol blends discharging from a pressure-swirl nozzle. The spray cone angle, discharge coefficient, breakup length, and velocity distribution are obtained by particle image velocimetry, while droplet size is acquired by particle/droplet imaging analysis. Kerosene, E10 (10% ethanol, 90% kerosene), E20 (20% ethanol, 80% kerosene), and E30 (30% ethanol, 70% kerosene) have been considered under the injection pressure of 0.1–1 MPa. The results show that as injection pressure is increased, the discharge coefficient and breakup length decrease, while the spray cone angle, drop size, and spray velocity increase. Meanwhile, the drop size decreases and the spray velocity increases with ethanol concentration when the injection pressure is lower than 0.8 MPa. However, the spray characteristics are not affected obviously by the ethanol concentration when the injection pressure exceeds 0.8 MPa. A relation to breakup length for kerosene-ethanol blends is obtained. The findings demonstrate that the adding of ethanol into kerosene can promote atomization performance.

scholarly journals Spray Drop Size and Velocity Measurements in a Swirl-Stabilized Combustor

1991 ◽  
Author(s):  
B. Chehroudi ◽  
M. Ghaffarpour
Keyword(s):  
Drop Size ◽  
Cone Angle ◽  
Hollow Cone ◽  
Flow Rates ◽  
Fuel Droplets ◽  
Radial Profiles ◽  
Fuel Nozzle ◽  
Pass Through ◽  
Yellow Region ◽  
Hollow Cone Spray

A pressure-swirl fuel nozzle generating a hollow-cone spray with nominal cone angle of 30 degrees is used in a swirl-stabilized combustor. The combustor is circular in cross section with swirl plate and fuel nozzle axes aligned and coinciding with the axis of the chamber. Kerosene is injected upward inside the chamber from the fuel nozzle. Separate swirl and dilution air flows are uniformly distributed into the chamber that pass through the honey comb flow straighteners and screens. Calculated swirl number of 1.5 is generated with the design swirl plate exit air velocity of 30 degrees with respect to the chamber axis. Effects of swirl and dilution air flow rates on the shape and stability of the flame are investigated. Stable and classical liquid fuel sheet disintegration zone exists close to the nozzle with no visible light followed by a luminous blue region and a mixed blue/yellow region that subsequently turns into yellow for most of the part in the flame. A Phase Doppler Particle Analyzer (PDPA) is used to measure drop size, mean and rms axial velocity for two cases of with and without combustion at six different axial locations from the nozzle. For the no-combustion case all air and fuel flow rates were kept at the same values as the combusting spray condition. Results for mean axial drop velocity profiles indicate widening of the spray due to combustion while the magnitudes of the peak velocities are slightly increased. No measurements inside the hollow-cone spray are possible due to burning of fuel droplets. Drop turbulence decreases due to combination of increase in gas kinematic viscosity and elimination of small drops at high temperatures. Sauter Mean Diameter (SMD) radial profiles at all axial locations increase with combustion due to preferential burning of small drops.

Droplets Behavior of Hollow-Cone Spray in a Non-Condensable Environment

2002 ◽  
Author(s):  
Minoru Takahashi ◽  
Suizheng Qiu ◽  
Shin-Ichi Kitagawa
Keyword(s):  
Spherical Particles ◽  
Spray Angle ◽  
Dual Phase ◽  
Hollow Cone ◽  
Phase Doppler Anemometry ◽  
Breakup Length ◽  
Liquid Spray ◽  
Hollow Cone Spray

The characteristics of droplets in a water hollow-cone spray from nozzles 1.1 mm and 3.6 mm in diameter in an air environment have been investigated experimentally. The dual phase Doppler anemometry (PDA) system was used to measure the size and two velocity components of individual spherical particles. The liquid spray geometry, including spray breakup length and spray angle were also obtained experimentally. The mechanism and the influence of these parameters on a hollow cone spray flow were described.

Characteristics of Hollow Cone Swirl Spray at Various Nozzle Orifice Diameters

2012 ◽  
Vol 58 (2) ◽  
Author(s):  
A. Hussein ◽  
M. Hafiz ◽  
H. Rashid ◽  
A. Halim ◽  
W. Wisnoe ◽  
...  
Keyword(s):  
Discharge Coefficient ◽  
Cone Angle ◽  
Injection Pressure ◽  
Orifice Diameter ◽  
Hollow Cone ◽  
Spray Characteristics ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Nozzle Orifice ◽  
Breakup Length

An experimental work to investigate the swirl spray characteristics that emanates from hollow–cone and solid–cone spray simplex atomizers is presented. Main objective of the research is to investigate the spray characteristics, i.e. spray breakup length, discharge coefficient and spray cone angle at different nozzle orifice diameter and injection pressure. Discharge coefficient is almost uninfluenced by the operating Reynolds number. This test also reveals that both breakup length and spray cone angle increases as orifice diameter is increased. Higher injection pressure leads to shorter breakup length and wider spray cone angle.

Structure of a Hollow-Cone Spray With and Without Combustion

1992 ◽  
Author(s):  
B. Chehroudi ◽  
M. Ghaffarpour
Keyword(s):  
Cone Angle ◽  
Velocity Profiles ◽  
Axial Distance ◽  
Volume Flux ◽  
Hollow Cone ◽  
Flow Rates ◽  
Drop Velocity ◽  
Radial Profiles ◽  
Fuel Nozzle ◽  
Hollow Cone Spray

A hollow-cone spray with a nominal cone angle of 30 degrees from a pressure-swirl fuel atomizer was used in a swirl-stabilized combustor. The combustor is circular in cross section, with a swirl plate and fuel nozzle axis coinciding with the axes of the chamber. kerosene is injected upward inside the chamber from the fuel nozzle. Separate swirl and dilution air flows are distributed into the chamber that pass through honeycomb flow straighteners and screens. A calculated swirl number of 1.5 is generated with the design swirl plate exit air velocity of 30 degrees with respect to the chamber axis. Effects of swirl and dilution air flow rates on the shape and stability of the flame are investigated. A Phase Doppler Particle Analyzer (PDPA) is used to measure drop size, mean and rms values of axial drop velocity, fuel volume flux, drop velocity and size distributions, and size-classified drop velocity profiles for two cases of with and without combustion and at six different axial locations from the nozzle. For the no-combustion case all air and fuel flow rates were kept at the same values as the combusting spray condition. Results for mean axial drop velocity profiles indicate widening of the spray, with slight increase in the magnitudes of the peak drop velocities due to combustion. Root mean square (RMS) values of drop velocity fluctuations decrease due to a combination of increase in gas kinematic viscosity and elimination of small drops at high temperatures. Sauter mean diameter (SMD) radial profiles at all axial locations increase with combustion due to preferential burning of small drops. Fuel volume flux profiles indicate negligible drop vaporization and/or burning up to a distance of 25mm from the nozzle. Velocity number distributions at different radial points for without combustion at an axial distance of 55mm from the atomizer are symmetric in shape only close to the peak of the mean drop velocity and show a bimodal shape around the maximum mean drop axial velocity gradient. Corresponding number distributions for the combustion case are fairly symmetric and quite different in behavior at all radial positions. Size-classified drop velocity profiles are also plotted and discussed.

Effect of Azimuthal Velocity Fluctuation on Hollow Cone Spray

2017 ◽  
Author(s):  
Aravind I. Babu ◽  
Satya Chakravarthy
Keyword(s):  
Velocity Fluctuation ◽  
High Speed ◽  
Cone Angle ◽  
Azimuthal Velocity ◽  
Mean Flow ◽  
Hollow Cone ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Velocity Fluctuations ◽  
Hollow Cone Spray

This paper reports an experimental investigation on the effect of imposed azimuthal velocity fluctuation on the spray characteristics of a hollow cone spray produced from a pressure-swirl nozzle. This effect is inferred by performing experiments separately on 0° and 60° axial straight vane swirlers oriented concentric to the spray nozzle for the air-flow subjected to upstream acoustic forcing. The hollow cone spray is subjected to external excitation using a loudspeaker at two different frequencies and two amplitudes. These frequencies correspond to the resonant frequencies of the plenum. The 60° vane swirler, when subjected to acoustic excitation, produces axial and azimuthal velocity fluctuation downstream of the swirler, whereas the 0° swirler produces only axial velocity fluctuation downstream of the swirler. In both 60° and 0° swirlers, the downstream velocity fluctuation due to acoustic disturbances propagate at the speed of sound. In addition, the velocity fluctuations produced due to the excitation are convected by the mean flow. This results in a combined effect of velocity fluctuations at the swirler exit. The hollow cone spray responds more readily to excitation at low frequencies than higher frequencies. This is observed from the high-speed shadowgraph images. The high-speed shadowgraph images acquired are processed to extract spray cone angle. The phase averaged spray cone angle fluctuates for different phase angle within an acoustic cycle. The analysis of the high-speed shadowgraph images shows that the cone angle fluctuation amplitude is higher for the 0° swirler as compared to the 60° swirler. The variation of the liquid sheet thickness and breakup length due to excitation is captured using high-speed planar laser induced fluorescence. The study clearly demonstrates that azimuthal velocity fluctuation affects the spray formation process.

Studies on the Behavior of Droplets and the Air Flow in a Hollow-Cone Spray

1998 ◽  
Vol 120 (3) ◽  
pp. 586-592 ◽  
Author(s):  
Tatsuyuki Okamoto ◽  
Toshimi Takagi ◽  
Toshikazu Kaji ◽  
Katsunori Shimazaki ◽  
Kenji Nakanishi
Keyword(s):  
Equations Of Motion ◽  
Liquid Sheet ◽  
Experimental Result ◽  
Hollow Cone ◽  
Air Stream ◽  
Droplet Sizes ◽  
Swirl Atomizer ◽  
Pressure Swirl ◽  
Hollow Cone Spray

Experimental and numerical investigations are made on the behavior of droplets in a hollow-cone spray paying attention to the liquid sheet formed at the orifice of pressure-swirl atomizer. Simultaneous measurements of droplet sizes and velocities are made by phase-Doppler technique and numerical simulations are carried out based on the transient Eulerian equations for the gas and the Lagrangian equation for the droplets, taking account of the liquid sheet formed at the atomizer orifice. It is shown that the simulation gives good predictions by incorporating the existence of the liquid sheet. The predicted results indicate that the movement of the liquid sheet induces a strong air stream which acts as a strong side wind against the droplets immediately after breakup. This air stream selectively transports small droplets toward the central region and plays an essential role in the classification of droplets by size. Accordingly, the existence of the liquid sheet is significant for the characteristics of droplet dispersion and it should not be neglected in the prediction of hollow-cone spray flows. In addition, the shape of the liquid sheet is theoretically computed based on the simplified equations of motion. The comparison between the theoretical computation and the experimental result suggests that the surface tension of liquid is predominant in determining the shape of the liquid sheet.

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