Measurements and Predictions of a Liquid Spray From an Air-Assist Nozzle

Bulzan, Daniel L.; Levy, Y.; Chitre, S.

doi:10.1615/atomizspr.v2.i4.50

Cited by 16 publications

(15 citation statements)

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“…The percent deceleration of the atomizing nitrogen gas is assumed to be approximately the same in both cases, since the two-fluid nozzles used in Ref. 13 and the present study were very similar in design.…”

Section: Acceleration Of Ln 2 Dropletsmentioning

confidence: 98%

Atomizing-gas temperature effect on cryogenic spray dropsize

Ingebo

1993

29th Joint Propulsion Conference and Exhibit

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Correlating expressions for two-phase flow breakup of liquid nitrogen, LN 21 jets in sonic velocity nitrogen gasflows were obtained for an atomizing-gas temperature range of 111 to 442 K. The correlations were based on characteristic dropsize measurements obtained with a scattered-light scanner. The effect of droplet vaporization on the measurements of the volume-median dropsize, Dv 5 , was calculated by using previously determined heat and momentum transfer expressions for droplets evaporating in high-velocity gasflow. Finally, the dropsize of the originally unvaporized spray, D v 5c , was calculated, normalized with respect to jet diameter, Do, and correlated with atomizing-gas flowrate and temperature, according to the following expression:

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Section: Acceleration Of Ln 2 Dropletsmentioning

confidence: 98%

Atomizing-gas temperature effect on cryogenic spray dropsize

Ingebo

1993

29th Joint Propulsion Conference and Exhibit

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“…Subsequent values of gas velocity, V., were calculated from data given b in Ref. 15 and plotted over a distance of 3 cm downstream of the fuel-nozzle orifice, as shown in Fig. 5.…”

Section: Simultaneous Vaporization and Acceleration Of D_mentioning

confidence: 99%

Cryogenic and simulated fuel jet breakup in argon, helium and nitrogen gas flows

Ingebo¹

1995

31st Joint Propulsion Conference and Exhibit

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Two-phase flow atomization of liquid nitrogen jets was experimentally investigated. They were co-axially injected into high-velocity gas flows of helium, nitrogen and argon, respectively, and atomized internally inside a two-fluid fuel nozzle. Cryogenic sprays with relatively high specific surface areas were produced, i.e., ratios of surface area to volume were fairly high. This was indicated by values of reciprocal Sauter mean diameters, RSMD's, as measured with a scattered-light scanning instrument developed at NASA Lewis Research Center. Correlating expressions were derived for the three atomizing gases over a gas temperature range of 111 to 422 K. Also, the correlation was extended to include water-jet breakup data that had been previously obtained in simulating fuel jet breakup in sonic velocity gasflow. The final correlating expression included a new dimensionless molecular-scale acceleration group. It was needed to correlate RSMD data, for LN 2 and HO sprays, with the fluid properties of the liquid jets and atomizing gases used in this investigation. Re Reynolds number, based on D32 or Dv.5 To ambient airflow temperature, 293 K t vaporization time, sec V fluid velocity, cm/sec

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“…These nozzles were chosen because of their well-known correlation between inlet air and water pressures and resulting droplet sizes produced. The nozzles were also desirable because of the extensive work done in the past by Bulzan et al 29 to both numerically and experimentally validate the nozzles radial and axial profiles of velocity and turbulent kinetic energy.…”

Section: Spray Test Setupmentioning

confidence: 99%

“…The air and water mass flow rates were approximately 2.3 and 0.5 g /s, respectively. 29 For three different test runs, the nozzle was placed at distances of 25, 45, and 65 cm from the superhydrophobic sample.…”

Section: Spray Test Setupmentioning

confidence: 99%

Superhydrophobic Surfaces to Resist Droplet Sprays, Simulated Rain, and Water Jets

Davis¹

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With anti-wetting properties such as contact angles greater than 150• and sliding angles less than 10• , low-cost superhydrophobic coatings hold great promise in reducing fouling and icing. However, these coatings must also resist saturation and erosion caused by water droplet impact. The first experimental study investigates the performance of a polyurethane/organoclay superhydrophobic nanocomposite modified with perfluoroalkyl methacrylic copolymer (PMC) in the presence of a high pressure air-water spray which simulates an icing cloud impact. Superhydrophobic samples were exposed at 25, 45, and 65 cm from the spray nozzle. The velocites of droplets impacting the superhydrophobic samples were estimated computationaly for each of these distances to be 14.5, 4.5, and 3.4 m /s, respectively. It was found that liquid saturation did not occur immediately, but over time, the high mass flow rate of water led to anti-wetting performance degradation. Upon evaporation through heating, contact angle returned to pre-test values, indicating little mechanical erosion. This was consistent with scanning electron microscopy (SEM) which showed that the nano-and micro-structure was preserved, as well as with energy-dispersive X-ray spectroscopy (EDXS), which showed no surface chemistry change after testing. However, sliding angle showed stronger degradation, especially at higher impact velocities.The objective of the second study was to test the mechanical durability of a polyurethane/organoclay/PMC nanocomposite coating in conditions that replicate extended rain impact. Samples were impacted with 1.4 mm droplets at a velocity of 25 m /s and a flow rate of 0.78 gpm for a period of 5 hours by an axial full cone nozzle. The cases of normal and angled 40• droplet impact were examined. After the spray period, samples were heated at 100• C to allow saturated liquid to evaporate from the surface.Contact angle and sliding angle of the superhydrophobic surfaces were measured before and after the spray period. A decrease in performance for both samples was observed, with the vertically sprayed sample showing greater degradation. After iv refunctionalizing the vertically sprayed surface with PMC, an increase in performance was observed. Microscopy of the superhydrophobic samples before and after spray impact revealed a change in surface morphology which, along with leaching of the fluoroacrylic copolymer, was the likely cause of the decrease in performance.In the third study, a novel superhydrophobic surface composed of a PTFE binder and flame-generated carbonaceous soot was created. Importantly, unlike previous surfaces created from flame-generated material, the produced surface showed good adhesive properties. Owing to the natural hydrophobicity of carbon and nanostructure of the deposited soot, surfaces displayed extreme resistance to saturation by an impinging high pressure water jet. Surfaces were found to saturate more easily as they were tilted to the impinging water jet. However, the anti-wetting properties of samples that ...

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Measurements and Predictions of a Liquid Spray From an Air-Assist Nozzle

Abstract: Unclassified 20. Security Classif.

Cited by 16 publications

References 0 publications

Atomizing-gas temperature effect on cryogenic spray dropsize

Atomizing-gas temperature effect on cryogenic spray dropsize

Cryogenic and simulated fuel jet breakup in argon, helium and nitrogen gas flows

Superhydrophobic Surfaces to Resist Droplet Sprays, Simulated Rain, and Water Jets

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