Liquid atomization by coaxial rocket injectors

Sankar, Subra; Rosa, Augusto; Isakovic, A. F.; Bachalo, W. D.

doi:10.2514/6.1991-691

Cited by 11 publications

(2 citation statements)

References 1 publication

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“…The large droplets at the edge of the spray moved faster than the air, since they could not follow the air flow and maintained their upstream velocity while the air flow decelerated. The relative velocity between large droplets and air indicates the possibility of secondary atomization and this im portant information was absent in the measurements of the time-average droplet velocity independent of droplet size of Sankar et al (1991Sankar et al ( , 1992 and Zaller & Klem (1991). The local Weber number, based on the Sauter mean diameter and relative velocity, was around unity and lower than the critical value, so th at the droplet size was measured in a region of the spray where breakup did not occur and most of the droplets can be expected to be spherical, as required by the sizing principle of the phase Doppler anemometry.…”

Section: R E Su Ltsmentioning

confidence: 99%

Breakup phenomena in coaxial airblast atomizers

Engelbert

Hardalupas

Whitelaw

1995

Proc. R. Soc. Lond. A

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The breakup of a liquid jet with length-to-diameter ratio of 22 surrounded by a coaxial flow of air has been examined by a combination of high-speed photography and phase-Doppler velocimetry. The air-to-liquid momentum and kinetic energy ratios, the Reynolds number of the coaxial water and air jet flows and the exit-plane Weber number have been varied over extensive ranges and the results examined in terms of the breakup length, frequency, droplet size distributions and velocity characteristics. The photographs reveal the deterministic nature of the liquid flow at Reynolds numbers which are sufficient to guarantee turbulent flow, with the formation of a wave-like structure for a short distance followed by the formation of a liquid cluster and subsequent breakup into ligaments and droplets, with the entire process repeated in a periodic manner. Attempts are made to relate the breakup length and the frequency of the process to the air-to-liquid momentum and energy ratios, the exit Weber number and the slip velocity between the two streams at the nozzle exit. The results confirm that the ratio of the frequencies of the wave-like structures and breakup decreased with the slip velocity between the two streams and asymptotically approached a value of around one for values higher than 150 m s -1 . The photographs indicate that the droplet sizes in the sprays are due mainly to disintegration of liquid clusters produced after the initial breakup of the liquid jet and the phase Doppler measurements confirm that most of the liquid remained close to the centreline, where the mean diameter reached a maximum and the slip velocity between the droplets and the air flow was low. An atomization model based on the value of the local Weber number on the centreline of the sprays is used to explain the size characteristics of the sprays. The atomization process was affected by the air-to-liquid momentum ratio at the nozzle exit, the annular width of the coaxial atomizer, the liquid-to-air density ratio, the surface tension and the kinematic viscosity and density of the air. The rate of spread of the sprays close to the nozzle reduced with increase of the air and liquid flowrates and was affected by the initial breakup of the liquid jet and the amplitude of the wave-like structure of the liquid jet during breakup rather than by the air flow turbulence.

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Section: R E Su Ltsmentioning

confidence: 99%

Breakup phenomena in coaxial airblast atomizers

Engelbert

Hardalupas

Whitelaw

1995

Proc. R. Soc. Lond. A

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“…The reported number densities, however, are far less than those being considered in the present study. Sankar et al [2] have used a PDPA in a shear coaxial rocket injector spray similar to the type of injector used in the present study. Peak number densities of about 2xl0 4 cm" 3 were measured.…”

Section: Introductionmentioning

confidence: 99%

Phase Doppler Measurements in Dense Sprays

Strakey¹,

Talley²,

Bachalo³

1998

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY) 13-03-19982. REPORT TYPE Paper DATES COVERED (From -To) TITLE AND SUBTITLE Phase Doppler Measurements in Dense Sprays SPONSOR/MONITOR'S ACRONYM (S) SPONSOR/MONITOR'S NUMBER(S) AFRL-PR-ED-TP-1998-060 DISTRIBUTION / AVAILABILITY STATEMENTApproved for public release; distribution unlimited. SUPPLEMENTARY NOTES AbstractMeasurements of droplet size, velocity and volume flux have been made in a dense spray using phase Doppler interferometry. Volume flux measurements have shown significant improvement over conventional phase Doppler techniques through the use of a flow splitter which provided the probe beams and scattered light signals access to the dense core of the spray. Also, the beam waist diameter was made much smaller than the droplets being measured in order to reduce multiple particle occurrences within the probe volume. The volume flux measurements were very encouraging when compared to measurements made with a mechanical patternator.

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