Characterization of coaxial rocket injector sprays under high pressure environments

Sankar, S. V.; Wang, G.; Rosa, Augusto; Rudoff, R. C.; Isakovic, A. F.; Bachalo, W. D.

doi:10.2514/6.1992-228

Cited by 10 publications

(4 citation statements)

References 4 publications

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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 photographs were imaged with the laser sheet and have been digitally reproduced from color photographs to improve image quality for photoduplication and to accentuate noticeable structures within the spray. As a consequence, larger droplets pervade the spray of a nonevaporating liquid at higher chamber pressures, 56 although shorter liquid breakup lengths may also be present. Regions of droplet flow are most evident downstream of the liquid structures, whereas very little droplet production is observed along the liquid column close to the injector exit.…”

Section: B Photographic Studies Using Cryogenic Fluids (Liquid/gaseomentioning

confidence: 99%

Atomization in Coaxial-Jet Injectors

2004

Liquid Rocket Thrust Chambers

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Nomenclature a = radius of atomizer C -model constant d = liquid nozzle diameter di = drop diameter Z) 0 = initial diameter of vaporizing drop DIQ -arithmetic mean diameter h -thickness of annular air nozzle L R = length of recess L = length of combustor Mf -mixture ratio M r = momentum flux ratio n -number of droplets produced per unit time NI = number of droplets PI -pressure of liquid upstream in injector Downloaded by PURDUE UNIVERSITY on July 25, 2015 | http://arc.aiaa.org | Downloaded by PURDUE UNIVERSITY on July 25, 2015 | http://arc.aiaa.org |

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“…The momentum ratio is very important due to the fact that it can be used to compare fluids of densities and velocities. Sankar et al 10 and Glogowski et al 11 concluded that increasing the gas velocity helped to improve the breakup process.…”

Section: Introductionmentioning

confidence: 99%

Atomization and Combustion Characteristics of Ethanol/Nitrous Oxide at Various Momentum Flux Ratios

2014

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The flame structure of ethanol and nitrous oxide combustion was experimentally studied using a tricoaxial injector at various momentum flux ratios. The objects of the study were to investigate the effects of the additional supplement of nitrous oxide that gas jets inject at the outer annular gap at various injection velocities and to obtain and analyze the flame structure. The fully developed patterns due to the transfer of momentum and viscosity mixing were similar to that of the axial flow when the measurement position was increased from Z/d = 1 to Z/d = 10. The correlation equation, using the momentum flux ratio, was used along with the linear regression method to calculate the breakup length and Sauter mean diameter (SMD). The effects were clearly observed and significant. The inner gas injection caused the SMD to decrease, and the outer gas injection was able to create a boundary layer around the spray jets. As the momentum flux ratio of the inner gas jets increased, the spray angle and flame angle increased. OH radicals extended toward the rear flame region with the increase in momentum flux ratio from the inner gas jets. As the momentum flux of the outer gas jets increased, the boundary of the OH radicals developed and the intensity of the OH radicals generated in the flame region was enhanced. Also, the flame temperature increased as gas was injected from the outer-stage.

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Characterization of coaxial rocket injector sprays under high pressure environments

Cited by 10 publications

References 4 publications

Breakup phenomena in coaxial airblast atomizers

Breakup phenomena in coaxial airblast atomizers

Atomization in Coaxial-Jet Injectors

Atomization and Combustion Characteristics of Ethanol/Nitrous Oxide at Various Momentum Flux Ratios

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