Preliminary Results on Coaxial Jet Sprean Angles and the Effects of Variable Phase Transverse Acoustic Fields

Leyva, Ivett A.; Talley, Douglas G.; Rodríguez, Juan Luis Rodríguez; Chehroudi, Bruce

doi:10.2514/6.2008-950

Cited by 20 publications

(20 citation statements)

References 10 publications

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“…The largest decrease in length of the dark core compared to the case with no acoustics was observed in this regime. These findings support previous experimental results that had shown similar behavior with one acoustic driver configuration 4,5 and preliminary data with two acoustic resonators 6 .…”

Section: Resultssupporting

confidence: 82%

“…In the present paper, however, the addition of a second acoustic driver allowed changes of the relative position of the acoustic field with respect to the fixed location of the coaxial jet injector. Preliminary results with this new setup at subcritical pressures were presented in Leyva et al 6 Consistent with previous studies 4,5 , it was found that the maximum changes in the dark-core length for subcritical pressures were statistically significant for MR=2.6 but not for MR=1. The present study extends the range of the MR's studied for subcritical conditions and introduces results for the (higher) near-critical pressures.…”

Section: Introductionsupporting

confidence: 76%

See 1 more Smart Citation

Effects of a Variable-Phase Transverse Acoustic Field on a Coaxial Injector at Subcritical and Near-Critical Conditions (Preprint)

Rodríguez¹,

Leyva²,

Talley³

et al. 2008

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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) SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S)Air Force Research Laboratory (AFMC) AFRL/RZS SPONSOR/MONITOR'S Pollux Drive NUMBER(S)Edwards AFB CA 93524-7048 AFRL-RZ-ED-TP-2008-081 DISTRIBUTION / AVAILABILITY STATEMENTApproved for public release; distribution unlimited (PA #08117A). SUPPLEMENTARY NOTESSubmitted for presentation at the 21 st ILASS-Americas Meeting, Orlando, FL, 18-21 May 2008. ABSTRACTAn experimental study that focuses on the effects of a variable transverse acoustic field on an N 2 shear coaxial jet is presented. The coaxial jet is exposed to different acoustic conditions by varying the phase between two acoustic sources. The main objective of this investigation is to analyze the effect of transverse acoustic forcing with variable phase on the magnitude of the inner-jet dark-core length. The coaxial jet is exposed to a subcritical and near-critical pressure environment. The measurements are performed on backlit images of the coaxial jet obtained with a high-speed camera. The momentum flux ratio of the outer to the inner jet is varied from 1 to 20 for subcritical conditions and from 0.6 to 5 for near-critical conditions. The resonant frequency of the system is approximately 3 kHz and the maximum pressure variation with respect to total pressure is 3%. It is found that at subcritical pressures the effects of these variable acoustic fields on the length of the dark core achieve a maximum for momentum flux ratios between 1 to 5. AbstractAn experimental study that focuses on the effects of a variable transverse acoustic field on an N 2 shear coaxial jet is presented. The coaxial jet is exposed to different acoustic conditions by varying the phase between two acoustic sources. The main objective of this investigation is to analyze the effect of transverse acoustic forcing with variable phase on the magnitude of the inner-jet dark-core length. The coaxial jet is exposed to a subcritical and near-critical pressure environment. The measurements are performed on backlit images of the coaxial jet obtained with a highspeed camera. The momentum...

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Section: Resultssupporting

confidence: 82%

Section: Introductionsupporting

confidence: 76%

Effects of a Variable-Phase Transverse Acoustic Field on a Coaxial Injector at Subcritical and Near-Critical Conditions (Preprint)

Rodríguez¹,

Leyva²,

Talley³

et al. 2008

Self Cite

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“…[11][12][13][14][15][16] who examine the single-species case, and by Mayer and Smith 17 who consider a stream of nitrogen injected at low temperature (high density) surrounded by a high velocity stream of moderate temperature helium. Quantitative measurement of species density are reported by Oschwald et al 18 for a coaxial nitrogen/hydrogen injection, using spontaneous Raman scattering.…”

Section: Introductionmentioning

confidence: 99%

Experiments and numerical simulation of mixing under supercritical conditions

et al. 2012

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Supercritical pressure conditions designate a situation where the working fluid pressure is above the critical point. Among these conditions, it is interesting to identify a transcritical range which corresponds to cases where the pressure is above the critical point, but the injection temperature is below the critical value. This situation is of special interest because it raises fundamental issues which have technological relevance in the analysis of flows in liquid rocket engines. This situation is here envisaged by analyzing the behavior of a nitrogen shear coaxial jet comprising an inner stream injected at temperatures close to the critical temperature and a coaxial flow at a higher temperature. Experiments are carried out both in the absence of external modulation and by imposing a large amplitude transverse acoustic field. Real gas large eddy simulations are performed for selected experiments. The combination of experiments and calculations is used to evaluate effects of injector geometry and operating parameters. Calculations retrieve what is observed experimentally when the momentum flux ratio of the outer to the inner stream \documentclass[12pt]{minimal}\begin{document}$J= (\rho _eu_e^2)/(\rho _iu_i^2)$\end{document}J=(ρeue2)/(ρiui2) is varied. Results exhibit the change in flow structure and the development of a recirculation region when this parameter exceeds a critical value. The instantaneous flow patterns for different momentum flux ratios are used in a second stage to characterize the dynamical behavior of the flow in terms of power spectral density of velocity and density fluctuations. Results obtained under acoustic modulation provide insight into mixing enhancement of coaxial streams with a view of its possible consequences in high frequency combustion instabilities. It is shown in particular that the presence of strong acoustic modulations notably reduces the high density jet core length, indicating an increased mixing efficiency. This behavior is more pronounced when the jet is placed at the location of maximum transverse velocity fluctuations.

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“…While in many practical systems involving liquid spray combustion the flame envelops the spray itself [21], the behavior of individual droplets is a necessary component of twophase models for the reactive spray [22,23]. Moreover, many flow and reactive processes associated with single droplet combustion are relevant to and consistent with those of reactive multiphase jets, especially for configurations found in LREs [4], including shear coaxial jets, which have been shown in the past to selfexcite combustion instabilities [24][25][26][27][28][29][30].…”

Section: Single Fuel Droplet As a Basic Model For Condensed Phase Commentioning

confidence: 94%

Acoustically Coupled Combustion of Liquid Fuel Droplets

Karagozian

2016

Applied Mechanics Reviews

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The dynamics of oscillatory flames is relevant to acoustically coupled combustion instabilities arising in many practical engineering systems. This paper reviews fundamental studies that pertain to the combustion of single liquid fuel droplets in an acoustically resonant environment. This flow field is not only an idealized model for the study of the fundamental interaction of reactive, evaporative, acoustic, and other transport-based timescales, but it may also be used to identify relevant phenomena in more complex or practical geometries that require a focus for future combustion control efforts. The nature of these phenomena is discussed in detail, in addition to their implications for broader issues associated with combustion instabilities.

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Preliminary Results on Coaxial Jet Sprean Angles and the Effects of Variable Phase Transverse Acoustic Fields

Cited by 20 publications

References 10 publications

Effects of a Variable-Phase Transverse Acoustic Field on a Coaxial Injector at Subcritical and Near-Critical Conditions (Preprint)

Effects of a Variable-Phase Transverse Acoustic Field on a Coaxial Injector at Subcritical and Near-Critical Conditions (Preprint)

Experiments and numerical simulation of mixing under supercritical conditions

Acoustically Coupled Combustion of Liquid Fuel Droplets

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