Measurements in an Acoustically Driven Coaxial Jet Under Supercritical Conditions

Davis, Dustin W.; Chehroudi, Bruce; Afb, Edwards; Sorensen, Ira J.

doi:10.2514/6.2005-736

Cited by 10 publications

(21 citation statements)

References 12 publications

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“…An overview of the facility is shown in Figure 1. This facility has been extensively described in previous references 7,8 . The gaseous N2 used to supply the inner and outer jets, and to pressurize the chambers, is obtained from the main supply line to the lab.…”

Section: Methodsmentioning

confidence: 99%

“…Several series of experiments have previously been carried out at the present facility to study the effects of a transverse acoustic field on coaxial jets at sub-, near-, and supercritical conditions using N2 7,8 . In these studies, it was found that the jet's dark core length for an undisturbed jet decreases as the outer to inner momentum flux ratio (MR) and outer to inner velocity ratio (VR) increase.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Dark Core Analysis of Coaxial Injectors at Sub-, Near-, and Supercritical Conditions in a Transverse Acoustic Field

Leyva¹,

Chehroudi²,

Talley³

2007

43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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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/PRS SPONSOR/MONITOR'S Pollux Drive NUMBER(S)Edwards AFB CA 93524-7048 AFRL-PR-ED-TP-2007-164 14. ABSTRACT An experimental study on the effects of an externally-imposed transverse acoustic field in sub-, near-, and supercritical N2 coaxial jets is presented. Such fields and their interaction with the jets (i.e., breakup, mixing, etc.) is believed to play a critical role during combustion instabilities in liquid rocket engines. The shear coaxial injector used here is similar to those used in cryogenic liquid rockets. By using N2 as the working fluid, the chemistry effects on combsution instability are separated from the effects of a transverse acoustic field on coaxial jets. Furthermore, through this choice, ambiguities associated with compostion dependence on mixtures critical properties are eliminated. The acoustic oscillations are generated by a piezo-siren and have a frequency of ~3kHz. The pressures in the chamber range from 215-716 psia to span sub-, near-, and supercritical conditions. The outer to inner jet velocity ratio varies from ~1.2 to 23 and the momentum flux ratio varies from ~0.2 to 23. These ratios are mainly varied by changing the temperature and flow rates of the outer jet. At least 2000 backlit images were taken at 41kHz for each run. The main metric investigated is the length of the dark, or inner jet, core length. Both the axial length of the jet and the total, or curved, length are studied. A functional relation of the form A/MR n describes the behavior of the axial length with the exponent being 0.2 (A:20-25) for subcritical conditions and 0.5 (A:5-12) for near and supercritical conditions. These results agree with historical data. The standard deviation of the axial length, which due to the large number of data points is within 0.03% of the RMS of the jet lengths fluctuations, also decreases with velocity ratio, for sub-, near-, and supercritical conditions. For momentum flux ratios ~O(1) the axial and total length differences between ac...

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dark Core Analysis of Coaxial Injectors at Sub-, Near-, and Supercritical Conditions in a Transverse Acoustic Field

Leyva¹,

Chehroudi²,

Talley³

2007

43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

Self Cite

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“…As the most destructive instabilities in LREs involve transverse resonant modes of the thrust chamber, many experimental studies were performed on non-reacting [27][28][29][30][31][32][33][34][35] and reacting flows [36][37][38][39][40] submitted to transverse acoustic modulations. They showed a reduction of the jet length, indicating altered destabilization and mixing processes, a growth of the expansion angle and a flame oscillation following the acoustic field.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of a transcritical coaxial flame under a high-frequency transverse acoustic forcing: Influence of the modulation frequency on the flame response

Hakim

Schmitt

Ducruix

et al. 2015

Combustion and Flame

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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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Measurements in an Acoustically Driven Coaxial Jet Under Supercritical Conditions

Cited by 10 publications

References 12 publications

Dark Core Analysis of Coaxial Injectors at Sub-, Near-, and Supercritical Conditions in a Transverse Acoustic Field

Dark Core Analysis of Coaxial Injectors at Sub-, Near-, and Supercritical Conditions in a Transverse Acoustic Field

Dynamics of a transcritical coaxial flame under a high-frequency transverse acoustic forcing: Influence of the modulation frequency on the flame response

Experiments and numerical simulation of mixing under supercritical conditions

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