A small, Fast-Response Probe to Measure Composition of a Binary Gas Mixture

Brown, Geoffrey L.; Rebollo, Manuel Rebollo

doi:10.2514/3.50170

Cited by 88 publications

(34 citation statements)

References 4 publications

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“…the concentration of helium relative to the nitrogen). This probe, which is described by Brown & Rebollo (1972), has a response time of about 0.2 ms and samples a volume of a few thousandths of an inch in diameter. It is insensitive to velocity when the Mach number is small, as in our experiments.…”

Section: Results For Density Differencementioning

confidence: 99%

“…As a minimum, mean density and velocity profiles are required to establish the essential features of the mixing region. The instruments used to obtain these were a fast electronic (Barocel) manometer connected to a Pitot tube, to measure dynamic pressure, and a small, fast-response, density probe developed especially for this study and described in detail by Brown & Rebollo (1972).…”

Section: Apparatus and Measuring Techniquesmentioning

confidence: 99%

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On density effects and large structure in turbulent mixing layers

1974

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Plane turbulent mixing between two streams of different gases (especially nitrogen and helium) was studied in a novel apparatus. Spark shadow pictures showed that, for all ratios of densities in the two streams, the mixing layer is dominated by large coherent structures. High-speed movies showed that these convect at nearly constant speed, and increase their size and spacing discontinuously by amalgamation with neighbouring ones. The pictures and measurements of density fluctuations suggest that turbulent mixing and entrainment is a process of entanglement on the scale of the large structures; some statistical properties of the latter are used to obtain an estimate of entrainment rates. Large changes of the density ratio across the mixing layer were found to have a relatively small effect on the spreading angle; it is concluded that the strong effects, which are observed when one stream is supersonic, are due to compressibility effects, not density effects, as has been generally supposed.

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Section: Results For Density Differencementioning

confidence: 99%

Section: Apparatus and Measuring Techniquesmentioning

confidence: 99%

On density effects and large structure in turbulent mixing layers

1974

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“…For the irreversible reaction the total amount of mixed fluid within the sampling volume is proportional to the amount of product there, independent of the size of the sampling volume. Konrad (1976) used a concentration probe (see Brown & Rebollo 1972) to measure the mixing of a passive scalar. Breidenthal ( 1978Breidenthal ( , 1981 approximated the irreversible reaction with a reversible one using phenolphthalein and sodium hydroxide, i.e.…”

Section: Chemical-reaction Methodsmentioning

confidence: 99%

Mixing and combustion with low heat release in a turbulent shear layer

1984

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Turbulent mixing and combustion are investigated in a gaseous shear layer formed between two streams: one containing a low concentration of hydrogen in nitrogen and the other containing a low concentration of fluorine in nitrogen. The resulting temperature field is measured simultaneously at eight points across the width of the layer using fast-response cold-wire thermometry. The results show the presence of large, hot structures separated by tongues of cool fluid that enter the layer from either side. The usual bell-shaped mean-temperature profiles therefore result from a duty cycle whereby a fixed probe sees alternating hot and cool fluid, which results in the local mean. The adiabatic flame temperature is not achieved in the mean, at any location across the layer. For fixed velocities, it is found that, in general, two different mean-temperature profiles result from a given pair of reactant compositions if the sides of the layer on which they are carried are exchanged ('flipped'). This finding is a direct consequence of the asymmetric entrainment of fluid into the layer. Results are compared with the predictions of Konrad and discussed in the context of the Broadwell-Breidenthal model. By comparison with the liquid result of Breidenthal, the amount of product formed in the layer at high Reynolds number is found to be dependent upon the Schmidt number. Results for a helium-nitrogen layer are discussed briefly.

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“…5. They measure mixing layer spreading in a twodimensional arrangement by both shadowgraphy (called visible jet thickness) as well as through velocity profiles extracted from results of a concentration probe, see Brown and Rebollo [22], along with Pitot tube dynamic pressure measurements within the layer (called vorticity thickness as described in the Appendix). They make distinction between mixing layers in which density changes are caused by temperature changes, high-speed compressible (high Mach number and supersonic) flows, and differences in molecular weights (i.e., different gases).…”

Section: Jet Spreading Anglementioning

confidence: 99%

Initial Growth Rate and Visual Characteristics of a Round Jet into a Sub- to Supercritical Environment of Relevance to Rocket, Gas Turbine, and Diesel Engines

Chehroudi¹,

Talley²,

Coy³

1998

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Public reporting burden lor this eolation of information is estimated to average 1 hour per respo-se n-udrg ~e . ~e ■-• revewng instructions, searching existing datasources gathering and maintaining the data needed, and completing and reviewing this collection of information Send ccmme-fs recarcna tr s ouroen estimate or any other aspect of this collection of information including suggestions for reducing this burden to Department of Defense. Washington Headquarters Se vices Directorate tor Info-mation AbstractThe combustion chamber temperature and pressure in many liquid rocket, gas {urbin|, and diesel engines are quite high and can reach above the critical point *¥ the injected fuels and/or oxidizers. A high pressure chamber is used to investigate and understand the nature of the interaction between the injected fluid and the environment under such conditions. Pure N 2 , He, and 0 2 fluids are injected. Several chamber media are selected including, N 2 , He, and mixtures of CO+N 2 . The effects of chamber pressure ranging from a subcritical (i.e.*elative pressure, P r = P/Pinjeoantcridca! 1) value|"at a supercritical chamber temperature (i.e.^ relative temperature T r = TAr injectam critical >1) are photographically observed and documented near the injector hole exit region using a CCD camera illuminated by a shortduration back-lit strobe light. At low subcritical chamber pressures, the jets exhibit surface irregularities that amplify downstream, lookjggintact, shiny, but wavy (sinuous) on the surface mimS evenwglly break up into irregularly-shaped small entities./^urther increase of chamber pressure causes formation of many small droplets on the surface of the jet ejecting away only within a narrow region below the critical pressure of the injected fluid similar to a second wind-induced liquid jet breakup regime. Raising the chamber pressure, transition into a full atomization regime is inhibited by rejghing near, but slightly lower than, ^"critical pressure «fthe injectant where both surface tension and heat of vaporization are sufficiently reduced. The jet appearance changes abruptly at this point and remains the same «ter resemb}£a?turbulent gas jet injection. In this region, and within the imaging resolution limitation, no droplets are seen forming and/or departing from the jet. The jet initial total divergence angle, indicating initial growth or spreading rate, is extracted from a large set of images and plotted along with ^"available data on liquid fuel injection in £ diesel engine environment, turbulent incompressible, supersonic, and variable-density jets and for incompressible but variable-density turbulent mixing layers, thus quantitatively strengthening the gas-jet like appearance. Considering this agreement, the inhibition of Tfc*-transition to atomization regime and its confirmation through the examined atomization criteria, and the visual lack of any drop; the relevancy of current injection models and some drop vaporization/combustion results under conditions where...

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A small, Fast-Response Probe to Measure Composition of a Binary Gas Mixture

Cited by 88 publications

References 4 publications

On density effects and large structure in turbulent mixing layers

On density effects and large structure in turbulent mixing layers

Mixing and combustion with low heat release in a turbulent shear layer

Initial Growth Rate and Visual Characteristics of a Round Jet into a Sub- to Supercritical Environment of Relevance to Rocket, Gas Turbine, and Diesel Engines

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