Download or read book Behavior of a Round Cryogenic Jet at Below and Above the Critical Pressure written by and published by . This book was released on 1998 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In an effort to investigate and understand the behavior of the injected cryogenic fluid and its environment, a high pressure chamber is used into which pure N2 He, and O2 fluids are injected. Several chamber media are selected including, N2, Me, and mixtures of CO+N2. The effects of chamber pressure ranging from a subcritical to a supercritical values at a supercritical chamber are photographically observed and documented near the injector hole exit region using a CCD camera illuminated by a short-duration back-lit strobe light. At low subcritical chamber pressures, the jets exhibit small surface irregularities that amplify downstream, looking intact, shiny, but wavy on the surface which eventually break up into irregularly-shaped small entities. Further increase of chamber pressure aids 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 jet breakup - regime. Raising the chamber pressure, transition into a full atomization regime is inhibited by reaching near, but S slightly lower than, the critical pressure of the injectant where both surface tension and heat of vaporization are sufficiently reduced. The jet appearance changes abruptly at this point and remains the same to resemble a turbulent gas jet injection. The jet initial growth rate, is extracted from a large set of images and plotted with the available data on liquid fuel injection in diesel engine environment, turbulent incompressible, and variable density jets and mixing layers, creating a unique plot on its own. The jet spreading rate measurements agree well with a theoretical equation proposed for incompressible but variable density turbulent mixing layers by Papamoschou and Roshko 1 and follow the trend of that of Dimotakis.

Download or read book The Fractal Geometry of Round Turbulent Cryogenic Nitrogen Jets at Supercritical Pressures written by and published by . This book was released on 2002 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Box-counting and EDM methods were used to measure the fractal dimension of round turbulent cryogenic nitrogen jets at pressures ranging from subcritical to supercritical pressures. Both method produced similar trends, with close quantitative agreement for a suitably small box-counting scale. At subcritical pressures, the fractal dimension was found to be consistent with the fractal dimension of a spray in the 2nd wind-induced atomization regime. The fractal dimension tended to increase as pressure increased, until at supercritical pressures the fractal dimension was found to be consistent with that of gas jets and mixing layers. The results constitute additional quantitative evidence for the hypothesis that subcritical jets exhibit mainly spray-like behavior, while supercritical jets exhibit mainly gas-like behavior. This appears to have been the first time pressure effects on the fractal dimension of turbulent jets has been measured.

Download or read book The Behavior of Cryogenic Shear Layers Under Supercritical Conditions written by and published by . This book was released on 2001 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent experience gained at AFRL with the injection of cryogenic fluids into high back-pressures is summarized. In the experimental investigations described, a jet of a cryogenic fluid, typically liquid N2, is injected into a chamber whose ambient pressure is varied to values exceeding the critical pressure of the injectant. The structure of the jet and the shear layer between the jet and the ambient has been examined. Results from visualization, jet growth rate, fractal analysis, and Raman scattering measurements indicate that the behavior of the injected fluid changes from spray-like behavior to gas jet-like behavior as pressure increased.

Download or read book Visual Characteristics and Initial Growth Rates of Round Cryogenic Jets at Subcritical and Supercritical Pressures written by and published by . This book was released on 2001 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The visual characteristics and initial growth rates of round cryogenic jets injected into subcritical and supercritical pressures were studied. We found that the jet exhibits liquid-like and gas-like characteristics at subcritical and supercritical pressures, respectively. Explanations are offered. The jet spreading angle at supercritical pressures has been demonstrated to agree quantitatively with the theoretical spreading angle of incompressible but variable density turbulent gas jets, the first time more than a qualitative visual similarity with gas jets has ever been demonstrated. In addition, the present measurements of spreading rates have been plotted along with other measurements for subsonic incompressible constant density and variable density jets, liquid sprays, supersonic jets, and other mixing layers in a plot spanning four orders of magnitude in gas-to-liquid density ratio. This is the first time these results have been consolidated in a single plot over such a large range of density ratio.

Download or read book Fractal Geometry and Growth Rate Changes of Cryogenic Jets Near the Critical Point written by and published by . This book was released on 1999 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Injection of several pure fluids into a chamber with different ambient gases under supercritical temperature but sub- to supercritical condition based on the injectant thermodynamic critical conditions resulted in the following: the jet exhibits classical liquid-like jet second wind-induced type breakup until chamber pressure reaches near the critical point of the jet substance beyond which gas-like visual behavior is observed and no drops are found. For the first time, these visual qualitative observations are verified quantitatively by agreement between the experimental growth rate of the jets reported here and those developed theoretically by D. Brown, D. Papamoschou and A. and Roshko, and P.E. Dimotakis for the incompressible variable-density mixing layers. This gas-like jet appearance is also confirmed quantitatively and for the first time by fractal analysis of the outer contour of the jet. The geometry of the jet interface shows a transition from Euclidean to a fractal interface with a fractal dimension near the values measured and reported by others for gaseous turbulent jets. Finally, based on a physical hypothesis implying that at the point where gas-like behavior appears, the value of the jet interface bulge separation/formation characteristic time should be near that of gasification, an "intuitive/smart" equation is proposed for the growth rate that agrees well with the presented experimental data for a wide range of density ratios. (9 figures, 40 refs.).

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Download or read book Survey of Heat Transfer to Near critical Fluids written by Robert C. Hendricks and published by . This book was released on 1970 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Sustainable Machining written by J. Paulo Davim and published by Springer. This book was released on 2017-03-19 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides an overview on current sustainable machining. Its chapters cover the concept in economic, social and environmental dimensions. It provides the reader with proper ways to handle several pollutants produced during the machining process. The book is useful on both undergraduate and postgraduate levels and it is of interest to all those working with manufacturing and machining technology.

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