Internal crossflow effects on turbine airfoil film cooling adiabatic effectiveness with compound angle round holes

textInternal crossflow is an important element to actual gas turbine blade cooling; however, there are very few studies in open literature that have documented its effects on turbine blade film cooling. Experiments measuring adiabatic effectiveness were conducted to investigate the effects of perpendicular crossflow on a row of 45 degree compound angle, cylindrical film cooling holes. Tests included a standard plenum condition, a baseline crossflow case consisting of a smooth-walled channel, and various crossflow configurations with ribs. The ribs were angled to the direction of prevailing internal crossflow at 45 and 135 degrees and were positioned at different locations. Experiments were conducted at a density ratio of DR=1.5 for a range of blowing ratios including M=0.5, 0.75, 1.0, 1.5, and 2.0. Results showed that internal crossflow can significantly influence adiabatic effectiveness when compared to the standard plenum condition. The implementation of ribs generally decreased the adiabatic effectiveness when compared to the smooth-walled crossflow case. The highest adiabatic effectiveness measurements were recorded for the smooth-walled case in which crossflow was directed against the spanwise hole orientation angle. Tests indicated that the direction of perpendicular crossflow in relation to the hole orientation can significantly influence the adiabatic effectiveness. Among the rib crossflow tests, rib configurations that directed the coolant forward in the direction of the mainstream resulted in higher adiabatic effectiveness measurements. However, no other parameters could consistently be identified correlating to increased film cooling performance. It is likely that a combination of factors are responsible for influencing performance, including internal local pressure caused by the ribs, the internal channel flow field, jet exit velocity profiles, and in-hole vortices.Mechanical Engineerin

Gaseous reactions in heteroporous media

A modified dusty-gas model which accounts for the effects the pore-size and tortuosity distributions have on the mass fluxes in heteroporous media is presented. The behavior of the dusty-gas model (homoporous model) can be obtained from the modified model when the pressure is either very low or very high as well as for intermediate pressures when the characteristic parameter of the introduced tortuosity function has a very small value. When the pressure is very high or very low, all pores in the porous medium are almost in a single transport regime of either molecular or Knudsen diffusion. Comparisons of the mass fluxes predicted by the two models for binary isobaric diffusion, simultaneous diffusion and flow, and for chemical reactions with mole changes in heteroporous media show that the percentage deviations between the mass fluxes and the effectiveness factors calculated by the dusty-gas and the modified dusty-gas models can be significant. An analysis of the results indicates that the dusty-gas model could fail in predicting accurately the mass fluxes and effectiveness factors in porous systems with wide pore-size distributions, and it is suggested that the modified dusty-gas model, which incorporates the pore-size and tortuosity distributions in its constitutive equations, should be appropriate for use in the design and prediction of the performance of separation and reaction systems involving porous media required to operate in the transition transport regime --Abstract, page iii

The observed chaotic rotation of Hyperion

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1989.Includes bibliographical references (leaves 65-68).by James Jay Klavetter.Sc.D

Alloy-type and conversion-type anode materials for enhanced performance as lithium ion battery anode materials

Charge storage in the contemporary lithium-ion battery is at an energy density too low to support the function of long-range electric vehicles and other electronically powered technologies. To obtain up to two times or greater higher energy density than what is available by intercalation of lithium ions into graphite, the prevalent anode material in commercial batteries, materials with a higher storage density of lithium may be used, including materials that alloy with lithium or undergo a reversible conversion reaction to form lithium oxide. In this work, several such materials are considered – Ge, SnO2, Co3O4, and Ge0.1Se0.9 – and focus is directed to first demonstrating significantly enhanced cycling stability and capacity retention at variable charge/discharge rates and, second, to explaining the electrochemical performance in terms of key physical and chemical properties. Particular attention is given to assessing the formation of the solid electrolyte interphase (SEI) formed upon the anode material during charge/discharge cycling by means of microscopy and chemical characterization.Chemical Engineerin

Rotation of an oblate satellite: Chaos control

Aims. This paper investigates the chaotic rotation of an oblate satellite in the context of chaos control. Methods. A model of planar oscillations, described with the Beletskii equation, was investigated. The Hamiltonian formalism was utilized to employ a control method for suppressing chaos. Results. An additive control term, which is an order of magnitude smaller than the potential, is constructed. This allows not only for significantly diminished diffusion of the trajectory in the phase space, but turns the purely chaotic motion into strictly periodic motion.Comment: 9 pages, 4 figures; accepted in A&

Serologic Survey for Canine Infectious Diseases among Sympatric Swift Foxes (Vulpes velox) and Coyotes (Canis latrans) in Southeastern Colorado

Swift foxes (\\u27IL~VPGCY~ OX)a nd CoVi I otes (C~rrisl r~tr(~r~a.rse) sympatric canids distributed througllout rnany regions of tlie Great Plains of North America. ~h~ prevalence of canid diseases arnong these two species where they occur syiripatrically is presently unknown. Frorn January 1997 to January 2001, we collected blood salnples from 89 switt toxes and 122 coyotes oil the US Arlny Pifion Canyon Maneuver Site, 1,as Anilrlas County, SE lorado (USA). Seroprcvalence of ailtibodies against canine parvovirr~s (C13\i) was 71 % for adult (\u3e9 nlo old) ailcl 38% for jrlveilile (59 Ino old) swift fbxes. Adult (21 yr old) and juvenile (old) coyotes had a scroprevalence fo

Nonlinear time-series analysis of Hyperion's lightcurves

Hyperion is a satellite of Saturn that was predicted to remain in a chaotic rotational state. This was confirmed to some extent by Voyager 2 and Cassini series of images and some ground-based photometric observations. The aim of this aticle is to explore conditions for potential observations to meet in order to estimate a maximal Lyapunov Exponent (mLE), which being positive is an indicator of chaos and allows to characterise it quantitatively. Lightcurves existing in literature as well as numerical simulations are examined using standard tools of theory of chaos. It is found that existing datasets are too short and undersampled to detect a positive mLE, although its presence is not rejected. Analysis of simulated lightcurves leads to an assertion that observations from one site should be performed over a year-long period to detect a positive mLE, if present, in a reliable way. Another approach would be to use 2---3 telescopes spread over the world to have observations distributed more uniformly. This may be achieved without disrupting other observational projects being conducted. The necessity of time-series to be stationary is highly stressed.Comment: 34 pages, 12 figures, 4 tables; v2 after referee report; matches the version accepted in Astrophysics and Space Scienc

Signature of chaos in gravitational waves from a spinning particle

A spinning test particle around a Schwarzschild black hole shows a chaotic behavior, if its spin is larger than a critical value. We discuss whether or not some peculiar signature of chaos appears in the gravitational waves emitted from such a system. Calculating the emitted gravitational waves by use of the quadrupole formula, we find that the energy emission rate of gravitational waves for a chaotic orbit is about 10 times larger than that for a circular orbit, but the same enhancement is also obtained by a regular "elliptic" orbit. A chaotic motion is not always enhance the energy emission rate maximally. As for the energy spectra of the gravitational waves, we find some characteristic feature for a chaotic orbit. It may tell us how to find out a chaotic behavior of the system. Such a peculiar behavior, if it will be found, may also provide us some additional informations to determine parameters of a system such as a spin.Comment: 14 pages, LaTeX, to appear in Phys. Rev.