1,687 research outputs found
Nonlinear Unsteady Motions and NOx Production in Gas Turbine Combustors
Chiefly for improved efficiency, the trend to increasing use of gas turbine engines in stationary
powerplants has been firmly established. The requirement for minimum NOx production has motivated
operation as close as practically possible near the lean flammability limit, to reduce flame temperatures and
consequently reduce formation of nitrogen oxides via the Zeldovich thermal mechanism. However,
experience has shown that under these conditions, stability of the chamber is compromised, often leading
to the presence of sustained oscillations in the combustor. That possibility raises the problem of the
influence of oscillatory motions on the production of nitrogen oxides. Numerically calculating these
influences for a complex geometry gas turbine combustor is too computationally expensive at this ?me.
Nonlinear analytical methods making use of these influences are a promising direction for simplei ways to
design and develop operational gas turbine combustors. However, this analysis needs results on which to
base unsteady models of the interaction between nonlinear oscillations and species production within a gas
turbine combustor. In this paper, two methods are explored briefly as an initial step. The first is based on
a configuration of perfectly stirred and plug flow reactors to approximate the flow in a combustion
chamber. A complete representation of the chemical processes is accommodated, but the geometry is
simplified. The second is a full numerical simulation for a realistic geometry, but at this stage the
chemistry is simplified
Laboratory investigation of visible shuttle glow mechanisms
Laboratory experiments designed to uncover mechanistic information about the spectral and spatial characteristics of shuttle glow were conducted. The luminescence was created when a pulse of O atoms traveling at orbital velocities was directed toward NO molecules previously adsorbed to aluminum, nickel, and Z306 Chemglaz (a common baffle black) coated surfaces held at various temperatures. Spectral and spatial measurements were made using a CCD imaging spectrometer. Corroborative spectral information was recorded in separate measurements using a scanning monochromator and gated photomultiplier arrangement. The e-folding distance at several temperatures was calculated from images of the surface glow using the photometrics image processing capability of the imaging spectrometer. The e-folding distance was not altered as a function of incoming O beam velocity. The results are presented and the observations provide direct evidence that the visible shuttle glow results from recombination of oxygen atoms and surface bound NO
Open-Ended Modeling Group Projects in Introductory Statics and Dynamics Courses
Traditionally, the types of problems that students see in their introductory statics and dynamics courses are well-structured textbook problems with a single solution [1]. These types of questions are often seen by students as being somewhat at-odds with the more ārealisticā challenges that they may face in their design or lab courses. Additionally, in the pandemic-necessitated paradigm of emergency online instruction, methods of assessment beyond traditional exams have become more emphasized, both as a way of keeping students engaged by giving the material relevance and of ensuring that the work that they present is their own when so many solutions are available online
Interaction of intermediate energy protons with light nuclei
Interaction of intermediate energy protons with light nucle
Randomized Trial of 3 Techniques of Perineal Skin Closure During SecondāDegree Perineal Laceration Repair
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151863/1/jmwh13020.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151863/2/jmwh13020_am.pd
A conceptual design study of the reusable reentry satellite
Experimentation leading to an understanding of life processes under reduced and extremely low gravitational forces will profoundly contribute to the success of future space missions involving humans. In addition to research on gravitational biology, research on the effects of cosmic radiation and the interruption and change of circadian rhythms on life systems is also of prime importance. Research in space, however, is currently viewed by biological scientists as an arena that is essential, yet largely inaccessible to them for their experimentation. To fulfill this need, a project and spacecraft system described as the Reusuable Reentry Satellite or Lifesat has been proposed by NASA
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Measurement and simulation of apertures on Z hohlraums
The authors have performed aperture measurements and simulations for vacuum hohlraums heated by wire array implosions. A low-Z plastic coating is often applied to the aperture to create a high ablation pressure which retards the expansion of the gold hohlraum wall. However, this interface is unstable and may be subjects to the development of highly nonlinear perturbations (jets) as a result of shocks converging near the edge of the aperture. These experiments have been simulated using Lagrangian and Eulerian radiation hydrodynamics codes
A distance learning university and its economic impact in a countryās peripheries: the case of Hellenic Open University
A versatile and compact capacitive dilatometer
We describe the design, construction, calibration, and operation of a
relatively simple differential capacitive dilatometer suitable for measurements
of thermal expansion and magnetostriction from 300 K to below 1 K with a
low-temperature resolution of about 0.05 angstroms. The design is characterized
by an open architecture permitting measurements on small samples with a variety
of shapes. Dilatometers of this design have operated successfully with a
commercial physical property measurement system, with several types of
cryogenic refrigeration systems, in vacuum, in helium exchange gas, and while
immersed in liquid helium (magnetostriction only) to temperatures of 30 mK and
in magnetic fields to 45 T.Comment: 8 pages, incorporating 6 figures, submitted to Rev. Sci. Instru
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