Begell House Inc.
Atomization and Sprays
AAS
1044-5110
14
1
2004
ATOMIZATION AND EMISSION GAS CHARACTERISTICS OF RESIDUAL OILS/WATER MIXTURES IN A SMALL FURNACE WITH A TWIN-FLUID ATOMIZER
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10.1615/AtomizSpr.v14.i1.10
Kunihiko
Namba
Department of Mechanical Engineering, Osaka Prefectural College of Technology, Osaka, Japan
Kyoji
Kimoto
Department of Mechanical Engineering, Osaka Prefectural College of Technology, Osaka, Japan
Residual water mixture (RWM) is a fuel of an "oil-in-water" emulsion with a water content of about 30% (by weight) to the final residual oils such as asphalt and pitch after distilling crude oils. The fuel shows two orders of magnitude lower viscosity than the neat residual oils because of water content included in the emulsion, so it can be used in a pump to supply fuel to a burner. In this article, the atomization characteristics of the sprays of a twin-fluid atomizer and, in particular, NOx emission characteristics in the flue gases in a small furnace, are discussed for asphalt/water (As/W) emulsions, one of the RWM fuels, in combustion experiments. It is concluded that As/W fuels can be expected to be used as substitute fuels for C heavy oil because of improved combustive quality of residual oils and nearly equivalent NOx emissions to C heavy oil. The result is based on dispersed flames induced by the secondary atomization due to the microexplosion effect of the fuel droplets.
SPRAY DISPERSION IN A COUNTER-SWIRLING DOUBLE-ANNULAR AIR FLOW AT GAS TURBINE CONDITIONS
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10.1615/AtomizSpr.v14.i1.20
Julian
Becker
DLR—German Aerospace Center, Institute of Propulsion Technology, Cologne, Germany
Daniel
Heitz
DLR—German Aerospace Center, Institute of Propulsion Technology, Linder Hohe, 51147 Cologne, Germany
Christoph
Hassa
German Aerospace Center−DLR, Institute of Propulsion Technology, Linder Hohe, 51147 Cologne, Germany
The dispersion of a kerosene fuel spray generated by plain-jet-in-crossflow injection into the inner annulus of a counter-swirling double-annular air flow was investigated experimentally. Tests were conducted at 6 bar and 12 bar static air pressure and 750 K air temperature and at the corresponding cold test conditions in terms of air density, with an additional excursion to higher air density (9.3 bar at 290 K). The air flow was characterized by laser Doppler anemometry (LDA) and the spray dispersion was investigated by phase Doppler anemometry (PDA). It was found that the very small droplets generated at high pressure have such a great ability to follow the streamlines of the air flow that they remain trapped in the inner annulus, preventing the formation of a uniform fuel–air mixture in the annular flow. For an in-depth discussion of the results, the appropriate versions of the Stokes number are introduced and evaluated.
SIMULATION OF CAVITATED FLOW IN ORIFICES FED BY A MANIFOLD
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10.1615/AtomizSpr.v14.i1.30
Changhai
Xu
School of Aeronautics and Astronautics, Purdue University, West Lafayette, Indiana, USA
Stephen D.
Heister
Maurice J. Zucrow Laboratories, Department of Aeronautics and Astronautics, Purdue University, West Lafayette, Indiana, USA
Gregory A.
Blaisdell
School of Aeronautics and Astronautics, Purdue University, West Lafayette, Indiana, USA
Simulations of three-dimensional cavitating flows for an orifice fed by a manifold are performed using a homogeneous flow model. The dynamics of a bubble response per the Rayleigh-Plesset equation are cast into a constitutive equation for the density for the pseudo-fluid. Results are obtained for several different cross-flow velocities for both cavitating and noncavitating flows. The model shows good agreement with measured discharge coefficients and also reveals vortex structures recently found in experimental observations.
MODELING THE PRIMARY BREAKUP OF HIGH-SPEED JETS
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10.1615/AtomizSpr.v14.i1.40
Rolf D.
Reitz
Engine Research Center, University of Wisconsin-Madison, Rm 1018A, 1500 Engineering Drive, Madison, Wisconsin 53706, USA
A new jet primary breakup model is proposed and applied to high-speed jets to predict the primary breakup characteristics. The liquid jet is modeled by discrete blobs. Initial conditions, such as jet diameter, injection velocity, and initial disturbances on the liquid jet, are provided by a nozzle flow model to reflect the effects of nozzle internal flow. The breakup characteristics of the jet are calculated by tracking the wave growth on the surface of each liquid blob using a one-dimensional Eulerian approach. Novel initial and periodic boundary conditions are applied to the computational domain that allow consideration of the unstable growth of complex initial disturbances. The surface structure of a blob is decomposed into a combination of waves with different wavelengths and is expressed in a Fourier series using a fast Fourier transform (FFT). The drops that are stripped from the surface are calculated from the surface wavelengths and amplitudes, as indicated by the Fourier coefficients. A multilayer drop-stripping model is proposed and multidimensional effects are included by reflecting the surface structure in the axial direction into the peripheral direction, as suggested by high-speed jet experiments that show that surface wavelengths are approximately isotropic. The new breakup model has been implemented in the multidimensional KIVA computational fluid dynamics (CFD) code to simulate spray atomization. The breakup model has been used to predict drop size, jet breakup length, and spray liquid penetration length. Comparisons with experimental data indicate that the new breakup model significantly improves spray predictions over standard atomization models that are based on linear jet stability theories.
THE FRACTAL GEOMETRY OF ROUND TURBULENT CRYOGENIC NITROGEN JETS AT SUBCRITICAL AND SUPERCRITICAL PRESSURES
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10.1615/AtomizSpr.v14.i1.50
Douglas
Talley
USAF Research Lab, CA, USA
Bruce
Chehroudi
Engineering Research Consultants, Inc. 10 E. Saturn Blvd., Edwards AFB, CA, USA 93524-7680
Box-counting and Euclidean distance mapping (EDM) methods were used to measure the fractal dimension of round turbulent cryogenic nitrogen jets at pressures ranging from subcritical to supercritical pressures. Both methods 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 second 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 spraylike behavior, while supercritical jets exhibit mainly gaslike behavior. This appears to have been the first time pressure effects on the fractal dimension of turbulent jets have been measured.