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  • 1
    Digitale Medien
    Digitale Medien
    Temporal instability of plane gas sheets in a viscous liquid medium (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 8 (1996), S. 103-111 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: This paper reports a linear temporal instability analysis of an incompressible plane gas sheet in a quiescent viscous liquid medium of infinite expanse. Results indicate that there exist two unstable modes of disturbance waves, sinuous and varicose, and surface tension always reduces, while the relative velocity between the gas and liquid phases and the gas density always enhance instability development. For both unstable modes, the presence of liquid viscosity increases the instability limit, which is however independent of the absolute value of viscosity. It is also shown that the sinuous mode becomes stable when the gas Weber number, defined as the ratio of aerodynamic forces to surface tension forces, is less than the critical value of one. At slightly larger gas Weber numbers, liquid viscosity exhibits dual effects—it may enhance or suppress the growth of unstable disturbances, depending on specific flow conditions. However, for sinuous mode at high Weber numbers and varicose mode at any Weber numbers, liquid viscosity always reduces disturbance growth rates and dominant wave numbers. Unlike the case for plane liquid sheets, varicose mode controls the instability process for all Weber number ranges and for both inviscid and viscous liquids, and only at high Weber numbers, do varicose and sinuous modes become almost equally important. It is further found that the wave propagation velocity for both unstable modes is much smaller than the gas velocity at the mode of maximum instability, implying that the disturbance waves appear almost stationary rather than travelling-wave type, in contrast with the plane liquid sheet results. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.868819
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  • 2
    Digitale Medien
    Digitale Medien
    Natural convection in vertical slots with wall temperature oscillation (1994)
    Springer
    Experiments in fluids 16 (1994), S. 308-315 
    Details
    ISSN: 1432-1114
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Natural convection in vertical slots has been studied experimentally with oscillation of a cold wall temperature. It is found that at sufficiently large Rayleigh numbers travelling-wave instability occurs, but only in the region close to the cold wall when the hot wall is maintained at the initial temperature, and appears in both cold and hot regions when both hot and cold wall temperatures are changed simultaneously and symmetrically with the initial temperature value, although the hot wall temperature is kept constant after the change. The observed instability may be attributed to the “leading-edge” effect induced by the cold wall temperature oscillation, and selectively amplified by the natural convection flow.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00195429
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  • 3
    Digitale Medien
    Digitale Medien
    Fischer-Tropsch synthesis on Fe-Mn ultrafine catalysts (1994)
    Springer
    Catalysis letters 23 (1994), S. 245-250 
    Details
    ISSN: 1572-879X
    Schlagwort(e): Fe-Mn catalyst ; ultrafine particle ; FT synthesis ; active phase ; role of Mn
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The Fischer-Tropsch (FT) synthesis on Fe-Mn ultrafine catalysts prepared by a special degradation method of Fe-Mn complexes is presented. The effects of preparation method and Mn content on the FT performance are examined and the active phases and the role of Mn are elucidated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00811359
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  • 4
    Digitale Medien
    Digitale Medien
    On the Prediction of Droplet Size and Velocity distributions in sprays through maximum entropy principle (1992)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 9 (1992), S. 195-201 
    Details
    ISSN: 0934-0866
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Based on the conservation laws of mass, momentum and energy, the droplet size and velocity distributions in liquid sprays are formulated through the maximum entropy principle, without taking into account the details of liquid atomization processes such as the characteristics of disturbances and behavior of liquid bulk preceding the droplet formation. The joint probability distribution function in size and velocity of the droplets can be predicted from the atomization conditions which are represented by the Weber number and the source terms in the formulation. The model prediction agrees well with the experimental data measured by a phase Doppler particle analyzer.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ppsc.19920090126
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  • 5
    Digitale Medien
    Digitale Medien
    Calculated Characteristics of Droplet Size and Velocity Distributions in liquid sprays (1990)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 7 (1990), S. 54-59 
    Details
    ISSN: 0934-0866
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Predictions of the droplet size and velocity distributions in sprays under isothermal conditions are reported. The calculations are based on the maximum entropy formalism, complying with the conservation laws of liquid mass, momentum and energy. This theoretical approach considers only the macroscopic quantities about the atomization processes, without resorting to the details of the liquid breakup processes such as the onset and growth of instabilities. The derived joint droplet size and velocity distribution function depends on the Weber number as well as the liquid mass, momentum and energy source terms.These parameters represent the conditions under which the atomization occurs. The droplet velocity distributions are truncated Gaussian distributions for any specific sizes. The nondimensional Sauter mean diameter decreases slightly with the Weber number and then approaches an asymptotic constant. The calculated values of D21/D30 are very close to unity which agrees with the experimental observations. The computations also show that the atomization efficiency is very low; less than 2.6 percent.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ppsc.19900070111
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  • 6
    Digitale Medien
    Digitale Medien
    A Droplet Vaporization Model for Spray Calculations (1992)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 9 (1992), S. 59-65 
    Details
    ISSN: 0934-0866
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A semi-analytical model of multi-component droplet vaporization in a convective environment is formulated. The model includes many important physical effects such as variable properties, non-unity Lewis number, transient liquid phase heat and mass transport, and the blowing effect of evaporation on heat, mass and momentum transfer. The liquid phase heating is calculated from a Nusselt number model which incorporate heat transfer enhancement due to internal circulation. The model predictions are in good agreement with detailed numerical results for droplets vaporizing in various ambient conditions. The behavior of droplets in simultaneously changing concentration, temperature and velocity fields, is also examined.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ppsc.19920090110
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