Photonium particle structure free#

In these bands of frequency, the external forcing appears to promote a new kind of interfacial instability that, instead of producing the usual large Rayleigh drops, breaks the outer layer of the jet into droplets much smaller than the jet diameter. The induced atomization can take place only in small discrete bands of the forcing frequency. It is experimentally demonstrated that an intact liquid jet can be induced to atomize by imparting periodic external forcing at the jet nozzle. In addition, uniform drops with diameters predetermined by the ultrasound frequency can be accomplished by adjusting the air velocity. Hence, it is further concluded that secondary atomization is negligible in co-flow two-fluid atomization of a water jet at air velocities up to 170 m/s and air-to-water mass ratio up to 5.6. Furthermore, all peak drop diameters can be accounted for by the harmonic frequencies of the ultrasound. Good agreements between the theoretical predictions by these models and the experimental results of how drop-size and size distributions are influenced by air velocity and surface tension led to the conclusion that Taylor-mode breakup of capillary waves plays a very important role in two-fluid atomization.

Theoretical calculations of the amplitude growth rate are based on two models of temporal instability of wind-generated capillary waves: Taylor’s dispersion relation and Jeffreys’ one-parameter (sheltering factor) model. Atomization occurs when the wave amplitude becomes too great to maintain wave stability the resulting drop sizes are proportional to the wavelength of the resonant capillary waves which is determined by the harmonic frequency of the ultrasound in accordance with the Kelvin equation. As these capillary waves travel downstream in the direction of air flow, their amplitude is further amplified by the air flowing around them. Specifically, capillary waves are established on the surface of a liquid jet as it issues from a coaxial two-fluid atomizer, the nozzle tip of which vibrates at the same frequency as the ultrasound while the frequency of the capillary waves is only half of the ultrasound frequency. This technique is based on resonance between the liquid capillary waves generated by ultrasound and those generated by high-velocity air. (C) 1998 Acoustical Society of America.Ī mechanistic study of two-fluid atomization has been carried out using a new spray technique called ultrasound-modulated two-fluid (UMTF) atomization. The comparison between theoretical and experimental results allows the determination of the internal damping coefficient. The influence of the materials mechanical damping on the displacement amplitude of the atomizing surface is investigated. A sizing method of the stepped horn is established and experimentally tested. The present study focuses on an analytical analysis of the longitudinal oscillations stimulated by the piezoelectric elements in a stepped horn which operates as an amplitude transformer. This may be achieved using a displacement amplitude transformer. The displacement amplitude of the atomizing surface must be greater than 2 mu m to initiate the atomization process.

Photonium particle structure free#

The fine atomization of liquids by means of low-frequency ultrasonic atomizers (about 50 kHz) results from unstable surface waves generated on the free surface of a thin liquid film, This thin liquid film develops as the liquid spreads fast over the atomizing surface of the atomizer. Within the range of working conditions tested, the application of this formalism is successful and provides a procedure for the prediction of spray drop size distributions from calculations only. The relationship between the mean drop diameter and the surface wave wavelength was accurately determined and introduced into a mathematical approach based on the maximum entropy formalism to predict the drop size distribution of the spray.

The thickness of the liquid film was measured and its effects on the drop diameter were studied together with the effects of both the liquid's physical properties and the ultrasonic atomiser's characteristics. This paper focuses on a systematic experimental analysis of the sprays produced by low-frequency ultrasonic atomisers. The thin liquid film develops as the liquid spreads over the atomising surface of the atomiser. These unstable waves are obtained from the tuning of the amplitude and the frequency of an imposed oscillation. The atomisation of liquids by means of low-frequency ultrasonic atomisers results from unstable surface waves generated on the free surface of a thin liquid film.