An experimental analysis of the spraying processes in improved design of effervescent atomizer

Abstract

This work experimentally examines the primary atomization processes in a newly developed atomizer, similar to effervescent atomizer concept, at low pressures and low gas-to-liquid ratios (GLR). Several experimental and post-processing techniques are applied to investigate the spray spatial evolution. The near-nozzle area is captured by a high-speed camera with a long-distance microscope. Further, characteristics of the developed spray are investigated by a phase-Doppler analyser (PDA). The high-speed recordings are processed by the proper orthogonal decomposition (POD). The frequency analysis of examined phenomenon is done by the fast Fourier transformation (FFT) at selected positions in the images. The POD enables to sort out data according to the importance of characteristic shapes occurring in the recordings. The velocity and dimensions of discharging liquid are measured in images by a point-tracking method. Dimensionless criteria are estimated to describe the atomization principles where several new findings are found comparing the previous studies. The spatial spray evolution is described by the processed PDA data. A simplification, based on the Stokes number, is used to estimate a gas motion in the spray. This approach enables to investigate the interaction between the spray and ambient atmosphere. The combination of experimental and post-processing techniques confirms the previous findings of the improved effervescent atomizer. In other words, the atomizer operates inherently at annular twophase flow regime which, however, leads to a specific atomizing mechanism i.e. bubble bursts, the same as in the effervescent spraying process. However, an importance of the interaction between the two following bubble bursts is highlighted as driving atomization mechanism. This specific behaviour is reason why the atomizer can be operated at low consumption of gas and low-pressure regimes. Moreover, the applied experimental and post-processing techniques indicate a potential for further advanced data post-processing of the stochastic processes of liquid atomization.

Spraying of Viscous Liquids: Influence of Fluid-Mixing Mechanism on the Performance of Internal-Mixing Twin-Fluid Atomizers

“…As our previous work Mlkvik et al [21] revealed, the investigated OIL configuration proved that the injection port configuration has a significant influence on the performance of the atomizer. This was later confirmed by Zaremba et al [22]. The CFT ( Figure 1c) nozzle has a design inspired by several previous works Chin [31], Ferreira M. Teixeira [32], Tamaki N.and Shimizu [33].…”

“…With regard to the values of We mix , Bo mix and the Fr mix (Table 2), the OIL device was characterized by the dominant influence of fluid inertia and gravity on the internal flow. The internal flow pattern was identified as the wall-attached [16,21,22], Figure 7a). The internal two-phase flow pattern led to the continuous passage of the liquid film through the discharge orifice without significant GLR fluctuations [15].…”

“…All the internal flow dimensionless parameters of this device were comparable to its OIL counterpart, and yet, the OIL and the OIG performance differed sharply. The switch of the gas and liquid injection ports led to an internal flow different from those observed for the OIL nozzle [16,22]. Two-phase flow maps are often used to determine the internal flow pattern for the OIG type of atomizers [1,39].…”

“…The authors investigated the fluid injection into the mixing chamber and linked the ratio of the fluid momentum to the observed internal flow pattern. This approach was also successfully applied to the modified design of an effervescent atomizer [21,22].…”

Air-Core-Liquid-Ring (ACLR) Atomization: Influences of Gas Pressure and Atomizer Scale Up on Atomization Efficiency

“…In IMP atomizers, atomization gas and liquid stream are brought into contact in a mixing zone inside the atomizer and leave the atomizer through the exit orifice in a two-phase flow pattern. For this purpose, several gas injection geometries have been proposed (e.g., [15,17,[20][21][22][23]). Although no targeted mixing of gas and liquid is performed in most cases [24], it is well known for IMP atomizers that internal flow conditions determine the means of liquid disintegration and the spray development in time and space [22].…”