Bubble formation regimes during gas injection into a liquid cross flow in a conduit

Abstract

A study was performed to characterize the different bubble formation regimes that occur during the process of gas jet injection into a liquid cross flow in a conduit. Air was injected perpendicularly into a turbulent, fully developed water flow circulating through a 12.7 mm square channel. Three different gas injectors, with diameters of 0.27 mm, 0.52 mm, and 1.59 mm were used. The bulk water velocity values ranged between 1.1 and 4.3 m/s. The effects that the gas injection velocity, liquid mean velocity, and injection gas injection diameter have on the process of bubble generation were investigated. A high‐speed visualization technique was used to determine the regimes near the gas inlet region. Four distinct regimes were identified: Single Bubbling (SB), Pulse (P), Elongated Jetting (EJ), and Atomizing Jetting (AJ). It was observed that the shift between regimes occurs gradually, producing the need to identify transitional regions: SBP and PTJ. Sets of independent dimensionless variables were used to categorize the proposed regimes using bubble formation maps. It was determined that the injection diameter plays a primary role in jet formation: as the injection diameter increased, the observable number of regimes decreased, indicating a more stable and continuous process of bubble generation. Empirical correlations that delimit the boundaries between ordered and chaotic bubble generation are presented.

Experimental Investigation of Effervescent Atomization, Part Ii: Internal Flow and Spray Characterization With Novel Darpa Suboff Afterbody Streamline Aerator

“…a. Single bubbling: Single bubbling is observed to be the formation of individual uniformly sized bubbles, which are either sheared directly from the emerging gas-phase at the aerator orifice or detach from a short "teardrop" shaped gas neck within the peripheral liquid flow (Figure 2a)this is in agreement with the literature descriptions (Loubière et al, 2004;Forrester et al, 1998;Balzán et al, 2017) . Upon injection, the bubbles are drawn away from the aerator with the liquid flow into the mixing chamber.…”

“…Given sufficient residence time and breakup mechanisms, these instabilities on the gas-liquid interface eventually gain sufficient amplitude to separate the neck into gas entities of varying size. The observations corresponding to pulse bubbling are in line with the definitions provided within the literature (Forrester et al, 1998;Balzán et al, 2017;Rigby et al, 1995). The region of pulse bubbling is shown in the regime map (Figure 3).…”

Bubble Formation in a Swirl-Venturi Microbubble Generator

“…The dimensionless parameters, gas Froude number Fr G and liquid Reynolds number Re L , are adopted to describe the influence of flow parameters on the bubble formation patterns, as shown in Figure . The calculation formulas are as follows F r G = u G g d or R e L = d throat u L ρ L μ L where d or is the orifice inner diameter, d throat is the throat diameter, ρ l is the liquid density, and μ l is the liquid viscosity.…”

Review of Research Related to Fluid Cokers

“…Using the appropriate venturi geometry is essential, because some venturi geometries give poor premixing . Premixing has a significant impact on the liquid distribution performance: − the liquid distribution on the fluidized bed particles can be correlated with the homogeneity of the gas–liquid dispersion in the nozzle conduit, just upstream of the nozzle tip, and good premixing is also associated with the formation of more stable sprays . With feedstocks that are less likely to create fouling issues, helical vane premixers could be used…”