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

Abstract

The thermal usage of liquid fuels implies their combustion, which is a process strongly influenced by the performance of the atomizer, which disrupts the fuel into drops of the required sizes. The spray quality of the twin-fluid atomizers with internal mixing (IM-TFA) is primarily influenced by the two-phase flow pattern inside the mixing chamber. We studied the performance of the four types of the IM-TFA nozzles by the optical diffraction system (Malvern Spraytec) to answer the question of how the mixing chamber design influences the spray quality at low atomizing gas consumption. We tested the effervescent atomizer in outside-in-liquid (OIL) and outside-in-gas (OIG) configurations, the Y-jet nozzle and new nozzle design, and the CFT atomizer when spraying model liquids with the viscosities comparable to the common fuels (μ=60and143 mPa· s). We found that the effervescent atomizer performance was strongly influenced by the configuration of the inlet ports. Although the OIL configuration provided the best spray quality (D32 = 72 μm), with the highest efficiency (0.16%), the OIG nozzle was characterized by unstable work and poor spray quality. Both the devices were sensitive to liquid viscosity. The Y-jet nozzle provided a stable performance over the liquid viscosity spectrum, but the spray quality and efficiency were lower than for the OIL nozzle. Our findings can be used to improve the performance of the common IM-TFA types or to design new atomizers. The results also provide an overview of the tested atomizers’ performances over the wide range of working conditions and, thus, help to define the application potential of the tested nozzle designs.

Child droplets from micro-explosion of emulsion and immiscible two-component droplets

“…First, large droplets, several millimeters in size, can be generated using pulverizers of simpler design and lower pressures. Secondary atomization of droplets due to their micro-explosive breakup can provide the size (see section 4.3 for analysis), which is comparable to that of droplets obtained using special-purpose pulverizers [31].…”

“…However, when slurry fuels (for instance coal water slurries) are burned in boiler unit furnaces, the droplet size may be both 40-250 µm [33] and increase up to several millimeters [34] depending on the component concentration and viscosity of the composition. The size of a primary droplet (R d ≈1.1 mm) is in fact larger by an order of magnitude (Table 1) than the size of droplets that are normally burned in internal combustion chambers [31].…”

“…In actual applications, such as fuel combustion, droplet size may vary in a wide range. For example, when fuel is burned in internal combustion chambers, droplet diameters may range from 5 to 180 µm [31,32], depending on the type and design of the atomizer used. However, when slurry fuels (for instance coal water slurries) are burned in boiler unit furnaces, the droplet size may be both 40-250 µm [33] and increase up to several millimeters [34] depending on the component concentration and viscosity of the composition.…”

“…However, as mentioned earlier, one of the purposes of this research is to study the atomization process and characteristics of the resulting child droplets. This mechanism is proposed as an alternative to mechanical atomization of a composition using pulverizers [31][32][33][34]. First, large droplets, several millimeters in size, can be generated using pulverizers of simpler design and lower pressures.…”

Laminar Air Curtains as Protection against Respiratory Infections

“…Thanks to the smoke from the smoke machine, which is discharged at a certain speed and direction, it is possible to realistically visualize the air flow and more quickly to find the places of turbulence. The principle of the smoke machine's function is the use of a special liquid, which is glycerol or glycol dissolved in distilled water, and it is pumped into hot copper tubes, the end of which is fitted with a nozzle [11].…”