الفهرس 
Some Problems that Face the Atomization ProcessOnly 14 pages are availabe for public view
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Abstract
Effervescent atomizers are a special form of the twin-fluid atomizers. A lot of advantages of the effervescent atomizers over the conventional atomizers that enable them to be utilized in many applications. This experimental study focuses on investigating the effect of the internal two-phase flow as well as the bubble size on the characteristics of the effervescent atomizer. The study covers the condition where, an ”in-out” gas injection configuration atomizer operates under low gas-to-liquid ratios by mass ”GLR” (0.71% to 5.74%). The shadowgraph technique is utilized for visualizing and quantifying bubbles inside the atomizer, spray characteristics, the near nozzle spray and the total spray structure. The two phase flow pattern directly upstream the exit orifice is compared with the predictions of the modified Baker’s map for vertical downward two-phase flow. The comparison shows a notable difference between the observed and the predicted flow patterns. For investigating the effect of the bubble size, the internal flow is controlled by bubble breakers (BB). Two novel bubble breakers are designed and tested.
from the visualization and measured results, the flow pattern is found to shift from a bubbly flow at GLRs ≤ 2.02% to a bubble-annular flow at the GLR of (5.74%), passing through an unsteady transition stage between these two patterns. Also, it is observed that the bubble breakers efficiently disintegrate large bubbles. The largest reduction percentage in the bubble size is 75.63% for the case of flat end BB at GLR of 2.21%. Also, the results showed that the DROP size and spray cone angle are strongly affected by the bubble size (i.e. the internal flow structure) subsequent to the presence of the bubble breakers. The largest reduction percentage in the droplet size is 68.88%, for the case of the cone end BB at GLR of 0.77%. Yet, the largest increment percentage in the spray cone angle is 69.97%, for the cone end BB at GLR of 0.77 %. All are relative to the case of without BB. Considering pressure fluctuations data and the total spray structure, it is observed that decreasing the GLR or increasing the pressure fluctuations magnitude of the internal flow inside the atomizer leads to an increase in the spray unsteadiness. It is also noted that the pressure fluctuations magnitude decreases in the presence of the bubble breakers inside the mixing chamber. It is observed that the cone end BB gives the lowest pressure fluctuations, and consequently the highest spray stability.