Experimental study of impinging jets of gelled and liquid fluids

This work presents an experimental study on spray formation by unlike impingement of gelled ethanol with liquid water and liquid ethanol, and a comparison with spray formation by like impingement of gelled ethanol. High-speed shadowgraphy was utilized to analyze collision sheets, instabilities, breakup lengths and particles of sprays formed by colliding jets with 0.80 mm diameter with equal momentum and different collision angles and flow conditions. For unlike jet impingement, the sheet evolution and disintegration showed a mixture of patterns found in Newtonian and non-Newtonian fluids, such as complex structures with rails, holes, fishbone, detaching beads and ligaments. Regime transition for unlike impingement configurations is faster than for like impingement, consequently the breakup lengths for unlike impingement were significantly shorter than for like impingement. In general, the breakup lengths decreased for larger We or larger jet momentum values and increased for lower impingement angles. Despite the improvement in the atomization caused by unlike configurations, small ligaments remained in all sprays formed by unlike jets. The particle sizes and geometries for the different configurations were evaluated and compared in terms of circularity, percent area and Feret diameter. No significant differences of the spray regions were observed between the two unlike impingement settings.