Atomization and Sprays, 22 (9): 733–755 (2012) ON THE DISINTEGRATION OF FAN-SHAPED LIQUID SHEETS M. Altimira, 1,∗ A. Rivas, 2 J. C. Ramos, 2 & R. Ant ´ on 2 1 Department of Mechanics, Kungliga Tekniska H¨ ogskolan, Osquars Backe 18, SE-100 44 Stockholm, Sweden 2 Thermal and Fluids Engineering Division, Mechanical Engineering Department, Tecnun (University of Navarra), Manuel de Lardizabal 13, 20018 Donostia-San Sebasti´ an, Spain * Address all correspondence to M. Altimira E-mail: mireia@mech.kth.se Original Manuscript Submitted: 9/12/2012; Final Draft Received: 12/12/2012 This paper presents a combined experimental and theoretical investigation of the disintegration of fan-shaped liquid sheets produced by industrial fan-spray atomizers. The disintegration regimes ob- served for different geometries and operating conditions are described, proving the paramount role of nozzle flow on the final characteristics of the spray produced. The concept of breakup length is rede- fined to account for the stochastic nature of liquid stream disintegration. An analogy is established between the breakup of a liquid sheet dominated by the wave mode and a radial sheet, obtaining good agreement with the experiments. However, in those cases where several disintegration regimes coexist, the breakup length cannot be given by an analytical expression. Finally, the influence of the disin- tegration regime on both the droplet size and the spatial distribution of the droplets is investigated, confirming the strong influence of rim breakup. KEY WORDS: atomization, experimental characterization, visualization tech- niques, liquid sheet, primary breakup, rim breakup 1. INTRODUCTION Sprays are encountered in nature, as rain or mist, and in many industrial applications in- cluding combustion, painting, spray cooling, agriculture, and powder metallurgy. Each application has its own requirements regarding the spray characteristics, such as the droplets’ size, velocity, and spatial distribution. The knowledge of the atomization mech- anisms allows the fulfillment of these particular requirements so a more efficient use of the atomized fluid is achieved. The liquid can be atomized either due to its own kinetic energy (pressure atomizers), the interaction with a gas with higher velocity (air-assist and air-blast atomizers), or by means of external devices (rotary, ultrasonic, and elec- trostatic atomizers), and is typically fed in the form of a jet or a sheet (flat, conical, or cylindrical). 1044–5110/12/$35.00 c  2012 by Begell House, Inc. 733