Influences of Ultrasonic Excitation on Breakup and Atomization of Liquid Jets in Crossflow

Liquid jets in crossflow are common ways of delivering large amounts of fuel in a rapidly atomized form to modern aircraft combustor systems. Unfortunately, they are not able to deliver the necessary droplet sizes for the demands of future advanced propulsion systems without modification. In this study, an ultrasonically excited solid obstruction, or pintile, is added to the liquid jet in crossflow system. This addition is intended to introduce additional instabilities in the liquid jet, improving on jet breakup characteristics across a wide range of Weber numbers. This setup is then subjected to a range of crossflow conditions, while maintaining the momentum flux ratio of the jet, and imaged using Mie scatter techniques in both the streamwise and transverse planes. Lagrangian droplet tracking is applied to the streamwise plane to obtain distributions of droplet sizes, velocities, and droplet generation rates to compare the excited and unexcited liquid jets. The sheet breakup distance is tracked in the transverse plane and compared. Across each condition studied, the introduction of the ultrasonically excited pintile led to improvements in the breakup characteristics of the liquid jet. For low Weber conditions, excitation led to a 45% decrease in average droplet size, and a corresponding 380% increase in droplet production rate. The sheet breakup distance was additionally shortened by more than 25% for each case studied, demonstrating substantial improvement to the inactive pintile, proving to be a strong candidate for next generation fuel injection technologies.