Impact of Air to Liquid Mass Ratios on the Spray Features in the Near Field of a Flow-Blurring Atomizer

摘要

Clean combustion of liquid fuels greatly relies on effective fuel atomization to promote lean premixed combustion. Conventional injectors generate a liquid jet first which atomizes into spray at farther downstream locations by shear layer instabilities. In contrast, flow blurring (FB) injector applies a two-phase flow concept to produce fine spray at the nozzle exit. Clean combustion of fuels such as biodiesel, straight vegetable oil (VO), and glycerol has been achieved without fuel any pre-processing by using the FB injector. Previous studies have also revealed the FB spray features in the injector near field for a fixed atomizing air to liquid mass ratio (ALR). This study investigates the effect of different ALRs in the near field of FB water sprays to delineate the break-up mode, and quantify the droplet velocity field and turbulence characteristics. High speed visualization with exposure time of 1 μs and acquisition rate of 100k frames per second (fps) is employed to directly probe the spray near-field. Time-resolved particle image velocimetry (PIV) is used to capture frame-straddled image pairs with the interval of 1 μs at 15 kHz to quantify the flow features.