Investigation of Effect of Fluid Properties on Near-Field Spray Characteristics of a Two-Phase Swirl Burst Injector

Effective atomization dictates clean and efficient liquid fuel combustion. A novel twin-fluid swirl burst injector combining reverse internal and external swirls (SBCR) injector has previously produced fine and stable sprays for water at the injector immediate exit, rather than a typical jet of conventional atomizers that are highly sensitive to slight fuel property variations. Based on the superior SBCR atomization, this study investigates the effect of fluid properties on the SBCR spray behavior at a constant air-to-liquid mass ratio (ALR) of 2.0. 100% water, 100% glycerol, and 50%/50% glycerol/water blend (by mass) are selected to span a broad range of viscosities and surface tensions representative of both conventional and bio-derived fuels, providing relevance for combustion systems seeking sustainable fuel alternatives. Under the same operating conditions, droplet size distribution, breakup dynamics, and spray stability are evaluated using high-speed X-ray imaging and frequency-domain analysis. The SBCR injector produces fine and stable droplets at the injector immediate exit for both 100% water and 50%/50% glycerol/water blend, while thin ligaments are discharged for 100% glycerol. Within ~15 mm downstream of the injector exit, ~90% of droplets remain below ~29 µm and SMD values stay under ~18 µm for 100% water and 50%/50% glycerol/water blend. For 100% water, the local instantaneous SMD in the injector near field exhibits very small temporal fluctuations, indicating highly stable spray behavior. In contrast, the 50%/50% glycerol/water blend shows modest viscosity-induced variations in local SMD at certain radial locations. Overall, both fluids maintain fine and stable droplet sizes, underscoring the SBCR injector’s robust atomization performance even with moderately viscous fluids.