Breakup characteristics of a pulse jet issuing into a compressed gas environment under different injection conditions

Abstract

The dynamics of jet breakup undergo significant alteration due to the influence of a compressed gas environment. In the first injection stage of an air-assisted fuel injector (AAFI), fuel is introduced into such an environment. Therefore, studying the influence of injection conditions on the jet breakup characteristics has significant importance for AAFI spray. This study utilized a high-speed camera to record the jet breakup images in a compressed gas environment. Subsequently, these images were analyzed using MATLAB to get the spray penetration distance and fuel projection area (FPA). The research findings indicate that both fuel injection pressure (FIP) and fuel–gas pressure drop (ΔP) exert influence on jet breakup characteristics, with ΔP exhibiting more significant influence. Maintaining ΔP at 1 bar, when FIP increased from 4 to 7 bar, gas Weber number (Weg) increased by 87%. While maintaining gas pressure at 5 bar, as ΔP increased from 1 to 3 bar, Weg escalated by 194%. Additionally, jet breakup length under different injection conditions followed a pattern as summarized by Bonhoeffer et al. [“Impact of formulation properties and process parameters on the dispensing and depositioning of drug nanosuspensions using micro-valve technology,” J. Pharm. Sci. 106(4), 1102–1110 (2017)]. The jet surface disturbance was enhanced by the increase in both FIP and ΔP. The detachment of the droplets from main jet stream induced by ΔP resulted in an increase in jet flow width. Furthermore, the effect of ΔP on FPA was more significant compared to FIP. As ΔP rose from 1 to 3 bar, the time-averaged FPA and area-to-mass ratio (Raq) increased 245% and 207%, respectively.