On the evolution of n-octane atomization characteristics using an air-assisted intermittent spray method

Abstract

In this study, droplet size and velocity of an intermittent air-assisted n-octane spray were measured using a Phase Doppler Particle Analyzer, focusing on the effect of operating parameters on time-resolved droplet behavior and local gas flow characteristics. An electro-magnetically actuated air-assisted injector, which features internal gas-liquid premixing upstream and releasing through an annular nozzle, was used to generate intermittent sprays. The sampling time equalization method is employed to examine the time-resolved spray microscopic characteristics with various injection control parameters and spatial sampling positions. The droplet diameter range is found to be generally independent of air injection duration and sampling time while droplet velocity is correlated with these two parameters. A large air injection duration tends to accelerate droplets in the late spray period and leads to an increasing normalized gas flow velocity. Estimation of local gas flow turbulence intensity indicates a prominent radial sampling position dependence due to the rapid attenuation of the gas flow velocity away from the spray axis. A noteworthy finding for this intermittent air-assisted spray is that at 30 mm from the nozzle outlet, the zero point of droplet-gas mean slip velocity shifts toward the nozzle with sampling time. The time bin size employed to divide the sampling time has been proved to exert no influence on the statistical results of transient spray microscopic characteristics.