Experimental study on the spray steadiness of an internal-mixing twin-fluid atomizer

Abstract

Liquid breakup intensity in the near-nozzle region and droplet size fluctuations at different downstream positions of an internal-mixing twin-fluid (IMTF) atomizer were studied by using a high-speed camera and a Malvern Spraytec diffractometer, and the effect of operating conditions on spray steadiness was analyzed. The results show that under the operating conditions of this study, the primary breakup process of IMTF atomization is affected by various breakup modes, and the characteristic droplet diameters at a given position exhibit different degrees of fluctuation, which can be considered to be inherently unsteady. The primary breakup process at medium gas/liquid mass flow ratio (GLR) is more unsteady than that at either small GLR or large GLR. At different downstream positions, the steadiness of larger droplets is significantly lower than that of smaller droplets. Compared with the near-nozzle region, the spray steadiness is significantly improved in the fully developed region. Moreover, frequency spectrum analysis performed on the time-resolved data of various droplet characteristic diameters in the near-nozzle region shows the presence of a pulsation frequency in the spectrum diagrams. This pulsation frequency can be used for evaluating the influence of GLR on the spray steadiness.