Effect of co-and counter-swirling inner air on the spray dynamics of an annular fuel sheet in a hybrid atomizer

This paper reports important experimental findings of atomization of an annular swirling liquid sheet in the presence of swirling inner and outer air. The sandwiched fuel and the outer air has swirl in the same direction while the inner air swirl direction can be changed. Relevant spray dynamics has been presented for both the cases: a co-swirling as well as a counter-swirling inner and outer air. Swirl in all three fluid streams are imparted through a tangential entry. The co-swirl configuration is found to produce a more stable sheet with a higher breakup length than the counter-swirl one. This higher instability in the sheet with a counter-swirl has also been shown through a fractal dimension analysis using box counting method. A higher fractal dimension implying a higher level of tortuosity in the annular sheet is observed with a counter swirling inner air. The sheet width is expressed by a non-dimensional parameter named sheet expansion coefficient and is compared in the two configurations. Thus experimental investigation in an advanced hybrid injector leading to useful insights on atomization is presented in this article.