Visualization of internal flow and the effect of orifice geometry on the characteristics of spray and flow field in pressure-swirl atomizers

The quality of fuel atomization has a significant influence on combustion efficiency and emissions. One way to achieve optimized engine performance is to minimizing the atomized droplet size, which, in turn, is strongly related to injector characteristics. At present, achieving high precision in mass manufacturing of nozzles on micrometer scales is very difficult, the irregular internal geometry caused by minor deviations are inevitable, so that the circumstances of internal flow that are considered to have a major impact on the spray are diversiform. In this paper, the influence of conical, inclined and diameter error that embody common deviations in orifices on atomization were experimentally investigated. The transparent orifices were mounted in a typical pressure-swirl atomizer and ultra-precisely measured by fiber probe measurement system. The internal flows of nozzles were visualized and their spray characterization analyzed. The experimental results indicate that smaller cylindrical nozzle has inhibition effect on air-core development and the SMD is a little larger at low pressure. Convergent nozzles have the worst effect on air-core and atomization process. Divergent nozzles have better performance at low pressure but the discharge coefficients (Cd) are very low. Inclined nozzles have an adverse effect on the SMD, Cd and uniformity of atomizing area. (C) 2017 Elsevier Ltd. All rights reserved.