Hole number effect on spray dynamics of multi-hole diesel nozzles: An observation from three- to nine-hole nozzles

For the simplicity of optical diagnostics, studies on fuel spray and combustion characteristics of modern diesel engines have been conducted using the investigation nozzles having the reduced number of holes (two- or three hole nozzles) compared to the production nozzles. However, the similarity of spray dynamics between the investigation nozzles and production nozzles has not been confirmed yet. Also, the hole-number effect on spray dynamics has been investigated only in a limited range of hole number making it difficult to derive the clear trend and understandings of the hole number effect. In this study, the hole-number effect on spray dynamics of multi-hole diesel nozzles has been investigated in a wide range of hole number with sufficient data points (three, five, six, eight, nine-hole) by using the X-ray Phase-Contrast Imaging technique. The non-linear trend in the spray structure, as well as the dynamics results, was observed as increasing the hole number regardless of injection pressure. Discussions were made accordingly to understand the observed result trend. The study suggests that great attention is needed when deciding the number of nozzle holes for the optimized engine combustion.