The asymmetry of the multi-orifice spray will cause uneven heat load of the marine diesel engine, thereby affecting its working performance and service life. Therefore, an in-depth understanding of the spray and flame characteristics of multi-orifice nozzles will guide the optimization of the nozzle structure, needle design and diesel atomization and combustion process. For this reason, four groups of dual-orifice nozzles with different hole diameters (0.1–0.55 mm) and mass flow rates covering the typical marine medium-speed diesel injections are designed and customized, and the constant volume chamber (CVC) with high temperature and pressure is used to simulate the actual in-cylinder working conditions of the diesel engine for the spray visualization experiment. To study the asymmetry of the fuel sprays discharged from a diesel injector, the multi-orifice nozzle is simplified as a dual-orifice nozzle in this study. Combined with X-ray Computed Tomography (CT) imaging technology, the influences of the nozzle internal structure on the spray and flame asymmetry are studied in the constructed supercritical environment. It is found that the asymmetry of the inlet angle and the equivalent length-diameter ratio is positively correlated with the inconsistency of the dual sprays. With an increase in the injection pressure and nozzle diameter, the asymmetry of the dual spray becomes more pronounced, resulting in greater disparities in the ignition delay times and ignition positions of the two sprays. Moreover, the increase in nozzle diameter also leads to combustion instability, resulting in a flame with a serrated appearance. With the increase of ambient temperature, the proportion of liquid phase in the jet decreases and the relative density of spray front decreases.
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