Abstract: A visual test platform for the fuel injection atomization process is designed and built. With a nanosecond level flash lamp as the exposure light source, the digital camera and the long-distance micro imaging technology with high magnification and high resolution are used to visually capture the microstructure of the initial disturbance of the jet surface near the fuel nozzle area. Combined with the image post-processing technology, the jet surface structure parameters and injection parameters are measured and analyzed quantitatively. The study shows that the generation, deformation and breakup of the initial jet surface wave, liquid wire and liquid drop near the nozzle are closely related to the injection pressure, cavitation and environmental backpressure. With the increase of the injection pressure, the initial jet disturbance increases, and the “potholes” and “bulges” structures on the jet surface are more close to the nozzle. Cavitation promotes the formation of the initial jet disturbance, liquid wire and liquid drop, resulting in increase of the spray cone angle. With the increase of the environmental back pressure, the shear effect between the jet and the environmental medium increases and the initial breakup of the jet can be effectively promoted, and the liquid wire around the jet can be further broken to form droplet, which effectively improves the atomization quality

Key words: jet breakup mechanism, multiphase flow, microscopic imaging, visual experiment