2.2.3. Spray Visualization Measurement

Spray visualization experiments were carried out in order to directly confirm the injection speed and behavior for each prototype. In this study, a static chamber with a volume of 885 cc was used, and images were taken with a high speed camera through a quartz glass window with a diameter of 108 mm and a thickness of 50 mm. This experiment was conducted at a normal temperature and pressure, and used a Bosch common-rail system. Since the prototype injector used in the experiment was a piezo-driven type, it was controlled using a universal piezo actuation driver (Zenobalti Co., Model:ZB-6200, Korea). Detailed specifications of the high-speed camera (Vision Research, Model:Phantom V7.3, Wayne, NJ, USA) used in this study are shown in Table 3. Direct lighting spray images were obtained using an 80 W LED light source. The experimental conditions of the spray visualization experiment are shown in Table 4. Figure 5 shows a schematic and actual picture of the injection test apparatus used in this experiment.

**Table 3.** Specifications of the high-speed camera.


**Table 4.** Experimental conditions for spray visualization.


**Figure 5.** Spray visualization measurement; (**a**) Visualization apparatus, (**b**) Definition of spray parameter.
