Study on in-nozzle flow and spray behavior characteristics under various needle positions and length-to-width ratios of nozzle orifice using a transparent acrylic nozzle

Abstract

This study visualizes and analyzes the changes in cavitation flow and spray characteristics that depend on the needle position and length-to-width ratios of the nozzle. We tested five needle positions that simulated the eccentricity of the needle. The length-to-width ratios were set at 2.0 and 2.67. The width of the nozzle was taken as 3 mm and 4 mm, and the length of the nozzle was fixed at 8 mm. The cross section of the test nozzles was rectangular. The injection pressure was set at 1–4 bar in 0.1 bar increments, and the inside of the nozzle was visualized using shadow graphic visualization. The flow rate of the fluid, the injection pressure applied to the inside of the nozzle, and the material properties of the fluid were measured in terms of the Reynolds number, the cavitation number, and the discharge coefficient, respectively. We analyzed the spray angle, cavitation length, and cavitation width inside the nozzle from the captured images by using image processing, as well as the correlations between the spray angle and cavitation length and width.