Investigation of cavitation phenomenon with different fuel temperatures in diesel nozzles

Two-phase cavitating flow in the diesel nozzle has been widely concerned by researchers for a long time. Most of the attention has been paid to irregular geometry-induced cavitation, while the research on string cavitation induced by vortex is relatively less. The two cavitating patterns often occur simultaneously in the nozzle, which are still not understandable for their interaction characteristics. In this paper, it is analyzed that the characteristics of string cavitation and geometry-induced cavitation in the transparent nozzle based on the visual scale-up test bench. In the study of hole-to-hole string cavitation, it is found that when needle lifts elevate, geometry-induced cavitation and hole-to-hole string cavitation are observed all together under the same working condition. The development and stability of hole-to-hole string cavitation are further improved with the increase of fuel temperature. The geometry-induced cavitation and string cavitation interact with each other, that is, geometry-induced cavitation at the nozzle inlet interrupts the hole-to-hole string cavitation inception. The tail of hole-to-hole string cavitation is disturbed by cloud cavitation shedding after its developing into the nozzle hole, leading to fracture in serious cases. At high temperatures, there is a periodic transformation between the needle-originated string cavitation and hole-to-hole string cavitation.