Analysis on pressure fluctuation and unsteady cavitation inside high-pressure diesel injection nozzles

Pressure fluctuations and unsteady cavitation within a single-hole diesel injection nozzle, together with combination between these two phenomena, were investigated thoroughly through experimental measurements and three-dimensional numerical modeling. Analysis results indicate that pressure in the diesel injection nozzle fluctuates more dramatically as the magnitude of injection pressure increases and maximum frequency of fluctuation even reaches 40 kHz. Sharp pressure fluctuations have a significant impact on the evolution of cavitation process in nozzle hole, and rate of pressure change derived from pressure fluctuation can be regarded as an important index to evaluate the cavitation degree inside diesel injection nozzle holes. Moreover, dynamic behaviors of cavitation bubble at different locations of nozzle hole cavitating flow field are obviously distinct. As location closes to the outlet of nozzle hole, the corresponding dynamic behavior of cavitation bubble is more unstable and accordingly becomes more sensitive to pressure fluctuations.