Numerical Study of String Cavitation and Spray Dynamics in a High-disturbance Nozzle under Engine-operating Conditions

String cavitation in injector nozzles has been shown to improve spray atomization while mitigating cavitation erosion. Herein, to comprehensively investigate flow behaviors under realistic engine conditions, we employ a validated computational fluid dynamics model to simulate coupled in-nozzle wall-bounded cavitation flow and near-nozzle spray flow. The characteristics of multiphase flow are extracted using the Omega vortex identification method and Lamb vector analysis. Under nine sets of representative operating conditions, injection performance is assessed using flow coefficient, total pressure recovery coefficient, vapor phase distribution, and kinetic energy transport equation. Near-nozzle spray behavior is evaluated based on the momentum flux, liquid breakup rate, and vorticity transport equation. The results indicate that the high-disturbance nozzle has good application prospects and exhibits a flow coefficient of ۰.۷–۰.۸, whereas the total pressure recovery coefficient varies between ۰.۶ and ۰.۷. Optimal injection performance is observed under conventional conditions, whereas atomization quality is enhanced under idle conditions. Additionally, cylinder pressure causes jet momentum attenuation under accelerating conditions and considerably affects the development of string cavitation in the jet core under idle and normal conditions, forming bidirectional tearing and one-way tearing of liquid film with different vorticity transport terms, thus affecting the atomization process.

کلیدواژه ها:

Diesel engine ، Vortex cavitation ، Multiphase flow ، Fuel injection ، Spray atomization