A Detailed Computational Analysis of Cavitating and Non-Cavitating High Pressure Diesel Injectors

Demands for higher power engines have led to higher pressures in fuel injectors. Internal nozzle flow plays a critical role in the near nozzle flow and subsequent spray pattern. The internal flow becomes more difficult to model when the injector pressure and internal shape make it more prone to cavitation. Two Bosch injectors, proposed for experimental and computational studies under the Engine Combustion Network (namely “Spray C” and “Spray D”) are modeled in the computational fluid dynamics code ANSYS Fluent. Both injectors operate with n-dodecane as fuel at 150 MPa inlet pressures. The computational model includes cavitation effects to characterize any cavitating regions. Including compressibility of both liquid and vapor is found to be critical. Also, due to high velocity gradients and stresses in the nozzle, turbulent viscous energy dissipation is considered along with pressure work resulting from significant pressure changes in the injector. Results are compared against available experimental data and demonstrate that Spray C has a cavitating zone along the nozzle wall whereas Spray D is noncavitating. The influences of fluid compressibility, liquid and vapor property implementations, and inclusion of energy solution are shown to be important for the internal flow as well as nozzle exit flow with direct impact on atomization and spray pattern. Finally, the two injectors are compared to examine the influences of fuel vapor formation due to cavitation on important quantities at the nozzle outlet.