Comparison of Computed and Measured High-Pressure Conical Diesel Sprays 2000-01-0951
To model sprays from pintle type nozzles with large hollow cone angle and high injection pressure, the correct flow field in the near region must be predicted. A new model was implemented in KIVA-3V code, which adopts the theory of steady gas jet to correct the relative velocities between the drop and gas phases, based on the existence of quasi-steady part of the conical spray and an assumption of equivalent gas jet. Accordingly, the structure of the sprays is defined into three parts: 1. initial part that the gas phase velocity is set to the assumed gas injection velocity; 2. quasi-steady part where the component of velocity in the symmetric line direction of the spray is corrected; 3. stagnation part which is left unchanged. This new model is referred to as the Relative Velocity Correction (RVC) model, and is a set of empirical equations that calculate the sectional distribution of the gas-phase velocity along the symmetric line of the sprays.
The high-pressure conical diesel sprays with different ambient pressures (0.1, 1.0 and 2.0 MPa) have been numerically and experimentally studied. The computational results compared to experimental data, including penetration, photographic comparison, and drop size. The structure of the spray, such as gas entrainment and spray oscillation, has been clearly revealed. It was found that behavior of the conical sprays is much more sensitive to the ambient pressure increase than that of the solid sprays.