GDI and CR Diesel Sprays Wall Impingement Analysis

An interaction between numeric computation and experimental analysis has been performed to study the spray from high pressure and electronically controlled injection systems, successfully, today, used both in diesel and in Direct-Injection Spark-Ignition (DISI) engines. Spray evolution and its impact on a flat wall have been visualized and spray main parameters have been analyzed varying the injection pressure, the backpressure of the gas in an optically accessible test chamber and the temperature of the flat wall. Sprays have been lightened by a pulsed sheet generated by the second harmonic of a Nd-YAG laser (wave length 532 nm, duration 12 ns, thickness 80 μm). The scattered light has been collected at right angle respect to the laser sheet by a CCD camera whose frame grabber has been synchronized with the single shot injection command and the laser start pulse. A digital image processing software has allowed to extract characteristic parameters of sprays and of jets evolution on the wall after the impact. Detailed spatial and temporal sprays characterization has been carried out showing interesting peculiarities of jets for different operating conditions. Results of a work, aiming to select and to validate spray development and wall-impingement models, have been also reported. Calculations have been performed using KIVA 3V CFD code, modified in basic spray sub-models.