Search Results

Diesel homogeneous charge compression ignition (HCCI) engines with early injection can result in significant spray/wall impingement which seriously affects the fuel efficiency and emissions. In this paper, the spray/wall interaction models which are available in the literatures are reviewed, and the characteristics of modeling including spray impingement regime, splash threshold, mass fraction, size and velocity of the second droplets are summarized. Then three well developed spray/wall interaction models, O'Rourke and Amsden (OA) model, Bai and Gosman (BG) model and Han, Xu and Trigui (HXT) model, are implemented into KIVA-3V code, and validated by the experimental data from recent literatures under the conditions related to diesel HCCI engines. By comparing the spray pattern, droplet mass, size and velocity after the impingement, the thickness of the wall film and vapor distribution with the experimental data, the performance of these three models are evaluated.

The mechanism of NOx and soot reduction using different pilot and multiple injection strategies has been computationally studied in a heavy duty DI Diesel engine. A designed set of advanced injection schemes with various variables and exhaust gas recirculation rate (up to 10%) have been analyzed. The CFD model was firstly calibrated against experimental data for a part load operation at 1600 rpm. The computational models used were found to predict the correct trends obtained in the experiment. The study demonstrated the potential and explained the mechanism of the combination of EGR and multiple injection to reduce both soot and NOx emissions together with improved fuel economy.