Abstract
Non-evaporating spray penetration characteristics for multiple diesel oil injections at atmospheric conditions are studied by comparing numerical simulations, effected by means of two different numerical codes, and experimental results collected in a constant volume vessel of controlled thermodynamic conditions. Different injection strategies are implemented via a Programmable Electronic Control Unit on a Common Rail system with dwell time between injections up to the electro-mechanical limits of a Multijet injector. The instantaneous and total amount of delivered fuel is measured by an AVL Injection Rate Meter, operating according to the Bosch principle. Images of jets emerging from the nozzle in different operating conditions are captured by using an AVL Engine Videoscope with a CCD camera and a properly synchronized flash-like lightning system. The jets dynamics is extracted through a digital image processing software in order to analyze temporal and spatial behavior. The non reacting flow simulation is effected by means of the FIRE code, whereas the KTVA3 V code is used to analyze both the non reacting spray dynamics and the process of auto-ignition, combustion and pollutants formations. Reacting flow calculations are performed using a detailed chemistry mechanism for a diesel fuel surrogate. To get consistent data, the KIVA3V and FIRE predictions are preliminary compared for the same operating conditions. Reliability of both the code in predicting the spray behaviour is proven, by properly customizing the employed versions. The different multiple-injection schedules are found to have considerable effects on droplet and fuel vapor distribution, hence also on auto-ignition, combustion and emissions (soot, NO_X) formation. Among the injection schedules studied, the most optimal one is singled out as the one leading to complete fuel consumption and reduced amount of generated pollutants.
