Experimental and numerical investigation of high-pressure Diesel sprays with multiple injections at engine conditions

A numerical methodology to simulate the high pressure spray evolution and the fuel-air mixing in Diesel engines is presented. Attention is focused on the employed atomization model, a modified version of the Huh and Gosman, on the definition of a turbulence length scale limiter and of an adaptive local mesh refinement technique to minimize the result grid dependency. All the discussed models were implemented into Lib-ICE, which is a set of libraries and solvers, specifically tailored for engine simulations, which runs under the open-source CFD technology OpenFOAM. To provide a comprehensive assessment of the proposed methodology, the validation procedure consisted into simulating, with a unique and coherent set-up of all models, two different set of experiments: a non-evaporating Diesel fuel spray in a constant-volume vessel with optical access and an evaporating non-reacting Diesel fuel spray in an optical engine. The first of these experiments were carried out by the authors by analyzing optical pictures of the jets taken at different instants by imaging technique. A Common-Rail based injection apparatus was used for injecting commercial Diesel fuel at pressures ranging from 50 to 123 MPa inside a constant volume vessel at engine-like density conditions and operating in single shot mode. Literature data were then used to validate the vapor fuel-air mixing at engine conditions.