Assessment and Validation of Internal Aerodynamics and Mixture Preparation in Spark-Ignition Engine Using LES Approach

Abstract

A workflow for the assessment and validation of internal aerodynamics and mixture preparation in a representative high-tumble optical engine using Large Eddy Simulation with the commercial code CONVERGE^TM is proposed. First, the prediction of the aerodynamic movement in the engine is compared to Particle Image Velocimetry (PIV) measurements. The global velocity fields and position of the center of the tumble for the average experimental and simulation cycles are compared, showing a very good match of the global behavior. The cycle to cycle aerodynamic variability is investigated thanks to velocity profiles, showing that the simulated cycles feature comparable velocity fluctuations to the experiments. In a second part, to account for Direct Injection (DI), a Lagrangian spray modeling approach is used to take into account the injection process. Experimental spray penetration data are used for the calibration of the spray models, leading to a faithful representation of the spray. Mixture preparation in the engine is then assessed, comparing the fuel air equivalence ratio of the LES in the central plane to LIF diagnostics. This qualitative comparison shows a good prediction of the evolution of the position of the fuel-rich areas and overall mixing during the compression stroke. The cycle to cycle variability of the mixing process is found comparable to the experiments, though underestimated. An evaluation of this methodology is given and the next steps towards combustion computations are discussed.