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The air-fuel mixture formation in an optical direct-injection internal combustion engine is investigated by numerical simulations for the two biofuels Ethanol and 2-Butanone. The gas phase in the internal combustion (IC) engine is predicted by a large-eddy simulation, in which the fuel phase is determined by a spray model based on Lagrangian particle tracking. A hollow-cone injector is used for which the primary breakup is modeled by a series of small full-cone injections, while the Rosin-Rammler initial droplet size distribution is used. The secondary spray break-up is modeled by the Kelvin-Helmholtz-Rayleigh-Taylor (KHRT) model, and the evaporation of the fuel is determined by the Bellan-Harstad model. The gas phase simulation is based on a finite-volume method formulated for hierarchical Cartesian grids, in which the immersed moving boundaries are resolved using a multiple level-set/cut-cell approach.

A Holographic Particle-Image Velocimetry (HPIV) system is developed to investigate the in-cylinder flow in a motored four-valve engine operated at 1500 rpm. Image aberrations introduced by the optical liner of the engine are optically eliminated using complex-conjugate hologram reconstruction that allows measurements near the cylinder walls also. High-resolution velocity measurements in different axial planes of the in-cylinder flow are made at crank angles from 60° to 285° ATDC. Prospects and limitations to full three-dimensional extension of the HPIV system are discussed. The results show the development of the in-cylinder flow in two planes with emphasis on large and small-scale flow structures.