Search Results

Tumble and swirl motions in the cylinder of a four-valve SI engine with production type cylinder head were investigated using a cross-correlation digital Particle Image Velocimetry (PIV). Tumble motion was measured on the vertical symmetric plane of the combustion chamber. Swirl motion was measured on a plane parallel to the piston crown with one of intake ports blocked. Large-scale flow behaviours and their cyclic variations were analysed from the measured two-dimensional velocity data. Results show that swirl motion is generated at the end of the intake stroke and persists to the end of the compression stroke. Tumble vortex is produced in the early stage of the compression stroke and distorted in the late stage of the stroke. The cyclic variation of swirl motion is noticeable. The cyclic variation in tumble dominated flow field is much greater.

Using a Laser Doppler Velocimetry with Burst Spectrum Analyzer (LDV-BSA), droplet velocities of a diesel fuel spray under a pressure higher than 100 MPa were measured at different points within the spray profile. Results show that although the mean velocity distribution at the sampling plane is rather uniform, the number-based droplet velocity distributions of two sampling points at the same plane are different. The conclusions agree with theoretical predictions through maximum entropy principle qualitatively.