A Basic Experimental Study of Gasoline Direct Injection at Significantly High Injection Pressures 2005-01-0098
In gasoline direct injection engines with stratified-combustion strategies only a short time is available for mixture preparation. Therefore, investigations are carried out to evaluate the influence of high injection pressure up to 50 MPa in order to optimize the mixture preparation. Two types of multi-hole injectors are analyzed in a pressure vessel under various pressure and temperature conditions. Laser light sheet visualization technique is applied in order to determine spray characteristics like shape, angle, penetration depth and spray width. To determine the velocity of the air surrounding the spray, a PIV (Particle Image Velocimetry) measurement technique is used. Droplet sizes and velocities are measured with a Phase Doppler Anemometer (PDA) in different positions in the spray center and at the spray edge. Spray visualization experiments show the influence of evaporation on spray propagation at higher temperatures. With increasing chamber pressure, a widening of the jet is observed, while its length remains nearly constant. PIV-measurements show a torus-like flow at the spray front and a distinctive air entrainment into the spray, which depends on injection pressure and chamber pressure. Analyses of droplet velocity and diameter with PDA reveal high velocities of very small droplets at higher injection pressures. However, droplet velocity does not increase in the same dimension as does the fuel pressure.