Characteristics of air flow surrounding transient diesel sprays

An experimental study on the characteristics of airflow surrounding non-evaporating, evaporating, and burning transient diesel sprays inside a constant volume spray chamber was conducted under high chamber pressures and temperatures using a 6-hole injector and a simulated single-hole injector. Particle Image Velocimetry (PIV) was used to measure the gas velocities surrounding a spray plume as a function of space and time.; A conical control surface surrounding the spray plume was chosen as a representative side entrainment surface. The normal velocities crossing the conical control surface toward the spray plume for single-hole injection sprays were higher than those of 6-hole injection sprays and the velocities tangential to the control surface toward the injector tip for single-hole injection sprays were lower than those of 6-hole injection sprays. A significant increase in tangential velocities near the spray chamber wall suggests that the recirculation of surrounding gas was accelerated by the spray wall impingement.; Large differences between the speed of the spray tip and the measured maximum surrounding gas speed near the spray tip were observed, and it was estimated that over 60% of the total gas entrained into the spray plume appears to be entrained through the spray front head area for non-evaporating spray conditions. The normal and tangential velocities of evaporating spray conditions were larger than those of non-evaporating spray conditions. From the experimental results and close examination of a series of spray images, a general image of surrounding gas motion relative to the spray boundary was suggested for non-evaporating and evaporating sprays. For burning spray conditions the side entrained gas velocities were higher than for the non-evaporating spray conditions, but similar to the results from evaporating spray conditions. This was due to relatively long flame lift-off lengths that were comparable to the size of spray chamber.