Measurement of Droplet Size, Shape and Velocity in Diesel Sprays using a Single and Double Nano-Spark Photography Method

Abstract

Fundamental investigation of non-evaporating diesel spray disintegration was carried out using single and double nano-spark back-light photography of diesel sprays injected into a constant volume chamber and relatively clear single and double exposure images of droplets were obtained. Droplet size, shape and velocity as well as the two-dimensional velocity vectors of the droplets have been simultaneously measured by analyzing the spray photographs, using an image processing system and developed analysis method. It was observed that even at the early period of injection, some droplets have a velocity much lower than the penetration velocity of the spray tip. The velocity of droplets around the spray tip is much hogher than the velocity of droplets near the nozzle tip. At the early period of injection, droplets flew away from the spray flow around the nozzle tip. However later at the same position, droplets were entrained into the spray flow. No droplet entrains into the spray around the spray tip at the early period of injection.