Abstract
Measurements of temporal and spatial changes in the velocity and size of droplets of diesel fuel sprays were conducted near the nozzle orifice by a laser 2-focus velocimeter (L2F). The L2F had a high sampling frequency of 15MHz. Fuel sprays were injected intermittently into the atmosphere by using an 8-hole injector nozzle. The diameter of the nozzle orifice was 0.112 mm. The injection pressure was set at 40 and 135MPa. The time interval between injections was 333ms. Measurement positions were located at 10 mm from the nozzle exit. The number of data measured at each position was 40,000. The distance between droplets in the direction of droplets' flight was determined by multiplying the droplet velocity and the time interval between 2 droplets sequentially passing the measurement volume. The measurement result showed that the droplet velocity was the fastest at the center of fuel sprays and the droplet size near the spray center was larger than that at the periphery of fuel sprays. When the injection pressure became higher, the velocity and size of droplets became higher. The number density at the center of fuel sprays was lower than that at the periphery of fuel sprays. It was found that the luminance of spray image became higher with increase of injection pressure.
