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Study on Behavior of Spray Droplets Near Diesel Injector Nozzle by L2F
Published May 23, 2012 by Society of Automotive Engineers of Japan in Japan
A laser 2-focus velocimeter (L2F) was used for measurements of velocity and size of droplets in diesel sprays. The L2F has a micro-scale probe which consists of two foci. Diesel fuel was injected intermittently into the atmosphere. The injection pressure was set at 80 MPa. Measurement positions were located at 5, 7, 10 and 15 mm from the nozzle exit. The measurement result showed that the droplet size of spray front decreased between 5 and 7 mm at the spray periphery, and then increased between 7 and 15 mm from the nozzle exit. It is understood that the breakup of droplets occurred in a near nozzle region, and the coalescence occurred between the droplet injected after and the droplet of spray front in a region downstream. The acceleration of spray front, the second derivative of the spray penetration, decreased between 4.5 and 7 mm at the spray periphery, and then increased between 7 and 10 mm from the nozzle exit. It is understood that the change in the droplet size is related to the change in the acceleration of the spray front.