1995-02-01

Investigation of Drop Size Distribution in the Spray of a Five-Hole, V.C.O. Nozzle at High Feeding Pressure 950087

The spray of a 5-hole, V.C.O. nozzle for D.I. diesel engines has been studied; the data obtained from each hole were compared. A high pressure injection system (Elasis patent), electronically controlled, was used.
To investigate the behaviour of each hole a “cap” was used to cover the nozzle in such a way that only one hole at a time could inject in the spray chamber. The investigation consisted of a photographic characterization with back-light technique and of the droplet size distribution through laser diffraction technique via Malvern.
Four pressure values (30, 60, 90, 120 MPa) and three injected flowrates (10, 25, 40 mm3/inj.) were chosen to characterize the behaviour of the nozzle. Each test was carried out with the nozzle under normal running conditions, measuring the laser signal background after each acquisition. The influence of the injection frequency, of the number of the injections needed before running conditions, of the background measurement and data acquisition were investigated. The investigation revealed the presence of an internal part of the spray made of drops of smaller diameter. The different value of droplet size distribution in sprays, obtained from different holes but working under same conditions, have been attributed at the different hole inclination in respect to the injector axis. More inclined holes produce sprays of droplet of bigger diameter.

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