City Research Online

Abstract

Cavitation structures developing within the injection holes of high-pressure Diesel injectors are known to affect the emerging spray shape and its stability. The present study attempts to link the development of these cavitation structures to the near-nozzle spray formation for a Valve Covered Orifice (VCO) nozzle and a new Diesel nozzle design concept, through use of high speed flow visualisation applied on large-scale and real-size transparent nozzle replicas. A prototype Diesel nozzle has been manufactured that eliminates the sac volume and isolates the flow path that links adjacent injection holes. Comparison between the two Diesel nozzle designs reveals that the spray instabilities observed with the VCO nozzle are linked to the development of vortex cavitation inside the injection holes. This flow characteristic is absent in the new nozzle design concept that produces fairly stable sprays. Unlike the VCO nozzle design, geometric cavitation becomes a controlled flow characteristic that is used to alter fuel atomisation and near-nozzle spray angle.

Publication Type:	Book Section
Publisher Keywords:	Cavitation, Vortex Flow, Visualisation, Enlarged Nozzle Replicas, Real Size Nozzle, Spray Atomisation
Subjects:	T Technology > TJ Mechanical engineering and machinery
Departments:	School of Science & Technology > Engineering

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