A wide variety of processes make use of plain orifice nozzles. Fuel injectors for
internal combustion engines incorporate these nozzles to generate finely atomized sprays.
Processes such as jet cutting, jet cleaning, and hydroentanglement, on the other hand, use
similar nozzles, but require coherent jets. The spray or jet characteristics depend on the stability
of the flow emerging from the orifice. This problem has been extensively researched for nozzles
with diameters above 300 μm. Much less is known about the characteristics of jets produced by
nozzles with smaller diameters, where viscous effects and small geometric variations due to
manufacturing tolerances are likely to play an increasing role. Results are presented of a
wide-ranging investigation of geometry effects on the flow parameters and jet characteristics
of nozzles with diameters between 120 and 170 μm. Nozzles with circular cross-section and
conical, cone-capillary and capillary axial designs were investigated. For conical and conecapillary
nozzles, the effect of cone angle and effects due to interactions between adjacent
nozzles in the multi-hole cone-capillary nozzles were studied. For capillary nozzles, the effects
of diameter variations and inlet edge roundness for capillary nozzles were considered.
Furthermore, the effect of varying the aspect ratio (ratio of major and minor axes) of elliptical
nozzles was studied. Flowrate and jet impact force measurements were carried out to determine
the discharge coefficient Cd, velocity coefficient Cv, and contraction coefficient Cc of the nozzles
for supply pressures between 3 and 12 MPa. Visualizations of the jet flow were carried out in
the vicinity of the nozzle exit in order to identify near-nozzle flow regimes and to study jet
coherence. The relationship between nozzle geometry, discharge characteristics, and jet coherence is examined.
History
School
Mechanical, Electrical and Manufacturing Engineering
Citation
GHASSEMIEH, E., VERSTEEG, H.K. and ACAR, M., 2006. The effect of nozzle geometry on the flow characteristics of small water jets. Proceedings of the IMechE Part C: Journal of Mechanical Engineering Science, 220 (12), pp. 1739-1753