Author(s): Umberto Fratino; Alessandro Pagano; Stefano Malavasi; Gianandrea Vittorio Messa
Linked Author(s): Alessandro Pagano, Umberto Fratino
Keywords: No Keywords
Abstract: Multi-hole orifices are largely used in hydraulic pressurized systems either as flow conditioner or, placed side by side a control device, to attenuate the onset and the development of cavitation. The hydraulics of single and multi-hole orifices have been widely discussed in literature, with the main aim of identifying the most important parameters affecting their performances. In particular, it has been found by many Authors that the dissipation and cavitation characteristics of such devices are significantly affected by geometrical features, such as the contraction ratioβ, the dimensionless plate thickness t/d h and the number n h and disposition of the holes. In order to further clarify the role played by these parameters, with particular attention for the case of multihole orifices, the results of two experimental campaigns, carried out by research groups of Polytechnic School of Bari and Polytechnic School of Milan in two different pilot plants, are reported and discussed. Several devices, characterized by different geometries, were tested in variable flow conditions. In particular, the equivalent diameter ratio varied between 0. 2 and 0. 72, the dimensionless thickness between 0. 2 and 1. 44 and the number of holes between 1 and 52. The result of the two campaigns appear consistent, and confirm the remarkable dependency of the dissipation characteristics of the devices, expressed in terms of pressure loss coefficient K and discharge coefficient C d, upon the above mentioned geometrical parameters. A comparison to different literature models is provided. At last, the problem of estimating the pressure recovery length is also considered.
Year: 2012