油圧作動油のキャピテーション

第3報 円筒絞りに生じるキャピテーションについて

抄録

The aim paper is to chairfy the limits of cabtation occurence inlong orifices.
Cavitation in round-deged and sharp-edged long orifices was detectde by means of the pressure fluctuation at the middle of the orifices, with the naked eye with astrobosoope and the ear. The experiments coverde the following ranges; orifice diamenter d=3∼6mm, orifice inlet pressure P₁<10.0kgf/cm²abs., orifice outlet pressure P₂<0.7kgf/cm²abs., and Reynolds number R_e=4Q/πdv=1900∼5700 in cavitating flow, where Q: flow rate, v: kinematic visoosity.
Juaging from the experimental results, it is reasonable to assume combined vortexes in the shear layer as mechanism of cevitetion in orifices. Based on this assumption, the limits of cacitation occurrence are then derived. While some paramemers were wxperimentally determined, the calculated valves coincide well with data reported by other investigators.
The limits are given us follows:
desinen cevitation number for round-edged longorifices,
k^d=(0.8-6.7((l/d)/R_e)^1/2)C_d²
desinent cacitation number for sharp-edged long orifices,
k^d=(1+0.25C²_v)(C_v/C)²-1
critical cavitation number=(P₂-P₁)/(P₁-P₂)P_v: vapor pressure, C_d: dscharge coefficient of long orifice, C_v: velocity onefficient of long orifice, C:discharge coefficient of sharp-edged short orifice; suffix, d:disinent, ch: chocking.