GB1467258A - Nozzle device - Google Patents

Abstract

1467258 Ejectors IMPERIAL CHEMICAL INDUSTRIES Ltd 23 April 1974 [16 May 1973] 23332/73 Heading F1E [Also in Division B1-2] A high-pressure liquid jet device, suitable for hydrodynamic cleaning, comprises a jet tube 7 for delivering liquid, e.g. water or an organic solvent, at a pressure of at least 50 bar and a nozzle 1 having an internal passage 2, the nozzle comprising an entry zone 3 for fluid, e.g. steam, a restricted throat zone 4, a frusto-conical expansion portion 5 and a cylindrical mixing zone 6 having a discharge orifice the end of the jet tube 7 being disposed in the throat zone 4 and being directed towards the discharge orifice. In use, fluid admitted to the entry zone 3 and passing through the throat zone 4 is accelerated in the expansion portion 5 to a speed in excess that of the liquid leaving the jet tube 7, and in the mixing zone 6 the fluid imparts momentum to the liquid leaving the jet tube. The radius of curvature of the smoothly curved upstream shoulder of the throat zone is between one-tenth and twice the diameter of the throat. The included angle of the frusto-conical expansion portion 5 is between 5 degrees and 15 degrees, and the mixing zone 6 has a length: diameter ratio of between 1:1 and 10:1. The ratio of the fluid pressures at the inlet end of the entry zone 3 and the throat zone 4 may be so arranged that the fluid is accelerated to sonic velocity at the throat zone 4, and accelerated to supersonic velocity in the expansion portion 5. The fluid may be heated before passing through the throat zone 4. The orifice speed of the jet is typically 100 to 500 m/sec and the liquid supply pressure may be up to 7000 bar, but is preferably less than 1000 bar. The jet tube 7 may be of hardened steel or tungsten carbide.