Bruce J. P. Mortimer
School of Elec. Eng., Cape Technikon, P.O. Box 652, Cape Town, 8000, South Africa
Beric W. Skews
Univ. of the Witwatersrand, Johannesburg, 2050, South Africa
Water jets can be either continuous or pulsed. Pulsed or discrete water jets have many advantages over continuous jets in certain applications. The production of discrete jets has mostly been due to a momentum transfer from a mass impacting a compression chamber. In this study the feasibility of using a novel adaptation of an electromagnetic source (EMAS) for the production of a pulsed water jet is investigated. This device consists of a high-voltage 4-8 F, 20-kV capacitor which is discharged through a flat pancake coil. An insulated metal disk is in close proximity with the coil. Lorentz forces due to the eddy currents induced in the disk accelerate the disk away from the coil. The disk acceleration produces a shock wave in a liquid-filled cavity. A convergent reflector focuses the wave onto a nozzle. The reflection of the shock wave from the water--air interface produces a discrete water jet. A theoretical analysis of the electrical characteristics of the transducer is presented. A finite-element package was used to optimize the convergent reflector. Experimental results from a prototype generator are given including pressure measurements from a needle hydrophone and schlieren photographs of the water jet. [Work supported by FRD.]