This paper describes our recent experiments in nonintrusive pumping of seawater by the JxB Lorentz force principle. For the first time the magnetohydrodynamically (MHD) induced two-phase seawater flows were photographically and video graphically recorded at the center of a multi-Tesla solenoid magnet. A closed seawater loop using a synthetic "sea salt" solution was installed in and around the magnet. The plexi-glass test section consisted of two parallel electrodes that passed the d.c. current through the seawater. The test section was placed at the center of the magnet with the magnetic field being perpendicular to the current, so that the Lorentz force was created in the axial direction of the test section. As a result of electrolysis, hydrogen and chlorine/oxygen gases were produced at the cathode and anode, respectively. In addition to the visualization of the complex two-phase MHD flows, performances of the test section as an MHD pump were also studied. The MHD-induced flow rate, the thrust, and the mechanical efficiency as functions of the current and magnetic field will be discussed.
Marine vehicle propulsion based on the Magnetohydrodynamic (MHD) principle has been a technical speculation for some time. Because seawater conducts electricity (0" = 4 – 5(1/Ωm), It can be subjected to the JxB Lorentz force. The MHD thruster of a marine vehicle brings in the seawater from its proximity, imparts the electromagnetic energy to the seawater, and then discharges it at a higher pressure and momentum. The vehicle is thus propelled by the rearward momentum transfer. Few mechanical moving parts are required with MHD propulsion. As a result, this type of propulsion can be very quiet. This technology did not hold much promise due to the requirement of very high magnetic field until the advent of the superconducting multi-Tesla magnets.
