This paper describes the results of analytical and experimental studies of a helical magnetohydrodynamic (MHO) seawater thruster using a 8-Tesla (T) solenoid magnet. The application of this work is in marine vehicle propulsion. Analytical models are developed to predict the performance of the helical MHO thruster in a closed-loop condition. The analytical results are compared with experimental data, and good agreement is obtained.
The presence of salts allows seawater to conduct electricity by electrolytic ion exchange. Thus bypassing an electric current through seawater in the presence of a magnetic field, a Lorentz (J x B) force will act to move the seawater in the direction normal to both the magnetic field and electric current (Fig. 1). This is the basis for MHD propulsion. Few mechanical moving parts are required with MHD propulsion. As a result, this type of propulsion may be acoustically attractive. Recently there has been an increase of research and development in this field (Un, 1992). An experimental MHD ship, Yamato-l, has been constructed in Japan (Motora et al., 1991). It uses two MHD thrusters, each capable of producing 4,000 N of thrust. Research in the United States includes experiments at Argonne National Laboratory (ANL) (Petrick et al., 1991), Naval Undersea Warfare Center-Newport (NUWC-N) (Meng et al., 1991), and Applied Research Laboratory of Penn State (Un et al., 1992). Analytical studies of seawater propulsion (Doss and Roy, 1991; Un et al., 1991a) and seawater electrolysis, conductivity enhancements, and electrode studies (Lin, 1990; Gilbert et al., 1991) have been conducted. The experiments of ANL, NUWC-N and ARL Penn State use 6-, 3.2-, and 8-T magnets, respectively. The analytical studies did not consider the effects of electrolytic bubbles on the performance of the thrusters until later (Un et al., 1991b), which showed that these effects are significant.
