Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Effect of Load on Performance of LMMHD Generator
K. X. Song1, 2; A. W. Peng1, 2; L. Z. Zhao1, 2
1Institute of Electrical Engineering Chinese Academy of Sciences, Beijing, China
2

University of Chinese Academy of Sciences, Beijing, China

ABSTRACTthe inlet velocity of the liquid metal increased, the generation efficiencyof the single channel LMMHD generator decreased. Furthermore, theinduced magnetic field could be almost negated by using double
generation channels. As a result, the LMMHD generator could obtain
almost constant generation efficiency at any inlet velocity of the liquid
metal. The large-eddy simulation of the turbulent duct flow in an
LMMHD generator was examined to reveal the behavior of the MHD
flow and the turbulent structure (Hiroki et al., 2011). It was found thatthe non-uniform magnetic flux density in the streamwise direction
produced two eddy currents, and they caused the wall-jet flows with Mshaped mean streamwise velocity profiles in the plane perpendicular to
the applied magnetic field. An equivalent circuit model of the LMMHD
generator was built based on the basic steady-state electromagnetic
characteristics and 3D simulations of the generation channel (Zhao etal., 2011). The calculative and experimental results were compared,
which showed that the proposed equivalent circuit model andcalculation methods were valid with a higher computational accuracy.
The 3D numerical simulation analysis of the generation channel of anLMMHD generator was carried out based on the computational fluid
dynamics method (Yi et al., 2021). Results showed that the input
energy decreased with the increase of load factors, but there was an
optimal load factor to maximize the output power and the generation
efficiency.

Taking the induced magnetic field, the electrode current, the loadposition and the conductive area of the load into consideration, theperformance of an LMMHD generator under load condition isinvestigated with COMSOL and 3D numerical simulations. Results
show that the load position and the conductive area of the load might
affect the output power and the generation efficiency. When the load isplaced in the middle of electrodes and the ratio of the conductive areaof the load to electrodes is about 0.8, the output power and thegeneration efficiency are maximum.

KEY WORDS: LMMHD generator; induced magnetic field; liquidmetal.

INTRODUCTION
The power generation experiment of an 11.5 kW MHD generator wasdone successfully in 1959 and this confirmed the feasibility of MHD
power generation technology (Brogan et al., 1962). And performancesof LMMHD generators were studied in Argonne National Laboratory
in 1963 (Petrick et al., 1964). Since then, the LMMHD generator has
been studied around the world and remarkable results have beenachieved. Nowadays LMMHD generators have been widely used invariable displacement vehicles, wave energy power generation systems
and thermoacoustic power generation systems (Haaland, 1995; Liu etal., 2018; Brekis et al., 2020).

In the LMMHD generator, the electric conductivity of the liquid metal
is so large as to be comparable with that of electrodes. Under suchconditions the perfect conductor approximation no longer holds forelectrodes because the electric potential is not constant and distributes
unevenly in electrodes as well as in the liquid metal. Nobuhiro et al.
(1971) found that the distortion extent of electric equipotential lines
depended on the conductivity ratio of electrodes to the liquid metal, andon the load connection. The effect of the electrode length and theposition of current lead connection on the performance of an LMMHD
generator was studied (Katsunori et al., 2006). It was found that theinduced magnetic field generated by the electrode current might affectthe output power and the generation efficiency. How Katsunori ever, inmost numerical simulations of LMMHD generators, it is assumed thatelectrodes are ideal conductors, and the induced magnetic field

The basic working principle of an LMMHD generator is Faraday's lawof electromagnetic induction. The liquid metal is driven to cut themagnetic line of flux in the generation channel by an internal
combustion engine or a wave energy converter or a thermoacoustic
engine, realizing the direct conversion of mechanical energy into
electrical energy. In recent years, with the steady increase ofcomputational capabilities, the performance of LMMHD generators hasbeen studied numerically. The effect of the induced magnetic field on
the performance of an LMMHD generator was investigated bynumerical simulations (Shingo et al., 2007). The results showed that as540