Analyses on response of a liquid metal MHD power generation system to various external inputs

We numerically analyze the response of a liquid metal MHD power generation system to various external inputs of piston force (regular: constant (step), square, sinusoidal; irregular: Piersion-Moskowitz (P-M)) with three different working fluids (NaK78, U-alloy47, and mercury), where the electrical efficiency is mainly examined in the presence of the shape loss due to different cross-sectional areas between the MHD generator and piston driver parts. Although the electrical efficiency is reduced owing to the shape loss, the deterioration can be mitigated by using NaK78 with low density and high electrical conductivity and compensated by the increase in the applied magnetic flux density. For the period shorter than 1 s, the output power markedly decreases, although the electrical efficiency seems to recover toward the ideal value. The irregular force input based on the P-M wave gives no big difference compared to the regular forces when the effective value of the input is the same, which can provide the prospect of utilizing a real ocean wave.