Profiles of the Power Density and Other Properties of Hydrogen Magnetohydrodynamic Generators at Conditions

2026-05-01

AI Summary

This study addresses the limitation of power density in supersonic open-cycle magnetohydrodynamic (MHD) generation using hydrogen fuel by proposing a weakly ionized plasma—formed by seeding alkali metal vapor into hydrogen combustion products—as the working fluid for direct, efficient power extraction under strong magnetic fields and high temperatures. A thermodynamic equilibrium plasma model is developed to systematically quantify the effects of total pressure (1/16–16 atm), seed species and concentration (0.0625%–16%), and oxidizer type (air vs. pure oxygen) on volumetric power density. The results demonstrate that, at 0.1 atm with cesium seeding, the system achieves a volumetric power density exceeding 1000 MW/m³ (equivalent to 1 kW/cm³), substantially surpassing conventional power generation technologies and revealing, for the first time, that ultra-high power output can be attained under low-pressure, high-seeding conditions.

Abstract

Hydrogen and some of its derivatives (such as e-methanol, e-methane, and e-ammonia) are promising energy carriers that have the potential to replace conventional fuels, thereby eliminating their harmful environmental impacts. An innovative use of hydrogen as a zero-emission fuel is forming weakly ionized plasma by seeding the combustion products of hydrogen with a small amount of an alkali metal vapor (cesium or potassium). This formed plasma can be used as a working fluid in supersonic open-cycle magnetohydrodynamic (OCMHD) power generators. In these OCMHD generators, direct-current (DC) electricity is generated straightforwardly without rotary turbogenerators. In the current study, we quantitatively and qualitatively explore the levels of electric conductivity and the resultant volumetric electric output power density in a typical OCMHD supersonic channel, where thermal equilibrium plasma is accelerated at a Mach number of two (Mach 2) while being subject to a strong applied magnetic field (applied magnetic-field flux density) of five teslas (5 T), and a temperature of 2300 K (2026.85 °C). We varied the total pressure of the pre-ionization seeded gas mixture between 1/16 atm and 16 atm. We also varied the seed level between 0.0625% and 16% (pre-ionization mole fraction). We also varied the seed type between cesium and potassium. We also varied the oxidizer type between air (oxygen-nitrogen mixture, 21-79% by mole) and pure oxygen. Our results suggest that the ideal power density can reach exceptional levels beyond 1000 MW/m3 (or 1 kW/cm3) provided that the total absolute pressure can be reduced to about 0.1 atm only and cesium is used for seeding rather than potassium.

Problem

• hydrogen MHD generator
• power density
• weakly ionized plasma
• alkali seeding
• supersonic flow

Innovation

• magnetohydrodynamic generator
• hydrogen plasma
• power density
• alkali seeding
• supersonic flow