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.

翻译：氢及其衍生物（如电制甲醇、电制甲烷和电制氨）是有望替代传统燃料的能源载体，能够消除传统燃料的有害环境影响。将氢气作为零排放燃料的一种创新用途是：在氢气燃烧产物中掺入微量碱金属蒸气（铯或钾），形成弱电离等离子体。这种等离子体可用作超音速开环磁流体（OCMHD）发电机组的工作流体。在这些OCMHD发电机组中，直流电可直接生成，无需旋转涡轮发电机。本研究定量与定性探究了典型OCMHD超音速通道中的电导率水平及其产生的体电输出功率密度。在该通道中，热平衡等离子体以马赫数2被加速，同时受到5特斯拉的强外加磁场作用，温度为2300 K（2026.85 °C）。我们将预电离掺铯气体混合物的总压力从1/16个大气压变化至16个大气压，种子份额（预电离摩尔分数）从0.0625%变化至16%，种子类型在铯与钾之间切换，氧化剂类型在空气（氧气与氮气的混合物，摩尔比21-79%）与纯氧之间切换。结果表明：若能将总绝对压力降至仅约0.1个大气压，且采用铯而非钾作为种子，理想功率密度可达到超过1000 MW/m³（或1 kW/cm³）的极高水平。