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Analyses of the power generation performance and the non-equilibrium plasma of a disk MHD generator

In this study, the results relating to a plasma state which takes into account the ionization instability of non-equilibrium seeded plasma is added to the theoretical prediction of the relationship between enthalpy extraction and isentropic efficiency. As a result, the electron temperature, which reaches the seed complete ionization state without the growth of ionization instability, can be realized at a relatively high seed fraction condition. However, the upper limit of the power generation performance is suggested to remain lower than the value expected in the low seed fraction condition. It is also suggested that a higher power generation performance may be obtained by implementing the electron temperature range, which reaches the seed complete ionization state at a low seed fraction. | TAÏP CHÍ PHAÙT TRIEÅN KH&CN, TAÄP 19, SOÁ K2- 2016 Analyses of the power generation performance and the non-equilibrium plasma of a disk MHD generator Le Chi Kien Ho Chi Minh City University of Technology and Education (Manuscript Received on March 12nd, 2015, Manuscript Revised April 04th, 2016) ABSTRACT Recently, closed cycle MHD power generation system studies have been focused on improving the isentropic efficiency and the enthalpy extraction ratio. By reducing the crosssection area ratio of the disk MHD generator, it is believed that a high isentropic efficiency can be achieved with the same enthalpy extraction. In this study, the results relating to a plasma state which takes into account the ionization instability of non-equilibrium seeded plasma is added to the theoretical prediction of the relationship between enthalpy extraction and isentropic efficiency. As a result, the electron temperature, which reaches the seed complete ionization state without the growth of ionization instability, can be realized at a relatively high seed fraction condition. However, the upper limit of the power generation performance is suggested to remain lower than the value expected in the low seed fraction condition. It is also suggested that a higher power generation performance may be obtained by implementing the electron temperature range, which reaches the seed complete ionization state at a low seed fraction. Key words: Isentropic efficiency, enthalpy extraction, ionization instability, seed fraction, closed cycle MHD. 1. INTRODUCTION In recent years, closed cycle MHD power generation research has been placed on improving the isentropic efficiency in addition to the enthalpy extraction ratio with a great interest. Enthalpy extraction ratio (EE) is defined as the ratio of the electrical output to the heat input while the isentropic efficiency (IE) is the ratio of |hi –hf|actual to |hi –hf|isentropic. Here hi, hf represent the total enthalpy of the initial state and .