MHD generator performance analysis for the Advanced Power Train study

Abstract

Comparative analyses of different magnetohydrodynamic (MHD) power train designs for early commercial MHD powerplants were performed for plant sizes of 200, 500, and 1000 MWe. The work was conducted as part of a program to formulate an MHD Advanced Power Train development plan. This paper presents the results of the MHD generator design and topping-cycle performance analyses. All of the MHD generator designs were based on burning of coal with oxygen-enriched air preheated to 922 K. OMPARATIVE analyses of different MHD generator designs were performed for early commercial MHD powerplant applications. Powerplant sizes of nominal 200, 500, and 1000 MW total electrical output were considered. The work reported herein was conducted as part of the first phase of a planned three-phase program to formulate an MHD Advanced Power Train (APT) development plan. This paper presents the results of the MHD generator design and topping-cycle performance analyses. The bottoming plant analyses and the overall powerplant designs and economics are described in Ref. 1. The MHD generators considered in this study were all designed to operate with preheated (922 K) oxygen-enrich ed air (30 to 36 molar percent oxygen) and Montana Rosebud coal dried to 5% by mass moisture content. Fuel-rich conditions were used in the MHD combustion process for NOX emission control with an oxidizer/fuel equivalence ratio of 0.9. The seed concentration was 1% potassium by weight of the total combustion gas. Sensitivities of the MHD generator performance to powerplant size (thermal input), oxygen enrichment level, channel length, Mach number, diffuser pressure recovery coefficient, magnetic field strength, and other factors were investigated. These sensitivity analyses were conducted in a systematic manner so that one can compare the true performance potential of the MHD generator designs between the various selected design conditions. Thus, if a design parameter was varied during the parametric analysis, the operating conditions of the MHD generator were also varied in such a manner that optimum performance was always obtained from the MHD topping cycle. The methodology and results of the generator design performance analyses are presented in Sees. II and III, respectively. Based on these MHD generator and topping-cycle performance studies, together with the results from the overall plant performance and cost-of-electricity analyses of Ref. 1, a generator design was selected for each of the three plant sizes. Table 1 summarizes the important design data for the three generators selected. The generators for the 200 and 500 MWe plants are of supersonic designs. Only subsonic generator designs were investigated for the largest plant size and one of these subsonic designs was selected for the 1000 MWe plant. Presented as Paper 84-0154 at the AIAA 22nd Aerospace Sciences