Effect of nonideal conditions on the electrical performance of faraday MHD generators

Abstract

The effect of nonideal conditions on the current flow in a MHD generator has been investigated by two‐dimensional analysis in terms of internal resistance, Hall voltage and uniformity of current distribution. In particular, the effects of (a) temperature profile along the Faraday direction in the plasma, (b) current bunching on cathode surfaces due to phenomena like arc spots, and (c) electrical leakage between adjacent electrodes due to finite resistance of the insulator segments are investigated. the results show that cold boundary layers near metallic electrode surfaces tend to relieve current concentration. the optimum resistivity of wedge‐shaped electrodes for obtaining uniform current distribution in the duct has been calculated for various temperature profiles. the results indicate that the internal resistance of a MHD generator strongly depends on the location and size of current bunched spots on cathodes. the fluctuations in the spot size and its location can lead to large fluctuations in power output. the present calculations reveal that the electrical performance of a MHD generator is not adversely affected by current leakage along insulator segments for small insulator conductivities.

Effect of velocity profile models on the gasdynamic voltage drop in open-cycle mhd generators

“…The change in m, say from 8 to 7, affects the gasdynamic voltage drop estimation by about 26 per cent which is practically the same for different values of Po in the range studied. In order to understand the above dependence of gasdynamic voltage drop on m physically, we look at various velocity profiles generated by choosing different values of m. As studied by various workers (Lengyel, 1969;Jayakumar et al, 1978;Sodha et al, 1979), one interprets the exponent l / m used to describe the velocity profile as a direct measure of boundary layer thickness. If l / m increases (m decreases), the velocity profile becomes less steep giving rise to a thicker boundary layer and vice versa.…”

Recent advances in open cycle MHD electrical power generation

“…This probably arises from the different economic standards and costing procedure. Figure 30 summarises the cost of electricity from open cycle MHD steam power plant with different parameters (Jayakumar et al 1978). If the fuel cost is less than 15 roubles/unit, the thermal plant is more economical (region A, curve 6) whereas if the fuel cost is higher than 15 roubles/unit, MHD is more economical (region B, curve 4).…”