Abstract
Electrohydro dynamics (EHD) is a new field which combines electricity, magnetism and hydro dynamics. EHD power generation is an application of this field.
The author has conducted variational and maximum principle analyses of the optimal conversion process of incompressible EHD generation. However, a guiding principle in order to increase the output power and the physical meaning of the optimal conversion process have not been clarified sufficiently.
In this paper, the simple optimal solution derived earlier from the maximum principle has made it possible to analyze the power conversion process from fluid energy to electric energy in detail. The optimal power conversion characteristics of incompressible EHD power generator are expressed in terms of slip.
The conclusions of this investigation are summarized as follows:
(1) The duct configuration becomes slender trumpet-shaped as the output power increases if the total duct volume is fixed.
(2) The energy of working fluid pressure is converted to electrical and mechanical kinetic energies in the first half of the optimal process. Around the duct outlet, both the current density and the electric field intensity are decreased rapidly and the electric output energy density is reduced considerably. As a result, the kinetic energy is not fully converted to electrical energy but converted to energy of working fluid pressure. This is the basic principle to improve the conversion efficiency limiting the pressure drop between the entry and exit ends.
