Finite amplitudes helical waves on the surface of the conducting fluid earth core as an example of the self-exciting homopolar heterogeneous dynamo

International audienceHelical waves of the finite amplitude on a surface of the fluid conducting Earth core are examined for generation of the magnetic field. Estimates are made for the differentially rotating cylindrical conducting fluid body, with the helical surface wave structure on its top. This structure is similar to the self-exciting Faraday-disk homopolar heterogeneous dynamo. Estimations of angular velocity and magnetic field magnitude for a polar vortex on the surface of the Earth's liquid outer core gives reasonable numbers and proves this hypothesis to be of value for further detailed analysis. As magnetic field generation by the helical structure is a surface effect, it is possible to find connection between Earth magnetic field fluctuations and fast relief changes on the iron fluid core ? the silicate mantle boundary of the Earth

Comparative analysis of the Allam cycle and the cycle of compressorless combined cycle gas turbine unit

Nowadays, alternative thermodynamic cycles are actively studied. They allow to remove CO2, formed as a result of fuel combustion, from a cycle without significant energy costs. Calculations have shown that such cycles may meet or exceed the most advanced power plants in terms of heat efficiency. The Allam cycle is recognized as one of the best alternative cycles for the production of electricity. Nevertheless, a cycle of compressorless combined cycle gas turbine (CCGT) unit is seemed more promising for cogeneration of electricity and heat. A comparative analysis of the thermal efficiency of these two cycles was performed. Particular attention was paid to ensuring equal conditions for comparison. The cycle of compressorless CCGT unit was as close as possible to the Allam cycle due to the choice of parameters. The processes, in which the difference remained, were analysed. Thereafter, an analysis of how close the parameters, adopted for comparison, to optimal for the compressorless CCGT unit cycle was made. This analysis showed that these two cycles are quite close only for the production of electricity. The Allam cycle has some superiority but not indisputable. However, if cogeneration of electricity and heat is considered, the thermal efficiency of the cycle of compressorless CCGT unit will be significantly higher. Since it allows to independently regulate a number of parameters, on which the electric power, the ratio of electric and thermal power, the temperature of a working fluid at the turbine inlet depend. Thus, the optimal parameters of the thermodynamic cycle can be obtained in a wide range of operating modes of the unit with different ratios of thermal and eclectic powers. Therefore, the compressorless CCGT unit can significantly surpass the best steam turbine and combined cycle gas turbine plants in district heating system in terms of thermal efficiency. © The Authors, published by EDP Sciences, 2020