| Electrogasdynamic(EGD)power generation is an approach to directly convert the thermal energy into electricity.Due to the advantages of simple structure,no mechanical moving parts,low maintenance requirement and strong adaptability to heat source,it has a great development potential and most likely to become one of the new generation technologies with high efficiency,low carbon and environmental protection.But an EGD converter not only has a coupling of flow field,particle field and electrostatic field,but also with an interaction between working gas flow and charged particle movement.It is a typical multi-field coupled two-phase flow of gas and charged particle.A comprehensive and detail analysis of the characteristics of the two-phase flow in the EGD power converter and law of power conversion and its influence factor,which can provide a theoretical basis and foundation for improving the energy conversion efficiency and its wide application.At present,the research of EGD power generation is still in the stage of basic theory research and model test.A lot of complex physical phenomena and technical problems are required to be solved.In order to deeply understand the various physical processes and phenomena in the EGD power converter and improve the cycle efficiency,the Brayton cycle with an EGD power converter is studied through theoretical analysis in this paper.A multi-field coupled two-phase flow of gas and charged particle in the EGD power converter is numerical simulated by using the software of computational fluid dynamics.An regeneration thermodynamic cycle integrating with an EGD converter with heat addition is established and analyzed.Two-phase flow of gas and charged particle and heat transfer characteristics in the process of EGD power conversion with heat addition are explored.the feasibility to increase the power conversion efficiency through gas expansion with heat addition is demonstrated.The main studies and conclusions in this paper are as follows:(1)Based on the thermodynamics theory,the thermodynamic process of the Brayton cycle integrating with an EGD power converter is analyzed theoretically.it is proved that adding heat into the flow process of the EGD converter can improve the cycle thermal efficiency theoretically.The theoretical calculation formula of the cycle integrating with an EGD power converter is established,and the influence of the working gas parameters and the performance of each component of the circulating system on the cycle thermal efficiency is analyzed.The results show that the performance of the regenerator has a great influence on the performance of the whole cycle.For a smaller pressure ratio,the higher cycle thermal efficiency can be attained with an excellent regenerator.When the pressure ratio is larger than the one corresponding to the maximum work output,one excellent regenerator leads to the smaller cycle efficiency.The cycle power efficiency can be effectively improved by increasing the generator power conversion efficiency or reducing the cycle pressure ratio.Compared to the compressor,the performance of the generator has a greater impact on the performance of the cycle.The difference can be reduced by improving the performance of the regenerator.(2)For the characteristics of the two-phase complex flow of gas and charged particle with coupling effect of flow field,particle field and electrostatic field in the EGD power converter,the charge transmission characteristics and the variation of the gas performance parameters are simulation studied by using CFD software FLUENT.The contrast analysis of the difference between the adiabatic flow and the non-adiabatic flow caused by heat addition in the EGD power conversion process is given.The influence of different method of heat addition and different regions with heat addition on the gas and charged particle movement is discussed.The simulation results show that the shock wave has a significant influence on the gas acceleration and the particle velocity in the EGD power converter.The added heat is converted into the internal energy and kinetic energy of the gas,so the speed of the particle is increased,then more power is exported.Increasing the particle flux on the one hand will increase the charge density,on the other hand,it will reduce the particle velocity.For a given boundary condition,there is a maximum value of the output current.Compared to the whole converter heated,adding heat in the converging section of the converter makes more heat convert into the kinetic energy of the gas,so increasing the speed of the particle.By wall heat conduction,only the velocity and temperature of the gas in the vicinity of the wall increased.The heat is hardly transferred to the mainstream.However,by internal heating the gas velocity and temperature are increased in the whole converter and the speed of the particle is enhanced.(3)The physical process of two-phase flow of gas and charged particle with multi-field coupled in the EGD power converter numerically calculated by using two fluid model.The effects of different particle parameters and heat addition on the two phase flow are studied.It is found that more gas internal energy can be converted into the kinetic energy of the particle with the particle volume fraction increased,and thus more energy can be output.The sound velocity of two-phase is obviously lower than that of single phase gas.The sound velocity of two-phase decreases with the volume fraction increased.In addition,the particle volume fraction has a significant influence on the electric field strength in the EGD power converter.The volume fraction is limited by the electric breakdown strength of the EGD converter.Decreasing the particle diameter and increasing the particle inlet temperature can increase the output current.The gas velocity and gas temperature in the whole converter are increased by adding heat into the power conversion process.The increase of the gas internal energy and the output current is more obvious when the particle inlet temperature is higher.(4)An regeneration thermodynamic cycle integrating with an EGD converter with heat addition is established.Based on gas parameter of the numerical simulation results,The effects of heat addition and different heat addition method on the cycle thermal efficiency are analyzed.The results show that the cycle net work and thermal cycle efficiency increased with the inlet temperature increased.By adding heat into the EGD converter,the cycle thermal efficiency can be significantly enhanced.Moreover,the cycle thermal efficiency increases with the increase in the amount of heat addition.Compared to the wall heat conduction,Internal heating is proved to more significantly enhance the cycle thermal efficiency.Adding heat in the converging section of the converter and improving the charged particle inlet temperature can more significantly increase the cycle net work and thermal efficiency. |
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