Nozzle Flow With Heat Addition And Cycle Efficiency Analysis Of The Electrogasdynamic

Electrogasdynamic (EGD) power conversion is a process that convertsthermal(internal/kinetic) energy directly into electric energy. The EGD system use gasas work fluid, with the advantages of non-polluting, simplifying equipment, compactand low maintenance requirements. It can be used as distributed energy system, withgreat potential for development. In order to improve the thermal efficiency, the gas flowin the nozzle of the regenerative Brayton cycle is heated for the heat addition in theexpansion process of gas. A new thermodynamic model was constructed. The flowfields and cycle efficiency with heat adding on the nozzle was studied.Firstly, the flat Laval nozzle for the EGD converter was designed. The nozzle flowfield of different type line was compared, then nozzle velocity coefficient and energyloss coefficient were calculated according to the CFD simulation results. The best typeline nozzle was selected. Then, the nozzle flow with heat addition was studied by CFDsimulation. Different heating methods were studied in this paper. With the factors ofdifferent heat power, different flow channel thickness, flow deflectors, heating atdifferent locations, extension of the diverging sections, extension of the convergingsection, different inlet height, the nozzle flow with heat addition on the wall was studied.The methods to improve the effect of heat addition was found, and the nozzle wasoptimized. Further, the flow fields and exergy efficiency of wall heating and inner heatsource was compared. A method of combination heat addition of wall heating and innerheat source of the nozzle was found according to the effect of heating at differentlocations. Finally, the influence of different heating power to the thermal efficiency wasanalyzed. A method to improve the thermal efficiency of EGD was proposed. The cycleefficiency with different gas inlet temperature, minimum cycle temperature, gas inletpressure with heat addition on the nozzle was calculated.The results show that compared to the linear nozzle, the nozzle with twoarc-tangent type profile has better performance for the acceleration of gas. The nozzlewith the narrower channel could increase the gas velocity, however, it can also increasethe flow resistance and result in velocity decreasing. While the nozzle with flowdeflectors and extension of the diverging sections can increase the heating power, it canalso increase the flow resistance and result in velocity decreasing. The nozzle with thelonger converging section and higher entrance with a constant flux can effectively increase the flow velocity and temperature of the gas. Heat addition through nozzle wallhas a little impact on gas velocity and temperature in the regions around the centerlinedue to the effect of boundary layer. Whereas the inner heat source heating cansignificantly increase the gas velocity and temperature of nozzle central region. Thecombination heat addition of wall heating and inner heat source of the nozzle caneffectively improve the cycle efficiency. With heat addition on the nozzle gas, cycleefficiency was improved with different gas inlet temperature, minimum cycletemperature, gas inlet pressure.