Structure Design And Performance Experiment Of High-temperature-resistant Liquid Metal Frequency Selective Surface

With the development of aerospace technology,the outside surface temperature of the craft with supersonic and hypersonic flight in the atmosphere rises sharply under the effect of air viscous retardation,The traditional structural materials can not bear too high thermal load,which leads to the risk of ablation on the aircraft,and surface thermal properties and fluidity of liquid metal good provides a solution for it.Frequency Selective surfaces is a periodic array of space electromagnetic wave filter,which selectively reflect or transmit electromagnetic waves of specific bands to change the transmission properties of electromagnetic wave.The reconfigurable FSS can be designed by taking advantage of the excellent conductivity and fluidity of liquid metals to meet the needs of aircraft stealth.Aims at the requirements of high temperature resistance and stealth of hypersonic vehicle,based on the low melting point,high boiling point,high thermal conductivity and good fluidity of liquid metal,a design scheme of high temperature resistant multi-band FSS with liquid metal as circulating cooling medium is proposed.In this scheme,liquid metal is passed into a high temperature resistant medium cavity with a certain shape element to form FSS,and circulates and flows in the cavity to dissipate heat on the high temperature surface.At the same time,by building multi-layer FSS cavity with different shape units,and relying on the regulation of external valves,liquid metal flow into the corresponding cavity layer is controlled according to the frequency band demand,so as to realize the multi-band switch of FSS and achieve the purpose of frequency reconfiguration.The main work is divided into the following aspects:First of all,on the basis of summarizing the current research on FSS at home and abroad,a new design scheme of reconfigurable high temperature resistant FSS based on liquid metal is proposed.According to the theory of FSS,two kinds of single-layer FSS structures,cross shape and Y shape,were designed,and the electromagnetic performance was simulated and analyzed.The sensitivity analysis of the structural parameters was used to optimize the design of single-layer FSS,and it was proved that it was feasible to construct FSS with non-metallic material cavity and liquid metal.Second,the multi-layer FSS is studied based on the adjusted single-layer FSS model,The two unit structures were superimposed to design the reconfigurable double-layer FSS in the C-and Ku-bands,and the sensitivity analysis of all structural parameters was made in the two bands respectively to adjust the double-layer FSS structure.The real object was processed for experiments,which verified the feasibility of the reconfigurable FSS scheme based on liquid metal.Finally,a Y-shaped FSS model was used to study the cooling effect of circulating liquid metal into the cavity of FSS medium.The effects of inlet velocity,liquid channel height and other structural parameters on heat dissipation performance are analyzed.A heat dissipation experiment platform was set up to conduct heat dissipation experiments under two working conditions of air burning and liquid metal cooling.The simulation results are compared with the experimental results,which verifies the correctness of the simulation,and also shows that the liquid metal FSS has a good heat dissipation performance.