Design And Simulation Of Experimental Device For Convective Heat Transfer And Pressure Loss Of Metal Foam

As aerospace aircraft continue to evolve toward higher performance,conventional thermal cycling is limited by material performance,and the relative lifting space is already small.Therefore,people are paying more and more attention to complex thermal cycles such as intercooling and regenerative cycles.In the ground and marine gas turbines,it has been proved that the use of intercooled regenerative cycles can greatly improve engine power and reduce fuel consumption.In the intercooling and regenerative cycle,heat exchangers such as intercoolers and regenerators are the key components.Unlike ground and marine gas turbines,heat exchange equipment on aerospace engines needs to be more stable,compact,efficient,lightweight,and long lasting.Through research,it is found that the open-cell foam metal material has the advantages of good heat transfer,low density,high strength and easy machining,and is suitable for manufacturing a compact heat exchanger on an aeroengine.Firstly,this paper has studied the domestic heat transfer wind tunnel test bench by reading relevant literatures at home and abroad,and designed a foam metal heat transfer wind tunnel test bench that can meet the requirements of high temperature and high flow rate of aeroengine.The inlet speed is not less than 70 m/s,the inlet pressure is about 1.0 MPa,and the heating temperature is not lower than 200 °C.The experimental bench can conduct a mechanism study on the convective heat transfer of foam metal materials,and explore the influence of the relevant parameters of foam metal on its convective heat transfer.Secondly,the X-ray CT machine is used to realize the three-dimensional scanning and digital reconstruction of the micro-scale pore structure of foam metal materials.Combined with electron microscopy,the characteristic parameters of foam metal are extracted and the pore structure characteristics are analyzed.A tetrahedral structure was constructed by using Surface Evolver software.By optimizing the tetradecahedral structure,a new type of tetradecahedral model was proposed.By comparing with the research results of other scholars,the rationality of the model is proved.At the same time,this paper uses Fluent software to simulate the convective heat transfer of foam metal at the pore scale,and studies the influence of key parameters of foam metal on its heat transfer and resistance characteristics.By analyzing the temperature field,velocity field and pressure field in the foam metal channel at the pore scale,the influence of the microstructure of the foam metal on the heat transfer characteristics and the resistance characteristics is more intuitively obtained.Finally,this paper analyzes the influence of characteristic parameters such as pore density and porosity of foam metal on heat transfer characteristics and resistance characteristics.The main conclusions are as follows: When the pore density is the same,the porosity is larger,the convective heat transfer coefficient is larger,unit pressure When the porosity is the same,the larger the pore density,the larger the convective heat transfer coefficient and the larger the pressure drop per unit length.At the same time,as the flow velocity of the fluid increases,the convective heat transfer coefficient and the unit pressure drop increase.By introducing j/f as a comprehensive performance evaluation index,it is concluded that the larger the pore density and porosity of the foamed metal,the larger the comprehensive performance evaluation factor j/f,and the better the comprehensive heat transfer performance.Under the conditions of overall pressure loss,foam metal materials with relatively high pore density and porosity are more suitable for making compact heat exchangers.