Research On Coke Deposition And Convective Heat Transfer Of Supercritical Pressure Hydrocarbon Fuels In Porous Media

The front of hypersonic vehicles and fuel injector struts of scramjet engine will suffer extremely high temperature as well as high heat flux working conditions.The transpiration-cooling technology which uses supercritical pressure endothermic hydrocarbon fuels as coolant is one of key thermal protection methods to keep the heated parts under good protection.So the research on heat transfer performance and coke deposition characteristics of hydrocarbon fuels in porous media plays a very important role for the design of transpiration-cooling structure of hypersonic vehicles.Considering the safety of hydrocarbon fuels as coolant,n-decane and a kind of engineered fuel were used as working fluids to study the coke deposition characteristics of hydrocarbon fuel in bronze porous media by weighing the mass of coke.The influences of fluid temperature,mass flow rate and inlet pressure were discussed,and the results showed the following points.The fluid temperature was a dominant factor of coke generated from hydrocarbon fuel.Two types of coking behaviors including thermal-oxidative coking and pyrolysis coking were observed,which led to the coke surface deposition rate showing a double-peak curve.At a certain temperature,the mass flow rate determined the residence time of the fluid in porous channels.Thermal-oxidative coking was limited by the residence time and the dissolved oxygen concentration,so the coke surface deposition rate increased at first and then decreased with the mass flow rate increased.However,pyrolysis coking was only affected by the residence time,so the coke surface deposition rate monotonously decreased with the mass flow rate increased.Elevating pressure could effectively inhibit the coking products generated from n-decane,thus the coke surface deposition rate in porous media reduced.Considering the heat transfer performance of hydrocarbon fuel as coolant,the local thermal non-equilibrium(LTNE)model and lumped parameter method were used to study the heat transfer rules of supercritical pressure n-decane in bronze porous media.Similarly,the affections of fluid temperature,mass flow rate and inlet pressure were studied,and the influence mechanisms were explained by fluid properties changing and turbulence i ntensity.Finally,according to the experimental data,a correlation was proposed to describe the n-decane convective heat transfer in porous media at supercritical pressure in the range of experimental conditions.