| Aviation kerosene is an important coolant in aero-engines,and the study of it s thermophysical propert ies is of great significance t o the development and safety of aerospace engines.Due t o the limit ation of the act ual working condit ions and experiment al cond itions of the fuel oil,sufficient thermal physical propert y data of the fuel oil cannot be obtained.The complex composit ion of aviat ion kerosene w ill lead to excessive computat ional cost of numerical calculat ion.Theref ore,an alt ernative model is proposed t o simplify the composit ion of aviation kerosene.Since n-decane,n-dodecane and 1,2,4-t rimet hylbenzene and their mixtures are often used as alternat ive fuels for RP-3 aviat ion kerosene,t his paper present s the follow ing two alternat ive models:(1)n-dodecane and 1,2,4-t rimet hylbenzene;(2)n-dodecane and n-dodecane for simulation study.The main findings are as follows:(1)Three pure subst ances,n-decane,n-dodecane and 1,2,4-trimet hylbenzene,were simulated and st udied,and a three-dimensional model was est ablished,and the Tra PPE-UA force field was used for molecular dynamics(MD)simulation,respect ively.Three t hermal propert ies of thermal conduct ivity,densit y and thermal diffusivity w ere simulated,and the simulat io n result s were compared wit h NIST data.The average absolute relative deviation of each item was less than 5%.(2)The tw o alt ernative models combined the two substances in proport ions of88.7% and 11.3%.Molecular dynamics simulat ions were carried out on t he tw o models t o study t he variation trend of the density of t he two models wit h temperature under sub/supercrit ic al pressure.The simulation result s at the three pressures w ere compared wit h NIST values and experiment al values,all errors were less t han 8%,both alternat ive mode ls could provide reasonable alternat ive accuracy for predicting the density characterist ics of aviation kerosene RP-3.(3)The t rend s of t hermal conduct ivity w it h t emperature f or t he two models under sub/supercrit ical pressure were invest igat ed.The t herma l conduct ivity result s at t he three pressures were compared w ith the NIST and experiment al values,and all errors w ere less than 5.5%.Both alternat ive models can provide reasonable alt ernatives for predict ing the thermal conduct ivity propert ies of aviat io n kerosene RP-3 precision.The average accuracy per pressure of the f irst alt ernat ive model is higher than that of the second model.(4)The densit y and thermal conduct ivit y of the two surrogate models w ere calculat ed using theoret ical formulas,and the th eoret ical values w ere compared with t he NIST dat a.The average error of the densit y was large,and the densit y propert ies of the surrogat e model could not be accurately pred ict ed;in terms of thermal conductivity,although t he simulat ion result s show similar accuracy,but the error w ill increase w ith the increase of pressure,so t he molecular dynamics method can show better prediction effect than the theoretical formula.(5)B y means of radial distribut ion funct ion,mean square displacement,self-diffusion coefficient,average end-to-end distance and angular distribut ion funct ion,the thermophysical mechanism and the microst ructure inside t he molecule were stud ied in t he first model.It is found that w ith the increase of temperat ure,the volume of the system increases gradually,the density of t he syst em decreases,and the spacing between each molecule also increases.It was also found that the n-decane chain cont ract s and twists w ith increasing t emperature,explaining the mechanism of t he thermal conduct ivity of alt ernative fuels chang ing wit h temperature,w hich cont ributes to a better understand ing of the thermophysical properties of aviation fuels. |
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