Numerical Simulation Of Cold Spray Of Dimethyl Ether And N-heptane Under Supercritical Conditions

In order to explore the influence of turbulence model and the gas equation of state on the numerical simulation of supercritical spray,the supercritical fluid spray experiments of dimethyl ether and n-heptane were carried out for numerical simulation.Numerical simulation study on supercritical fluid spray of dimethyl ether.Coupled with KH-RT breakup model,RANS and LES turbulence models were used to simulate DME supercritical non-combustion spray experiment respectively.Applicability of two turbulence models was discussed,and the developing processes of DME subcritical spray and isooctane and n-heptane supercritical spray were also studied,serving as contrasts.Meanwhile,based on LES turbulence model,ambient temperature and pressure as well as spray pressure and temperature on the penetration distance of DME supercritical spray were analyzed.The results show that both RANS and LES models can simulate DME supercritical spray very well while the results of LES model are in better agreement with experimental observations.The atomization effect of DME supercritical spray prevails over that of DME subcritical spray and that of isooctane and n-heptane supercritical spray in the same initial conditions.The spray penetration distance and radial diffusion increases as the ambient temperature,fuel temperature and injection pressure rise,but decreases as the ambient pressure rises.About numerical simulation of n-heptane supercritical spray,Euler-Lagrange and Euler-Euler methods are used to simulate the supercritical spray experiment of n-heptane.Coupled with the turbulence model,The real gas equation of state was used to simulate n-heptane supercritical spray process.The simulation results were compared and analyzed from temperature,mass fraction and density distribution.The results show that under supercritical conditions,the temperature increases with the increase of the axial and radial distance,and the mass fraction and density decrease with the increase of axial and radial distance.Compared with the change of temperature,mass fraction and density,it is found that there are three zones in the spray atomization process under supercritical conditions,namely,the liquid core region in the center layer,the gas liquid mixing layer in the middle layer and the outermost gas layer.Under the KH-RT model,it is further proved that the LES model is more suitable under supercritical conditions.In supercritical condition,the simulation results of PR equation are better than those of SRK and RK equation.