Numerical Simulation Of The Gasoline Combustion In Porous Media

Porous media combustion is a novel combustion type.It has many advantages in gas fuel combustion,and it is widely used in the combustion of liquid fuels.However,studies on the evaporation and combustion characteristics of liquid fuels in porous media are not yet clear.In this paper,evaporation and combustion mathematical models of liquid in porous media are established by simplifying the novel type of porous burner for liquid fuels.Based on the simulation platform of fluent,the characteristics of evaporation,temperature profiles and pollutant profiles of gasoline in porous burner were studied in detail by numerical simulation of the combustion process,which is in a new type of porous burner for liquid fuel.The results provide the theoretical basis for further research on the combustion of liquid fuels in porous media.Evaporation and combustion mathematical models of liquid in porous media are established.95# gasoline as the fuel,the numerical simulation introduced detailed chemical reaction thermodynamic data.With the gas as a continuous phase,the governing equation of Euler coordinates is solved.The standard k-? turbulence model is used to describe the gas-phase turbulence process of the combustion.And diffusion combustion process of gasoline is treated with the non-premixed combustion model of mean mixture factions/PDF.By taking the droplets of gasoline as the discrete phase,the trajectories and velocities of the droplets can be traced by solving the equilibrium of force and the motion of the droplets equations in a Lagrange reference frame.And the evaporation process of droplets is described by the heat and mass transfer equations(single-tempreture equations).On this basis,a user-defined scalar(UDS)was used to establish the solid-phase energy equation,and a user-defined function(UDF)was used to modify the gas-phase energy equation,and a model of double-temperature energy equations was established in order to further analyze the influence difference on evaporation process of gasoline droplets to Solution.Simulation results were validated with the experimental results of temperature for checking the model.The evaporation and combustion characteristics of gasoline in porous media are studied.Firstly,the characteristics of evaporation,combustion temperature profiles and pollutant profiles of gasoline in porous media are analyzed.The effects of air-fuel ratio,droplet diameter of atomized gasoline and spray cone angles on the characteristics of evaporation and profiles of temperature and pollutant are also studied.The results show that diameter of the atomized droplets expect the spray cone angle has significant effects on the evaporation area and evaporation rate.The influence of the air-fuel ratio and the diameter of the atomized droplets on the combustion temperature profiles are obvious,and the maximum temperature decreases with the increase of air-fuel ratio.The molar concentration(average value)of pollutant CO at the outlet of porous burner gradually decreases with the increase of air-fuel ratio,and all variables have little effect on the concentration of CO2 at the outlet.Combustion flame and gas solid temperature distribution of gasoline in porous media are studied.Considering the gas-solid heat transfer,a model of double-temperature equations is established to analyze the characteristics of gas-solid temperature profile.The influence of gas-solid heat transfer on evaporation,combustion temperature and pollutant profile are analyzed by comparing the simulation results of models of single and double temperature equations.The temperature of solid shows obvious two-dimensional profile in porous media.In the upstream of the flame surface,the temperature of the solid-phase is gradually higher than that of the gas-phase in the axial direction,and the heat of solid-phase transfers to the gas-phase.The temperature of the gas-phase in the downstream of the flame surface and the heat recovery zone is higher than the solid-phase,and the heat of gas-phase transfers to the solid-phase.The solid-phase temperature in the vicinity of the wall is higher than the gas-phase,and the heat loss on the wall has little effect on the temperature of solid–phase.In the downstream of the flame surface,the temperature of gas-solid phase has a small decrease process,the decline trends gradually waning along the radial direction,and the temperature no longer decreases near the wall.The heat transfer between gas and solid phase has a certain inflence on the evaporation process and tempreture profile,but has little effect on the pollutions.