Investigation Of The Physical And Chemical Effects Of Diluent Gas N₂/CO₂/Ar On Premixed Laminar Flame Velocity Of Methane

As the energy crisis,emissions,and oil dependence on foreign sources have become increasingly prominent,energy conservation and emission reduction are urgently needed.As an alternative fuel for efficient and clean combustion,methane has very promising application prospects.Methane combustion often needs to be combined with diluent gas.Researchers have studied the effect of diluent gas on the laminar flame velocity of methane premixed combustion.The effect is mainly divided into physical effects and chemical effect.The physical effects can be divided into dilution effect and thermal effect.However,the current research still has problems such as less research on the influence of the three effects,lack of study on the parameters of thermal effect and experimental study on chemical effect.Therefore,this thesis mainly conducts research on these aspects,and uses non-dilution and physical effect to replace thermal effect.The main research content and research results are as follows.In this thesis,the laminar flame velocity of diluted premixed methane is studied with three typical diluent gases as the research object.The results show that the addition of CO₂/N₂/Ar always leads to a decrease in the laminar flame velocity.Under the same working conditions,the corresponding laminar flame velocity of each diluent gas is always CO₂<N₂<Ar.The chemical effect of Ar and N₂ is negligible.The three effects of CO₂ all lead to the decrease of laminar flame speed.When the dilution rate increases,the proportion of the dilution effect increases,while the proportion of non-dilution and physical effect does not change significantly,and that of chemical effect decreases.When the equivalence ratio increases,the proportion of the physical effects all first decrease and then increase,and that of chemical effect first increases and then decreases.The non-dilution and physical effect of Ar causes the laminar flame velocity to rise.The chemical effect of CO₂ has the most significant inhibitory effect on R99:OH+CO<=>H+CO2,which promotes the laminar flame velocity.The mole fraction of H and OH radicals are positively correlated with the laminar flame velocity,and their variation trends are also consistent with the laminar flame velocity under the influence of diluent gas.This thesis presents a method to simulate the effects of various parameters on non-dilution and physical effect.The results show that the specific heat capacity in the thermodynamic parameters,the potential well depth and the collision diameter in the transport parameters are negatively related to the laminar flame velocity,and the third-body effect of CO₂ causes the laminar flame velocity to decrease,while that of Ar causes the increase.The results of decoupling research show that there is no effective coupling effect between the main physical parameters and parameter effects.The specific heat capacity accounting for about 90%is the main factor causing the non-dilution and physical effect,but the influence of other parameters accounting for about 10%cannot be ignored.This thesis presents compensation and double-balance experiment schemes to study the chemical effect of CO₂.The corresponding experiment and simulation results show that the two schemes have good applicability under various working conditions.Two experiment schemes are given to calculate the relevant experiment conditions according to the CO₂dilution rate to be studied.The analysis results of sensitivity and the mole fraction of radicals further verify the feasibility of the two schemes.The changing trend of H and OH confirms the theoretical principles of the two schemes.