Study On The Explosion Characteristics And Influencing Factors Of Ammonia/Methanol/Air

Energy shortages and environmental pollution have become major issues globally,necessitating the adoption of clean alternative fuels to reduce carbon emissions.As a zero-carbon fuel,ammonia has been receiving increasing attention.Methanol,one of the representatives of clean alternative fuels,can improve the combustion performance of ammonia when blended with it.As these two fuels are flammable and explosive which can lead to fire and explosion accidents when mixed,the study of the explosion hazard of ammonia/methanol mixtures is of great significance for the safe application of clean energy.This paper investigated the explosion hazard of ammonia/methanol mixtures based on a 5 L spherical explosion experimental system with the equivalence ratio of 0.7-1.7,the methanol content of 0.2-1.0,the initial pressure of 50 kPa-100 kPa and initial temperature of 298 K-348 K.The results show that with the increase of equivalence ratio,the maximum explosion pressure and the maximum rate of pressure rise first increase and then decrease,while the explosion heat loss shows the opposite variation.The addition of methanol significantly increases the maximum explosion pressure and the maximum rate of pressure rise,while reducing the heat loss.As the initial pressure increases,the maximum explosion pressure,the maximum rate of pressure rise and the heat loss increase.As the initial temperature increases,the maximum explosion pressure and heat loss decrease,while the maximum rate of pressure rise does not change significantly.The prediction model for the explosion pressure parameters was established by the support vector regression algorithm,and the prediction performance model was improved by combining an evolutionary algorithm to optimize the hyperparameters.The results show that the GA-SVR and DE-SVR models are applicable to the prediction of maximum explosion pressure and maximum rate of pressure rise,respectively.The kinetic characteristics of the ammonia/methanol/air explosion were analyzed by numerical calculations.The results show that the smooth flame model underestimates the maximum pressure rise rate due to the neglect of flame instability.As the methanol content increases,the flame instability is more remarkable.This is attributed to the joint effect of increased hydrodynamic instability and decreased diffusive-thermal instability.The increase of initial pressure results in the increase of flame instability,mainly due to the increase of hydrodynamic instability.The increase of initial temperature has no significant effect on the flame instability.The net heat release rate of the ammonia/methanol mixture gradually increases with increasing methanol content,initial pressure and initial temperature.The reactions OH+H2<=>H+H2O,HO2+H<=>20H,CO+OH<=>CO2+H and NH3+ OH=NH2+H2O are the main exothermic reactions during the explosion,while the reaction H+O2<=>O+OH is always the most important endothermal reaction.The chemical effect has the largest contributions to the accelerated flame propagation on the lean and stoichiometric side,while the contributions of thermal and transport effects are dominant on the rich side.As the initial pressure increases,the chemical effect of methanol decreases,the thermal effect increases and the transport effect does not change significantly.As the initial temperature increases,the chemical effect of methanol increases,the thermal effect decreases and the transport effect changes insignificantly.