Effects Of Water Vapor Addition On The Pyrolysis And Combustion Characteristics Of Ethanol Fuel

Knock has become the major obstacle for futher increasing the thermal efficiency of conventional engine.The view is widely accepted that bio-alcohols and water mixed combustion can effectively reduce the tendency of knock in engine.Compared with other bio-alcohol,ethanol is easier to produce and has lower boiling point,better water solubility.The production and storage of ethanol is relatively difficult.Therefore,wet ethanol is gradually becoming a research hotspot for conventional engine alternative fuels.However,modeling studies and experiment on the ethanol mixed with water are still not comprehensive enough.Therefore,the effects of water vapor addition on the pyrolysis and combustion characteristics of ethanol fuel were studied in this work.This paper investigated the change of the mole fraction of the components after pyrolysis of water addition on ethanol through experiments in the plug flow reaction,and analyzed the effect of adding water on the pyrolysis process of ethanol;Based on decoupling method,the effects of 10%water vapor on the flame properties and soot formation characteristics and the effects of 40%water vapor in ethanol flame on the macro characteristics of ethanol flame in an ethanol/air coflow laminar diffusion flame at atmospheric pressure by using Co Flame program.The results show that,compared with ethanol pyrolysis,the addition of water reduces the production of CO and CH₄ in the reaction,but also increases the production of C₂H₄.With the blending of water vapor,the peak temperature of the flame and the maximum soot volume fraction reduce.The water vapor influence flame properties and soot formation through dilution effect,chemical effect,thermal effect and radiation effect.The chemical effect and dilution effect play dominate roles.The chemical effect affect the O,H,H₂and OH radicals mole fraction,and the increase of OH radical enhance the oxidation of soot.The chemical effect also influence the intermediates of soot formation,such as benzene?A1?,pyrene?A4?,C₃H₃ and C₂H₂,then reduce the rate of soot nucleation and surface growth.40%water vapor addition in the ethanol flame,affects the laminar combustion velocity of the premixed flame and the ignition delay of the ethanol flame through density effect,transport effect,thermodynamic effect and chemical effect.The chemical effect of water vapor affect the mole fraction of CO,CO₂,OH and other components.The increase of OH mole fraction promotes the shortening of the ignition delay period.