Experimental Research On The Flame Propagation And Combustion Characteristics Of Wheat Starch Dust

A high concentration of grain dust in the process of grain production and shipment has great potential danger in the process of explosion,which causes serious threat to grain and food processing.The flame propagation characteristics of wheat starch and oxidized characteristic mechanism were revealed.It try to provide scientific basis for safety production and strong guarantee to reduce the incidence of grain dust explosion accidents.This article focuses on wheat starch and studies its flame propagation characteristics and oxidation characteristics mechanism.An experimental system for dust cloud flame propagation characteristics established.Combining with the high-speed photography,superfine thermocouple and ion probe measurement techniques,the effects of particle size and concentration on dust flame propagation characteristics were explored.And combustion characteristics mechanism of wheat starch were investigated to further discuss its influence by thermal analysis technique,as follows:(1)According to flame images,flame frontal shape changes from the irregular to rules in the flame propagation process.When dust cloud concentration is low,the flame front shape discrete.With the increasing of dust cloud concentration frontal shape gradually tends to be more smooth.And luminous intensity of fire also gradually increase.Furthermore,the time of flame full of the entire pipeline is decreased first and then increased.When dust particle size is larger,the continuity of the flame propagation images is increased with the decreasing of the particle size.Serious fault occurs when the particle size is less than 30 microns.(2)In the process of flame propagation,the flame propagation velocity increases with the increasing of concentration at lower dust cloud concentration.Flame propagation speed reaches the maximum value when the concentration of dust cloud is 0.610 kg/m~3(the particle size distribution is 30-74microns),then flame propagation speed slowly decreases with the increasing concentration of dust cloud.Dust flame propagation velocity increases with the decreasing of the dust particle size.(3)The maximum flame temperature in the process of flame propagation increases first and then decreases with the increasing of the dust cloud concentration.When the dust concentration is 0.610 kg/m~3(the particle size distribution is30-74microns),the flame temperature peak reaches 998.3?.Under different cloud of dust concentration,the maximum flame temperature and flame propagation speed have the same change trend.And there exists a linear relation between the maximum flame temperature and flame propagation speed.Heat transfer dominates in the process of flame propagation.(4)The different particle sizes of wheat starch was studied by thermal analyzer.The particle size has a great influence on the combustion characteristics of wheat starch.The particle size of dust is smaller,the water precipitation temperature is lower.The maximum thermal decomposition rate moves towards the low temperature.With the decreasing of the dust particle,the ignition temperature,activation energy and the thickness of preheat zone were decreasing.The particle size of wheat starch is smaller,the wheat starch is more combustible.