Numerical Simulation Of Bluff Body Effect On Stable Combustion Inside Burner

Since the reform and opening,the expansion of the domestic economic construction and the beginning of the various infrastructure facilities promote the rapid development of the cement industry.According to statistics,in 1978,Chinese cement output was only 65.24 million tons,while in 2005 the amount rise to 1.064 billion tons.Since 1985,the chinese cement production has been ranked 1st in the world for 21 consecutive years,and accounts for 47%of the world's cement production now.The rapid growth of cement production,basically meets the needs of Chinese large-scale economic construction.Cement,as an important basis for national economic construction raw materials,palys an irreplaceable role in the national economic development,and the infrastructure construction.Coal,as the fuel necessary for cement production,of its virous natures,heat instability,resource shortage and prices,and so on,has been seriously hampering the normal development of the cement industry,so how to reduce coal consumption and increase the calorific value of coal has become an important subject of the cement companies better,faster development.Because of the recirculation zone with intensifing mobility,stabling combustion characteristics in the tail of bluff body,this article would like to set a bluff body into the burner,and change the boundary condition to simulate the coal combustion in the burner with CFD soft,in order to understanding their movement,analysising their combustion,and correctly assessing bluff body's effect on combustion.Finally,according to simulation results,proposing a reasonable bluff body construction and boundary condition,for sake of the optimum combution.The results showed that,with the bluff body' side length gradually increasing,the length of recirculation zone firstly increases,then decrease.The angle impact on recirculation zone inform that with the blunt body angle larger,the length of recirculation zone become gradually larger.the variation range is wider in the beginning than that when angle become large.Bluff body structure can give a big impact on coal combution.The simulation show that when the vertical width of the bluff body is closed to the nozzle size,and doesn't impede fluid flow,the combustion result is advanced;while bluff body's angle also require that the vertical width of the bluff body is closed to the nozzle size.In addition,the inlet velocity should reasonable select.too low velocity,a large number of coal particles will not be transported to most of the region of the burner,make higher content near nozzle and body bluff tail,and result in hige temperature in these area.Contrastly,the hige velocity would make the coal with hige kinetic energy from the nozzle,which can break the "drag" from reciculation zone,when passing that region.So many coal partiles fast transported to the other side of the burner,can't be burnt.Stream teperature also impacts on coal combustion,the higher the temperature,the better the coal combustion.Because when the stream at lower temperatures,coal can't be ignited,coal in the unburned state.while the stream at high temperature,the temperature in recirculation zone is near the combustion',coal can be betterly warmed up,and burn ahead.