Experimental And Simulation Research On Flameless Combustion Of Gas Fuels Under Un-preheating Conditions

In order to meet the needs of energy saving and emission reduction,the industry requires heating furnaces to improve combustion thermal efficiency and reduce pollutant emissions.Flameless combustion technology has the characteristics of high combustion thermal efficiency and low pollutant emissions,which has attracted the attention of many experts and scholars.In the past,flameless combustion technology required preheating of fuel or air,which was not conducive to the industrial promotion of flameless combustion.In this study,the flameless combustion of the fuel without preheating was realized in laboratory experiments based on the following two points:the first point is that the furnace needs to be fully heated during the realization of flameless combustion,so that the internal working temperature of the furnace is higher than the spontaneous combustion of combustibles;the second point is to use a non-premixed flameless burner to enhance the jet flow at the nozzle outlet through a smaller nozzle inlet aperture,so as to achieve the effect that the flame front is completely blown away by the outlet jet.In this thesis,the effects of different fuels,different incident diameters and different incident angles on the realization of flameless combustion are explored by combining experiments and numerical simulations.,the main research results are as follows:During the experiment,when the flammable combustion state changed to the flameless combustion state,the working temperature in the furnace required for different fuels to achieve flameless combustion was different.When propane is used,the working temperature in the furnace must be greater than 923 K.When the flame state reaches the state of flameless combustion,the temperature fluctuation in the furnace is significantly reduced compared with the traditional flameless combustion,and the emission level of pollutants is also significantly reduced.Methane flameless combustion has smaller temperature fluctuations and pollutants than propane flameless combustion.The emission level is lower,and it is easier to achieve a flameless combustion state.The detailed chemical reaction mechanism is used to numerically simulate flameless combustion under non-preheating conditions.The simulation results show that increasing the inclination angle of the burner inlet or reducing the diameter of the burner inlet can improve the circulation rate of flue gas inside the furnace and make the temperature inside the furnace higher.The distribution is more uniform and the pollutant content at the tail of the furnace is significantly reduced,both of which are conducive to the realization of flameless combustion.During the flameless combustion simulation process,OH radicals and H₂CO radicals have a good correlation with the heat release region of the reaction,and it can also be found that there is a positive correlation between the Reynolds number and the internal circulation rate of the flue gas.A summary analysis of the data and experimental data shows that the burner has a critical Reynolds number.At present,the conditions required for flameless combustion in industrial applications are relatively harsh.In order to simplify the process flow of flameless combustion technology,this thesis attempts to achieve flameless combustion without fuel or air preheating,Industrial progress and application have certain scientific significance.