| Impinging streams have significantly enhanced the atomization and combustion process of liquid fuels.However,due to their complexity,so far,the key factors affecting the spray impact combustion process and the formation of NO_x have not been reported.Therefore,based on theoretical analysis and numerical simulation,the NO_x of coaxial jet impinging combustion,reverse jet spray combustion and combustion process can be studied by establishing a comprehensive model considering droplet collision and subsequent development,droplet evaporation process and gas phase combustion reaction process.By comparing and analyzing the characteristics of spray impingement combustion in various forms,the variation and distribution of heat flow field in combustion chamber under different conditions were studied,and the strengthening mechanism of the impinging stream on the spray combustion process and the formation of NO_x were revealed,which is of guiding significance to the application and optimization of the impinging stream spray combustion in the industrial process.It can be seen from numerical simulation that the impinging stream has a certain enhancement effect on the combustion process of coaxial jet impinging combustion and reverse jet spray combustion.Compared with single nozzle jet combustion,the temperature of coaxial jet spray combustion increased by 100K.In coaxial spray impinging combustion,with the increase of gas velocity,fuel mass flow at the nozzle inlet,the angle of two nozzle and the number of fuel carbon atoms,the combustion intensity in the impinging area is enhanced,resulting in a high temperature difference of 100K~500K.With the increase of the distance between the two nozzles,the combustion enhancement effect in the impingement zone first increases and then decreases.In reverse jet spray combustion,the reverse spray combustion of pneumatic atomization is higher than the pressure type 300K.Among them,with the increase of gas velocity difference between two nozzles,the mass flow rate of fuel at the nozzle inlet and the distance between the two nozzles,the combustion effect in the impingement zone first increases and then decreases.On the basis of previous combustion simulation results,the effect of different flow field structure on the formation and emission of nitrogen oxides in the process of coaxial jet impinging combustion and reverse jet spray combustion is studied.It is found that with the increase of inlet gas velocity,nozzle angle and velocity difference between two sides,the rate of thermal NO_x and fast NO_x formation increases.With the increase of nozzle spacing,the formation rate of thermodynamic and fast NO_x decreases,and the emission of NO_x at the exit decreases. |
