Effects Of Partial Premixing On The Combustion Characteristic And NO Production In Methanol/Dimethyl Ether Counterflow Flames

With the rapid development of China's auto industry,it has caused a series of energy shortages and increased pollution emissions.The search for more efficient and clean alternative fuels is the need of current economic development.Alcohol ether binary fuel has become the focus of extensive research as a traditional fossil fuel and combustion additive.At present,there are few basic researches on the combined application of alcohol ether fuel,and it is necessary to carry out the binary combination combustion technology of alcohol ether fuel.In this study,the current advanced combustion method,part premixed hedging flame,was used to combine the reaction kinetics from the perspective of combustion.The combustion characteristics and NO emission index of different side premixed hedging flames were analyzed,and it is hoped that the alcohol ether blending combustion can be improved.Theoretical basis research.Based on the OPPDIF module in the large gas phase dynamics software CHEMKIN,the simulation of the hedging flame is carried out.The combustion characteristics and NO generation of the methanol/dimethyl ether hedging flame are studied by solving the premixed laminar flame model of different sides.The study defined the premixed methanol and dimethyl ether hedging flame as the A series flame,and defined the pre-mixed dimethyl ether and methanol hedging flame as the B series flame.The theoretical data of the basic flame temperature,basic flame structure,heat release rate analysis,fuel and key free radical concentration distribution,and NO formation mechanism in the combustion process were analyzed.The results show that no matter which flame mode increases with the premixed equivalence ratio,the flame changes from a single flame structure to a double flame structure.This feature becomes more significant as the premixing equivalent increases;the maximum flame temperature rises.The heat release rate of the flame increased in different degrees in the non-premixed zone and the premixed zone,and the reason was related to the concentration of internal free radicals H,O,OH and CH₃.Both the premixed equivalence ratio and the flame pull rate affect the structure of the flame,which is manifested in the combination and separation between the double flame reaction zones.The flame thickness is also one of the ways to characterize this trend.Whether it is A or B series flame,NO mainly produces non-premixed reaction zone from flame through thermal,transient and NO reburning mechanism;with the introduction of premixing,the N₂O mechanism of NO in premixed reaction zone will be obviously excited.However,the net production rate has not increased significantly.The NO peak concentration and the maximum production rate of the two types of flames A and B decreased with the increase of the premixed equivalence ratio,but the NO accumulation amount and the NO emission factor showed different trends.The effect of flame stretching on the NO formation of the two types of flames is consistent,and the NO formation of the A B flame decreases as the flame stretch increases.