| As a clean and renewable emerging fuel,hydrogen energy has very broad application prospects in the fields of fuel cells,gas turbines,hydrogen energy vehicles,and aerospace.The research on the combustion characteristics of hydrogen has attracted the attention of many domestic and foreign experts.Hydrogen has the advantages of good combustion performance,high heat release rate,large flammable range,and can achieve lean combustion,but it also has shortcomings such as flammability and explosion,especially its high adiabatic temperature during combustion Medium nitrogen is oxidized at high temperature to form nitrogen oxides,causing serious environmental pollution.Therefore,it is of great significance to study the characteristics of hydrogen combustion and NO generation to realize the efficient and low-polluting combustion of hydrogen,and to optimize the design and operation of combustion equipment.In this paper,the eddy dissipation concept combustion model of finite rate reaction is used to couple the 18-component 43-step H2-N2-CO2 reaction mechanism model,and the accuracy of the simulation is verified by the hydrogen combustion data of the German Aerospace Center(DLR).(initial temperature of air,initial temperature of fuel,air inlet velocity,and fuel inlet velocity)and the hydrogen-air diffusion combustion process under dilution conditions(type of diluent and dilution rate)were numerically calculated to explore the effect of inlet parameters and dilution conditions on hydrogen-air diffusion combustion.Influence law of NO generation characteristics in air diffusion combustion.The main research work is as follows:(1)The ANSYS Fluent simulation software is used to numerically simulate the hydrogen-air combustion process under different inlet parameters.The results show that increasing the initial temperature of the air and the initial temperature of the fuel can both increase the peak temperature and NO generation on the central axis of the flame;With the increase of the inlet velocity,the peak flame temperature increases gradually,and the amount of NO generation increases,but with the increase of the fuel inlet velocity,the peak flame temperature decreases,and the amount of NO generation also decreases.(2)The hydrogen combustion process under different diluents(N2,CO2)and dilution rates was studied,and it was found that the addition of diluents N2 and CO2 could reduce the combustion temperature of hydrogen to a certain extent,and at the same time could effectively inhibit the generation of NO,and With the increase of the flame peak temperature,the NO formation concentration gradually increases;compared with the diluent N2,CO2 has a better effect on reducing the hydrogen combustion temperature and inhibiting the NO formation.(3)The effects of the diluents N2 and CO2 on the hydrogen combustion temperature and NO generation are non-linear.With the increase of the dilution rate,the effect of the diluent on reducing the hydrogen combustion temperature is gradually enhanced,while the inhibitory effect on NO generation is gradually weakened;when N2 When the dilution rate is 0.5 and the CO2 dilution rate is 0.3,the concentration of NO can be maintained at a low level while the hydrogen combustion maintains a relatively high temperature,which is conducive to the realization of high-efficiency and low-pollution combustion of hydrogen.(4)The average reaction rate analysis of NO generation pathways showed that the reactions N+OH?NO+H,NO2+O?NO+O2 and NO2+H ?NO+OH were the main reactions that dominated NO generation,while the reactions N+NO? N2+O,NO+HO2?NO2+OH and NO+O+M?NO2+M are the main consumption paths of NO. |
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