Experiment And Numerical Simulation Of NO Generation Characteristics Of Ammonia Premixed Flame

In order to meet the demand of chemical energy storage,NH₃ has been emphasized as a substitute for H₂.NH₃ has the advantages of high energy density,octane number,easy compression storage and transportation,and combustion without CO2 production.It is a high-power fuel with wide application prospects.For ammonia utilization,a very important problem is the emission of pollutants from combustion to produce NO.In this paper,the NO generation characteristics of ammonia premix flame are studied experimentally and numerically.An ammonia premix flame test bench was designed and constructed.Aiming at the characteristics of low propagation speed and low calorific value of ammonia flame,a burner structure and ignition process were designed to realize ignition.Through this test bench,stable and repeatable ammonia premix flame could be obtained.The rule of ammonia combustion pollutant formation was studied on this experimental bench,and the emission rule and reason under different conditions were obtained.In this paper,ammonia premix combustion is studied,and its pollutant NO generation is mainly concerned.The product measurement and simulation calculation of ammonia air premix flame with equivalent ratio of 0.7-1.0 and oxygen concentration of 24%/26%/28% were carried out on the independently designed experimental bench.In the experiment,MRU Vario Plus flue gas analyzer was used to measure the concentration of NO and residual O2 in flue gas products.The paper compared the two most common mechanisms used in the study of ammonia combustion,as well as two special mechanisms to compare the atmospheric combustion of ammonia,through different mechanisms to evaluate the accuracy of the prediction.According to the experimental results in this paper,Konnov mechanism and M&G Scheme have a good prediction effect on the formation of NO products under experimental conditions.NO products of ammonia premix flame are greatly affected by heat dissipation.In the case of Bunsen burner in this paper,NO generation has a peak value near the equivalent ratio of 0.9,while NO production rapidly drops to an extremely low value within the range of 0.9 to 1.0.The decrease of NO formation concentration under low equivalent is on the one hand due to the dilution effect of air and on the other hand due to the change of reaction.For the two most common mechanisms,GRI3.0 mechanism and Konnov mechanism,the results were analyzed through detailed analysis of mechanism paths,and qualitative speculation was made on the use of mechanisms in a wider range based on the results.The above two mechanisms are respectively represented as simplified and more comprehensive mechanisms.Through ROP analysis,the reaction path diagrams of GRI3.0 mechanism and Konnov mechanism were drawn.The path diagram and sensitivity analysis indicated that the change of NO formation concentration was caused by the change of internal primitive reaction.In this paper,NO generation in pure ammonia premix combustion is studied,and the results can be used to guide the optimization design of relevant combustion system,which makes a certain contribution to the advancement of ammonia energy storage technology.