Research On Fundamental Laminar Combustion Characteristics And Reaction Kinetic Mechanism Of Innovative Carbon-Free Ammonia Fuel

With the continuous development of the economy and society,the usage of clean alternative fuels to reduce carbon emissions has become more and more significant in the research field of energy engineering.As a hydrogen energy carrier,ammonia is more economical and efficient than hydrogen in storage and transportation;while as a novel carbon-free fuel,it can participate in the combustion process for energy supply,its large-scale application contributes to the realization of carbon neutral goals.This paper carried out fundamental researches on the laminar burning velocity as well as reaction kinetics to study the combustion properties of ammonia.A self-made heat flux method testing platform was made to carry out experiments on the strechless adiabatic laminar burning velocity of various ammonia relevant fuel mixtures,with different initial temperature,equivalent ratios,and different fuel mixing ratios.The experimental results are compared with the simulation results of different reaction kinetic mechanisms,obtaining the ammonia combustion reaction process and flame structure in depth.A new mechanism was developed and validated using present experimental results and other literature combustion parameters such as ignition delay and component distribution.This study aims to deepen the understanding of the mixed combustion of ammonia and multiple fuels through the means of experiment and simulation,which will be helpful for future practical applications.First of all,facing the problem of low combustion speed of ammonia and its instability,strategies of improving the experimental system performance were proposed,as well as more advanced theoretical analyses.Using classical flame theory,a quantitative equation α_Tu⁰→Tu=（E_α）/（2R）·X+x was proposed and validated for the first time,to describe the temperature dependence coefficient α of laminar burning velocity;and a projection procedure was introduced to minimize the α uncertainty.Methods were summarized to overcome the cellular flame instability,also,the influence of the heat flux burner plate on the experiment results was quantitatively investigated.Then,the performance of the updated heat flux measurement system was validated by testing the well-investigated C1-C3/C7-C8 alkane fuels,where the over-rich phenomenon of the hydrocarbon flames was discovered and clarified.Based on the understanding of the heat flux method,the NH₃+ air laminar burning velocity was measured for the first time using the heat flux method,and through the detection of the temperature dependence coefficientα,the NH₃ over-rich phenomenon was discovered and explained for the first time.Finally,by the experimental and numerical investigations on the laminar burning velocity of ammonia with varied fuels,the effect of fuel blending was obtained,and the CEU-NH₃ mechanism was developed to reasonably reproduce the NH₃ relevant experiments in both present and literature studies.Through the analysis of the CEU-NH₃ mechanism,three reaction paths of lean,stoichiometric,and rich ammonia oxidation process are obtained;and the results at different temperatures are used to study the effect of interaction on the laminar burning velocity of NH₃ blended with multiple fuels.