| In scramjet engines,hydrocarbon fuels are used as fuel and as heat protection coolants,that is the hydrocarbon fuel will experience two processes in the engine,the heat transfer cracking process in the engine cooling channel,and the combustion process in the combustion chamber,then in the combustion chamber combustion of hydrocarbon fuel,in fact,after the process of pyrolysis,at high temperature or mixed with a variety of small molecules.However,there is no research in the qualitative and quantitative research in this area,this paper based on this research background,two kinds of research methods through experiments and numerical simulation,to study the target fuel n-decane,different temperature and different pyrolysis degree n-decane combustion performance.In the study,the first after designed coaxial nozzle,designed diffusion transformation temperature of kerosene jet ignition experiment,based on hydrocarbon fuel cracking at the Harbin Institute of Technology Center for the study of hypersonic heat transfer platform,and the method of measuring high temperature orifice plate flow have been analyzed,and put forward a method of flame image analysis and processing.The measurement method of the flame performance parameters are introduced and the combustion performance of the theoretical analysis.At the completion of the experimental design,theoretical analysis,change the initial gas temperature control method,realize the effective control of the initial temperature of combustion gas,n-decane flame characteristics under different initial temperature were investigated,respectively on the different temperature conditions for laminar flame heat release area,diffusion angle the flame,dark bright region height ratio,analyses the flame speed and flame emission component diffusion,and the external flow conditions with flame ignition stability were studied.After the study of different degree of pyrolysis,n-decane flame heat release,diffusion angle,dark light height ratio,the diffusion speed of flue gas emissions,and compared with the flame temperature under different conditions,analysis and comparison of the different characteristics and different to the different ignition stability and cracking degree of flame at the beginning the ignition temperature of the flame stability were compared,explained the pyrolysis process for the entire flame performance advantages.Finally,based on the numerical simulation platform OpenFOAM open source,coupled with chemical reaction mechanism of n-decane combustion,to verify the accuracy of the model,different initial temperature for n-decane flame conditions and different pyrolysis degree were simulated,the internal flow field of the flame were analyzed.The reasons for improving the performance of the flame the theoretical analysis,and the whole process of path analysis,the quantitative analysis is carried out on the flame combustion efficiency theoretically.Found the increase of the initial temperature of gas and increase fuel pyrolysis rate is respectively by increasing the rate constant of the reaction process and promote the positive reaction process,increased the efficiency of the combustion process,and the increase of fuel cracking rate for combustion efficiency improvement is generally superior to the increase of the initial temperature of the fuel.Quantitative mixing of small amount of molecular fuel shows that hydrogen content is the decisive factor affecting the combustion efficiency.The higher the hydrogen content,the better the combustion efficiency. |
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