A Research On Characteristics Of Jet Plasma In Supersonic Ignition

Ramjet is a subtype of aeroengine accommodating to high altitude and high Mach number flight conditions.Ignition and combustion stability is among the core subjects while designing ramjet combustion chamber.For aeroengines,jet plasma is a new method of ignition,which is expected to solve the ignition problem of turbo-engines under extreme conditions.To solve ignition and combustion stability problems,employing jet plasma in ramjet engine is of certain research value.Taking a ramjet oriented coaxial jet plasma ignition method as the research object,this paper focused on the plasma jet for ignition and flame structure.Adopting the research method of partial decoupling,the research processes in sequence from quasi-static to transient.Research below is accomplished by experimental measurements and numerical analysis.Firstly,the process of flame kernel formation and development is analyzed in multiscale.Flow,combustion and discharge is then decoupled in local time domain and space domain of flame kernel.Experiments on the ignition characteristics of premixed methane-air by needle-electrode excited plasma were carried out in a constant volume combustion device.Secondly,the flow structure and jet plasma nuclei under supersonic coaxial jet field are studied.With computational fluid dynamics method,the patten how different jet inlet and co-flow inlet parameters influence the flow field is summarized.In addition,a digital camera was deployed.The jet plasma nuclei,whose geometric structure obviously influenced by different co-flow parameters,was then paragraphed and studied.The process of forming central flame by jet plasma igniter in supersonic coaxial jet field is then studied.Through the method of temporal decomposition,the structure model of central flame in each development stage is constructed.By extracting the structural parameters,the influence of ignition configuration parameters on structural parameters of the central flame is analyzed.Furthermore,a dynamic feedback mechanism model of supersonic ignition and steady combustion is established.The holdback in the process of supersonic ignition of coaxial jet plasma is also analyzed.Solution are put forward and specific ignition scheme is tested.