Study On Instability And Cell Characteristics Of Spherical Expansion Flame With Hydrogen-rich Combustion

Spherical expansion flame has always been a very important research direction in the field of combustion research.A large number of studies have found that after the spherical expansion flame develops to a certain scale,the surface will gradually produce cell-like cracks.When the jellified cracks fill the surface of the flame,the flame will be unstable overall,and then the flame speed will increase significantly.The degree of cell surface of the flame surface is obviously improved.After a period,the degree of cell surface morphogenesis and the growth rate of flame speed are slowed down.The research on the spherical expansion flame of hydrogen is mostly concentrated under the condition of dilute hydrogen combustion.In order to study the spherical expansion flame of hydrogen more comprehensively,the instability and cytification of the spherical expansion flame of hydrogen under the condition of rich hydrogen combustion(Le_eff>1)are studied.In view of the fact that the previous studies have less quantitative evaluation of the spherical expansion flame instability and cell characteristics,this paper uses image recognition program to identify the spherical expansion flame profile and surface cracks,while changing the equivalence ratio and initial pressure,using a series of indicators such as flame speed,critical jellification radius,total length of flame surface crack and average flame cell radius are combined to analyze the typical development process of spherical expansion flame,and the spherical expansion flame is explored at different equivalence ratios（1.0,1.2,1.4,1.6）and initial pressure（5 bar,8 bar,10 bar,12bar）.What are the changes in instability and cell characteristics.The test results show that whether the spherical expansion flame is unstable or not will affect its flame speed.The average flame speed of the spherical flame expansion flame is much smaller than that of the unstable spherical expansion flame,and the flame speed increases slowly without self-acceleration and oscillation.The increase of the equivalence ratio can significantly inhibit the instability of the spherical expansion flame,the total length of the flame surface crack is reduced,and the average flame cell radius is significantly increased.Large,when the equivalent ratio is greater than 1.2,the flame speed is also slowed down;increasing the initial pressure can significantly promote the instability of the spherical expansion flame,the total length of the flame surface crack increases,the average flame cell radius is significantly reduced,and the flame speed monotonously increases.However,the Pellet number at the critical cell radius R_c only changes with the equivalent ratio,independent of the initial pressure.