Study On Flame Propagation And Explosion Suppression Characteristics Of Methane In A Visualizedized Airtight Pipeline

With the progress of society,the development of industry and the improvement of people’s livehood,clean energy has been widely used.As a main component of coalbed methane,natural gas and other high-quality clean energy,the study of its explosive properties and safety research has great significance.The use of visualized square airtight pipeline and schlieren/high-speed photography techniques to study the flame propagation process of methane explosion and the propagation process of carbon dioxide to methane flame suppression.The results of research as follows:(1)The existing visualized square airtight pipeline and experimental methods in the laboratory are improved,and the air tightness and the precision of the air intake were greatly improved.(2)Using visual square airtight pipeline and high speed photography to studied 5.5%,7.5%,9.5%,13.5% and 14.5% volume fraction of methane/air premixed gas explosion flame propagation and pressure,by the mean time,9.5% volume fraction of methane/air premixed gas explosion flame microstructure was studied by the schlieren/high-speed photography.The results shows that the explosive pressure increases first and then decreases with increasing methane volume fraction.The flame propagation velocity increased first and then decreased,and fluctuated at the end of the propagation.(3)No matter the methane volume fraction was 5.5% or 14.5%,"semi-flat flame" was appeared.The "double tulip flame" appeared at the later stage of flame propagation.(4)Methane-air premixed gas with a volume fraction of methane of 9.5% was selected as the research object and ignited concentration of 3%,6%,9%,12%,15% and 18% carbon dioxide to analyzing pressure data,speed curve,the results shows: The explosive pressure decreased with the volume fraction of carbon dioxide increased,and the flame propagation speed tendeds to decrease.Analysis of the schlieren/high-speed photographic images shows: In all experiments,the phenomenon of "semi-flat flame" appeared in the later stage of flame propagation.In each group which carbon dioxide volume fraction was less than 18%,"quasi-planar flame" was formed in the middle of flame propagation and the "Tulip flame" structure was formed in the mid-and-late flame front,the "Double Tulip" phenomenon appeared on the front of the flame front at a carbon dioxide volume fraction of 6%.When the volume fraction of carbon dioxide reached to 12% and 15%,the flame front formed a phenomenon of "double half-plane flame".When the volume fraction of carbon dioxide reached to 18%,the phenomenon of "Tulip flame" disappeared from the flame front.When the carbon dioxide concentration reached to 20%,the premixed gas reached the extinguishing point,the explosion was suppressed.(5)During the propagation of methane/air premixed gas and its suppression flame,the tulip flame appears,the premixed gas flame begins to change from laminar combustion to turbulent combustion,and the forward structure transformation of flame front starts from the edge of flame(small size eddy appears),and spreads to the entire front(cell like structure).