The Study Of Hydrogen-air And Methane-air Premixed Flame Propagation And Pressure Oscillation In The Duct

Hydrogen has a wide prospect as a kind of new energy, so the research of hydrogen/air premixed gases combustion and explosion properties is imperative. Gas explosion is one of the disasters in coal mine production, and many domestic and foreign scholars for its research have made certain progress in recent years. In the paper,studied the hydrogen/air and methane/air premixed explosion characteristics in different ducts for providing theoretical guidance of grasping the gas flame propagation law,explosion pressure change rule, controlling and reducing the damage of explosion.The experimental platform with three square cross-section ducts with a length of1000 mm is designed and set up, and explosion characteristics, tulip formation mechanism and the influence of the pressure oscillation.were studied in three aspects of the shape of flame front, the flame propagation speed, the explosion pressure. The experiments of hydrogen/air premixed gases explosion were conducted under hydrogen volume fraction of 20%, 25%, 30%,40% in three ducts. The experimental results show that explosion characteristics had big difference with different hydrogen volume fraction in the same duct. The flame propagation speed had declining stage under tulip flame conditions, and the pressure wave strongly oscillated between positive values and negative values. The premixed flame shape and propagation speed were different with the same hydrogen volume fraction in different duct. The thinner the duct is, the easier the tulip flame will form,and the more front the forming position of tulip flame. Regardless of the size of hydrogen volume fraction and duct cross-section, the flame propagation speed was closely related to the change process of flame shape. There were maximum flame propagation speed and explosion pressure peak value in the duct with middle cross-section size.The methane/air premixed explosion characteristic was researched with the methane volume fraction of 8%, 9%, 9.5%, 10%. The premixed flame propagation characteristic was different with the same hydrogen volume fraction in different duct.The methane volume fraction had a great influence on flame propagation characteristic especially the formation of tulip flame. The flame propagation speed had rising again stage under tulip flame conditions. The flame propagation characteristicwas closelyrelated to the explosion pressure, and the size of cross-section had a great influence on the value of explosion pressure. There were maximum flame propagation speed and explosion pressure peak value in the duct with middle cross-section size. Compared and analysis the difference between the influence of section to the hydrogen/air premixed explosion and the influence of section to the methane/air premixed explosion, and this showed that there were the same influence law between them. The section of duct effected the flame shape in propagation process, propagation speed and explosion pressure. Compared with the thinnest duct and the thickest duct, the maximum flame propagation speed and pressure appeared in the duct with middle cross-section size.Finally, premixed flame propagation and pressure variation rule were studied in detail under the condition of the tulip flame formation, and analyzed the formation reasons of tulip flame and negative pressure, and the reason of the pressure oscillation.Based on the mechanisms of combustible gas/air premixed flame dynamics and pressure, studied the scale effects on premixed flame and pressure of hydrogen/ air and of methane /air. This has certain help for safety utilization of hydrogen energy and perfecting the theory of preventing gas explosion.