Study On The Influence Of Ignition Position On The Explosion Characteristics Of Premixed Syngas In Tube

With the gradual depletion of traditional energy sources and the growing problem of environmental pollution,the demand for green energy sources has gradually increased in the course of economic development.Syngas with H₂ and CO as the main components is receiving more and more attention as a clean energy source.Compared with traditional energy sources,syngas has a wide range of sources,and syngas is more environmentally friendly in the application process.However,syngas,as a combustible gas,is prone to combustion and explosion accidents when it is exposed to ignition source in the constrained space once the syngas leaks in the application process due to the special properties of its main components H₂ and CO.In this study,the self-designed and self-built small-sized experimental platform was used to study the explosion characteristics of premixed gas in closed and half-open tubes.At the same time,the explosion characteristics of the premixed syngas with different hydrogen volume fraction(?)and different initial equivalence ratio(?)in the half-open tube at different ignition positions were studied.When conducting experiments on the effects of different ignition positions on the explosion characteristics of premixed syngas,three ignition positions are arranged on the axis of the tube.Ignition position 1 is located in the center of the closed end(intake end).Ignition position 2 is located in the middle of the pipe,and ignition position 3 is located 100 mm from the open end.The experimental results show that the explosion characteristics of premixed syngas in closed and half-open tubes are obviously different.A classic tulip flame can be observed in a half-open tube when??50%.In the closed tube,the classical tulip flame was formed under all working conditions.At a certain hydrogen fraction,the distorted tulip flame structure can be formed in both half-open and closed tubes.Both flame propagation velocity and explosion overpressure increased with the increase of hydrogen fraction.When?<50%,increasing the hydrogen fraction in the premixed syngas has an obvious effect on increasing the flame propagation velocity and the peak value of explosion overpressure.When??50%,the effect of adding hydrogen on the flame propagation velocity and the peak value of overpressure is weak.The ignition position and the hydrogen fraction affect the syngas explosion characteristics,and the same law appears under the three equivalent ratios of?=0.8,?=1.0 and?=1.2.When ignited at ignition position 1,the premixed flame formed a classic tulip flame when??30%,and a distorted tulip flame was formed when?=0.8,??30%and?=1.0,??30%.When ignited at ignition position 2,the flames propagating to the closed end all formed distorted tulip flames,but there was a significant gap with the formation process of distorted tulip flames at ignition position 1.With a certain hydrogen volume,the flame propagates fastest at the ignition position 1,and the overpressure oscillation becomes more obvious as the ignition position is close to the open end.At the same ignition position,the propagation velocity of premixed flame increases with the increase of the hydrogen volume.At ignition position 2 and ignition position 3,the shock of overpressure is more severe.With the increase of hydrogen volume fraction,the shock of overpressure shows two different trends.When the hydrogen fraction is constant(?=50%),the ignition position and equivalent ratio affect the explosion characteristics of the premixed syngas.When firing at ignition position 1,a classic tulip flame was formed when??1.6,and a distorted tulip flame was formed under the conditions of??2.When firing in ignition position 2,the flame propagating to the right of the ignition position only experienced spherical and finger flames,and the flame propagating to the left of the ignition position formed a distorted tulip flame.When igniting at ignition position 3,after the flame forms a flat flame,the flame front oscillates and propagates in an inclined manner toward the closed end.In ignition position 2 and ignition position 3,when the overpressure reaches the first peak,there will be a severe shock.In most operating conditions,the overpressure usually reaches the shock peak within the first oscillation cycle.And the amplitude of the overpressure shock has no obvious regularity.However,when ignited at the ignition position 3,the amplitude of the overpressure shock gradually increases in a sinusoidal manner under the conditions of?=1.0,?=2.5,and?=3.0.