Research On The Comparation Of The Explosive Characteristics Of Methane Under The Open And Silent Condition

Flammable gas explosion is considered to be one of the main forms of explosion. Theseexplosions occurred in the underground tunnels of coal mines, in the pipes or containers, andsteam cloud explosions within the factory boundary, all belong to the typical gas explosion.Most of these explosions are not occurred in the airtight container but in the open spaces.Meanwhile, domestic and foreign researches of methane explosion characteristics are mostlycarried on in confined spaces, therefore, it is very important to compare methane explosioncharacteristics in both open and confined spaces during the research.Using horizontal pipe gas-dust explosion experimental appliance, a contrast experimentresearch was conducted to compare methane explosion characteristics between in open andclosed spaces. The main content includes: methane explosive limit, the influence posed onexplosion characteristics by different content of methane, the varying trend of explosionpressure and flam propagation velocity along the pipe and the influence of exist obstacles,then compared the explosion characteristics in open and closed spaces, the result are asfollows:1. In open space, the explosion limits of CH4 are between 5.5% to 15.5% , while inclosed space, the limits are 4.5% to 15%, the up and low limits in open space are a little bithigher than in closed space;2. The influence of methane content on its explosion characteristics is basically the sameboth in open and closed space, which means when the content of methane reaches 10%, itsexplosion pressure and the rising rate of the pressure reaches its summit, leading to theshortest time to reaches the maximum explosion pressure; when the methane content is moreor less than 10%, the pressure and rising rate both slows down and extend the time to reachesits maximum explosion pressure accordingly;3. The varying trends of explosion pressure along the pipe are different between open and closed space: in open space, regardless of the existence of obstacles, the maximumexplosion pressure and the maximum rising rate of it first increases then decreases within thedistance between test point and ignition end, the time to reach maximum explosion pressureincreases gradually and the points where the maximum pressure and rising rate occur arebasically the same; while in closed space, when there is no obstacle, the maximum explosionpressure and the maximum rising rate of the pressure increases according to the increasingdistance between test point and ignition end; when obstacles are placed, this trend changes tofirst decreases then increases and the decreasing point is the first test point right after theshock wave over the obstacle.4. In open and closed spaces, the flame propagation velocity varies: in the formercondition, the flame propagation velocity along the pipe gradually increases while theexistence of obstacle obviously promote its propagation; in the latter condition, the flamepropagation velocity along the pipe gradually decreases, though obstacles did promote itspropagation but the extent is smaller.5. In open space, the obstacle posed obvious influence on flame propagation velocity butbarely on pressure; while in closed space, the influence on both the velocity and pressure areobvious by obstacles.