Abstract:

In order to reduce gas explosion accidents during the production, transportation and storage of combustible gases in industrial sites, square pipes of 200 mm×200 mm×35 m and round pipes of 90 mm diameter and 10 m length were independently constructed. Under the same initial conditions, the explosion test of methane/air premixed gas with volume fraction of 9.5% was carried out, and it was studied with pressure and flame sensors. The results show that the evolution process of the wave system in two kinds of pipes with different scales and cross sections is the same. After ignition, the flame changes from layer to turbulent flow, and the acceleration of flame leads to the compression wave chasing each other, finally forming a strong shock wave. The changing trend of flame speed in the two long straight pipes is the same, and they both experience the process of acceleration-deceleration-re-acceleration-re-deceleration, with the maximum flame speed in the square tube and round tube reaching 69 and 35.7 m/s respectively. After the first compression wave reflects off the wall, the pressure rises to 117% and 114%. When the reflected wave is coupled with the flame front, the flame speed in the large-scale pipeline is reduced to 73%, and that in the small pipeline is reduced to 93%. Under the same volume fraction, the maximum overpressure values of the first compression wave in the two long straight spaces are similar, which are about 65.45 and 67.09 kPa.

Key words: long straight pipe, premixed gas, detonation, evolution of wave system, pressure wave