Experimental Study on the Effect of Air Pollution Caused by Methane-Air Deflagration Characteristics

Abstract

In order to study the effect of combustible gas cloud releasing from FPSO upper deck facilities deflagration characteristics on air pollution, a semi-open open test pipe system was built. By changing the initial conditions such as the obstacles length, distance between obstacles, section shape of obstacles and pipe system structure, the flame propagation mechanism and overpressure changing rules of methane / air deflagration were analyzed. As a result of that, the degree of sufficiency of methane combustion was analyzed, which could be seen as air pollution level. With the increase of the length of obstacle and decrease of the distance between obstacles, the induced turbulence increased, the compression effect of unburned gas became stronger, the combustion of combustible gas became more intense and sufficient, and the flame propagation speed and the maximum overpressure increased. The effect of square cross section was more obvious on inducing turbulence than that of rectangular cross section and circular cross section. The flame front was divided into many small flames by the pipe structure obstacle, and the flame front showed as a `spiny` shape. Under the effect of �spiny� flame, the methane combustion was more sufficient, and the maximum overpressure value was 3.1 times of the circular section obstacle condition. In conclusion, as the methane-air deflagration becoming more serious, although the overpressure and flame speed would be higher and the extent of damage to the surrounding facilities would be more serious, the air pollution causing by unburned gas would abate.