Experimental Study on Gas Explosion in an Obstructed Confined Pipe

The acceleration of flame inside a pipe is a complex phenomenon involving several variables including fuel nature, mixture composition and geometrical characteristics of the pipe itself such as length, wall roughness or presence of obstacles.  It has been well known that the obstacles in pipes and long ducts would accelerate the flame propagation, and cause the transition from deflagration to detonation. This work sought to evaluate the magnitude of the hydrocarbon-air mixtures explosion using 90-degree pipe and T-junction configuration as a full bore obstacle condition. The experimental work was performed in a confined pipe of 0.42 m3 volume, giving  a length to diameter ratio (L/D) of 51. Hydrogen, propane and natural gas-air mixtures were used in this work with equivalence ratio (Φ) ranges between 0.5 to 2.0. The experimental results show that explosion characteristics depended on the carbon content, the layout of obstacles, and the content of argon and nitrogen as an inhibitor. It can be seen from the experimental results that a highest overpressure was observed at a slight above to all fuel-air mixtures as compared to stoichiometric.  In addition, records of pressure traces showed a substantial rise to the pressure downstream of the pipe, known as retonation and this phenomenon is discussed.