ENHANCEMENT OF FLAMMABILITY LIMITS OF THE NATURAL GAS BY THE USE OF BLUFF BODY

Abstract

An experimental investigation has been carried out to study flammability limits of the natural gas and the effect of flame holder position, in the burner tube, on it. These tests employed two shapes of bluff body: disk and cone (600 included angle) with blockage ratio of 0.42. The fuel used was natural gas and the upstream air velocity was varied up to 26 m/s. The flame holder location was varied from 12 mm inside the burner tube, with respect to the burner mouth, to 12 mm downstream and outside it (hid from -0.44 to +0.44). The results showed that the flammability limits are widened due to the use of bluff body and it depends largely on the flame holder shape and position in the burner tube. The results showed also that the best position of the flame holder is not the same for all shapes of the bluff bodies, but it depends on the shape of the flame holder and on the nature of study (lean limit or rich limit). For the lean limit of flammability, it is concluded that the best position of the flame stabilizer is at 6 mm inside the burner tube (hid = -0.22) for disk bluff body and 12 mm outside it (hid = 0.44) for the conical one. For the rich limit the best position is 6mm outside (hid = 0.22) for disk and 12mm outside also (hid = 0.44) for cone.