Experimental and numerical studies on characteristics of LPG-air premixed flames in curved tube

Abstract

Liquefied Petroleum Gas (LPG) is the widely used fuel worldwide from residential to industrial applications, and thus largely meets the energy demand of various systems. The present study experimentally and numerically investigates the flame propagation behavior of LPG- air mixture in straight and curved tube with inner diameter 30 mm, a length of 500 mm for straight tube and a chord length of 500 mm for the curved tube. Numerical study has been carried out using ANSYS Fluent with FGM approach for modelling of combustion. The premixed reactant in the equivalence range of 0.3 ≤ φ ≤ 2.7 is supplied through the closed end of the tube and the mixture is ignited at the open end exposed to atmosphere. Different flame regimes are observed for 30 mm diameter combustor tube, like the self- repetitive extinction and re-ignition flame, forced repetitive extinction and re-ignition flames, cellular flames, blow out flames, stretched or slanted flames. The curvature of the tube was found to enhance the instabilities occurring in the flame, but rapid changing of flame speed towards the cold inlet is not observed in curved tubes. Cellular flames were formed in the curved combustor as a result of secondary flow and thermal-diffusive instability. Curvature in the combustor tubes induces cross stream vortices in the flow due to the secondary flow, which influence the flame structure in the fuel rich regime of the mixture.