The effects of hydrogen, H-2 addition and preheated reactants on bluff-body stabilized LPG-H-2 diffusion flame for two cases namely, (I) preheated air and (II) preheated air and fuel are reported in the present paper. Results confirm that the H-2 addition leads to a reduction in flame length. Besides this, the flame length is also observed to be reduced with increasing reactant temperature and lip thickness of the bluff-body. The soot free length fraction (SFLF) for both cases is observed to be increased with H-2 addition to fuel stream, which might have caused due to decrease in the C/H ratio in the flame. Interestingly, the SFLF is observed to be reduced with increasing lip thickness and reactants temperature, which can be attributed to the attenuation in induction period of soot formation and enhanced soot volume fraction, respectively. The NOx emission level is found to be decreased in coaxial burner with hydrogen addition for both case I and II. In contrast, it is observed to be enhanced in bluff-body stabilized flame. The former can be ascribed to the reduction in residence time of gas mixture, whereas the latter can be explained on the basis of enhanced flame temperature. Besides this, emission index of NOx (EINOx) is also found to be enhanced with increase in lip thickness and reactant temperature which may be caused due to both enhanced residence time and thermal effect, respectively. (c) 2009 Elsevier Ltd. All rights reserved.