Experimental investigation of laminar LPG–H2 jet diffusion flame

This paper presents an experimental investigation of the effect of hydrogen addition on flame length, soot free length fraction (SFLF), and emission level in LPG–H2 hybrid fuel jet diffusion flame. Result shows that the addition of H2 upto 20% does not exhibit any change in the flame length. However, when hydrogen level is varied from 20% to 40%, a reduction in flame length is observed which may be attributed to the enhanced diffusivity caused due to the increased gas temperature. It is also observed that the SFLF increases as H2 is added to fuel stream. This might have caused due to the reduction in the C/H ratio in the flame which is favorable to attenuate PAH formation rate. Moreover, the reduction in radiant fraction with hydrogen addition is pertinent with the reduction in soot concentration level. Besides this, the decrease in NOxNOx emission level with H2 addition to the fuel stream is also observed. This can be ascribed to the enhanced flame temperature and diffusivity with hydrogen addition which results in an increase in gas velocity from burner rim to flame tip and hence leads to a decrease in residence time of the gases. The emission level of CO is observed to be enhanced with hydrogen addition. In contrast, the emission index of CO2 is seen to be reduced. This can be attributed to reduction in the residence time with hydrogen addition which leads to inhibit the conversion of CO to CO2 and thus results in decreased CO2 and enhanced CO concentration levels.