Experimental Investigation on flame stability of Ammonia-LPG Flames

NH3 as an alternate fuel is gaining huge importance in the recent past owing to the urgency to mitigate global warming caused by conventional hydrocarbon fuels.However, NH3 because of its low laminar flame speed and reactivity when compared to those of conventional hydrocarbon fuels, needs to be blended with conventional fuels for it to be a viable alternative.In this paper, NH3 in various proportions is blended with LPG.Experiments are conducted using a single slot burner of 17.3 mm inner diameter for different combinations of parameters like (i) mixing ratios of NH3 and LPG in fuel mixture, (ii) low power ratings (0.1 to 1.1 kW) and (iii) percentages of partial premixing with air (0% to 30%).Analysis of varying the aforementioned parameters is done using flame photographs and trends in flame length data.This is followed by a stability map for different configurations which divides the flames into different regimes of (A) steady flames, (B) stable flames with oscillating tip, (C) flames with vortex shedding, and (D) unstable flames with lift-off.An increase in partial premixing is observed to have a stabilising effect (making flames transition from the regime of vortex shedding to that with oscillating tips) whereas an increase in power rating has the opposite effect.It is found that increase in partial premixing shortens the average flame length whereas increase in power rating has the opposite effect.Stable and steady flames are observed with either lower percentage of partial premixing coupled with higher concentrations of NH3 or higher percentage of partial premixing coupled with lower concentrations of NH3.Additionally, the effect of increasing NH3 volume fractions in the fuel mixture on adiabatic flame temperature, NO, CO and CO2 production is also studied using equilibrium calculations and the results are reported.