Thesis (PH.D.) - Cairo University - Faculty Of Engineering - Department Of Mechanical Power Engineering

AIn radiant burners , the flame stability plays a much significant roleEffects of Flame speed , excess air ratio , and firing rate on the flame stability were investigatedCombustion characteristics and stability of premixed LPG - air mixture in a porous media radiant burner are studied experimentallyAl2O3 and SiC were used as porous media in this workThe main objective behind this study is to determine factors affecting the flame stability and to develop empirical correlations for combustion characteristics and flame stability limits in porous media An apparatus was built and measurements under steady state conditions were carried outExperiments are conducted for different firing rates and excess air ratios , as well as for two different thermal properties of the porous medias and two different porous layer thicknessesseries of tests had been conducted and the data are presented Results indicate that when a reaction front is stabilized within porous medium , flame characteristics are quite different from those of a free flameThe location of the flame front is influenced by the excess air ratio and firing rateFor rich fuel mixtures , flame is located above burner surface , while for lean fuel mixtures the flame is either embedded within the porous layer or located close to the surface It has been confirmed that the solid thermal conductivity plays a significant role in the flame stabilization in porous mediaCompared with free flames ; the higher heat transfer leads to a faster flame propagation , which hampers flame stabilization in porous media Heat dissipation , which depends on material properties , affects both flame position and propagationnalysis of measurements made it possible to determine flame location in porous media for different excess air ratios and firing ratesFor Al2O3 flame is usually stabilized at the middle of the porous layer

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