Experimental investigation of flammability limits and flame characteristics of LPG–H₂ mixtures at various equivalence ratios via image processing techniques

Authors : Kamil Mutlu, Ömer Çam

Pages : 1649-1666

Doi:10.58559/ijes.1810265

View : 46 | Download : 189

Publication Date : 2025-12-29

Article Type : Research Paper

Abstract :In combustion systems, determining the flammability limits of the fuel–air mixture to be used, or establishing the conditions that enable combustion within the desired limits, is of critical importance. By doing so, instabilities that may occur in the system can be minimized, and operational safety can be ensured. In the present study, the flammability limits and instantaneous flame images of premixed burners were experimentally investigated as a function of the amount of H₂ added to pure LPG. The H₂ content was increased up to 80%, while the swirl number and thermal power were kept constant at 1 and 4 kW, respectively, under all experimental conditions. Instantaneous flame images were taken at different equivalence ratios at 0.1 intervals below stoichiometric conditions and at 0.2 intervals above stoichiometric conditions. Flame brightness and RGB (red-green-blue) values were evaluated quantitatively in detail by image processing with HSV and grayscale detection methods using MATLAB. For 100% LPG, the stable flammability limits are ϕ=0.8–2.8, while with hydrogen enrichment the lower flammability limit expands to ϕ=0.4, and the upper flammability limit decreases to ϕ=2.0 (for 20% LPG–80% H₂). The results revealed that hydrogen addition significantly affects the LPG flame behavior, alters the stable flammability limits, and increases flame brightness up to ϕ=1.6.
Keywords : LPG, Hydrogen, Flammability limits, Instantaneous flame images, MATLAB, Image processing

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