| Abstract |
The considerable increase in energy demand, the strengthened requirements of new emission norms and the limited fuel resources are the major challenges for researchers over the world. The use of biodiesel produced from waste cooking oil is a promising solution. In the current study, the transesterification process used to convert waste cooking oil into a Waste Cooking Oil Methyl Ester (WCOME) has been modified and the production time is reduced with the help of ultrasonication. Then extensive study on combustor cold flow as well as flame characteristics had been carried out. In the first set of experiments, the study compares the cold flow conditions (air), flame structure, combustion, and emission of Jet A-1 via the use of two swirl burners having different configurations and identical geometric swirl number (SN=0.55). The first configuration is a typical High Swirl Burner (HSB) with a central bluff body while the second one is a Low Swirl Burner (LSB) with central perforated plate allows relatively axial flow to pass through the burner center.
In the second set of experiments, the study identifies the effect of biodiesel blending ratio within mixtures of biodiesel/Jet A-1 fuel burned in a confined combustor on the flame characteristics and exhaust emissions. The Jet A-1 fuel is blended with WCOME with volume fraction of 5, 10, 15 and 20%, symbolized as B5, B10, B15, and B20 respectively. For all tested cases the Lean Pre-vaporized Premixed (LPP) turbulent flames are examined keeping the same equivalence ratio φ = 0.75 and the temperature of premixed fuel/air mixtures entering the combustion chamber at 250 °C. The main results indicated that the flow field of the LSB is free of a central recirculation zone while HSB has a large central recirculation region. The lean pre-vaporized premixed Jet A-1 and air can sustain steady combustion at HSB and LSB with comparable global combustion quality. The HSB can generate an attached blue cone-shaped flame while the LSB can generate a blue lift-off “W” type flame. The HSB flame temperature distribution shows a high-temperature zone at the burner edge which represent a hot spot region while the LSB shows a more uniform flame temperature distribution. The CO and NOx concentrations of the HSB through the flame are approximately 50 % higher than those for LSB. The local flame temperature distribution of the biodiesel/Jet A-1 fuel shows a similar behavior like that of Jet A-1. Biodiesel (oxygenated fuel) addition to Jet A-1 has a great effect on the emission characteristics of LPP combustion. There was remarkable emissions reduction due to biodiesel blending, the maximum reduction in CO was achieved for B20 as 30% lower than Jet A-1 and the maximum reduction for NOx was achieved at B5 as 45% lower than Jet A-1. The Jet A-1 fuel can be replaced by biodiesel/Jet A-1 fuel without any modifications in the combustor design as they have similar temperature distribution and great emission reduction.
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