Emission characteristics of methanol-in-canola oil emulsions in a combustion chamber
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This paper focuses on the emulsification and combustion characteristics of different methanol-in-canola oil blends subject to different conditions including swirl number and equivalence ratio. Exhaust emissions data such as nitrogen oxides (NOx), unburned hydrocarbons (UHC's), carbon monoxide (CO) and carbon dioxide (CO2) emission levels were measured and analyzed thoroughly. Stable methanol-in-canola oil emulsions were made by using a combination of Span 80 and Tween 80 surfactants. The three different fuels studied were; pure canola oil, 89-9 emulsion [9% methanol - in - 89% canola oil emulsion with 2% surfactant (w/w)] and 85-12.5 emulsion [12.5% methanol - in - 85% canola oil emulsion with 2.5% surfactant (w/w)]. All the experiments were conducted in a 30 kW combustion chamber equipped with a twin fluid atomizer and a radial vane swirler. The swirler vanes were positioned at 60 and 51 angles (with respect to vertical axis) in order to achieve swirl numbers (SNs) of 1.40 and 1.0, respectively. The fuels were tested at equivalence ratios of 0.83, 0.91, 1.0, 1.05 and 1.11. Ultimate analysis, higher heating value (HHV), kinematic viscosity and density were used to characterize the fuel properties. Experimental results showed that fuel type and swirl number had a major influence on emission levels. All the emulsions produced lower NOx, CO and unburned hydrocarbon emissions than pure canola oil at both swirl numbers and all equivalence ratios. The emulsions also produced higher CO2 emissions than pure canola oil. On comparing the performance of the emulsions, it was seen that the addition of methanol to the blend had a definite positive impact on the combustion characteristics. It was observed that higher percentage of methanol in the emulsions led to lesser NOx, UHC and CO emissions. The vorticity imparted to the secondary air by the swirler also affected emission levels considerably. Increased vorticity at higher swirl angle led to better mixing of air and fuel, minimizing emission levels specifically at swirl number of 1.4. 2013 Elsevier Ltd. All rights reserved.