INVESTIGATION OF LAMINAR FLAME SPEED OF ALTERNATIVE LIQUID FUEL BLENDS

Abstract

The rapid fluctuation in oil prices and increased demand of clean fuels to reduce emissions has forced the researchers to find alternative fuels that can give the same or better overall fuel characteristics. This thesis aims at looking into the prospects of Gas to Liquid (GTL) fuel as an alternative fuel for Internal Combustion Engines (ICEs), by investigating the flame speed of GTL fuel and its 50/50 (by volume) blend with conventional diesel. The tests were conducted in a newly designed state of the art cylindrical bomb test rig capable of measuring laminar flame speed at different initial temperatures and equivalence ratios, employing pressure signal for measuring flame speeds. The bomb measurements for conventional diesel were found in an excellent agreement (error of 1.5%) when compared with the literature. The GTL and its 50/50 blend were investigated for their laminar flame speeds, along with the effect of changing the equivalence ratio and initial temperature on the flame speed. It was found that the pure GTL has highest flame speed (SN=88.3 cm/s) as compared to conventional diesel, near and at stoichiometric mixtures (Φ=1.1), which was 5 cm/s more than conventional diesel. At lean and rich mixtures, the flame speed of GTL get slightly lower than conventional diesel. The 50/50 blend gave a lower flame speed at lean and rich mixture conditions as compared to the rest of the fuels. The flame speed of 50/50 blend was almost the same as that of pure conventional diesel at stoichiometric conditions. The flame speed of all three tested fuels was increasing with the increase of initial temperature of the mixture, which also confirms with the literature. It was concluded that the GTL fuel is good if the application requires higher flame speed near the stoichiometric conditions. If the application requires conserving conventional diesel and using alternative fuel, 50/50 blend of conventional diesel and GTL shall give the exact flame speeds.