Effect of Fuel Composition on NOx Formation in Lean Premixed Prevaporized Combustion

Abstract

The effect of fuel composition on NOx formation in lean premixed prevaporized (LPP) combustion is examined using an atmospheric pressure jet-stirred reactor fitted with a prevaporizing-premixing chamber and liquid fuel atomizing nozzle. Four liquid fuels are studied, including the pure hydrocarbons n-heptane (C7H16) and n-dodecane (C12H26), No. 2 low sulfur diesel fuel oil (LSDFO#2) with 0.0195% sulfur and 0.0124% nitrogen by weight, and n-dodecane doped with n-ethylethylenediamine (C2H5NHCH2CH2NH2 or C4H12N2) to give 0.0096% nitrogen by weight in the doped fuel. For comparison, propane (C3H6) is burned. The combustion temperature range of the experiments is 1625 to 1925K, and the nominal residence time of the reactor is 3.5ms. The first objective of the work is to determine the effect which increasing fuel carbon number has on the NOx yield of high-intensity LPP combustion. For combustion at 1800K, an increase of 15 to 20% is measured in the NOx yield when the fuel is changed from C3H6 to C12H26. Comparison to earlier work on CH4 and C3H6 combustion in the jet-stirred reactor operating at 1800K shows essentially an identical increase in NOx yield between CH4 and C3H6 as between C3H6 and C12H26. The second objective of the work is to determine the conversion of fuel-nitrogen to NOx for the combustion of low nitrogen content fuels in high-intensity LPP combustion. The measurements indicate a fuel-nitrogen to NOx conversion of 70 to 100%. These conversion values should be regarded as preliminary since only two nitrogen-containing fuels have been examined and only one prevaporizer-premixer system has been used.