THE EFFECT OF GASOLINE FUEL TYPE ON SI ENGINE NITROGEN-OXIDES AND CARBON-MONOXIDE EMISSIONS UNDER PART-LOAD OPERATING-CONDITIONS

Six different gasoline blends with different antiknock agents and arom atics content were investigated for its influence on SI engine nitroge n-oxides and carbon monoxide emissions at part- load operating conditi ons. The six fuel types used were leaded gasoline with 0.5 g Pb/l, com mercial unleaded gasoline, unleaded synthetic gasoline and its blends with different proportions of methyl tertiary butyl ether MTBE (10, 15 and 20 vol%). A four- stroke, four- cylinder, spark- ignition Regata engine (type 138 B 3,000) was used for conducting this study. The exha ust gases were analyzed for nitrogen-oxides and carbon monoxide emitte d at part-load operating conditions for the speed range of 1000 to 300 0 rpm. The results of this investigation have shown that blending unle aded synthetic gasoline with ethers such as MTBE reduces the aromatic content of the fuel. The 20 vol% MTBE-fuel blend gave the lowest carbo n monoxide emissions of all blends used at part load condition. On the other hand, the 10 vol% MTBE-fuel blend gave the lowest nitrogen-oxid es emission of all blends at part-load condition. The carbon monoxide concentration in engine exhaust differs between increase and decrease at part-load condition when fuel aromatics content increases. It was a lso found that as the gasoline aromatics content increases in the blen d, the nitrogen-oxides concentration in engine exhaust increases. So, substitution of MTBE for the higher aromatics gasoline blends may help improving state environment and air quality.