Effect of Carburetor Main Metering Orifice on Exhaust of the Engine Fueling Methanol and Gasoline

More and more small agricultural engines begin to use mixed fuel of gasoline and methanol. ST188 small engine test-bed is built in this paper, the effect of diameter of carburetor main metering orifice diameter on HC, CO and NOx of ST188 small engine using M10 methanol gasoline is studied by tests of changing carburetor main metering orifice, the results indicate that CO decreases 8.4％, HC decreases 1.7%, NOx increases 32％, when ST188 small engine with the bigger diameter of carburetor main metering orifice fuels M10 methanol gasoline. A measure of lessening the decrease of power performance of the carburetor engine using M10 methanol gasoline is given without increasing too more exhaust. The experiment results prove that this measure is feasible, which will accelerate the use of M10 methanol gasoline on small agricultural engines.