Performance, combustion and emission characteristics of n-butanol additive in methanol-gasoline blend fired in a naturally-aspirated spark ignition engine

The aim of the study was to compare the effects of dual alcohols (n-butanol and methanol) with single alcohol (methanol) blended in gasoline fuel (GF) against performance, combustion and emission characteristics. Problems arise in the fuel delivery system when using the highly volatile methanol-gasoline blends. This problem is reduced by adding n-butanol to methanol-gasoline blends. However, the satisfactory engine performance of the dual alcohol-gasoline blends need to be proved. The test fuels were GF, blend M53b17 (53 % methanol, 17 % n-butanol and 30% GF by volume), M20, and M70. The blend M53b17 was selected to match the vapor pressure (VP) of GF, whereas M70 to match the total alcohol content in the blend. The test fuels were a lean mixture with excess-air ratio of λ = 1.1. The experiments were conducted on a naturally-aspirated, spark ignition engine. The brake thermal efficiency (BTE) improved whereas the exhaust gas temperature (EGT) of the blends reduced, which is a benefit that reduces compression work. The regulated emissions were also reported. The blend M53b17 was recommended in preference to M70 because the former had shortened combustion duration, high-energy content and its VP was selectively matched to that of GF's.