Improvement of performance and reduction of pollutant emissions of a four-stroke spark ignition engine fuelled with a mixture of hydrogen and methane as a supplementary fuel to alcohol

Abstract

Owing to the energy crisis and pollution problems of today, investigations have concentrated on decreasing fuel consumption and on lowering the concentration of toxic components in combustion products by using non-petroleum, renewable, sustainable and non-polluting fuels. While conventional energy sources such as natural gas, oil and coal are non-renewable, hydrogen and alcohol can be coupled to renewable and sustainable energy sources. The usage of a mixture of hydrogen and methane as a supplementary fuel to an alcohol-air mixture for spark ignition engines results in a considerable improvement in engine performance and in the reduction of the toxic components in exhaust gases in comparison with the conventional spark ignition gasoline engine. In tests, the gas comprising 40 per cent H₂ and 60 per cent CH₄ by volume was added to alcohol as 0, 2, 4, 6, 8, 10 and 12 per cent by mass. Operating test results for a range of compression ratio (CR) and equivalent ratio are presented. Gasoline fuel was used as a basis for comparison. The important improvement in methane addition reduced the specific fuel consumption (s.f.c.) and CO emission of alcohol engines. The performance of the engine is enhanced when relatively small amounts of hydrogen are present with methane. This improvement in performance, which is especially pronounced at operational equivalence ratios that are much leaner than the stoichiometric value, can be attributed largely to the faster and cleaner burning characteristics of hydrogen in comparison with methane or alcohol. Moreover, the addition of hydrogen decreases the s.f.c. of the engine. The possibility of an engine power quality adjustment has also been studied.