Experimental Investigation of Hydrous Ethanol Gasoline on Engine Noise, Cyclic Variations and Combustion Characteristics

Nowadays, the noise pollution of internal combustion engines is a very important factor influencing human health and is the main noise source of urban environmental noise. Additionally, the main source of gasoline engine noise consists of combustion noise in the cylinder, where the combustion noise is influenced by the combustion processes within the combustion chamber, especially the cyclic variation in the engine combustion. Thus, the inter-relationship between engine noise, cyclic variation and combustion is of great interest to be explored. Moreover, despite the environmental advantages of clean energy, the impact of different fuels on the internal combustion engine’s noise emissions cannot be ignored. As a result, in this work, three blends were prepared and used as test fuels, namely pure gasoline (E0), 10% hydrous ethanol (E10W) and 20% hydrous ethanol (E20W) by volume, accompanied by engine operating at a steady speed of 2000 r/min under various loads. The experimental results show that lower engine noise was observed for both E10W and E20W compared to E0. Upon the addition of hydrous ethanol, the peak in-cylinder pressure increased while the maximum pressure rise rate (( dp/dφ ) max ) decreased at the low and medium loads. Furthermore, the coefficients of variation in indicated mean effective pressure ( COV imep ) and COV ( dp/dφ ) max for the two blended fuels were higher than those for pure gasoline. Compared with those of E20W, E10W has lower COV imep and COV ( dp/dφ ) max at low and medium loads. The ( dp/dφ ) max and noise emission have a positive relation when the engine is fueled with the hydrous ethanol–gasoline blends, whereas the cyclic variation parameters vary in the opposite direction of the noise emission level for all the blend mixtures. Moreover, ( dp/dφ ) max has an essential effect on the combustion noise from a gasoline engine.