Experimental study on sparking ignition engine performance for optimal mixing ratio of ethanol-gasoline blended fuels

purpose of this study is to experimentally determine the optimal blend rate of ethanol-gasoline fuels in order to maximize the brake thermal efficiency of a commercial SI engine. In this study, the engine performance, in terms of brake torque and brake specific fuel consumption, has been investigated with variation of volumetric mixing ratio between 87.5-octane gasoline and 99.5%-purity ethanol (E10, E20, E30, E40, E50, E60, E70, E85, and E100). The experiment has been conducted at different engine speeds and percentages of intake-throttle opening. The tests were performed at a constant compression ratio. The relative air-fuel ratio was tuned to unity and the ignition timing was tuned for maximum engine torque. The experimental results indicated that the appropriate ethanol-gasoline mixing ratio can enhance engine torque output, especially at low engine speed. The brake thermal efficiency is maximum when the engine operates at 58-73% of WOT with an engine speed of 2000-2500 rpm, using E40 and E50 fuels. This paper also provides a guideline for a suitable ethanol-gasoline blend rate at a certain engine load and speed. (C) 2016 Elsevier Ltd. All rights reserved.