Investigation on idle performance of a spark-ignited ethanol engine with dimethyl ether addition

Dimethyl ether (DME) and ethanol are thought to be alternative fuels for future internal combustion (IC) engines. The experiments in this paper were carried out at idle and stoichiometric conditions to investigate the effect of DME addition on the idle performance of a spark-ignited (SI) ethanol engine. The engine was modified to be fueled with the mixture of DME and ethanol which were injected into the engine intake ports simultaneously. A hybrid electronic control unit (HECU) was specially developed to control the injection timings and durations of ethanol and DME, accomplishing specified excess air ratios and DME addition fractions in the total ethanol-DME fuel mixture. The experimental results demonstrated that, the indicated thermal efficiency was increased by over 20% after DME blending and the flame development and propagation durations were shortened with the increase of DME addition fraction. Meanwhile, HC emissions were obviously decreased with the increasing fraction of DME addition, while NOx emissions were slightly increased. Therefore, DME addition is a potentially applicable method to improve the idle performance of SI ethanol engines. (C) 2011 Elsevier B.V. All rights reserved.