Clean combustion enabling with ethanol on a dual-fuel compression ignition engine

Abstract

In this work, ethanol is applied as the main energy source (up to 95%) on a high compression ratio (18.2:1) diesel engine for improvements in engine efficiency and exhaust emissions, especially at high engine loads. The intake port injection is applied for ethanol fuel delivery along with directly injected diesel pilots as the ignition source. In order to investigate the impact of ethanol on diesel engines operating in the dual-fuel mode, systematic engine experiments are carried out to study the combustion process, engine emissions, and fuel efficiency. The test results indicate that at medium engine loads (8–10 bar indicated mean effective pressure), the increasing use of ethanol offers substantially enhanced homogeneity of the cylinder charge and leads to a greater extent of premixed burning; as a result, the smoke emissions reduce drastically compared to those of the diesel baseline tests. However, the increasing use of ethanol generally results in higher incomplete combustion products. The near-top dead center injected diesel pilots are effective to control the ignition timing and combustion phasing, which provides desirable combustion controllability. At high engine loads, the clean combustion is enabled through the optimization of the engine intake pressure, exhaust gas recirculation, and the fuel ratio to achieve NOx emissions < 0.2 g/kW h and smoke emissions < 0.01 g/kW h. The load capability of the engine operating on ethanol as the primary energy source is demonstrated up to the engine full load (19.5 bar indicated mean effective pressure) with low NOx (0.2–0.7 g/kW h) and smoke ( <1 FSN) emissions.