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.

Exploring the mid-load potential of ethanol-diesel dual-fuel combustion with and without EGR

“…CO emissions decreased as the ethanol fraction was increased from 40% towards 80%, which is likely linked to the reduction in partial oxidation of the premixed fuel. Relatively lower levels of ISCO at high ethanol percentages was also reported by Han et al [10] over a sweep of intake oxygen concentration at 1.0 MPa IMEP. Higher engine loads and the use of EGR were effective in reducing CO emissions, mainly due to increased global fuel/air equivalence ratio.…”

“…One effective approach is the dual-fuel combustion mode, which allows for the use of alternative low carbon fuels in diesel engines while improving efficiency and reducing NOx emissions [8,9]. The dual-fuel combustion also introduces significant soot reduction compared with conventional diesel combustion, particularly at elevated EGR rates [10,11]. As a result, fuel energy supply is diversified, production and running costs can be reduced, and air quality and subsequent effects to human health are improved.…”

Isolating the effects of reactivity stratification in reactivity-controlled compression ignition with iso-octane and n-heptane on a light-duty multi-cylinder engine

“…For example, several studies have looked at ethanol’s high antiknock properties. 5,6 Curran et al 7 explored the role of an 85% ethanol–gasoline blend (E85) for the premixed fuel on extending the load range for RCCI in a multi-cylinder light-duty engine and found significant load increase compared to ethanol-free gasoline (E0). In a subsequent study, the role of high octane ethanol–gasoline blends in extending stable combustion over more of the light-duty drive cycle load range was also explored.…”

Diesel-Minimal Combustion Control of a Natural Gas-Diesel Engine

“…It can be explained by the strong dilution of the diesel if it is injected very early, which leads to a low local equivalence ratio towards the end of the compression phase and therefore to a longer ignition delay of the diesel [15]. The sign change can also be observed in other dual-fuel engines that use diesel to ignite the mixture, for example, if gasoline or ethanol is used as the primary fuel, see [15] or [16], respectively. The method proposed in this paper can be applied to all engines that feature this sign change.…”