An Experimental Investigation of Directly Injected E85 Fuel in a Heavy-Duty Compression Ignition Engine

A commercially available fuel, E85, a blend of ~85% ethanol and ~15% gasoline, can be a viable substitute for fossil fuels in internal combustion engines in order to achieve a reduction of the greenhouse gas (GHG) emissions. Ethanol is traditionally made of biomass, which makes it a part of the food-feed-fuel competition. New processes that reuse waste products from other industries have recently been developed, making ethanol a renewable and sustainable second-generation fuel. So far, work on E85 has focused on spark ignition (SI) concepts due to high octane rating of this fuel. There is very little research on its application in CI engines. Alcohols are known for low soot particle emissions, which gives them an advantage in the NOx–soot trade-off of the compression ignition (CI) concept. Therefore, the main objective of this research is to experimentally characterise the impact of E85 on performance and emissions of a heavy-duty (HD) direct ignition compression ignition (DICI) engine at mid-to-low load, and to identify possible challenges. To do so, a surface response method of the Box-Behnken type is implemented on a measurement campaign on a HD single cylinder CI engine. The effects of common rail pressure (Prail), λ and combustion timing (CA50) as control parameters on experimentally measured values of soot, regulated gaseous emissions (NOx, CO and THC) and gross indicated efficiency (GIE) of the engine are studied. Linear regression (LR) analysis indicates that the outputs of the NOx and soot models are affected by all three control parameters, whereas GIE, THC and CO models in this case exclude λ effects. E85 fuel shows potential to be a good candidate for highly efficient low temperature combustion (LTC) in DICI engines, with reduced NOx and soot levels compared to fossil diesel combustion.