Ethanol as a Diesel Base Fuel: Managing the Flash Point Issue - Consequences on Engine Behavior 2009-01-1807

Facing more and more stringent regulations, new solutions are developed to decrease pollutant emissions. One of them have shown promising and relevant results. It consists of the use of ethanol as a blending component for diesel fuel Nevertheless, the addition of ethanol to Diesel fuel affects some key properties such as the flash point. Consequently, Diesel blends containing ethanol become highly flammable at a temperature around ambient temperature. This study proposes to improve the formulation of ethanol based diesel fuel in order to avoid flash point drawbacks.

First, a focus on physical and chemical properties is done for ethanol based diesel fuels with and without flash point improvement.

Second, blends are tested on a passenger car diesel engine, under a wide operating range conditions from low load low speed up to maximum power. The main advantage of the ethanol based fuels generate low smoke level, that allows using higher EGR rate, thus leading to an important NOx decrease. Using the standard engine calibration, given by the engine control unit, at lower loads, the weak ignitability of the ethanol blends results in unstable and incomplete combustion, with higher fuel consumption and CO and HC emissions. This trend is extremely stressed for the improved flash point blend. That was attributed to the flash point improver lower ignitability. Consequently, the combustion settings have been optimized deeper for the flash point improved fuel. That lead to low levels of PM and NOx emissions, with a contained fuel consumption penalty and with an acceptable noise level for both fuel blends.