Experimental comparison of different diesel-biodiesel blends in a CFR engine

A wide experimental investigation was performed on a CFR engine with a view to comparing different renewable fuels in terms of Cetane Number, engine brake thermal efficiency and exhaust emissions. The CFR engine available at the Internal Combustion Engines Group of the University of Genoa was properly modified and fully instrumented in order to control operating conditions and to measure the average engine parameters and in-cylinder pressure diagrams. Aiming at the comparison of fuels obtained from various feedstock, an experimental procedure was then defined, including the standard Cetane Number evaluation and the definition of engine operating quantities in 16 different working points, considering four levels of rotational speed and load, for fixed levels of compression ratio and injection advance. Methyl-esters of rapeseed oil and of vegetable oils mix were investigated, while rapeseed, palm and coconut oil were also available. Several blends, obtained by mixing different biodiesel fractions with conventional diesel oil, assumed as reference fuel, were tested applying the defined experimental procedure. In the paper the experimental setup is firstly presented describing changes and instrumentation of CFR engine. The investigation program is then summarized in order to introduce results discussion, mainly focused on the analysis of the influence of the biodiesel content on brake thermal efficiency, NOx and soot emissions, taking into account fuel properties.