Combustion Study of a Common Rail Diesel Engine Optimized to be

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VOLUME 22, NUMBER 3

MAY/JUNE 2008

Copyright 2008 by the American Chemical Society

Special Section on Energy and EnVironment Combustion Study of a Common Rail Diesel Engine Optimized to be Fueled with Biodiesel† A. Senatore,* M. Cardone, and D. Buono Dipartimento di Ingegneria Meccanica per l’Energetica UniVersità di Napoli Federico II, Italy

V. Rocco Dipartimento di Ingegneria Meccanica, UniVersità di Roma - Tor Vergata, Italy ReceiVed August 4, 2007. ReVised Manuscript ReceiVed NoVember 24, 2007

The automobile market is, nowadays, characterized by a growing demand for cars equipped with diesel engines. This is because these offer smaller fuel consumption and better engine performance. A modern common rail turbocharged diesel engine provides performance equal to a gasoline engine, with same displacement, not turbo-charged but with a higher torque at lower engine speeds and with smaller fuel consumption. The methyl esters of vegetable oils, known as biodiesel, are receiving increasing interest because of their low environmental impact and their potential as an alternative fuel for diesel engines as they would not require any significant modification of existing engines. The modern common rail (CR) diesel engines are normally optimized for commercial diesel fuel. Consequently, the Electronic Control Unit (ECU) calibrations are defined to offer the best compromise between performance and emissions. If the engine is fuelled with an alternative fuel with different characteristics (net heating value, stoichiometric air fuel ratio (a/f), density, viscosity, etc.), it is clear that the calibration must be modified. In past experiments the authors have demonstrated that it is possible to optimize emissions and performances of a light duty CR diesel engine fueled with a vegetable derived fuel (rapeseed methyl ester) pure or blended with commercial diesel fuel, changing ECU parameters. This paper will show a detailed analysis of combustion in a modern diesel engine fueled with biodiesel and in particular some of the influences on engine parameters will be analyzed in order to demonstrate how an optimization strategy of ECU parameters could be applied to a diesel engine, when it is fueled with different fuels, with different physical/chemical characteristics.

1. Introduction Biodiesel fuel has attracted considerable attention in recent years because of both its biodegradability and nosulfur content characteristics and its low environmental impact in terms of the net global release of carbon dioxide. † Presented at the 10th International Conference on Energy and Environment. * Corresponding author.

Life cycle analysis indicates that biodiesel is highly renewable, and its use, therefore, can produce real reductions in petroleum consumption and carbon dioxide emissions. When fossil fuels are burned, in fact, 100% of the CO2 released adds to the CO2 concentration levels in the air. The fossil fuel energy required to produce biodiesel from soybean or rapeseed oil is only a fraction (about 32%) of the energy contained in 1 L of conventional fuel. Therefore, although the recycling of CO2 with biodiesel is not 100%, substituting biodiesel for petroleum diesel reduces life-cycle CO2 emissions by 78%. In addition, biodiesel can be

10.1021/ef7004749 CCC: $40.75  2008 American Chemical Society Published on Web 02/08/2008

1406 Energy & Fuels, Vol. 22, No. 3, 2008

Senatore et al.

Table 1. Diesel-Bi Characterization versus the Standards Requirements for Automotive Traction properties ester content (wt %) density (kg/m3) at 15 °C viscosity (mm2/s) at 40 °C net heating value, kJ/kg flash point (°C) sulfur content (mg/kg) carbon residue on 10% distillation residue (wt %) cetane number sulfated ash content (wt %) water content (mg/kg) total contamination (mg/kg) copper strip corrosion (3 h at 50 °C) (rating) oxidation stability at 110 °C (h) acid value (mg KOH/g) iodine value linolenic acid methyl ester (wt %) polyunsaturated (g4 double bonds) methyl esters (wt %) methanol content (wt %)

Diesel-Bi

prEN 14214:2002 standards

98.06 884.1 4.219 36000 94.0 6 0.58 118.0 7.9