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The pressure losses across the different parts of a regenerative Diesel Particulate Filter (DPF) have been modeled and compared with the measured pressure loss and with the measured changes in the instantaneous weight of the DPF of a commercial automotive diesel engine. The comparisons were made in three operating conditions selected among those included in the transient cycle established in the European Emission Directive. The first one is a low-load mode, with high soot emissions and therefore with high contribution to the DPF charge. The second one is a medium-load mode, in which the balance of soot charge versus spontaneous soot regeneration leads to a slow DPF charging, the temperature at the exhaust manifold being high enough to permit active regeneration. The third one is a high-load mode, in which the spontaneous regeneration leads to a net DPF discharge, the active regeneration becoming useless.

The effect of the biodiesel feedstock on the engine performance and emissions is expected to become increasingly important as the emissions regulations become more stringent (Euro 5). This work aims to study the effect of the degree of unsaturation of a biodiesel fuel (which is a characteristic of the original oil), this being quantified by the iodine number, on the pollutant emissions and combustion timing. Four biodiesel fuels with iodine numbers ranging from 90 to 125 were tested pure and blended (30% and 70% biodiesel content, volume basis) with a diesel reference fuel, which was tested too, in a four-cylinder, 2.2 litre, turbocharged, direct injection diesel engine. The operation modes were selected to be representative of the New European Driving Cycle. In general, pure biodiesel fuels, compared to the reference fuel, resulted in sharp reductions in particle mass and opacity (60-70%) and in a slight increase in both fuel consumption (around 15% in mass) and NOx emissions (9%).

Methyl esters obtained from the most interesting Spanish oleaginous crops for energy use -sunflower and cynara cardunculus- were both used as diesel fuels in this work, pure and in 25% blends with a reference commercial fuel which was also used pure. A stationary engine test bed, together with the appropriate instrumentation for chemical and morphological analysis, allowed to evaluate the effect of these fuels on the engine emissions, particularly in the main particulate matter characteristics, such as soluble organic fraction, origin of adsorbed hydrocarbons, sulphate content, particle number per unit filter surface, and mean particle diameter. Both the consideration of the main thermochemical properties of the tested fuels and the computations of a chemical equilibrium model were helpful for the analysis of the experimental results.

A study about the utilisation of producer gas from gasifiers for obtaining mechanical energy in a SI engine is presented in this work. Therefore, the influence of the gas composition and its thermodynamic properties on the combustion characteristics and on the engine performance are analysed. A home-made chemical equilibrium model which considers 28 chemical species was used to calculate the gas composition as a function of the gasification conditions, and to study the influence of the gas composition on some thermochemical parameters such as adiabatic flame temperature and heat release. The chemical kinetic package CHEMKIN III was also used to study its autoignition behaviour. Finally, a quasi-dimensional two-zone model for SI engines was used to calculate the knock tendency and to analyse the effect of fuel composition on some combustion parameters related to engine performance (IMEP, cylinder pressure, etc.).

A nonequilibrium approach for the instantaneous calculation of the composition of 29 chemical species is used in this work to simulate the evolution of the gas composition in a Diesel engine cylinder from the start of combustion to the exhaust opening. A discretization of the heat release law is used as a sequential source of combustion products, which are then subjected the evolution of pressure directly measured from the cylinder engine, and to the evolution of a burnt-zone temperature obtained from the same pressure signal through a diagnosis thermodynamic model. For each burning fuel package, the equilibrium composition and the corresponding adiabatic flame temperature are considered as initial conditions for the kinetic calculation of the gas composition evolution.

The particulate reduction targets imposed by regulations require wide knowledge about the effect of fuel formulation on both particulate emissions and composition. The results of a set of engine steady test-bed experiments, extraction procedures and chemical analysis are presented in this paper, aiming to study the effect of some of the main fuel properties on the particulate emissions and composition of a typical European passenger car Diesel engine. The tested fuels had different properties (density, volatility, cetane number, aromatic content, sulphur content, etc.), and also different engine operating conditions such as torque and engine speed, were tested.