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The present paper is focused on the application of the Low Temperature Combustion (LTC) systems to modern diesel engines. Aim of the work was to assess the possibility to optimize LTC systems performances in terms of both engine efficiency and pollutant emissions. In particular, the results of a study of the effects of highly cooled Exhaust Gas Recirculation (EGR) on a diesel engine running at LTC condition, will be presented and discussed. The engine employed for the experimental activity was a FIAT JTD 4 cylinder CR diesel engine, EURO 4 version. The EGR layout was modified with respect to the production one, in order to obtain lower temperatures of the recirculated exhaust gases. The performed tests evidence the advantages offered by the strong EGR cooling (and so the lower intake air temperature) in reducing NOx emissions, leaving very low Soot emissions, typical of premixed low temperature combustion.

In this paper some preliminary results on the emission performance of a modern CR DI diesel engine running on reformulated diesel fuels are discussed. The engine employed in the tests was a Fiat M724 1910cc, installed on Alfa Romeo 156 1.9 JTD. Modern injection systems can modify the spray structure with respect to a spray of a classical rotary injection pump so the well-consolidated knowledge on the correlation between fuel parameters and pollutant emissions may not be valid for the new generation of DI diesel engines. Two high quality fossil fuels and a synthetic fuel were selected for the tests. Tests were directed to analyze the relative influence on exhaust emissions between injection parameters and fuel quality. One engine test point (2000 rpm × 2 bar of b.m.e.p.) was chosen, with different setting of injection pressure, EGR ratio and pilot injection activation.

This paper presents the performances of a modern DI diesel engine, equipped with a Common Rail injection system, fed on blends of an advanced diesel fuel (base fuel) and Diethylene-Glycol-Dimethyl-Ether (Diglyme - C6H14O3). The base fuel was a reformulated diesel fuel with low aromatic and sulfur content. Three blends with different volumetric percentage of Diglyme (10, 20 and 30%) in the base fuel were prepared and tested. The engine was a FIAT M724, installed in a Alfa Romeo 156 1.9 JTD, with a Bosch Common Rail injection system (EDC-15C). At the exhaust of the engine, soot, NOx, HC, CO, and CO2 were measured. The experiments represent the potential of diesel reformulation technology with synthetic fuels coupled with the new diesel technology generation.

In this paper results on in-cylinder pollutant concentration evolution during combustion of six different oxygenated fuels, in comparison with tetradecane and n-octane combustion, are presented. These four fuels are: Ethylene-Glygol-Dimethylether (monoglyme-C4H10O2), Diethylene-Glygol-Dimethylether (diglyme-C6H14O2), Diethylene-Glycol-Diethylether (diethyldiglycol-C8H18O3), butylether (C8H18O). Two techniques were adopted on a single cylinder direct injection diesel engine: two-color pyrometry for the measurement of in-cylinder soot loading and a fast sampling valve for the measurements of in-cylinder combustion products. In addition, the sampling line downstream of the fast sampling valve was adapted for the in-cylinder aldehyde measurements. The main results obtained provide information about the mechanisms that control soot evolution during diesel combustion.

Selected measurements of the in-cylinder soot loading and the gaseous combustion products for ten different innovative fuels, burned in a D.I. diesel engine are presented and discussed. All the fuels which were tested have a very low sulfur content, so the insoluble fraction of the particulate is mainly composed of soot. Two different measure techniques are applied: the two-color pyrometry optical method and the fast sampling of gaseous products in the combustion chamber. A priori and experimental uncertainties relative to the reduction of the data obtained with the two-color measurements are preliminarily investigated.

A methodological analysis of combustion parameters and pollutant emissions measuring procedures during transient operation of a D.I. T.C. light duty diesel engine was performed. Combustion process was characterized by ignition delay time, combustion pressure peak value and heat release law measurements during the transient ECE 15 schedule on a dynamic test bed with electronic simulation of inertia. The particulate emission was measured every 0.05 s by an I.R. optical method. In addition some correlations, based on pressure cycle and injection law evolution, were implemented in order to calculate instantaneous fuel delivery and transient NOx emission. Some activities were carried out in order to asses the limits of engine configurations ranking performed with steady state measurements of performances and emissions. Strong differences were detected between carbon emission during transient operations and the value obtained by interpolation from a steady state map.