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This study was aimed to characterize the effect of ethanol blends on sub-23 nm particles and on their volatile organic fraction from a turbocharged 1.8 L direct injection spark ignition engine. Tests were performed on the Worldwide Harmonized Light Vehicles Test Cycle. Engine was fueled with three different blends: 10, 25 and 85 %v/v of ethanol content, gasoline was used as reference fuel. An Engine Exhaust Particle Sizer was used to measure the particle number and size in the range 5.6 - 560 nm. Particle measure was carried out by diluting the sample gas through both a single diluter and the Dekati Engine Exhaust Diluter. The number and diameter of particles emitted from ethanol blends as well as the presence of volatiles are affected from both the specific phase of the cycle and the fuel properties. A large fraction of volatiles in the sub-23 nm range, especially in the low and extra-high phases of the test cycle, was observed whatever the fuel. Anyway, the percentage of sub-23 m particles increases as the ethanol content in the blends increases except for E85. For this blend, the greater decrease of temperature due to the stronger charge cooling effect ascribable to the larger ethanol content, deteriorates the combustion evolution contributing to the formation of large soot particles. The addition of ethanol to gasoline fuel increases the volatile organic fraction whatever the blend ratio.

The present study investigates the influence of pressure on the products of fast pyrolysis of a lignocellulosic biomass (Walnut Shells).

The experiment determined the technical and financial efficiency of five storage techniques, specifically designed for SRF poplar chips stored at the farm site in small (20 m3) piles. The treatments on test were: uncovered storage, storage under a temporary roof structure, cover under a semi-permeable fleece sheet, cover under two types of plastic sheet (i.e. white and black). Each treatment was replicated 3 times. Researchers monitored temperature and moisture content trends inside the piles, and determined dry matter losses at the end of the 170 days storage period. In general, piles under plastic cover presented opposite trends compared to all other piles. They acquired moisture rather than losing it, and showed gradual temperature trends instead of a typical peak-and-drop behaviour. Dry matter losses varied from 5.1% to 9.8%, and were highest for the uncovered treatment, and lowest for the plastic cover treatment. Under the conditions of north-western Italy, uncovered storage was a cost-effective option. Protecting the piles with some cover incurred more cost than it saved, resulting in a higher storage cost per unit energy. Although more expensive, sheltering the piles under a simple roof structure offered the benefit of a higher reduction of moisture content, which may turn the chips into a higher quality fuel. Of course, these results were closely related to the Southern European climate, and the specific year of the test. Occasional wetter years may overturn these results. © 2013 Elsevier Ltd. All rights reserved.

This paper provides a study of injection process in a research compression ignition engine fueled with Rapeseed Methyl Ester pure biodiesel and its blends by advanced optical diagnostics and 1D model. Experimental tests have been performed in an optical direct injection single-cylinder engine equipped with the Common Rail injection system of a real compression ignition engine. The injection strategies consisted of two events per cycle, the pilot and the main. The investigated conditions were representative of two engine operating points of the WLTC corresponding to two different engine speed and brake mean effective pressure values. The 2D visible imaging and the novel infrared (IR) technique have been applied to evaluate fuel spray parameters (i.e. penetration and cone angle) for liquid and vapor phases, respectively. Experimental results have been compared to data obtained with commercial diesel fuel available from previous authors' works, underlining the main differences. Furthermore, to improve biodiesel spray knowledge, 1D model for diesel jets has been suitably modified to analyze RME spray. The model has been set up via collected experimental data. Pure fuel and blends properties have been evaluated using REFPROP® software. Once the model has been validated, it has allowed to calculate the equivalence ratio along both the jet axis and radial direction, and the amount of vapor fuel over time. The modified 1D model presented in this study could be an advanced and effective instrument to study injection process in the modern engines fed with biofuel, supporting experimental activities in order to reduce time and costs.

Abstract The use of biogas in internal combustion engines presents many advantages. Nevertheless, the CO2 content in the fuel negatively affects the combustion process, reducing combustion speed and stability. The presence of hydrogen in the biogas would improve its combustion characteristics. This paper investigates the combustion of biogas in a Controlled Auto Ignition (CAI) engine by means of numerical simulations. A model of the combustion system was developed for analyzing the use of biogas in a Chemkin environment. The biogas considered in this paper naturally contains hydrogen as a result of a new anaerobic digestion process. The CAI internal combustion engine model allowed the evaluation of engine performance and emissions. Different hydrogen contents were investigated to find the optimal fuel composition for reducing nitrogen oxides emission. Exhaust Gas Recirculation (EGR) was adopted for controlling in-cylinder temperature and therefore fuel auto-ignition. In fact, the presence of very reactive chemical species in the EGR, such as nitric oxide (NO), resulted to have an important impact on the onset of combustion. The results demonstrated that biogas containing hydrogen allow a reduction of NOx emissions with respect to a conventional biogas. An optimal biogas composition was identified, allowing a 32% reduction in NOx emission compared to the conventional biogas. The reaction mechanism for NO formation did not change with biogas composition, with an important contribution coming from prompt NOx formation mechanism. The main differences were in the reaction rates, higher for the conventional biogas.

This paper investigates the changes in reactivity and physicochemical characteristics of char and tar produced from severe heat treatment in either inert or CO2-rich atmospheres of a synthetic fuel doped with Fe&Mg and K&Mg sulfates. The mineral-free model fuel was obtained by hydrothermal carbonization (HTC) of cellulose. The comparison of Py-GC/MS-GC/TCD, heated strip reactor (HSR), and drop tube reactor (DTR) results highlighted that mineral doping, heating rate, temperature, residence time and atmosphere all interacted and influenced the pyrolysis products. Fe&Mg increased the light permanent gases during flash pyrolysis. The minerals catalytically affected the decomposition of the levoglucosan fraction in the tars. In N2, the addition of K&Mg influenced the oxy-aliphatic tars, while Fe&Mg had a stronger impact on oxy-aromatic compounds. Depending on the pyrolysis temperature and residence time (and reactor type), CO2 inhibited (700 °C in the HSR) or enhanced (1027 °C in the DTR) the formation of polycyclic aromatic hydrocarbon (PAHs) in the tars. Chars doped with Fe&Mg always exhibited higher reactivity than the chars doped with K&Mg. While the presence of CO2 during pyrolysis favored the aromatization of the chars especially in combination with doped minerals, alkali mineral interaction with CO2 decisively altered char reactivity.

To promote the integration between solar-driven torrefaction, Power-to-Gas, and Chemical Looping Combustion (CLC) systems, this work numerically analyzes the performances of a novel process layout. Several agro-industrial residues were considered as fuels. CuO supported on zirconia and Ni supported on alumina were considered as oxygen carrier and methanation catalyst, respectively. Torrefied samples were purposely obtained by means of experimental runs carried out for 30 min at 300 °C in a lab-scale fixed bed reactor under a nitrogen atmosphere. Under the adopted conditions it was attained an increase in the lower heating values (LHV) of the selected feedstocks by about 14-49 %, depending on the different composition and reactivity of the parent biomass. Based on these data, it was estimated that, with respect to 10 kg h-1 torrefied biomass fed to the CLC system, a total thermal power production in the range of 28-58 kW can be achieved. CO2 conversion degrees of above 98 % were evaluated for the methanation unit in all considered scenarios. Considering different locations in Italy, PV field sizes ranging from 45 m2 up to 1392 m2 were evaluated for the solar-driven torrefaction unit. Wider sizes were calculated for the hydrogen production one, ranging from 3366 m2 up to 5598 m2. Eventually, an electric energy storage efficiency of around 16 % was assessed for the proposed layout. Finally, it was found that moving from the adopted torrefied feedstocks to the produced gaseous fuel, an increase in the LHV by about 44-55 % can be attained, while concurrently, CO2 emissions are favorably decreased by 98 %.