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In this work, a promising technique, consisting of a liquid Water Injection (WI) at the intake ports, is investigated to overcome over-fueling and delayed combustions typical of downsized boosted engines, operating at high loads. In a first stage, experimental tests are carried out in a spark-ignition twin-cylinder turbocharged engine at a fixed rotational speed and medium-high loads. In particular, a spark timing and a water-to-fuel ratio sweep are both specified, to analyze the WI capability in increasing the knock-limited spark advance. In a second stage, the considered engine is schematized in a 1D framework. The model, developed in the GT-Power(TM) environment, includes user defined procedures for the description of combustion and knock phenomena. Computed results are compared with collected data for all the considered operating conditions, in terms of average performance parameters, in-cylinder pressure cycles, burn rate profiles, and knock propensity, as well. Finally, the validated model is applied to investigate the full potential of water injection in reducing the knock tendency and improving the fuel economy in a wide load range. The numerical results highlight that WI technique involves significant Brake Specific Fuel Consumption (BSFC) advantages, especially at the medium-high loads. These benefits are limited by the maximum allowable levels for the in-cylinder pressure, while additional advantages are obtained in terms of reduced turbine inlet temperature, turbocharger speed, and boost pressure. The developed numerical procedure, based on validated combustion and knock sub-models, is able to take into account the complex interactions among different parameters, which affect the engine behavior. It is hence believed to realistically forecast the WI-related BSFC advantages and constraints, induced by thermo-mechanical stresses. Simultaneously, it underlines the need of a partial engine redesign to fully exploit WI potential.

The convective drying of pine wood cylinders (40 mm diameter) in hot air has been investigated experimentally for conditions reproducing those encountered in the drying section of xed-bed updraft gasiers (nominal velocities of 0.4- 1:2 m=s and maximum air temperatures of 435-600 K). Temperature proles show a drying zone slowly propagating from the heat exposed surfaces towards the inside, whereas the global drying rate presents two maxima, corresponding to moisture evaporation along a thin supercial layer and sample heat-up, respectively. The drying times reproduce trends already known on dependence of the external heating conditions and the initial moisture content. From the quantitative point of view, a moisture content of 50% is observed to delay the particle heating times up to factors of 3-5. Acceptable quantitative agreement is obtained between these measurements and the predictions of a simplied model of moisture evaporation in wood, which can be used to treat single particle e7ects in the more complicated mathematical descriptions of gasier behavior.

The gaseous and liquid products of the fixed-bed pyrolysis of agricultural residues (hazelnut shells, olive pomace, straw pellets) and wood (beech wood and softwood pellets) are chemically characterized and compared. The heating temperature is varied in the range 473-800 K but the process occurs in the presence of large thermal overshoots. These reach their maxima for heating temperatures below (residues, overshoots up to about 225 K) or above (wood, overshoots up to about 85 K) approximately 650 K. Though mainly originated from secondary decomposition, overheating also highly enhances the primary decomposition rates, globally leading to short volatile residence times. As a consequence, the product distribution is modified. In particular, at low heating temperatures, also following pyrolytic runaway, the residues produce the largest amounts of volatiles and the yields of several condensable organic compounds (acetic acid, propionic acid, formic acid, hydroxypropanone, levoglucosan, guiacols and syringols) reach their maxima, with even qualitative deviations from the usual trends observed in pyrolysis.

Among all the CCS strategies, post-combustion capture provides a near-term solution for stationary fossil fuel-fired power plants, eliminating the need for substantial modifications to existing combustion processes and facilities. In this respect, adsorption using solid sorbents has the potential, in terms of energy saving, to complement or replace the current absorption technology. Therefore, the design of highly specific CO2 adsorbents materials is requested. In this framework, great interest is focused on nanomaterials, whose chemico-physical properties can be tuned at the molecular level. As regards the handling of such materials, sound-assisted fluidization is one of the best technological options to improve the gas-solid contact by promoting a smooth fluidization regime. The presentwork is focused on the CO2 capture by sound-assisted fluidized bed of fine activated carbon. Tests have been performed in a laboratory scale experimental set-up at ambient temperature and pressure, pointing out the effect of CO2 partial pressure, superficial gas velocity, sound intensity and frequency. Effectiveness of CO2 adsorption has been assessed in terms of the moles of CO2 adsorbed per unit mass of adsorbent, the breakthrough time and the fraction of bed utilized at breakpoint. The results show, on one hand, the capability of the sound in enhancing the adsorption process and, on the other hand, confirm that sound assisted fluidization of fine solid sorbents is a valid alternative to the fixed bed technology, which require also an additional previous step of pelletization.

In the present study a laminar premixed ethylene flame was doped with different amounts of ethanol in order to understand the influence on biofuels in the total amount of particulate matter and the size distribution functions of the formed carbonaceous particles. Four different flames were investigated: one of pure ethylene as reference and three with an increased amount of ethanol, i.e. 10%, 20% and 30%. The equivalence ratio of the four flames was kept constant at 2.01. The particle size distribution functions were obtained using a nano-Differential Mobility Analyzer (nano-DMA). The results showed a general reduction of the total volume fraction of particulate when ethanol was added. The reduction of the formed particles increased as a function of the amount of ethanol added. The particle size distribution for pure ethylene flame and ethanol doped flames at different heights with the same amount of particles are quite similar. This indicates that in premixed flames, ethanol mostly affects gas phase chemistry and consequently the formation of incipient particles.

One of the main drawbacks of using biomass as pyrolysis feedstock consists of the huge variability of the different biomass resources which undermines the viability of downstream processes. Inherent inorganic elements greatly contribute to enhance the compositional variability issues due to their catalytic effect (especially alkali and alkaline earth metals (AAEMs)) and the technical problems arising due to their presence. Due to the different pretreatments adopted in the experimental investigations as well as the different reactor configurations and experimental conditions, some mechanisms involving interactions between these elements and the biomass organic fraction during pyrolysis are still debated. This is the reason why predicting the results of these interactions by adapting the existing kinetic models of pyrolysis is still challenging. In this work, the most prominent experimental works of the last 10 years dealing with the catalytic effects of biomass inherent metals on the pyrolysis process are reviewed. Reaction pathways, products distributions and characteristics, and impacts on the products utilization are discussed with a focus on AAEMs and on potential toxic metallic elements in hyperaccumulator plants. The literature findings are discussed in relation to the applied laboratory procedures controlling the concentration of inherent inorganic elements, their capability of preserving the chemical integrity of the main organic components, and the ability of resembling the inherent inorganic elements in the raw biomass. The goal is to reveal possible experimental inconsistencies and to provide a clear scheme of the reaction pathways altered by the presence of inherent inorganics. This analysis paves the way for the examination of the proposed modifications of the existing models aiming at capturing the effect of inorganics on pyrolysis kinetics. Finally, the most relevant shortcomings and bottlenecks in existing experimental and modeling approaches are analyzed and directions for further studies are suggested.

The paper reports an experimental study carried out with a 110-mm ID fluidized bed combustor focused on the characterization of particulates formation/emission during combustion of coal and non-fos...

The influence of two strains of Trichoderma (T. harzianum strain T22 and T. atroviride strain P1) on the growth of lettuce plants (Lactuca sativa L.) irrigated with As-contaminated water, and their effect on the uptake and accumulation of the contaminant in the plant roots and leaves, were studied. Accumulation of this non-essential element occurred mainly into the root system and reduced both biomass development and net photosynthesis rate (while altering the plant P status). Plant growth-promoting fungi (PGPF) of both Trichoderma species alleviated, at least in part, the phytotoxicity of As, essentially by decreasing its accumulation in the tissues and enhancing plant growth, P status and net photosynthesis rate. Our results indicate that inoculation of lettuce with selected Trichoderma strains may be helpful, beside the classical biocontrol application, in alleviating abiotic stresses such as that caused by irrigation with As-contaminated water, and in reducing the concentration of this metalloid in the edible part of the plant.