Impact of the laminar flame speed correlation on the results of a quasi-dimensional combustion model for Spark-Ignition engine

Abstract In the present study, the impact of the laminar flame speed correlation on the prediction of the combustion process and performance of a gasoline engine is investigated using a 1D numerical approach. The model predictions are compared with experimental data available for full- and part-load operations of a small-size naturally aspirated Spark-Ignition (SI) engine, equipped with an external EGR circuit. A 1D model of the whole engine is developed in the GT-Power™ environment and is integrated with refined sub-models of the in-cylinder processes. In particular, the combustion is modelled using the fractal approach, where the burning rate is directly related to the laminar flame speed. In this work, three laminar flame speed correlations are assessed, including both experimentally- and numerically-derived formulations, the latter resulting from the fitting of laminar flame speeds computed by a chemical kinetic solver. Each correlation is implemented within the combustion sub-model, which is properly tuned to reproduce the experimental performance of the engine at full load. Then, the reliability of the considered flame speed formulations is proved at part-loads, even under external EGR operations

Immagine e immaginazione

Che cos’è un’immagine? E che rapporto ha con l’immaginazione? A queste domande rispondono i saggi raccolti nel volume, articolati secondo tre fondamentali linee interpretative: un approccio storico, che dà rilievo al rapporto tra immagine e immaginazione nella storia del pensiero; uno sguardo etico-politico, che mette al centro della riflessione il ruolo del binomio immagine-immaginazione nella scelta individuale o collettiva; e infine il punto di vista estetologico, che mostra la specificità della dimensione artistica, sia essa visuale o letteraria

Experimental prototype development and performance analysis of a small-scale combined cycle for energy generation from biomass

Abstract This paper presents a research activity aimed at exploiting combined cycles (gas turbine plants coupled with steam cycles) for small-scale energy generation from carbon-neutral biomass. Such a goal has never been achieved before, since combined cycles are generally suited only for large-scale applications and for clean fuels. In order to adapt combined cycles to small-scale energy generation using dirty fuels, the implementation of cost-effective and commercially available components is studied, such as the use of a turbocharger and a power turbine taken from the automotive industry. The ongoing realization of the first prototype of small-scale combined cycle is presented in this paper, providing a detailed description of both the plant architecture and the main components chosen. In addition, a commercially available tool (Cycle Tempo) is used to demonstrate the high feasibility and potential of the plant in terms of efficiency. To that end, different plant configurations are studied and the effects of losses on the plant performance are investigated in detail

design of a novel open space test rig for small scale wind turbine

Abstract In the present paper, an innovative and cost-effective open test rig for small and medium wind turbines is proposed. The main aim is to develop a valid alternative to wind tunnels, which present unresolved problems such as the unmatched Reynolds numbers for downscaled wind turbine tests. The proposed test bench concept is an open field, subsonic facility for horizontal and vertical axis wind turbines. The core of the test bench is a cluster of axial fans, positioned at a given height from the ground, which generate an air flow suitable for testing a wind turbine placed in front of the fans. The present work aims at investigating the feasibility of this novel concept of test rig for small wind turbines having a rotor diameter smaller than 5 m. A thorough CFD analysis is performed in this paper in order to assess the characteristics of the wind generated by the fans in terms of uniformity and intensity, even in case of atmospheric disturbances. The developed CFD modelling is also instrumental in both determining the maximum rotor diameter that can be tested and selecting the correct position for a wind turbine in the proposed open test rig

Acoustic cavitation by means ultrasounds in the extra virgin olive oil extraction process

Abstract The virgin olive oil extraction process has changed very little over the past 20 years when the mechanical crushers, malaxers, horizontal and vertical centrifuges, took place in the olive mills. However, malaxation process remains the main critical step due to the discontinuity of this process. In previous activities, the same authors demonstrated how application of new emerging technologies could offer an interesting number of advantages to remove this bottleneck and, among the others, the ultrasound (US) technology is the most promising one, due to its mechanical and thermal effects due to the acoustic cavitation phenomenon. Acoustic cavitation, provided by means of low frequency high power ultrasounds, increases the quality, the work capacity and efficiency of the extraction plant, guaranteeing the sustainability. The paper shows how the authors have designed, realized and tested the first in the world continuous ultrasonic full-scale device for the extra virgin olive oil industry, with the aim to obtain the best product quality at the highest efficiency. Considering the heterogeneity of the olive paste, which is composed of different tissues, and considering the large number of parameters able to influence the process, a 3D multiphase CFD analysis was used as auxiliary tool in the design a so-called Sono-Heat-Exchanger (SHE). This innovative device, to be placed between the crusher and the decanter, is a combination of a heat-exchanger with plate-shape ultrasonic transducers. Finally, experimental results about yields and phenols contents demonstrated the relevance of this innovation

Selective Aerobic Oxidation of 5-Hydroxymethylfurfural to 2,5-Diformylfuran or 2-Formyl-5-furancarboxylic Acid in Water by using MgO⋅CeO2 Mixed Oxides as Catalysts

Mixed oxides based on MgO⋅CeO2 were used as efficient catalysts in the aerobic oxidation of 5-hydroxymethylfurfural (5-HMF) to afford, with very high selectivity, either 2,5-diformylfuran (DFF, 99 %) or 2-formyl-5-furancarboxylic acid (FFCA, 90 %), depending on the reaction conditions. 5-Hydroxymethyl-2-furancarboxylic acid (HMFCA, 57–90 %) was formed only at low concentration of 5-HMF (<0.03 m) or in presence of external bases. The conversion of 5-HMF ranged from a few percent to 99 %, according to the reaction conditions. The oxidation was performed in water, with O2 as oxidant, without any additives. The surface characterization of the catalysts gave important information about their acid–base properties, which drive the selectivity of the reaction towards DFF. FFCA was formed from DFF at longer reaction times. Catalysts were studied by XPS and XRD before and after catalytic runs to identify the reason why they undergo reversible deactivation. XRD showed that MgO is hydrated to Mg(OH)2, which, even if not leached out, changes the basic properties of the catalyst that becomes less active after some time. Calcination of the recovered catalyst allows recovery of its initial activity. The catalyst is thus recoverable (>99 %) and reusable. The use of mixed oxides allows tuning of the basicity of the catalysts, avoiding the need for external bases for efficient and selective conversion of 5-HMF and waste formation, resulting in an environmentally friendly, sustainable process

Fluid dynamic-based Engineering design of a Full-Scale Device for the improvement of Extra Virgin Olive Oil Yield and Quality by means of Combined Acoustic Cavitation and Thermal Conditioning

After some hesitations, the scientific community is jointly converging on the benefits due to the ultrasound treatment by means of mechanical effects generated by acoustic cavitation phenomena occurring into the olive oil paste proposed initially by Amirante and Clodoveo. In recent works, many authors have now confirmed that this promising emerging technology produces relevant beneficial effects if applied to the extraction process under well-controlled conditions. In the last years, the industrial applications of ultrasound (US) in the Extra-Virgin Olive Oil (EVOO) extraction process are changing the paradigm of the knowledge in this field of interest due to a great effort of the research activity. In the present work, the design of the device by means a Three-Dimensional (3D) Multiphase Computational Fluid Dynamic (CFD) analysis was performed, which describes the ultrasound effects in the olive paste, necessary to control the US waves propagation. Thus, fluid dynamic analysis allowed to predict the flow path in the ultrasound devices, to evaluate the flow parameters of the olive paste inside the SHE and the cavitation phenomenon, with the aim to find an optimal design, capable to ensure the best ultrasounds and mixing effects. Moreover, experimental results demonstrated that the machine can guarantee an actual simultaneous improvement of the olive oil extraction yield, as well as of the product quality. Finally, the results from sensory evaluations are summarized confirming the goodness of EVOO obtained by means of US

Cortical thinning and clinical heterogeneity in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) has heterogeneous clinical features that could be translated into specific patterns of brain atrophy. In the current study we have evaluated the relationship between different clinical expressions of classical ALS and measurements of brain cortical thickness. Cortical thickness analysis was conducted from 3D-MRI using FreeSurfer software in 29 ALS patients and 20 healthy controls. We explored three clinical traits of the disease, subdividing the patients into two groups for each of them: the bulbar or spinal onset, the higher or lower upper motor neuron burden, the faster or slower disease progression. We used both a whole brain vertex-wise analysis and a ROI analysis on primary motor areas. ALS patients showed cortical thinning in bilateral precentral gyrus, bilateral middle frontal gyrus, right superior temporal gyrus and right occipital cortex. ALS patients with higher upper motor neuron burden showed a significant cortical thinning in the right precentral gyrus and in other frontal extra-motor areas, compared to healthy controls. ALS patients with spinal onset showed a significant cortical thinning in the right precentral gyrus and paracentral lobule, compared to healthy controls. ALS patients with faster progressive disease showed a significant cortical thinning in widespread bilateral frontal and temporal areas, including the bilateral precentral gyrus, compared to healthy controls. Focusing on the primary motor areas, the ROI analysis revealed that the mean cortical thickness values were significantly reduced in ALS patients with higher upper motor neuron burden, spinal onset and faster disease progression related to healthy controls. In conclusion, the thickness of primary motor cortex could be a useful surrogate marker of upper motor neuron involvement in ALS; also our results suggest that cortical thinning in motor and non motor areas seem to reflect the clinical heterogeneity of the disease. © 2013 Mezzapesa et al

Effects of Ultrasound and Green Synthesis ZnO Nanoparticles on Biogas Production from Olive Pomace

Abstract Agro-biomass residues can play a crucial role in promoting the fossil-fuel replacement in agro-food farms. Apulia, a region in Southern Italy, concentrates 22% of farms and 57% of total national olive and olive oil production, resulting the leader producer of the Country. So that, a high quantity of biomass (olive pomace) can be recovered from the milling process. This study investigates the biogas production that occurs during the anaerobic digestion of olive pomace by means of an ultrasound pre-treatment or by means of green synthesis of ZnO Nanoparticles mixed with olive pomace, in order to facilitate its digestion or co-digestion. Measurement of dry matter and biogas produced volume during the anaerobic process were investigated starting from 3-phase and 2-phase olive pomace by means of high specific energy and low frequency ultrasound values. The results highlight a promising influence of ultrasound pre-treatment useful at increasing the biogas yield of olive pomace