Showing papers by "Sebastian Brusca published in 2018"

Dynamic performance evaluation of photovoltaic power plant by stochastic hybrid fault tree automaton model

Abstract: The contribution of renewable energies to the reduction of the impact of fossil fuels sources and especially energy supply in remote areas has occupied a role more and more important during last decades The estimation of renewable power plants performances by means of deterministic models is usually limited by the innate variability of the energy resources The accuracy of energy production forecasting results may be inadequate An accurate feasibility analysis requires taking into account the randomness of the primary resource operations and the effect of component failures in the energy production process This paper treats a novel approach to the estimation of energy production in a real photovoltaic power plant by means of dynamic reliability analysis based on Stochastic Hybrid Fault Tree Automaton (SHyFTA) The comparison between real data, deterministic model and SHyFTA model confirm how the latter better estimate energy production than deterministic model

Internal combustion engine heat release calculation using single-zone and CFD 3D numerical models

Abstract: The present study deals with a comparative evaluation of a single-zone (SZ) thermodynamic model and a 3D computational fluid dynamics (CFD) model for heat release calculation in internal combustion engines. The first law, SZ, model is based on the first law of thermodynamics. This model is characterized by a very simplified modeling of the combustion phenomenon allowing for a great simplicity in the mathematical formulation and very low computational time. The CFD 3D models, instead, are able to solve the chemistry of the combustion process, the interaction between turbulence and flame propagation, the heat exchange with walls and the dissociation and re-association of chemical species. They provide a high spatial resolution of the combustion chamber as well. Nevertheless, the computation requirements of CFD models are enormously larger than the SZ techniques. However, the SZ model needs accurate experimental in-cylinder pressure data for initializing the heat release calculation. Therefore, the main objective of an SZ model is to evaluate the heat release, which is very difficult to measure in experiments, starting from the knowledge of the in-cylinder pressure data. Nevertheless, the great simplicity of the SZ numerical formulation has a margin of uncertainty which cannot be known a priori. The objective of this paper was, therefore, to evaluate the level of accuracy and reliability of the SZ model comparing the results with those obtained with a CFD 3D model. The CFD model was developed and validated using cooperative fuel research (CFR) engine experimental in-cylinder pressure data. The CFR engine was fueled with 2,2,4-trimethylpentane, at a rotational speed of 600 r/min, an equivalence ratio equal to 1 and a volumetric compression ratio of 5.8. The analysis demonstrates that, considering the simplicity and speed of the SZ model, the heat release calculation is sufficiently accurate and thus can be used for a first investigation of the combustion process.

Hydrogen production from residual biomass via air-steam gasification for a bioenergy-based economy in Sicily

Abstract: This work aims at evaluating the potential impact of hydrogen production in Sicily by citrus peel air-steam gasification. The thermochemical behavior of such feedstock was evaluated in a previous work by means of a bench-scale fluidized bed reactor operate at different temperature and steam to biomass ratios. A virtual scale-up of the gasification system was developed in order to assess the combined hydrogen and power production potential. The downstream processes of syngas, i.e. hydrogen separation through Pressure Swing Adsorption (PSA) and off-gas combustion in engines for power production, were simulated considering the efficiencies reported in literature and datasheets. The results of this study show that, depending on the gasifier operating conditions, from 1,000 to 1,414 t/year of hydrogen can be produced by exploiting the totality of available citrus peel in Sicily (33,000 t/year). It has been estimated that from 927 to 15,900 MWh/year of electricity can be produced, in combination with hydrogen, by internal combustion engines and exported to the national grid, while the recovered heat may be used for the citrus peel drying. RÉSUMÉ. Cet article vise à évaluer l’impact potentiel de la production d’hydrogène en Sicile par la gazéification d’air-vapeur à écorces d’agrumes. Le comportement thermochimique de cette matière première a été évalué dans un travail précédent au moyen d'un réacteur à lit fluidisé à l'échelle du laboratoire fonctionnant à différentes températures et différents rapports vapeur / biomasse. Une mise à l'échelle virtuelle du système de gazéification a été développée afin d'évaluer le potentiel combiné de production d'hydrogène et d'électricité. Les processus en aval du gaz de synthèse, à savoir la séparation de l’hydrogène par adsorption à pression modulée (APM) et la combustion des effluents gazeux dans les moteurs de production d’énergie, ont été simulés en tenant compte des rendements rapportés dans la littérature et les fiches techniques. Les résultats de cette étude montrent que, selon les conditions de fonctionnement du gazéificateur, il est possible de produire de 1 000 à 1 414 t / an d'hydrogène en exploitant la totalité des écorces d'agrumes disponibles en Sicile (33 000 t / an). Il a été estimé que de 927 à 15 900 MWh / an d'électricité peuvent être produits combinant à l'hydrogène par des moteurs 442 ACSM. Volume 42 – n° 3/2018 à combustion interne et être exportés vers le réseau national, tandis que la chaleur récupérée peut être utilisée pour le séchage des écorces d'agrumes.

A Detailed Analysis of the Centrifugal Pumping Phenomenon in HAWTs Through the Use of CFD Models

Abstract: The centrifugal pumping, also known as rotational augmentation, is a 3D phenomenon which is of utmost importance in the aerodynamics of HAWTs. A clear physical explanation about the rise and development of this phenomenon is still missing in the scientific literature. Indeed, several empirical approaches have been proposed for taking into account the rotational effects inside 1D design codes. However, at the state, these approaches lead to results, which are quite different amongst each other. In the present paper the authors propose a thorough analysis of the rotational augmentation in an experimental micro HAWT. For this purpose, previously validated CFD 3D models were used. These models were developed using ANSYS Fluent solver with a calibrated RANS transition turbulence model. The post-processing analysis, presented in this paper, demonstrates that the strong increase of the aerodynamic forces is mainly due to the presence of a strong helical vortex which develops in the inner part of the blade. This vortex depressurizes the entire separated layer and it is found to be due to the combined effect of Coriolis and centrifugal forces along with the span-wise pressure gradient. Moreover, the essential contribution of the radial component of the Coriolis force was evidenced in contrast with the fact that this component is usually neglected.