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On-Board Systems Preliminary Sizing in an Overall Aircraft Design Environment
No full textAn innovative aircraft preliminary design environment is presented, in particular highlighting the impacts of on-board systems design discipline on the Overall Aircraft Design, especially in terms of mass changes and fuel consumptions. The design environment has been conceived and set up during a collaboration between Politecnico di Torino and the German Aerospace Center (DLR - Hamburg). The entire design workflow is presented, focusing the attention on the subsystems design module, an in-house tool named ASTRID, developed at Politecnico di Torino. ASTRID is conceived to design both conventional and innovative systems, as hybrid-electric propulsion systems and More Electric and All Electric architectures. In particular, from the design modules of the proposed environment, system masses and secondary power levels are obtained, hence pointing out the system design effects on aircraft weights and fuel consumptions. Two case studies are presented. The first one refers to the preliminary design of a general aviation aircraft equipped with a hybrid-electric propulsion system. Several variants are designed varying the degree of hybridization, meant as the ratio between the electric power and the total propulsive power. The second case study is centered on four 90-passengers civil airplane designs with the same stakeholders' requirements but different on-board systems technology levels - i.e. ranging from a conventional architecture to the All Electric Aircraft, passing through two More Electric configurations. Each design affects differently the aircraft empty weight and the required mission fuel. At the end of the designs, it is assessed that a high degree of hybridization, around 35%, entails a drastic fuel reduction, marking the significant benefits of this innovative technology. Concerning the second case study, the most innovative concept, the All Electric Aircraft, is characterized by a significant fuel reduction due to the more efficient power off-takes and a lower empty weight compared to the traditional architecture, hence returning a lower Maximum Takeoff Weight
Experimental and numerical analyses on thermal performance of different typologies of PCMs integrated in the roof space
No full textThe study investigates the thermal performances of Phase Change Materials (PCM) integrated in a roof space to be used as a residential attic in Torino, Italy. Three different solutions were applied to a roof continuously monitored under summer climatic conditions. The roof was divided into three portions, one, the bare roof, representing the reference case without PCMs, the other two integrating two PCM's typologies with different melting/solidification temperatures range. A numerical model was furthermore developed implementing the equivalent capacitance numerical method to describe the substance phase transition and the measured data set were used for its validation. The study demonstrates that PCM-enhanced components are a promising solution toward a higher thermal performance efficiency in roof attic spaces during the summer season. Experimental results showed a reduction of the ongoing heat peak load between 13% and 59% depending on the PCM typology, highlighting that to reach the expected performance the proper PCM type should be carefully selected
Investigating cohesive healing of asphalt binders by means of a dissipated energy approach
No full textThe paper reports the results of an experimental investigation in which the cohesive healing properties of different types of asphalt binder were evaluated by means of the dissipated energy ratio approach. A specifically designed testing methodology was proposed which involves comparing the response of binders subjected to continuous oscillatory shear loading carried out without rest periods and with single rest periods introduced at predefined levels of damage A rheological parameter (Healing Ratio) was introduced to quantify the magnitude of healing occurring during rest time and to rank the consequent healing potential of binders. Obtained results indicate that the investigated binders did not completely recover their original fatigue resistance after rest time, confirming the existence of some intrinsic irreversible damage, the amount of which depends on the total damage experienced before load removal. Experimental results also indicate that healing performance of binders can be significantly enhanced by polymer modificatio
UAV OBLIQUE PHOTOGRAMMETRY AND LIDAR DATA ACQUISITION FOR 3D DOCUMENTATION OF THE HERCULES FOUNTAIN
No full textThis paper discusses some enhancements concerning 3D modelling, and the integration and comparison of 3D data from aerial and terrestrial sensors, developed by innovative geomatics techniques around the metric documentation of cultural heritage. In archaeology, it is interesting to deal with the considerable advantages of new multi-sensor approaches for the data acquisition and the management phases in terms of the sustainability (automated acquisition, quickness, precision, time and cost cutting). In particular, Unmanned Aerial Vehicles (UAVs) photogrammetry with the joint use of nadir and oblique cameras can be usefully combined with the large-scale details acquired by the terrestrial Light Detection and Ranging (LiDAR) in vast areas or complex objects, especially in mostly vertical sized objects. Here, we will report the results of an integrated 3D survey in an archaeological context in the Piedmont region of Italy. The Hercules Fountain is located in the gardens of the Venaria Reale (a Savoy Royal Palace included in the UNESCO heritage list) and has witnessed several events and historical phases during the past centuries - from its construction in the 16th century to its disuse and decline in the 17th century, right up to the 21st century when it was eventually brought back to light. The goal of the test is the creation of a 3D continuous model of the site for documentation purposes, future consolidation, and enhancement projects finalised for a public promotion. To meet these strategic aims, a terrestrial laser scanning (TLS henceforth) survey has been designed together with multi-flights by a multi-rotor UAV and terrestrial close-range photogrammetry (CRP) acquisition to produce a highly detailed 3D textured model from which we have inferred standard 2D drawings, digital orthoimages, and further 3D products. In conclusion, the entire workflow and the outputs have been compared together to evaluate the effectiveness of each elaboration according to the different goals of the survey
High temperature properties of the monolithic CVD β-SiC materials joined with a pre-sintered MAX phase Ti3SiC2 interlayer via solid-state diffusion bonding
No full textInfluence of groundwater temperature variation on thermal plume modelling in geothermal open loop systems
No full textThe Groundwater Heat Pump system is a technology that withdraws water from a well or surface water, passes it through a heat exchanger and discharges the water into an injection well or nearby river, developing a thermal plume of colder/warmer re-injected water, known as the Thermal Affected Zone (TAZ). Plumes are considered a potential anthropogenic geothermal resource or pollution, in fact they might pose a risk to groundwater use downgradient. It is then important to know early in the project whether the aquifer is suitable for the system to be implemented and whether the TAZ will interfere with existing wells, subsurface infrastructure or land use. Physical processes affecting heat transport within an aquifer include advection (or convection), mechanical dispersion and diffusion (Diao et al., 2004). Plume propagation occurs primarily through advection (Lo Russo and Taddia, 2010), and tends to "degrade" following conductive heat transport, and convection within moving water (Hecht-Mendez et al., 2010). The results of a sensitive analysis realized by Lo Russo et al. (2012) indicates that the main hydrodynamic parameters that influence the heat transport are hydraulic conductivity and gradient. As the hydraulic conductivity varies according to the temperature due to the variation of the water dynamic viscosity, in the present study we evaluate the influence on heat transport of the groundwater temperature variation induced by an open-loop system reinjection system. To investigate this topic a sensitive analysis has been realized using FEFLOW® 6.2 package developed by Diersch (2010). FEFLOW gives the possibility to include or disregard the dynamic viscosity variation related to the groundwater temperature and therefore we simulated these two scenarios. For each of them nine different cases have been considered using the combination between three different conductivity classes and three different injection temperatures values. For each case (K-Treinj) the isotherms obtained in both scenarios have been compared geometrically. The two scenarios analysed highlighted that the variation of the dynamic viscosity with the groundwater temperature affects the extension of the TAZ in the cases of higher values of aquifer hydraulic conductivity and/or in the situations of warmer injected water and therefore in these modelling contexts it should be taken into account to correctly assess the subsurface thermal perturbation. References Diao N, Li Q, Fang Z. 2004. Heat transfer in ground heat exchangers with groundwater advection. Int. J. Thermal Sci., 43: 1203-1211. Diersch H.J.G. 2010. FEFLOW 6 - User's Manual. WASY GmbH, Berlin. Hecht-Mendez J, Molina-Giraldo N, Blum P, Bayer P (2010) Evaluating MT3DMS for heat transport simulation of closed geothermal systems. Ground Water 48(5), 741-756. Lo Russo S. and Taddia G. 2010. Advective heat transport in an unconfined aquifer induced by the field injection of an open-loop groundwater heat pump. American Journal of Environmental Sciences 6(3), 253-259 DOI: 10.3844/ajessp.2010.253.259. Lo Russo S, Taddia G, Verda V. 2012. Development of the thermally affected zone (TAZ) around a ground water heat pump (GWHP) system: a sensitivity analysis. Geothermics 43:66- 74. doi:10.1016/j.geothermics.2012.02.001
Adaptive time step selection in the quasi-static methods of nuclear reactor dynamics
No full textOf the methods available by which to integrate the neutron and delayed neutron precursor balance equations in time, at present the quasi-static methods are among the most practical and favourable. However, the correct application of the quasi-static method requires the use of appropriately determined time steps, for both the reasons of accuracy and efficiency. This work presents a methodology for the adaptive selection of the time steps employed by the quasi-static method, thereby allowing the quasi-static approach to be applied in an efficient manner while maintaining a prescribed level of accuracy. The method is applied to and studied using some numeric test problems
I processi di rigenerazione urbana tra sostenibilità e innovazione. Storie e protagonisti di un'infinita opera che può determinare la nostra sopravvivenza o decretare il nostro fallimento nel futuro dell'era globalizzata
No full textLe megalopoli moderne rappresentano la vera sfida per la sopravvivenza dell' ecosistema mondiale. L'inurbamento ha concentrato in ambiti cittadini oltre il 50% della popolazione mondiale rendendo indifferibile il tema di una rivoluzione e nei modelli dell'abitare ed organizzare la città