Current Issue : October - December Volume : 2019 Issue Number : 4 Articles : 5 Articles
Modern aeronautic fans are characterised by a transonic flow regime near the blade tip.\nTransonic cascades enable higher pressure ratios by a complex system of shockwaves arising across\nthe blade passage, which has to be correctly reproduced in order to predict the performance and the\noperative range. In this paper, we present an accurate two-dimensional numerical modelling of the\nARL-SL19 transonic compressor cascade. A large series of data from experimental tests in supersonic\nwind tunnel facilities has been used to validate a computational fluid dynamic model, in which the\nchoice of turbulence closure resulted critical for an accurate reproduction of shockwave-boundary\nlayer interaction. The model has been subsequently employed to carry out a parametric study in\norder to assess the influence of main flow variables (inlet Mach number, static pressure ratio) and\ngeometric parameters (solidity) on the shockwave pattern and exit status. The main objectives of the\npresent work are to perform a parametric study for investigating the effects of the abovementioned\nvariables on the cascade performance, in terms of total-pressure loss coefficient, and on the shockwave\npattern and to provide a quite large series of data useful for a preliminary design of a transonic\ncompressor rotor section. After deriving the relation between inlet and exit quantities, peculiar to\ntransonic compressors, exit Mach number, mean exit flow angle and total-pressure loss coefficient\nhave been examined for a variety of boundary conditions and parametrically linked to inlet variables.\nFlow visualisation has been used to describe the shock-wave pattern as a function of the static pressure\nratio. Finally, the influence of cascade solidity has been examined, showing a potential reduction\nof total-pressure loss coefficient by employing a higher solidity, due to a significant modification of\nshockwave system across the cascade....
In order to solve the problems of filtering divergence and low accuracy in Kalman filter\n(KF) applications in a high-speed unmanned aerial vehicle (UAV), this paper proposed a new\nmethod of integrated robust adaptive Kalman filter: strong adaptive Kalman filter (SAKF). The\nsimulation of two high-dynamic conditions and a practical experiment were designed to verify the\nnew multi-sensor data fusion algorithm.............................
Planning and executing missions in terms of trajectory generation are challenging problems\nin the operational phase of unmanned aerial vehicles (UAVs) lifecycle. The growing adoption of\nUAVs in several civil applications requires the definition of precise procedures and tools to safely\nmanage UAV missions that may involve flight over populated areas. The paper aims at providing a\ncontribution toward the definition of a reliable environment, called FLIP (flight planner) for route\nplanning and risk evaluation in the framework of mini- and micro-UAV missions over populated areas.\nThe environment represents a decision support system (DSS) for UAV operators and other decision\nmakers, like airports authorities and aviation agencies. A new ICT tool integrating an innovative\nprocedure for evaluating the risk related to the use of UAV over populated areas is proposed....
A very interesting field of research on advanced composite materials is the possibility to integrate new functionalities and specific\nimprovements acting on the matrix of the composite by means of a nanocharged resin. In this way, the composite becomes a\nso-called â??multiscale compositeâ? in which the different phases change from nano to macro scale. For example, the incorporation of\nnanoscale conductive fillers with intrinsically high electrical conductivity could allow a tailoring of this property for the final\nmaterial. The properties of carbon nanotubes (CNT) make them an effective candidate as fillers in polymer composite systems\nto obtain ultralight structural materials with advanced electrical and thermal characteristics. Nevertheless, several problems are\nrelated to the distribution in the matrix and to the processability of the systems filled with CNT. Existing liquid molding\nprocesses such as resin transfer molding (RTM) and vacuum-assisted resin transfer molding (VARTM) can be adapted to\nproduce carbon fiber reinforced polymer (CFRP) impregnated with CNT nanofilled resins. Unfortunately, the loading of more\nthan 0.3-0.5% of CNT can lead to high resin viscosities that are unacceptable for such kind of processes. In addition to the\nviscosity issues that are related to the high CNT content, a filtration effect of the nanofillers caused by the fibrous medium may\nalso lead to inadequate final component quality. This work describes the development of an effective manufacturing process of a\nfiber-reinforced multiscale composite panel, with a tetra-functional epoxy matrix loaded with carbon nanotubes to increase its\nelectrical properties and with GPOSS to increase its resistance to fire. A first approach has been attempted with a traditional\nliquid infusion process. As already anticipated, this technique has shown considerable difficulties related both to the low level of\nimpregnation achieved, due to the high viscosity of the resin, and to the filtration effects of the dispersed nanocharges. To\novercome these problems, an opportunely modified process based on a sort of film infusion has been proposed. This\nmodification has given an acceptable result in terms of impregnation and morphological arrangement of CNTs in nanofilled\nCFRP. Finally, the developed infiltration technique has been tested for the manufacture of a carbon fiber-reinforced panel with a\nmore complex shape....
Solar sails are propellantless systems where the propulsive force is given by the momentum\nexchange of reflecting photons. Thanks to the use of shape memory alloys for the self-actuation\nof the system, complexity of the structure itself has decreased and so has the weight of the whole\nstructure. Four self-deploying systems based on the NiTi shape memory wires have been designed\nand manufactured in different configurations (wires disposal and folding number). The deployed\nsolar sails surfaces have been acquired by a Nextengine 3D Laser Scanner based on the Multistripe\nTriangulation. 3D maps have been pre-processed through Geomagic Studio and then elaborated in\ntheWolfram Mathematica environment. The planarity degree has been evaluated as level curves from\nthe regression plane highlighting marked differences between the four configurations and locating\nthe vertices as the most critical zones. These results are useful in the optimization of the best folding\nsolution both in the weight/surface reduction and in the planarity degree of the solar sail....
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