1,720,990 research outputs found
Experimental investigation on the flow field and performances of a Savonius-Darrieus wind turbine
No full textIn this paper, measurements performed on a vertical axis wind turbine (VAWT) model are reported. The turbine is a combination of Savonius and Darrieus rotors to optimize performances in medium-low wind regimes. To this end, the turbine is positioned into a wind-tunnel to derive instantaneous and averaged velocity fields by means of Particle Image Velocimetry (PIV). PIV data allow to derive specific fluid flow phenomena on each single and on combined geometrical configurations. These results are also compared with electrical measurements to determine performances, efficiency and the best working conditions
HYBRI – A combined Savonius-Darrieus wind turbine: Performances and flow fields
No full textIn this paper, wind tunnel measurements on a model of a vertical axis wind turbine (VAWT) are reported. The turbine is a novel hybrid Savonius-Darrieus combined rotor which aims optimizing performances in medium-low wind regimes, by using a careful design of the shape, size and relative positions of Savonius and Darrieus blades. To this end, a dynamically scaled turbine model is tested in wind tunnel to derive instantaneous and averaged velocity fields by means of Particle Image Velocimetry (PIV), which allows deriving wakes and specific fluid flow phenomena on each single configuration (Savonius or Darrieus) and interactions on the combined geometry. These results are coupled with electrical measurements to determine global performances, efficiency and best working conditions for each separate turbine and for the combined turbine. Data are also compared with results obtained by other authors in previously reported combined hybrid configurations. The proposed system is able to work with good performances (power coefficient equal or slightly lower than 0.2), on an extended range of operative conditions, covering those of each component alone, i.e. for tip speed ratios between 0.5 and 4, in comparison to the ranges 0.5 ÷ 1 and 1.7 ÷ 4 of the used Savonius and Darrieus components. Motivations for the increased performances and working ranges reached by the proposed combined turbine, especially in the low tip speed ratio regime, are given as derived from detailed PIV velocity measurements
V. Indovina, M. Occhiuzzi, D. Pietrogiacomi and S. Tuti “The surface composition of CuOX/ZrO2 catalysts as determined by FTIR, XPS, ESR spectroscopies and volumetric CO adsorption” J. Phys. Chem. B (1999) 103, 9967-9977
No full textCuOx/ZrO2 samples were prepared and characterized by means of FTIR,XPS,ESR,DRS, volumetric CO adsoption, redox cycles with H2 and O2
Decomposition of nitrous oxide on CoOx/ZrO2, CuOx/ZrO2 and FeOx/ZrO2 catalysts
No full textCuOx/ZrO2, CoOx/ZrO2 and FeOx/ZrO2 catalysts were characterized and studied for the decomposition of nitrous oxid
CoOx/sulphated-ZrO2 and CoSO4/ZrO2 as catalysts for the abatement of NO with C3H6 in the presence of excess O2
No full textCobalt-sulphated zirconia catalysts were prepared by two different methods and characterized by UV-Vis, DRS, XRD, XPS and FTIR spectroscopies. Samples were tested for the NO reduction with C3H6 in the presence of excess O2
Experimental and Numerical Investigation of Flow Control on Bluff Bodies by Passive Ventilation
No full textThis chapter investigates flow control on bluff bodies by passive ventilation. Natural or passive ventilation drag reduction method is examined experimentally and numerically in the chapter. Passive ventilation is performed by directly connecting the high pressure region at the front of a body to the lower pressure in the near wake using a venting duct; so far, it is able to establish a net mass flux into the wake. In particular, in aerodynamic applications it seems to be suitable to attain a global reduction of the drag of a body moving in a fluid and a reduction of turbulence levels by means of a global modification of the body wake. Velocity field investigations using particle image velocimetry measurements and numerical Reynolds averaged code are employed at moderately high Reynolds numbers to clarify the effectiveness of drag reduction on a vented bluff body. The numerical and experimental results agree qualitatively, but the amount of reduction for the vented body (about 10%) is underestimated numerically. Direct balance measurements are used for comparisons. © 2005 Elsevier B.V. All rights reserved
Simultaneous abatement of NO and N2O with CH4 over modified Al2O3 supported Pt,Pd,Rh
No full textPt, Pd and Rh supported on Al2O3-SiO2 and Al2O3-ZrO2, prepared by adsorbing noble metal ions from salt aqueous solutions on well-mixed supports, were characterized by XRD, N2 physisorption and FESEM, and studied for the simultaneous abatement of NO and N2O by selective catalytic reduction in the presence of O2 using CH4 as reductant (SCRsim). To give a better insight into the simultaneous process, the reactions related to SCRsim (SCRNO, SCRN2O, CH4 combustion), as well as the abatements in the absence of O2 (CRsim, CRNO, CRN2O), and the N2O decomposition by itself and in the presence of O2 and NO, were investigated. The catalytic measurements were performed in a flow apparatus with GC analysis of reactants and products. Catalytic results showed that Pt,Pd,Rh/Al2O3-SiO2 and Pt,Pd,Rh/Al2O3-ZrO2 are effective catalysts for SCRsim above 400 °C from feeds containing O2/CH4 less than 1, yielding complete NO and N2O conversions and complete selectivity to CO2 and N2. At lower temperatures, N2O and NO are unconverted and only the competitive CH4 combustion occurs. Compared to the separate NO and N2O abatement reactions, a slight shift in activity towards higher temperatures occurs in SCRsim. Such a shift can be related to the possible formation of strongly adsorbed NOy-like species formed in the presence of NO and competing with the N2O adsorption sites. The poisoning effect of these species disappears above a threshold-like temperature (about 300 °C), suggesting that above this temperature the high surface-O mobility, guaranteeing a partial reduction of the noble metal ions by CH4, sustains the reductive reactions of both NO and N2O
Cobalt supported on ZrO2: catalysts characterisation and their activity for the reduction of NO with C3H6 in the presence of excess O2
No full textCoOx/ZrO2 catalysts, prepared by impregnation were characterized by beams of DRS, XPS, FTIR and volumetric CO adsorption. Catalysts awere studied for the catalytic activity for NO reduction with propene in the presence of O2
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