294 research outputs found
High-Fidelity Computational Analysis of the Aerothermal Performance of In-serviced Jet Engine Blades
In today’s civil aviation, the struggle for higher jet engine efficiencies has pushed the manufactures into the continuous challenge of developing new and better design and optimization strategies. In the information age, it is only natural that a great deal of this effort is going to be carried out by means of computational analysis. That is to say, these design and optimization strategies rely heavily on the use of computational models, and thus the search for a better design is hinged upon the search for a better model. A notable product of this search is the “robust design” philosophy, which aims to consider the variability in geometry and operating conditions that every component will invariably experience in real-world conditions. In general, the key element in this evolution process is for the model to be capable of accounting for more and more aspects of the reality of the problem at hand, while still being affordable in terms of computational costs. In this case, the problem is represented by the aero-thermal behavior of the jet engine’s most characteristic components: the blades.
As mentioned above, to increase the fidelity of the model, key aspects that characterize the real operation of these components can be included in it, beginning with the geometry. While most of the computational performance analysis is conducted on nominal designs, it is important to consider that, during most of their service life, the turbine blades are going to operate with a geometry that is increasingly affected by deviation from nominal. This is due to both manufacturing variation and in-service damage. These geometric deviations can be measured on the blades after an engine overhaul, providing highly useful information on the damage modes of the engine. By digitalizing these geometries, engineers can quantify and parametrize the geometric deviation. Furthermore, by creating computational grids around these geometries, a high-fidelity CFD study revolving around the performance of the real blades can be carried out, shedding light on the correlation between the geometric deviation parameters and aerodynamic performance loss. Naturally, this geometric deviation also has a significant impact on the thermal behavior of the blades, affecting the distribution of the Heat Transfer Coefficient (HTC) over the blades’ surfaces.
Even when modelling the nominal case, it is often common practice to use a simplified version of the geometry, where the internal cooling system is replaced with source terms. Although this reduces the costs of the CFD simulations, it obviously subtracts from the model’s accuracy. Furthermore, it is particularly important to model the fluid-solid thermal exchange, and the rotor-stator unsteady interaction.
All these fidelity-related aspects that can impact the model’s accuracy are investigated in the present work
L'«Avvizzimento» del cartamo (<i>Carthamus tinctorius</i> L.) causato da <i>Verticillium dahliae</i> Kleb.
The wilt of safflower (Carthamus tinctorius L.) by Verticillium dahliae Kleb., hitherto unreported in Italy,
has been found on last two years in Sardinia.
The disease symptoms and the pathogen characters are described.
Artificial inoculation tests allowed to state that our isolate is highly virulent to this host
Experimental determination of the particle dynamics into a rotating tube
This paper reports the procedure for analysing the biomass powder bed characteristics realized in an experimental pyrolysis reactor. The reaction apparatus is made of a quartz tube which can rotate, horizontally or slightly inclined, with different speeds. Depending on the tube inclination and rotation, different motion conditions (regime, hold-up, residence time and advancing rate) are possible; also the particle characteristics (nature, shape and size, humidity) and the flow rate affect the bed behaviour. After taking some pictures of the bed from the discharge side, they can be analysed by means of the geometry rules; this procedure is here described. In this way the bed profile can be obtained, and this information can be used to calculate the parameters of a proper model, already developed. The methodology here presented will be used in the future to find data to be used in the development of a whole pyrolysis process model including also heat exchange, gas fluid dynamics and pyrolysis reaction kinetics
Kinetic modelling of the gas-phase water oxidation of light hydrocarbons
The conversion of solid and liquid fuels to gas, whenever possible, is an important way for improving the efficiency and cleanness of processes. This paper presents the kinetic modelling of the water oxidation of light hydrocarbons in the gas phase at 500 °C with mixtures of heptane and water in different amounts. The aim of the work was to find information about kinetics of the homogeneous chemical reactions which take place in the gas phase during the biomass processing, particularly pyrolysis, performed with water steam as the oxidizing reactant. The experimental data here used were obtained by a continuous stainless steel reactor placed inside a heated muffle oven and maintained at a constant temperature. The gaseous product, after separation of the condensable components, was analysed by an in-line gas chromatograph. The apparatus showed to be effective for future operations with different experimental conditions (temperature and feed). The obtained data will be integrated with those coming from parallel studies about the biomass wet pyrolysis for gas production
Prove di lotta contro il <i>Cladosporium cucumerinum</i> Ell. <i>et</i> Arth. agente della «cladosporiosi» dello zucchino
The results of control trials against Cladosporium cucumerinum Ell. et Arth. artificially inoculated on
aged pumpkin plants and in soil belore seeding, are referred. All the tested fungicides (benomyl, captafol,
chlorothalonil, iprodione, mancozeb, procymidone, thiram, thyophanate-methyl), although with dlfference
according to the kind of treatment, limited infections powerfully. Thyophanate-methyl and benomyl in foliar
sprays, thyophanate-methyl and chlorothalonil in soil drench, thyophanate-methyl, benomyl and captafol
in seed dressing, gave best results.
By these results, tha Authors point out that a very good control of pumpkin scab is attainable avoiding
primary infections on seedlings by soil drench and se ed dressing
Il «Marciume molle» dei frutti di pomodoro da <i>Pseudomonas virdiflava</i> (Burkholder) Dowson
The Authors report on the results of researches about a serious soft rot of greenhouse tomato fruits in
southern Sardinia (Italy).
The disease symptoms and the characteristics of the causal agent, identified by its morphological and
cultural characters, and by biochemical and serological lests, as Pseudomonas viridiflava (Burkholder)
Dowson, are described
La «Cladosporiosi» dello zucchino (<i>Cucurbita pepo</i> L.) in coltura protetta in Sardegna
On last years the «scab» of pumpkin (Cucurbita pepo L.) induced by Cladosporium cucumerinum Ell. et
Arth. has been observed very damaging on greenhouse cultures in southern Sardinia (Italy). The disease
symptoms and epidemiology, as well as the pathogen's characters, are described.
Finally, control means are briefly reviewed
L'«Alternariosi» del cartamo (<i>Carthamus tinctorius</i> L.) da <i>Alternaria cartami</i> Ch. in Sardegna
A stem and leaf spot of safflower by Alternaria carthami Ch. has been found on last three years in Sardinia
(Italy).
The disease symptoms and the pathogen characters are described. The susceptibility of 7 safflower expe
rimental cvs. has been assessed, and by artificial inoculations the fungus pathogenicity was checked.
Finally, the Authors examine some epidemiological aspects of the disese and briefly expose the control
means
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