1,721,250 research outputs found
Trabocchetti nella diagnosi di addome acuto in epoca neonatale.
No full textAggiornamenti in Neonatologi
Lo Coco F, Guerriero E, Novelli V, Adami G, Cozzi F, Emissioni di policlorodibenzodiossine, policlorodibenzofurani, idrocarburi policiclici aromatici e policlorobifenili nell’industria cementiera: tecniche di campionamento ed analisi dei dati
No full textEffects of Confinement and Reynolds Number Variation on the Flow Field of Swirling Jets
No full textSwirling jets are commonly used in the burners of gas turbines to enhance mixing or to stabilize the flames. In this manuscript, a stereo (3C2D) particle image velocimetry (SPIV) was applied to examine the near exit region of an isothermal swirling jet inside an octagonal-shaped combustion chamber with a focus on the effects of confinement and Reynolds number (Re) variation on the swirling flow field. Measurements were performed on an axial plus tangential entry swirl burner with a geometric swirl number (Sg) of 1.8 and two different Re, corresponding to 10,900 and 21,800. The results observed in our experimental work are scaled appropriately with the swirl number based on the flux of the axial momentum. The contours of the mean axial velocity field reveal the occurrence of vortex breakdown (VB) for the confined jets compared to the unconfined jets for both Reynolds numbers. Upon confinement, the flow field is dominated by the existence of VB with a wider central recirculation zone (CRZ) and with enhanced axial velocity fluctuations. The enhancement in the Re further increased the CRZ and enhanced the magnitudes of the mean axial velocity and its fluctuations. The outcome obtained from these results includes a better knowledge of the swirl jet in the swirl burner's near region. In addition, the experimental data can be useful for validating computational fluid dynamics (CFD) modeling
Numerical predictions of flashback limits of H2-enriched methane/air premixed laminar flames
Full text linkHydrogen is considered as a promising resource for decarbonizing not just the industrial sector but also domestic heating systems. By partially substituting natural gas with hydrogen, domestic combustion-based conversion systems have the potential to enhance efficiency, decrease carbon emissions, and achieve cleaner combustion, specifically reducing levels of particulate matter. Nevertheless, hydrogen possesses properties that differ significantly from natural gas. In particular, due to its higher laminar flame speed, hydrogen has a much higher propensity to flashback than natural gas, raising notable safety concerns. This study aims to examine the impact of H2 addition (up to 100%) to natural gas on the combustion process in domestic condensing boilers. To achieve this objective, 3D numerical simulations are conducted, modeling the multi-hole geometry that emulate perforated burners commonly found in these appliances. The simulations incorporate detailed kinetics and conjugate heat transfer with the burner plate and consider various hole-to-hole distances for a more comprehensive analysis. Flashback limits are found for a wide range of operating conditions of interest for domestic applications, with equivalence ratios from 0.5 to 1 and hydrogen fractions from 0 (pure methane) to 1 (pure hydrogen). The results confirm the observations of previous works on planar, multi-slit configurations. More specifically, the results shows that the conventional flashback correlation based on the concept of critical velocity gradient becomes inaccurate for H2 fractions larger than 0.50 as it does not take into account stretch induced preferential diffusion effects, which are especially large in the multi-hole configuration here investigated
Renal function up to the 5th decade of life after nephrectomy in childhood: a literature review
No full textThe aim of the present study was to find out if in children ablation of 50% of renal mass may be associated with a progressive renal damage (Brenner’s hypothesis). We collected 1035 adult or adolescent survivors who underwent nephrectomy for unilateral oncological or non-oncological causes during childhood. Stratification of all survivors for age revealed that the number of subjects with blood hypertension and/or renal dysfunction (glomerular filtration rate < 90 mL/min per 1.73 m2) to be significantly higher in survivors ≥30 years old in comparison with younger patients. Available data on long-term renal function after nephrectomy during childhood support the Brenner’s hypothesis
Comment on: Long-term renal function after treatment for unilateral nonsyndromic Wilms’ tumor - A personal perspective
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