1,721,262 research outputs found
Water and steam injection in micro gas turbine supplied by hydrogen enriched fuels: Numerical investigation and performance analysis
No full textThis paper investigates the energetic and environmental performance of micro gas turbine plant with two proposed concurrent improvements: the methane-based fuel enriched by hydrogen and the humidification of the plant cycle. The energetic and environmental benefits of both features are well-know, and the aim of this work is the analysis of their combined impact on the micro gas turbine operation. Despite enhancing fuel with H2 involves significant advantages like greenhouse emission reduction and a better combustion in case of low LHV fuels, most of commercial micro gas turbine combustors are not able to burn fuels with high hydrogen content unless structurally modified. On the contrary, has been demonstrated that humidified gas turbines (i.e., gas turbines with water injection, humid air turbine (HAT) and steam injection gas turbine (STIG) cycles) improve the combustion stability as well as electric power delivered and plant efficiency. Hence, in order to investigate the feasibility of the concurrent two features, the first step of this work was the thermodynamic analysis of a micro gas turbine supplied by methane-based fuels enriched with H2 up to 20%vol, considering both dry and humidified cycles. Since a combustion anomaly was detected, i.e., flashback, in the CFD study on the combustion chamber, a steam injection in the combustor has been added in the plant layout with the aim of overcoming the anomaly, and its effect on the combustion process has been analyzed also raising the hydrogen content up to 30%vol. The main outcome of this paper is the assessment of the feasibility of supplying the combustor of the proposed HGT-STIG micro gas turbine with a hydrogen enrichment up to 30%vol, achieving a safe and regular combustion mainly owing to a steam injection mass flow equal up to 125% of fuel flow
First and second law analysis of a hydro storage with respect to the environmental impact of an energy system
No full textGRAVITY HEAT PIPES AS GEOTHERMAL CONVECTORS
No full textDesign of and tests on a gravity heat pipe transmitting up to 25 kW thermal power from a surface aquifer in a volcanic area are described. This includes laboratory tests on a single pipe immersed in a thermostatically controlled water sink, which enabled determination of overall pipe conductance, and is followed by details of the design and construction of a full scale device
Primary intraventricular haemorrhage in adults
No full textINTRODUCTION:
Primary intraventricular haemorrhage (PIVH) is an uncommon type of intracerebral haemorrhage. Relatively little is known about clinical and imaging features, and even less about prognosis and predictors of mortality.
MATERIAL AND METHODS:
We analysed clinical and imaging features, causative factors and outcome of 26 patients with CT brain scan evidence of PIVH. A multivariate regression model of failure time data was used to assess predictors of in-hospital mortality.
RESULTS:
Loss of consciousness was the first manifestation of PIVH in six patients and occurred after all other symptoms in five. In other patients, onset was characterized by headache, vomiting, confusion and disorientation (n=8) or by headache with or without vomiting (n=7). Angiography revealed vascular malformations in eight patients (31%). Other possible causative factors were clotting disorder in one patient and arterial hypertension in 10. No cause was identified in seven patients. Early hydrocephalus was the most frequent complication and resolved spontaneously in a minority of patients. In-hospital mortality was high (42%): four patients died early of direct consequence of bleeding and seven died after clinical worsening because of increasing hydrocephalus or other adverse events. Multivariate analysis indicated Glasgow Coma Scale < or = 8 (OR 4.67; 95% CI 1.22-17.92) and early hydrocephalus (OR 4.93; 95% CI 1.13-21.59) as independent predictors of in-hospital mortality.
CONCLUSION:
In patients with PIVH, hydrocephalus seems to be a critical determinant of in-hospital mortality and this suggests the need for early treatment strategies
Determinazione dell'efficienza dei dispositivi per la filtrazione dell'aria negli impianti di ventilazione e di condizionamento - descrizione dell'apparecchiatura installata presso l'Istituto di Fisica Tecnica di Napoli
No full textDeterminazione dell'efficienza dei dispositivi per la filtrazione dell'aria negli impianti di ventilazione e di condizionamento - descrizione dell'apparecchiatura installata presso l'Istituto di Fisica Tecnica di Napoli
No full textClinical and electrophysiological findings and follow-up in tarsal tunnel syndrome
No full textThe authors report clinical and electrophysiological findings in 59 patients with tarsal tunnel syndrome (TTS) and follow-up in 23 of them. The entrapment was prevalent in females; was bilateral in 6 patients and involved medial plantar in 7 and lateral plantar nerves in two cases. Eleven presented with other nerve entrapment syndromes or focal mononeuropathies, due to hereditary neuropathy with liability to pressure palsy or systemic diseases. The other 48 subjects had TTS without any other related entrapment syndromes: 23 were idiopathic cases, 13 had a history of local trauma, 3 had systemic diseases and the others had external or intrinsic compressions. The most frequent symptoms were paraesthesia or dysaesthesia (86% of feet) and pain (55%). Hypoaesthesia of the sole and weakness of toe flexion were evident in 74% and 22% of feet, respectively. Absence of sensory action potential or slowing of sensory conduction velocity (SCV) of the plantar nerves were present in 77% of feet; significant differences of SCV between affected and unaffected plantar nerves and/or between distal sural and plantar nerves were evident in 14%. Abnormalities of plantar SCV were therefore absent in only 9% of feet. Distal motor latency was delayed in 55% and electromyography showed neurogenic changes in 45% of sole muscles. Five cases (6 feet) underwent surgery with excellent or good results in 5, 4 of them also showing improvement in distal conduction of the plantar nerves. Nine were treated with local steroid injections, with good results shown in 6 patients. Nine other patients who did not receive any therapy showed a disappearance of symptoms or good outcome in 6 cases. The subjects with poor therapeutic results had S1 radiculopathy or systemic diseases. The authors underline that patients with connective tissue diseases should not be treated by surgical decompression because they may have subclinical neuropathy. Some subjects with idiopathic or trauma-induced TTS recover spontaneously. Surgical release should be limited to cases with space-occupying lesions and when conservative treatments fail. Copyright (C) 1998 Elsevier Science Ireland Ltd
A bridge between CAD and LCA to optimise the life cycle inventory phase
No full textHaving environmental indications such as those provided by Life Cycle Assessment (LCA), while designing a product would reduce the time required by the trial-and-error approach resulting from environmental checks only at the end of the process, directing the development towards more sustainable solutions from the beginning. To achieve this, the design and environmental analysis should be more integrated, as well as the respective tools. The project idea discussed in this paper aims to overcome this barrier by defining an XML (eXtensible Markup Language) structure designed to carry Life Cycle Inventory data from Computer Aided Design (CAD) tools to Life Cycle Assessment tool. The idea is to exploit overlapping data between the CAD system and LCA instruments, which are currently not being considered. This process will contribute to the reduction of time required for data input and the amount of mistakes. © Springer International Publishing Switzerland 2016
Numerical Modeling of Energy Systems Based on Micro Gas Turbine: A Review
Full text linkIn the context of the great research pulse on clean energy transition, distributed energy systems have a key role, especially in the case of integration of both renewable and traditional energy sources. The stable interest in small-scale gas turbines can further increase owing to their flexibility in both operation and fuel supply. Since their not-excellent electrical efficiency, research activities on micro gas turbine (MGT) are focused on the performance improvements that are achievable in several ways, like modifying the Brayton cycle, integrating two or more plants, using cleaner fuels. Hence, during the last decades, the growing interest in MGT-based energy systems encouraged the development of many numerical approaches aimed to provide a reliable and effective prediction of the energy systems’ behavior. Indeed, numerical modeling can help to individuate potentialities and issues of each enhanced layout or hybrid energy system, and this review aims to discuss the various layout solutions proposed by researchers, with particular attention to recent publications, highlighting the adopted modeling approaches and methods
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