This paper proposes a theoretical study of some alternative solutions to improve the blade cooling in the heavy-duty gas turbine. The study moves to the evaluations of the air coolant reduction ...temperature effects, considering two different methods: a water surface exchanger (WSE) and a cold water injection (CWI). A logical development of these possible cooling system improvements is the steam cooling application, particularly suitable for mixed or combined gas–steam cycles; the steam cooling is evaluated using open and closed loop configurations; the possible interaction of steam and air cooling is also studied. All the simulation is realized with a family of modular codes developed by authors and the study is conducted with the analysis of the characteristic cooling parameters (efficiency, effectiveness) and by the evaluation of blade temperature distribution. The study is related to a typical configuration of heavy-duty rotor blade with a standard air cooling scheme and the possible variations are related to coolant characteristics only. The results show the interesting possibility due to air coolant temperature reductions, particularly for the CWI method, but the steam cooling turns out to be more incisive. All of the considered techniques show the possibility of a mass coolant reduction and/or the possibility of a maximum cycle temperature increase in comparison to the standard air-cooling. The best results are obtained for an innovative closed–open/steam–air cooling system.
We discuss the effects of turbine-blade cooling on HAT-cycle performance. The performance depends on the location for cooling by air bleeding; four possible locations have been explored. A parametric ...analysis was performed to verify pressure-ratio and turbine-inlet-temperature (TIT) effects. An exergetic analysis was used to clarify the differences between bleed-air point options and cycle-configuration choices.
The continuing need to improve both the efficiency and the specific power of gas turbines requires to progressively increase the temperatures of the turbine inlet.
Because the first stator blades are ...heavily thermally loaded, efficient blade cooling is necessary.
The cooling system is particularly delicate and its design must follow these guidelines:
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minimum thermodynamic and fluid dynamic losses;
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limited blade temperature even for reduced cooling mass flow.
Although the problem is important, analyses of possible designs are not common in literature and many constructors refer to practical experience and to various experimental results.
This paper presents a comparative investigation to determine the effects of internal and external cooling in the same blade, on the basis of different combined solutions as it often happens. The cooling model will be considered one-dimensional: the limitation in the accuracy of the results is by far overcome by the simplicity and versatility of the approach. Finally, practical hints for designing an effective cooling system are derived, with particular attention to impingement. Then, global cooling parameters and medium blade will be determined in off-design condition.
Modélisation d'un système de refroidissement d'aubage de turbine à gaz. La nécessité d'accroître la puissance et le rendement des turbines à gaz requiert une élévation régulière de la température maximale du cycle.
Les sollicitations thermiques étant très fortes, le refroidissement de l'aubage est indispensable.
Le système de refroidissement à l'étude est très délicat et doit parvenir à ces résultats:
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contenir les pertes thermo-fluidodynamiques,
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garantir un bon fonctionnement même avec un débit réduit du fluide de refroidissement.
Dans cet article, nous présentons une étude comparative des différentes solutions possibles pour le refroidissement d'un aubage de turbine à gaz pour application industrielle. Les résultats montrent la possibilité de calculer la distribution de la température sur l'aubage afin d'optimiser sa répartition ainsi que son comportement en condition de charge partielle.
With purpose to verify the epidemiological value of the Rheumatoid Factor's variations over time, we studied: 421 RA at first hospitalization (from 1976 to 1985; Group A); 348 consecutive RA with ...follow-up at 0, 6, 12, 24, and 48 months (Group B); 750 subjects, chosen at random from a healthy population, before and after 48 months (Group C). Five agglutination tests were used: three latex tests with human (2) and rabbit (1) IgGs; one red cells test on slide, and one in tube. The results were: uneven variations in positive results in all tests (Group A); the maximum confirmation of the basic profile are provide in short-term follow-up; in subsequent follow-ups, with the exclusion of the case of all the negative tests, the remaining profiles have a decreasing confirmation rate (Group B); the positive frequency is different in all the tests; this trend is sustained at follow-up (4 years later) in spite of the overall increase of positive results (Group C). Serum-positive RA, according to all or many tests, tend to reduce the number of positive results; healthy subjects (with few positive tests) tend to increase the number of positive results over time. RA with all the negative tests have a reasonably constant profile.
The literature on atmospheric particulate matter (PM), or atmospheric aerosol, has increased enormously over the last 2 decades and amounts now to some 1500-2000 papers per year in the refereed ...literature. This is in part due to the enormous advances in measurement technologies, which have allowed for an increasingly accurate understanding of the chemical composition and of the physical properties of atmospheric particles and of their processes in the atmosphere. The growing scientific interest in atmospheric aerosol particles is due to their high importance for environmental policy. In fact, particulate matter constitutes one of the most challenging problems both for air quality and for climate change policies. In this context, this paper reviews the most recent results within the atmospheric aerosol sciences and the policy needs, which have driven much of the increase in monitoring and mechanistic research over the last 2 decades. The synthesis reveals many new processes and developments in the science underpinning climate-aerosol interactions and effects of PM on human health and the environment. However, while airborne particulate matter is responsible for globally important influences on premature human mortality, we still do not know the relative importance of the different chemical components of PM for these effects. Likewise, the magnitude of the overall effects of PM on climate remains highly uncertain. Despite the uncertainty there are many things that could be done to mitigate local and global problems of atmospheric PM. Recent analyses have shown that reducing black carbon (BC) emissions, using known control measures, would reduce global warming and delay the time when anthropogenic effects on global temperature would exceed 2 °C. Likewise, cost-effective control measures on ammonia, an important agricultural precursor gas for secondary inorganic aerosols (SIA), would reduce regional eutrophication and PM concentrations in large areas of Europe, China and the USA. Thus, there is much that could be done to reduce the effects of atmospheric PM on the climate and the health of the environment and the human population. A prioritized list of actions to mitigate the full range of effects of PM is currently undeliverable due to shortcomings in the knowledge of aerosol science; among the shortcomings, the roles of PM in global climate and the relative roles of different PM precursor sources and their response to climate and land use change over the remaining decades of this century are prominent. In any case, the evidence from this paper strongly advocates for an integrated approach to air quality and climate policies.
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