Design analysis and development of a high temperature actuator for gas turbine blade tip clearance control

During a typical startup cycle industrial gas turbine blades experience rapid radial thermal expansion while bulky shroud structure with larger thermal inertia requires much longer period to reach its operating temperature. Turbine designers have to leave a safe radial distance in order to prevent contact of blades to the surrounding annular casing. However, when thermal steady state in the turbine stage is achieved, shroud and casing grow and excessive amount of blade-shroud clearance remains. Engine efficiency is very sensitive to blade-shroud clearance. Just one millimeter of radial blade tip gap in fist stage turbine section of a 150 MW class engine leads to 4% efficiency drop due to blade tip leakage. To achieve better efficiency or higher power, turbine blade tip clearance has to be controlled. Attempts to address blade tip clearance problem were not applicable as designs were bulky and complex which required excessive modification on the turbine hardware and design. The goal of this study is to design, analyze and develop a low-cost and compact actuator system which is capable of controlling the tip clearance up to 0.25mm at elevated temperatures. Actuator will be positioned between inner and outer shrouds of the casing to force the inner shroud radially away from the blades during transients, and allow it to come back towards the blades when casing reaches operating temperature to decrease the tip leakage during steady state. Different actuator designs have been studied and finite element analysis solutions have been obtained for deflection and stress. Low cycle fatigue life of the actuator has been estimated via Coffin-Manson criterion. An experimental setup has been designed and fabricated to validate the simulation results. Furthermore, since actuator will be subjected to wear at elevated temperatures due to mechanical loading and vibrations in the gas turbine, friction and wear behavior of candidate actuator materials has to be investigated. High temperature scuffing combined with rapid oxidation can lead to failures and dramatic reductions service life. Therefore, another experimental setup has been developed to conduct friction and wear tests of the candidate actuator materials, i.e. Nickel and Cobalt based superalloys Haynes 25, 188 and 214. The tests have been conducted at 20, 200,400 and 540 °C. Overall, the results indicated that the compact actuator can achieve 0.25 mm tip clearance reduction leading to 1% efficiency increase for 880 startup cycles

Quelle similitude de la faune saproxylique des vieux chênes (Quercus spp.) entre la Turquie et la Suède?

The number of old oaks has decreased during the last century and the saproxylic insects associated with the oak are one of the most endangered organism group all over Europe and Turkey. The beetle fauna on old hollow oaks was studied in Sweden and Turkey with window- and pit-fall traps. The most species rich families in the study were Anobidae and Tenebrionidae. The number of saproxylic beetle species was higher at the Turkish sites in comparison with the Swedish. This was most obvious for the families Elateridae, Cleridae, Anobiidae and Tenebrionidae. The overlap among the saproxylic beetle species at the sites in Turkey and Sweden was small. Only 14 (8%) of the 166 species found were shared between the sites in the two countries, most of them being Tenebrionidae. Many of the found beetle species are very rare and can be found on national redlists in many European countries. One good example is the Violet click beetle (Limoniscus violaceus) found at one of the Turkish sites. It is a very rare beetle all over its European range and is listed in Annexe II of the EC Habitat Directive. Three species from the family Staphylinidae were new to science and have been described as Hesperus gozukarai, H. turcicus and H. auricomusLe nombre des vieux chênes a chuté durant le siècle passé et les insectes saproxyliques associés au chêne sont l'un des groupes d'organismes les plus menacés dans l'ensemble de l'Europe et en Turquie. Les coléoptères des vieux chênes creux ont été étudiés en Suède et en Turquie avec des pièges à vitre et des pièges-fosses. Les familles les plus riches en espèces furent les Anobidae et les Tenebrionidae. Le nombre d'espèces de coléoptères saproxyliques était plus élevé sur les sites turcs que sur les suédois. Cela était le plus évident pour les Elateridae, Cleridae, Anobiidae et Tenebrionidae. Le recouvrement des listes de coléoptères saproxyliques entre les sites turcs et suédois était faible. Seules 14 (8%) des 166 espèces trouvées étaient communes aux sites des deux pays, la plupart étant des Tenebrionidae. Beaucoup des coléoptères trouvés sont des espèces rares qui figurent sur les listes rouges de beaucoup de pays européens. Un bon exemple en est Limoniscus violaceus trouvé sur l'un des sites turcs. C'est un coléoptère très rare sur l'ensemble de son aire de répartition européenne et il est inscrit en Annexe II de la Directive Habitat de la Communauté européenne. Trois espèces de la famille des Staphylinidae étaient nouvelles pour la science et ont été décrites comme Hesperus gozukarai, H. turcicus et H. auricomus

Personalized reference intervals - Statistical approaches and considerations

Under embargo until: 2022-12-13For many measurands, physicians depend on population-based reference intervals (popRI), when assessing laboratory test results. The availability of personalized reference intervals (prRI) may provide a means to improve the interpretation of laboratory test results for an individual. prRI can be calculated using estimates of biological and analytical variation and previous test results obtained in a steady-state situation. In this study, we aim to outline statistical approaches and considerations required when establishing and implementing prRI in clinical practice. Data quality assessment, including analysis for outliers and trends, is required prior to using previous test results to estimate the homeostatic set point. To calculate the prRI limits, two different statistical models based on ‘prediction intervals’ can be applied. The first model utilizes estimates of ‘within-person biological variation’ which are based on an individual’s own data. This model requires a minimum of five previous test results to generate the prRI. The second model is based on estimates of ‘within-subject biological variation’, which represents an average estimate for a population and can be found, for most measurands, in the EFLM Biological Variation Database. This model can be applied also when there are lower numbers of previous test results available. The prRI offers physicians the opportunity to improve interpretation of individuals’ test results, though studies are required to demonstrate if using prRI leads to better clinical outcomes. We recommend that both popRIs and prRIs are included in laboratory reports to aid in evaluating laboratory test results in the follow-up of patients.publishedVersio

List Decoding of Short Codes for Communication over Unknown Fading Channels

In this paper, the advantages of list decoding for short packet transmission over fading channels with an unknown state are illustrated. The principle is applied to polar codes (under successive cancellation list decoding) and to general short binary linear block codes (under ordered-statistics decoding). The proposed decoders assume neither a-priori knowledge of the channel coefficients, nor of their statistics. The scheme relies on short pilot fields that are used only to derive an initial channel estimate. The channel estimate is required to be accurate enough to enable a good list construction, i.e., the construction of a list that contains, with high probability, the transmitted codeword. The final decision on the message is obtained by applying a list. This allows one to use very few pilots, thus reducing the the Rayleigh block-fading channel and compared to finite-length performance bounds. The proposed technique provides (in the short block length regime) gains of 1 dB with respect to a traditional pilot-aided transmission scheme

Evaluation of oregano (Origanum vulgare) essential oil supplementation on growth performance, digestive enzymes, intestinal histomorphology and gut microbiota of Black Sea salmon, Salmo labrax

This study aimed to determine the effect of dietary oregano (Origanum vulgare) essential oil (EO) on the growth performance, digestive enzyme activity, intestinal histomorphology, and intestinal microbiota of the Black Sea salmon juvenile (Salmo labrax). Fish were fed diets different levels of oregano EO such as 50, 100, 200, and 400 mg kg-1. For this purpose, a total of 675 fish were distributed randomly in triplicate into 5 experiment groups in 15 experiment tanks. Fish with average initial weights of 3.52±0.01 g were fed by hand at 3% of live weight for 90 days. At the end of the study, feeding with oregano EO supplementation did not significantly affect the growth performance of fish. Except for pepsin, there were no significant differences in the activity of digestive enzymes among the control and oregano EO groups. Besides, oregano EO at the doses of 50 or 400 mg kg-1 may have the potential to increase the surface area required for digestion by increasing intestinal villi length. Moreover, all doses of oregano EO showed antimicrobial properties by decreasing the count of lactic acid bacteria in the intestine. Supplementation with 100 and 200 mg kg-1 oregano EO in diets decreased the total coliform, Escherichia coli and lactic acid bacteria counts when compared to the control group. The results showed that oregano EO may positively affect digestion and absorption without adverse effects on the growth performance of Black Sea salmon juvenile. © 2022 Osman Tolga Özel et al., published by Sciendo