Academic literature on the topic 'Extended land beaufort scale'
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Journal articles on the topic "Extended land beaufort scale"
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Stirling, Ian, Evan Richardson, Gregory W. Thiemann, and Andrew E. Derocher. "Unusual Predation Attempts of Polar Bears on Ringed Seals in the Southern Beaufort Sea: Possible Significance of Changing Spring Ice Conditions." ARCTIC 61, no. 1 (March 1, 2009): 14. http://dx.doi.org/10.14430/arctic3.
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In April and May 2003 through 2006, unusually rough and rafted sea ice extended for several tens of kilometres offshore in the southeastern Beaufort Sea from about Atkinson Point to the Alaska border. Hunting success of polar bears (Ursus maritimus) seeking seals was low despite extensive searching for prey. It is unknown whether seals were less abundant in comparison to other years or less accessible because they maintained breathing holes below rafted ice rather than snowdrifts, or whether some other factor was involved. However, we found 13 sites where polar bears had clawed holes through rafted ice in attempts to capture ringed seals (Phoca hispida) in 2005 through 2006 and another site during an additional research project in 2007. Ice thickness at the 12 sites that we measured averaged 41 cm. These observations, along with cannibalized and starved polar bears found on the sea ice in the same general area in the springs of 2004 through 2006, suggest that during those years, polar bears in the southern Beaufort Sea were nutritionally stressed. Searches made farther north during the same period and using the same methods produced no similar observations near Banks Island or in Amundsen Gulf. A possible underlying ecological explanation is a decadal-scale downturn in seal populations. But a more likely explanation is major changes in the sea-ice and marine environment resulting from record amounts and duration of open water in the Beaufort and Chukchi seas, possibly influenced by climate warming. Because the underlying causes of observed changes in polar bear body condition and foraging behaviour are unknown, further study is warranted.
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Doxaran, D., E. Devred, and M. Babin. "A 50 % increase in the mass of terrestrial particles delivered by the Mackenzie River into the Beaufort Sea (Canadian Arctic Ocean) over the last 10 years." Biogeosciences 12, no. 11 (June 9, 2015): 3551–65. http://dx.doi.org/10.5194/bg-12-3551-2015.
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Abstract. Global warming has a significant impact on the regional scale on the Arctic Ocean and surrounding coastal zones (i.e., Alaska, Canada, Greenland, Norway and Russia). The recent increase in air temperature has resulted in increased precipitation along the drainage basins of Arctic rivers. It has also directly impacted land and seawater temperatures with the consequence of melting permafrost and sea ice. An increase in freshwater discharge by main Arctic rivers has been clearly identified in time series of field observations. The freshwater discharge of the Mackenzie River has increased by 25% since 2003. This may have increased the mobilization and transport of various dissolved and particulate substances, including organic carbon, as well as their export to the ocean. The release from land to the ocean of such organic material, which has been sequestered in a frozen state since the Last Glacial Maximum, may significantly impact the Arctic Ocean carbon cycle as well as marine ecosystems. In this study we use 11 years of ocean color satellite data and field observations collected in 2009 to estimate the mass of terrestrial suspended solids and particulate organic carbon delivered by the Mackenzie River into the Beaufort Sea (Arctic Ocean). Our results show that during the summer period, the concentration of suspended solids at the river mouth, in the delta zone and in the river plume has increased by 46, 71 and 33%, respectively, since 2003. Combined with the variations observed in the freshwater discharge, this corresponds to a more than 50% increase in the particulate (terrestrial suspended particles and organic carbon) export from the Mackenzie River into the Beaufort Sea.
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Doxaran, D., E. Devred, and M. Babin. "A 50% increase in the amount of terrestrial particles delivered by the Mackenzie River into the Beaufort Sea (Canadian Arctic Ocean) over the last 10 years." Biogeosciences Discussions 12, no. 1 (January 7, 2015): 305–44. http://dx.doi.org/10.5194/bgd-12-305-2015.
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Abstract. Global warming has a significant impact at the regional scale on the Arctic Ocean and surrounding coastal zones (i.e., Alaska, Canada, Greenland, Norway and Russia). The recent increase in air temperature has resulted in increased precipitations along the drainage basins of Arctic Rivers. It has also directly impacted land and seawater temperatures with the consequence of melting the permafrost and sea-ice. An increase in freshwater discharge by main Arctic rivers has been clearly identified in time series of field observations. The freshwater discharge of the Mackenzie River has increased by 25% since 2003. This may have increased the mobilization and transport of various dissolved and particulate substances, including organic carbon, as well as their export to the ocean. The release from land to the ocean of such organic material, which was sequestered as frozen since the last glacial maximum, may significantly impact the Arctic Ocean carbon cycle as well as marine ecosystems. In this study we use 11 years of ocean-colour satellite data and field observations collected in 2009 to estimate the amount of terrestrial suspended solids and particulate organic carbon delivered by the Mackenzie River into the Beaufort Sea (Arctic Ocean). Our results show that during the summer period the concentration of suspended solids at the river mouth, in the delta zone and in the river plume has increased by 46, 71 and 33%, respectively, since 2003. Combined with the variations observed in the freshwater discharge, this corresponds to a more than 50% increase in the particulate (terrestrial suspended particles and organic carbon) export from the Mackenzie River into the Beaufort Sea.
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Bieniek, Peter A., Uma S. Bhatt, Donald A. Walker, Martha K. Raynolds, Josefino C. Comiso, Howard E. Epstein, Jorge E. Pinzon, et al. "Climate Drivers Linked to Changing Seasonality of Alaska Coastal Tundra Vegetation Productivity." Earth Interactions 19, no. 19 (December 1, 2015): 1–29. http://dx.doi.org/10.1175/ei-d-15-0013.1.
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Abstract The mechanisms driving trends and variability of the normalized difference vegetation index (NDVI) for tundra in Alaska along the Beaufort, east Chukchi, and east Bering Seas for 1982–2013 are evaluated in the context of remote sensing, reanalysis, and meteorological station data as well as regional modeling. Over the entire season the tundra vegetation continues to green; however, biweekly NDVI has declined during the early part of the growing season in all of the Alaskan tundra domains. These springtime declines coincide with increased snow depth in spring documented in northern Alaska. The tundra region generally has warmed over the summer but intraseasonal analysis shows a decline in midsummer land surface temperatures. The midsummer cooling is consistent with recent large-scale circulation changes characterized by lower sea level pressures, which favor increased cloud cover. In northern Alaska, the sea-breeze circulation is strengthened with an increase in atmospheric moisture/cloudiness inland when the land surface is warmed in a regional model, suggesting the potential for increased vegetation to feedback onto the atmospheric circulation that could reduce midsummer temperatures. This study shows that both large- and local-scale climate drivers likely play a role in the observed seasonality of NDVI trends.
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Macklin, Mark G., and John Lewin. "River stresses in anthropogenic times: Large-scale global patterns and extended environmental timelines." Progress in Physical Geography: Earth and Environment 43, no. 1 (October 10, 2018): 3–23. http://dx.doi.org/10.1177/0309133318803013.
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Global perspectives on the complexities of environmental change impacts associated with past and present human activity are needed for the food and water security challenges of the twenty-first century. This is especially true for rivers, for which the onset and persistence of a range in human activities, altering their function and form, have been temporally and spatially variable. Ancient civilisations, states and empires extended geographically to cover sub-continental areas where their river modifying activities became linked to regional Earth system stresses arising from climate and land use change. We present a new interpretative framework for characterising and classifying human impact on river systems, emphasising that this has taken place over decadal to millennial time periods on a sub-continental scale. This 16-element classification and documentation of different human transformations, including land management, urbanisation, industry and engineering activities, is used to explore anthropogenic channel and floodplain disruptions that have followed each other in different sequences in different places. It is significant that these inadvertent and deliberate human interventions have also taken place in parallel with contrasting climatic fluctuations that have been sub-continental in scale and varied in time. We assess the influence of the dominant modes of regional climate variability (monsoons, El Niño Southern Oscillation, Indian Ocean Dipole, North Atlantic Oscillation, Pacific Decadal Oscillation and Siberian High) on the speed and pattern of river system adjustment to anthropogenic perturbations. Some river civilisations have proved resilient to change given their adaptive management, while others have been overwhelmed by climate-related changes in river morphodynamics. We conclude that integrated socioeconomic, climatic and hydromorphological histories provide usefully instructive antecedents for sensibly managing, as they evolve, the even more serious coupled environmental stresses likely in the future.
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Guo, Yaohua, Puyang Zhang, Hongyan Ding, and Conghuan Le. "Experimental Study on Torsion Resistance of Foundation Ring Land-Based Wind Power Expanded Foundation Scale Model." Applied Sciences 10, no. 16 (August 13, 2020): 5612. http://dx.doi.org/10.3390/app10165612.
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In this paper, an experimental torsion resistance-loading system for wind power extended foundation scale models is taken as the research object, and four 1:3 scale model specimens of the foundation ring are tested. The transmission mechanism of torque load in the extended foundation was analyzed, and the proportion of each part bearing the torque load was calculated. Test results showed that when the torque load was small, the torque load transmitted from the upper part was mainly borne by the sidewall adhesion force, as well as the top radial reinforcement. In contrast, the torque load was gradually borne by the anchor flange of the foundation ring in the case of a large torque load. At the middle and late stages of torque loading, the top radial reinforcement of the foundation shared about 20% of the torque load, while the bottom flange of the foundation ring shared about 80%. The torque load is most sensitive to changes in the size of the bottom flange but not sensitive to those in the embedded depth of the foundation ring or in the strength of the foundation concrete.
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Pratama, Isnu Putra, Haryo Winarso, Delik Hudalah, and Ibnu Syabri. "Extended Urbanization through Capital Centralization: Contract Farming in Palm Oil-Based Agroindustrialization." Sustainability 13, no. 18 (September 8, 2021): 10044. http://dx.doi.org/10.3390/su131810044.
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The discussion on extended urbanization considers accumulation by dispossession as a key apparatus for instilling urban logic into predominantly rural areas. This paper contends that extended urbanization can also be produced without physical dispossession of community land. This is illustrated by the case study of Sei Mangkei, an emerging palm oil agroindustrial district in North Sumatra, Indonesia. Capitalist industries prefer monetization through contract farming rather than privatization as an instrument to capture the productivity of palm oil smallholder land. The people who serve as smallholders in the palm oil industry are not victims of land appropriation. Moreover, this situation was also triggered by an opportunity for maximizing the socio-economic welfare of smallholders. However, the limited options to access other economic activities when the commodity crisis occurred was a consequence that smallholders were not aware of in the past. Thus, we assert that extended urbanization was (re)produced through the articulation of socio-economic and cultural practices of smallholders on a local-scale with regard to the dynamics of the broader process of global industrialization.
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Daskalova, Gergana N., Isla H. Myers-Smith, Anne D. Bjorkman, Shane A. Blowes, Sarah R. Supp, Anne E. Magurran, and Maria Dornelas. "Landscape-scale forest loss as a catalyst of population and biodiversity change." Science 368, no. 6497 (June 18, 2020): 1341–47. http://dx.doi.org/10.1126/science.aba1289.
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Global biodiversity assessments have highlighted land-use change as a key driver of biodiversity change. However, there is little empirical evidence of how habitat transformations such as forest loss and gain are reshaping biodiversity over time. We quantified how change in forest cover has influenced temporal shifts in populations and ecological assemblages from 6090 globally distributed time series across six taxonomic groups. We found that local-scale increases and decreases in abundance, species richness, and temporal species replacement (turnover) were intensified by as much as 48% after forest loss. Temporal lags in population- and assemblage-level shifts after forest loss extended up to 50 years and increased with species’ generation time. Our findings that forest loss catalyzes population and biodiversity change emphasize the complex biotic consequences of land-use change.
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Tremblay, L.-B., and M. Hakakian. "Estimating the Sea Ice Compressive Strength from Satellite-Derived Sea Ice Drift and NCEP Reanalysis Data*." Journal of Physical Oceanography 36, no. 11 (November 1, 2006): 2165–72. http://dx.doi.org/10.1175/jpo2954.1.
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Abstract Satellite-derived sea ice drift maps and sea level pressure from reanalysis data are used to infer upper and lower bounds on the large-scale compressive strength of Arctic sea ice. To this end, the two datasets are searched for special situations in which the wind forcing and its orientation with respect to the coastline allowed the authors to deduce a mean sea ice compressive strength from simple theory. Many estimates of ice compressive strength were possible for the winter of 1992/93 when the Arctic high was confined to the western Arctic and deep penetration of the Icelandic low produced wind patterns that pushed the ice perpendicular to the coastline in the Beaufort and East Siberian Seas. The winter of 1996/97, on the other hand, was characterized by a well-established Arctic high, producing wind patterns that generally pushed ice along coastlines rather than against them. Results show lower and upper bounds on the sea ice compressive strength parameter of 30 and 40 kN m−2, and 35 and 45 kN m−2, for the winters of 1992/93 and 1996/97, respectively (with a potential bias low of about 10 kN m−2). A tensile strength for sea ice of about 25 kN m−2 is also found in the East Siberian Sea in the first few hundred kilometers from the land, presumably associated with land-fast ice. The proposed mean ice compressive strength estimate is higher than those derived by minimizing the cumulative error between simulated and observed buoy drift trajectories. It is noted that the uncertainties in the estimates derived from models are large (with an unbiased estimate of standard deviation of 8.75 kN m−2). The estimates of yield strength in isotropic compression presented herein are in good agreement with a previous estimate made during the Arctic Ice Dynamic Joint Experiment, and with in situ ice compressive stress measurements made in the Beaufort Sea.
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Héquette, Arnaud, and Philip R. Hill. "Late Quaternary seismic stratigraphy of the inner shelf seaward of the Tuktoyaktuk Peninsula, Canadian Beaufort Sea." Canadian Journal of Earth Sciences 26, no. 10 (October 1, 1989): 1990–2002. http://dx.doi.org/10.1139/e89-168.
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This paper describes the seismic stratigraphy of the Quaternary sediments on the inner shelf (< 20 m water depth) of the Canadian Beaufort Sea, seaward of the Tuktoyaktuk Peninsula. Two regional unconformities and three seismic sequences are defined from the high-resolution seismic records. The deeper sequence (sequence III) is characterized by large-scale cross-beds. This sequence has been correlated with the Tingmiark Sand lithostratigraphic unit, which was previously defined farther offshore and is thought to be a glaciofluvial unit deposited during lower-than-present sea-level conditions in the Late Wisconsinan. The lower boundary of the overlying sequence (sequence II) is an unconformity (u/c 2), interpreted as the pre-transgression land surface. Sequence II is discontinuous and consists of localized basin-fill and channel-fill units. Most of these are remnants of thermokarst lakes partially eroded during the Holocene transgression. This sequence is separated from the uppermost sequence (sequence I) by another unconformity (u/c 1), which is the shoreface erosion surface generated by the Holocene sea-level rise. Sequence I is composed of a transgressive sand sheet overlain, in deeper areas, by recent marine muds. Seaward of Hutchison Bay, a large subbottom depression within sequence III in interpreted as a Late Wisconsinan fluviatile channel. According to our seismic interpretation, the Tuk Phase morainal and glaciofluvial deposits existing onland on the Tuktoyaktuk Peninsula, previously assigned to the Early Wisconsinan, would be of Late Wisconsinan age.
Dissertations / Theses on the topic "Extended land beaufort scale"
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Michener, John E. "Effects of Environmental Factors on Construction of Soil-Cement Pavement Layers." Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2630.pdf.
Full textBooks on the topic "Extended land beaufort scale"
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Purcell, Kate. Geographical Change and the Law of the Sea. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198743644.001.0001.
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This book examines the implications of geographical change for maritime jurisdiction under the law of the sea. In a multistranded intervention, it analyses and critiques both the explicit and implicit reasoning underpinning the familiar claim that maritime limits are, as a general rule, ambulatory—shifting with changes to the coast. The book examines and challenges related and analogous arguments regarding the implications of geographical change for maritime boundaries. It attempts to clarify the principles and presumptions bearing upon an assessment of the fluidity of boundaries generally. Finally, it considers and contests claims that entitlement to maritime space will be lost if the features generating such entitlement are submerged by rising seas. This analysis is extended in a comment on the implications of a loss of habitable land and large-scale population displacement for continuing territorial sovereignty and statehood. The in-depth analysis of the existing law in this book offers new answers to the question of the implications of geographical change for entitlement to maritime space, maritime limits, and international maritime boundaries. It also helps to clarify the circumstances in which either or both territorial sovereignty and statehood may be lost, explaining why the impacts of climate change upon land and population will not automatically have this result—even if the affected State is no longer ‘effective’ as a State or territorial sovereign. The book includes an analysis of the principle of intertemporal law that suggests a useful framework for considering questions of stability and change in international law more broadly.
Book chapters on the topic "Extended land beaufort scale"
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Jeffs, Andrew, Carly Daniels, and Kevin Heasman. "Aquaculture of Marine Lobsters." In Fisheries and Aquaculture, 286–312. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780190865627.003.0012.
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Marine lobsters include some of the most highly prized and valuable seafood species in the world. Accessible wild populations of edible lobster species are under increasing pressure from harvesting, habitat loss, disease, pollution and climate change. To provide an alternative supply, there have been extensive efforts to develop aquaculture methods for many species of marine lobsters, but with slow progress. A range of unfavorable biological attributes of marine lobsters has constrained their development for aquaculture, including complex life cycles, low fecundity, extended larval periods, slow growth, and cannibalism. A lack of knowledge of aspects of the fundamental biology of many species has also made it challenging to advance aquaculture techniques. Currently, the only extensive commercial aquaculture of marine lobsters occurs in Vietnam, with annual production of well over 1,000 t of spiny lobsters. This involves the wild capture and mariculture of early juveniles of several species of spiny lobsters in simple floating sea cages and feeding them on freshly caught marine life, mostly small coastal fish and benthic invertebrates. The success of this apparently simple technology indicates the opportunity for increased aquaculture production as soon as the recent advances in larval culture of spiny (Palinuridae) and slipper (Scyllaridae) lobsters can provide a large and sustainable source of juveniles. While viable larval culture methods for the American and European clawed lobsters (Homaridae) have been available for some time, more recent advances with compartmentalized land- and sea-based culture systems show promise in overcoming the cannibalistic behavior of these species, an essential step toward developing commercially viable aquaculture. The likely emergence of large-scale commercial aquaculture of marine lobsters in the next decade has the potential to provide an alternative supply of lobsters into global seafood markets, with the prospect of relieving fishing pressure on wild populations of marine lobsters.
Conference papers on the topic "Extended land beaufort scale"
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Paschereit, Christian Oliver, Peter Flohr, Hanspeter Kno¨pfel, Weiqun Geng, Christian Steinbach, Peter Stuber, Karin Bengtsson, and Ephraim Gutmark. "Combustion Control by Extended EV Burner Fuel Lance." In ASME Turbo Expo 2002: Power for Land, Sea, and Air. ASMEDC, 2002. http://dx.doi.org/10.1115/gt2002-30462.
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Flame stabilization in a swirl-stabilized combustor occurs in an aerodynamically generated recirculation region which is a result of vortex breakdown. The characteristics of the recirculating flow are dependent on the swirl number and on axial pressure gradients. Coupling to downstream pressure pulsations is also possible. In order to fix the position of the recirculation zone, an extended fuel lance was inserted into the burner. An additional benefit of the extended lance was to enable secondary fuel injection directly into the recirculation zone where the flame is stabilized. Tests were conducted with and without secondary fuel injection. The measurements included optimization of the location of the extended lance in the mixing chamber and variation of the amount of secondary fuel injection at different equivalence ratios and output powers. Flow visualizations showed that stabilization of the recirculation zone was achieved. The effect of the extended lance on pressure and heat release oscillations and on emissions of NOx, UHC and CO was investigated. The results were confirmed in high pressure single burner pressure tests and in a full scale land-based test gas-turbine. The lance has been successfully implemented in engines with sufficient stability margins and good operational flexibility. This paper shows the careful development process from lab scale tests to full scale engine tests until the implementation into the field engines.
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Stuttaford, Peter, Hany Rizkalla, Yan Chen, Brian Copley, and Thomas Faucett. "Extended Turndown, Fuel Flexible Gas Turbine Combustion System." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-22585.
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Flexibility is key to the future success of gas turbines for power generation. As renewable energy becomes more widely used the need for reliable, flexible standby power generation will increase. Gas turbines which are able to operate efficiently and in emissions compliance from extended low load to base load will have a significant advantage in meeting this need. Fuel costs and availability are of increasing concern. A gas turbine which is able to flexibly operate with a wide range of fuels, without the need for a diluent such as water or nitrogen, will provide added value to the operators of these machines. Carbon emissions are also of growing environmental concern, and the abatement of such emissions is likely to become of increasing monetary value. A fuel flexible combustor able to operate flexibly on both decarbonized fuel and natural gas will be well positioned to take commercial advantage of the situation. A combustion system is described and demonstrated which meets the goals set forth above. The system is simply retrofittable into existing E/F-class frame machines. The combustor is comprised of a dry lean premixed system without the need for diluents to control emissions. The operating principle of the new combustor is described. A full scale rig test program was undertaken to validate the new design and these results are presented. Results are shown with low emissions operation at 15–25% engine load. Combustor performance with a range of fuel blends up to 60% hydrogen, all with emissions below 9ppm of NOx and CO, is presented.
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Alizadeh, Sohail, and Barrie Moss. "Modelling Sub-Grid Scale Features in Congested Engine Ventilation Zones." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90461.
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In the increasingly congested accessory zones of gas turbine engine casings, it is important that the several temperature-sensitive components, like the electronic engine control unit (EEC), are bathed in an appropriate ventilation environment. Additionally it must be ensured that heat sources, like the geometrically complex gear box components, furthest from the inflows do not sit in stagnant zones. In this paper CFD methods have been used to study in detail the ventilation and heat transfer environment of one particular zone — that of the fan casing in the engine nacelle of a high by-pass turbofan. A particular challenge was the appropriate modelling of the extensive pipe systems that existed in this environment, ensuring that their impact on the flow field and heat transfer was suitably taken into account. Whilst in past practice large components and ducts have been modelled in CFD studies, the small scale pipe systems and electrical harnesses do not lend themselves easily to explicit modelling strategies. In this work a methodology is presented whereby the effects of all small scale pipe systems within the zone are represented using a sub-grid modelling approach. The momentum drag and heat release associated with all small scale pipes have been modelled and their impact on the ventilation and heat transfer characteristics of the accessory zone environment assessed. Comparisons made with the explicit methodology, not employing sub-grid models, have revealed that the small scale pipe systems have a significant impact on the flow and heat distribution, particularly around the EEC. Finally, limited comparisons with similar test rig flow visualisation data have been made, confirming the overall flow pattern within the zone. The work also suggests approaches in which the sub-grid methodology may be extended and verified for engine design purposes.
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Greenberg, Steven J., Neil K. McDougald, and Leonel O. Arellano. "Full-Scale Demonstration of Surface-Stabilized Fuel Injectors for Sub-Three ppm NOx Emissions." In ASME Turbo Expo 2004: Power for Land, Sea, and Air. ASMEDC, 2004. http://dx.doi.org/10.1115/gt2004-53629.
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ALZETA Corporation has developed surface-stabilized fuel injectors for use with lean premixed combustors which provide extended turndown and ultra-low NOx emission performance. These injectors use a patented technique to form interacting high-flow and low-flow flame zones immediately above a selectively-perforated porous metal surface. This allows stable operation at low reaction temperatures. This technology has been given the product name nanoSTAR™. Previous work involved the development of nanoSTAR technology from the proof-of-concept stage to prototype testing. Rig testing of single injectors and of two injectors simulating a sector of an annular combustion liner have been completed for pressure ratios up to 17 and combustion air inlet temperatures up to 700 K (800°F). This paper presents results from the first ever full-scale demonstration of surface-stabilized fuel injectors. An annular combustion liner, fitted with twelve nanoSTAR injectors was successfully tested up to a pressure ratio of 12 and combustion air inlet temperature of 700 K (800°F). NOx emissions were 2 ppm with CO emissions of 3 ppm both corrected to 15% O2. The combustion system exhibited excellent temperature uniformity around the annular combustor outlet with a maximum pattern factor of 0.16 and engine-appropriate radial profiles.
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Bolwell, Richard. "Through Life Management of Naval Gas Turbines for Extended Service Lives and Reduced Lifetime Costs." In ASME Turbo Expo 2002: Power for Land, Sea, and Air. ASMEDC, 2002. http://dx.doi.org/10.1115/gt2002-30269.
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Marine gas turbines have been used for many decades in a diverse range of commercial and naval marine vessels, almost exclusively for main propulsion duties in a number of different configurations. As well as providing an outline of the scope of operation, this paper aims to discuss the key Life Extension Program’s and Cost Reduction Strategies developed by the UK Ministry of Defence in support of the two international collaborative Memoranda of Understanding (MoU) for the marine Olympus, Tyne and Spey gas turbines. Where available, discussion is supported with evidence from emerging equipment maintenance policies, equipment modifications and data collected from components and engines returned from the fleet for repair or overhaul. In addition, and in terms of the economy of scale advantages that the arrangements offer, an assessment of accumulated savings and projected financial return is provided with an insight into the operational benefits and improved capability that the program’s realise.
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Hah, Chunill, Jo¨rg Bergner, and Heinz-Peter Schiffer. "Short Length-Scale Rotating Stall Inception in a Transonic Axial Compressor: Criteria and Mechanisms." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90045.
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The current paper reports on investigations aimed at advancing the understanding of the flow mechanism that leads to the onset of short-length scale rotating stall in a transonic axial compressor. Experimental data show large oscillation of the tip clearance vortex as the rotor operates near the stall condition. Inception of spike-type rotating stall is also measured in the current transonic compressor with high response pressure transducers. Computational studies of a single passage and the full annulus were carried out to identify flow mechanisms behind the spike-type stall inception in the current transonic compressor rotor. Steady and unsteady single passage flow simulations were performed, first to get insight into the interaction between the tip clearance vortex and the passage shock. The conventional Reynolds-averaged Navier-Stokes method with a standard turbulence closure scheme does not accurately reproduce tip clearance vortex oscillation and the measured unsteady pressure field. Consequently, a Large Eddy Simulation (LES) was carried out to capture more relevant physics in the computational simulation of the rotating stall inception. The unsteady random behavior of the tip clearance vortex and it’s interaction with the passage shock seem to be critical ingredients in the development of spike-type rotating stall in a transonic compressor. The Large Eddy Simulation was further extended to the full annulus to identify flow mechanisms behind the measured spike-type rotating stall inception. The current study shows that the spike-type rotating stall develops after the passage shock is fully detached from the blade passages. Interaction between the tip clearance vortex and the passage shock creates a low momentum area near the pressure side of the blade. As the mass flow rate decreases, this low momentum area moves further upstream and reversed tip clearance flow is initiated at the trailing edge plane. Eventually, the low momentum area near the pressure side reaches the leading edge and forward spillage of the tip clearance flow occurs. The flows in the affected blade passage or passages then stall. As the stalled blade passages are formed behind the passage shock, the stalled area rotates counter to the blade rotation just like the classical Emmon’s type rotating stall. Both the measurements and the computations show that the rotating stall cell covers one to two blade passage lengths and rotates at roughly 50% of the rotor speed.
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Yokoyama, Ryohei. "Optimal Configuration Design of Gas Turbine Cogeneration Plants by a MILP Decomposition Approach." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27565.
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To attain the highest economic and energy saving characteristics of gas turbine cogeneration plants, it is necessary to rationally determine capacities and numbers of gas turbines and auxiliary equipment in consideration of their operational strategies corresponding to seasonal and hourly variations in energy demands. Some optimization approaches based on the mixed-integer linear programming (MILP) have been proposed to such configuration design problems of energy supply plants. However, with increases in the numbers of the equipment which must be considered as candidates as well as the periods which must be set for variations in energy demands, the optimal configuration design problems become too large-scale and complex to solve. The author has proposed a MILP decomposition approach to obtain quasi-optimal solutions of the optimal configuration design problems in reasonable computation times. However, this approach has been limited to the optimal configuration design problems where equipment capacities are treated continuously. In this paper, the MILP decomposition approach is extended to the optimal configuration design problems where equipment capacities are treated discretely. The effectiveness of this extended approach is investigated through a numerical study on a gas turbine cogeneration plant.
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Speth, Raymond L., H. Murat Altay, and Ahmed F. Ghoniem. "Dynamics and Stability Limits of Syngas Combustion in a Backward-Facing Step Combustor." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-28130.
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The stability bands and combustion dynamics of syngas under different operating conditions and fuel compositions are investigated. Pressure measurements and high-speed video data are used to distinguish three operating modes. A stable region near the lean flammability limit is characterized by the shedding of small-scale vortices in the shear-layer. A quasistable region is present at intermediate equivalence ratios. At high equivalence ratios, we observe an unstable operating mode characterized by the periodic interaction between a large vortex and the flame. As the amount of hydrogen in the fuel is increased, the lean flammability limit is extended and transitions between operating regimes moves to lower equivalence ratios. Numerical simulations performed using a vortex method correspond to the experimental measurements and confirm the observed instability mechanism.
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Straatman, A. G., N. C. Gallego, Q. Yu, and B. E. Thompson. "Characterization of Porous Carbon Foam as a Material for Compact Recuperators." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90598.
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Experiments are presented to quantify the convective heat transfer and the hydrodynamic loss that is obtained by forcing water through blocks of porous carbon foam (PCF) heated from one side. The experiments were conducted in a small-scale water tunnel instrumented to measure the pressure drop and the temperature rise of the water passing through the blocks and the base temperature and heat flux into the foam block. In comparison to similar porosity aluminum foam, the present results indicate that the pressure drop across the porous carbon foam is higher due to the large hydrodynamic loss associated with the cell windows connecting the pores, but the heat transfer performance suggests that there may be a significant advantage to using PCF over aluminum foam for extended surface convection elements in recuperators and electronic cooling devices.
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Canepa, Edward, Pasquale Di Martino, Piergiorgio Formosa, Marina Ubaldi, and Pietro Zunino. "Unsteady Aerodynamics of an Aero-Engine Double Swirler LPP Burner." In ASME Turbo Expo 2004: Power for Land, Sea, and Air. ASMEDC, 2004. http://dx.doi.org/10.1115/gt2004-54212.
Full textAbstract:
Lean premixing prevaporizing burners represent a promising solution for low-emission combustion in aeroengines. Since lean premixed combustion suffers from pressure and heat release fluctuations that can be triggered by unsteady large-scale flow structures, a deep knowledge of flow structures formation mechanisms in complex swirling flows is a necessary step in suppressing combustion instabilities. The present paper describes a detailed investigation of the unsteady aerodynamics of a large scale model of a double swirler aero-engine LPP burner at isothermal conditions. A 3-D laser Doppler velocimeter and an ensemble averaging technique have been employed to obtain a detailed time-resolved description of the periodically perturbed flow field at the mixing duct exit and associated Reynolds stress and vorticity distributions. Results show a swirling annular jet with an extended region of reverse flow near to the axis. The flow is dominated by a strong periodic perturbation which occurs in all the three components of velocity. Radial velocity fluctuations cause important periodic displacement of the jet and the inner separated region in the meridional plane. The flow, as expected, is highly turbulent. The periodic stress components have the same order of magnitude of the Reynolds stress components. As a consequence the flow mixing process is highly enhanced. While turbulence acts on a large spectrum of fluctuation frequencies, the large scale motion influences the whole flow field in an ordered way that can be dangerous for stability in reactive conditions.