Academic literature on the topic 'Line loading margin'
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Journal articles on the topic "Line loading margin"
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A N, Venkateswarlu, Tulasi Ram, S. S, and Sangameswara Raju.P. "Alleviation of VAr Impact on Critical Loading Margin with Redispatch in Deregulated Power Systems." International Journal of Engineering & Technology 7, no. 1.8 (2018): 130. http://dx.doi.org/10.14419/ijet.v7i1.8.11534.
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The stability management under deregulated environment has become typical task to the system due to random nature of load pattern and generation schedules. In addition, the regular uncertainties in system operation like line outage, generator outage or change in loading level are also causing to change in stability as well as security margins significantly. In order to manage transmission system security, the system operator can go for redispatch as a short term solution. In this article, an attempt is made to clear reactive power loading (VAr) impact on voltage instability margin or Critical Loading Margin (CLM). An Interior Point –Optimal Power Flow (IP-OPF) is applied to make system secured under (N-1) line contingencies. Using this secured schedule, the CLM is computed using Continuous Power Flow (CPF) for the two operating scenarios i.e., without VAr and with VAr loading on the system. The case study is simulated on IEEE 14-bus test network and outcome is validating that, the redispatch can also be apt for CLM enhancement even under contingencies as short term solution for stability management in real time.
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Haghighat, Hossein. "Loading margin calculation with line switching: A decomposition method." International Journal of Electrical Power & Energy Systems 64 (January 2015): 104–11. http://dx.doi.org/10.1016/j.ijepes.2014.07.019.
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Sun, Yu, and Xiu Li Wang. "Extreme Weather Loading Risk Model of Overhead Transmission Line." Advanced Materials Research 383-390 (November 2011): 2005–11. http://dx.doi.org/10.4028/www.scientific.net/amr.383-390.2005.
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Power grid suffers tremendous economic loss in extreme ice disaster weather, suggesting that it lacks immediate precautionary system. On the basis of the standards of Q/GDW179-2008 and IEC60826-2003, the curve of transmission line design loads is built up. In view of ransom character for load-strength of transmission line, according to load-strength interference theory, a short-term wind and ice loading risk model is established, which is a time-dependent wind and ice loading model, and can be calculated unreliability probability and fault rate, showing risks about cluster fault and common fault. Furthermore, wind and ice loads are divided into five states, which show risk margin of loads. It also can provide precautionary information for operator, and can present risk measurement on time scale.
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Ikeli, Ndubuisi Hyginus, Chinemezu Ashigwuike Evans, and Ibitoye Alabi Isaac. "Comparative Study and Performance Analysis of PSO, ABC, BFO and Cuckoo Search Optimization Techniques on UPFC Device for Voltage Stability Margin Improvement." International Journal of Innovative Science and Research Technology 7, no. 6 (2022): 1371–89. https://doi.org/10.5281/zenodo.6856386.
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This paper investigates the enhancement of voltage stability margin using UPFCdevice tuned with PSO, ABC, BFO and Cuckoo Search techniqueson Nigerian 330KV 56-bus practical network. In order to have avoltage stable power system it is goodto keep voltages within the acceptable limits. This is achieved using continuation power flow embedded in Power System Analysis Toolbox (PSAT).The optimal location and tuning of the UPFC device is determined using line stability index and the met – heuristics techniques. The effects of UPFC on voltage stability margin are examined. The results so obtained for tuning PSO, ABC, BFO and Cuckoo Search with UPFC device are compared to know the technique that yields the best loading parameter for Nigerian 56- bus power system for voltage stability margin enhancement. It is found thatUPFC tuned with Cuckoo Search outperforms the other techniques in terms of the increased loading parameter of the Nigerian power system which gives room for voltage stability margin improvement.The tuned UPFC device has provedbeyond reasonable doubt that it can improve voltagestability margin of the entire Nigerian 330KV Network.
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B, Vivekanadam. "Analysis of Voltage Stability Index under Stressed Operating Conditions in Bus Power Systems." December 2020 2, no. 4 (2021): 146–50. http://dx.doi.org/10.36548/jeea.2020.4.001.
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In stressed operating conditions, several types of voltage stability indices (VSI) are used for the assessment of voltage stability at specific operating points. The performance of various available VSIs are compared in this paper. The one generation unit tripped effects, single line to ground (SLG) fault and inductive loading variations occur in combinational format with such operating conditions. Voltage collapse occurs in the lines or nodes due to the stressed operating conditions (SOC). SLG fault, loading effects, power margin, line continency ranking, and line number are some of the performance parameters of VSI analysed in this paper. For utilization of reactive power compensation, the proper location can be chosen with the help of critical line and node analysis (CLNA) that makes use of VSIs. For any SOC, accurate voltage instability prediction is performed using VSI as per the simulation results. Under voltage collapse due to multiple causes, the voltage stability assessment of any specific line can be performed using this information.
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Kushwaha, Pawan Kumar, and Chayan Bhattacharjee. "A Research on Selection of Appropriate Stability Index under Adverse System Conditions for the Assessment of Voltage Stability of an IEEE 14 Bus Power System." European Journal of Electrical Engineering 22, no. 6 (2020): 435–46. http://dx.doi.org/10.18280/ejee.220605.
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For voltage stability assessment at a given operating point, various types of voltage stability indices (VSIs) have been proposed in the literature. In this paper, the voltage stability assessment of an IEEE-14 bus system is done for performance comparison of different types of VSIs available, under certain critical and practical stressed operating conditions (SOCs). The performance comparison of various VSIs under the considered SOCs is not reported in the literature. Such SOCs include the combinational occurrence of – variation in inductive loading, single line to ground (SLG) fault and effect of one generation unit tripped. These SOCs are the prime cause of voltage collapse of any node/line. The results show the performance of various VSIs with respect to line number, contingency ranking of the line, power margin, effects of loading and SLG fault. These VSIs are also instrumental in critical line and node analysis (CLNA) which is useful in the choice of proper location for reactive power compensation required. The simulated results provide the best performing VSI for accurate prediction of voltage instability under any considered SOC. This information is essential for voltage stability assessment of a particular line under multiple causes of voltage collapse.
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Nikkhah, Saman, Arman Alahyari, Adib Allahham, and Khaled Alawasa. "Optimal Integration of Hybrid Energy Systems: A Security-Constrained Network Topology Reconfiguration." Energies 16, no. 6 (2023): 2780. http://dx.doi.org/10.3390/en16062780.
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The integration of distributed energy resources, such as wind farms (WFs) and energy storage systems (ESSs), into distribution networks can lower the economic cost of power generation. However, it is essential to consider operational constraints, including loading margin, which ensures the security line contingency. This study aims to develop a comprehensive hourly distribution network reconfiguration (HDNR) model to minimize the economic cost for the power generation company. The model considers the optimal allocation of WFs and ESSs in terms of capacity and location, as well as the hourly status of the distribution network switches, based on security constraints. The proposed model is applied to an IEEE 33-bus distribution test system, and the capacities and locations of WFs and ESSs are determined. The impacts of security constraints on the optimal capacities and locations of WFs and ESSs, and the hourly configuration of the distribution network, are analyzed based on two case studies. In Case Study I, the model is solved with HDNR conditions, while Case Study II is solved without these restrictions, for comparison purposes. The results show that the optimal allocation of WFs and ESSs is affected by security constraints when HDNR is considered and highlight the crucial role of security constraints under contingency conditions, such as line outages. In the test system, three WFs and two ESSs are optimally allocated, with changes in capacity and location as the loading margin varies.
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Araga, Idris A., and A. E. Airoboman. "Enhancement of voltage stability in an interconnected network using unified power flow controller." Journal of Advances in Science and Engineering 4, no. 1 (2021): 65–74. http://dx.doi.org/10.37121/jase.v4i1.141.
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In this paper, the optimal placement of Unified Power Flow Controllers (UPFC) in a large-scale transmission network in order to improve the loadability margin was considered. In other to achieve this aim, the Line Stability Factor (LQP) as a technique for the optimal location of UPFC in the IEEE 14-bus network and 56-bus Nigerian national grid was adopted. The power injection model for the UPFC was employed to secure improvements in the loading margin of the IEEE 14-bus network and 56-bus Nigerian national grid system. Continuation power flow was used to assess the effect of UPFC on the loadability margin. Steady-state simulations using Power System Analysis Toolbox (PSAT) on MATLAB was applied to determine the effectiveness of placing UPFC between bus 13 and bus 14 in the IEEE 14-bus network and between bus 44 (Ikot-Ekpene) and bus 56 (Odukpani) in the 56-bus Nigerian national grid system. The results showed that the loadability margin increased by 8.52 % after UPFC was optimally placed in the IEEE 14-bus network and increased by 195.5 % after UPFC was optimally placed in the 56-bus Nigerian national grid system. Thus, these enhance the voltage stability of both network and utilizing the network efficiently.
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Stoeva, Daniela, Galena Mateeva, Danimir Jevremovic, Ana Jevremović, Branka Trifkovic, and Dimitar Filtchev. "Mechanical Resistance of Implant-Supported Crowns with Abutments Exhibiting Different Margin Designs." Applied Sciences 15, no. 9 (2025): 5193. https://doi.org/10.3390/app15095193.
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Background: Modern dentistry demands accurate finish line designs for abutments. CAD/CAM systems enable the fabrication of thin prosthetic structures to fulfill this requirement. The aim of this study is to research the mechanical resistance of customized implant abutments with different types of marginal design in laboratory environment. The null hypothesis is there is no difference in fatigue loading and compression strength in custom implant abutments with chamfer or vertical marginal design. Methods: The study model includes 60 specimens of implant suprastructures, organized into four test groups, by the margin design and used material: Group A—suprastructures, made of monolithic zirconia implant crown and titanium custom abutment with vertical marginal design; Group B—suprastructures, monolithic lithium disilicate implant crown and titanium custom abutment with vertical marginal design; Group C—suprastructures, made of monolithic zirconia implant crown and titanium custom abutment with chamfer marginal design; and Group D—suprastructures, made of monolithic lithium disilicate implant crown and titanium custom abutment with chamfer marginal design. All samples were subjected to fatigue loading test in chewing Simulator CS-4 (SD-Mechatronik, Westerham, Germany) for 1250,000 cycles, at a frequency of 2 Hz. The specimens, which survived, was conducted to compressive strength test in universal testing machine Instron M 1185 (Instron, Norwood, MA, USA). Results: The results analysis highlighted Group A as the most resistant to compressive forces (4411 MPa). Group D was with lowest values (1864 MPa)—twice than Group A. Group B (3314 MPa) had lower results than Group A, but higher than Groups C (3130 MPa) and D. Conclusion: Compression strength significantly depends on the choice of marginal design of implant abutments. Vertical margin design has better performance, that chamfer one.
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Pan, Chin-Yun, Ting-Hsun Lan, Pao-Hsin Liu, and Wan-Ru Fu. "Comparison of Different Cervical Finish Lines of All-Ceramic Crowns on Primary Molars in Finite Element Analysis." Materials 13, no. 5 (2020): 1094. http://dx.doi.org/10.3390/ma13051094.
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This study aimed to conduct a stress analysis of four types of cervical finish lines in posterior all-ceramic crowns on the primary roots of molar teeth. Four different types of finish lines (shoulder 0.5 mm, feather-edged, chamfer 0.6 mm, and mini chamfer 0.4 mm) and two all-ceramic crown materials (zirconia and lithium disilicate) were used to construct eight finite element primary tooth models with full-coverage crowns. A load of 200 N was applied at two different loading angles (0° and 15°) so as to mimic children’s masticatory force and occlusal tendency. The maximum stress distribution from the three-dimensional finite element models was determined, and the main effect of each factor (loading type, material, and finish line types) was evaluated in terms of the stress values for all of the models. The results indicated that the loading type (90.25%) was the main factor influencing the maximum stress value of the primary root, and that the feather-edged margin showed the highest stress value (p = 0.002). In conclusion, shoulder and chamfer types of finish lines with a 0.4–0.6 mm thickness are recommended for deciduous tooth preparation, according to the biomechanical analysis.
Dissertations / Theses on the topic "Line loading margin"
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Kang, Han. "Forecasting congestion in transmission line and voltage stability with wind integration." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-08-3867.
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Due to growth of wind power, system operators are being challenged by the integration of large wind farms into their electrical power systems. Large scale wind farm integration has adverse effects on the power system due to its variable
characteristic. These effects include two main aspects: voltage
stability and active line flow. In this thesis, a novel techniques
to forecast active line flow and select pilot bus are introduced
with wind power integration.
First, this thesis introduces a methodology to forecast congestion in the transmission line with high wind penetration. Since most wind resources tend to be located far away form the load center, the active line flow is one of the most significant aspects when wind farm is connected to electrical grid. By providing the information about the line flow which can contribute to transmission line congestion, the system operators would be able to respond such as by requesting wind power or load reduction.
The second objective of this thesis is to select the weakest
bus, called pilot bus, among all load buses. System reliability,
especially voltage stability, can be adversely affected by wind
variability. In order to ensure reliable operation of power systems
with wind power integration, the index to select the pilot bus is
developed, and further prediction of voltage profile at the pilot
bus is fulfilled. The objective function to select the pilot bus
takes account of the N-1 contingency analysis, loading margin, and reactive power sensitivity. Through on the objective function, the pilot bus is representative of all load buses as well as controllable by reactive power regulation. Predicting the voltage profile at the pilot bus is also useful for system operators to
determine wind power output.<br>text
Book chapters on the topic "Line loading margin"
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Roldo, Liane, and Nenad Vulić. "Marine Propeller Shaft Dimensions: Proposal to Extend the IACS UR M68 Formula to Alloy Steels." In Progress in Marine Science and Technology. IOS Press, 2024. https://doi.org/10.3233/pmst240044.
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On modern ships, particularly small coastal tourist ships around 50 meters in length, ship owners often prefer stainless steel propeller shafts, lubricated by an emulsion of grease and seawater, with no aft sealing. The IACS unified requirement UR M68 prescribes the expression for evaluating shaft diameter based on service loading and tensile strength of the shaft material. However, it should be noted that the formula is only applicable to shafts made of carbon, carbon manganese, and alloyed steels. Stainless steel is excluded. The aim of the paper is to propose the extension of the UR M68 formula for propeller shaft dimensions to cover stainless steel shafts. The chosen dimensions are dependent upon the shaft line concept, especially the type of lubricant, material and predetermined shaft loading (torque or power at the relevant speed). These are currently the only available initial quantities for dimensioning the propeller shaft. Dimensioning propeller shafts, including stainless steel, is a crucial aspect in the development of marine propulsion shafting systems. The presented approach is based upon the fact that the expected failure mechanism of the shaft is fatigue due to cycling loading. Additionally, it highlights and implements the relationship between fatigue strength and the tensile strength of the shaft material.
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Xue, X., N. Z. Chen, and Y. C. Pu. "Effects of proof loading test on fatigue life of mooring chain links." In Trends in the Analysis and Design of Marine Structures. CRC Press, 2019. http://dx.doi.org/10.1201/9780429298875-22.
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Kim, S., K. Kim, J. Lee, C. Yu, and W. You. "An experimental study on fatigue crack propagation life of T-joint fillet specimen considering residual stress under storm loading." In Advances in Marine Structures. CRC Press, 2011. http://dx.doi.org/10.1201/b10771-59.
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Sturmer, Daniel M., Patricia H. Cashman, Simon R. Poulson, and James H. Trexler. "Evolution of the Pennsylvanian Ely–Bird Spring Basin: Insights from Carbon Isotope Stratigraphy." In Late Paleozoic and Early Mesozoic Tectonostratigraphy and Biostratigraphy of Western Pangea. SEPM (Society for Sedimentary Geology), 2022. http://dx.doi.org/10.2110/sepmsp.113.04.
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Analysis and correlation of strata in ancient basins are commonly difficult due to a lack of high-resolution age control. This study tackled this problem for the latest Mississippian to middle Pennsylvanian Ely–Bird Spring basin. Here, 1095 new carbon isotope analyses combined with existing biostratigraphy at six sections throughout the basin constrain changes in relative sediment accumulation rates in time and space. The Ely–Bird Spring basin contains dominantly shallow-water carbonates exposed in eastern and southern Nevada, western Utah, and southeastern California. It formed as part of the complex late Paleozoic southwestern Laurentian plate margin. However, the detailed evolution of the basin, and hence the tectonic driver(s) of deformation, is poorly understood. The combined isotopic and biostratigraphic data were correlated using the Match-2.3 dynamic programming algorithm. The correlations show a complex picture of sediment accumulation throughout the life of the Ely–Bird Spring basin. Initially, the most rapid sediment accumulation was in the eastern part of the basin. Throughout Morrowan time, the most rapid sediment accumulation migrated to the northwestern part of the basin, culminating in a peak of sediment accumulation in Atokan time. This peak records tectonic loading at the north or northwest margin of the basin. Basin sedimentation was interrupted by early Desmoinesian time in the north by formation of northwest-directed thrust faults, folds, uplift, and an associated unconformity. Deposition continued in the south with a correlative conformity and increased clastic input. The combination of isotopic and biostratigraphic data for correlation is therefore a valuable tool for elucidating temporal basin evolution and can be readily applied to tectonically complex carbonate basins worldwide.
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Huang, X. P. "Study on fatigue life prediction of details with a surface crack under spectrum loading." In Progress in the Analysis and Design of Marine Structures. CRC Press, 2017. http://dx.doi.org/10.1201/9781315157368-48.
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Ettensohn, Frank R., D. Clay Seckinger, David P. Moecher, and Cortland F. Eble. "Paleoenvironmental and tectonic implications of an Upper Devonian glaciogenic succession from east-central West Virginia, USA." In Field Excursions to the Appalachian Plateaus and the Valley and Ridge for GSA Connects 2023. Geological Society of America, 2023. http://dx.doi.org/10.1130/2023.0066(01).
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ABSTRACT Glaciogenic rocks are rare in the Appalachian area and occur only locally as parts of Upper Precambrian and Upper Devonian successions. This trip examines a relatively recent exposure of Upper Devonian glaciogenic diamictites and laminites along Corridor H (U.S. Highway 48) in east-central West Virginia, USA. The diamictites occur in the Rockwell Member of the Price Formation, in transition with the underlying redbeds of the Upper Devonian Hampshire Formation. Palynology indicates that all parts of the Rockwell Member exposed at the locality are present in the Retispora lepidophyta – Verrucosisporites nitidus (LN) Miospore Biozone and are, therefore, of Late Devonian, but not latest Devonian, age. This biozone occurrence indicates correlation with parts of the Oswayo Member of the Price Formation, the Finzel tongue of the Rockwell Formation, and with dropstone-bearing parts of the Cleveland Shale Member of the Ohio Shale in northeastern Kentucky. Much previous work supports a glaciogenic origin for the diamictites and associated sediments, which occur as parts of a shallow-marine incursion that ended the Hampshire/Catskill alluvial-plain/deltaic complex across much of the Central Appalachian area. The glaciogenic succession is part of nearshore, marginal-marine strata that accumulated in an embayment during the Cleveland-Oswayo-Finzel transgression, which represents a global eustatic sea-level rise and foreland subsidence related to Acadian/Neoacadian deformational loading in the adjacent orogen. Detrital-zircon-provenance data from the diamictites indicate Ordovician plutonic sources as well as reworked Neoproterozoic to Ordovician sedimentary sources that can only have been derived from nearby Inner Piedmont sources like the Potomac terrane. This provenance suggests that Acadian/Neoacadian convergence of the exotic Carolina terrane with the New York and Virginia promontories along the southeastern margin of Laurussia not only uplifted Inner Piedmont source areas into a high mountain range capable of supporting glaciation in a subtropical setting, but also, through deformational loading, enhanced regional subsidence and the incursion of shallow seas that allowed alpine glaciers access to the open sea.
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"Mitigating Impacts of Natural Hazards on Fishery Ecosystems." In Mitigating Impacts of Natural Hazards on Fishery Ecosystems, edited by Sarah G. McCarthy. American Fisheries Society, 2008. http://dx.doi.org/10.47886/9781934874011.ch2.
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<em>Abstract</em>.—Nonpoint source pollution in the form of stormwater runoff is one of the most important emerging threats to ecosystems along the coastal margins of the United States. A wide diversity of potentially toxic chemicals is commonly found in stormwater. These include the various pesticides, petroleum hydrocarbons, heavy metals, and other common contaminants that originate from commercial, industrial, residential, and agricultural land-use activities. These chemicals are mobilized from roads, lawns, crops, and other surfaces by rainfall and then transported to aquatic habitats via terrestrial runoff. The ongoing development of coastal watersheds nationwide is increasing the loading of nonpoint source pollutants to rivers, estuaries, and the nearshore marine environment. A central aim of the National Oceanic and Atmospheric Administration’s national Coastal Storms Program (CSP) is to enhance the resiliency of coastal ecosystems by improving the ability of coastal communities to anticipate and reduce the impacts of contaminated terrestrial runoff. Toxic chemicals in stormwater can adversely impact the health of fish, including threatened and endangered species. Nonpoint source pollution can also degrade the biological integrity of aquatic communities that support productive fish populations. This article examines the effects of stormwater runoff on fish and fisheries. Using case studies drawn from CSP project work in the Pacific Northwest and Southern California pilot regions, we show how degraded water quality can impact the health of fish during critical life history stages (i.e., spawning and rearing) as well as limit the overall effectiveness of fish habitat restoration. We also discuss some of the resources currently available to local communities to reduce the loading of toxics in stormwater, thereby increasing the resilience of aquatic communities. Finally, we identify priority areas for new research to help guide the future conservation and recovery of at-risk fish populations.
Conference papers on the topic "Line loading margin"
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Marchesani, Thomas J. "Evaluation of a Crude Oil Loading Berth for Maintenance Coating." In SSPC 2007. SSPC, 2007. https://doi.org/10.5006/s2007-00056.
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Abstract During FY2003, a feasibility study evaluated the condition of coatings on a crude oil loading berth, analyzed the ramifications of coating failure, and performed life cycle economic comparisons of maintenance coating alternatives. The subject paper presents a summary of the coating inspection results as well as an alternative method to determine the effect of coating failure and corrosion on marine loading berths.
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Zhang, Kathy, and James Ferguson. "Crack Shape Development in Fatigue Growth Assessment for Pipelines." In CORROSION 2017. NACE International, 2017. https://doi.org/10.5006/c2017-09402.
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Abstract Assessment of fatigue crack growth for pipelines is critical to evaluate the effects of operational pressures acting on flaws and predict the remaining service life. Under pressure cycling, cracks propagate continuously until they reach a critical size, resulting in a pipeline leak or rupture. When the crack grows, the crack shape and size evolve and it is important to characterize these changes to accurately predict fitness. Currently, it is typical to only consider growth in crack depth when modeling pressure cycling-induced fatigue. In some cases, neglecting the effects of crack shape or aspect ratio under crack growth may result in inaccurate predictions for remaining service life and ultimately a reduced margin of safety. Developing a full understanding of crack shape development during crack growth can be crucial for integrity management to more accurately estimate the remaining service life and prevent pipeline leaks or ruptures. In this work, crack aspect ratio change was studied for pipelines undergoing pressure cycling. The effects of initial crack aspect ratio, pipeline diameter and wall thickness, and loading conditions on the crack shape development were investigated. A new methodology for fatigue crack growth assessment is demonstrated. The study provides a refinement to fatigue crack growth assessment with the potential for more accurate prediction of remaining service life for pipelines.
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Okui, Hidetaka, Tom Verstraete, R. A. Van den Braembussche, and Zuheyr Alsalihi. "Three Dimensional Design and Optimization of a Transonic Rotor in Axial Flow Compressors." In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-45425.
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This paper presents a 3-D optimization of a moderately loaded transonic compressor rotor by means of a multi-objective optimization system. The latter makes use of a Differential Evolutionary Algorithm in combination with an Artificial Neural Network and a 3D Navier-Stokes solver. Operating it on a cluster of 30 processors enabled the optimization of a large design space composed of the tip camber line and spanwise distribution of sweep and chord length. Objectives were an increase of efficiency at unchanged stall margin by controlling the shock waves and off-design performance curve. First, tests on a single blade row allowed a better understanding of the impact of the different design parameters. Forward sweep with unchanged camber improved the peak efficiency by only 0.3% with a small increase of the stall margin. Backward sweep with an optimized S shaped camber line improved the efficiency by 0.6% with unchanged stall margin. It is explained how the camber line control could introduce the forward sweep effect and compensate the negative effects of the backward sweep. The best results (0.7% increase in efficiency and unchanged stall margin) have been obtained by a stage optimization that also considered the spanwise redistribution of the rotor flow and loading to reduce the Mach number at the stator hub.
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Farrell, Ronald S. "Some Practical Aspects of Class 1E Actuator Qualification on Comparing Test Levels and Design Basis Event Loading." In ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-63526.
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All power operated valve actuators that perform a critical safety function in nuclear power plants must be backed by testing to demonstrate they are capable of reliably performing their safety related function. Such actuators are denoted Class 1E and must be qualified according to IEEE-382 “Standard for Qualification of Actuators for Power-Operated Valve Assemblies with Safety-Related Functions for Nuclear Power Plants” which states that a Class 1E Actuator is essential to emergency reactor shutdown, containment isolation, reactor core cooling, and containment and reactor heat removal, or otherwise essential in preventing significant release of radioactive material to the environment. Qualification of these actuators involves type testing where one or several test specimens that adequately represent and span the entire represented fleet undergo rigorous testing commensurate with expected service. Then, for each application, an evaluation is performed to show how specific loading is enveloped with margin by the testing. IEEE-382 is a specific application of the more general IEEE-323 “Standard for Qualifying Class 1E Equipment for Nuclear Power Generation Stations” containing general requirements applicable to all Class 1E equipment; then, the rules of IEEE-323 add useful clarification to those of IEEE-382. This paper describes actual type testing of a gas-hydraulic actuator where planned levels were not reached at all times for every test due to test apparatus limitations and shows that the resulting intermittently off target test levels need not envelope loading for all times compared to specific applications. IEEE-382 requires an evaluation showing that test conditions meet specific service conditions plus acceptable margin; however, demonstrating that margin also exists in the range of achieved test levels demonstrates that specified service conditions are adequately included even though specified levels are not enveloped at every time or frequency due to the test apparatus limit anomalies. One practical example is given that logically compares the achieved seismic test levels with a sample required load case for a line mounted valve assembly. Another example compares results from a simulated design basis environmental accident event involving high temperature steam with a sample expected event curve. Rather than compare test and application level by level and curve by curve, the physical effect of the loading, such as stress level, is compared between the test specimen and the application. It is concluded that test levels need not envelope requirements at every point if it can be shown and documented that important physical aspects including stress level, deflection magnitude, absorbed vibration cycles, and energy involvement are enveloped with the required margin.
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Kiss, A., and Z. Spakovszky. "Effects of Transient Heat Transfer on Compressor Stability." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75413.
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The effects of heat transfer between the compressor structure and primary gas path flow on compressor stability are investigated during hot engine re-acceleration transients, or so called “Bodie” transients. A mean line analysis of an advanced, high-pressure ratio compressor is extended to include the effects of heat transfer on both stage matching and blade row flow angle deviation. A lumped capacitance model is used to compute the heat transfer of the compressor blades, hub, and casing to the primary gas path. The inputs to the compressor model with heat transfer are based on a combination of full engine data, compressor test rig measurements, and detailed heat transfer computations. Transient calculations with heat transfer show a 8.0 point reduction in stall margin from the adiabatic case, with heat transfer predominantly altering the transient stall line. 3.4 points of the total stall margin reduction are attributed to the effect of heat transfer on blade row deviation and the remainder is attributed to stage re-matching. It is found that heat transfer increases loading in the front stages and destabilizes the front block. Furthermore, the stage re-matching due to heat transfer alters the slope of the compressor characteristic and promotes modal-type stall inception. Sensitivity studies show a strong dependence of stall margin to heat transfer magnitude and flow angle deviation at low speed, due to the effects of compressibility. Computations for the same transient using current cycle models with bulk heat transfer effects, such as NPSS, only capture 1.2 points of the 8.0 point stall margin reduction. This implies that, using this new capability, opportunities exist early in the design process to address potential stability issues due to transient heat transfer.
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Patel, Ankit Bhai, K. Viswanath, and Dhyanjyoti Deb Nath. "Effect of Axial Sweep and Tip Extension on Performance of an Axial Fan." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-65967.
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Performance enhancement in terms of stall margin increment, increased pressure rise coefficient and increased efficiency is of great need for low speed axial fans. Stacking line modifications in terms of sweep, skew, dihedral or combination of these, as well as blade tip geometry modifications are assumed to be one of the ways to achieve finite performance improvement. Non radial stacking of blade profiles modifies secondary flows, tip vortex effects, hub passage vortex and thus affects aerodynamic performance parameters such as stall margin, efficiency, pressure rise, blade loading. In literature many studies have confined to comparison of few cases which led to conflicting results as modification of stacking line may have different effects in different cases. In the present work, comparison of performance of axial fan rotor with three different blade configurations BSL (baseline), SWP (swept blade) and EXTN (swept blade with extended tip) are considered. The BSL configuration is designed on basis of non-free vortex design. The SWP configuration is obtained by shifting radial stacking line of the BSL in axial flow direction by 10° (Forward sweep). The EXTN configuration is obtained by extending tip profile on pressure surface as well as suction surface by 3% locally. Experiments have been conducted on these three configurations to study effects of these modifications on aerodynamic performance. The flow field has been surveyed using Kiel probe, Three hole pressure probe at many flow rates starting from fully open to fully closed. Unsteady flow analysis at exit of rotors of all configurations is carried out using fast response pressure probe. Experimental results show slight performance improvement in terms of increased stall margin, efficiency, as well as total pressure rise for SWP rotor as well as EXTN rotor compared to BSL rotor at low flow coefficients.
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Hagesteijn, Gerco, Karola van der Meij, and Cornel Thill. "Distributed Propulsion: A Novel Concept for Inland Vessels." In ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/omae2015-41845.
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In the drive to reduce the fuel consumption of inland vessels, one of the main limitations, the risk of propeller ventilation was investigated. The aim was to reduce the resistance of the vessel, while at the same time an acceptable margin against propeller ventilation had to be assured. A typical inland vessel has up to two high loaded relative large propellers, with tip regions in the lighter loading condition above the water line. To eliminate the risk of propeller ventilation, these ships often have inbuilt shape features such as tunnels and skirts, only having the intention to avoid air being drawn by the rotating propeller. These devices however have a noticeable own resistance, imposing a mortgage to the ship’s total resistance. Current design practice for these devices is that as long as you cannot quantify a risk, take care of a sufficient safety margin. With the research done within the EU-funded STREAMLINE project new insights were gained into the prediction of air suction. As a result, the margin against ventilation could be reduced which resulted into a large reduction of the resistance of the vessel. Reducing the high loading of propellers means to gain efficiency with at the same time reducing the risk of propeller ventilation as the suction by the propeller(s) can be decreased as well. This leads to the idea of a “distributed thrust” concept (DTC). Within STREAMLINE DST developed a sample case for such a novel design with six thrusters, with the aim to reduce ventilation against zero and to achieve maximal performance improvements. The measurements were carried out in MARIN’s Depressurized Wave Basin (DWB). These tests were carried out with a 1:10 scale ship model, in sailing condition, and depressurized conditions. In this way, the correct representation of cavitation and possible ventilation bubbles and vortices is ensured, resulting in a correct physical behavior. At the same time synchronized high speed video recordings were made to acquire insight in the occurring phenomena. Within the project CFD calculations were carried out, aimed at characterizing the performance, loads, cavitation nuisance and ventilation risk in full-scale operating conditions. Validation of these calculations was done using the towing tank results.
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Nicak, Tomas, Richard Trewin, Elisabeth Keim, Ingo Cremer, Sebastien Blasset, and Heinz Hägeli. "Fracture-Mechanics Analysis of the Reactor Pressure Vessel Beznau 1 Based on Thermal-Hydraulics Input Data From KWU-MIX and CFD Analyses." In ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-63459.
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The integrity of a reactor pressure vessel (RPV) has to be ensured throughout its entire life in accordance with the applicable regulations. Typically an assessment of the RPV against brittle failure needs to be conducted by taking into account all possible loading cases. One of the most severe loading cases, which can potentially occur during the operating time, is the loss-of-coolant accident, where cold water is injected into the RPV nearly at operating conditions. High pressure in combination with a thermal shock of the ferritic pressure vessel wall caused by the injection of cold water leads to a considerable load at the belt-line area known as Pressurized Thermal Shock (PTS). Usually the assessment against brittle failure is based on a deterministic fracture-mechanics analysis, in which common parameters like J-integral or stress intensity factor are employed to calculate the load path for an assumed (postulated) flaw during the PTS event. The most important input data for the fracture-mechanics analysis is the transient thermal-hydraulics (TH) load of the RPV during the emergency cooling. Such data can be calculated by analytical fluid-mixing codes verified on experiments, such as KWU-MIX, or by numerical Computational Fluid Dynamics (CFD) tools after suitable validation. In KWU-MIX, which is the standard used for TH calculations within PTS analyses, rather conservative analytical models for the quantification of mixing and, depending on the water level, condensation processes in the downcomer (including simplified stripe and plume formations) are utilized. On the contrary, the numerical CFD tools can provide best-estimate results due to the possibility to consider more realistically the stripe and plume formations as well as the geometry of the RPV in detail. In order to quantify the safety margin inherent to the standard approach, two fracture-mechanics analyses of the RPV Beznau 1 based on thermal-hydraulic input data from KWU-MIX and CFD analyses were performed. Subsequently the resulting loading paths were compared between each other and with material properties obtained from the irradiation surveillance program of the RPV to demonstrate the exclusion of brittle-fracture initiation.
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Guinet, Cyril, J. Anton Streit, Hans-Peter Kau, and Volker Gümmer. "Tip Gap Variation on a Transonic Rotor in the Presence of Tip Blowing." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25042.
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High stability and efficiency are the main two objectives in the design of an axial-flow compressor. Stability usually reduces at higher stage loading, and the stability margin critically drops in transient operation and through the life cycle of an engine. A major reason for this to happen is the growing tip gap. A recirculating tip blowing casing treatment has shown the ability to enhance stability. To be able to use it as a stability control system at varying tip clearances in aircraft engines, the behavior of this casing treatment at different tip clearances was considered important and investigated in this paper. The present study investigates in depth the ability of a tip blowing casing treatment to postpone stall at three different tip clearances. The results prove a substantial beneficial effect for design and increased tip gaps and show some negative impact of the casing treatment for a small tip gap. The study is carried out on a 1.5 stage research compressor. The investigated rotor was already investigated with an axial-slot casing treatment for different tip gap heights at the Institute for Flight Propulsion. The design of a recirculating tip blowing casing treatment is simulated with an equivalent numerical setup. A tip blowing casing treatment consists of a bleed port connected to a tip blowing upstream of the rotor. The streamwise pressure gradient drives the tip blowing with a high injection velocity. A design speed line is simulated for three tip clearance values with and without the tip blowing casing treatment. The impact of the interaction between the tip blowing and the tip gap vortex is analyzed. A detailed analysis of the passage flow is conducted. A comparison of the stall margin is made. The study is carried out using URANS simulations.
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Kim, Hong-Won, Kook-Taek Oh, Sang-Hak Ghal, and Ji-Soo Ha. "Centrifugal Compressor Aerodynamic Design of Marine Engine Turbocharger by Three Dimensional Numerical Simulation." In ASME 2002 Joint U.S.-European Fluids Engineering Division Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/fedsm2002-31178.
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For the centrifugal compressor aerodynamic design of a turbocharger, first of all, the works for system matching to the engine specification must be preceded. Then, mean line design together with performance prediction should be carried out for preliminary design. In the mean line prediction, a slip factor is adopted as a function of flow coefficient and geometry instead of Wiesner’s equation, and it is found that the predicted result of slip magnitude is more accurate than that of conventional slip factor. Also, three-dimensional blade profile shape is generated on the basis of the preliminary design. The Navier-Stokes Equation solver with a turbulent model is used to find whether three-dimensionally designed geometry is reasonable by analyzing loading distribution of the blade. By investigating diffuser flow field of the simulated result, the diffuser inlet and exit angles were modified for the flow to move smoothly along the diffuser geometry. Modified performance prediction results shows better than those of original specification. Consequently, off design performance prediction results and numerical simulation result show good agreement with the experimental data. The modified design results show more increased compression ratio and efficiency than those of previous design results. The increased choke margin has made a stable operating range larger.
Reports on the topic "Line loading margin"
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Hadley, Isabel. PR164-205102-R01 Application of Probabilistic Fracture Mechanics to Engineering Critical Assessment. Pipeline Research Council International, Inc. (PRCI), 2021. http://dx.doi.org/10.55274/r0012093.
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This report summarizes the results of a series of deterministic and probabilistic fracture and fatigue calculations carried out in order to: ? Demonstrate that ProCW correctly implements probabilistic ECA, eg by comparing selected deterministic and probabilistic calculations, ? Show the effect of the choice of K-solution on the fatigue life and POF of pipes containing a circumferential flaw, ? Implement a two-stage probabilistic model of fatigue crack growth, in both air and marine environments, ? Consider the effects of modelling the fatigue crack growth threshold probabilistically, ? Demonstrate the use of ProCW for a representative riser geometry and a complex loading spectrum, ? For the same riser geometry/loading scenario, compare the POF implied by the use of design fatigue safety factors given in DNVGL-ST-F101 [2], DNVGL-RP-F204 [3] and DNVGL-RP-F201 [4] with the POF calculated directly from probabilistic calculations. There is a related webinar.