bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Influence of Mach Number on the Boundary Layer Development of High-Lift Low Pressure Turbine in Low Reynolds Number
Authors: Duan Wenhua , Liu Jian , Qiao Weiyang 
Published: January 2021

Abstract
A numerical analysis of the effect of Mach number on the boundary layer development and aerodynamic performance of a high-lift, after loaded low pressure turbine blade is presented in this paper. The turbine blade is designed for the GTF engine and works in a low Reynolds number, high Mach number environment. Three different isentropic exit Mach numbers (0.14, 0.87 and 1.17) are simulated by large eddy simulation method, while the Reynolds number based on the axial chord length of the blade and the exit flow velocity is kept the same (1 × 105). The condition Mais,2 = 0.14 represents the lowspeeed wind tunnel environment which is usually used in the low pressure turbine investigation. The condition Mais,2 = 0.87 represents the design point of the turbine blade. The condition Mais,2 = 1.17 represents the severe environment when the shock wave shows up. A comparison of the boundary layer development is made and the total pressure loss results from the boundary layer is discussed.
Morphology and Dynamics of a Premixed Hydrogen-Methane-Air Jet Flame in Hot Vitiated Turbulent Crossflow
Authors: Solana-Pérez R. , Miniero L. , Shcherbanev S. , Bothien M. , Noiray N. 
Published: January 2021

Abstract
The effect of hydrogen enrichment of a premixed hydrogen-methane-air jet in hot vitiated crossflow was studied at atmospheric condition. The hot turbulent vitiated crossflow is generated by a symmetric array of 4 × 4 jet flames burning a lean mixture of natural gas and air in fully premixed condition at equivalence ratio φcf = 0.7 and total thermal power of 50 kW. This crossflow is then used to ignite the premixed perpendicular jet of hydrogen-methane-air at ambient temperature. Three jet parameters are varied to study the effect of hydrogen addition on the flame morphology and stabilization mechanism: the hydrogen mass fraction of the H2/CH4 fuel blend (ξ = 0 – 100%), the jet equivalence ratio (φ = 0.8 – 2.0) and the jet-to-crossflow momentum ratio (J = 3 – 12). High-speed hydroxyl (OH) chemiluminescence is used to obtain the time-resolved imaging of the reactive jet and to compute its time averaged morphology. OH planar laser induced fluorescence (OH-PLIF) is used to acquire OH concentration fields at the jet center plane. The jet morphology is analyzed by considering its mean trajectory, extracted from the experimental data and fitted with empirical correlations available from the literature. New correlations are proposed for the flame length, width and center of gravity as function of the hydrogen content. It is shown that with increasing hydrogen fraction, the flame is shortened and more compact, and it stabilizes close to the jet root. Another finding of this work is the reattachment of the flame at the base of the windward jet shear layer when hydrogen fraction is increased. Robust flame anchoring is observed for H2 mass fractions of the CH4/H2 fuel blend that exceed 50%. Moreover, it is shown using instantaneous OH-PLIF images that for these conditions of increasing hydrogen concentration, the windward shear layer features larger-scale coherent structures that govern the aerodynamics of the reactive premixed jet in turbulent vitiated crossflow.
Comparison of Two Methods for the Sensitivity Analysis of a One-Dimensional Cooling Flow Network of a High-Pressure-Turbine Blade
Authors: Fiedler Barbara , Muller Yannick , Voigt Matthias , Mailach Ronald 
Published: January 2021

Abstract
Efficient cooling of the thermally extremely loaded high-pressure-turbine blades and vanes is required to ensure acceptable service life. The development of cooling systems is a high-dimensional problem, since it includes multiple design parameters. The integration of stochastic methods into the design phase contributes to a better understanding of the complex interaction between the design parameters and the system behavior and thus helps designing more efficient cooling systems. Therefore, the present study compares two stochastic methods, the Elementary-Effect method by Morris and the Coefficient-of-Importance, for the quantification of the sensitivity of the cooling flow to geometric variations using a 1D flow network of a high-pressure-turbine blade. As test case a multipass cooling system with rib-roughened walls is investigated. To achieve geometrically meaningful variations a new parametrization, called Harmonic-Spline-Deformation, is developed and first time presented in the paper at hand. The parametrization proves to be universally applicable to the components of a cooling system and facilitates the interpretation of the physical relationships between variables and resulting system behavior. For a sufficiently large population size, both methods show good agreement in quantifying the importance of design parameters regarding their effect on the cooling flow. The Coefficient-of-Importance, however, proves to be more stable against a decreasing population size and more robust against defects in the population.
Research on Prediction of NOx Emission Performance of Marine Gas Turbine Under Variable Operating Conditions
Authors: Li Jian , Wang Zhitao , Li Tielei , Li Shuying 
Published: January 2021

Abstract
With the global warming, many countries pay more attention to environmental pollution. The NOx emissions has become an important index when gas turbine designed. This paper provides a method for predicting NOx emissions of marine gas turbine under variable operating conditions. Firstly build the 3-D model of combustor. The characteristic regions of combustor were divided according to the reaction principle. Then build the chemical reactor network (CRN) models of different characteristic regions. According to the NOx emissions of several specific operating points simulated by computational fluid dynamics (CFD), fit the relation between residence time and operating conditions by Newton interpolation in the CRN models. Then the prediction model of NOx emissions of gas turbine was established by using neural network. The NOx emissions under 0.7∼1.0 working conditions and 0.019∼0.023 fuel-air ratios can be predicted efficiently.
An Exploration of a New Type of Guide Vanes for Thermoacoustic Bi-Directional Turbine
Authors: Liu Dongdong , Chen Yanyan , Dai Wei , Luo Ercang 
Published: January 2021

Abstract
As a new method of acoustic-to-electric conversion, bidirectional impulse turbine shows great potential for the development of economic and large scale thermoacoustic generators. In this paper, experimental and numerical studies on conventional bi-directional turbine with fixed guide vanes are investigated. A test rig for turbine operating in acoustic oscillating flow has been built. The fundamental output characteristics of the turbine are analyzed in oscillating flow. The maximum turbine efficiency is 38% (with 4000 rpm rotating speed, 853 W output shaft power and 1 flow coefficient). Additionally, enlightened by the bi-directional turbine with self-pitching guide vanes, a new structure of turbine is proposed. The guide vanes of the turbine are divided into two layers: the upper guide vanes and the lower guide vanes. When the turbine blade was rotating, the main flow is expected to flow through the lower guide vanes at the blade inlet and upper guide vanes at the blade outlet. So fluid energy loss could be reduced and efficiency could be improved. Compared with the bi-directional turbine with self-pitching guide vanes, the new structure shows in paper is simpler and more reliable. Different upper guide vanes angles and inclined angles of the nose cone are studied under steady flow. The results show that the maximum efficiency obtained is 31%, which is still lower than that of the conventional turbine. This means the fluid loss in the turbine may not be effectively reduced after the structure change and more optimizations need to be carried out for higher efficiency.
Electrified Aircraft Propulsion Systems: Gas Turbine Control Considerations for the Mitigation of Potential Failure Modes and Hazards
Authors: Simon Donald L. , Connolly Joseph W. 
Published: January 2021

Abstract
This paper provides a high-level review of the potential failure modes and hazards to which electrified aircraft propulsion (EAP) systems are susceptible, along with potential gas turbine control-based strategies to assist in the mitigation of those failures. To introduce the types of failures that an EAP system may experience, a generic EAP system is considered, consisting of gas turbine engines, mechanical drives, electric machines, power electronics and distribution systems, energy storage devices, and motor driven propulsors. The functionality provided by each of these EAP subsystems is discussed, along with their potential failure modes, and possible strategies for mitigating those failures. To further illustrate the role of gas turbine controls in mitigating EAP failure modes, an example based on a simulated EAP concept aircraft proposed by NASA is given. The effects of failures are discussed, along with turbomachinery control strategies, including reversionary control modes, and control limit logic.
Assessment of Surface Roughness Effects on Micro Axial Turbines
Authors: Gamil Abdelaziz A. A. , Nikolaidis Theoklis , Teixeira Joao A. , Madani S. H. , Izadi Ali 
Published: January 2021

Abstract
Surface roughness significantly affects the aerodynamics and heat transfer within micro-scale turbine stages. It results in a considerable increment in the blade profile loss and leads consequently to sizeable performance reductions. The provision of low roughness surfaces in micro gas turbine stages presents challenges on account of the small (mm scale) sizes, manufacturing complexity and associated costs. The axial turbine investigated in this study is fitted to Samad Power’s TwinGen domestic micro combined heat and power unit. The micro gas turbine has a compressor pressure ratio of 3, 1200K turbine inlet temperature and a rotational speed of 170,000 rpm. This paper presents a numerical assessment of the effects of varying the surface roughness on the performance and heat transfer of the micro turbine. The surface roughness was uniformly distributed on the NGV and rotor blades. The results showed that increasing the surface roughness from 3 microns to 6, 20, and 100 microns resulted in a reduction in stage total efficiency of 0.8%, 4% and 12% respectively as well as a comparable decrease in output power (0.7%, 3.6%, and 11% respectively). The turbine temperature was also observed to be very sensitive to surface roughness and a temperature increase of some 5% at the rotor hub and over 4% increment in the blade tip surface was observed for 100 microns when compared to the 3 microns surface roughness case. The findings of this paper highlight the adverse effects of the surface roughness on the micro-turbine performance and temperature distribution as well as the importance of careful consideration of wall roughness during the design and manufacturing stages.
Estimating Toughness for LF and DC Welded ERW Seams
Authors: Kiefner John , Rosenfeld Michael , Veloo Peter , Rovella Troy 
Published: January 2021

Abstract
ERW pipe materials, particularly those manufactured prior to 1970, have exhibited higher rates of failures from seam manufacturing defects than other types of pipe materials. Typically, the seam bond line regions of low-frequency (LF) and direct-current (DC) welded ERW pipe materials exhibit poor resistance to manufacturing defects. The toughness of the bond line region is difficult to determine, and it is likely to vary from one piece of pipe to another.
Pipeline operators must address the risk of ERW seam failures as part of their integrity management plans, but it is unlikely that they will know the toughness levels in the seams of their pipelines comprised of such materials. To avoid having to know the toughness levels in the seams, a pipeline operator can utilize a hydrostatic test to verify the integrity of a vintage ERW pipeline, but there are disadvantages the main one being that the pipeline must be taken out of service. Most likely an operator will choose to use an ILI crack tool to locate ERW seam anomalies to avoid having to take the pipeline out of service. Even if the seam defects can be located, correctly sized, and classified, however, the operator may have no idea of the effective toughness that is the key to deciding whether or not a given crack has to be excavated and repaired.
Presented herein are two options for improving the effectiveness of an ILI integrity assessment of a pipeline with low toughness ERW seams.
• Option 1 involves assuming a conservative level of toughness. Some such levels are available in the publicly available documents. Data from a large database of ERW seam failures are used to show the effectiveness of a fixed level of toughness at identifying critical defects while minimizing unnecessary digs.
• Option 2 consists of first: back-calculating the toughness levels associated with the known crack sizes and failure pressures of the defects in the database of ERW seam failures, and second: calculating the probability that each type of defect would have been correctly identified at a particular level of confidence using a particular level of toughness.
Using either of these options, a pipeline operator can improve the effectiveness of an ILI-crack-tool integrity assessment of a pipeline comprised of LF or DC welded ERW seams by reducing the number of unnecessary excavations while still being able to find the critical defects with an acceptable level of confidence.
Assessing Soil Corrosivity for Buried Structural Steel
Authors: Beauregard Yannick , Mah Andrea 
Published: January 2021

Abstract
Corrosion of steel structures in soils has been a topic of industrial research for many decades. The research has shown that the corrosivity of a soil is highly variable and a function of numerous interconnected parameters including soil resistivity, moisture content and pH. Despite the complexity of the soil environment, methods to evaluate soil corrosivity, guidelines for corrosion control during the design phase and lifetime of a structure have been developed. By applying this understanding, an opportunity exists to optimize the corrosion protection and capital expenses for new projects associated with corrosion protection of buried structural steel components. For instance, for new projects, e.g., identifying regions of low corrosivity where coatings are not required could lead to cost savings without compromising the integrity of the structure. However, within the industry, there is no universally accepted method to guide such decisions.
This paper is intended to address this issue by presenting a literature review and a case study on the topic. The literature review identifies the factors that influence the corrosion of buried steel structures, the range of corrosion rates observed on buried steel structures and quantitative and qualitative methods for assessing soil corrosivity. In the desktop case study, industry standards identified during the literature review (AASHTO R27-01, DIN50929-3:2018, ANSI/AWWA C105/A21.5 and Eurocode 3-5) are applied to applied to evaluate the soil corrosivity at three meter station sites in Alberta. The results are compared and recommendations for implementation are discussed. DIN 50929-3 stands out among the standards as it provides conservative estimates based on the most comprehensive data set and unlike the other standards, it assesses soil corrosivity both qualitatively and quantitatively.
Repair and Reinforcement of Blunt Defects on Pipeline Bends Using Composite Materials
Authors: Hill Paul , Swankie Troy , Bood Robert , Mihsein Dina 
Published: January 2021

Abstract
Previous research on the use of composite repair systems has focused on the repair of damage to straight sections. This paper reports verification testing completed on composite repairs for pipeline bends to support development of a safe and consistent approach that ensures an equal level of performance is maintained over the entire system.
A series of finite element analyses were completed that considered the effects of bend size (diameter and wall thickness), material grade, bend radius and angle. From this work 90° , 1.5D, 12” NB, X52 bends were selected for test. The objective was to demonstrate restoration of the fatigue life of the pipe to acceptable levels rather than just considering burst pressure. Defects equal to 0.5 times the diameter axially and 0.25 times the diameter radially were machined into the intrados of the bend (the location of highest hoop stress). Wall losses of 20% and 80% were replicated. Bounding repair thicknesses were tested to confirm performance was predictable.
Aggressive cyclic pressure ranges of 125Nmm−2 and 90mm−2 were applied to the repaired defects, with the lower stress range loaded for a larger number of cycles. A successful test was defined as one which exceeded the target number of cycles by a factor of 10 AND for which there was no visual sign of repair degradation. The number of load cycles was selected to ensure the repaired lines satisfied the slope of the S-N curve for pristine pipe, confirming the approach maintained the required margin of safety applicable to the rest of the system.
A design method is proposed that addresses weaknesses in the methods given in ISO 24817 and ASME PCC-2 Article 401. It is proposed that this be adopted by the standards for repairs to high pressure gas transmission pipelines to ensure equality of performance with undamaged sections.
Effects of Niobium on Microstructure and Hardness of Base Plate and Coarse Grained HAZ of High Strength X70 Grade UOE Linepipe Steel
Authors: Kizu Taro , Sakai Ryutaro , Imoto Hiroshi , Endo Shigeru , Barbaro Frank 
Published: January 2021

Abstract
The present study systematically evaluated base plates and Coarse Grained Heat Affected Zone (CGHAZ) properties of linepipe steels by using the controlled addition of increasing levels of niobium in a low carbon steel for comparison with other alloying combinations of Mn, Ni, Mo and V using laboratory melts and processed under simulated production conditions. The effects of niobium and other alloying elements on the mechanical properties and microstructural development, have been quantified with the intention of maintaining constant CGHAZ hardness in order that specific compositional effects can be directly compared. Characteristics of martensite and austenite (M-A) constituents in terms of size, shape and chemical composition has also been assessed.
It is demonstrated that niobium additions up to 0.1 mass% in a low carbon steel design provide opportunities to improve pipeline mechanical properties, service performance and safety. For the CGHAZ, austenite grain size was limited as the niobium content increased. Weld HAZ microstructures were relatively similar with little influence of niobium content on MA character, although the hardness was noted to increase with increasing niobium content, which would be beneficial to ensure adequate resistance to weld zone softening.
Bainite and small volume fractions of MA (nearly equal 2%) was a characteristic feature of CGHAZ of the materials having constant CGHAZ hardness, irrespective of chemical compositions examined. Other MA characteristics, such as size and cementite fraction, were also very similar among the steels.
Does Open Cut Pipeline Installation Affect the Geomorphology of Rivers?
Authors: Smith Sheldon , Enes Shannon , Metcalfe Jackie , Guthrie Rick , Dubeau Chuck 
Published: January 2021

Abstract
Open cut has traditionally been the preferred method of pipeline installation traversing watercourses. It is well understood and accepted that open cut excavation of the channel bed and banks during construction causes temporary disturbance to watercourse and aquatic habitat. Horizontal directional drilling, direct push and other subsurface installation methods can potentially avoid channel bed and bank disturbance but may have unique environmental effects such as frac-outs of drilling fluid. Although highly dependent on site conditions, open cut crossings are generally less costly than comparable subsurface installation methods.
When a pipeline is installed in an open cut, the pipe is typically installed on a gravel or sand bed, laid in place, surrounded by a sand pack and surrounding soils placed back in the cut in a manner that attempts to replicate the soil lithology, horizons and native compaction of the cut. It has long been thought that this sediment and soil disturbance and backfilling has the potential create a zone of geomorphological weakness at the cut where soil and sediment become dissimilar to the surrounding channel bed and banks and can result in the acceleration of bed scour, bank erosion, widening and slope instability. In this paper we examine the longer-term effects of open cut pipeline installations on the geomorphic characteristics of watercourses.
Over the course of four years of field investigation, nearly 750 pipeline watercrossings throughout Ontario were visited and assessed for geomorphic stability and depth of cover. The fluvial geomorphology of Ontario is diverse and ranging from alluvial, sinuous, unconfined, low gradient watercourses in the southwest to karst-influenced morphologies in eastern Ontario and often greater slope, confined and bedrock dominated watercourses in the north. By examining the field-based geomorphological characteristics of pipeline watercourse crossings in Ontario installed by open cut and crossing a wide range of fluvial geomorphological types we will explore and draw empirically-based conclusions on whether open cuts do in fact affect the long term geomorphological conditions of the watercourse.
Leak Rate Testing of a Natural Pipeline Defect
Authors: Andrews Robert M. , Short Joe 
Published: January 2021

Abstract
If a stable through wall defect (leak) were to occur in a pipeline, the leak rate is an important factor for both safety and environmental assessments, and also to determine the performance requirements for a leak detection system. For a “large” leak, an assessment can be based on simple idealization as an orifice, but for narrow crack like defects this is not appropriate. The flow through a crack is dependent on factors such as the surface roughness and the crack opening. These issues have been extensively studied for nuclear pipework where the fluid is either pressurized water, steam or CO2, and guidance is given in Annex F of BS 7910. However, there is little published work for pipeline geometries and single phase liquids such as refined hydrocarbons.
This paper presents the results of experiments measuring the leak rates through a tight axial through wall crack in a NPS 8 refined products pipeline. Leak rate measurements were made using water (for safety reasons) over a range of pressures. The data were fitted to a model for leakage through a tight crack that takes account of interaction of asperities in surface roughness. The fitted equation was then adjusted to take account of the different density and viscosity of the pipeline products. It was concluded that the model was able to give a good prediction of the measured leak rates and that the adjustments for the product properties were small.