bluuebunny/crossref_metadata_2025 huggingface dataset:
Global health volunteering, the Ebola outbreak, and instrumental humanitarianisms in Sierra Leone
Authors: Herrick Clare , Brooks Andrew
Published: November 2019

Geographers have long been concerned with the spaces, scales, and conceptual significance of volunteering. They have, however, been slower to engage with the global surge in medical volunteering, whether in times of everyday or acute emergency. Volunteering is a crucial component of the architectures of global health and humanitarianism, but it remains marginal to the concerns of both health and development geographers. This paper seeks to address this lacuna through drawing on the case study of the 2013–2016 Ebola outbreak in Sierra Leone. When the outbreak was belatedly declared a Public Health Emergency of International Concern in 2014, volunteers flowed into Sierra Leone to aid in the response. In drawing on qualitative research with volunteers from a small, Freetown‐based NGO, we aim to close two explicit theoretical gaps. First, we draw out the geographical significance of volunteering during an outbreak of such exceptionality that the modalities, methods and architectures of global health and humanitarianism closed in on one another. Second, we explore how the act and experience of volunteering during the Ebola outbreak helped those involved apprehend what global health might mean and be. In so doing, we also reflect on the instrumental use of humanitarianism within a global health field whose professional contours are often remarkably difficult to navigate. In empirical terms, this intervention is rendered even more significant given the discipline's wider neglect of the Ebola outbreak as a crucial moment where the failures of global health were exposed and the toolkits of humanitarian intervention were pushed to their limits.
How renewable energy consumption lower global CO2 emissions? Evidence from countries with different income levels
Authors: Dong Kangyin , Dong Xiucheng , Jiang Qingzhe
Published: November 2019

Significant difference in the emission–renewables nexus across countries with different income levels is frequently ignored in previous studies. To empirically investigate whether the effect of renewable energy consumption on carbon dioxide (CO2) emissions differs across countries with different income levels, the emission–growth–renewables nexus for a global panel of 120 countries and four income‐based subpanels over the period 1995–2015 is examined. Fully considering the potential cross‐sectional dependence and slope heterogeneity, a series of econometric techniques allowing for cross‐sectional dependence and slope heterogeneity is utilised. Cross‐sectional dependence and slope heterogeneity are confirmed for the global panel as well as for all four subpanels. Only for the global panel, high‐income subpanel and upper‐middle‐income subpanel is the environmental Kuznets curve (EKC) hypothesis valid. Renewable energy consumption has a negative effect on CO2 emissions, but its effect is not significant; the mitigation effect may be obscured by higher economic growth and increasing non‐renewable energy consumption. The global panel and four subpanels provide mixed directionality of causality among the variables, suggesting that for various income‐based subpanels, significant differences exist in the effect of renewable energy consumption on CO2 emissions, especially highlighting in various direct and indirect influencing paths between renewable energy consumption and CO2 emissions.
Keeping the blood flowing
Authors: Eberhart Lars
Published: November 2019

The transfusion procedure is the last step in a multi‐process supply chain. The task of matching supply with demand requires donor managers to consider average consumption rates on a weekly or monthly basis, but to also have insight into variability in order distribution and possible attribute (blood groups) requirements. Since hospitals and blood banks are usually not deeply interwoven and often only ex‐post data are available, forecasting methods should be implemented. A thorough analysis of order pattern to set weekly target inventories and safety levels is required to close the information gap. A collection plan needs to identify possible bottlenecks which can be prevented through the planning of inter‐shipping, changes in message urgency and building of reserve donor pools. Constant analysis of collection and mobilization KPIs allows donor managers to implement the rolling‐wave planning approach and continually adapt to changing requirements, unexpected events and overall systematic variability. The variability happens on the demand side, as order quantities and their attributes, such as blood group distribution, are subject to change. However, also the supply is subject to significant variation, as donor response rates, attrition, deferrals and overall availability of donors are not constant. Unfavourable combinations of variable factors often lead to bottlenecks if only long‐term average values find their way into the planning process.
Serological and molecular typing in platelet alloantibody investigations
Authors: Ahlen Maria Therese
Published: November 2019

Alloimmunization against platelet antigens causes complications in transfusion settings as platelet transfusion refractoriness and post‐transfusion purpura, as well as in pregnancy, causing fetal/neonatal alloimmune thrombocytopenia. Strategies for the laboratory investigations depend on a repertoire of serological and molecular assays and are often dependent on timing and objective. Technical improvements have led to a number of sophisticated methods for alloantigen typing and alloantibody identifications during the last decade; however, some traditional methods are still beneficial. The laboratory investigations should ensure that the causative antibody specificities are identified as soon as possible to support the correct diagnosis and guide the selection of compatible platelets if needed.
Investigation of the Effect of Perforated Sheath on Thermal-Flow Characteristics Over a Gas Turbine Reverse-Flow Combustor—Part 2: Computational Analysis
Authors: Wang Liang , Wang Ting
Published: November 2019

The objective of Part 2 is to employ a computational scheme to investigate the difference in flow pattern, pressure drop, and heat transfer in a gas turbine’s dump diffuser and over the outer surface of the combustor with and without a sheath. Both experimental and computational studies are performed. In Part 1, the experiments were conducted under low pressure and temperature laboratory conditions to provide a database to validate the computational model, which was then used to simulate the thermal-flow field surrounding the combustor and transition piece under elevated gas turbine operating conditions. For laboratory conditions, the computational fluid dynamics (CFD) results show that (a) the predicted local static pressure values are higher than the experimental data but the prediction of the global total pressure losses matches the experimental data very well; (b) the total pressure losses are within 3% of the experimental values; and (c) the temperature difference between the sheathed and non-sheathed cases is in the range of 5–10 K or 16–32% based on the temperature scale between the highest and lowest temperatures in the computational domain. Under the elevated pressure and temperature conditions in real gas turbine, removing the sheath can achieve a significant pressure recovery of approximately 3% of the total pressure, but it will be subject to a wall temperature increase of about 500 K (900 °F or a 36% increase) on the outer radial part of the transition piece, where the flow is slow due to diffusion and recirculation in the large dump diffuser cavity near the turbine end. If modern advanced materials or coatings could sustain a wall temperature of about 500 K higher than those currently available, the sheath could be removed. Otherwise, removal of the sheath is not recommended.
An Expanding Cavity Model for Indentation Analysis of Shape Memory Alloys
Authors: Anuja J. , Narasimhan R. , Ramamurty U.
Published: November 2019

The mechanical and functional responses of shape memory alloys (SMAs), which are often used in small volume applications, can be evaluated using instrumented indentation tests. However, deciphering the indentation test results in SMAs can be complicated due to the combined effects of the non-uniform state of stress underneath the indenter and stress-induced phase transformation. To address this issue, an expanding cavity model (ECM) applicable to spherical indentation of SMAs is developed in this work based on an analytical solution for an internally pressurized hollow sphere. Analytical expressions for key indentation parameters such as the mean contact pressure and size of the transforming zone are obtained, whose validity is evaluated by recourse to finite element simulations and published experimental data for a Ni–Ti alloy. It is shown that the ECM predicts the above parameters reasonably well for indentation strains varying from 0.01 to 0.04. Also, a method is proposed to determine the critical stress required to initiate phase transformation under uniaxial compression based on the application of the ECM to interpret the indentation stress–strain response.
Automated Classification of Manufacturing Process Capability Utilizing Part Shape, Material, and Quality Attributes
Authors: Zhao Changxuan , Dinar Mahmoud , Melkote Shreyes N.
Published: November 2019

The ability to classify the capabilities of different manufacturing processes based on computer-aided design (CAD) models of parts is a key missing link in cybermanufacturing. In this paper, we present a one-step approach for automatically classifying the capabilities of three discrete manufacturing processes—milling, turning, and casting—based on part shape, quality, and material property attributes. Specifically, our approach utilizes machine learning to classify manufacturing process capabilities of these processes in terms of part shape attributes such as curvature, rotational symmetry, and pairwise surface point distance (D2) histogram computed from CAD models, as well as part quality (surface finish and size tolerance) and material property attributes of parts. In this manner, historical data can be utilized to classify the capabilities of manufacturing processes. We show that it is possible to achieve high classification accuracies—88% and 83% for the training and test data sets, respectively—using this approach. In addition, a key insight gained from this work is that part shape attributes alone are inadequate for discriminating between the capabilities of the manufacturing processes considered. Specifically, the inclusion of material property and part quality attributes enables the classifier to predict viable manufacturing processes that would otherwise be ignored using shape attributes alone. Future extensions of this work will include enriching the classification process with additional attributes such as production cost, as well as alternative classification methods.
Focus Variation Measurement and Prediction of Surface Texture Parameters Using Machine Learning in Laser Powder Bed Fusion
Authors: Özel Tuğrul , Altay Ayça , Kaftanoğlu Bilgin , Leach Richard , Senin Nicola , Donmez Alkan
Published: November 2019

The powder bed fusion-based additive manufacturing process uses a laser to melt and fuse powder metal material together and creates parts with intricate surface topography that are often influenced by laser path, layer-to-layer scanning strategies, and energy density. Surface topography investigations of as-built, nickel alloy (625) surfaces were performed by obtaining areal height maps using focus variation microscopy for samples produced at various energy density settings and two different scan strategies. Surface areal height maps and measured surface texture parameters revealed the highly irregular nature of surface topography created by laser powder bed fusion (LPBF). Effects of process parameters and energy density on the areal surface texture have been identified. Machine learning methods were applied to measured data to establish input and output relationships between process parameters and measured surface texture parameters with predictive capabilities. The advantages of utilizing such predictive models for process planning purposes are highlighted.
Reliability-Based Design Optimization of Complex Problems With Multiple Design Points via Narrowed Search Region
Authors: Wang Yutian , Hao Peng , Guo Zhendong , Liu Dachuan , Gao Qiang
Published: November 2019

The expensive computational cost is always a major concern for reliability-based design optimization (RBDO) of complex problems. The performance of RBDO can be lowered by the inaccuracy of reliability analysis (RA) which is caused by multiple local optimums and multiple design points in highly non-linear space. In order to reduce the computational burden and guarantee the accuracy of RA (and thus to improve the RBDO performance), a global RBDO algorithm by adopting an improved constraint boundary sampling (GRBDO-ICBS) method is proposed. Specifically, the GRBDO-ICBS method first narrows the concerned search region by using a Kriging-based global search. The accuracies of the design points are verified by the expected risk function (ERF), and the corresponding inaccurate design points are added into training samples to update Kriging. Then a multi-start gradient-based sequential RBDO is carried out, which tries to find out all multiple design points in the concerned search region. The performance of GRBDO-ICBS is demonstrated by four examples. All results have shown that the proposed method can achieve similar accuracy as Monte Carlo simulation (MCS)-based RBDO but with a much lower computational cost.
Calculating the Fold Angles of Any Vertex Roof Using a Spherical Image Technique
Authors: Eatough Daniel T. , Seffen Keith A.
Published: November 2019

The shape of a vertex roof is defined by the geometry of its constituent flat facets and the relative angle of folding across them. The spherical image of the roof, originally from Gauss, expresses these properties simultaneously. We present a method for calculating the image properties and thence the shape of any vertex roof based on subdividing the image into an array of suitable spherical triangles. In particular, we introduce a truss representation of the vertex for choosing viable subdivisions of the image, which allow full calculations to be made. Additionally, this allows us to construct generalized closed-form expressions for the fold angles of vertex roofs, presented here for roofs with up to six facets.
Wrench-Feasible Workspace of Mobile Cable-Driven Parallel Robots
Authors: Rasheed Tahir , Long Philip , Caro Stéphane
Published: November 2019

Cable-driven parallel robots (CDPRs) hold numerous advantages over conventional parallel robots in terms of high speed and large workspace. Cable-driven parallel robots whose workspace can be further increased by the modification of their geometric architecture are known as reconfigurable cable-driven parallel robots. A novel concept of reconfigurable cable-driven parallel robots that consists of a classical cable-driven parallel robot mounted on multiple mobile bases is known as mobile CDPR. This paper proposes a methodology to trace the wrench-feasible workspace of mobile cable-driven parallel robots by determining its available wrench set. Contrary to classical cable-driven parallel robots, we show that the available wrench set of a mobile cable-driven parallel robot depends, not only on the cable tension limits but also on the static equilibrium conditions of the mobile bases. The available wrench set is constructed by two different approaches known as convex hull approach and hyperplane shifting method. Three case studies are carried out for the validation of the proposed methodology. The proposed approach is experimentally validated on a mobile cable-driven parallel robot with a point-mass end-effector and two mobile bases.
Compressor Speed Decay During Emergency Shutdowns
Authors: Kurz Rainer , Garceau Sean , Ji Min , Brun Klaus
Published: November 2019

The emergency shutdown of a compressor train is a necessary safety feature. In this event, the power supply (either from a gas turbine or an electric motor) is cut off. The compressor train will continue to spin due to its inertia, but the speed will reduce fast. To avoid damage of the equipment during a shutdown event, compressor surge must to be avoided. In many instances, the dynamic behavior of the compression system is simulated to ensure that the necessary recycle valves are sized, and arranged properly. One of the key problems of dynamic simulation, and a major source of uncertainty in the results, is the correct treatment of the speed decay of the compressor train. The present study provides the background to evaluate the speed decay, and includes data from actual rundown situations. The evaluation shows general trends, that can be used to reduce the simulation uncertainties in dynamic simulations.
Aerodynamic Shape Optimization of a Turbine Blade Considering Geometric Uncertainty Using an Adjoint Method
Authors: Luo Jiaqi , Zheng Yao
Published: November 2019

Aerodynamic shape optimization of turbomachinery blades taking the performance impact of geometric uncertainty into account is presented in the paper. A continuous adjoint method for the steady-state Euler equations is used to calculate the first order (FO) sensitivities of performance functions to the design parameters. For each performance function, all the sensitivities can be obtained by about two equivalent flow computations, regardless of the number of design parameters. The performance changes due to the geometric variations are evaluated on use of the second order (SO) sensitivities. A direct-ad joint method is used to calculate the FO and SO sensitivities of performance functions to the basis modes of geometric variations, which are extracted from a covariance function using principal component analysis method. Firstly, the sensitivities of the mass-averaged adiabatic efficiency and mass flow rate to the basis modes of geometric variations for a three-dimensional turbine blade are calculated. The validations of sensitivity-based performance impact are then illustrated. For the optimization maximizing the adiabatic efficiency with mass flow rate constrained, a series of shape functions are imposed on the turbine blade to perturb the aerodynamic shape. For each deformed blade with respect to each design parameter, the statistic mean values of performance changes are evaluated by using the method of moment and then contribute to the calculation of the corresponding FO sensitivity of performance functions. The design optimization without and with geometric uncertainty are finally presented. The results are compared in detail to demonstrate the effects of geometric variations to the optimization, especially to the statistical performance of the optimized blades. Through design optimization, the shock loss can be significantly reduced, compared with the original blade. The optimized blade is more robust in respect of geometric uncertainty.
Gas Turbine Health State Prognostics by Means of Bayesian Hierarchical Models
Authors: Losi Enzo , Venturini Mauro , Manservigi Lucrezia
Published: November 2019

The prediction of the time evolution of gas turbine performance is an emerging requirement of modern prognostics and health management (PHM), aimed at improving system reliability and availability, while reducing life cycle costs.

In this work, a data-driven Bayesian Hierarchical Model (BHM) is employed to perform a probabilistic prediction of gas turbine future health state thanks to its capability to deal with fleet data from multiple units.

First, the theoretical background of the predictive methodology is outlined to highlight the inference mechanism and data processing for estimating BHM predicted outputs. Then, BHM is applied to both simulated and field data representative of gas turbine degradation to assess its prediction reliability and grasp some rules of thumb for minimizing BHM prediction error.

For the considered field data, the average values of the prediction errors were found to be lower than 1.0 % or 1.7 % for single- or multi-step prediction, respectively.
Property Risk Assessment for Liquefied Natural Gas Liquefaction Plants
Authors: Orme George J. , Venturini Mauro
Published: November 2019

Liquefied Natural Gas (LNG) liquefaction plants have become increasingly important as natural gas is exported from the United States of America to markets world-wide. Downtime of any part of the process train (gas turbine, compressors, controls, etc.) due to failure of one or more of its components can result in high costs. The total cost of loss is of great concern to the LNG industry as it moves towards increased LNG exports with required operational efficiency, and downtime reduced to a minimum.

This paper reports the application of a methodology of property risk assessment, providing insight into the use of PML (Probable Maximum Loss) and MFL (Maximum Foreseeable Loss) risk measures. Major sources of risk are analyzed, drawing from both technical literature and operational information on typical large LNG liquefaction plants.

The outcome of this paper is an estimation of the economic loss associated with property risk for two hypothetical LNG liquefaction plants, based upon sample plants located in North America and characterized by different capacity. These plants represent recently built and commissioned plants and are chosen to take advantage of current technology and plant capacities.
Wheel Box Test Aeromechanical Verification of New First Stage Bucket With Integrated Cover Plates for MS5002 GT
Authors: Mariottini Marco , Pieroni Nicola , Bertini Pietro , Pacifici Beniamino , Giorgetti Alessandro
Published: November 2019

In the oil and gas industry, manufacturers are continuously engaged in providing machines with improved performance, reliability and availability. First Stage Bucket is one of the most critical gas turbine components, bearing the brunt of very severe operating conditions in terms of high temperature and stresses; aeromechanic behavior is a key characteristic to be checked, to assure the absence of resonances that can lead to damage. Aim of this paper is to introduce a method for aeromechanical verification applied to the new First Stage Bucket for heavy duty MS5002 gas turbine with integrated cover plates. This target is achieved through a significantly cheaper and streamlined test (a rotating test bench facility, formally Wheel Box Test) in place of a full engine test. Scope of Wheel Box Test is the aeromechanical characterization for both Baseline and New bucket, in addition to the validation of the analytical models developed. Wheel Box Test is focused on the acquisition and visualization of dynamic data, simulating different forcing frequencies, and the measurement of natural frequencies, compared with the expected results. Moreover, a Finite Elements Model (FEM) tuning for frequency prediction is performed. Finally, the characterization of different types of dampers in terms of impact on frequencies and damping effect is carried out. Therefore, in line with response assessment and damping levels estimation, the most suitable damper is selected. The proposed approach could be extended for other machine models and for mechanical audits.
Multifidelity Based Optimization of Shaped Film Cooling Hole and Experimental Validation
Authors: Zhang Hao , Li Yifei , Chen Ziyu , Su Xinrong , Yuan Xin
Published: November 2019

It has been known that in previous optimization problems, surrogate models are widely used to improve the optimization efficiency. The optimization result depends heavily on the accuracy of surrogate model, while it also costs a lot to construct a high-accurate surrogate model. In order to obtain the optimal design of a shaped film cooling hole which is already well-designed, an optimization framework based on multi-fidelity model is proposed in this article. The characteristic of the multi-fidelity model in this work is that it combines the experimental design information and numerical simulation together. The optimization efficiency can be greatly improved by 64.5% with multi-fidelity model and furthermore the prediction accuracy is maintained with a high level. In this work, three geometry parameters are selected as design variables, which are lateral angle, laidback angle and hole length. A combined optimization method which includes GA (generic algorithm) and SQP (sequential quadratic programming) algorithm is used in the optimization process. A validation experiment is further conducted to validate the optimized hole design using PSP (pressure sensitive paint) and 3D printing technology. The optimization results have shown that the overall film cooling performance is 39% higher compared with baseline design. This work shows the merits of multi-fidelity model in high-efficiency optimization film cooling holes and it may provide further guide for other relative works.
Secondary Flow Measurements in a Compressor Cascade Using 3D LDA/PDA: Part B — Dispersed Phase Effects on Flow Topology
Authors: Harbeck Janneck , Geist Silvio , Joos Franz
Published: November 2019

The rapid regulation of gas turbine power plants is becoming increasingly important. In the field of stationary gas turbine power augmentation droplet-laden flows receive special attention as they cool the compressor’s inlet temperature. High fogging is an effective and economic method that secures power supply by reacting rapidly to fluctuating power generation. However, water droplets effect the aerodynamic performance of the compressor negatively. Therefore, the Laboratory of Turbomachinery investigated the interaction between droplets and blades at midspan by using diverse experimental methods to comprehend aerodynamic performance and water film induced losses. Additionally, the knowledge of the separation’s extent for three-dimensional flows with corner separation is of great importance as it leads to a blockage of the flow cross-section and therefore contributes to the losses. This paper enlarges this knowledge base by studying the interactions of the dispersed phase with the gas flow in three-dimensional flow structures as they are found in the near wall regions of every turbo compressor. By utilizing a three-dimensional Phase-Doppler Anemometer spatially resolved information on velocity mean vector, its higher moments as well as droplet diameters were extracted from the separated region for a compressor blade, in middle cross section design, with spray-injection. Streamlines that derive from the mean velocities visualize key features such as saddle and focal points. Then an integral approach is presented to evaluate the effect of the dispersed phase on the flow structure compared to dry flow and the impact back on different diameter classes. Finally, the velocity in streamwise direction shows the influence of the disperse phase on the aerodynamic blockage.
Using a New Entropy Loss Analysis to Assess the Accuracy of RANS Predictions of an HPT Vane
Authors: Zhao Yaomin , Sandberg Richard D.
Published: November 2019

Entropy loss is widely used to quantify the efficiency of components in turbomachines, and empirical relations have been developed to estimate the contribution of different mechanisms. However, further analysis is still needed to not only get a deeper insight of the physics, but also to more accurately quantify the loss generation caused by different terms. In the present study, the entropy transport equations based on averaged flow quantities are first derived, and the entropy generation process is fully decomposed into several terms representing different physical mechanisms, such as mean viscous dissipation, turbulence production, mean and turbulent heat flux, etc. This decomposition framework is then applied to high-resolution LES and RANS results of a VKI LS-89 HPT vane, and a detailed quantification of different entropy generation terms is obtained. The results show that the entropy generation caused by mean flow features like mean viscous dissipation and mean heat flux are in close agreement between LES and RANS, indicating that RANS provides an overall good prediction for the mean flow. Furthermore, we find that turbulence production plays an important role in entropy generation as it represents the energy extracted from the mean flow to turbulent fluctuations. However, the difference between RANS and LES results for the turbulence production term is not negligible, particularly in the wake region. This implies that the failure of RANS to predict the correct total loss might be largely caused by errors in capturing the correct turbulence production in the near wake region.
Power Augmentation Technologies for Gas Turbines: Alternatives for an Existing Simple Cycle Power Plant in Peru
Authors: Celis Cesar , Peralta Sergio , Galarza Walter
Published: November 2019

The influence of different power augmentation techniques used in gas turbines on the performance of simple cycle type power plants is assessed in this work. A computational model and tool realistically describing the performance of a typical simple cycle type power plant at design and off-design point conditions is initially developed. This tool is complemented with different models of power augmentation technologies. Finally, the whole model including both power plant and power augmentation techniques is used to analyze a case study involving a particular power plant in Peru. The results from the simulations of the specific power plant indicate that power output can be increased through all the evaluated power augmentation technologies. These results show indeed that technologies based on absorption refrigeration systems produce the largest gains in terms of power output (7.1%) and thermal efficiency (0.7%). Such results confirm the suitability of these systems for simple cycle type power plant configurations operating under hot and humid operating conditions as those accounted for here. From an economic perspective, considering the net present value as the key parameter defining the feasibility of a project in this category, power augmentation techniques based on absorption cooling systems result also the most suitable ones for the studied power plant. Power augmentation techniques environmental implications are also quantified in terms of CO2 emissions.
Numerical Study on Heat Transfer and Flow Characteristics in Double Turning Areas Ribbed Serpentine Channel With Lateral Outflow
Authors: Zhang Bo-lun , Zhu Hui-ren , Guo Tao , Yao Chun-yi , Fu Zhong-yi
Published: November 2019

The double turning areas ribbed serpentine channel with lateral outflow is an important structure for designing the internal systems of turbine blade. The current work similarly simplifies the internal channel of the real blade. The Nusselt number and pressure coefficient distribution of the double turning areas ribbed serpentine channel with different outflow ratios are numerically researched under static and rotating conditions. The Realizable k-ε turbulence model with enhanced wall treatment is used in the numerical simulation. The inlet Reynolds number is 11000. The rotation numbers vary from 0 to 0.09. Three outflow ratios are 27%/0%/73%, 27%/49%/24% and 27%/73%/0%, respectively. The rotation radius (R) is 46.4d. The result shows that the Nusselt number distribution of the passage 3 under 27%/49%/24% outflow ratio condition is similar to that under 27%/73%/0% outflow ratio condition. There is a large low Nusselt number area in the passage 3 under Dr = 27%/0%/73% condition. The averaged area Nusselt number ratios on the suction side of the passage 1, passage 2 and passage 3 are higher than that on the pressure side under nonrotating condition. Rotation enhances heat transfer on the suction side of the passage 2, and has a positive effect on pressure side heat transfer of passage 1 and passage 3. The averaged area Nusselt number ratio of passage 3 under 27%/73%/0% outflow ratio condition is higher than that under other outflow ratio conditions. With the rotation number increasing, the pressure coefficient of the complete ribbed serpentine channel gradually increases, and the maximum increase is in the first turning area.
Simulation of an Aero-Engine Bearing Compartment Using Two-Way Transition Between Lagrangian Droplets and a Three-Dimensional Eulerian Liquid Film
Authors: Dick Jean-Sebastien , Kumar Vivek , Nakod Pravin , Montanari Federico
Published: November 2019

This paper presents a new hybrid two-phase flow numerical model. It uses the Discrete Phase Model (DPM) and the Volume of Fluid model (VoF) to study the interaction between air, oil droplets and films in a bearing compartment. It allows transition from a trackable Lagrangian particle, such as a droplet, into a continuous liquid structure in a Eulerian frame of reference. The transition can also be performed in the opposite direction, where a continuous liquid structure can be converted back into a trackable particle if specific requirements are met. The method is designated as DPM-VoF-DPM throughout this paper.

Test cases capturing the impingement of a droplet in a liquid film are performed to assess its effectiveness. The simulation of a simplified bearing compartment is compared with measurements and results obtained using a standard VoF modeling approach. Mechanisms which are usually modeled such as droplet splashing, film separation, and droplet stripping, can now be physically captured with reduced computing resources by allowing transition from continuous liquid structures to discrete parcels. The employed modeling strategy allows for high resolution of the oil film at the walls and tracking of the droplets while minimizing mesh size and computing needs. Current results suggest that the proposed DPM-VoF-DPM method can be an efficient and accurate tool for locating air and oil in aero-engine transmission systems.
Application of Tuned Vibration Absorber Concept to Blisk Ring Dampers: A Nonlinear Study
Authors: Lupini Andrea , Mitra Mainak , Epureanu Bogdan I.
Published: November 2019

In this study, a novel design for ring dampers is proposed, where the concept of tuned vibration absorbers is leveraged to substantially increase damper effectiveness while minimizing potential stresses near the blade root. Tuned absorbers have been used in the past to reduce the forced response amplitudes of both mechanical and civil structures. The absorber natural frequency is tuned to the targeted frequency of the host structure where it is attached. The vibration reduction mechanism relies on energy transfer from the host structure to the absorber. The novel design technique proposed here uses a vibration absorber approach to achieve energy transfer from the blisk to the damper, which leads to larger damper motion. This enables energy dissipation due to friction, reducing vibrations even in blade dominated modes. An academic finite element model of a blisk with a ring damper is used to demonstrate the novel tuned damper concept and design technique. The geometric mistuning of the damper due to the presence of a gap in the ring structure is also taken into account. The results demonstrate the validity of the proposed tuned damper concept, showing a substantial vibration amplitude reduction compared to the linear baseline results, in which the damper is not tuned or absent.
Novel and Applicable Method to Determine Equivalent Strain Range and Equivalent Strain Direction Under Multiaxial Non-Proportional Loading
Authors: Krouse Charles R. , Musgrove Grant O. , Kim Taewoan , Lee Seungmin , Lee Muhyoung
Published: November 2019

When considering mechanical components that are subjected to complex loading conditions, it is difficult to achieve accurate predictions of low-cycle fatigue life. For multiaxial and non-proportional loads, the principal strain directions vary in three-dimensional space with time. The commonly accepted methods to determine fatigue life under such loading conditions are based on a critical plane approach, and they rely heavily on accurate strain range estimates. However, there is no singly accepted method to determine the critical plane, equivalent strain magnitude, or equivalent strain direction. Furthermore, current suggestions are computationally intensive and challenging to implement. This paper offers a novel and concise method to accurately determine equivalent strain range and equivalent strain direction under multiaxial, non-proportional loading in three-dimensional space. A practical approach is provided for implementing the method, and an example of an application using a finite element model of a first stage turbine blade is discussed. To demonstrate the approach, ANSYS Mechanical was used to simulate a turbine blade under transient loading conditions and to determine the resulting strains. Equivalent strain range results were applied to a Coffin-Manson relation to determine the low-cycle fatigue life of every node within the finite element model of the first stage turbine blade. The post-processing of the strain predictions, which yielded the equivalent strain range and equivalent strain direction, is discussed in detail.
80 Years Open GT Development in Baden
Authors: Wettstein Hans E.
Published: November 2019

On 07.07.1939 the Neuchatel gas turbine passed its performance test under the supervision of Aurel Stodola [1]. This was the world’s first open gas turbine for electric power generation in commercial operation. It launched the past eighty year period of further development and corresponding market growth. The Baden area played an important role.

The aim of this paper is to complete the already published comprehensive historical information with two additional aspects especially regarding the second 40 years, in which the author was an involved contemporary witness:

The first is how the predominance of something like a local spirit integrated both a considerable share of foreign engineering staff and also the changes of the ownership of the technology from Brown Boveri to ABB and then to Alstom and recently to GE and Ansaldo.

The second aspect is the inside view of the author, who has both shaped and suffered these gas turbine developments in several job positions allowing direct contact to both top management and shop floor workers.

These two aspects will be integrated in the historical sequence. As a rule the roles of the persons acting after the seventies are given but not their names.

The history of the involved companies has caught much attention of media and writers. After the formation of ABB it was used for both celebrating outstanding management performance and despicable management mistake. I will add as an engineer my insider view to this and mention the corresponding book references.

This paper is limited to the mainstream open GT development for space reasons and therefore omits other interesting side developments of BBC such as closed Helium cycles, IGCC applications and compressed air energy storage as well as the other products of BBC, which all played a role in equalizing the business cycles.
On the Frequency Dependency of Tilting-Pad Journal Bearings
Authors: Wagner Laurence F.
Published: November 2019

Controversy regarding the dynamic modeling of tilting-pad journal bearings (TPJB) has existed for years, with the question of the effective stiffness and damping properties, and the requirement for consideration of frequency dependency, being of great concern. There is a partial disconnect between the results of theoretical and many experimental investigations. This paper attempts to examine this issue in more of a macro sense; broadening the scope of the geometric and operating domains, and in turn expanding an understanding of related frequency effects. The investigation hinges on a single-pad, single degree-of-freedom (DOF) model that represents various geometries and operating conditions for a full bearing. The results clearly show that the dynamic coefficients must be dependent upon the “exciting” frequency, and that the dependency is primarily associated with the pad rotational damping.
Offshore Experience With Thermal Turbomachinery in Norwegian Petroleum Industry Through Fifty Years: A Review of Major Milestones, Lessons Learned and Impacts
Authors: Lynghjem Arne , Bakken Lars E. , Naess Tore
Published: November 2019

From the beginning of the offshore oil & gas industry in Norway in 1969, the applications of thermal turbomachinery did often involve new and innovative conceptual solutions. In some cases they had to be followed by extensive modifications on the offshore platforms afterwards, which have resulted in valuable lessons learned.

The list of offshore challenges for thermal turbomachinery has gradually increased over time. The initial challenges involved very high pressure gas compression, low weight machinery, small footprints, low offshore maintenance needs, reliable and safe operation. Later, it also involved strict environmental regulations, reduced emissions, remote control, subsea and multiphase operations.

This paper reviews major technological milestones for offshore application of thermal turbomachinery over five decades. Further, it presents a collation of the experiences that have been made and discussions of their impact on other applications.

The intension of the paper is to transfer experience, and the target group is young engineers and other engineers working with thermal turbomachinery in oil & gas industry.

Initially, the technological milestones were achieved on improvement of centrifugal compressor instabilities in high pressure application, the shift from large heavy duty gas turbines to aeroderivatives and pioneering work on Norwegian small gas turbines. It was followed by a clear trend from gas turbine to electric motor drive, preferably variable speed drive, and a central gas turbine power plant. In the 1990es and beyond, ambitious efforts were made on reduced emissions of CO2 and NOx from gas turbines. Further, achievements were made on dry running gas seals, active magnetic bearings and currently hermetically enclosed compressors without shaft seals. After 2010, the ultimate solution was achieved with combined compressor and electric motor casing, entailing subsea compression and wet gas compression.
Unsteady Passing Wake Effects on Turbine Blade Tip Aerodynamic and Aerothermal Performance With Film Cooling
Authors: Zhang Bo , Qiang Xiaoqing , Teng Jinfang , Lu Shaopeng
Published: November 2019

In this paper, upstream unsteady passing wake effects on the rotor blade tip with film cooling have been numerically examined. The geometry and flow conditions of the first stage of GE-E3 high-pressure turbine have been used to obtain the unsteady three-dimensional blade tip flow and heat transfer characteristics. The first stage of GE-E3 high-pressure turbine has 46 guide vanes and 76 rotor blades. In the process of calculation, compromise the computational resources and accuracy to simplify the number of the guide vane and rotor blade to 38:76. Namely, each computational domain comprises of one guide vane and two rotor blades. The computational boundary conditions are consistent with the GE-E3 annular cascade test conditions. In the case of 1% blade span tip clearance, through comparing the steady results, time-averaged and time-resolved unsteady results, the investigation of the unsteady passing wake effects on flat tip aerodynamic and aerothermal performance without film cooling holes (NC) and three cases with film cooling holes are conducted. To be specific, near the leading edge (C123), at the central area (C456) and near the trailing edge (C789). This paper emphasizes the variation of leakage flow and heat transfer coefficient at different unsteady instants. The results show that the time-averaged leakage flow is pretty similar to the steady results, but the increment of the leakage flow can rise to more than 8% at the maximum envelope. Moreover, the heat transfer coefficient discrepancy between steady results and time-averaged results is almost below 4%, but the dramatic growth of the instantaneous heat transfer coefficient along the pressure side is in excess of 20% due to the shift of the pressure spot.
Successive Aeroacoustic Transfer of Leading Edge Serrations From Single Airfoil to Low-Pressure Fan Application
Authors: Biedermann Till M. , Kameier F. , Paschereit C. O.
Published: November 2019

Leading edge serrations are identified as an effective passive treatment for reducing fan broadband noise due to high turbulent inflow conditions. This paper aim to investigate the isolated effect of serrated applications in a rotating frame, covering the aerodynamic and aeroacoustic performance. With this purpose, a serration design, previously analyzed in the rigid domain, is transferred to the rotating frame, following a successive approach in form of a continuous increase of the fan blade number. This is considered as a feasible way to isolate the serration effects and to provide information on fan blade interaction and possible masking effects. Comparing blades with straight and serrated leading edges by analyzing the spectral noise reduction and the overall level results in deep insights in the underlying noise reduction mechanisms. Furthermore, analysis of phase differences by means of the wall pressure fluctuations leads to the identification of rotating flow phenomena, non-synchronized with the rotor speed. The results obtained indicate an efficient noise reduction by the serrations in the vicinity of the design point. By use of the presented successive approach, noise reduction phenomena observed with the full rotor could be identified to be of either aeroacoustic or aerodynamic nature. A reduced noise is observed for the full rotor case, showing a reduction of blade interaction effects. At reducing flow coefficients, an improved stall margin of the serrated rotor is identified that also affects the aeroacoustic signature.
Experimental Investigation of the Discharge Behavior of Cavitating and Non-Cavitating Flow Through Rotating Radial Orifices
Authors: Cordes Laura , Schwitzke Corina , Bauer Hans-Jörg
Published: November 2019

The transport of a flow from a static system into a rotating system can be realized by means of orifices in the rotating wall. In this paper the experimental study of a liquid flowing through a radial, sharp-edged orifice with a l/d-ratio of 1.56 in a rotating shaft is presented. The discharge coefficient cd for (circumferential) orifice speeds of up to 24 m s−1 and Reynolds numbers ranging from Red = 1.2 × 104 to 3.4 × 104 is evaluated for an oil with a density of 920 kg m−3 and a kinematic viscosity of 5.3 × 10−6 m s−2.

A modular test rig was designed, consisting of two concentric rotating shafts forming an annular duct. The outer shaft is fitted with the orifices through which the liquid passes from the static into the rotating system. The modularity allows the exchange of the shaft element containing the orifices. For this study two shaft elements with 5 or 12 radial, cylindrical, sharp-edged orifices were used. Thus, a wider range of flow velocities through a single orifice was achieved.

This study is the first to illustrate the effect of cavitation in a rotating orifice. Outside the cavitation regime a change of the approaching flow represented by the velocity ratio causes a change of the discharge coefficient while within the cavitation regime cd additionally depends on the cavitation parameter. A relationship for the flow contraction in the cavitation regime depending on the orifice velocity and the pressures upstream and downstream of the orifice is derived.

For a second set of orifices, where the liquid exits the rotor into the surrounding air, a significant regime change depending on the ratio of orifice rotational speed and flow velocity occurs. For higher flow velocities through the orifice this change occurs for lower orifice speeds. A likely cause is the onset of cavitation.