bluuebunny/crossref_metadata_2025 huggingface dataset:
Mitigating Mistrust? Participation and Expertise in Hydraulic Fracturing Governance
Authors: Neville Kate J. , Weinthal Erika
Published: September 2016

In Canada's Yukon Territory, a legislative committee was tasked with assessing the risks and benefits of hydraulic fracturing. The committee designed an extensive participatory process involving citizens and experts; however, instead of information access and public hearings fostering an open dialogue and trust, these two channels failed to de‐polarize debates over hydraulic fracturing. We argue that mistrust was reinforced because (1) weak participatory processes undermined the goals of public involvement, (2) scientific evidence and scientists themselves were not accepted as neutral or apolitical, and (3) strategic fostering of mistrust by actors on both sides of a polarized issue intensified existing doubt about the integrity and credibility of the process. The implications of a failure to restore trust in government are significant, not only for the issue of hydraulic fracturing, but for governance more broadly, as mistrust has spillover effects for subsequent public negotiations.
Central Andean magmatism can be constrained by three ubiquitous end‐members
Authors: Blum‐Oeste Magdalena , Wörner Gerhard
Published: September 2016

The geochemical character of primary magmas and the nature of crustal melts remain poorly constrained at the active continental margin of the Central Andes, where the crustal thickness is >70 km. We identify three end‐members and constrain their full major and trace element compositions by polytopic vector analysis (PVA). The end‐members include two mafic parent magmas: (1) a slightly evolved calcalkaline basaltic andesite derived from the fluid‐fluxed mantle wedge that is typical of the Andes in general and (2) a strongly LREE‐enriched basalt akin in its trace element pattern to back‐arc shoshonites. (3) The third end‐member is a variably HREE‐depleted rhyodacite representing partial melts of lower to middle crustal lithologies. We propose that these end‐members are ubiquitous and typical of such thick‐crust settings, and can explain – in highly variable mixing proportions – the entire compositional range of Central Andean magmatism.
A blinded, randomized, placebo‐controlled, dose determination trial of lokivetmab (ZTS‐00103289), a caninized, anti‐canine IL‐31 monoclonal antibody in client owned dogs with atopic dermatitis
Authors: Michels Gina M. , Ramsey Deborah S. , Walsh Kelly F. , Martinon Olivier M. , Mahabir Sean P. , Hoevers Jacquelien D. , Walters Rodney R. , Dunham Steven A.
Published: September 2016

Background

Pruritus is the hallmark clinical sign of atopic dermatitis (AD) in dogs. Lokivetmab, a caninized anti‐canine IL‐31 monoclonal antibody, reduced pruritus and associated inflammatory skin lesions in a proof‐of‐concept study in dogs with AD.

Hypothesis/Objectives

The objective was to describe lokivetmab dose response in a randomized, double blind, placebo‐controlled trial.

Animals

Clinicians at 15 referral clinics enrolled 211 client owned dogs with a history of chronic AD.

Methods

Dogs were randomized to treatment with lokivetmab (0.125, 0.5 or 2.0 mg/kg) or placebo administered subcutaneously once on Day 0. Dog owners assessed visual analog scale (VAS) scores of pruritus on days 0, 1, 2, 3, 7, 14, 21, 28, 35, 42, 49 and 56. Clinicians assessed Canine AD Extent and Severity Index (CADESI‐03) scores on days 0, 7, 14, 28, 42 and 56.

Results

Treatment with lokivetmab (2 mg/kg) resulted in a greater percentage reduction from baseline in owner assessed pruritus (days 1–49) and clinician assessed CADESI‐03 scores (days 7–56) compared to placebo (P < 0.05); differences were achieved in lower dose groups but at later time points and for shorter duration for both owner assessed pruritus (0.5 mg/kg, days 2–35; 0.125 mg/kg, days 7–21) and clinician assessed CADESI‐03 scores (0.5 mg/kg and 0.125 mg/kg, Day 14).

Conclusions and clinical importance

Lokivetmab (0.5, 2.0 mg/kg) reduced pruritus compared to placebo for at least 1 month. Level and duration of response increased with increasing dose. Further studies are needed to better understand variability in individual responses across a broader population of dogs with AD.
Alopecia universalis in a dog with testicular neoplasia
Authors: Outerbridge Catherine A. , White Stephen D. , Affolter Verena K.
Published: September 2016

Objective

To describe a case of testicular neoplasia and alopecia universalis in a dog, and successful treatment of the latter with ciclosporin.

Animal

Twelve‐year‐old intact male wirehaired fox terrier.

Methods

Castration, skin biopsy for histopathology, lymphocyte immunophenotyping and clonality analysis of the canine T‐cell receptor gamma locus (TCRγ) rearrangement.

Results

The dog presented with symmetrical generalized alopecia. Testicular enlargement was noted which on castration was determined to be caused by bilateral interstitial cell tumours, Sertoli cell tumours and a unilateral seminoma. During the four months after castration the alopecia became more severe and widespread. Histopathology of the skin showed moderate, multifocal, mural folliculitis, peribulbar mucinosis and lymphocytic bulbitis, and targeting of anagen hair follicles. Immunophenotyping of the infiltrate showed a population of well‐differentiated, small CD3‐positive T lymphocytes, some expressing CD4 and others CD8. Molecular analysis revealed a polyclonal lymphocytic infiltrate, substantiating the diagnosis of alopecia areata rather than lymphoma. Treatment with ciclosporin (4.6 mg/kg) and ketoconazole (4.6 mg/kg) resulted in complete hair regrowth.

Conclusion and clinical importance

Ciclosporin treatment, in combination with ketoconazole, can be effective for treatment of alopecia universalis in the dog. Alopecia universalis may present with clinically noninflammatory, symmetrical, generalized alopecia, mimicking an endocrine alopecia, and skin biopsies are needed to confirm the diagnosis.
Phylogenetic relationships of the largest lungless tetrapod (Gymnophiona, Atretochoana) and the evolution of lunglessness in caecilians
Authors: Maciel Adriano O. , Sampaio Maria I. C. , Hoogmoed Marinus S. , Schneider Horacio
Published: September 2016

Atretochoana eiselti is the largest extant lungless tetrapod. This species is one of the fully aquatic caecilian amphibians of the family Typhlonectidae. It is unique within Gymnophiona in lacking lungs and having sealed choanae, a snake‐like postoccipital jaw articulation, and some other greatly divergent features. Phylogenetic relationships of the five typhlonectid genera have been estimated only once previously, in an analysis of morphological data. Here we infer for the first time integrating molecular and morphological data, the relationships of all typhlonectid genera. Although Atretochoana and Potomotyphlus share several derived character states in morphology, some of which linked to a reduction of the pulmonary importance in respiration, Potomotyphlus is more closely related to Typhlonectes than to Atretochoana. Consequently, we conclude that evolutionary loss of lungs or gradual reduction of their importance in respiration in Atretochoana and Potomotyphlus was convergent within this poorly known group of amphibians.
Morphological assessment of the Octopus vulgaris species complex evaluated in light of molecular‐based phylogenetic inferences
Authors: Amor Michael D. , Norman Mark D. , Roura Alvaro , Leite Tatiana S. , Gleadall Ian G. , Reid Amanda , Perales‐Raya Catalina , Lu Chung‐Cheng , Silvey Colin J. , Vidal Erica A. G. , Hochberg Frederick G. , Zheng Xiaodong , Strugnell Jan M.
Published: September 2016

Cryptic species are common in the ocean, particularly among marine invertebrates such as octopuses. Delineating cryptic species is particularly problematic in octopus taxonomy where the plasticity recorded among taxonomic characters often results in low resolution at the species level. This study investigated the morphological relationships among seven phylogenetic clades (identified using cytochrome c oxidase subunit I) of the broadly distributed Octopus vulgaris species complex and close relatives. Morphological analyses in this study were successful in delimiting O. sinensis, Brazilian O. vulgaris and O. vulgaris sensu stricto, which was congruent with the molecular findings of this study. Analyses based on male morphology were successful in distinguishing 14 of 15 total pairwise comparisons and proved to be a more reliable indicator of species‐level relationships in comparison with female morphology. The majority of characters with the greatest discriminatory power were male sexual traits. Significant morphological differences were also recorded among sampling localities of conspecifics, with phenotype showing correlation with local environmental data. The findings of this study support the hypothesis that multiple O. vulgaris‐like species are currently being incorrectly treated under a single species name, O. vulgaris. Octopuses being exported globally under the name O. vulgaris are of extremely high fisheries market value and profile. Our findings have potentially significant implications for the naming and conservation of commercially harvested members of this species complex throughout their ranges.
On Goren–Oort stratification for quaternionic Shimura varieties
Authors: Tian Yichao , Xiao Liang
Published: September 2016

Let$F$be a totally real field in which a prime$p$is unramified. We define the Goren–Oort stratification of the characteristic-$p$fiber of a quaternionic Shimura variety of maximal level at$p$. We show that each stratum is a$(\mathbb{P}^{1})^{r}$-bundle over other quaternionic Shimura varieties (for an appropriate integer$r$). As an application, we give a necessary condition for the ampleness of a modular line bundle on a quaternionic Shimura variety in characteristic$p$.
Effects of continuous positive airway pressure and isocapnic‐hypoxia on cerebral autoregulation in patients with obstructive sleep apnoea
Authors: Waltz Xavier , Beaudin Andrew E. , Hanly Patrick J. , Mitsis Georgios D. , Poulin Marc J.
Published: September 2016

Key points

Altered cerebral autoregulation (CA) in obstructive sleep apnoea (OSA) patients may contribute to increased stroke risk in this population; the gold standard treatment for OSA is continuous positive airway pressure, which improves cerebrovascular regulation and may decrease the risk of stroke.

Isocapnic‐hypoxia impairs CA in healthy subjects, but it remains unknown in OSA whether impaired CA is further exacerbated by isocapnic‐hypoxia and whether it is improved by treatment with continuous positive airway pressure.

During normoxia, CA was altered in the more severe but not in the less severe OSA patients, while, in contrast, during isocapnic‐hypoxia, CA was similar between groups and tended to improve in patients with more severe OSA compared to normoxia.

From a clinical perspective, one month of continuous positive airway pressure treatment does not improve CA.

From a physiological perspective, this study suggests that sympathetic overactivity may be responsible for altered CA in the more severe OSA patients.

Cerebral autoregulation (CA) impairment may contribute to the increased risk of stroke associated with obstructive sleep apnoea (OSA). It is unknown if impaired CA is further exacerbated by isocapnic‐hypoxia and whether it is improved by treatment of OSA with continuous positive airway pressure (CPAP). CA was assessed during wakefulness in 53 OSA patients (50.3 ± 9.3 years) and 21 controls (49.8 ± 8.6 years) at baseline and following a minimum of 1 month of effective CPAP therapy (OSA patients, n = 40). Control participants (n = 21) performed a follow‐up visit to control for time effects within OSA patients between baseline and the post‐CPAP visit. Beat‐by‐beat middle cerebral artery blood flow velocity and mean arterial blood pressure (MBP), and breath‐by‐breath end‐tidal partial pressure of CO2 () were monitored. CA was determined during normoxia and isocapnic‐hypoxia using transfer function (phase and gain) and coherence analysis (including multiple and partial coherence (using MBP and as inputs)) in the very low frequency range (0.03–0.07 Hz). OSA patients were divided into two subgroups (less severe and more severe) based upon the median respiratory disturbance index (RDI). During normoxia, the more severe OSA patients (RDI 45.9 ± 10.3) exhibited altered CA compared to controls and the less severe OSA patients (RDI 24.5 ± 5.9). In contrast, during isocapnic‐hypoxia, CA was similar between groups. CPAP had no effect on CA. In conclusion, CA is altered in the more severe OSA patients during normoxia but not during isocapnic‐hypoxia and CPAP treatment does not impact CA.
Trajectory Planning for Robot Manipulators Considering Kinematic Constraints Using Probabilistic Roadmap Approach
Authors: Yu Xiaowen , Zhao Yu , Wang Cong , Tomizuka Masayoshi
Published: September 2016

Trajectory planning is a fundamental problem for industrial robots. It is particularly challenging for robot manipulators that transfer silicon wafers in an equipment front end module (EFEM) of a semiconductor manufacturing machine where the work space is extremely limited. Existing methods cannot give satisfactory performance since they usually solve the problem partially. Motivated by this demand in industrial applications and to solve all aspects of the problem, this paper proposes to learn the work environment beforehand by probabilistic roadmap (PRM) method for collision avoidance. The cycle time preference and the robot kinematic hard constraints are considered properly. A constrained optimization problem is formulated with the shortest path searched from the roadmap and parametrized by a cubic B-spline curve, which simplifies the optimization process.
Many-Objective Optimal and Robust Design of Proportional-Integral-Derivative Controls With a State Observer
Authors: Sardahi Yousef , Sun Jian-Qiao , Hernández Carlos , Schütze Oliver
Published: September 2016

This paper presents a many-objective optimization (MaOO) approach to design control and observer gains simultaneously. The many-objective optimization (MaOO) approach finds trade-offs between different nonagreeable design goals. We report the MaOO results of a proportional-integral-derivative (PID) control with a state estimator applied to a second-order oscillator. The overall system is optimized to minimize the peak time, overshoot, tracking error, and control energy, and maximize the rejection of external disturbance and measurement noise, while the relative stability, which is defined by maximum real part of eigenvalues of the closed-loop system, is constrained to be less than or equal to −1. The numerical simulations show promising findings of the proposed method.
Control-Oriented Model of Molar Scavenge Oxygen Fraction for Exhaust Recirculation in Large Diesel Engines
Authors: Nielsen Kræn Vodder , Blanke Mogens , Eriksson Lars , Vejlgaard-Laursen Morten
Published: September 2016

Exhaust gas recirculation (EGR) systems have been introduced to large marine engines in order to reduce NOx formation. Adequate modeling for control design is one of the bottlenecks to design EGR control that also meets emission requirements during transient loading conditions. This paper therefore focuses on deriving and validating a mean-value model of a large two-stroke crosshead diesel engine with EGR. The model introduces a number of amendments and extensions to previous, complex models and shows in theory and practice that a simplified nonlinear model captures all essential dynamics that is needed for EGR control. Our approach is to isolate and reduce the gas composition part of the more complex models using nonlinear model reduction techniques. The result is a control-oriented model (COM) of the oxygen fraction in the scavenge manifold with three molar flows being inputs to the COM, and it is shown how these flows are estimated from signals that are commonly available. The COM is validated by first comparing the output to a simulation of the full model, then by comparing with measurement series from two engines. The control-oriented nonlinear model is shown to be able to replicate the behavior of the scavenge oxygen fraction well over the entire envelope of load and blower speed range that are relevant for EGR. The simplicity of the new model makes it suitable for observer and control design, which are essential steps to meet the emission requirements for marine diesel engines that take effect from 2016.
Effect of Particle Size and Aggregation on Thermal Conductivity of Metal–Polymer Nanocomposite
Authors: Li Xiangyu , Park Wonjun , Chen Yong P. , Ruan Xiulin
Published: September 2016

Metal nanoparticle has been a promising option for fillers in thermal interface materials due to its low cost and ease of fabrication. However, nanoparticle aggregation effect is not well understood because of its complexity. Theoretical models, like effective medium approximation model, barely cover aggregation effect. In this work, we have fabricated nickel–epoxy nanocomposites and observed higher thermal conductivity than effective medium theory predicts. Smaller particles are also found to show higher thermal conductivity, contrary to classical models indicate. A two-level effective medium approximation (EMA) model is developed to account for aggregation effect and to explain the size-dependent enhancement of thermal conductivity by introducing local concentration in aggregation structures.
Tribological Studies of Transmission Oil Dispersed With Molybdenum Disulfide and Tungsten Disulfide Nanoparticles
Authors: Srinivas V. , Thakur R. N. , Jain A. K. , Saratchandra Babu M.
Published: September 2016

This paper compares the tribological properties of transmission oil dispersed with molybdenum disulfide (MoS2) and tungsten disulfide (WS2) nanoparticles. Lubricant samples are prepared by dispersing MoS2 and WS2 nanoparticles in 0.5 wt.% in transmission oil. The nanoparticles are stabilized in the lubricant by surface modification with surfactant SPAN 80. The stability of the lubricant in terms of size variation of dispersed nanoparticles is evaluated using particle size analyzer. The antiwear, antifriction, and extreme pressure (EP) properties are tested on a four-ball wear tester and a comparison is made to assess the relative performance of MoS2 and WS2 nanoparticles. The friction and wear characteristics of lubricant dispersed with nanoparticles are strongly dependent upon the load taken into consideration. The lubricant dispersed with WS2 nanoparticles gave higher weld load and load wear index (LWI) than that of lubricant dispersed with MoS2 nanoparticles. The metallographic studies show that under high load conditions, the WS2 nanoparticles deposit more than MoS2 nanoparticles, thereby giving better performance at higher load conditions.
Effects of Typical Machining Errors on the Nonlinear Dynamic Characteristics of Rod-Fastened Rotor Bearing System
Authors: Liu Yi , Liu Heng , Wang Nanshan
Published: September 2016

The effects of typical machining errors on the dynamic features of rod-fastened rotor bearing system (RBS) are studied in this paper. Three micron-sized machining errors are considered in a three-dimensional (3D) rod-fastened model. The static effects of machining errors are investigated by applying finite element method. Results demonstrate that machining errors not only bring about mass eccentricity but also cause obvious rotor bending due to large pretightening force. Then, nonlinear dynamic features such as stability and bifurcation are analyzed by using target-shooting technique, track-following method, and Floquet theory. Analysis data indicate that rotor bending originated from machining errors reduces the system stability evidently. It is also observed that the vibration value continues to go up after critical speed as rotating speed increases. It is a particular property compared with integral rotor. It explains the reason why the machining precision of rod-fastened rotor is much higher than that of the corresponding integral rotor to some extent. Moreover, differences between machining errors are compared and the results show that the machining precision of axial assembly interfaces should be paid more attention in the rod-fastened rotor design.
Computational Investigation of a Shrouded Vertical Axis Wind Turbine
Authors: Vafiadis K. , Fintikakis H. , Zaproudis I. , Tourlidakis A.
Published: September 2016

In urban areas, it is preferable to use small wind turbines which may be integrated to a building in order to supply the local grid with green energy. The main drawback of using wind turbines in urban areas is that the air flow is affected by the existence of nearby buildings, which in conjunction with the variation of wind speed, wind direction and turbulence may adversely affect wind energy extraction. Moreover, the efficiency of a wind turbine is limited by the Betz limit. One of the methods developed to increase the efficiency of small wind turbines and to overcome the Betz limit is the introduction of a converging – diverging shroud around the turbine. Several researchers have studied the effect of shrouds on Horizontal Axis Wind Turbines, but relatively little research has been carried out on shroud augmented Vertical Axis Wind Turbines.

This paper presents the numerical study of a shrouded Vertical Axis Wind Turbine. A wide range of test cases, were examined in order to predict the flow characteristics around the rotor, through the shroud and through the rotor – shroud arrangement using 3D Computational Fluid Dynamics simulations. The power output of the shrouded rotor has been improved by a factor greater than 2.0. The detailed flow analysis results showed that there is a significant improvement in the performance of the wind turbine.
Thermal Mechanical Fatigue and Creep Interaction in Turbine Housing Divider Wall Design
Authors: Guo Wei , Guo Henry
Published: September 2016

Turbochargers are commonly used to boost internal combustion engines for both on and off high way applications to meet current emission regulations and performance requirements. Divider wall turbochargers have two exhaust gas inlets and twin scrolls with the divider cast wall connected. Turbochargers with divider wall feature could conserve an engine’s exhaust pulse kinetic energy for great turbine wheel efficiency. It is widely used in 6-cylinder engine applications. Turbochargers with divider wall configuration operate in very hostile conditions with high temperature and great thermal gradient. Using thinner divider wall feature benefits aerodynamic performance, but with the configuration turbine housing may show cracks and large deformation during thermal cycling. In order to achieve the balance between mechanic and aerodynamic, design study of a reasonable divider wall is required. This paper first presents the initial design with thinner divider wall, which experienced severe cracking problem in the divider wall location during the engine thermal shock testing. In order to capture the failure mode at divider wall region, finite element analysis (FEA) with thermal mechanical fatigue (TMF) and creep interaction is performed. The simulation repeats the failure mode very well which shows this numerical analysis method is convincing and fast for further study. Base on the failure case and successful cases, TMF with creep interaction simulation criteria is proposed. The criteria could be used as the reference for the further design, and the design should be controlled within the criteria limit. Based on the methodology and the criteria, the new design is analyzed and the simulation result shows the risk is low. Engine thermal shock testing is done for the final validation. This design has acceptable cracks and no large deformation at divider wall location under the testing condition. TMF and creep interaction gives a right and fast methodology to capture the failure mode at divider wall. Meanwhile it provides a knowledge base for the turbine housing divider wall design.
Design of a 400 kW Gas Turbine Prototype
Authors: Jaatinen-Värri Ahti , Nerg Janne , Uusitalo Antti , Ghalamchi Behnam , Uzhegov Nikita , Smirnov Alexander , Sikanen Eerik , Grönman Aki , Backman Jari , Malkamäki Matti
Published: September 2016

Decentralized power and heat generation is a growing trend throughout the world. In smaller applications, electrical power output less than few megawatts, reciprocating engines have dominated the market. In recent years, small sized gas turbines have emerged as challengers for the reciprocating engines. The small gas turbines have a growing share of the decentralized energy market, which itself is rapidly growing. Hence, improvements in small gas turbine efficiency have a significant impact from the economic and environmental perspective.

In this paper, the design of a high efficiency 400 kW gas turbine prototype is described and discussed. The prototype is a two-spool, recuperated and intercooled gas turbine where both spools comprise of a radial compressor and turbine, a permanent magnet electric generator, an axial and two radial active magnetic bearings and two safety bearings.

The prototype design was divided into five categories and each of the categories are discussed. The categories were: the process design, the turbomachinery design, the generator and electrical design, bearing design and rotor dynamic analysis, and mechanical design. The design of recuperator, intercooler, and combustion chamber were outsourced. Hence, they are not discussed in this paper.

The prototype design process showed the readiness of the chosen technological selections, as well it showed that the type of machine under discussion can be designed and manufactured.
Dynamic Model of a 10 MW Supercritical CO2 Recompression Brayton Cycle
Authors: Lambruschini Fabio , Liese Eric , Zitney Stephen E. , Traverso Alberto
Published: September 2016

In this work, the National Energy Technology Laboratory (NETL) in collaboration with the Thermochemical Power Group (TPG) of the University of Genoa have developed a dynamic model of a 10 MW closed-loop supercritical CO2 (sCO2) recompression Brayton cycle plant in the MATLAB-Simulink environment. The sCO2 cycle modeled here is a closed cycle with an external thermal source used to heat the sCO2 working fluid before it is expanded in a turbine. The turbine exhaust heat is recuperated using high- and low-temperature recuperators, with mixing of two compressor outlets between the recuperators (on the cold-side). About two thirds of the low-pressure sCO2 is compressed by a main compressor, after passing through a cooler, while the remaining working fluid flows directly through a bypass compressor. The reference fluid properties (REFPROP) method by the National Institute of Standards and Technology is used to provide the thermodynamic and transport properties for sCO2 over the cycle temperature and pressure range because the sCO2 behavior is highly non-ideal, especially at the inlet of the two compressors. Dynamic simulations have been carried out to assess the behavior of the plant during a typical process disturbance.
A Novel Small Scale Liquefied Natural Gas Production Process at Filling Stations: Thermodynamic Analysis and Parametric Investigation
Authors: Ancona M. A. , Bianchi M. , Branchini L. , De Pascale A. , Melino F. , Mormile M. , Palella M.
Published: September 2016

In the last years, the increased demand of the energy market has led to the increasing penetration of renewable energies in order to achieve the primary energy supply. However, simultaneously natural gas still plays a key role in the energy market, mainly as gaseous fuel for stationary energy generation, but also as liquefied fuel, as an alternative to the diesel fuel, in vehicular applications. Liquefied Natural Gas (LNG) is currently produced in large plants directly located at the extraction sites.

In this study, the idea of realizing plug & play solutions to produce LNG directly at vehicle’s filling stations has been investigated. A novel process of LNG production for filling stations has been analyzed, consisting in a single stage Joule-Thompson isenthalpic expansion process, with intercooled compression. Furthermore, the presented layout has been developed with the purpose of optimizing the energy consumption of the plant, obtaining moderately pressurized LNG.

With the aim of investigating the feasibility of this novel LNG generation process, a thermodynamic analysis has been carried out and presented in this study. Moreover, the minimization of energy consumption has been investigated with a parametric analysis, in order to optimize the LNG production and to maximize the efficiency of the process. Furthermore, novel performance indicators have been defined, in order to account the efficiency of the LNG production process. Results of the optimization analysis show that, with the proposed layout, an energy consumption equal to about 1.9 MJ/kg of produced LNG can be achieved.
Experimental Study of the Influence of the Operating Parameters on the Performance and Capability of a Mixed-Flow Multiphase Pump
Authors: Serena Alberto , Bakken Lars E.
Published: September 2016

Multiphase flow introduces many challenges in turbomachines analysis and operation, as each of the phases responds differently to the forces in the hydraulic channel, and the mechanical and thermal interaction among the phases has to be taken into account too. Especially when very high gaseous fractions need to be covered, due to the concurrent physics involved and transient phenomena, a proper machine characterization cannot be limited to an overall description of the performance, but it needs to rely on advanced analysis tools which can reveal the local phenomena responsible for performance degradation and instabilities.

The flow regimes vary from a homogeneous distribution of fine bubbles, evenly dispersed and carried away by the main flow, to more complex flow patterns, especially if bubbles coalesce and adhere to a wide portion of the channel wall.

Tests are performed on a multiphase pump facility recently designed by the authors, which allows a complete optical access to the pump channels and fine adjustments in the inlet configuration and the tip clearance gap.

The investigation focuses on the effect of the mixture inlet pressure and machine rotational speed on performance and stability. Increasing values of the inlet pressure reduce the density ratio between the phases, thus making them become more coupled; this results in a milder performance degradation and a wider stable operating range.

Accurate flow visualization through the pump transparent casing complements the study, allowing an immediate and detailed local phenomena description.

The results are presented under performance and surging curves, showing the gas-handling capability dependence on the actual conditions.

These analyses fully characterize the machine behavior, define the operating zones which should be avoided, and will serve later to implement a control strategy to keep the machine in a safe regime.
Gas Turbine Shutdown Thermal Analysis and Results Compared With Experimental Data
Authors: Reddy Vishnu Vardhan , Selvam Kathiravan , De Prosperis Roberto
Published: September 2016

Gas turbines undergo transient operation during startup, load change and shutdown. Understanding transient behaviour is very critical as it has significant influence on the safety and life of turbine components. The transient thermal analysis of the gas turbine is one of the most important aspects to evaluate the clearances and life of various components of the unit. The understanding of the shutdown phenomena is very complex due to huge transient variation in the temperature inside the turbine. In the shutdown process natural convection plays an important role as there is very less flow inside the turbine, which is difficult to model and predict with the current state of art tools.

A Flange to Flange 2D axi-symmetric thermal model was considered for this analysis to predict the overall temperature distribution of the gas turbine components with suitable approximations. In this paper detailed experimental results of the GE frame 5 shut down are analysed and numerical modelling was attempted to match the experimental results. Several analytical studies are carried out to understand the various effects including the “heat soak” effect. These effects were captured in both experimental and analytical studies.
Heat Transfer Correction Methods for Turbocharger Performance Measurements
Authors: Schinnerl Mario , Seume Joerg , Ehrhard Jan , Bogner Mathias
Published: September 2016

Turbocharger performance maps used for the matching process with a combustion engine are measured on test benches which do not exhibit the same boundary conditions as the engine. However, these maps are used in engine simulations, ignoring that the compressor and turbine aerodynamic performance is rated on the basis of quantities which were measured at positions which do not coincide with the respective system boundaries of the turbomachinery.

In the operating range of low to mid engine speeds, the ratio between the heat flux and the work done by the turbine and the compressor is much greater than at high speeds where heat transfer phenomena on the compressor side can usually be neglected. Heat losses on the turbine side must be taken into account even at higher shaft speeds when dealing with isentropic turbine efficiencies.

Based on an extensive experimental investigation a one-dimensional heat transfer model is developed. The compressor and turbine side are treated individually and divided into sections of inlet, wheel, outlet, diffuser and volute. The model demonstrates the capability to properly account for the impact of heat transfer and thereby improves the predictive accuracy of temperatures relevant for the matching process.
Enhancement of the Rotordynamic Performance of a Shaft Supported by Air Foil Bearings With Vibration Damper
Authors: Zamanian Yazdi Behzad , Kim Daejong , Xu Fangcheng
Published: September 2016

Air foil bearings (AFBs) have found many successful applications in small high-speed oil-free turbomachinery over the past decades. AFBs are made of a thin top foil serving as the bearing surface, and an underlying mechanical structure that provides structural support and damping. AFBs offer better rotor stability than the rigid-walled gas bearings because of the damping. However, improvements in the damping and the rotordynamic stability are still active areas of research in the AFBs. Researchers have suggested different solutions for improving the stability such as hydrodynamic preload, pressurized air injection, forced axial flow, different material structures, etc. This study investigates the effect of the added bump foil damper around the bearing sleeve on the rotordynamic performance of a rigid rotor (3.91 kg) supported by AFBs (49mm in diameter and 37.5mm in length). Simulation studies involve transient time-domain simulation of the rotor’s vibrational motion under the imbalance excitation with different sleeve masses and different stiffness of the bump foil damper. From the simulation results, the beneficial effect of the added bump foil damper on the rotordynamic performance of the rotor was observed. By reducing the stiffness of the damper, the stability increases and the onset speed of the subsynchronous vibration pushes to the higher speeds. Also, a heavier bearing sleeve reduces the magnitude of the vibration at the critical speed. Two radial AFBs with the damper around the bearing sleeve support the rotor. Two different bump foil dampers were manufactured using different material thicknesses, and two sets of bearing sleeves were made from different materials with identical geometries to investigate the effect of the bearing sleeve mass on the rotordynamic performance.
Design Parameters Exploration for Supercritical CO2 Centrifugal Compressors Under Multiple Constraints
Authors: Shao Wenyang , Wang Xiaofang , Yang Jinguang , Liu Huimin , Huang Zhenjun
Published: September 2016

The Supercritical Carbon Dioxide (SCO2) Brayton cycle has been getting more and more attentions all over the world in recent years for its high cycle efficiency and compact components. The compressor is one of the most important components in the cycle. Different from traditional working fluid, SCO2 has a risk of condensation at the impeller inlet because of the particular properties near the critical point. In order to determine the possibility of the condensation, a concept called “Condensation Margin (CM)” suited for SCO2 is introduced. It is associated with the total and saturated thermodynamic conditions. A design parameter called velocity ratio at the impeller inlet (IVR) is defined to control the state of working fluid at impeller inlet based on CM. In terms of different constraints and design requirements, such as impeller efficiency, operating range and processing technic, especially in small size cases, the design parameters at the impeller outlet are explored by establishing a function of outlet width, the number of blades, rotating speed, outlet tangential velocity coefficient and outlet meridional velocity coefficient. A preliminary design result of a low-flow-coefficient SCO2 centrifugal compressor is presented as an example of the application of the design parameters exploration results; then CFD simulation is performed, and consistent results are obtained compared with exploration results.
Cryogenic Turboexpanders in LNG Liquefaction Applications
Authors: Taher Matt , Meher-Homji Cyrus B.
Published: September 2016

Turboexpanders provide the most efficient solution when it is required to reduce the pressure of a fluid stream. By expanding high pressure fluid, energy in the high pressure fluid entering the turboexpander can be efficiently used for either driving a booster compressor or for electrical power generation. While the plants are designed to operate without the need for the power produced by turboexpander, the work recovered from the expansion is a bonus, which increases the plant thermal efficiency.

This paper is intended to explain the benefits of utilizing a turboexpander in LNG liquefaction applications. Also, in absence of a published API standard for a turboexpander-generator package, this paper provides recommendations on factory acceptance tests.
Experimental Investigation of Effusion Cooling Performance on the Liner of a Scaled Three Injector Annular Combustor
Authors: Ji Yongbin , Ge Bing , Zang Shusheng , Yu Jiangpeng , Zhang Ji
Published: September 2016

Gas turbine combustors design nowadays is aimed at achieving extremely lower NOx emissions through involving more air into the combustor to perform lean combustion, which results in the reduction of cooling air ratio for the liner walls. In this context, effusion cooling, one of the most effective cooling strategies, is adopted on the liner for its advantages of providing well cooling protection with limited amount of air. The swirl flow structure generated by the injector to stabilize flame in most modern lean-burn combustor is very complex with recirculation and vortex breakdown. So the interaction between three dimensional main flow and jets issued from the effusion holes is significant when assessing effusion cooling performance on the liner.

In the present work, detailed effusion cooling feature on both inner and outer liners of a scaled annular combustor equipped with three axial swirlers has been provided under non-reactive and reactive conditions. The main flow is electrically heated for the non-reactive condition, while premixed combustion is realized after methane is fueled into the injectors and mixed with the air in the surrounding passage for the reactive condition. Temperature distribution on the target bended plate with 7 rows of discrete cooling holes in an in-line layout is captured by infrared thermography, and the cooling effectiveness is then analyzed. Effects of coolant to mainstream flow rate ratio and equivalence ratio are evaluated respectively. Results show that the macro rotational flow generated by the swirl flows interacts with cooling film and leads to non-symmetric cooling protection circumferentially on both liners. Additionally, averaged cooling effectiveness is found to increase with the flow rate ratio. At reactive conditions, stagnation of the high temperature swirl flow impinging on the liner wall locates at X/D range of 0.4–0.5, which has not been observed at non-reactive conditions. Also cooling effectiveness results indicate that outer liner obtains better cooling protection than inner liner when reaction is activated. Finally, the effect of most interested parameter for combustion process equivalence ratio is surveyed at Φ=0.7, 0.8 and 0.9. With experimental results, the importance of the combustion is highlighted in weighing the effusion cooling performance on the real annular combustor liners, which can’t be predicted comprehensively by non-reactive investigations. To obtain more knowledge of this issue, future work concerned with the flow field and flame visualization needs to be done through experimental techniques and numerical methods.
Performance Analysis and Comparison Study of Transcritical Power Cycles Using CO2-Based Mixtures as Working Fluids
Authors: Xia Jiaxi , Wang Jiangfeng , Zhao Pan , Yiping Dai
Published: September 2016

CO2 in a transcritical CO2 cycle can not easily be condensed due to its low critical temperature (304.15K). In order to increase the critical temperature of working fluid, an effective method is to blend CO2 with other refrigerants to achieve a higher critical temperature. In this study, a transcritical power cycle using CO2-based mixtures which blend CO2 with other refrigerants as working fluids is investigated under heat source. Mathematical models are established to simulate the transcritical power cycle using different CO2-based mixtures under MATLAB® software environment. A parametric analysis is conducted under steady-state conditions for different CO2-based mixtures. In addition, a parametric optimization is carried out to obtain the optimal design parameters, and the comparisons of the transcritical power cycle using different CO2-based mixtures and pure CO2 are conducted. The results show that a raise in critical temperature can be achieved by using CO2-based mixtures, and CO2-based mixtures with R32 and R22 can also obtain better thermodynamic performance than pure CO2 in transcritical power cycle. What’s more, the condenser area needed by CO2-based mixture is smaller than pure CO2.
A Study of S-CO2 Power Cycle for Waste Heat Recovery Using Isothermal Compressor
Authors: Heo Jin Young , Ahn Yoonhan , Lee Jeong Ik
Published: September 2016

As the demand to develop more efficient energy systems increases, ways to generate power from waste heat are under investigation. The supercritical carbon dioxide recovery cycle (S-CO2 cycle) has been considered a viable candidate as a bottoming cycle for “waste heat to power” (WHP) applications, such as the utilization of gas turbine outlet heat.

One major limitation to the system is that the S-CO2 cycle operates at a low expansion ratio, which leads to a higher turbine outlet temperature. This waste heat should be recuperated in order for the overall cycle efficiency to increase. Such limitation leads to a larger recuperator, higher volume flow rate, lower temperature gradient at the heater, and more complex cycle layouts for WHP applications. These constraints ultimately lead to the increase of hardware costs, which can degrade economics of the system.

To solve the existing problems regarding the use of S-CO2 cycle for WHP applications, the possibility of using an isothermal compressor in place of a conventional compressor in a simple Brayton cycle is investigated. This solution, named the iso-Brayton cycle, though the compressor technology is still under development, seems promising because it does not require an additional heat exchanger as one of the cycle components. Furthermore, the compressing work is minimized during an isothermal compression process.

To analyze the cycle performance of the iso-Brayton cycle, it is compared with a reference cycle, the simple recuperated Brayton cycle. The parameters of cycle net efficiency and cycle net work (or net usable work) are calculated using the KAIST-CCD in-house code.
Measurements and Modelling of Ingress in a New 1.5-Stage Turbine Research Facility
Authors: Patinios Marios , Scobie James A. , Sangan Carl M. , Owen J. Michael , Lock Gary D.
Published: September 2016

In gas turbines, hot mainstream flow can be ingested into the wheel-space formed between stator and rotor discs as a result of the circumferential pressure asymmetry in the annulus; this ingress can significantly affect the operating life, performance and integrity of highly-stressed, vulnerable engine components. Rim seals, fitted at the periphery of the discs, are used to minimise ingress and therefore reduce the amount of purge flow required to seal the wheel-space and cool the discs.

This paper presents experimental results from a new 1.5-stage test facility designed to investigate ingress into the wheel-spaces upstream and downstream of a rotor disc. The fluid-dynamically-scaled rig operates at incompressible flow conditions, far removed from the harsh environment of the engine which is not conducive to experimental measurements. The test facility features interchangeable rim-seal components, offering significant flexibility and expediency in terms of data collection over a wide range of sealing-flow rates. The rig was specifically designed to enable an efficient method of ranking and quantifying the performance of generic and engine-specific seal geometries.

The radial variation of CO2 gas concentration, pressure and swirl is measured to explore, for the first time, the flow structure in both the upstream and downstream wheel-spaces. The measurements show that the concentration in the core is equal to that on the stator walls and that both distributions are virtually invariant with radius. These measurements confirm that mixing between ingress and egress is essentially complete immediately after the ingested fluid enters the wheel-space and that the fluid from the boundary-layer on the stator is the source of that in the core. The swirl in the core is shown to determine the radial distribution of pressure in the wheel-space.

The performance of a double radial-clearance seal is evaluated in terms of the variation of effectiveness with sealing flow rate for both the upstream and the downstream wheel-spaces and is found to be independent of rotational Reynolds number. A simple theoretical orifice model was fitted to the experimental data showing good agreement between theory and experiment for all cases. This observation is of great significance as it demonstrates that the theoretical model can accurately predict ingress even when it is driven by the complex unsteady pressure field in the annulus upstream and downstream of the rotor. The combination of the theoretical model and the new test rig with its flexibility and capability for detailed measurements provides a powerful tool for the engine rim-seal designer.