bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Method for Rotordynamic Force Prediction of a Centrifugal Compressor Impeller Front Cavity Using a Transient Whirling CFD Technique
Authors: Hoopes Kevin , Moore J. Jeffrey , Rimpel Aaron , Kulhanek Chris , Venkataraman Balaji 
Published: November 2019

Abstract
In order to improve the rotordynamic stability predictions of centrifugal compressor impeller front cavities, a method for modeling the eye seal and shroud cavity using transient, moving wall, CFD simulation is presented. This method allows for the extraction of the rotordynamic coefficients from the eye seal and impeller front cavity using a single model. This paper presents the details of the method as well as a set of typical results at various different whirling frequencies for a centrifugal impeller front cavity. Along with the CFD derived rotordynamic coefficients, predictions using correlations from the literature are also presented for comparison.
Effect of Microporosity on Damage Initiation in Ceramic Matrix Composites
Authors: Gururaja Suhasini , Nagaraja Abhilash 
Published: November 2019

Abstract
Ceramic matrix composites (CMC) are a subclass of composite materials consisting of reinforced ceramics. They retain the advantages of ceramics such as lower density and better refractory properties but exhibit better damage tolerance compared to monolithic ceramics. This combination of properties make CMCs an ideal candidate for use in high temperature sections of gas turbines. However, modeling the damage mechanisms in CMCs is complex due to the heterogeneous microstructure and the presence of processing induced defects such as matrix porosity. The effect of matrix pore location and orientation on damage initiation in CMCs is of interest in the present work.
CMCs fabricated by various fabrication processes exhibit matrix pores at different length scales. Microporosities exist within fiber bundles in CMCs have a significant effect on microscale damage initiation and forms the focus of the current study. In a previous work by the authors, a two step numerical homogenization approach has been developed to model statistical distribution of matrix pores and to obtain the effective mechanical properties of CMCs in the presence of matrix porosity. A variation of that approach has been adopted to model matrix pores and investigate the severity of pores with respect to their location and orientation. CMC microstructure at the microscale has been modeled as a repeating unit cell (RUC) consisting of fiber, interphase and matrix. Ellipsoidal pores are modeled in the matrix with pore distance from the interphase-matrix interface and pore orientation with respect to the loading direction as parameters. Periodic boundary conditions (PBCs) are specified on the RUC by means of constraint equations. The effect of the pore on the local stress fields and its contribution to matrix damage is studied.
The STEP 10 MWe sCO2 Pilot Plant Demonstration
Authors: Marion John , Kutin Mike , McClung Aaron , Mortzheim Jason , Ames Robin 
Published: November 2019

Abstract
A team led by Gas Technology Institute (GTI), Southwest Research Institute® (SwRI®) and General Electric Global Research (GE-GR), along with the University of Wisconsin and Natural Resources Canada (NRCan), is actively executing a project called “STEP” [Supercritical Transformational Electric Power project], to design, construct, commission, and operate an integrated and reconfigurable 10 MWe sCO2 [supercritical CO2] Pilot Plant Test Facility located at SwRI’s San Antonio, Texas campus. The $119 million project is funded $84 million by the US DOE’s National Energy Technology Laboratory (NETL Award Number DE-FE0028979) and $35 million cost share by the team, component suppliers and others interested in sCO2 technology. This project is a significant step toward sCO2 cycle based power generation commercialization and will inform the performance, operability, and scale-up to commercial facilities.
Supercritical CO2 (sCO2) power cycles are Brayton cycles that utilize supercritical CO2 working fluid to convert heat into power. They offer the potential for higher system efficiencies than other energy conversion technologies such as steam Rankine or organic Rankine cycles, especially when operating at elevated temperatures. sCO2 power cycles are being considered for a wide range of applications including fossil-fired systems, waste heat recovery, concentrated solar power, and nuclear.
The pilot plant design, procurement, fabrication, and construction are ongoing at the time of this publication. By the end of this 6-year project, the operability of the sCO2 power cycle will be demonstrated and documented starting with facility commissioning as a simple closed recuperated cycle configuration initially operating at a 500°C (932°F) turbine inlet temperature and progressing to a recompression closed Brayton cycle technology (RCBC) configuration operating at 715°C (1319 °F).
3D Heat Transfer Assessment of Full-Scale Inlet Vanes With Surface-Optimized Film Cooling: Part 1 — Experimental Results
Authors: Anthony R. J. , Clark J. P. , Finnegan J. , Johnson J. J. 
Published: November 2019

Abstract
Full-scale annular experimental evaluation of two different high pressure turbine first stage vane cooling designs was carried out using high frequency surface heat-flux measurements in the Turbine Research Facility at the Air Force Research Laboratory. A baseline film cooling geometry was tested simultaneously with a genetically optimized vane aimed to improve efficiency and part life. Part 1 of this two-part paper describes the experimental instrumentation, test facility, and surface heat flux measurements used to evaluate both cooling schemes. Part 2 of this paper describes the result of companion conjugate heat transfer posttest predictions, and gives numerical background on the design and modelling of both film cooling geometries.
Time-resolved surface heat flux data is captured at multiple airfoil span and chord locations for each cooling design. Area based assessment of surface flux data verifies the genetic optimization redistributes excessive cooling away from midspan areas to improve efficiency. Results further reveal key discrepancies between design intent and real hardware behavior. Elevated heat flux above intent in some areas led to investigation of backflow margin and unsteady hot gas ingestion at certain film holes. Analysis shows areas toward the vane inner and outer endwalls of the aft pressure side were more sensitive to reduced aft cavity backflow margin. In addition, temporal analysis shows film cooled heat flux having large high frequency fluctuations that can vary across nearly the full range of film cooling effectiveness at some locations. Velocity and acceleration of these large unsteady heat flux events moving near the endwall of the vane pressure side is reported for the first time. The temporal nature of the unsteady 3-D film cooling features are a large factor in determining average local heat flux levels. This study determined this effect to be particularly important in areas on real hardware along the HPT vane pressure side endwalls towards the trailing edge, where numerical assumptions are often challenged. Better understanding of the physics of the highly unsteady 3D film cooled flow features occurring in real hardware is necessary to accurately predict distress progression in localized areas, prevent unforeseen part failures, and enable improvements to turbine engine efficiency. The results of this two-part paper are relevant to engines in extended service today.
The Role of Mean Flame Anchoring on the Stability Characteristics of Syngas, Synthesis Natural Gas, and Hydrogen Fuels in a Turbulent Non-Premixed Bluff-Body Combustor
Authors: Baraiya Nikhil Ashokbhai , Chakravarthy Satynarayanan R. 
Published: November 2019

Abstract
A lab-scale bluff body combustor is mapped for its stability and flame dynamics of non-premixed flames. The characteristics are observed across variations in the fuel composition, as well as in the inlet flow rate. The combustor is seen to exhibit markedly different dynamics for each of the varied fuel compositions. This behavior is explained on the basis of mean flame stabilization behavior and on the combined effects of the fuel-jet momentum flux and global equivalence ratio. It is seen that the H2 flames primarily act as a pilot source for secondary combustion of either CO or CH4. Further, it is seen that, the high momentum flux associated with H2-CO mixtures result in combustion near the wall and outside the bluff-body shear layers at low inlet flow rates. Whereas, at high inlet flow rates, the mean heat release rate is seen to stabilize closer to the injection holes as well as extend to near the bluff-body shear layer. This marked difference in flame stabilization is seen to have a drastic effect on the nature of oscillations inside the chamber. This is contrasted to H2-CH4 (synthesis natural gas) flames that exhibit stabilization inside the bluff-body wake at high inlet flow rate. The difference between H2-CH4 and H2-CO flames with regards to combustion dynamics is then explained as a result of the flame stabilization behavior, which is seen to be different across the varied fuel compositions. While H2-CH4 flame exhibits the well-known large wake structures responsible for combustion instability, H2-CO flame exhibits no such structures, owing to their stabilization point. Further analysis using pressure fixed phase instants reveal the difference in nature of combustion dynamics across the tested fuel compositions and are justified using the spatial Rayleigh index map.
Investigation on Effect of Inlet Flow Turbulence on the Combustion Instability Using Simultaneous PIV and CH* Chemiluminescence in a Backward Facing Step Combustor
Authors: Pancharia Pankaj , Ramanan Vikram , Nagarajan Baladandayuthapani , Chakravarthy S. R. 
Published: November 2019

Abstract
The present study investigates the role of inlet turbulence intensity on the stability characteristics of a lab scale backward facing step combustor (BFS). Turbulence generator placed upstream of the flame holder is used to vary the turbulence levels. The present study utilizes simultaneous chemiluminescence, particle image velocimetry (PIV) and unsteady pressure fluctuation measurement are done in a time-resolved manner to study the role of inlet turbulence intensity on the flame-flow dynamics and identify different modes of combustion instability as a result of the same. The bifurcation plot with airflow rate, in terms of step-based Reynolds number (Re) as the control parameter, indicates a counterintuitive picture, whereby higher turbulence intensity postpones the onset of instability. The finding has been reported in the past by Nagarajan et. al [30], with the present work extending it. It is shown that the flow-flame structures at high (∼1000 Pa) and very high (>4000 Pa), conditions, the dynamics are significantly different across the same turbulence intensity at different equivalence ratio as well as at different turbulence intensities for the same equivalence ratio. Analysis of the flame-flow dynamics reveals the role of the extent of vortex initiated by acoustics and its orientation in forming an unsteady loop, whereby the vortex span and strength aids the flame to propagate upstream of the step, and the flame in-turn being responsible to sustain the large-scale vortex. This phenomenon is distinct from the conventional vortex sustained combustion instability, whereby the vortex is of the lower span and does not influence the upstream flow. The role of inlet turbulence intensity is seen to be more pronounced in the extent of the flame propagating upward, which then completes the fore-mentioned loop.
Development of a Gas Turbine Concept for Electric Power Generation in a Commercial Hybrid Electric Aircraft
Authors: Schneider Michael , Dickhoff Jens , Kusterer Karsten , Visser Wilfried , Stumpf Eike , Hofmann Jan-Philipp , Bohn Dieter 
Published: November 2019

Abstract
Civil aviation is growing 4.7% per annum. Alternative propulsion systems are necessary to reduce emissions causing global warming. The electrification of aircraft propulsion systems has the potential to use renewable energy and reduce the environmental footprint of aviation.
At present, full electric flight appears to be feasible for small aircraft only, due to the power density of batteries which is approximately 45-times lower than that of kerosene. Hybrid electric concepts may present a bridging technology towards more electrified aviation for short/mid-range aircraft. The hybrid concept combines the benefits of electrical power with conventional turboshaft engine technology.
Within the framework of the ‘HyFly’ project (supported by the German Luftfahrtforschungsprogramm LuFo V-3), a hybrid electric concept for a short/mid-range 19 PAX aircraft is studied. In this paper the results of a preliminary design exercise of the gas turbine used in this concept is presented.
Conventional aircraft gas turbines deliver maximum power only at take-off for a short period of time. At this power setting temperature and stress levels are at the extreme and dominate overall engine life consumption. In the HyFly concept, the gas turbine inlet temperature is kept constant during the entire flight. The engine is not driven into the extreme take-off power setting, resulting in a significant increase of engine life. The constant power setting also offers the opportunity to optimize efficiency especially around the base load point. For take-off and an emergency power rating, extra power is provided by batteries.
In this paper, a survey of existing engine technology is presented considering suitability for the concept. The impact of improvement of component efficiencies, increase in cycle pressure ratio and turbine inlet temperature, relative to the state-of-the-art, is analyzed using a B&B-AGEMA in-house gas turbine simulation tool. In addition, a weight model is presented for preliminary estimation of engine mass. Finally, requirements for the individual gas turbine sub-component design and performance are defined. This will build the basis for further component design.
CO Time-Histories During Oxy-Methane Combustion in a CO2 Environment
Authors: Pryor Owen M. , Ninnemann Erik , Vasu Subith 
Published: November 2019

Abstract
Carbon monoxide time-histories and ignition delay times were measured in carbon dioxide diluted methane mixtures behind reflected shockwaves. Experiments were performed around 2 atm for a temperature range between 1650–2000 K. The experiments were performed for a mixture of XCH4 = 0.5%, XO2 = 1.0%, XCO2 = 8.5%, XAr = 90.0%. The mixture was chosen to minimize energy release during the experiment and a minimum of 2 ms was recorded for all experiments. The carbon monoxide time-histories were measured using a tunable diode laser absorption spectroscopy technique and measuring the absorbance at two different wavelengths to isolate the impact of carbon monoxide on the absorbance. Carbon monoxide was measured at a wavelength of 4886.94 nm while the interfering species was measured at 4891.17 nm. Each experiment was performed twice, with the pressure and temperature before combustion being matched to within the experimental uncertainty of the two experiments. The ignition delay times were measured using OH* radical emission to determine the time-scales of the experiments. All experiments were compared to detailed chemical kinetic mechanisms that can be found in the literature. The experimental results show that the detailed mechanisms from the literature were able to accurately predict the general profile of the carbon monoxide time-histories but under-predicted maximum concentration of CO being formed at these conditions.
Telehealth spirometry for children with cystic fibrosis
Authors: Logie Karla , Welsh Liam , Ranganathan Sarath C 
Published: November 2019

AimWe assessed the feasibility of telehealth spirometry assessments for children with cystic fibrosis (CF) living in a regional setting.MethodPatients with acceptable computer hardware at home were provided with a SpiroUSB (Vyaire) spirometer. Spirometry was performed during ‘home admissions’ or for ongoing home monitoring in children living outside metropolitan Melbourne. At the end of the session, the family forwarded the data to the Royal Children’s Hospital, Melbourne.ResultsTwenty-two patients aged 7 to 17 years participated, with spirometry successful in 55 of 59 (93%) attempted sessions according to American Thoracic Society/European Respiratory Society criteria. The median distance between the subject’s home and the hospital was 238 km (range 62–537 km) which equated to a travel time saving of 5 hours and 34 min per hospital visit.ConclusionHome-based telehealth spirometry is feasible in children with CF and can support the CF team during home-based admissions and for ongoing outpatient monitoring.
Association of macular disease with long-term use of pentosan polysulfate sodium: findings from a US cohort
Authors: Jain Nieraj , Li Alexa L , Yu Yinxi , VanderBeek Brian L 
Published: November 2019

Background/AimsA series at a single clinical centre recently demonstrated an association between the interstitial cystitis drug pentosan polysulfate sodium (PPS) and a vision-threatening pigmentary maculopathy. The aim of this study was to determine if an association exists between PPS use and macular disease in a large national cohort.MethodsA retrospective, matched cohort study using data from a large US medical claims database from 2002 to 2016 was performed. A total of 3012 and 1604 PPS users were compared with 15 060 and 8017 matched controls at 5 and 7 years, respectively. The primary outcome measures included (1) any new diagnosis of a hereditary or secondary pigmentary maculopathy (atypical maculopathy outcome), and (2) any new diagnosis of dry age-related macular degeneration (AMD) or drusen in addition to the aforementioned diagnoses (atypical maculopathy+AMD outcome).ResultsAt the 5-year and 7-year follow-up, 9 (0.3%) and 10 (0.6%) PPS patients progressed to the atypical maculopathy outcome compared with 32 (0.2%) and 25 (0.3%) control patients, respectively. 103 (3.4%) and 87 (5.4%) PPS patients developed the atypical maculopathy+AMD outcome compared with 440 (2.9%) and 328 (4.1%) control patients at 5 and 7 years, respectively. At 5 years, multivariate analysis showed no significant association (p>0.13). At 7 years, PPS users had significantly increased odds of having the atypical maculopathy+AMD outcome (OR=1.41, 95% CI 1.09 to 1.83, p=0.009).ConclusionsPPS exposure was associated with a new diagnosis of macular disease at the 7-year follow-up in a large national cohort.
Geospatial assessment of the voluntary medical male circumcision programme in Tanzania, 2011–2016
Authors: Kim Hana , Branscum Adam , Miller F DeWolfe , Cuadros Diego F 
Published: November 2019

IntroductionTanzania is one of the 14 priority countries in sub-Saharan Africa scaling up voluntary medical male circumcision (VMMC) for HIV prevention. In this study, we assessed the progress of VMMC by evaluating changes in the spatial structure of male circumcision (MC) prevalence and identifying age groups with low MC uptake.MethodsWe use data from two waves of the Demographic and Health Survey (DHS) conducted in Tanzania in 2011–2012 and 2015–2016. MC incidence rate was estimated using a method developed to calculate incidence rates from two successive cross-sectional surveys. Continuous surface maps of MC prevalence were generated for both DHS waves and compared with identified areas with high MC prevalence changes and high density of uncircumcised males.ResultsNational MC prevalence in Tanzania increased from 73.5% in 2011–2012 to 80.0% in 2015–2016. The estimated national MC incidence rate was 4.6 circumcisions per 100 person-years (py). The lowest circumcision rate was observed in males aged 20–24 years, with 0.61 circumcisions per 100 py. An estimated 1 567 253 males aged 15–49 years residing in low-MC prevalence areas were uncircumcised in 2015–2016.ConclusionTanzania has shown substantial progress in the implementation of VMMC. However, extensive spatial variation of MC prevalence still exists in the country, with some areas having an MC prevalence <60%. Here, we identified locations where VMMC needs to be intensified to reach the ~1.5 million uncircumcised males age 15–49 living in these low-MC areas, particularly for men aged 20–34.
Keep the fire burning: a survey study on the role of personal resources for work engagement and burnout in medical residents and specialists in the Netherlands
Authors: Solms Lara , van Vianen Annelies E M , Theeboom Tim , Koen Jessie , de Pagter Anne P J , de Hoog Matthijs 
Published: November 2019

ObjectivesThe high prevalence of burnout among medical residents and specialists raises concerns about the stressful demands in healthcare. This study investigated which job demands and job resources and personal resources are associated with work engagement and burnout and whether the effects of these demands and resources differ for medical residents and specialists.DesignIn a survey study among residents and specialists, we assessed job demands, job resources, personal resources, work engagement and burnout symptoms using validated questionnaires (January to December 2017). Results were analysed using multivariate generalised linear model, ordinary least squares regression analyses and path analyses.SettingFive academic and general hospitals in the Netherlands.ParticipantsA total number of 124 residents and 69 specialists participated in this study. Participants worked in the fields of pediatrics, internal medicine and neurology.ResultsThe associations of job and personal resources with burnout and work engagement differed for residents and specialists. Psychological capital was associated with burnout only for specialists (b=−0.58, p<0.001), whereas psychological flexibility was associated with burnout only for residents (b=−0.31, p<0.001). Colleague support (b=0.49, p<0.001) and self-compassion (b=−0.33, p=0.004) were associated with work engagement only for specialists.ConclusionThis study suggests that particularly personal resources safeguard the work engagement and lessen the risk of burnout of residents and specialists. Both residents and specialists benefit from psychological capital to maintain optimal functioning. In addition, residents benefit from psychological flexibility, while specialists benefit from colleague support. Personal resources seem important protective factors for physicians’ work engagement and well-being. When promoting physician well-being, a one-size-fits-all approach might not be effective but, instead, interventions should be tailored to the specific needs of specialists and residents.