bluuebunny/crossref_metadata_2025 huggingface dataset:
Learning From Successful School‐Based Vaccination Clinics During 2009 pH1N1
Authors: Klaiman Tamar , O'Connell Katherine , Stoto Michael A.
Published: December 2013

BACKGROUND

The 2009 H1N1 vaccination campaign was the largest in US history. State health departments received vaccines from the federal government and sent them to local health departments (LHDs) who were responsible for getting vaccines to the public. Many LHD's used school‐based clinics to ensure children were the first to receive limited vaccine supplies, but the success of school‐based distribution strategies varied in different locations. The goal of this project was to identify and learn from high‐performing school‐based vaccination clinics in order to share successes and improve performance in future school‐based vaccination campaigns.

METHODS

We used a combination of process mapping and comparative analysis to identify and derive lessons from positive outlier cases observed during 2009 H1N1 school‐based vaccination clinic implementation. We created process maps to identify the activities of LHDs conducting school‐based vaccinations and used them as the basis for in‐depth interviews of LHD staff. We asked interviewees to describe their activities during the 2009 H1N1 pandemic (pH1N1) school‐based vaccination campaign with a focus on successful processes.

RESULTS

We identified positive deviants, that is, those that performed better than expected, and categorized qualitative data from in‐depth interviews with 13 successful LHDs according to the process maps. Key mechanisms for school‐based vaccination success included having a relationship with local school authorities, communicating effectively with parents, and ensuring clinic logistics allowed for an easy flow of students through the vaccination process.

CONCLUSIONS

Utilizing rigorous methodology, we defined and learned lessons from successful LHDs when conducting school‐based vaccination clinics, which can be applied to future school‐based vaccination campaigns.
Benefits and Quality of Life Outcomes From Transportation Voucher Use by Adults With Disabilities
Authors: Samuel Preethy S. , Lacey Krim K. , Giertz Chesley , Hobden Karen L. , LeRoy Barbara W.
Published: December 2013

People with disabilities often feel isolated from their communities, which in turn affects their emotional well‐being and their overall quality of life. Access to transportation is a substantial barrier to community participation and an improved quality of life for individuals with disabilities. Transportation voucher programs represent a cost‐effective way to provide access to transportation for people with disabilities, but few studies have empirically examined the effectiveness of such programs. The present study examined the perceived benefits of participating in a transportation voucher program in Michigan, a midwestern state in the United States with limited public transportation. Cross‐sectional survey data collected from a convenience sample of 73 participants of the transportation voucher program, funded by the state's Developmental Disabilities Council from 2005 to 2008, were analyzed. Participation outcomes were differentiated by age, sex, employment status, and type of disability using multivariate logistic regression analysis. More than two‐thirds (70%) of participants reported that their emotional well‐being and community participation had improved, and 54% of participants indicated that participation in the voucher program had resulted in better overall quality of life. The type of disability was an important factor in determining the degree of gain experienced, particularly in terms of community participation and overall quality of life. Findings suggest that resources spent on developing voucher programs have the potential to enrich the lives of persons with disabilities and their families. However, future longitudinal research along with a comparison group may be necessary to validate these preliminary findings on the benefits of vouchers.
Oral infestation with leech Limnatis nilotica in two mixed‐breed dogs
Authors: Rajaei S. M. , Khorram H. , Ansari Mood M. , Mashhadi Rafie S. , Williams D. L.
Published: December 2013

Leeches are bloodsucking hermaphroditic parasites that attach to tissues using two muscular suckers, ingest large amounts of blood and may cause severe anaemia in the host. Two four‐month‐old mixed‐breed dogs (one bitch and one male) were referred with anorexia, retching, hypersalivation and bleeding from the oral cavity. On physical examination, two live leeches were detected on the ventral aspect of the tongue of the bitch and one in a similar position in the male. The leeches were gently detached and removed using Adson tissue forceps after applying vinegar over the area. Microcytic hypochromic anaemia was detected in the bitch and mild leukocytosis in the dog. One month after treatment both animals were re‐examined and a complete blood count was normal. Given that infestation with leeches as described here is associated with contaminated water, the use of clean and safe drinking water is recommended to avoid such diseases.
Role of chronic stress and depression in periodontal diseases
Authors: Warren Kimberly R. , Postolache Teodor T. , Groer Maureen E. , Pinjari Omar , Kelly Deanna L. , Reynolds Mark A.
Published: December 2013

An extensive body of experimental and clinical evidence documents the negative impact of chronic psychological stress and depression on the immune system and health. Chronic stress and depression can result in general dysregulation of the immune system, of both cellular and humoral pathways, which may contribute to pathogenic infection and concomitant periodontal tissue destruction. In general, the evidence is consistent with the hypothesis that stress can modify the host defense and progression of periodontal infections in patients susceptible to periodontitis. However, substantial evidence also indicates that these conditions can mediate risk for disease, including periodontitis, through changes in health‐related behaviors, such as oral hygiene, smoking and diet. The unequivocal interpretation of studies has also been hampered, in part, by issues related to conceptualization of stress and depression, as well as commonly associated comorbidities, such as diabetes, that can modify the onset and progression of periodontal disease. In addition, stress and depression appear to fall into a spectrum, ranging from mild to severe, involving a complex interaction of genetic background, coping strategies and environment. Differences in the conceptualization of stress and depression are probably important in assessing associations with other biologic and clinical measures. Future studies are necessary to clarify the complex interactions of chronic stress and depression in periodontal diseases.
Rab7 Is Functionally Required for Selective Cargo Sorting at the Early Endosome
Authors: Girard Emmanuelle , Chmiest Daniela , Fournier Natalie , Johannes Ludger , Paul Jean‐Louis , Vedie Benoît , Lamaze Christophe
Published: December 2013

The small GTPases of the Rab family act as a molecular switch regulating various aspects of membrane trafficking through the selective recruitment of effector proteins. Whereas Rab7 has been classically involved in the regulation of transport within the endolysosomal network, persistent controversy remains as to whether Rab7 also plays a role in earlier steps of endosomal trafficking. In this study, we show that Rab7 depletion or inactivation results in enlargement of both early and late endosomes. Rab7 depletion led to the retention of a significant fraction of internalized low‐density lipoproteins (LDL) mainly in enlarged early endosomes (EE). As a result, LDL processing and the transcriptional regulation of sterol‐sensitive genes were impaired. We found that Rab7 activity was also required for the sorting of the mannose‐6‐phosphate receptor, the interferon alpha‐receptor and the Shiga toxin B‐subunit. In contrast, epidermal growth factor (EGF) sorting at the EE or the recycling of transferrin and LDL‐R were not affected by Rab7 depletion. Our findings demonstrate that in addition to regulating late endosomes (LE) to lysosomes transport, Rab7 plays a functional role in the selective sorting of distinct cargos at the EE and that the Rab5 to Rab7 exchange occurs early in the endosomal maturation process.
Growth factor and proteinase profile of Vivostat® platelet‐rich fibrin linked to tissue repair
Authors: Ågren M. S. , Rasmussen K. , Pakkenberg B. , Jørgensen B.
Published: December 2013

Background and Objectives

Autologous platelet‐rich fibrin (PRF®) is prepared by the automatic Vivostat® system. Conflicting results with Vivostat PRF in acute wound healing prompted us to examine its cellular and biomolecular composition. Specifically, platelets, selected growth factors and matrix metalloproteinase (MMP)‐9 were quantified using novel analytical methods.

Materials and Methods

Ten healthy non‐thrombocytopenic volunteers donated blood for generation of intermediate fibrin‐I and final PRF. Anticoagulated whole blood and serum procured in parallel served as baseline controls. Leucocyte, erythrocyte and platelet counts in whole blood and fibrin‐I were determined by automated haematology analyser. Platelet concentration in PRF was quantified manually by stereologic analysis of Giemsa‐stained tissue sections, and the total content of five growth factors and MMP‐9 by enzyme‐linked immunosorbent assays.

Results

The number of leucocytes and erythrocytes was reduced (P < 0·001), whereas platelets increased (P < 0·001) in fibrin‐I versus whole blood. PRF contained 982 ± 206 × 109 platelets/l representing 3·9‐fold (P < 0·001) enrichment relative to whole blood. Growth factor abundance in Vivostat PRF and serum was in descending order: transforming growth factor‐β1 [5·1‐fold higher in PRF than serum, P < 0·001] > platelet‐derived growth factor (PDGF)‐AB [2·5‐fold, P < 0·01] > PDGF‐BB [1·6‐fold, P < 0·05] > vascular endothelial growth factor > basic fibroblast growth factor [75‐fold, P < 0·001]. MMP‐9 was reduced 139‐fold (P < 0·001) compared with serum, reflecting leucocyte depletion in PRF.

Conclusion

The gained knowledge on platelet enrichment and biomolecular constituents may guide clinicians in their optimal use of Vivostat PRF for tissue regenerative applications.
Bispectrum: A Tool for Distinguishing Different Faults in Rotating Machine
Authors: Elbhbah Keri , Sinha Jyoti K.
Published: December 2013

The current state-of-the-art in vibration-based condition monitoring of rotating machines requires a number of vibration transducers at each bearing pedestal of a rotating machine to identify any faults, in the machine. In this paper, the use of the bispectrum has been proposed for fault diagnosis in rotating machines. The reason for this is that it may reduce the number of vibration transducers at each bearing pedestal in rotating machines in the future. The paper presents a comparison of the bispectrum results for four cases, namely; Healthy, Misaligned shaft, Crack Shaft and Shaft Rub on an experimental rig consisting of two rigidly coupled shafts supported through 4 ball bearings. Only one accelerometer has been used for this purpose at each bearing and the initial results observed are encouraging.
Auxiliary Turbine Generator Set Isolation System Design for US Naval Vessel
Authors: Jones Paul G. , Carmichael Steven L.
Published: December 2013

The RR4500 Auxiliary Turbine Generator (ATG) incorporates an isolation system addressing four main design requirement environments. These environments include high-impact shock, structureborne vibration, sea state motion, and installation/integration into the machinery space. Multiple design iterations were performed, beginning with a simplified system representation and expanding to full system finite element models. Specific resilient isolation mounts were selected to satisfy the competing criteria from the different requirement sets. Design resolutions passed specific requirements down to the component level and were addressed during detail design. Structures, system components, and flexible ship connections were adapted to meet the requirements needed by the isolation system. Testing of the system indicates good correlation between system predictions and actual performance.
Detailed Modeling of Parabolic Trough Collectors for the Part Load Simulation of Solar Thermal Power Plants
Authors: Zaversky F. , Bergmann S. , Sanz W.
Published: December 2013

Solar thermal power plants are a promising way of providing clean renewable electric energy. These plants concentrate the incoming solar direct irradiation in order to heat up a heat transfer fluid. The collected thermal energy can be stored or instantly delivered to a power block where part of the thermal energy is converted to electrical energy in a turbine with the connected generator.

The parabolic trough collector plant is the today’s most developed solar thermal power plant type. There the solar irradiation is focused on receiver tubes which are concentrically placed to the focal lines of the parabolic trough collectors. A high temperature oil is pumped through these receiver tubes, which collects the heat and delivers it later on to the steam generator of the connected Rankine steam cycle. In order to improve the efficiency of these solar thermal power plants, the direct steam generation (DSG) within the parabolic trough collector receiver tubes is being investigated.

Both types of parabolic trough collectors, the conventional type using oil as heat transfer fluid and the direct steam generation type, are subject of this paper. A detailed steady-state parabolic trough collector model was developed for each type, using the thermodynamic simulation software IPSEpro. The developed models consider the cosine-loss attenuation factor, the shading attenuation factor, optical losses, as well as thermal losses. Appropriate heat transfer and pressure loss correlations were implemented for both collector types. For the direct steam generation model, distinct collectors for the preheating section, the evaporation section and the superheating section were used. Furthermore, the suitable length of discretization for the modeling of one collector loop within a center-fed solar field was investigated. Calculated solar field performance data for the oil concept were compared to validated data available in open literature. Finally, a power plant simulation with each collector type, over the course of one reference day, showed the great potential of the direct steam generation, as well as the suitability of IPSEpro for running solar thermal power plant yield simulations.
Handling Wind Variability Using Gas Turbines
Authors: Branchini L. , Perez-Blanco H.
Published: December 2013

A significant amount of energy is expected to come from wind in the upcoming years. The variability and uncertainty of this power source needs to be managed by the grid operator. Electricity networks with wind energy need extra reserves to deal with the extra uncertainty associated with the presence of wind. This paper evaluates the possibility to couple a 1000 MW wind farm with gas turbines (GTs) to provide firm capacity to the grid with a reasonable investment. Taking into account two different days of wind production with one minute data, the study analyzes the possibility of integrating the wind power output with two different types of GTs (heavy duty and aeroderivative). GTs operational constrains are included in the model in order to correctly demonstrate how the wind variability stresses turbine performance, as it probably would in extreme cases. Limitations on GTs ramps rates and start–up time are considered for both, heavy duty and aeroderivatives. GTs power output profiles, ramp rates and fuel consumption for the selected days of analysis are shown. The results show that the integration between wind and gas turbines could be a viable solution to compensate wind variability and to accommodate the increasing wind penetration into the electrical grid.
Arbitrary Surface Flank Milling and Flank SAM in the Design and Manufacturing of Jet Engine Fan and Compressor Airfoils
Authors: Wu Chung Y.
Published: December 2013

A pragmatic and versatile airfoil design and fabrication system, named the Arbitrary Surface Flank Milling (ASFM) system, has been continuously developed and applied to the design and manufacturing of fan and axial compressor airfoils — in the form of integrally bladed rotors (IBR) and centrifugal impeller blades — for jet engines at Pratt & Whitney over the past 28 years. In a previous paper 18 years ago, we gave an account of the general concept and methodology of the system, illustrated with a number of actual production engine applications. We have since then greatly expanded the domain of applicability of the system to successfully handle blades of unusual geometric complexity. We have made strides in the area of design for flank mill-ability with conventional cutters, and cutters shaped according to blade geometry. Based on the same concept and software methodology, we have also successfully demonstrated the superior quality and cost effectiveness of Flank Super Abrasive Machining (Flank SAM) of blades in nickel-based alloy IBRs.
On Two-Plane Balancing of Symmetric Rotors
Authors: Yu John J.
Published: December 2013

When rotor balancing is performed in the field, minimum trial weight runs would significantly reduce the downtime in power generation and oil-gas industries. Typically two trial weight runs would be required in order to obtain both static and couple influence coefficients. The current paper demonstrates how both static and couple influence coefficients can be evaluated with high accuracy through merely one trial weight run on symmetric rotors. It is shown through real cases that, for symmetric rotors such as double-flow low-pressure (LP) turbine and generator rotors, cross effects between static weights (placed in-phase at two ends) and couple response (the same vibration amplitude but 180 degrees out-of-phase at two ends) are minimal and can be neglected. The same holds true for coupled weights (placed 180 degrees out-of-phase at two ends) and static response (the same vibration amplitude inphase at two ends). Real cases show that static and couple influence coefficients for symmetric rotors obtained from the one trial weight run are very close to the true values from the two trial weight runs or the classical static/couple approach. From the calculated static and couple influence data through one trial weight run, final balance weights for reducing static or couple response only or their combination can be determined successfully.
Gas Turbine Performance and Energy Conservation on DDG-51 Class U.S. Navy Ships
Authors: Caguiat Daniel
Published: December 2013

On DDG-51 Class US Navy ships, maximum power and propulsion loads do not require all four main gas turbine engines nor all three electric generator engines to be operating simultaneously. U.S. Navy fleet guidance does not mandate a particular plant configuration at any given time. Therefore, the configuration being used on a given ship to support a particular mission is partially at the discretion of the ship’s crew. This paper focuses on an effort to utilize real-time data from the ship’s power and propulsion plants and auxiliary equipment to assess fuel efficiency and configuration options available, and suggest operating profiles conducive to energy savings. Current Phase I project deliverables, preliminary results, and potential way-forward topics are addressed.
Tribological Behaviours of Titanium Nitride and Chromium Nitride Based PVD Coating Systems
Authors: Cai F. , Huang Xiao , Yang Q. , Nagy Doug
Published: December 2013

This study investigates the effects of the deposition process and coating composition on microstructural and tribological properties of TiN and CrN based coating systems. Coatings were produced using various PVD based processes — electron beam (EB), cathodic arc (CA) and plasma enhanced magnetron sputtering (PEMS). All coated samples were evaluated for their composition, microstructure and surface morphology. Coating mechanical properties such as hardness, Young’s modulus and coefficient of friction were also studied and related to their microstructures, wear and erosion resistances. It was found that hardness (H), Young’s modulus (E) and coefficient of friction had impact on both wear and erosion rates. In particular, the H3/E2 ratio was inversely proportional to the specific wear rate. For erosion behaviour, higher H3/E2 ratios relate to lower erosion rates at low impingement angles; whereas higher H3/E2 ratios relate to higher erosion rates at high impingement angles.
Mitigating the Variability of Wind and Solar Energy Through Pumped Hydroelectric Storage
Authors: Richards S. , Perez-Blanco H.
Published: December 2013

Renewable power production is both variable and difficult to forecast accurately. These facts can make its integration into an electric grid problematic. If an area’s demand for electricity can be met without using renewable generation, the addition of renewable generation would not warrant a further increase in generation capacity. However, to effectively integrate large amounts of additional renewable generation, it is likely that a more flexible generation fleet will be required. One way of increasing a generation fleet’s flexibility is through the adoption of pumped hydroelectric storage (PHS, see the glossary for definitions of select terms). Like traditional hydropower generation, PHS is capable of quickly varying its power output but it is also capable of operating in reverse to store excess energy for later use. This paper will address many of the operational aspects of combining pumped hydroelectric storage (PHS), which is currently used to store excess energy from traditional generators, with wind and solar power generation.

PJM, a grid operator in the Middle Atlantic States, defines capacity value for renewable generation as the percent of installed generating capacity that the generator can reliably contribute during summer peak hours. Existing wind generators inside PJM have an average capacity value of 13% and existing solar generators have a capacity value of 38%. The chief reason for these capacity values is that the renewable power production does not usually coincide with the hours of peak electricity demand during the summer. If PHS were used to firm renewable power generation, it would translate into increased utilization of the renewable generation that would displace the least efficient/most costly generators.

A computer model with one minute granularity is constructed in order to study the operational requirements of PHS facilities. PJM electricity demand, power prices, and wind power production data for 2010 were used in conjunction with NREL simulated solar power production as input to the model. Currently, various PHS operational strategies are being tested to ascertain their effectiveness at firming and time shifting renewable generation. Preliminary results show the profound effects of increased penetration of renewable energy on an electric grid. The results also demonstrate a niche for even greater PHS operational flexibility, i.e. variable speed or unidirectional ternary machine (UTM) PHS.
Crack Propagation Prediction Using Haensel Damage Model
Authors: Bednarz Piotr , Szwedowicz Jaroslaw
Published: December 2013

The Haensel damage model correlates lifetime of a component until crack initiation to the dissipated and stored energy in the material during cyclic loading. The crack initiation is influenced by mean stresses. The Haensel damage model considers the mean stress effect by including compressive and tensile stresses in calculations of elastic strain energy during cyclic loading conditions. The goal of the paper is to extend the above model to predict crack propagation under large cyclic plasticity and non-proportional loading conditions. After voids initiation onset of necking, voids growth and linking takes place among them. During this process a mesocrack is created. This stage of fracture involves the same amount of released energy for new crack surface creation as dissipated energy for mesocrack initiation. The amount of dissipated and stored energy is related to the process zone size and to the number of cycles. Ilyushin’s postulate is used to calculate the amount of dissipated energy. In order to consider a contribution of tensile stresses only during loading to crack propagation, tensile/compressive split is performed for the stress tensor. One of the key drivers of this paper is to provide a straightforward engineering approach, which does not require explicit modelling of cracks. The proposed mathematical approach accounts for redistribution of stresses, strains and energy during crack propagation. This allows to approximate the observed effect of distribution of dissipated energy on the front of a crack tip. The developed approach is validated through FE (Finite Element) simulations of the Dowling and Begley experiment. The Haensel lifetime prediction of Dowling’s experiment is in good agreement with the experimental data and the explicit FE results. Finally, the proposed mathematical approach simplifies significantly the engineering effort for Nonlinear Fracture Mechanics lifetime prediction by avoiding the requirement to simulate real crack propagation using node base release methods, XFEM or remeshing procedures.
Blade Shape Optimization of Marine Propeller via Genetic Algorithm for Efficiency Improvement
Authors: Taheri Ramin , Mazaheri Karim
Published: December 2013

In this paper, a numerical optimization method has been carried out to optimize the shape and efficiency of a propeller. For analysis of the hydrodynamic performance parameters, an extended vortex lattice method was used by implementing an open-source code which is called OpenProp. The method of optimization is a non-gradient based algorithm. After a trade-off between a few gradient-based and non-gradient based algorithms, it is found that the problem of being trapped in local optimum solutions can be easily solved by choosing nongradient based ones. Hence, modified Genetic algorithm is used to implement the so-called hydrodynamic performance analyzer code. The objective function is to maximize efficiency by considering the design variables as non-dimensional blade’s chord and thickness distribution along the blade. For initial guess data of the DTRC 4119 propeller which are radially distributed along the blade is used. The hydrodynamic performance analyzer code is modified by a higher order QuasiNewton scheme. Also hybrid function is used to accurate the convergence. Finally, parallel processing implementation on the codes has been done successfully. To improve the computation speed, the algorithm is improved to be extended on a parallel processing system. The process of parallelizing has been done simplicity by Matlab M-code and the number of cores has been chosen as 4. The final results verify both fast convergence in comparison with common methods and nearly 10% improvement in propeller efficiency (mechanical efficiency of the system) which is significant for these kinds of problems.

Therefore, the algorithm starts with geometry arrived at by other researchers and improves it to a more efficient propeller.
Aerothermodynamic Development of a 70 kW Microturbine
Authors: Rodgers Colin
Published: December 2013

The aerothermodynamic component and engine development of a 70kW microturbine turbogenerator is discussed. The design incorporated a single stage centrifugal compressor mounted back-to-back with a single stage radial inflow turbine both mounted on a common shaft rotating at 90,000 rpm and directly coupled to a permanent magnet generator.

Component testing of the compressor and turbine was conducted at existing academic facilities prior to engine development testing which subsequently demonstrated better output power than design projections as a consequence of higher component efficiencies, increased airflow and better generator performance.
Effectiveness Verification of Creep-Fatigue Assessment Procedures for Fast-Starting Steam Turbines
Authors: Holdsworth Stuart , Radosavljevic Marko , Grossmann Patrick , Kühn Ingo , Mazza Edoardo
Published: December 2013

The paper reviews the methodology adopted in a Swiss Research Collaboration to devise a component-feature representative testpiece geometry and the thermo-mechanical fatigue (TMF) cycle parameters necessary to closely simulate the most arduous conceivable operating duties in steam turbines exposed to cyclic operation. Implementation of these service-like experimental conditions provides a practical indication of the effectiveness of deformation and crack initiation endurance predictions, in particular during fast turbine start-up conditions. Comprehensive post test inspection also provides evidence to demonstrate the physical realism of the laboratory simulations in terms of the creep-fatigue damage generated during the benchmark tests. Mechanical response results and physical damage observations are presented and their practical implications evaluated.
Development US Navy Gas Turbine Vibration Analysis Expertise: LM2500 Vibration and Trim Balance
Authors: Thompson Bruce D. , Grobler Jurie
Published: December 2013

Although generally reliable in-service and with an ever increasing mean time between removal, it was identified in the mid to late 1980’s that the LM2500 gas turbine in US Navy service had a problem with self generated vibration; this was principally due to imbalance in the gas generator or power turbine rotor, however, other non-synchronous sources for vibration were discovered to be important as well. The initial method for resolving this problem was to remove and repair, at a depot, the engines that exceeded the in-service alarm level. This turned out to be a very expensive approach and it was found that most engines that had excessive vibration levels in other respects (performance, etc.) were perfectly acceptable for continued use without repair. Raising the vibration alarm level was tried for a time. However, it became clear that prolonged engine operation with higher levels of vibration were detrimental to the mechanical integrity of the engine. This paper discusses the systematic approach developed to reduce LM2500 self generated vibration levels. This included monitoring system improvements, engine design & hardware improvements and the development and implementation of in-place trim balance. This paper also discusses some of the analysis and practical difficulties encountered reducing and maintaining low LM2500 vibration levels through trim balance and by other means. Also discussed is the present implementation of remotely monitoring LM2500 operating parameters, in particular vibration, through the Integrated Performance Analysis Reports (IPAR) and the Maintenance Engineering Library Server (MELS).
A CFD Study on the Dynamic Coefficients of Labyrinth Seals
Authors: Zhang Donghui , Lee Chester , Cave Michael
Published: December 2013

Labyrinth seals are widely used in gas compressors to reduce internal leakage and increase the compressor efficiency. Due to the eccentricity between the rotating impeller and the stationary part as *well as the shaft whirling motion, forces are generated when the leakage flow passing through the cavities and the seals. For a lot of applications with high speed and pressure, these forces can drive the system unstable. Thus, predicting the forces accurately become a very important for compressor rotordynamic designs.

A lot of research and studies has been done to the seals itself, including bulk flow method, computational fluid dynamic (CFD) and test measurement. The seal and leakage flow interaction forces can be predicted relatively accurate. But very few research treat the seal and cavities as one component interacting with the leakage flow and produce the forces. This paper presents results of CFD investigations on the dynamic coefficients of one typical impeller eye seal and front cavity. The CFD results show that large forces are generated in the front cavity due to circumferential uniform pressure distribution, which caused by the downstream labyrinth seal. The forces generated in the front cavity are more than in the front seal.

It was found that the inertia, damping, and stiffness are proportional to average pressure. The cross-coupling stiffness increases with speed with power of 2 while the direct stiffness increases with speed with power of about 1.7.
A Turbocharged Turbogenerator
Authors: Rodgers C.
Published: December 2013

Turbocharging generally implies the attainment of higher power through increased piston engine air inlet charge density. Turbocharging has too been visualized for gas turbines in the form of an exterior or integrated low pressure compressor and turbine spool module boosting a high pressure power producing spool.

This “turbocharged” cycle has been previously developed for both simple and intercooled recuperative cycles (ICR) gas turbine versions, the latter of which are recognized as one of the most thermally efficient Brayton cycles.

The two spool ICR flowpath with a separate power turbine has been extensively pursued for vehicular and marine applications accompanied with commercialized versions of large turbofans with low pressure (LP) spool power, yet the application of a two spool ICR counterpart with power extraction from the HP spool has been sporadic.

This paper focuses upon the thermodynamic performance and transient operating characteristics of non-concentric two spool non-recuperated Brayton cycles. A hypothetical “turbocharged” adaptation of an existing conventional single shaft 150kW turbogenerator simple cycle gas turbine is chosen as an example with which to portray the concept advantage of increased specific power yet inherent characteristic of diminished hot day performance.
On the Nonlinear Dynamics of Two Types of Backup Bearings: Theoretical and Experimental Aspects
Authors: Lahriri Said , Santos Ilmar F. , Weber Hans I. , Hartmann Henning
Published: December 2013

The possible contact between rotor and stator can for some cases be considered as a serious malfunction that may lead to catastrophic failure. Rotor rub is considered a secondary phenomenon caused by a primary source that leads to a disruption of the normal operational condition. It arises from sudden mass unbalance, instabilities generated by aerodynamic and hydrodynamic forces in seals and bearings among others.

The contact event gives rise to normal and friction forces exerted on the rotor at impact events. The friction force plays a significant role by transferring some rotational energy of the rotor to lateral motion, impacting the stator. This event results in persistent coupled lateral vibration of the rotor and stator. This paper proposes a new unconventional backup bearing design in order to reduce the rub related severity in friction. The idea is to utilize pin connections that center the rotor during impacts. In this way, the rotor is forced to the center and the lateral motion is mitigated. The four pins are passively adjustable, which allows the clearance to be customized.

A mathematical model has been developed to capture phenomena arising from impact for the conventional backup bearing (annular guide) as well for the new disk-pin backup bearing. For the conventional annular guide setup, it is reasonable to superpose an impact condition to the rub, where the rotor spin energy can be fully transformed into rotor lateral movements. Using a non ideal drive, i.e. an electric motor without any kind of velocity feedback control, it is even possible to almost stop the rotor spin under rubbing conditions. All the rotational energy will be transformed in a kind of “self-excited” rotor lateral vibration with repeated impacts against the housing. The vibration of the housing is coupled through the interaction force.

The experimental and numerical analysis shows that for the conventional annular guide setup, the rotational energy is fully transformed into lateral motion and the rotor spin is stopped. However, by employing the new disk-pin design the analysis shows that the rotor at impacts is forced to the center of the backup bearing and the lateral motion is mitigated. As a result of this, the rotor spin is kept constant.
Development of High Temperature Gas Turbine Matrix Microrecuperator Made of Laser Sintered Ceramic and Metal Structural Materials
Authors: Sudarev A. V. , Suryaninov A. A. , Sudarev B. V. , Konakov V. G.
Published: December 2013

Analysis of trends in the development of small gas turbine engines (GTE) has shown that a significant increase in the parameters of the working media required to increase their efficiency and competitiveness in the energy market is limited by the reduced efficiency of small size blading of compressors and turbines [1].

Structural ceramic materials (SCMs), which has high heat resistance and relatively low density, allows development of light-weight and compact heat exchangers for regeneration of heat in the GTE’s which are suitable for continuous operation at the gas temperatures above 1000°C [2].

A design of the heat exchange surface for a countercurrent regenerative AH with a matrix consisting of coaxial cylindrical shells, each of which is made of heat elements (HE) in the form of circular perforated plates of equal width and different diameters, is proposed. The shells are embedded in one another and form a cylindrical matrix with longitudinal channels of circular (air) and semicircular (gas) cross sections.

The AH matrix in the area with the gas temperature over 650°C is made of SMC, while within a zone with lower temperature operation it is made of the heat-resistant alloy. The AH metal matrix model was tested with various coolants in model paths: “air-water”, “water-air” and “air-to-air.”

The experimental results confirmed the data of the thermal-engineering calculations. Such a sintered heat exchanger was designed for microGTE of 2 kW. At the present time it is being fabricated. Bench tests are scheduled for September-November 2012.
A Theoretical and Experimental Comparison of Optimizing Angle of Twist Using BET and BEMT
Authors: Burdett Timothy A. , Van Treuren Kenneth W.
Published: December 2013

Wind turbines are often designed using some form of Blade Element Model (BEM). However, different models can produce significantly different results when optimizing the angle of twist for power production. This paper compares the theoretical result of optimizing the angle of twist using Blade Element Theory (BET) and Blade Element Momentum Theory (BEMT) with a tip-loss correction for a 3-bladed, 1.15-m diameter wind turbine with a design tip speed ratio (TSR) of 5. These two theories have been chosen because they are readily available to small-scale designers. Additionally, the turbine was scaled for experimental testing in the Baylor Subsonic Wind Tunnel. Angle of twist distributions differed by as much as 15 degrees near the hub, and the coefficient of power differed as much as 0.08 for the wind speeds tested.
Three-Dimensional Viscous Flutter Analyses of a Turbine Cascade in Subsonic and Transonic Flows
Authors: Micallef Derek , Witteck Dirk , Wiedermann Alexander , Kluß David , Mailach Ronald
Published: December 2013

In the present contribution the results of two three-dimensional viscous flutter analyses for a turbine cascade, Standard Configuration no. 11, are presented. The steady state and transient flow simulations were performed using the commercially available CFD solver ANSYS CFX 13.0 and a modified version of the CFD solver TBLOCK developed by Denton which is widely used in turbomachinery industry. The flutter analyses are performed under two different flow conditions. A subsonic, attached flow case and an off-design transonic case with a separated flow region near the trailing edge and a normal shock which are both located on the suction side. For each flutter analysis, the aeroelastic solution is computed for a large number of interblade phase angles. The results of ANSYS CFX and TBLOCK are compared to one another as well as to other CFD codes and experimental data. To reduce computing time, a phase-shifted boundary condition was implemented in TBLOCK. First results are shown in comparison to ANSYS CFX and its new implemented Fourier transformation method.

The results of TBLOCK and ANSYS CFX agree well with experimental results. First results applying the phase-shifted boundary condition show that this method is suitable for calculating the aerodynamic damping with less numerical effort.
Helium Brayton Cycles With Solar Central Receivers: Thermodynamic and Design Considerations
Authors: Kusterer Karsten , Braun René , Moritz Norbert , Lin Gang , Bohn Dieter
Published: December 2013

Concentrated Solar Power (CSP) technologies are considered to provide a major contribution for the electric power production in the future. Several technologies for such kind of power plants are already in operation. Parabolic troughs, parabolic dishes, Fresnel multi-facet reflectors or heliostats in combination with a central receiver are applied for concentration of the solar irradiation. The energy conversion cycles usually are water/steam cycles (Rankine cycles), but also open gas turbine cycles (Brayton cycle) or combined cycles are possible. One option is to apply closed Brayton cycles using fluids like carbon dioxide or helium.

With respect to commercial considerations, the main parameter driving the decision on which cycle to apply for energy conversion is the thermal efficiency of the process. This is due to the fact, that in case of a power plant without additional fuel supply, no fuel costs have to be considered to determine the levelized electricity costs (LEC). Thus, in the first place the capital costs determine the LEC. In CSP plants one main driver for the capital costs are the heliostats and the mirror size, which are necessary to generate the desired amount of electric power. The necessary solar aperture area directly depends on the thermal efficiency of the energy conversion cycle.

In this paper different closed Helium Brayton Cycles for application with solar central receivers are analyzed thermodynamically. The thermodynamic calculations are performed by application of a self-developed thermodynamic calculation software, which considers the real gas properties of the fluid. The software calculates the cycle’s thermodynamic diagrams (e.g. T-s-, h-s-diagrams) and determines its efficiency.

The results show that thermal efficiencies of approximately 46.6% (and higher) can be reached with a Helium Brayton Cycle. One important parameter is the turbine inlet gas temperature, which is not less than 900 °C. This means that the pressurized receiver for this technology has to bear even higher temperatures.

Furthermore, the paper deals with design considerations for compressor and turbine within the closed Helium Brayton Cycle. Based on dimensionless parameters, the major parameters like stage types, number of stages, rotational speed etc. are determined and discussed.
Nonlinear Dynamic Effect of Thrust Bearing on a Flexible Rotor Bearing System
Authors: Liu Heng , Liu Yi , Song Xuebin , Yi Jun , Jing Minqing , Wang Weimin , Zhao Shiquan , Qi Xiaobing
Published: December 2013

This article is concerned with the effect of nonlinearities on the stability and bifurcation of a flexible rotor system subjected to the influences of thrust bearing and mass eccentricity. The shaft is modeled by using the finite element method and then the model is reduced by a component mode synthesis method which can account for nonlinear forces and moment of the bearing. The periodic motions and their stability margins are obtained by using shooting method and path-following technique. The numerical results indicate that thrust bearing and mass eccentricity have great influence on stability and bifurcation of the motion of system. Thrust bearing can postpone the bifurcation of the periodic motion of system, heighten the critical speed and the stability threshold speed, and lower the resonant amplitude of the rotor.
On the Design and Matching of Turbocharger Turbines for Pass Car Gasoline Engines
Authors: Gugau Marc , Roclawski Harald
Published: December 2013

With emission legislation becoming more stringent within the next years, almost all future internal combustion gasoline engines need to reduce specific fuel consumption, most of them by using turbochargers. Additionally, car manufactures attach high importance to a good drivability, which usually is being quantified as a target torque already available at low engine speeds that is fast reached in transient response operation. These engine requirements result in a challenging turbocharger compressor and turbine design task, since for both not one single operating point needs to be aerodynamically optimized but the components have to provide for the optimum overall compromise for maximum thermodynamic performance. The component design targets are closely related and actually controlled by the matching procedure that fits turbine and compressor to the engine. Inaccuracies in matching a turbine to the engine full load are largely due to the pulsating engine flow characteristic and arise from the necessity of arbitrary map extrapolation to low turbine blade speed ratios and the estimation of turbine efficiency for low engine speeds.

This paper addresses the above described standard problems, presenting a methodology that covers almost all aspects of thermodynamic turbine design based on a comparison of radial and mixed flow turbines. Wheel geometry definition with respect to contrary design objectives is done using CFD, FEA and optimization software. Parametrical turbine models, composed of wheel, volute and standard piping allow for fast map calculation similar to steady hot gas tests but covering the complete range of engine pulsating mass flow. These extended turbine maps are then used for a particular assessment of turbine power output under unsteady flow admission resulting in an improved steady state matching quality. Additionally, the effect of various design parameters like either volute sizing or the choice of compressor to turbine diameter ratio on turbine blade speed ratio operating range as well as its inertia is analyzed. Finally, this method enables the designer to comparatively evaluate the ability of a turbine design to accelerate the turbocharger speed for transient engine response while still offering a map characteristic that keeps fuel consumption low at all engine speeds.
Steam Turbine Inlet Geometry From a Structural and Fluid Dynamics Point of View
Authors: Hecker Simon , Rohe Andreas , Stoff Horst
Published: December 2013

This work presents guidelines for designing a ring-type inlet duct of an intermediate pressure steam turbine. It looks at aerodynamic characteristics of the flow field in the analyzed ducts as well as the impact of the duct topology on the radial clearances influencing casing deformations in different load cases.

To show the reliability of the CFD-program used, calculated results are compared to measured data. The numerical method reflects the main physical effects observed in the reference cases with high accuracy.

The inlet duct shape influences the loss of total pressure within the duct and the following stator blades as well as the leakage losses in the whole turbine casing. To minimize these losses, geometric parameters such as area ratios within the duct and the shape of its flow channels, are considered and the influence of these parameters on the losses is quantified. The optimization of the inlet duct leads to a geometry with minimum losses from an aerodynamic and mechanical point of view.