bluuebunny/crossref_metadata_2025 huggingface dataset:
Carotid to Femoral Pulse Wave Velocity Reflects the Extent of Coronary Artery Disease
Authors: Hofmann Britt , Riemer Marcus , Erbs Christian , Plehn Alexander , Navarrete Santos Alexander , Wienke Andreas , Silber Rolf‐Edgar , Simm Andreas
Published: August 2014

Arterial stiffness is a well‐established risk factor for cardiovascular disease and mortality. Carotid to femoral pulse wave velocity (cfPWV) as a measure of arterial stiffness was obtained in 155 (47 women; 67.2±9.1 years, range 44–87 years) patients with detected coronary artery disease (CAD) scheduled for coronary artery bypass surgery. The authors set out to analyze how cfPWV in CAD patients correlates with reference values for healthy, normotensive volunteers and whether cfPWV values reflect the extent of CAD. cfPWV was measured with an oscillometric device. Mean cfPWV value of CAD patients was 9.3±1.9 m/s vs 7.7±1.1 m/s in healthy volunteers (P<.0001). In a multiple regression model, age (P<.0001), sex (P=.006), systolic arterial pressure (P=.04), mean arterial pressure (P=.04), and severity of CAD (P<.001) emerged as independent predictive markers for cfPWV in CAD patients. This study established reference values for cfPWV in CAD patients measured with an oscillometric device and confirmed the strong association between arterial stiffness and severity of CAD.
Fluoroscopic and Electrical Assessment of Implantable Cardioverter Defibrillator Leads: A Prospective Observational Study
Authors: McKEAG NICHOLAS A. , HODKINSON EMILY C. , NOAD REBECCA L. , KODOTH VIVEK N. , ASHFIELD KYLE , WILSON CAROL M. , McENEANEY DAVID J. , ROBERTS MICHAEL J.D.
Published: August 2014

Background

Insulation defects resulting in conductor externalization (CE) have been reported in the Riata family of implantable cardioverter defibrillator (ICD) leads (St. Jude Medical, Sylmar, CA, USA). The aim of this study was to identify, prospectively, the rate of CE and outcomes following this, within a group of patients with a Riata ICD lead.

Methods

Patients with a Riata ICD lead attended for fluoroscopic screening and electrical assessment of the lead at yearly intervals between 2010 and 2012.

Results

One hundred and forty patients had no or borderline evidence of CE on initial assessment in 2010. These patients were prospectively followed for 3 years (304.6 patient‐years). During this time, 11 patients developed definite CE, equating to an event rate of 3.6 (95% confidence intervals: 1.8–6.5) per 100 patient‐years of follow‐up. Of those patients developing definite CE, one patient had the ICD lead explanted (for reasons unrelated to CE) and no patients died. CE was not associated with any electrical abnormalities of the ICD lead.

Conclusions

CE was observed at a rate of 3.6 per 100 patient‐years of follow‐up, in 140 individuals with a Riata ICD lead and no definite evidence of CE at baseline.
PUBLIC ADMINISTRATION AND THE INTEGRITY OF THE ELECTORAL PROCESS IN BRITISH ELECTIONS
Authors: CLARK ALISTAIR
Published: August 2014

Although Britain has often been held up as being a model of electoral integrity, recent controversies have suggested that this perception may not be wholly justified. This article explores overall standards of electoral administration across Britain, utilizing performance reporting data for returning officers in the 2010 general election to outline a comprehensive measure for the integrity of the administration of the electoral process. Discussion begins by outlining the question of electoral integrity and, most importantly, the issue of electoral administration. The second section considers recent British controversies, while also outlining steps taken to monitor the performance of electoral administrators. The third section introduces the performance standards and the index of electoral integrity developed from these, while the fourth section presents an analysis. The article concludes with discussion of the challenges facing electoral administrators, and highlights the utility of an index of electoral integrity in helping electoral professionals address these challenges.
Feeling Hopeful Inspires Support for Social Change
Authors: Greenaway Katharine H. , Cichocka Aleksandra , van Veelen Ruth , Likki Tiina , Branscombe Nyla R.
Published: August 2014

Hope is an emotion that has been implicated in social change efforts, yet little research has examined whether feeling hopeful actually motivates support for social change. Study 1 (N = 274) confirmed that hope is associated with greater support for social change in two countries with different political contexts. Study 2 (N = 165) revealed that hope predicts support for social change over and above other emotions often investigated in collective action research. Study 3 (N = 100) replicated this finding using a hope scale and showed the effect occurs independent of positive mood. Study 4 (N = 58) demonstrated experimentally that hope motivates support for social change. In all four studies, the effect of hope was mediated by perceived efficacy to achieve social equality. This research confirms the motivating potential of hope and illustrates the power of this emotion in generating social change.
False Alarms and Missed Events: The Impact and Origins of Perceived Inaccuracy in Tornado Warning Systems
Authors: Ripberger Joseph T. , Silva Carol L. , Jenkins‐Smith Hank C. , Carlson Deven E. , James Mark , Herron Kerry G.
Published: August 2014

Theory and conventional wisdom suggest that errors undermine the credibility of tornado warning systems and thus decrease the probability that individuals will comply (i.e., engage in protective action) when future warnings are issued. Unfortunately, empirical research on the influence of warning system accuracy on public responses to tornado warnings is incomplete and inconclusive. This study adds to existing research by analyzing two sets of relationships. First, we assess the relationship between perceptions of accuracy, credibility, and warning response. Using data collected via a large regional survey, we find that trust in the National Weather Service (NWS; the agency responsible for issuing tornado warnings) increases the likelihood that an individual will opt for protective action when responding to a hypothetical warning. More importantly, we find that subjective perceptions of warning system accuracy are, as theory suggests, systematically related to trust in the NWS and (by extension) stated responses to future warnings. The second half of the study matches survey data against NWS warning and event archives to investigate a critical follow‐up question—Why do some people perceive that their warning system is accurate, whereas others perceive that their system is error prone? We find that subjective perceptions are—in part—a function of objective experience, knowledge, and demographic characteristics. When considered in tandem, these findings support the proposition that errors influence perceptions about the accuracy of warning systems, which in turn impact the credibility that people assign to information provided by systems and, ultimately, public decisions about how to respond when warnings are issued.
Issue Ownership and the Vote: The Effects of Associative and Competence Ownership on Issue Voting
Authors: Lachat Romain
Published: August 2014

Parties often are associated with specific issues. They can “own” an issue when they develop a reputation of competence and attention in that domain. This paper develops an individual‐level model of the effects of issue ownership, distinguishing between two aspects of this concept: which party is considered to care most about a given issue (associative ownership), and which one is perceived to have the best solutions (competence ownership). When a party is the associative owner of a given issue, voters' preferences on the corresponding issue should have a larger impact on the evaluation of the issue owner. But when a party is considered to be most competent in that domain, the effect of spatial distances should decrease. These hypotheses are tested with a statistical model that allows the impact of voter‐party issue distances on party utilities to vary across both parties and issues. This model is tested with data from the 2011 Swiss election study.
Validation of the handheld Lactate‐Pro analyzer for measurement of blood L‐lactate concentration in cattle
Authors: Buczinski Sébastien , Doré Elizabeth , Boulay Guillaume , Francoz David
Published: August 2014

Background

Blood L‐lactate concentration (LAC) can be used for various diagnostic purposes in cattle. As multiple handheld analyzers for LAC exist, it is important to validate their use in cattle in comparison with reference laboratory blood analyzers.

Objectives

The objectives of this study were to validate the handheld Lactate Pro meter (LacP) including reproducibility, and compare the measurements with the StatProfile (StatP) as a gold standard. In addition, diagnostic sensitivity and specificity, and the impact of HCT on LAC measured by both analyzers were assessed.

Methods

A cohort of 64 cattle with acute medical and surgical conditions was studied. Whole blood samples in heparin lithium tubes were analyzed upon arrival with both StatP and LacP. Twenty‐three samples were immediately retested to assess intra‐assay coefficient of variation (CV). The HCT values were also recorded.

Results

The LAC using LacP was highly correlated with the StatP (r = 0.9736 [95% confidence interval [CI]: 0.9562–0.9841]). The LacP underestimated LAC (mean difference:−0.9 mmol/L, 95% CI:−3.1 mmol/L to 1.3 mmol/L). The intra‐assay CV was excellent (4.77%). No significant correlation was observed between LacP or StatP and HCT (P = .39 and .09, respectively). Sensitivity and specificity for LacP were 91.7% (95% CI: 76.4–97.8%) and 100% (83.4–100%, cutoff of 4 mmol/L), and 78.6% (58.5–90.9%) and 100% (87.0–100%, cutoff of 6 mmol/L).

Conclusions

The LacP handheld lactate meter can be used safely and reliably cow‐side, although it underestimates LAC value when compared with a standard laboratory analyzer especially for LAC ≥ 10.0 mmol/L. The LAC value was not influenced by HCT in this study.
Demonstration of Fluidic Throat Skewing for Thrust Vectoring in Structurally Fixed Nozzles
Authors: Yagle Patrick J. , Miller Daniel N. , Ginn K. Brant , Hamstra Jeffrey W.
Published: August 2014

The experimental demonstration of a fluidic, multi-axis thrust vectoring (MATV) scheme is presented for a structurally fixed, afterburning nozzle referred to as the conformal fluidic nozzle (CFN). This concept for jet flow control features symmetric injection around the nozzle throat to provide throttling for jet area control, and asymmetric injection to subsonically skew the sonic plane for jet vectoring. The conceptual development of the CFN was presented in a companion paper (Miller et al., 1999). In that study, critical design variables were shown to be the flap length and expansion area ratio of the nozzle, and the location, angle, and distribution of injected flow. Measures of merit were vectoring capability, gross thrust coefficient, and discharge coefficient. A demonstration of MATV was conducted on a 20%-scale CFN test article across a range of nozzle pressure ratios (NPR), injector flow rates, and flow distributions. Both yaw and pitch vector angles of greater than 8° were obtained at NPR of 5.5. Yaw vector angles greater than 10° were achieved at lower NPR. Values of thrust-coefficient for the CFN generally exceeded published measurements of shock-based, vectoring methods. In terms of vectoring effectiveness (ratio of vector angle to percent injected flow), fluidic throat skewing was found to be comparable to shock-based vectoring methods.
Combined Cycles for High Performance, Low Cost, Low Environmental Impact Waste-to-Energy Systems
Authors: Consonni Stefano
Published: August 2014

This paper assesses the integration between natural gas-fired combined cycles and grate combustors for municipal solid waste (MSW). Saturated steam generated in the grate combustor is exported to the heat recovery steam generator (HRSG) of the combined cycle, where it is superheated and then fed to a steam turbine serving both the combined cycle and the Waste-to-Energy (WTE) plant. Using a single steam turbine reduces costs and increases efficiency; in addition, superheating steam with the clean combustion products discharged by the gas turbine avoids all penalties (and extra-costs) caused by the corrosive gases generated in the grate combustor, which follow a path and are discharged from a stack completely separated from those of the CC. The optimal CC/WTE plant match is achieved when evaporation is carried out almost exclusively in the grate combustor, with the HRSG bearing the load for superheat (and reheat) and part of feedwater heating.

Performance estimates for a combined cycle centered around a medium-size, heavy-duty gas turbine show that WTE/CC integration increases the efficiency of energy recovery from waste by 50% and more, with MSW disposal costs lower by 30–40%. Higher energy conversion efficiencies imply lower environmental impact, notably greater reductions of greenhouse gas emissions.
Application of Incomplete Measurement Data to Thermal Diagnostics of Complex Power Systems Components
Authors: Gluch Jerzy , Krzyzanowski Jerzy
Published: August 2014

Proper exploitation of the complex power systems needs application of diagnostic tools. The diagnostics of power systems can be effective only if reliable simulation methods are available and experimental data are complete.

Unlike that last requirement, it occurs very often in practice that experimental data for particular power cycle components are incomplete. This can happen due to

- inadequate distribution of measuring devices, or

- particular design of the power cycle components which makes the measurement difficult or impossible.

The question arises if any thermal diagnostics of components measured under such condition is possible. The authors try to answer the question taking as an example a specific subsystem of complex power cycle. It is composed of two HP turbine groups of stages, control stage and some glands of the turbine. Making use of the simulation techniques, the authors investigate how much the degradation causes of the elements of this subsystem influences the degradation symptoms of the power cycle. The answer to this question can be of significant importance for the designer of the measuring system and for the user of his thermal diagnostics efforts.
Finite Element Analysis of the Critical Flaw Size in Hybrid Silicon Nitride Bearing Ball
Authors: Warrier Sunil G. , Jarmon David C. , Chin Herbert A.
Published: August 2014

Hybrid bearings containing large silicon nitride balls are considered a critical technology for high speed turbine engine bearing applications. High costs of the balls as well as the lack of a reliable life prediction methodology have hindered extensive use of hybrid bearings in aerospace applications. The presence of surface cracks on silicon nitride balls necessitates the development of a fracture mechanics based approach for life prediction. The key element of the fracture mechanics based approach is the identification of a critical flaw size in silicon nitride balls. Finite element analysis was performed to parametrically vary the crack geometry and to determine the worst case crack geometry conditions. Stress intensity factors were computed for the worst case crack under Hertzian contact loading and in the presence of traction stresses. Failure maps were created that provide a prediction of the maximum permissible surface flaw in silicon nitride bearing balls. Single ball rig tests were performed with induced C-cracks to validate the predictions. Results from the single ball rig test were in good agreement with the results of the analysis for spontaneous spallation. The results of the analysis indicate that 100 μm deep cracks should not cause failure under nominal bearing operation conditions.
Ceramic Vanes for a Model 501-K Industrial Turbine Demonstration
Authors: Wenglarz Richard A. , Kouns Ken
Published: August 2014

First-stage ceramic vanes and their metallic mounts have been designed and fabricated for retrofit into Rolls-Royce Allison Model 501-K turbines. Thermal shock tests of the AS 800 ceramic vanes were conducted using a combustor rig. The ceramic vanes and mounts were then successfully operated in a Model 501-KB5 turbine during engine proof tests for a total of 22 hr. After inspection of the ceramic vane assembly, the turbine was reassembled and shipped to an Exxon natural gas processing plant near Mobile, AL, for the first phase of a field demonstration. The Model 501-KB5 turbine experienced the rigors of commercial operation, including an emergency shutdown (unrelated to the ceramic vane assembly) and a full power water wash. No forced shutdowns associated with the ceramic vanes were experienced. Successful operation for 815 hr (793 hr at Exxon and 22 hr engine proof test) was achieved for the Model 501-KB5 turbine with first-stage ceramic vanes during which the engine sustained power and performance. Analyses of the vanes revealed ceramic oxidation rates that are excessive for industrial turbine applications. A second phase of the ceramic vane demonstration is planned to evaluate environmental barrier coatings (EBCs) to inhibit ceramic oxidation rates.
Experimental Investigations of the Temporal Air-Fuel Mixing Fluctuations and Cold Flow Instabilities of a Premixing Gas Turbine Burner
Authors: Schildmacher K.-U. , Koch R. , Wittig S. , Krebs W. , Hoffmann S.
Published: August 2014

The advantages of premixed combustion are low NOx-emissions, but the drawbacks are possible thermoacoustic instabilities, which became the key issue of modern gas turbine combustion research. The principal mechanisms leading to combustion instabilities of modern low NOx burners are flow instabilities, caused by vortex shedding at the burner outlet, fluctuating recirculation zones and instationary fuel-air mixing. In the present study, a stationary gas turbine burner has been investigated with special emphasis on instationarities that may cause combustion instabilities. The test rig allows detailed investigations of the flow, the air-fuel mixing and the velocity field inside the combustion chamber. At the present stage of the investigations, different flame settings (pilot, non-premixed and premixed operation) were analysed at atmospheric pressure.
9 ppm NOx / CO Combustion System for “F” Class Industrial Gas Turbines
Authors: Vandervort Christian L.
Published: August 2014

The Dry Low NOx (DLN) - 2.6 combustion system has achieved emission rates of lower than 9 ppm NOx (dry, corrected to 15 percent O2) and CO from 50 to 100 percent load for the GE MS7001FA industrial gas turbine on natural gas. The system uses lean premixed combustion with fuel staging for low load stability. The first unit achieved commercial operation in March of 1996 with a firing temperature of 2350 F. As of September 9, 1999, it has accumulated over 11,800 hours of operation in peaking and base load service. Sixteen more units have since entered commercial service. Emissions data are shown for operation on natural gas. The DLN-2.6 system can operate on liquid fuel with water injection for NOx abatement. Power augmentation with steam injection is allowable while operating on natural gas. The premixed gas nozzles utilize swirl for flame stabilization. Aerodynamically shaped natural gas injectors are applied for flashback or flame-holding resistance.
Experimental Replication of an Aeroengine Combustion Instability
Authors: Cohen J. M. , Hibshman J. R. , Proscia W. , Rosfjord T. J. , Wake B. E. , McVey J. B. , Lovett J. , Ondas M. , DeLaat J. , Breisacher K.
Published: August 2014

Combustion instabilities in gas turbine engines are most frequently encountered during the late phases of engine development, at which point they are difficult and expensive to fix. The ability to replicate an engine-traceable combustion instability in a laboratory-scale experiment offers the opportunity to economically diagnose the problem more completely (to determine the root cause), and to investigate solutions to the problem, such as active control. The development and validation of active combustion instability control requires that the causal dynamic processes be reproduced in experimental test facilities which can be used as a test bed for control system evaluation. This paper discusses the process through which a laboratory -scale experiment can be designed to replicate an instability observed in a developmental engine. The scaling process used physically-based analyses to preserve the relevant geometric, acoustic and thermo-fluid features, ensuring that results achieved in the single-nozzle experiment will be scaleable to the engine.
Acoustic Resonances of an Industrial Gas Turbine Combustion System
Authors: Hubbard S. , Dowling A. P.
Published: August 2014

A theory is developed to describe low frequency acoustic waves in the complicated diffuser/combustor geometry of a typical industrial gas turbine. This is applied to the RB211-DLE geometry to give predictions for the frequencies of the acoustic resonances at a range of operating conditions. The main resonant frequencies are to be found around 605 Hz (associated with the plenum) and around 461 Hz and 823 Hz (associated with the combustion chamber), as well as one at around 22 Hz (a bulk mode associated with the system as a whole).
The Propagation of a Fuel-Air Ratio Disturbance in a Simple Premixer and its Influence on Pressure Wave Amplification
Authors: Scarinci Thomas , Freeman Christopher
Published: August 2014

The propagation of a fuel concentration disturbance in a premixer is studied analytically with a 3-D spatio-temporal mixing model. A simple analytical method is introduced which permits the frequency response characteristics of multiple points of fuel injection in simple (yet meaningful) premixer passage geometries to be obtained. The results provide physical insight into some of the design parameters that may affect the amplitude of FAR fluctuations coming out of a premixer when it is subjected to finite amplitude pressure waves. The possibility of a given design to lead to amplification of pressure waves (Rayleigh’s criteria) can be influenced by the characteristics of the mixing processes in a premixer channel. Results obtained in this paper may affect the design implementation of some of the proposals made for the control of combustion instability such as introduction of multiple time delays through selective fuel placement in a premixer.
Self-Excited Oscillations in Combustors With Spray Atomisers
Authors: Zhu M. , Dowling A. P. , Bray K. N. C.
Published: August 2014

Combustors with fuel-spray atomisers are susceptible to a low-frequency oscillation, particularly at idle and sub-idle conditions. For aero-engine combustors, the frequency of this oscillation is typically in the range 50–120Hz and is commonly caused ‘rumble’. In the current work, Computational Fluid Dynamics (CFD) is used to simulate this self-excited oscillation. The combustion model uses Monte Carlo techniques to give simultaneous solutions of the Williams’ spray equation together with the equations of turbulent reactive flow. The unsteady combustion is calculated by the laminar flamelet presumed pdf method. A quasi-steady description of fuel atomiser behaviour is used to couple the inlet flow in the combustor. A choking condition is employed at turbine inlet. The effects of the atomiser and the combustor geometry on the unsteady combustion are studied. The results show that, for some atomisers, with a strong dependence of mean droplet size on air velocity, the coupled system undergoes low frequency oscillations. The numerical results are analysed to provide insight into the rumble phenomena. Basically, pressure variations in the combustor alter the inlet air and fuel spray characteristics, thereby changing the rate of combustion. This in turn leads to local ‘hot spots’, which generate pressure fluctuations as they convect through the downstream nozzle.
Research on a Methane-Fueled Low NOx Combustor for a Mach 3 Supersonic Transporter Turbojet Engine
Authors: Kinoshita Yasuhiro , Oda Takeo , Kitajima Junichi
Published: August 2014

Methane-fueled low NOx combustor research had been conducted under the Japanese supersonic/hypersonic propulsion research programme. A unique form of premixture jet swirl combustor (PJSC) was proposed for the ultra low NOx combustor of a Mach 3 turbojet engine. Fuel-air mixing tests and fundamental combustion tests were conducted to obtain the design data and combustion characteristics in the first phase of the research. A single can type combustor was fabricated and high temperature and high pressure combustion tests were carried out for the evaluation on NOx emission reduction capability of the PJSC concept in the second phase. In the final phase of research, a multi-sector combustor was fabricated and the performance demonstration test was conducted for the final evaluation of the pollutant exhaust emission goals and the combustor performance goals set in the HYPR project.

The sequential three phased program was completed successfully, and the project goals of NOx emission, combustion efficiency, pressure loss and exit gas temperature pattern factor at the Mach 3 cruise condition, together with the ICAO regulatory levels for supersonic aircraft at LTO conditions, were all achieved in the performance demonstration test.
Parametric Modeling Approach to Gas Turbine Combustor Design
Authors: Tangirala Venkat E. , Tolpadi Anil K. , Danis Al M. , Mongia Hukam
Published: August 2014

Recent advances in CAD/CAE based design tools have not only enabled the automation of parametric sensitivity analyses involving aero, thermal and structural calculations necessary for gas turbine combustor life predictions, but have also minimized the analysis cycle time required to perform such parametric analyses. Concepts involved in development of the parametric models for geometry creation, grid generation and unstructured Computational Fluid Dynamics (CFD) simulations of a gas turbine combustor are discussed. In addition, the advantages of utilizing the parametric geometry and analysis models in parametric sensitivity studies of combustor aero analysis are demonstrated. A CAD-based parametric master model for 3-D solid feature creation and aero-analysis parametric models were developed for a modern GE single annular aircraft gas turbine combustor. Using these parametric models, a matrix of geometries was generated to define the computational domain for performing a parametric sensitivity study involving aero analysis, for combustor exit temperature predictions. The present combustor parametric aero-analysis considers the effects of the location of dilution holes and film slots in the combustor inner and outer liner components on the gas turbine combustor exit temperature profiles. Comparisons of the predicted combustor exit temperatures with available test data for an 18° annular sector are presented.
An Approximate Method for Jet Engines Flight Performances Prediction
Authors: Ghenaiet A.
Published: August 2014

This paper describes a fast simulation procedure to predict airbreathing engines steady state flight performances. This procedure uses an alternate method that works without the need of component maps and the corresponding matching. This method operates on simplified assumptions, such as constant power setting, without air bleed or power extraction. This approximate method for flight performance prediction is validated for three types of jet engines such as the P&W JT8D mixed flows turbofan, the GE CF6-80 high bypass turbofan. and the Russian double spool turbojet R11F-300.
Repowering of an Existing Cogeneration Plant Including Environmental Cost Internalization
Authors: Calì M. , Massardo A. F. , Santarelli M.
Published: August 2014

In this paper an existing cogeneration plant (134 MWel and 225 MWth) based on gas turbine and steam cycle technology, has been investigated. The main goal of the work is to analyse different repowering options for the plant taking into account the capital cost of the new devices, the cost of the fuel and the cost related to the CO2 emissions. For the analysis of the repowering alternatives the Thermoeconomic Analysis has been utilised. Two different approaches have been used for the CO2 emissions cost evaluation: the classical Carbon Tax approach using political charges on the unit ton of emitted CO2, and one proposed by the Authors linked to the efficient utilization of energy resources in the plants, and based on the exergy analysis.

In the paper the two procedures for the evaluation of the charges on the CO2 emissions and their influence on the choice of the repowering option, and how they promote the adoption of a high efficiency repowering solutions have been discussed.
Natural Gas Decarbonization to Reduce CO2 Emission From Combined Cycles: Part A — Partial Oxidation
Authors: Lozza Giovanni , Chiesa Paolo
Published: August 2014

This paper discusses novel schemes of combined cycle, where natural gas is chemically treated to remove carbon, rather than being directly used as fuel. Carbon conversion to CO2 is achieved before gas turbine combustion. Therefore CO2 can be removed from fuel (rather than from exhausts, thus utilizing less demanding equipment) and made available for long-term storage, to avoid dispersion toward the atmosphere and the consequent contribution to the greenhouse effect.

The strategy here proposed to achieve this goal is natural gas partial oxidation. The second part of the paper will address steam / methane reforming. Partial oxidation is an exothermic oxygen-poor combustion devoted to CO and H2 production. The reaction products are introduced in a multiple stage shift reactor converting CO to CO2. Carbon dioxide is removed by means of physical or chemical absorption processes and made available for storage, after compression and liquefaction. The resulting fuel mainly consists of hydrogen and nitrogen, thus gas turbine exhausts are virtually devoid of CO2.

The paper discusses the selection of some important parameters necessary to obtain a sufficient level of conversion in the various reactors (temperature and pressure levels, methane-to-air or methane-to-steam ratios) and their impact on the plant integration and on the thermodynamic efficiency. Overall performance (efficiency, power output and carbon removal rate) is predicted by means of a computational tool developed by the authors. The results show that a net efficiency of 48.5%, with a 90% CO2 removal, can be obtained by combined cycles based on large heavy duty machines of the present technological status, either by using chemical or physical absorption.
Assessment of LNG Regasification Systems With Cogeneration
Authors: Desideri Umberto , Belli Claudio
Published: August 2014

Natural gas is usually transferred to consumers through pipelines, which may cover distances of thousands of kilometers. In some cases, however, when the path of the pipelines crosses seas or countries where the politic situation does not ensure a continuous and reliable flow, other means of transportation are preferred. In these cases, the natural gas is liquefied and transported in tankers, which load the tanks at liquefaction plants and discharge them at regasification plants. This gives a considerable chance to differentiate supply sources and allows gas imports from producing countries that are otherwise inaccessible via pipeline.

The aim of this paper is the study of systems, which carry out liquefied natural gas (LNG) vaporization using cogenerative solutions. The following configurations were studied in particular:

• Gas-steam combined cycles;

• Closed gas-gas combined cycles using three different working fluids.

Two typical plant sizes and two gas pressure sendout levels (7.3 MPa for long distance pipeline networks and 2.5 MPa for terminals linked to power production plants with combined cycles) have been analyzed. The suggested solutions have been optimized, and performance calculated. The discussion is completed by a simplified economic analysis.
A Neural Network Simulator of a Gas Turbine With a Waste Heat Recovery Section
Authors: Boccaletti C. , Cerri G. , Seyedan B.
Published: August 2014

The objective of the paper is to assess the feasibility of the neural network (NN) approach in power plant process evaluations. A “feedforward” technique with a back propagation algorithm was applied to a gas turbine equipped with waste heat boiler and water heater. Data from physical or empirical simulators of plant components were used to train such a NN model. Results obtained using a conventional computing technique are compared with those of the direct method based on a NN approach. The NN simulator was able to perform calculations in a really short computing time with a high degree of accuracy, predicting various steady-state operating conditions on the basis of inputs that can be easily obtained with existing plant instrumentation. The optimization of NN parameters like number of hidden neurons, training sample size and learning rate is discussed in the paper.
Experimental Investigations on the Thermal Load and Leakage Flow of a Turbine Blade Tip Section With Different Tip Section Geometries
Authors: Urban Martin F. , Vortmeyer Nicolas
Published: August 2014

The gap flow across the tips of cooled rotor blades of combustion turbines is of crucial importance for the thermal load of the tip section and the stage efficiency. Various blade tip section designs with different cooling concepts were tested in a two dimensional steam cascade test rig with superheated steam as working fluid. The blade tip surface temperature distributions were measured with a thermography system and the gap flow was determined by 105 static wall pressure measurements at the opposite wall. The experimental program included systematic variations of decisive flow parameters like Mach and Reynolds numbers of the main and leakage flow as well as variations of the gap width in a range of 1.6% to 4.8% of the chord length. The performance of a simple flat blade tip served as a baseline for the comparison with advanced grooved tip designs developed in earlier studies. In addition attention was given to a systematic investigation of the influence of the coolant mass flow ejected out of the blade into the grooved tip section. The paper presents an overview of the experimental program and results as well as a discussion of the influence of the main flow and geometry parameters on the leakage flow characteristics and the accompanying thermal load of the tip section.
Time-Averaged Heat Flux for a Recessed Tip, Lip, and Platform of a Transonic Turbine Blade
Authors: Dunn M. G. , Haldeman C. W.
Published: August 2014

The results of an experimental research program determining the blade platform heat-flux level and the influence of blade tip recess on the tip region heat transfer for a full-scale rotating turbine stage at transonic vane exit conditions are described. The turbine used for these measurements was the Allison VBI stage operating in the closed vane position (vane exit Mach number _ 1.1). The stage was operated at the design flow function, total to static pressure ratio, and corrected speed. Measurements were obtained at several locations on the platform and in the blade tip region. The tip region consists of the bottom of the recess, the lip region (on both the pressure and suction surface sides of the recess), and the 90% span location on the blade suction surface. Measurements were obtained for three vane/blade spacings; 20%, 40%, and 60% of vane axial chord and for a single value of the tip gap (the distance between the top of the lip and the stationary shroud) equal to 0.0012-m (0.046-in) or 2.27% of blade height.
High Freestream Turbulence Effects on Endwall Heat Transfer for a Gas Turbine Stator Vane
Authors: Radomsky R. W. , Thole K. A.
Published: August 2014

High freestream turbulence along a gas turbine airfoil and strong secondary flows along the endwall have both been reported to significantly increase convective heat transfer. This study superimposes high freestream turbulence on the naturally occurring secondary flow vortices to determine the effects on the flowfield and the endwall convective heat transfer. Measured flowfield and heat transfer data were compared between low freestream turbulence levels (0.6%) and combustor simulated turbulence levels (19.5%) that were generated using an active grid. These experiments were conducted using a scaled-up, first stage stator vane geometry. Infrared thermography was used to measure surface temperatures on a constant heat flux plate placed on the endwall surface. Laser Doppler velocimeter (LDV) measurements were performed of all three components of the mean and fluctuating velocities of the leading edge horse-shoe vortex. The results indicate that the mean flowfields for the leading edge horseshoe vortex were similar between the low and high freestream turbulence cases. High turbulence levels in the leading edge-endwall juncture were attributed to a vortex unsteadiness for both the low and high freestream tubulence cases. While, in general, the high freestream turbulence increased the endwall heat transfer, low augmentations were found to coincide with the regions having the most intense vortex motions.
Heat Transfer in Rotating Narrow Rectangular Ducts With Heated Sides Oriented at 60° to the r-z Plane
Authors: Willett Fred T. , Bergles Arthur E.
Published: August 2014

Gas turbine blade life is often limited by the effectiveness of the cooling in the trailing edge convective cavity, which generally has a narrow cross-section. Previous research on rotational effects considered cavity shapes quite different from those of typical trailing edge cavities. In this research, experiments were conducted to determine the effect of rotation on heat transfer in ducts of narrow cross-section (height-to-width ratio of 1:10), oriented with the heated sides at 60° to the r-z plane. In the experiment, a high-molecular-weight gas (Refrigerant-134A) at ambient pressure and temperature conditions was used to match the dimensionless parameters at engine conditions. Thin foil heaters were used to produce a constant heat flux at the long sides of the duct; the narrow sides were unheated. Duct Reynolds numbers were varied up to 20,000; rotation numbers were varied up to 0.25. The test results show the effect of rotation and aspect ratio on duct leading and trailing side heat transfer. In addition, the results show the variation in heat transfer coefficient with transverse location in the duct, demonstrating the effect of rotation not only on lead and trail side heat transfer, but also on forward and aft end heat transfer.
Flow and Heat Transfer in a Rotating Square Channel With 45° Angled Ribs by Reynolds Stress Turbulence Model
Authors: Jang Yong-Jun , Chen Hamn -Ching , Han Je-Chin
Published: August 2014

Numerical predictions of three -dimensional flow and heat transfer are presented for a rotating square channel with 45° angled ribs as tested by Johnson et al. (1994). The rib height-to-hydraulic diameter ratio (e/Dh) is 0.1 and the rib pitch-to-height ratio (P/e) is 10. The cross-section of the ribs has rounded edges and corners. The computation results are compared with Johnson’s et al. (1994) experimental data at a Reynolds number (Re) of 25,000, inlet coolant-to-wall density ratio (Δρ/ρ) of 0.13, and three rotation numbers (Ro) of 0.0, 0.12, 0.24.

A multi-block numerical method has been employed with a near-wall second-moment turbulence closure model. In the present method, the convective transport equations for momentum, energy, and turbulence quantities are solved in curvilinear, body-fitted coordinates using the finite-analytic method. Pressure is computed using a hybrid SIMPLER/PISO approach, which satisfies the continuity of mass and momentum simultaneously at every time step. The second-moment solutions show that the secondary flows induced by the angled ribs, rotating buoyancy, and Coriolis forces produced strong non-isotropic turbulent stresses and heat fluxes that significantly affected flow fields and surface heat transfer coefficients. The present near-wall second-moment closure model provided an improved flow and heat transfer prediction.
A Transient Liquid Crystal Method Using Hue Angle and a 3-D Inverse Transient Conduction Scheme
Authors: Lin Mingjie , Wang Ting
Published: August 2014

Various transient liquid crystal methods have been widely and routinely employed to measure surface heat transfer coefficients. Typically, the heat transfer surface was modeled as a one-dimensional, transient heat conduction over a semi-infinite surface to retrieve information of the surface heat transfer coefficients. To satisfy the theoretical initial and boundary conditions, inconvenient and/or complex designs are required. Frequently, the conditions are not exactly satisfied. To resolve these issues, an approach of measuring heat transfer coefficients coupling the transient liquid crystal method with a 3-D inverse transient conduction scheme was developed and was applied to a nonuniform heat transfer surface produced by arrays of impinging jets.

The present method utilized the hue-angle method to process the color images captured from the liquid crystal color play. Instantaneous temperature readings from embedded thermocouples were utilized for in-situ calibration of hue angle for each data set. The convective heat transfer coefficient results were obtained by performing a 3-D inverse transient conduction calculation over the entire jet impingement target surface and the substrate. The results of average heat transfer coefficients agreed well with previous experimental results of point measurements by thermocouples.
Effect of Surface Curvature on Heat Transfer and Hydrodynamics Within a Single Hemispherical Dimple
Authors: Syred N. , Khalatov A. , Kozlov A. , Shchukin A. , Agachev R.
Published: August 2014

Turbulent heat transfer and hydrodynamics have been studied in concavely and convexly curved dimple in the range of Reynolds number from 1.3×105 to 3.1×105. The large scale single hemispherical dimple 50 mm diameter and 25 mm depth was arranged on a smooth concave or convex wall of curved rectangular-shaped passage. The fluid flow and heat transfer measurements, surface streamlines observations were performed within the flow curvature parameter δ**/R ranged from 0.002 to 0.007. The ‘tornado-like’ oscillating vortex bursting periodically out of dimple was registered in the experiments with a ‘curved’ dimple. This vortex structure is similar to that earlier observed in a ‘flat’ dimple. The surface curvature influences considerably the dimple heat transfer rate in both cases. It enhances heat transfer in a ‘concave’ dimple and reduces it in a ‘convex’ one, however the more remarkable effect is occurred in a concavely curved dimple. The correction factors describing the effect of curvature on average heat transfer in a ‘curved’ dimple have been obtained as a result of experimental study.
Novel Blade Cooling Engineering Solution
Authors: Moser Siegfried , Ivanisin Mario , Woisetschläger Jakob , Jericha Herbert
Published: August 2014

The evolution of increasing turbine inlet temperature has led to the necessity of full-coverage film cooling for the first turbine vane and blade. In this paper a new approach using transonic wall film jets for blade and vane cooling is investigated to provide a first guideline for engineering design. The first part presents a Computation Fluid Dynamics (CFD) cooling efficiency investigation on a flat plate with varied injection angles, turbulence intensities and blowing ratios. The results show a strong tendency to bend towards the roundness at cooling slit outlet. Therefore the cooling efficiency isn’t hardly influenced by cooling supply angle. Further it has been noticed that high mainflow turbulence coupled with a high mainflow velocity leads to a high turbulent kinetic energy in the mainflow, affects the cooling efficiency. This investigation with different turbulence intensities shows further, that turbulence intensity rate Tu [%] isn’t a suitable dimension to rate the “destructive Power” of mainflow turbulence to cooling jets. With these results detailed 2D- and 3D-Navier-Stokes external flow calculations coupled with the appropriate solid heat conduction calculations for a cooled turbine blade were modelled. Therefore a blade with five cooling slit rows was used. Two slit rows for trailing edge cooling and one slit row for pressure and suction side respectively and one slit row for the leading edge were used to model a full preserved blade. On the basis of heat transfer and temperature distribution of the 3D-CFD calculation of the blade a Finite Element Analysis (FEA) was realised, showing the points of maximum stresses.
Local Heat/Mass Transfer Measurement on the Effusion Plate in Impingment/Effusion Cooling System
Authors: Cho Hyung Hee , Rhee Dong Ho
Published: August 2014

The present study is conducted to investigate the local heat/mass transfer characteristics for flow through perforated plates. A naphthalene sublimation method is employed to determine the local heat/mass transfer coefficients on the effusion plate. Two parallel perforated plates are arranged in two different configurations: staggered and shifted in one direction. The experiments are conducted for hole pitch-to-diameter ratios of 6.0, for gap distance between the perforated plates of 0.33 to 10 hole diameters, and for Reynolds numbers of 5,000 to 12,000. The result shows that the high transfer region is formed at stagnation region and at the mid-line of the adjacent impinging jets due to secondary vortices and flow acceleration to the effusion hole. For flows through the perforated plates, the mass transfer rates on the surface of the effusion plate are about six to ten times higher than for effusion cooling alone (single perforated plate). In general, higher heat/mass transfer is obtained with smaller gap distance between two perforated plates.
High Lift and Aft Loaded Profiles for Low Pressure Turbines
Authors: Howell R. J. , Ramesh O. N. , Hodson H. P. , Harvey N. W. , Schulte V.
Published: August 2014

This paper shows how it is possible to reduce the number of blades in LP turbines by approximately 15% relative to the first generation of high lift blading employed in the very latest engines. This is achieved through an understanding of the behaviour of the boundary layers on high lift and ultra high lift profiles subjected to incoming wakes.

Initial development of the new profiles was carried out by attaching a flap to the trailing edge of one blade in a linear cascade. The test facility allows for the simulation of upstream wakes by using a moving bar system. Hot wire measurements were made to obtain boundary layer losses and surface mounted hot films were used to observe the changes in boundary layer state. Measurements were taken at a Reynolds number between 100,000 and 210,000.

The effect of increased lift above the datum profile was investigated first with steady and then with unsteady inflow (i.e. with wakes present). For the same profile, the losses generated with wakes present were below those generated by the profile with no wakes present. The boundary layer behaviour on these very high lift pressure distributions suggested that aft loading the profiles would further reduce the profile loss.

Finally, two very highly loaded and aft loaded LP turbine profile were designed and then tested in cascade. The new profiles produced losses only slightly higher than those for the datum profile with unsteady inflow, but generated 15% greater lift.