bluuebunny/crossref_metadata_2025 huggingface dataset:
Who Benefited More from the North American Free Trade Agreement: Small or Large Farmers? Evidence from Mexico
Authors: Prina Silvia
Published: July 2013

This paper measures the impact of increasing trade openness between Mexico and the USA resulting from the North American Free Trade Agreement (NAFTA) on the income of small versus large farmers in Mexico. Benefits resulting from higher prices of export goods as well as losses incurred from greater import competition are considered. First, relating NAFTA cuts in trade restrictions to border prices of Mexican exports and imports, it is found that NAFTA‐induced tariff reductions decreased the border price of corn, Mexico's main agricultural import, and increased the border prices of tomatoes and melons, Mexico's main agricultural exports. Then, it is shown that the rise in fruit and vegetable prices benefited small farmers more than large farmers; while the drop in corn prices hurt large farmers more. Finally, the results from the regional‐level analysis suggests that the effects are stronger in the central states than in the northern and southern states.
The Dynamic Effects of Fiscal Stimulus in a Two‐Sector Open Economy
Authors: Guest Ross , Makin Anthony
Published: July 2013

In 2009/10 governments around the world implemented unprecedented fiscal stimulus in order to counter the impact of the Global Financial Crisis of 2008/09. This paper analyzes the impact of fiscal stimulus using a dynamic open economy, overlapping generations model that allows for feedback effects of fiscal stimulus on private sector expenditure via changes in the tax rate and the interest rate. There are two types of goods—traded (T) and nontraded (N) goods—which differ in their capital intensities. The main qualitative result is that the dynamic output gains from fiscal stimulus depend on the productivity of the initial stimulus spending, on the speed of repayment of debt, on the sensitivities of the interest rate to government debt and of labor supply to the tax rate. Also, the overlapping generations framework allows an intergenerational welfare analysis. Among the biggest winners from stimulus are those about to retire. The biggest losers are those near the start of their working lives when the stimulus is implemented.
Hemodialysis and Water Quality
Authors: Coulliette Angela D. , Arduino Matthew J.
Published: July 2013

Over 383,900 individuals in the U.S. undergo maintenance hemodialysis that exposes them to water, primarily in the form of dialysate. The quality of water and associated dialysis solutions have been implicated in adverse patient outcomes and is therefore critical. The Association for the Advancement of Medical Instrumentation has published both standards and recommended practices that address both water and the dialyzing solutions. Some of these recommendations have been adopted into Federal Regulations by the Centers for Medicare and Medicaid Services as part of the Conditions for Coverage, which includes limits on specific contaminants within water used for dialysis, dialysate, and substitution fluids. Chemical, bacterial, and endotoxin contaminants are health threats to dialysis patients, as shown by the continued episodic nature of outbreaks since the 1960s causing at least 592 cases and 16 deaths in the U.S. The importance of the dialysis water distribution system, current standards and recommendations, acceptable monitoring methods, a review of chemical, bacterial, and endotoxin outbreaks, and infection control programs are discussed.
Prevention of Peritonitis in Peritoneal Dialysis
Authors: Segal Jonathan H. , Messana Joseph M.
Published: July 2013

Reducing the frequency of peritonitis for patients undergoing peritoneal dialysis (PD) continues to be a challenge. This review focuses on recent updates in catheter care and other patient factors that influence infection rates. An experienced nursing staff plays an important role in teaching proper PD technique to new patients, but nursing staff must be cognizant of each patient's unique educational needs. Over time, many patients become less adherent to proper dialysis technique, such as washing hands or wearing a mask. This behavior is associated with higher risk of peritonitis and is modifiable with re‐training. Prophylactic antibiotics before PD catheter placement can decrease the infection risk immediately after catheter placement. In addition, some studies suggest that prophylaxis against fungal superinfection after antibiotic exposure is effective in reducing fungal peritonitis, although larger randomized studies are needed before this practice can be recommended for all patients. Over time, exit site and nasal colonization with pathogenic organisms can lead to exit‐site infections and peritonitis. For patients with Staphylococcus aureus colonization, exit‐site prophylaxis with either mupirocin or gentamicin cream reduces clinical infection with this organism. Although there are limited data for support, antibiotic prophylaxis before gastrointestinal, gynecologic, or dental procedures may also help reduce the risk of peritonitis.
The Economics of Hemodialysis Catheter‐Related Infection Prophylaxis
Authors: Kosa S. Daisy , Lok Charmaine E.
Published: July 2013

Hemodialysis central venous catheter (CVC) use is associated with the highest morbidity, mortality, and cost of all types of hemodialysis vascular access. CVC‐related infection drives much of the cost associated with CVC use. The magnitude of the cost associated with CVC‐related infection varies depending on the type and severity of that infection; however, estimates of the total direct and indirect costs associated with hospitalizations due to hemodialysis CVC‐related infections range from 17,000 USD to 32,000 USD per episode. Thus, it is critically important, to not only have effective strategies to limit CVC‐related infection but also evaluate whether these strategies are an efficient use of resources. Prophylactic strategies can be considered economically efficient only if the value of its implementation and the corresponding drop in infection rate offer greater value than standard care. The optimal CVC‐related infection prophylaxis strategy should work to limit infection risk with minimal risk, inconvenience, and discomfort to the patient, and at minimal cost. The aim of this review was to examine the clinical and economic impact of some commonly described interventions used for CVC infection prophylaxis.
A Systematic Review of Buttonhole Cannulation Practices and Outcomes
Authors: Grudzinski Alexa , Mendelssohn David , Pierratos Andreas , Nesrallah Gihad
Published: July 2013

Buttonhole (constant site) cannulation has emerged as an attractive technique for needling arteriovenous fistulae. However, the balance of benefits and harms associated with this intervention is unclear. We conducted a systematic review of studies reporting outcomes with buttonhole cannulation. The setting and population included adult patients receiving home or center hemodialysis. We searched MEDLINE, Embase (1980‐June 2012), and CINAHL (1997‐June 2012), for randomized and observational studies. We also searched conference proceedings (2009–2011). The interventions included: 1) buttonhole cannulation established by sharp needles, with or without a polycarbonate peg, 2) rope‐ladder cannulation. Outcomes of interest included: Facility practices, systemic infection, local infection, access survival, access interventions, access‐related hospitalization, patient survival, pain, quality of life, and aneurysm formation. We identified 23 full‐text articles and 4 abstracts; 3 were open‐label trials, and the remainder observational studies of varying design and methodological quality. Studies were predominantly descriptive and lacked direct comparisons between buttonhole and rope‐ladder cannulation. No qualitative differences in outcomes were noted among home and center hemodialysis patients using buttonhole cannulation. Rates of bacteremia were generally higher with buttonhole cannulation. Studies reporting access survival, hospitalization, quality of life, pain, and aneurysm formation had serious methodological limitations that limited our confidence in their estimates of effect. Among the various facility practices that were described, only the application of mupirocin cream was noted to be associated with reduced risk of infection. Limitations in included studies were short follow‐up, crossover designs, lack of parallel control groups, and the use of patient‐reported outcome measures that were not well validated. The main limitation of this review was a limited literature search. Buttonhole cannulation may be associated with an increased risk of infection. Larger, more definitive studies are needed to determine whether this technique is safe for broader use.
The epidemiology of human T‐cell lymphotropic virus types I and II in Canadian blood donors
Authors: O'Brien S. F. , Goldman M. , Scalia V. , Yi Q. ‐L. , Fan W. , Xi G. , Dines I. R. , Fearon M. A.
Published: July 2013

Objectives

Blood donors in Canada have been tested for Human T‐Cell Lymphotropic Virus (HTLV) since 1990. We report the epidemiology, risk factors and lookback/traceback of HTLV‐positive donors/recipients.

Methods

The annual HTLV rate was calculated from 1990 to 2010. Residual risk was estimated as the product of incidence and window period. Twenty‐nine HTLV‐positive donors and 116 matched controls (ratio 1 : 4) were interviewed about risk factors. For HTLV‐positive donations, lookback investigations involved identification of all previous donations, and attempting to locate and test recipients. Traceback was initiated when transfusion transmission was queried for HTLV‐positive blood recipients. All donors of products that the recipient received were identified, with an attempt to locate and test them.

Results

The HTLV rate decreased from 9·35 per 100 000 donations in 1990 to 1·11 in 2010. The residual risk of infection was 1 in 7·6 million donations. In logistic regression birth overseas (OR 18·7), history of sexually transmitted diseases (OR 32·9), sex with unknown background (OR 5·4) and blood transfusion (OR 8·9) were significant predictors. In the lookback study, of 109 HTLV‐positive donors, 508 components were transfused, of whom 147 recipients were tested and 18 (12%) were positive. All were transfused prior to the implementation of donor testing. Twenty‐three traceback investigations were requested involving 324 transfused untested products,of whom 219 (67·6%) of donors were tested and 13 (6%) were positive for HTLV.

Conclusions

With testing of the blood supply, the risk from HTLV is very low and while most HTLV‐positive donors have risk factors, deferrable risk is rare.
Serosurvey and Observational Study of US Army Veterinary Corps Officers for Q Fever Antibodies from 1989 to 2008
Authors: Vest K. G. , Clark L. L.
Published: July 2013

Since World War II, the military has experienced outbreaks of Q fever among deploying units including recent case reports of Q fever in US military personnel returning from serving in the Middle East during Operation Iraqi Freedom and Operation Enduring Freedom. Occupational exposure and prevalence of Q fever among US Army Veterinary Corps officers have not been examined. A retrospective serosurvey and observational study of 500 military veterinarians were conducted using archived serum specimens from military veterinarians who entered and served between 1989 and 2008 and were tested for exposure to Coxiella burnetii. Corresponding longitudinal health‐related, demographic, medical and deployment data were examined. A total of 69 (13.8%) individuals at military entry and 85 (17%) had late career positive titres. A total of 18 (3.6%) individuals showed seroconversion. Women were more likely to be seropositive after military service [prevalence ratio (PR) 1.96; 95% confidence interval (CI) 1.15–3.35] and were also more likely to seroconvert (incidence rate ratio 3.55; 95% CI 1.19–12.7). Women who deployed to Operation Iraqi Freedom were more likely to be seropositive (PR 3.17; 95% CI 1.03–9.71). Veterinarians with field service and pathology specialties had the highest incidence rates (7.0/1000 PY; 95% CI 4–12 and 3–19, respectively). This is the first report documenting US military veterinarians' exposure to C. burnetii. Military veterinarians are at risk prior to service, with moderate number of new cases developing during service and most maintaining titres for long periods of time. Women consistently demonstrated higher seroprevalence and incidence levels. As increasing numbers of women enter the veterinary profession and subsequently the US Army, this may warrant close monitoring. This study likely underestimates exposure and risk and does not address chronic health effects, which may be valuable to explore in future health studies.
Characterization of Cutting Force Induced Surface Shape Variation in Face Milling Using High-Definition Metrology1
Authors: Nguyen Hai Trong , Wang Hui , Hu S. Jack
Published: July 2013

High-definition metrology (HDM) systems with fine lateral resolution are capable of capturing the surface shape on a machined part that is beyond the capability of measurement systems employed in manufacturing plants today. Such surface shapes can precisely reflect the impact of cutting processes on surface quality. Understanding the cutting processes and the resultant surface shape is vital to high-precision machining process monitoring and control. This paper presents modeling and experiments of a face milling process to extract surface patterns from measured HDM data and correlate these patterns with cutting force variation. A relationship is established between the instantaneous cutting forces and the observed dominant surface patterns along the feed and circumferential directions for face milling. Potential applications of this relationship in process monitoring, diagnosis, and control are also discussed for face milling. Finally a systematic methodology for characterizing cutting force induced surface variations for a generic machining process is presented by integrating cutting force modeling and HDM measurements.
Hybrid Extrusion Force-Velocity Control Using Freeze-Form Extrusion Fabrication for Functionally Graded Material Parts
Authors: Deuser Bradley K. , Tang Lie , Landers Robert G. , Leu Ming C. , Hilmas Greg E.
Published: July 2013

Freeze-form extrusion fabrication (FEF) is an additive manufacturing (AM) process that uses an aqueous-based paste loaded with ceramic or metal powder to build complex, three-dimensional parts by extruding the material from a syringe onto a solid substrate in a subzero temperature environment. This paper describes the development of an intelligent control methodology for paste extrusion that utilizes a hybrid extrusion force-velocity controller. A plunger velocity controller was used to ensure a steady extrusion flow rate, and an extrusion force controller was developed to precisely regulate the starting and stopping of the extrusion process. Both controllers were coupled with a hybrid control scheme for extrusion-on-demand and air bubble release compensation. The plunger velocity controller successfully regulated the output material composition from two syringes, and the extrusion force controller precisely controlled the extrusion start and stop. Air bubble release compensation reduced the severity of extrusion gap defects and extrusion track thinning resulting from air bubble releases. Monolithic and functionally graded parts were fabricated to illustrate the functionality of the hybrid extrusion force-velocity controller.
Modeling and Analysis of Forces in Laser Assisted Micro Milling
Authors: Kumar Mukund , Chang Chia-Jung , Melkote Shreyes N. , Roshan Joseph V.
Published: July 2013

Laser assisted micro milling (LAMM) is capable of generating three dimensional microscale features in hard metals with lower cutting forces than conventional micro milling. To maximize the reduction in cutting forces, a mathematical model is required to understand the influence of different laser and machining parameters on the forces. Consequently, a physics-based force model is developed in this paper to predict the cutting forces when micro milling a hard metal using laser assist. LAMM experiments are carried out on 52,100 bearing steel (62 HRc) over a range of feed rates and laser powers to calibrate the force model. The results indicate that the model predicts the cutting force profile with good accuracy. This model is then used to study the influence of laser assist on cutting forces, which yields a better physical understanding of the LAMM process.
Diagnosing Multistage Manufacturing Processes With Engineering-Driven Factor Analysis Considering Sampling Uncertainty
Authors: Liu Jian , Jin Jionghua
Published: July 2013

A new engineering-driven factor analysis (EDFA) method has been developed to assist the variation source identification for multistage manufacturing processes (MMPs). The proposed method investigated how to fully utilize qualitative engineering knowledge of the spatial variation patterns to guide the factor rotation. It is shown that ideal identification can be achieved by matching the rotated factor loading vectors with the qualitative indicator vectors (IV) that are defined according to spatial variation patterns based on the design constraints. However, the random sampling variability may significantly affect the estimation of the rotated factor loading vectors, leading to the deviations from their true values. These deviations may change the matching results and cause misidentification of the actual variation sources. By using implicit differentiation approach, this paper derives the asymptotic distribution and the associated variance-covariance matrix of the rotated factor loading vectors. Therefore, by considering the effect of sample estimation variability, the variation sources identification problem is reformulated as an asymptotic statistical test of the hypothesized match between the rotated factor loading vectors and the indicator vectors. A real-world case study is provided to demonstrate the effectiveness of the proposed matching method and its robustness to the sample uncertainty.
Experimental Investigation of the Machinability of Epoxy Reinforced With Graphene Platelets
Authors: Arora Ishank , Samuel Johnson , Koratkar Nikhil
Published: July 2013

The objective of this research is to study the effect of graphene platelet (GPL) loading on the machinability of epoxy-based GPL composites. To this end, micro-milling experiments are conducted on composites with varying GPL content and their results are contrasted against that of plain epoxy. The material microstructure is characterized using transmission electron microscopy and scanning electron microscopy methods. Chip morphology, cutting force, machined surface morphology, and tool wear, are employed as the machinability measures for comparative purposes. At lower loadings of GPL (0.1% and 0.2% by weight), the deformation of the polymer phase plays a major role; whereas, at a higher loading of 0.3% by weight, the GPL agglomerates and interface-dominated failure dictates the machining response. The minimum chip thickness value of the composites decreases with an increase in GPL loading. Overall, the 0.2% GPL composite has the highest cutting force and the lowest tool wear.
Standalone Throughput Analysis on the Wave Propagation of Disturbances in Production Sub-Systems
Authors: Li Yang , Chang Qing , Brundage Michael P. , Xiao Guoxian , Biller Stephan
Published: July 2013

Standalone throughput (SAT) of a single station is one of the most widely used performance indexes in industry due to its clear definition, ease of evaluation and the ability to provide a guidance for continuous improvement in production systems. A complex multistage manufacturing system is typically segmented into several subsystems for efficient local management. It is important to evaluate performance of each subsystem to improve overall system productivity. However, the definition of standalone throughput of a production subsystem is not as clear as for a single station in current literatures or in practice, not to say an effective evaluation method. This paper deals with the standalone throughput of a serial production line segment. The definition and implication of standalone throughput of a line segment is discussed. A data driven method is developed based on online production data and is proved analytically under a practical assumption. In addition, the method is verified through simulation case studies to be an accurate and fast estimation of the standalone throughput of a production line segment.
Optimum Integration of a Bottoming Heat Recovery System in a Geothermal Power Plant Application
Authors: Ojo Collins O. , Pont Damien , DeSimone Andrea , Speirs Donald
Published: July 2013

Geothermal power is becoming more and more significant in the renewable power mix of several countries in the world. The thermal conditions of the geothermal fluids exhausting from geothermal power plants shows additional potential for improved heat utilization through the integration of a low heat recovery system. This paper addresses the optimum integration of an Organic Rankine Cycle (ORC) as bottoming cycle with a geothermal steam power plant as topping cycle over a range of geothermal fluid interface temperatures.

A reference geothermal based steam turbine power plant of 50MW capacity with indirect cycle configuration has been chosen for the study. At design point of the reference plant, optimized Organic Rankine Cycles based on three working fluids n-pentane, R123, and R245fa have been integrated at the exhaust of the geothermal fluid leaving the geothermal plant. An overall optimization of the power plant has been carried out by downsizing and over sizing the topping cycle with the integration of the bottoming cycle. One of the optimization variables for the overall plant is the interface temperature, which is a consequence of the resizing of the topping cycle. The procedure is repeated for the three different organic working fluids. By applying this procedure, it is then possible to know within a given interface temperature range, the organic working fluid that will give optimum plant performance.

The choice of ORC integration option is not only driven by the best techno-economic solution but additionally by environmental, health and safety compliance.
Exergy Versus Energy Analysis: Advantages and Disadvantages in Teaching of Thermodynamics
Authors: Goyings Ryan , Arnas Özer
Published: July 2013

In a course of thermodynamics, in general, and gas turbine analysis, in particular as stand alone or within a cogeneration situation, teaching within the concepts of energy or exergy has become controversial particularly since most teachers of thermodynamics at the undergraduate level are not too familiar with the advantages of exergy analysis and thus do not cover the material from that point of view. In this paper, we will go through the pedagogical implications of teaching thermodynamics using both approaches and attempt to show and convince people that exergetic analyses are superior to any other approach in the teaching of thermodynamics. The bottom line and the ultimate goal is the precise teaching of the subject matter.
Thermo-Economic Analysis of the Ultra-Supercritical 900 MW Power Unit With the Various Configurations of the Auxiliary Steam Turbine
Authors: Stępczyńska Katarzyna , Łukowicz Henryk , Dykas Sławomir , Rulik Sebastian
Published: July 2013

Coal-based electric power generation remains the basic source of obtaining energy. With increasing pressure to reduce CO2 emissions, improving power unit efficiency has become an issue of utmost significance. The development of technologies related to coal-fired power units does not focus solely on the steam parameters ahead of the turbine. Increasing the live steam parameters usually constitutes the greatest contribution to the rise in the efficiency of a power unit, but the sum of efficiency gains related to the application of other solutions can also be significant and can, in some cases, exceed the effects related to raising the temperature and steam pressure values. A paper presents thermodynamic and economic analysis of various configurations of the ultra-supercritical coal-fired 900 MW power unit with the auxiliary steam turbine. Main subject of research was a power unit considered within the Strategic Research Programme – Advanced Technologies for Energy Generation with the parameters of live and reheat steam: 30 MPa/650°C/670°C. The base configuration of the power unit has single steam reheat and electric drive boiler feed pump. Analysis of ultra-supercritical 900 MW power unit involves configuration with a single and double reheat. The following configurations of the auxiliary steam turbine will be presented and compared:

• extraction-backpressure steam turbine fed with steam from cold reheat line with bleed and steam outlet directed to the feed water heaters;

• extraction-backpressure steam turbine fed with steam from cold reheat line with bleed and steam outlet directed to the feed water heaters; the auxiliary turbine drives the boiler feed pump;

• backpressure turbine fed with steam from a hot reheat steam line operating in parallel with the intermediate-pressure turbine; the auxiliary turbine drives the boiler feed pump.

The analysis of the operation of the 900 MW unit was carried out for three load levels: for the nominal mass flow of live steam, and for the partial mass flow of 75% and 50%. For all presented solutions thermodynamic and economic analysis was performed, which has taken into account the charge for CO2 emissions.
Theoretical Interpretation of the CORDIER-Lines for Squirrel-Cage and Cross-Flow Fans
Authors: Willinger Reinhard
Published: July 2013

Squirrel-cage fans are centrifugal fans with forward-curved blades. A large number of short blades of thin circular arc sheet metal provide a low diameter drum-type rotor of high axial length. Cross-flow fans have a similar rotor design. However, the flow passes the rotor in radial direction two times. One consequence of the forward-curved blades is that there is more or less no pressure rise in the rotor and the casing has to convert the high absolute rotor exit velocity into a global pressure rise. Both types are used in applications requiring low size, relative high volume flow rates, low costs and low noise at the drawback of relative low efficiency. Volume flow rate, specific isentropic enthalpy difference, rotor outer diameter and rotational speed of a single stage fan can be transformed to speed number and diameter number. For axial, radial and mixed flow fans, a single relationship (CORDIER-diagram) exists and it is well accepted that this line represents “optimum” fan designs with high efficiency. The paper provides a theoretical interpretation of the CORDIER-lines for squirrel-cage and cross-flow fans, since they differ considerably from the classical relationship. Based on velocity triangles and energy transfer, CORDIER-line of squirrel-cage fans depends on absolute inlet flow angle, relative exit flow angle, rotor inlet to exit diameter ratio, relative axial rotor width and circumferential efficiency. Additionally, the CORDIER-line of cross-flow fans depends on the degree of admission. At a distinguished pressure coefficient, a maximum speed number is found, corresponding to maximum volume flow rate.
Simple Parametric Model for Quick Assessment of IGCC Performance
Authors: Gülen S. Can , Driscoll Ann V.
Published: July 2013

Even though almost all components of an Integrated Gasification Combined Cycle (IGCC) power plant are proven and mature technologies, the sheer number of them, the wide variety of competing technologies (e.g., gasifiers, gas clean-up systems, heat recovery options), system integration options (e.g., cryogenic air separation unit and the gas turbine) including the recent addition of carbon capture and sequestration (CCS) with its own technology and integration options render fundamental IGCC performance analysis a monumental task. Almost all published studies utilize highly complex chemical process and power plant heat balance software, including commercially available packages and in-house proprietary codes. This makes an objective assessment of comparable IGCC plant designs, performance (and cost) and other perceived advantage claims (IGCC versus other technologies, too) very difficult if not impossible.

This paper develops a coherent simplified parametric model based on fully physics-based grounds to be used for quick design performance assessment of a large variety of IGCC power plants with and without CCS. Technology parameters are established from complex model runs and supplemented by extensive literature search. The model is tested using published data to establish its confidence interval and is satisfactory to carry conceptual design analysis at a high level to identify promising alternatives, development areas and assess the realism in competing claims.
Available and Future Gas Turbine Power Augmentation Technologies: Techno-Economic Analysis in Selected Climatic Conditions
Authors: Bhargava R. K. , Branchini L. , Melino F. , Peretto A.
Published: July 2013

There exist a widespread interest in the application of gas turbine power augmentation technologies in both electric power generation and mechanical drive markets attributable to deregulation in the power generation sector, increased electric rates during peak demand period, and need for a proper selection of the gas turbine in a given application. In this study detailed thermo-economic analyses of various power augmentation technologies, implemented on a selected gas turbine, have been performed to identify the best techno-economic solution depending on the selected climatic conditions.

The presented results show that various power augmentation technologies examined have different payback periods. Such a techno-economic analysis is necessary for proper selection of a power augmentation technology.
An Innovative Inlet Air Cooling System for IGCC Power Augmentation: Part II—Thermodynamic Analysis
Authors: Morini Mirko , Pinelli Michele , Spina Pier Ruggero
Published: July 2013

Integrated Gasification Combined Cycles (IGCCs) are energy systems mainly composed of a gasifier and a combined cycle power plant. Since the gasification process usually requires oxygen as the oxidant, the plant also has an Air Separation Unit (ASU). Moreover, a producer gas cleaner unit is always present between the gasifier and the gas turbine. Since these plants are based on gas-steam combined cycle power plants they suffer from a reduction in performance when ambient temperature increases.

In this paper, an innovative system for power augmentation in IGCC plants is presented. The system is based on gas turbine inlet air cooling by means of liquid nitrogen spray. In fact, nitrogen is a product of the ASU, but is not always exploited. In the proposed plant, the nitrogen is first chilled and liquefied and then it can be used for inlet air cooling or stored for a postponed use.

This system is not characterized by the limits of water evaporative cooling (where the lower temperature is limited by air saturation) and refrigeration cooling (where the effectiveness is limited by pressure drop in the heat exchanger).

A thermodynamic model of the system is built by using a commercial code for the simulation of energy conversion systems. A sensitivity analysis on the main parameters (e.g. ambient air temperature, inlet air temperature difference, etc.) is presented. Finally the model is used to study the capabilities of the system by imposing the real temperature profiles of different sites for a whole year.
Risk-Based Assessment of Unplanned Outage Events and Costs for Combined-Cycle-Plants
Authors: Grace Dale , Christiansen Thomas
Published: July 2013

Unexpected outages and maintenance costs reduce plant availability and can consume significant resources to restore the unit to service. Although companies may have the means to estimate cash flow requirements for scheduled maintenance and on-going operations, estimates for unplanned maintenance and its impact on revenue are more difficult to quantify, and a large fleet is needed for accurate assessment of its variability. This paper describes a study that surveyed 388 combined-cycle plants based on 164 D/E-class and 224 F-class gas turbines, for the time period of 1995 to 2009. Strategic Power Systems, Inc. (SPS®), manager of the Operational Reliability Analysis Program (ORAP®), identified the causes and durations of forced outages and unscheduled maintenance and established overall reliability and availability profiles for each class of plant in 3 five-year time periods. This study of over 3,000 unit-years of data from 50 Hz and 60 Hz combined-cycle plants provides insight into the types of events having the largest impact on unplanned outage time and cost, as well as the risks of lost revenue and unplanned maintenance costs which affect plant profitability. Outage events were assigned to one of three subsystems: the gas turbine equipment, heat recovery steam generator (HRSG) equipment, or steam turbine equipment, according to the Electric Power Research Institute’s Equipment Breakdown Structure (EBS). Costs to restore the unit to service for each main outage cause were estimated, as were net revenues lost due to unplanned outages. A statistical approach to estimated costs and lost revenues provides a risk-based means to quantify the impact of unplanned events on plant cash flow as a function of class of gas turbine, plant subsystem, and historical timeframe. This statistical estimate of the costs of unplanned outage events provides the risk-based assessment needed to define the range of probable costs of unplanned events. Results presented in this paper demonstrate that non-fuel operation and maintenance costs are increased by roughly 8% in a typical combined-cycle power plant due to unplanned maintenance events, but that a wide range of costs can occur in any single year.
Demonstration of Supercritical CO2 Closed Regenerative Brayton Cycle in a Bench Scale Experiment
Authors: Utamura Motoaki , Hasuike Hiroshi , Ogawa Kiichiro , Yamamoto Takashi , Fukushima Toshihiko , Watanabe Toshinori , Himeno Takehiro
Published: July 2013

Power generation with a supercritical CO2 closed regenerative Brayton cycle has been successfully demonstrated using a bench scale test facility. A set of a centrifugal compressor and a radial inflow turbine of finger top size is driven by a synchronous motor/generator controlled using a high-speed inverter. A 110 W power generating operation is achieved under the operational condition of rotational speed of 1.15kHz, CO2 flow rate of 1.1 kg/s, and respective thermodynamic states (7.5 MPa, 304.6 K) at compressor and (10.6 MPa, 533 K) at turbine inlet. Compressor work reduction owing to real gas effect is experimentally examined. Compressor to turbine work ratio in supercritical liquid like state is measured to be 28% relative to the case of ideal gas. Major loss of power output is identified as rotor windage. It is found the isentropic efficiency depends little on compressibility coefficient. Off design performance of gas turbine working in supercritical state is well predicted by a Meanline program. The CFD analysis on compressor internal flow indicates that the presence of backward flow around the tip region might create a locally depressurized region leading eventually to the onset of flow instability.
Electrical Static Discharge in Turbo Machinery
Authors: Ross David A.
Published: July 2013

An industrial gas turbine had a reoccurring failure with its accessory gearbox. The gearbox would run for a few days and then begin to show increased vibrations. The vibration level would gradually increase until the turbine alarm and trip signals operated. Studies at the time suggested alignment and accessory coupling issues were the cause. After many realignments and gears being changed the problem persisted. Eventually the gearbox replaced as it was suspected the original had internal alignment issues. This proved to be unsuccessful and the problem continued.

At the time of the unit’s last overhaul it was discovered the generator’s non-drive-end bearings insulation had failed and could not be rectified in time for its return to operation. It was then decided to install a second rotor earthing brush to the non-drive-end of the generator.

The writer reviewed all the historical and current date including a site inspection of the plant. Initial inspection of the gear damage indicated excessive misalignment and gear tooth overload. Finally, examination of the shell bearing liners had indications consistent with Electrical Static Discharge [ESD]. This had been overlooked; interpretation of the marking was due to unusual misalignment and the gear shaft.
A Numerical Study Into the Effects of Bio-Synthetic Paraffinic Kerosine Blends With Jet-A Fuel for Civil Aircraft Engine
Authors: Mazlan Nurul Musfirah , Savill Mark , Kipouros Timos , Li Yi-Guang
Published: July 2013

Growing concerns regarding fluctuating fuel costs and pollution targets for gas emissions, have led the aviation industry to seek alternative technologies to reduce its dependency on crude oil, and its net emissions. Recently blends of bio-fuel with kerosine, have become an alternative solution as they offer “greener” aircraft and reduce demand on crude oil. Interestingly, this technique is able to be implemented in current aircraft as it does not require any modification to the engine. Therefore, the present study investigates the effect of blends of bio-synthetic paraffinic kerosine with Jet-A in a civil aircraft engine, focusing on its performance and exhaust emissions. Two bio-fuels are considered: Jatropha Bio-synthetic Paraffinic Kerosine (JSPK) and Camelina Bio-synthetic Paraffinic Kerosine (CSPK); there are evaluated as pure fuels, and as 10% and 50% blend with Jet-A. Results obtained show improvement in thrust, fuel flow and SFC as composition of bio-fuel in the blend increases. At design point condition, results on engine emissions show reduction in NOx, and CO, but increases of CO is observed at fixed fuel condition, as the composition of bio-fuel in the mixture increases.
Numerical Analysis of a Fogging System in a Gas Turbine
Authors: Jeanty Freddy , De Andrade Jesús , Croquer Sergio , Clarembaux Correa Jorge Luis , Asuaje Miguel
Published: July 2013

Air cooling via evaporation of water droplets injected at the compressor intake duct is the process known as Fogging System, which is among the most used technologies for increasing output power of gas turbines nowadays. The optimal design of this system must consider numerous variables, such as: air temperature (Ta), air relative humidity (RH), duct geometry, amount of water injected (mw), droplets size (Dd), and nozzles location. Since there are so many variables the flow under study is very complicated. In consequence the analytical determination of an optimal Fogging System design is not feasible. In this paper, a numerical model was developed in order to characterize the injection of water at the air intake duct of a Gas Turbine. First, the expressions characterizing the model were included in the CFD software ANSYS CFX v-11 and simulated in a simple geometry (rectangular duct). Validation of CFD results was carried out by comparison with experimental data. Good agreement between numerical results of a control case and experimental data was achieved (deviation < 2%). Then, the influence of key parameters such as: Ta, RH, Dd, mw over the performance of the air cooling system was investigated. Finally, the model was used to design a Fogging System for an existing 120 MW Gas Turbine. For this gas turbine operating under real conditions, the model predicts a net power increment of 2% [7].
Aerodynamic Analysis of a Humid Air Turbine Expander
Authors: Nyberg Björn , Thern Marcus , Genrup Magnus
Published: July 2013

This paper presents a reduced-order through-flow expander design for the Humid Air Turbine (HAT) also called the Evaporative Gas Turbine (EvGT). The HAT cycle is an innovative gas turbine cycle that uses humid air to enhance efficiency and power output. This means that there will be a higher water vapour content in the exhaust gases than for a simple cycle. This high water content affects the design of the HAT expander. The design of a wet expander is presented and compared with the results obtained with an expander working under dry exhaust gas conditions. The study was conducted using the reduced-order turbine design tool LUAX-T, developed at Lund University, which is freely available for academic use upon request. LUAX-T allows a flow-path analysis of the expander by specifying important flow-path parameters such as blade root stress and wall-hade angle. The HAT cycle enables cooling flow to the expander under different conditions and design differences for three different options are presented. The first cooling air bleeding point evaluated is the original position, where air is bled from the compressor discharge. The second position is just before the humidification tower, where the air has been cooled down to a low temperature. The third position is just after the humidification tower, where the air has been humidified thus changing its thermodynamic properties. Results in this paper shows that there is a need for an additional turbine stage in a humid expander compared to a dry expander. There are also results indicating that the compressor power can be reduced depending on which cooling strategy is used which can yield an increased total efficiency for a HAT cycle.
Aeroacoustic Optimization for Axial Fans With the Lattice-Boltzmann Method
Authors: Stadler Michael , Schmitz Michael B. , Ragg Peter , Holman David M. , Brionnaud Ruddy
Published: July 2013

A set of aeroacoustic optimization strategies for axial fans is presented. Their efficiency is demonstrated for small axial fans. Thereby, the generated noise could be reduced significantly while retaining or even improving the aerodynamic performance.

In particular, we discuss the following two optimization strategies in detail: Firstly, we consider the design of winglets using a parametric model for genetic optimization. The resulting winglet geometry helps to control the tip vortex over a large range of operating points, thereby reducing the generated noise. In addition, the power consumption of the fan could be reduced. Various choices of geometrical parameter sets for optimization are evaluated.

Secondly, we discuss the reduction of fan noise via contour optimized turbulators. For axial fans it is desirable to reduce sound emission across a broad operating range, not just for the design point. However, operation in off-design points may be accompanied by flow separation phenomena, which contribute predominantly to noise generation and reduce the aerodynamic performance of the fan. Turbulators can help to minimize these adverse effects. The advantages of various contoured turbulator geometries are discussed for off-design operating points.

The optimization of the above mentioned strategies was driven by aeroacoustic measurements via physical tests as well as numerical analysis based on the Lattice-Boltzmann method. The merits of either method are discussed with respect to the two optimization strategies.
Techno-Economic Analysis of Integrated Gasification Fuel Cell Power Plants Capturing CO2
Authors: Lanzini Andrea , Kreutz Thomas G. , Martelli Emanuele , Santarelli Massimo
Published: July 2013

This work analyzes the efficiency and economic performance of different configurations of a coal-fed Integrated Gasification Fuel Cell (IGFC) plant with CO2 capture. Our analysis evaluates novel configurations, providing a detailed economic assessment for each case.

The plants studied here are based on a pressurized Solid Oxide Fuel Cell (SOFC) based power cycle integrated with a Shell coal gasifier. The design variations focus on syngas cleaning and pre-processing upstream of the SOFC power island. In particular, we have designed, simulated and optimized three main system configurations; two with a partial methanation process upstream of the SOFC (‘TREMP’ and ‘HICOM’ cases, respectively) and one without (‘DIRECT’ case). Depending on the specific plant layout, carbon capture is accomplished either before or after the SOFC power island, or both.

The best performance, both thermodynamic and economic, was achieved by the HICOM case, whose coal-to-electricity conversion efficiency is 50.6% (lower heating value basis). In addition to outperforming the other IGFC configurations analysed, compared to a conventional IGCC-CCS plant, the ‘HICOM’ case produced over 20% reduction in the levelized-cost-of-electricity (LCOE) delivered by the power plant.
An Integrated Approach for the Multidisciplinary Design of Optimum Rotorcraft Operations
Authors: Goulos Ioannis , Pachidis Vassilios , d’Ippolito Roberto , Stevens Jos , Smith Chrissy
Published: July 2013

This work focuses on the development and application of a generic methodology targeting the design of optimum rotorcraft operations in terms of fuel burn, gaseous emissions and ground noise impact. An integrated tool capable of estimating the performance and emitted noise of any defined rotorcraft configuration within any designated mission has been deployed. A comprehensive and cost-effective optimization strategy has been structured. The methodology has been applied to two generic–baseline missions representative of current rotorcraft operations. Optimally designed operations for fuel burn, gaseous emissions and ground noise impact have been obtained. A comparative evaluation has been waged between the acquired optimum designs. The respective trade-off arising from the incorporation of flight paths optimized for different objectives has been quantified. Pareto front derived models for fuel burn and emitted noise have been structured for each mission. The Pareto models have been subsequently deployed for the design of operations optimized in a multidisciplinary manner.

The results have shown that the proposed methodology is promising with regards to achieving simultaneous reduction in fuel burn, gaseous emissions and ground noise impact for any defined mission. The obtainable reductions are found to be dependent on the designated mission. Finally, the potential to design optimum operations in a multidisciplinary fashion using only a single design criterion is demonstrated.
SGT5-8000H Experimental Test Results and Validation of High Fidelity 3D CFD
Authors: Bigalk Joachim , Biesinger Thomas , Broeker Marc , Buchal Tobias , Nürnberger Dirk , Schmidt Markus
Published: July 2013

The first Siemens SGT5-8000H had extensively been tested in Simple Cycle in Irsching during 2008 and 2009. About 3000 sensors had been installed for monitoring of the engine operation, the results demonstrated that all performance targets have been exceeded.

Detailed measurements of pressure, temperature and flow were performed in the turbine flow path at various locations in circumferential and radial direction. The experimental test results in the turbine flow path have been used for additional detailed analysis of the fluid dynamics operation by a High Fidelity 3D CFD whole turbine model. This standardized whole turbine CFD process forms an important element in the Siemens design chain. The model was set up with all geometrical details to resolve all relevant flow features such as shrouds, cavities, coating, fillets etc.

This paper summarizes and compares the experimental test results with predicted CFD design values for overall thermodynamic operation and aerodynamics data at turbine outlet.

Besides the results from the Simple Cycle prototype test phase, performance test results are presented from recent measurements during customer acceptance testing in Combined Cycle in 2011. These results show a confirmation of the previously measured overall performance values after complete rebuild and re commissioning of the engine for combined cycle operation.