bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Key Factors Influencing Histamine Formation and Accumulation in Fermented Sausages
Authors: Wang Xin Hui , Ren Hong Yang , Wang Wei , Bai Ting , Li Jun Xia
Published: March 2015

The key factors influencing histamine accumulation in fermented sausages were investigated. Although Lactobacillus salivarius R06 with positive amino acid decarboxylase was inoculated, histamine was not detected in batch A without histidine availability. About 52.1 mg/kg of histamine was observed in batch B with the addition of 80 mg/kg histidine. Under sterilized condition, both histamine production and histamine‐forming bacteria were not detected in batch C. About 37.6 mg/kg histamine and 4.19 log10 cfu/g of histamine‐forming bacteria were presented in batch D by a spontaneous fermentation. Approximately 60% of histamine in batch F was degraded by Staphylococcus epidermidis R11 with amine oxidase activity. Additionally, histamine content in fermented sausages increased with rising temperature at storage. These findings indicate that histidine availability as a limiting factor and the presence of histamine‐forming bacteria as indispensable factor are responsible for histamine formation. The strains with amine oxidase activity contribute to histamine accumulation reduction. Storage temperature has a direct effect on further formation of histamine in fermented sausages.

Practical Applications

High levels of histamine have been described in fermented sausages, which are a major problem for public health and food safety. Thus, it is worthwhile to improve knowledge of the factors involved in histamine accumulation to control histamine accumulation in fermented sausages. In this study, the key factors, including histidine availability, the presence of strains with decarboxylase activity, the presence of strains with amine oxidase activity and storage temperature influencing histamine accumulation in fermented sausages were investigated. These findings indicate that the key actions to prevent histamine accumulation must be addressed toward a reduction of the numbers of undesirable microorganisms and histamine‐forming microorganisms to control the proteolytic and decarboxylase activities and use of adjunct cultures with amine oxidase activity to degrade histamine. Additionally, fermented sausages should be stored immediately at low temperature after ripening.
A National Assessment of Colleges and University School Health Education Methods Courses
Authors: Fisher Christine M. , Price James H. , Telljohann Susan K. , Dake Joseph A.
Published: March 2015

BACKGROUND

Across the United States, school health education programs provide a wide variety of knowledge and skills to their students. There are currently no guidelines for school health methods courses.

METHODS

Using a 2‐wave mailing followed by a third wave e‐mail reminder, a final population of 226 university school health methods instructors at school health preparation programs were surveyed.

RESULTS

A total of 138 completed surveys (61%) were returned. The topics taught in school health education methods courses emphasized the most included aligning objectives, instruction, and assessment (79%); development of lesson plans (73%); teaching methods that engage learners (72%); and application of the National Health Education Standards and performance indicators (69%). The content taught and how the instructors assessed their students differed statistically by 1 or more of the following: whether they had a health education degree, had experience teaching in the public schools, and if their program was accredited.

CONCLUSIONS

This study provides information regarding what school health methods instructors across the United States are teaching in their classes. Using this information as a baseline can serve as a guide for preservice faculty teaching a school health methods course.
Families' Experiences of Seeking Out‐of‐Home Accommodation for Their Adult Child With an Intellectual Disability
Authors: Grey Jillian M. , Griffith Gemma M. , Totsika Vasiliki , Hastings Richard P.
Published: March 2015

Research exploring the experiences of families during the process of seeking out‐of‐home accommodation for an adult son or daughter with intellectual disability is scarce. A study was undertaken to examine this process. Nine families currently seeking out‐of‐home accommodation for their adult son or daughter were interviewed and interview data were analyzed using thematic analysis. Two main themes were identified: (1) reasons for seeking housing and (2) experiences of seeking housing. Parents' aging and increased health problems along with the offspring's wish for greater independence were the main reasons for seeking out‐of home accommodation. Experiences of looking for a house were not straightforward in that parents often wanted to plan ahead but were prevented from doing so as the housing system prioritizes “housing crises.” Findings showed that families experienced seeking housing as stressful and frustrating and would like to see social care and housing professionals acknowledge them as collaborative partners in the process. The authors conclude there also needs to be greater clarity of expectation of the duration of finding suitable accommodation, a process that needs to be started early in a young adult's life.
Long‐term outcome of liver transplant patients with Budd‐Chiari syndrome secondary to myeloproliferative neoplasms
Authors: Potthoff Andrej , Attia Dina , Pischke Sven , Mederacke Ingmar , Beutel Gernot , Rifai Kinan , Deterding Katja , Heiringhoff Karlheinz , Klempnauer Jürgen , Strassburg Christian P. , Manns Michael P. , Bahr Matthias J.
Published: March 2015

Background

A considerable proportion of patients receiving liver transplants for Budd‐Chiari syndrome (BCS) suffer from myeloproliferative neoplasms (MPN). This study evaluated the long‐term prognosis of liver‐transplanted patients with BCS secondary to MPN and the effect of immunosuppression on MPN progression.

Methods

A total of 78 patients with BCS were evaluated between 1982 and 2013. Of those, 40 patients suffered from polycythaemia vera (PV) and essential thrombocythaemia (ET). One patient had primary myelofibrosis (PMF). All patients received the standard immunosuppressive regimen. We retrospectively evaluated the long‐term survival, clinical course and laboratory parameters of patients with MPN.

Results

Exactly 29/41 patients (71%) with MPN survived ≥ 3 years [mean age 36 ± 11 years; females n = 27 (93%)]. Mean follow‐up after orthotopic liver transplantation (OLT) was 12.4 ± 7.3 years (range 3–28 years). Five‐ and 10‐year survival rates were not significantly different in patients with and without MPN (P = 0.81 and P = 0.66 respectively) or in patients with PV and ET (P = 0.29 and P = 0.55 respectively). Thrombosis and bleeding developed in 7/29 (24%) long‐term MPN survivors with no significant difference between ET and PV (P = 0.18). In the long‐term follow‐up, there was no evidence of progression to overt myelofibrosis or acute myeloid leukaemia (AML). In the uni‐ and multivariate Cox‐regression analyses, MPN did not influence survival after OLT.

Conclusions

Budd‐Chiari syndrome patients with and without underlying MPN had similar long‐term survival rates after OLT. There was no evidence of enhanced progression of MPN after OLT secondary to immunosuppressive therapy. However, major haemorrhage and recurrent thrombosis contributed to morbidity and mortality after OLT in those patients.
Isolated central vestibular syndrome
Authors: Kim Sung‐Hee , Park Seong‐Ho , Kim Hyo‐Jung , Kim Ji‐Soo
Published: March 2015

Isolated vestibular syndrome may occur all along the vestibular pathways from the peripheral labyrinth to the brain. By virtue of recent developments in clinical neurotology and neuroimaging, however, diagnosis of isolated central vestibulopathy is increasing. Here, we review five distinct syndromes of isolated central vestibular syndrome from lesions restricted to the vestibular nuclei, the nucleus prepositus hypoglossi, the flocculus, the tonsil, and the nodulus, and introduce a new vestibular syndrome from isolated involvement of the inferior cerebellar peduncle. Decreased responses to head impulses do not exclude a central lesion as a cause of isolated vestibular syndrome. Brain imaging, including diffusion‐weighted magnetic resonance imaging (MRI), may be falsely negative during the acute phase in patients with isolated vestibular syndrome because of a stroke. Central signs should be sought carefully in patients with isolated vertigo, even when the patients show the features of peripheral vestibulopathy and negative MRIs. Recognition of these isolated central vestibular syndromes would aid in defining the lesions responsible for various vestibular manifestations in central vestibulopathy.
Foliar terpenoid levels and corresponding gene expression are systemically and differentially induced in Eucalyptus grandis clonal genotypes in response to Chrysoporthe austroafricana challenge
Authors: Visser E. A. , Mangwanda R. , Becker J. V. W. , Külheim C. , Foley W. J. , Myburg A. A. , Naidoo S.
Published: March 2015

Induction of systemic defences to fungal pathogens is well described in model plant systems, but not extensively studied in large woody perennials. Systemic induced defences in long‐lived tree species, such as Eucalyptus grandis, could provide resistance against subsequent biotic challenges. Terpenoids are a class of plant‐specialized metabolites implicated in defence against herbivores and pathogens. The aim of this study was to characterize the systemic induction of terpenoids in E. grandis clones challenged with the fungal pathogen Chrysoporthe austroafricana. Ramets of E. grandis clones previously classified as moderately resistant (TAG5) and susceptible (ZG14) were inoculated with C. austroafricana on the main stem, with mock‐inoculated ramets to serve as controls. Leaf tissue was harvested 3 days post‐inoculation and terpenoid levels were measured using gas chromatography coupled with mass spectrometry. Foliar mRNA abundance profiles of four candidate terpenoid biosynthesis pathway genes were compared in inoculated and mock‐inoculated ramets of each genotype. Monoterpene levels differed between clonal genotypes and p‐cymene was induced systemically in TAG5. Expression profiling of geranyl pyrophosphate synthase (EgrGPPS), farnesyl pyrophosphate synthase (EgrFPPS2), myrcene synthase (EgrTPS084) and β‐caryophyllene synthase (EgrTPS038) show induction of transcripts involved in terpenoid biosynthesis in leaves following pathogen challenge on the main stem. Together these results suggest that resistant and susceptible Eucalyptus genotypes may have different constitutive and induced terpenoid profiles. The significance of the systemic induction of terpenoid levels in TAG5 and terpenoid biosynthesis transcripts in both genotypes in response to C. austroafricana challenge in the stem, and their role in defence against secondary biotic attack, remains to be determined.
Different Factors for Different Causes: Analysis of the Spatial Aggregations of Fire Ignitions in Catalonia (Spain)
Authors: González‐Olabarria José Ramón , Mola‐Yudego Blas , Coll Lluis
Published: March 2015

The present study analyzes the effects of different socioeconomic factors on the frequency of fire ignition occurrence, according to different original causes. The data include a set of documented ignition points in the region of Catalonia for the period 1995–2008. The analysis focused on the spatial aggregation patterns of the ignitions for each specific ignition cause. The point‐based data on ignitions were interpolated into municipality‐level information using kernel methods as the basis for defining five ignition density levels. Afterwards, the combination of socioeconomic factors influencing the ignition density levels of the municipalities was analyzed for each documented cause of ignition using a principal component analysis. The obtained results confirmed the idea that both the spatial aggregation patterns of fire ignitions and the factors defining their occurrence were specific for each of the causes of ignition. Intentional fires and those of unknown origin were found to have similar spatial aggregation patterns, and the presence of high ignition density areas was related to high population and high unemployment rates. Additionally, it was found that fires originated from forest work, agricultural activities, pasture burning, and lightning had a very specific behavior on their own, differing from the similarities found on the spatial aggregation of ignitions originated from smokers, electric lines, machinery, campfires, and those of intentional or unknown origin.
Small Area Estimation to Quantify Discontinuities in Repeated Sample Surveys
Authors: Brakel Jan A. , Buelens Bart , Boonstra Harm-Jan
Published: March 2015

During redesigns of repeated surveys, the old and new approaches are often conducted in parallel to quantify discontinuities that are initiated by modifications in the survey process. For budget limitations, the sample size allocated to the alternative approach is often considerably smaller compared with the regular survey that is used for official publication. In this paper, small area estimation techniques are considered to improve the accuracy of domain estimates obtained under the alternative approach. Besides auxiliary information that is available from administrations, direct domain estimates available from the regular survey are useful auxiliary variables to construct model-based small area estimators. These methods are applied to a redesign of the Dutch Crime Victimization Survey.
A Comparison of Textbooks' Presentation of Fractions
Authors: Cady Jo A. , Hodges Thomas E. , Collins R. Lee
Published: March 2015

In the United States, fractions are an important part of the middle school curriculum, yet many middle school students struggle with fraction concepts. Teachers also have difficulty with the conceptual understanding needed to teach fractions and rely on textbooks when making instructional decisions. This reliance on textbooks, the idea that teaching and learning of fractions is a complex process, and that fraction understanding is the foundation for later topics such as proportionality, algebra, and probability, makes it important to examine the variation in presentation of fraction concepts in U.S. textbooks, especially the difference between traditional and standards‐based curricula. The purpose of this study is to determine if differences exist in the presentation of fractions in conventional and standards‐based textbooks and how these differences align with the recommendations of National Council of Teachers of Mathematics, Common Core State Standards, and the research on the teaching and learning of fractions.
Teachers Describe Epistemologies of Science Instruction Through Q Methodology
Authors: Barnes Caitlin , Angle Julie , Montgomery Diane
Published: March 2015

Creating scientifically literate students is a common goal among educational stakeholders. An understanding of nature of science is an important component of scientific literacy in K‐12 science education. Q methodology was used to investigate the opinions of preservice and in‐service teachers on how they intend to teach or currently teach science. Q methodology is a measurement tool designed to capture personal beliefs. Participants included 40 preservice and in‐service elementary and secondary science teachers who sorted 40 self‐referential statements regarding science instruction. The results identified three epistemologies toward teaching science: A Changing World, My Beliefs, and Tried and True. Participants with the A Changing World epistemology believe evidence is reliable, scientific knowledge is generated in multiple ways, and science changes in light of new evidence. The My Beliefs epistemology reflects that scientific knowledge is subject to change due to embedded bias, science is affected by culture and religion, and evolution should not be taught in the classroom. The Tried and True epistemology views a scientific method as an exact method to prove science, believes experiments are crucial for scientific discoveries, absolute truth exists in scientific knowledge, and society and cultural factors can be eliminated from investigations. Implications for preservice teacher education programs and in‐service teacher professional development are addressed.
Implications of Informal Education Experiences for Mathematics Teachers' Ability to Make Connections Beyond Formal Classroom
Authors: Popovic Gorjana , Lederman Judith S.
Published: March 2015

The Common Core Standard for Mathematical Practice 4: Model with Mathematics specifies that mathematically proficient students are able to make connections between school mathematics and its applications to solving real‐world problems. Hence, mathematics teachers are expected to incorporate connections between mathematical concepts they teach and their applications to solving problems arising in real‐world situation. Clearly, it is assumed that the teachers themselves are able to make such connections. On the other hand, research shows that mathematics teachers find it difficult to make those connections. In this paper, we present the results of the study that investigated the ways in which exploring mathematics in informal sites, and in particular science museum, assist teachers with making connections between school mathematics and its applications in real world.
Centers for the Kukles homogeneous systems with odd degree
Authors: Giné Jaume , Llibre Jaume , Valls Claudia
Published: March 2015

For the polynomial differential system , , where is a homogeneous polynomial of degree there are the following two conjectures raised in 1999. (1) Is it true that the previous system for has a center at the origin if and only if its vector field is symmetric about one of the coordinate axes? (2) Is it true that the origin is an isochronous center of the previous system with the exception of the linear center only if the system has even degree? We prove both conjectures for all odd.
Théorèmes de type Fouvry–Iwaniec pour les entiers friables
Authors: Drappeau Sary
Published: March 2015

An integer $n$ is said to be $y$-friable if its largest prime factor $P^{+}(n)$ is less than $y$. In this paper, it is shown that the $y$-friable integers less than $x$ have a weak exponent of distribution at least $3/5-{\it\varepsilon}$ when $(\log x)^{c}\leqslant x\leqslant x^{1/c}$ for some $c=c({\it\varepsilon})\geqslant 1$, that is to say, they are well distributed in the residue classes of a fixed integer $a$, on average over moduli ${\leqslant}x^{3/5-{\it\varepsilon}}$ for each fixed $a\neq 0$ and ${\it\varepsilon}>0$. We apply this to the estimation of the sum $\sum _{2\leqslant n\leqslant x,P^{+}(n)\leqslant y}{\it\tau}(n-1)$ when $(\log x)^{c}\leqslant y$. This follows and improves on previous work of Fouvry and Tenenbaum. Our proof combines the dispersion method of Linnik in the setting of Bombieri, Fouvry, Friedlander and Iwaniec with recent work of Harper on friable integers in arithmetic progressions.
Shock Formation in Overexpanded Tip Leakage Flow
Authors: Moore John , Elward Kevin M.
Published: March 2015

Shock formation due to overexpansion of supersonic flow at the inlet to the tip clearance gap of a turbomachine has been studied. The flow was modelled on a water table using a sharp-edged rectangular channel. The flow exhibited an oblique hydraulic jump starting on the channel sidewall near the channel entrance. This flow was analyzed using hydraulic theory. The results suggest a model for the formation of the jump. The hydraulic analogy between free surface water flows and compressible gas flows is used to predict the location and strength of oblique shocks in analogous tip leakage flows. Features of the flow development are found to be similar to those of compressible flow in sharp-edged orifices. Possible implications of the results for high-temperature gas turbine design are considered.
Investigation of the Vibration of a Blade With Friction Damper by HBM
Authors: Wang J. H. , Chen W. K.
Published: March 2015

The friction damper has been widely used to reduce the resonant vibration of blades. The most commonly used methods for studying the dynamic behavior of a blade with a friction damper are direct integration methods. Although the harmonic balance method (HBM) is a well known method for studying nonlinear vibration problems, generally only a one–term approximation has been proposed to study the nonlinear vibration of a frictionally damped blade. In this work; a procedure of the HBM with a multi–term approximation is proposed. The results show that the steady state response and other related behavior of a frictionally damped blade can be predicted accurately and quickly by the HBM with a multi–term approximation.
Foothills Decompression/Recompression Facilities Unique Power Recovery Application in Gas Pipelines
Authors: Kitt Stanley R. , Rose Bruce D.
Published: March 2015

Foothills Pipe Lines Ltd. is the Canadian sponsor of the Alaska Natural Gas Transportation System (ANGTS), a pipeline project selected in Canada and the United States as the means for transporting Alaskan gas reserves to the lower 48 United States. Currently, certain Prebuild portions of the ANCTS are in operation delivering Canadian gas to U.S. markets.

Recent system expansion of the Eastern Leg Prebuild to accommodate increased Canadian gas exports entailed the construction of Decompression/Recompression facilities at Empress, Alberta to enable high pressure operation of the Foothills pipeline while maintaining gas stripping at existing low pressure extraction plants. The general process of the Decompression/Recompression facilities involves the expansion of high pressure pipeline gas to conditions acceptable to the low pressure extraction plants, then the recompression of the residue gas for return to the pipeline at original pressure. By directing the inlet gas through turbo expanders coupled to brake compressors, a substantial portion of the expansion energy is captured and used in providing the first stage of gas recompression. Including supplemental conventional compression, the Decompression/Recompression facilities are capable of providing approximately 37 MW (50 000 HP) for continuous gas recompression.

Although power recovery with turbo expanders is relatively common in the gas processing industry, such application for gas recompression in large gas pipelines is unique. This technical paper describes the Foothills Decompression/Recompression facilities with their utilization of turbo expanders for pipeline recompression service, emphasizing the process design as well as the characteristics of the rotating equipment.
Evaluation of Leasing Versus Purchasing Water Treatment Equipment for Cogeneration Projects
Authors: Gagnon S. R. , Guidotti H. A.
Published: March 2015

The need for high purity water for both water and steam injection into gas turbines has become more evident over the past twenty years. Changing environmental concerns and the need for highly trained personnel have prompted a closer look at permanently installed water treatment systems versus leased, mobile systems. Water availability, water quality, discharge limitations, and licensing have all become key issues in new system development.

Traditional permanently installed water treatment systems with on site regeneration of resins must now be evaluated against new options available to developers and operators of gas turbine installations. The leased mobile systems, as evaluated in this paper, are trailer mounted, self contained units, which will have all regeneration of resins done off site at the vendor’s facility. The units are under the direct control of the vendor, with the only responsibility of the site being the delivery of power and water to the trailers. For clarity, this paper will use the term “Permanent System” to refer to a traditional water treatment plant installation under the control of the plant, and the term “Mobile System” to refer to a leased mobile system under the control of the system vendor.

This paper will provide conceptual designs for water treatment systems at two sites, for both permanently installed and leased mobile water treatment systems. It will examine the cost impact that each option has on installation, operation and maintenance. Different modes of operation will be examined to determine the optimal system. The results of this optimization will consist of an illustration of equipment, operating cost, capital cost, and advantages and disadvantages of purchasing versus leasing.

This paper does not address the leasing of a permanent water treatment system in lieu of purchasing the permanent equipment outright, as that would merely be an exercise in financing options.
Optimized Ultra High Efficiency Filter for High-Efficiency Industrial Combustion Turbines
Authors: Yu Henry H. S. , Gdulding Cecil H.
Published: March 2015

For modern high efficiency aero-derivative combustion turbines there is an urgent need for ultra high efficiency inlet air filters with a low initial pressure drop. Often high efficiency filters are associated with high pressure drop (e.g. HEPA). In this paper, through a mathematical analysis and design optimization, a new type of ultra high efficiency (>97% for 0.3 μm diameter particle), high capacity, and low pressure drop (0.5” w.g. at face velocity of 500 fpm) combustion turbine filter, particularly suitable for applications in the urban environment is presented.

In mathematical analysis, a closed form analytical solution from Navier-Stoke’s equation for air flow between filter pleat spacing with uniform mass addition and extraction is applied to each finite element along the pleat channel. The optimum pleat aspect ratio is obtained by combining the expressions for the axial pressure gradient for upstream channel with mass extraction, the axial pressure gradient for downstream channel with mass addition, and the filter media flow characteristics for finite elements along the filter pleat channel with varying wall flow rates.
Civil Aircraft Challenges in Engine/Airframe Integration
Authors: Hamilton Gordon L. , Welge H. Robert
Published: March 2015

The demand for economic and efficient aircraft has focused more attention on the integrated design process. In addition, supersonic flight speeds pose unique design constraints on both propulsion and airframe technologies. This paper addresses some of the key features of engine/airframe integration in both the subsonic and supersonic flight regimes, and addresses both design and test implications.
Self-Excited Vibration of Plugs in Regulating Valves
Authors: Vlček V. , Dobiăš I.
Published: March 2015

Experimental research aimed at the increasing regulating valve reliability is described. In particular, vibration measurements of elastically supported plugs on axisymmetric models and on models with rectangular cross-section of the flow field (“2D-model”) are described and discussed. Both models, geometrically similar with regard to the passage area, were designed so that the elasticity of the plug support could be simulated.

It has been shown that, in certain bands of the working parameters, self-excited transversal vibration of the plug appears. The boundaries of the self-excitation occurence have a certain hysteresis, which depends on working parameters. They are also influenced by the shape of the plug base. In the 2D-model, flow visualization and quantitative optical measurements, using the Mach-Zehnder interferometer, were made simultaneously with the vibration measurements. The influence of the plug vibration on breaking of vortices in the diffuser is shown.
An Infrared Pyrometry System for Monitoring Gas Turbine Blades: Development of a Computer Model and Experimental Results
Authors: De Lucia Maurizio , Lanfranchi Carlo
Published: March 2015

This work describes the development of a computer modeling system for infrared pyrometry measurement of gas turbine blade temperature. The model accurately evaluates apparent target emissivity and temperature on the basis of the radiation heat fluxes exchanged at steady-state conditions. Experimental testing conducted on gas turbine models in a controlled-temperature furnace has shown that the reliability of the target emissivity prediction effectively reduces one of the major causes of error in infrared pyrometry.
Surface-Curvature-Distribution Effects on Turbine-Cascade Performance
Authors: Korakianitis Theodosios , Papagiannidis Paschalis
Published: March 2015

The manufacturing accuracy of turbine blades is judged by the difference between designed and produced location of each point around the airfoils. This paper shows that the design-point and off-design-point aerodynamic and heat transfer performance of turbine cascades is affected significantly by the distribution of curvature along the suction and pressure surfaces, and less significantly by the exact location of each one point. The performance of turbine blades designed with continuous slope of curvature distribution, and with slight discontinuities in the slope of curvature, are examined using a computer program for various design and off-design flow conditions. The accuracy of the computations is checked by comparison of computational results with cascade solutions of known experimental output. It is concluded that the accuracy in local curvature is just as important as the design-location-by-manufactured-location accuracy of each point on the blade.
The Effects of Blade Loading in Radial and Mixed Flow Turbines
Authors: Chen H. , Abidat M. , Baines N. C. , Firth M. R.
Published: March 2015

Understanding of the effects of blade loading and blade number in radial and mixed flow turbines is often based on analogies with axial turbine cascade tests or centrifugal compressors rather than direct measurement. In this paper test results from a series of similar mixed flow turbines are described. The turbine rotors differ only in blade number or inlet incidence variation. The results comprise performance data and hub and shroud pressure measurements, from which it is possible to deduce parameters such as incidence angle with good accuracy. In addition, predictions of blade loading using three-dimensional computations are shown. The results are correlated against a loading coefficient and a slip factor, both derived for the general case of a mixed flow turbine. The influence of these parameters on the performance of the tested turbines, and for comparison of other radial turbines, is shown.
The Design and Evaluation of a High Pressure Ratio Radial Turbine
Authors: Pullen K. R. , Baines N. C. , Hill S. H.
Published: March 2015

A single stage, high speed, high pressure ratio radial inflow turbine was designed for a single shaft gas turbine engine in the 200 kW power range. A model turbine has been tested in a cold rig facility with correct simulation of the important non-dimensional parameters. Performance measurements over a wide range of operation were made, together with extensive volute and exhaust traverses, so that gas velocities and incidence and deviation angles could be deduced. The turbine efficiency was lower than expected at all but the lowest speed. The rotor incidence and exit swirl angles, as obtained from the rig test data, were very similar to the design assumptions. However, evidence was found of a region of separation in the nozzle vane passages, presumably caused by a very high curvature in the endwall just upstream of the vane leading edges. The effects of such a separation are shown to be consistent with the observed performance.
The LM6000 Gas Turbine as a Mechanical Drive Power Source
Authors: Casper R. L. , Spector R. B.
Published: March 2015

The LM6000 Gas Turbine was formally introduced at the IGTI Gas Turbine Conference in Brussels in 1990. It was immediately accepted for power generation/cogeneration applications; however, inquiries were received concerning the use of the LM6000 gas turbine for mechanical drive applications. These inquiries included the amount of power available with decreasing gas turbine speed, breakaway torque capability and resonant free operation over a broad speed range.

This paper discusses the engineering studies performed to ensure that the LM6000 will be a suitable power source for mechanical drive applications in the 30–40 MW power range.
Studies of Jet Thermal Stability in a Flowing System
Authors: Heneghan S. P. , Martel C. R. , Williams T. F. , Ballal D. R.
Published: March 2015

A flowing, single-pass heat exchanger test rig, with a fuel capacity of 189 litres, has been developed to evaluate jet fuel thermal stability. This so called, “Phoenix Rig” is capable of supplying jet fuel to a 2.15 mm I.D. tube at a pressure up to 3.45 MPa, fuel temperature up to 900K, and a fuel-tube Reynolds number in the range 300–11,000. Using this test rig, fuel thermal stability (carbon deposition rate), dissolved oxygen consumption, and methane production were measured for three baseline jet fuels and three fuels blended with additives. Such measurement were performed under oxygen-saturation or oxygen-starved conditions.

Tests with all of the blended fuel samples showed a noticeable improvement in fuel thermal stability. Both block temperature and test duration increased the total carbon deposits in a nonlinear fashion. Interestingly, those fuels that need a higher threshold temperature to force the consumption of oxygen exhibited greater carbon deposits than those that consume oxygen at a lower temperature. These observations suggested a complicated relationship between the formation of carbon deposits and the temperature-driven consumption of oxygen. A simple analysis, based on a bi-molecular reaction rate, correctly accounted for the shape of the oxygen consumption curve for various fuels. This analysis yielded estimates of global bulk parameters of oxygen consumption. The test rig yielded quantitative results which will be very useful in evaluating fuel additives, understanding the chemistry of deposit formation, and eventually developing a global chemistry model.
Multi-Jet Annulus/Core-Flow Mixing—Experiments and Calculations
Authors: Baker S. J. , McGuirk J. J.
Published: March 2015

LDV measurements are reported of the flow-field associated with a single row of radially injected jets penetrating a core-tube flow. Emphasis is placed on the influence of small feed-annulus height on jet entry conditions and resulting trajectories and mixing patterns. Conditions of unstable jet behaviour, with strong vortex patterns in the jet holes, were observed for small annulus heights and high annulus velocities. Most measurements were however taken under stable conditions to allow the data to be used in a CFD validation exercise. Significant differences in the strength of backflow generated at jet impingement and in the turbulence field in the immediate hole vicinity were observed for different annulus height/core diameter ratios. These were accompanied by jet trajectory and annulus flow structure changes. Measurements of all 3 mean velocity components and associated normal stresses enabled the data to be utilised to assess a 3D CFD calculation incorporating a k-ε turbulence closure. The strength of forward and back flow generated at impingement was accurately predicted when the QUICK discretisation scheme was used. However, the size of upstream vortex was overpredicted. As expected using an eddy viscosity model the turbulence field at jet impingement and in the hole vicinity was not correctly reproduced. The turbulence generation in the flow approaching the hole was greatly overestimated by the turbulence model used.
Effect of Initial Fuel Distribution and Subsequent Mixing on Emissions From Lean, Premixed Flames
Authors: Maughan J. R. , Warren R. E. , Tolpadi A. K. , Roloff T. P.
Published: March 2015

Results presented here illustrate how optimizing the fuel distribution at injection reduces the subsequent mixing needed for ultralow emissions in lean, premixed gaseous flames. An experimental facility was developed for bluff body stabilization of a high pressure natural gas flame at the exit of a 4” diameter mixing tube. Fuel was injected through two concentric ring manifolds. NOx and CO drop dramatically from diffusion flame to perfectly premixed levels with increasing mixing distance. Furthermore, for each mixing distance, there is an optimum fuel split that results in minimum NOx and CO emissions. Computational fluid dynamics and laser sheet flow visualization show the recirculation zones and fluid mixing that affect fuel injection requirements. Although improved fuel injection and greater mixing will both drive the NOx-CO curve to the origin, improving the initial fuel distribution reduces the requirement for subsequent mixing.
Achieving Manufacturing Excellence for Gas Turbine Components Through Focused Implementation of Technology
Authors: Hayner Chester
Published: March 2015

This paper explains how focused implementation of a broad range of technologies was used as the key strategy resulting in the establishment of highly efficient, dedicated facility for manufacture of gas turbine disk, hub, and drum rotor components.

The physical and operational constraints associated with the conversion of an existing operating facility, along with the rigid time constraints, required a carefully phased and integrated plan.

Reviews and tradeoffs of each of the many available manufacturing technologies are discussed and those selected, such as flowline units, group technology, rule based design/manufacturing and product improvement teams are explained in the context of their implementation phase-in.

Before and after performance results are provided and on-going enhancements of this manufacturing system are covered.
Boundary Layer Effects on the Transonic Flow in a Straight Turbine Cascade
Authors: Štastný M. , Šafařík P.
Published: March 2015

The analysis presented here deals with two subjects related to the transonic flow in a straight turbine cascade:

1) turbulization of the suction side boundary layer and its subsequent development along the profile

2) influence of side wall boundary layers on cascade flows.

The turbulization effect of supersonic compression on the boundary layers which accompany transonic expansion on the suction side of the profile is investigated by independent methods. Both the experimental results and the calculation confirm the loss of stability of the laminar boundary layer and its subsequent transition into turbulence in the region of an adverse pressure gradient. Also the possibility of reverse transition of turbulent boundary layer in a subsequent strong favourable pressure gradient is investigated.

The contraction effect of the wind tunnel side wall boundary layers is expressed by means of the AVDR factor over a wide range of flow regimes determined by the incidence angle and the Mach number. A correction of the exit flow angle from the cascade is made to obtain a purely 2D flow although it is apparent that the measured exit angle values and the exit angle obtained for a 2D flow differ considerably.
Transonic Flow Through Turbine Cascades With Nonuniform Pitch
Authors: Kurz R.
Published: March 2015

The flow behind linear turbine cascades with uniform and nonuniform pitches was investigated both theoretically and experimentally.

A calculation procedure based on an Euler–code for nonuniform pitch to chord ratios is presented. Experimental data were obtained by using a Laser–2–Focus measurement system and Kiel probes. Outlet Laval numbers range from 0.7 to 1.0, corresponding to Reynolds numbers from 380,000 to 700,000. The pitch–to–chord ratio of the investigated configurations reaches from 0.771 to 0.877.
Non-Steady Flow Measurements Inside a Hydrodynamic Torque Converter by Hot-Film Anemometry
Authors: Browarzik V. , Grahl K. G.
Published: March 2015

The overall-characteristics of hydrodynamic torque converters have been discussed often, although there is little knowledge about the flow field inside the circuit. During former investigations at our institute flow measurements have been made and a CFD-program was developed to calculate the flow through the guide vanes and the pump impeller.

Our present studies now examine the non-steady flow field at the inlet and outlet of the pump and the turbine impeller by means of hot-film anemometry and a computer based measuring system. The measuring techniques have been developed and now measurements are made at different operating points. Later the measurements will be performed with special regard to non-steady changes of operating conditions.

The paper describes the test facilities, the measuring equipment and the techniques used to evaluate the measured data. First results of test measurements are presented.
Optimization of a Multistage Axial Compressor Stochastic Approach
Authors: Egorov I. N.
Published: March 2015

A procedure of a multistage axial compressor (MAC) parameters optimization in stochastic setting has been offered. The procedure allows to obtain a stable solution from the point of view of its practical realization. A concept of robustness (stability) of turbomachine optimum design has been introduced, and the criteria of stability degree evaluation of complex technical objects optimum solution have been also suggested.

With reference to determining optimum laws to control the rows of MAC, modeled in 2-D axisymmetric setting, there are presented the results of the comparative analysis of the solutions obtained both with using the traditional (deterministic) approach and the proposed stochastic setting, which allows to increase the possibility to realize the technical solution by more than two times. Analysis of the results shows that the value of optimization criterion obtained in stochastic setting doesn’t practically worsen the value of optimization criterion obtained in deterministic approach.
The Dynamic Characteristics of a High Pressure Turbine Stage in a Transient Wind Tunnel
Authors: Sheard A. G. , Dietz A. J. , Ainsworth R. W.
Published: March 2015

A new transient facility for the study of time averaged and unsteady aerodynamics and heat transfer in a high pressure turbine was recently commissioned. During the facility design a high priority was placed on ease of access to the turbine blading to facilitate the development of blade mounted instrumentation. The turbine disc was cantilevered on a shaft by a thin annular link, with the shaft passing back through the disc to a single row and matched pair of relatively closely spaced bearings. The bearings were originally designed for use in a marine gas turbine. Due to the facility’s novel mode of operation the bearings were working well beyond some of their original design limits, primarily due to the high turbine acceleration and the high speed/low load condition at the end of facility operation.

During the facility design a programme of work was undertaken to predict its dynamic performance. This was continued during commissioning to measure actual facility performance. In this paper the predicted dynamic performance of the disc/shaft assembly and its bearing system are presented. The programme of work undertaken during the facility commissioning phase to ascertain actual dynamic performance is described, and the results discussed. Finally, the technique developed to field balance the rotating assembly following changes to blade instrumentation is described.
Coupled 3-D Aeroelastic Stability Analysis of Bladed Disks
Authors: Gerolymos Georg A.
Published: March 2015

In the present work an algorithm for the coupled aeromechanical computation of 3-D compressor cascades vibrating in a traveling-wave mode is presented and applied to the determination of aeroelastic stability of a transonic fan rotor. The initial vibratory modes are computed using a finite-element structural analysis code. The unsteady flowfield response to blade vibration is estimated by numerical integration of the 3-D unsteady Euler equations. Coupling relations are formulated in the frequency domain, using a mode-modification technique, based on modal projection. The vibratory mode is updated at the end of the aerodynamic simulation of each period, and the updated mode is used for the simulation of the next period. A number of results illustrate the method’s potential.
The Evolution of Thermal Barrier Coatings in Gas Turbine Engine Applications
Authors: Meier Susan Manning , Gupta Dinesh K.
Published: March 2015

Thermal barrier coatings (TBCs) have been used for almost three decades to extend the life of combustors and augmentors and, more recently, stationary turbine components. Plasma sprayed yttria stabilized zirconia TBC currently is bill-of-material on many commercial jet engine parts. A more durable electron beam-physical vapor deposited (EB-PVD) ceramic coating recently has been developed for more demanding rotating as well as stationary turbine components. This ceramic EB-PVD is bill-of-material on turbine blades and vanes in current high thrust engine models and is being considered for newer developmental engines as well. To take maximum advantage of potential TBC benefits, the thermal effect of the TBC ceramic layer must become an integral element of the hot section component design system. To do this with acceptable reliability requires a suitable analytical life prediction model calibrated to engine experience. The latest efforts in thermal barrier coatings are directed toward correlating such models to measured engine performance.
Integration of Turbo-Expander- and Turbo-Ramjet-Engines in Hypersonic Vehicles
Authors: Zellner B. , Sterr W. , Herrmann O.
Published: March 2015

Turbo-Expander-Ramjet and Turbo-Ramjet are two engine concepts considered for hypersonic aircraft designs with a flight regime between Mach 0 and 7. To establish any performance or integration aspects for these two combined-cycle engine types, an extended study of a variety of influence parameters is necessary, because the interaction between aircraft and propulsion system is even stronger than on conventional aircraft. In fact, the propulsion system is very sensitive to intake and nozzle/afterbody design at these high speeds.
Investigations on a Radial Compressor Tandem-Rotor Stage With Adjustable Geometry
Authors: Josuhn-Kadner B. , Hoffmann B.
Published: March 2015

A radial compressor stage has been investigated mainly experimentally for aerodynamic stage optimization. The rotor (πt = 3.9) consists of a profiled axial inducer and a conventionally designed radial impeller. Inducer and impeller can be locked at different circumferential positions relative to each other thus, forming a tandem wheel with adjustable geometry. Conventional and Laser-2-Focus system measurements for the tandem-rotor and the stage were performed at different operating points to study the influence of the circumferential clearance geometry between inducer and impeller with respect to compressor characteristics and performance. Furthermore, 3-D Navier-Stokes calculations are being developed at design point condition to analyse the flow field. Small influence of the inducer adjustment on the rotor characteristics is observed. The maximum rotor efficiency of 93.5 % varies in a range of less than 1 % depending on the different inducer positions.