bluuebunny/crossref_metadata_2025 huggingface dataset:
Colocasiomyia (Diptera: Drosophilidae) revised phylogenetically, with a new species group having peculiar lifecycles on monsteroid (Araceae) host plants
Authors: FARTYAL RAJENDRA S. , GAO JIAN‐JUN , TODA MASANORI J. , HU YAO‐GUANG , TAKANO KOHEI TAKENAKA , SUWITO AWIT , KATOH TORU , TAKIGAHIRA TOMOHIRO , YIN JIAN‐TAO
Published: July 2013

The phylogeny of Colocasiomyia (Drosophilidae) is analysed using data for 70 morphological characters, many of which are re‐evaluated from or added to those used previously, for an expanded taxon sample of 24 Colocasiomyia ingroup species. A special focus is put on three species, of which two have remained unresolved for their relationships to other Colocasiomyia species, and the other is a newly discovered species. The analysis results in a single, most parsimonious cladogram, in which a clade comprising the three focal species is recognized along with other clades recovered for the known species groups of Colocasiomyia. Based on this, a new species group—the gigantea group—is established, including Colocasiomyia gigantea (Okada), C. rhaphidophorae Gao & Toda, n.sp. and C. scindapsae Fartyal & Toda, n.sp. These species of the gigantea group breed on inflorescences/infructescences of the subfamily Monsteroideae (Araceae) exceptionally among Colocasiomyia species, most of which use plants of the subfamily Aroideae as their hosts. Colocasiomyia gigantea uses Epipremnum pinnatum (L.) Engler, C. rhaphidophorae uses Rhaphidophora hookeri Schott and C. scindapsae uses Scindapsus coriaceus Engler as their hosts. The host plants of the gigantea group are epiphytes and differ in the structure of spadix and the fruiting process from those of the Aroideae. To understand how the species of the gigantea group adapt to properties of their host plants, their reproductive ecology—most intensively that of C. gigantea—is investigated. The lifecycle of C. gigantea is characterized by its relatively slow embryonic development (taking approximately 6 days), the very long duration of the full‐grown first instar within the egg capsule (approximately three months) until dehiscence of host infructescence, and its relatively fast larval and pupal development (taking approximately 11 or 12 days). Some morphological adaptations and the reproductive strategy in terms of ‘egg size vs. number’ trade‐off are discussed in relation to their reproductive habits and peculiar lifecycles.
Two new alleles, HLA‐B*35:226 and HLA‐B*40:233 identified by sequence‐based typing in Chinese individuals
Authors: Luo J. , Yang N. , Cao L.‐Q. , Xu Z.‐X.
Published: July 2013

HLA‐B*35:226 differs from HLA‐B*35:28, and HLAB*40:233 differs from HLA‐B*40:01:01, both by a nonsynonymous mutation.
Identification of a novel HLA‐DQB1 allele, DQB1*05:19, in an African American family by sequence‐based typing
Authors: Hommel‐Berrey G. A. , House K. D. , Backfish K. A. , Arnoff T. S. , Lobashevsky A.
Published: July 2013

The novel allele, DQB1*05:19, differs from the closest matching allele, DQB1*05:02:01, by one nucleotide substitution.
R Tricks for Kids
Authors: Braun W. John , White Bethany JG , Craig Gavin
Published: July 2013

Real‐world phenomena simulation models, which can be used to engage middle‐school students with probability, are described. Links to R instructional material and easy‐to‐use code are provided to facilitate implementation in the classroom.
Management of vault prolapse
Authors: Ramalingam K , Monga Ash
Published: July 2013

Key content

Vaginal wall prolapse is increasing in incidence with improvement in life expectancy.

Conservative and surgical treatments exist.

Treatment should be tailored to individual needs depending on prolapse symptoms, sexual function and co‐existing medical conditions.

Indications, expertise required and complications of different procedures should be explored with available evidence.

Learning objectives

Recognise the presentation of vaginal vault prolapse.

Learn about different options available for the treatment of vaginal vault prolapse.

Understand the limitations and complications of different procedures and counsel patients appropriately.

Ethical issues

Should procedures that improve quality of life be performed in elderly patients with comorbid conditions?

Should simpler surgical treatments such as colpocleisis or vaginal surgery be performed to be more cost‐effective compared with laparoscopic or robotic procedures?

How safe is it to use mesh in vault prolapse by the abdominal or vaginal route?
The relationship between infertility treatment and cancer including gynaecological cancers
Authors: Louis Louay S , Saso Srdjan , Ghaem‐Maghami Sadaf , Abdalla Hossam , Smith J Richard
Published: July 2013

Key content

Increasing availability and expanding usage of infertility treatment is a concern with regard to a possible increase in the risk of future malignancy development for women and their offspring.

Infertile women are at significantly increased risk of developing ovarian and uterine cancers, especially nulliparous women.

Earlier studies pointed to a possible increase in the risk of ovarian cancer following large doses and multiple cycles of clomiphene citrate.

Recent studies did not observe any increase in malignancy risk due to infertility medications. Other confounding factors, such as infertility itself, may well be the reason for the increased percentage of cancer cases noted in earlier studies.

Uterine cancer risk is possibly increased following multiple cycles and high doses of clomiphene citrate.

There is no strong evidence linking infertility treatment with non‐gynaecological or childhood cancers, with the possible exception of melanoma.

Learning objectives

To highlight the available evidence linking infertility treatment with gynaecological, non‐gynaecological and childhood cancers.

How to counsel women about any possible risk of future neoplasia after infertility treatment.

Ethical issues

Is it ethical to persevere with multiple fertility treatment cycles if it might be associated with increased risk of neoplasia in the future?
Review Essay: The Antiglobalisation Paradox – Freedom to Enter into Binding International Law is Real Freedom
Authors: Trachtman Joel P.
Published: July 2013

InThe Globalization Paradox, Dani Rodrik sets up what he calls a policy trilemma among hyperglobalisation, democracy and autonomy. This trilemma is best understood as a trade‐off between national autonomy and rules that promote globalisation. However, a contractual perspective on international law – recognising that states use international law to make exchanges of policy autonomy in ways that enhance each consenting state's welfare – suggests that there is no real trade‐off between national autonomy and international legal rules that promote globalisation. The antiglobalisation paradox is that these rules of international law may be seen as an expression of national autonomy. There is no trilemma, and even the trade‐off between national autonomy and globalisation must be understood instead as a trade‐off between two ways of promoting national welfare: one through autarchy and the other through international legal exchange. It then becomes apparent that a bias in favour of autarchy is mistaken, as it inappropriately limits the ways in which governments may promote national welfare. Furthermore, international law does not necessarily need, at the international level, the same types of mechanisms for democratic accountability that are required at the national level, because states consent to international law through their national democratic processes. Globalisation can take place through international legal rules that have appropriate democratic credentials and that leave in place appropriate national autonomy.
Trade in Services and Regional Trade Agreements: Do Negotiations on Services Have to be Specific?
Authors: Guillin Amélie
Published: July 2013

Trade in services has been on a substantial positive trend since the last decades, and the number of regional trade agreements (RTAs) in force has increased regularly overtime. However, negotiations on services remain hesitant even at the bilateral level. Classifying an RTA according to its degree of liberalisation in services allows accounting for ‘depth’ and heterogeneity issues amongst RTAs. I estimate a gravity equation using panel data covering the period 1999–2007, including bilateral and country‐and‐time fixed effects. The main results are: (i) amongst RTAs, only the trade agreements covering services have a significant effect on trade in services; and (ii) the deeper, in terms of sectors and of content, the agreement is, the more intratrade the signatory countries have.
Transfusion‐associated circulatory overload (TACO) and potential risk factors among the inpatient US elderly as recorded in Medicare administrative databases during 2011
Authors: Menis M. , Anderson S. A. , Forshee R. A. , McKean S. , Johnson C. , Holness L. , Warnock R. , Gondalia R. , Worrall C. M. , Kelman J. A. , Ball R. , Izurieta H. S.
Published: July 2013

Background and Objectives

Transfusion‐associated circulatory overload (TACO) is a serious transfusion complication resulting in respiratory distress. The study's objective was to assess TACO occurrence and potential risk factors among elderly Medicare beneficiaries (ages 65 and older) in the inpatient setting during 2011.

Materials and Methods

This retrospective claims‐based study utilized Medicare administrative databases in coordination with Centers for Medicare & Medicaid Services. Transfusions were identified by recorded procedure and revenue centre codes, while TACO was ascertained via ICD‐9‐CM diagnosis code. We evaluated TACO diagnosis code rates overall and by age, gender, race, number of units and blood components transfused. Multivariate logistic regression analyses were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs).

Results

Among 2 147 038 inpatient transfusion stays for elderly in 2011, 1340 had TACO diagnosis code, overall rate of 62·4 per 100 000 stays. TACO rates increased significantly with age and units transfused (P < 0·0001). After adjustment for confounding, significantly higher odds of TACO were found for women vs. men (OR = 1·40, 95% CI 1·26–1·60), White people vs. non‐White people (OR = 1·38, 95% CI 1·20–1·62) and persons with congestive heart failure (OR = 1·61, 95% CI 1·44–1·88), chronic pulmonary disease (OR = 1·19, 95% CI 1·08–1·32) and different anaemias.

Conclusion

Our study identified largest number of potential TACO cases to date and showed a substantial increase in TACO occurrence with age and number of units transfused. The study suggested increased TACO risk in elderly with congestive heart failure, chronic pulmonary disease and anaemias. Overall, study shows importance of large administrative databases as an additional epidemiological tool.
Survey of Heliostat Concepts for Cost Reduction
Authors: Pfahl Andreas
Published: July 2013

A survey of hitherto concepts for cost reduction of heliostats is given. The survey might serve as a base for the development of low cost heliostats that are needed to meet the current challenging cost objectives. The concepts are related to the main heliostat subfunctions and to basic approaches for cost reduction found so far. Based on the main advantages and drawbacks of every concept, the most promising ones are indicated.
Electro-Thermal Measurement of Heat Transfer Coefficients
Authors: Uffrecht Wieland , Günther André , Caspary Volker
Published: July 2013

Heat transfer coefficients are very important for the design of the various flow paths found in turbomachinery. Therefore, the measurement of heat transfer coefficients plays an important role in the field of turbomachinery research. An accurate measurement of heat transfer is not a simple task considering gaseous flow in combination with good thermal conductivity of the boundaries along the flow path. The majority of the measurement methods applied has at least one of the following problems. The measurement setup as for instance a heat flux sensor is a thermal barrier in the object of interest or the sensor introduces for measurement reasons a lot of heat into the object of interest. In both cases the main error results from the modification of the system, which is critical for the investigation of any kind of flow influenced by buoyancy. Furthermore, insufficient fluid reference temperature and/or heat flux with changing sign corrupts any attempt to calculate reasonably heat transfer coefficients.

The measurement of heat transfer coefficients becomes even more complicated if the flow path of interest rotates at some thousand rpm as for instance in gas turbines or any other fast rotating machine with fluid flow. This contribution presents an experimental investigation of a setup for the direct measurement of heat transfer coefficients in gaseous flow with metallic boundaries. The calibration of a test sample probe is presented for the standard case forced convection on a flat plate. The sensor setup provides low influence of the measurement on the object investigated. It overcomes the problem of a reference temperature and delivers always positive heat transfer coefficients. Furthermore, the measurement setup fulfils the requirements of telemetric application in the rotating system of a machine. The test of the sensor for its strength against centrifugal acceleration is part of the continuation of the work.
Numerical Investigation of the Parameter Governing the Ignitability of a Spray Flame
Authors: Boyde J. M. , Le Clercq P. , Di Domenico M. , Rachner M. , Gebel G. C. , Mosbach T. , Aigner M.
Published: July 2013

This paper contains a numerical examination concerning the ignition behavior of a spray nozzle mounted in a rectangular channel under atmospheric conditions which is run with Jet A-1. On the basis of a comprehensive data set of experimental results, the numerical approach is verified primarily by means of a comparison of the flame growth and position after ignition. In the following several distinct igniter positions and boundary condition settings are simulated. The conditions which prevail at the location of the ignition are investigated with respect to how they influence the ignition process. Due to changes in the fuel placement and flow field characteristics which follow from alternating the boundary conditions such as air and fuel mass flow, ignition is either promoted or impeded. The underlying causes which can lead to a success or failure of the ignition are analyzed. The ignition in the experiment is achieved through a laser-induced breakdown, which is modelled through a Turbulent Flame Speed Closure combustion model with an additional spark ignition extension. A comparison with the ignition statistics from the experiment shows that numerical tools can be used to determine preferential boundary conditions and igniter locations to accomplish a successful ignition in multiphase flow configurations.
Spray Flames Simulation Using a Two Phase Combustion Model With Single Droplet Combustion Mode
Authors: Wang F. , Huang Y.
Published: July 2013

There are three combustion regimes of individual droplet combustion behavior: the fully enveloped flame, the partially enveloped flame, and the wake flame. From PLIF measurement results, single droplet combustion phenomenon happens in spray flame, as well as lean type gas turbine combustion chamber sometimes. The drag coefficient, evaporation rate, and combustion rate are different according to the burning modes. At present, in Reynolds Averaged Navier Stokes (RANS) method and Large Eddy Simulation (LES) method, the droplets are treated as point source because the grid scale is bigger than the droplet diameter. A two phase combustion model with the consideration of the individual droplet burning mode is proposed before. In this paper, this model is tested by spray flames here again. Furthermore, this model was used in a concept lean premixed pre-vaporized (LPP) combustion case too. In spray flame, the predicted results are close to the experimental data.
Performance and Emission Experimental Evaluation and Comparison of a Regenerative Gas Turbine Using Ethanol as Fuel
Authors: dos Santos Eraldo Cruz , do Nascimento Marco Antônio Rosa
Published: July 2013

Brazil is the most advanced country in terms of technology, production and use of ethanol as fuel. Alcohol can be obtained from various forms of biomass, being sugarcane a current economic reality. The environmental benefits associated with the use of alcohol are enormous, as approximately 2.3 tons of CO2 are no longer emitted to the atmosphere for each ton of ethanol, without taking into account emissions of other gases such as SO2. Sugarcane is the second largest source of renewable energy in Brazil, with 12.6% of participation in the current energy matrix, considering the ethanol fuel and cogeneration of electricity from sugarcane bagasse.

The aim of this work is an experimental analysis of thermal performance/emissions of a 30 kW regenerative cycle gas turbine engine using ethanol as fuel. The tests were carried out in the laboratories of the Federal University of Itajubá – UNIFEI, Brazil, on steady state condition under different load levels, considering the properties of ethanol in compliance with Brazilian legislations.

The results shown that there were no significant changes in the thermal performance of the gas turbine engine and the emissions ware a slight increase in CO and a reduction in concentrations of NOx.
Nonequilibrium Effect on Nitrogen Oxides Production in a Diffusion Flame
Authors: Tsatiashvili V. V. , Avgustinovich V. G.
Published: July 2013

Reduction of NOx emission of aircraft gas turbines is moving in the direction of development of direct combustor fuel injection systems providing conditions for rapid mixing and combustion of a uniform lean fuel/air mixture. However, formation of sufficient uniform fuel/air mixture in real combustors fails to be completed. It may result in burning out a considerable portion of fuel in stoichiometric conditions that in turn imposes limits on the emission level minimizing. The research accomplished by a number of authors justifies the necessity of decreasing the extent of stoichiometric zones by means of increasing fuel-air mixing rate on the stoichiometric surface of their contact, to reduce emission. This publication contains the analysis results upon the effect of mixing rate, in terms of a methane-air laminar diffusion combustion. It is proved that changes of mixing rate influence the two main factors governing the emission level: the extent of NO production zone and the efficient rate of its production. If the mixing rate increases explicitly due to the decrease of NOx production scale, the efficient velocity curve will contain a maximum value. Furthermore, the scale effect is all-over stronger than the kinetic one. It is concluded that in case of mixing rate increase, the reduction of NOx emission goes nonlinearly and steadily. The ranges of maximum effect are specified. Herewith, we introduce the relation, which demonstrates that in the diffusion combustion a sufficient reduction of NOx emission can be achieved.
Absolute and Convective Instability in Gas Turbine Fuel Injectors
Authors: Juniper Matthew P.
Published: July 2013

Hydrodynamic instabilities in gas turbine fuel injectors help to mix the fuel and air but can sometimes lock into acoustic oscillations and contribute to thermoacoustic instability. This paper describes a linear stability analysis that predicts the frequencies and strengths of hydrodynamic instabilities and identifies the regions of the flow that cause them. It distinguishes between convective instabilities, which grow in time but are convected away by the flow, and absolute instabilities, which grow in time without being convected away. Convectively unstable flows amplify external perturbations, while absolutely unstable flows also oscillate at intrinsic frequencies. As an input, this analysis requires velocity and density fields, either from a steady but unstable solution to the Navier–Stokes equations, or from time-averaged numerical simulations. In the former case, the analysis is a predictive tool. In the latter case, it is a diagnostic tool. This technique is applied to three flows: a swirling wake at Re = 400, a single stream swirling fuel injector at Re ∼ 106, and a lean premixed gas turbine injector with five swirling streams at Re ∼ 106.

Its application to the swirling wake demonstrates that this technique can correctly predict the frequency, growth rate and dominant wavemaker region of the flow. It also shows that the zone of absolute instability found from the spatio-temporal analysis is a good approximation to the wavemaker region, which is found by overlapping the direct and adjoint global modes. This approximation is used in the other two flows because it is difficult to calculate their adjoint global modes.

Its application to the single stream fuel injector demonstrates that it can identify the regions of the flow that are responsible for generating the hydrodynamic oscillations seen in LES and experimental data. The frequencies predicted by this technique are within a few percent of the measured frequencies. The technique also explains why these oscillations become weaker when a central jet is injected along the centreline. This is because the absolutely unstable region that causes the oscillations becomes convectively unstable.

Its application to the lean premixed gas turbine injector reveals that several regions of the flow are hydrodynamically unstable, each with a different frequency and a different strength. For example, it reveals that the central region of confined swirling flow is strongly absolutely unstable and sets up a precessing vortex core, which is likely to aid mixing throughout the injector. It also reveals that the region between the second and third streams is slightly absolutely unstable at a frequency that is likely to coincide with acoustic modes within the combustion chamber. This technique, coupled with knowledge of the acoustic modes in a combustion chamber, is likely to be a useful design tool for the passive control of mixing and combustion instability.
Development of a Lean Staged Combustor for Small Aero-Engines
Authors: Matsuyama Ryusuke , Kobayashi Masayoshi , Ogata Hideki , Horikawa Atsushi , Kinoshita Yasuhiro
Published: July 2013

As the amount of air traffic is rapidly increasing, the local air quality around airports and the global climate change are two major concerns. Under the circumstances, the regulation for NOx emission becomes more stringent year after year. Lean burn technology is one of the key technologies for the next generation civil aircraft engines. Kawasaki Heavy Industries (KHI) has been developing a Lean Pre-mixed Pre-vaporized (LPP) combustor for around 10,000 lb thrust class engine under the project of Environmentally Compatible Aircraft Engines for Small Aircraft (ECO)[1] led by New Energy and Industrial Technology Development Organization (NEDO) and Ministry of Economy, Trade and Industry (METI).

In this paper the results of the LPP combustor development about reducing NOx emissions is presented. The LPP burner main premixed duct is designed to have better mixing fuel and air. KHI have achieved 30%CAEP4 NOx without deterioration of the other combustor performance. In general altitude relight would be one of the weak points for LPP combustion system. Successful lights were confirmed up to 30kft altitude condition in the multi sector rig, which is as good as that of the conventional combustors. Several LPP burners have been developed through CFD results. The burners have been spray-tested and combustion-tested in a single burner test rig in order to improve the burner potential. The burners selected in the single sector tests have been evaluated in a multi sector combustor rig with several combustor configurations. This paper describes the multi sector test results together with the brief introduction on burner development activities through burner tests.
Towards the Automated Optimisation of Liquid Fuel Injector Design for Gas Turbine Engines
Authors: Comer Adam L. , Cant R. Stewart
Published: July 2013

Given the trend towards leaner combustor primary zones and concurrent increases in injector air mass flow rates for emissions reduction, an automated fuel injector optimisation procedure is proposed for a generic aero-engine combustor. The modelling assumptions and the design of the toolset to be applied for the optimisation study, as well as preliminary results from the computational tools, are presented. The proposed configuration will enable the consideration of the following design parameters: the number of swirlers, the swirl number for each swirler, the air mass flow splits between the swirlers, and the fuel mass flow split for multiple prefilming surfaces. Results from the unsteady RANS spray combustion solver available through the OpenFOAM software package are combined with semi-empirical correlations in order to estimate and capture trends in emissions. Pattern factor and susceptibility to thermoacoustic oscillations are assessed directly through the simulation output. Due to computational costs, only the cruise condition is considered for optimisation, and off-design considerations have been limited to their impact on preliminary combustor sizing and design. A multi-fidelity optimisation strategy incorporating a multi-objective Tabu Search algorithm is also presented in light of the nature of the problem and the complexity of the design spaces constructed from CFD results.
Large Eddy Simulation of Flame Response to Transverse Acoustic Excitation in a Model Reheat Combustor
Authors: Zellhuber M. , Meraner C. , Kulkarni R. , Polifke W. , Schuermans B.
Published: July 2013

The response of a perfectly premixed, turbulent jet flame at elevated inflow temperature to high frequency flow perturbations is investigated. A generic reheat burner geometry is considered, where the spatial distribution of heat release is controlled by auto-ignition in the jet core on the one hand, and kinematic balance between flow and flame propagation in the shear layers between the jet and the external recirculation zones on the other. To model auto-ignition and heat release in compressible turbulent flow, a progress variable / stochastic fields formulation adapted for the LES context is used. Flow field perturbations corresponding to transverse acoustic modes are imposed by harmonic excitation of velocity at the combustor boundaries. Simulations with single-frequency excitation are carried out in order to study the flame response to transverse fluctuations of velocity. Heat release fluctuations are observed predominantly in the shear layers, where flame propagation is important. The flow-flame coupling in these regions is analysed in detail with a filter-based post-processing approach, invoking a local Rayleigh index and providing insight into the interactions of flame wrinkling by vorticity and convection due to mean and fluctuating velocity.
Reduction of NOx Emissions in Alstom GT11NM Engines: Development, Validation and Engine Operation Experience of the EV-Alpha Burner
Authors: Magni Fulvio , Hudgins Duane , Geng Weiqun , Grimm Frank
Published: July 2013

The first Alstom GT11N engine was introduced to the market at the end of the eighties. In order to keep our base fleet engines (aged fleet) attractive for dispatch and therefore for operation, one of the key issues of the service business is the development of upgrade packages. For the GT11N fleet an emission reduction package was worked out in recent years with the target of single digit NOx at base load (<10 ppm NOx @15%O2). The purpose of this paper is to present the performed development work, starting from the R&D work with the CFD optimization of the mixing quality, going to the atmospheric combustion tests and finally to the engine validation tests on site.

The first section of the paper focuses on the performed R&D work, mainly on the improvement of the gas/air mixing quality of the EV burner. For the down selection of the most promising configurations the calculated unmixedness at different places of the burner and the hottest flame zones were analyzed and evaluated. The second part of the paper focuses on the results of the atmospheric burner combustion tests. The last part of the paper is focusing on the verification phase and on the achieved results during the engine validation tests on site. The EV-alpha burners were implemented during an A-inspection. Before the implementation a reference measurement with the standard EV burners was carried out. This section gives an overview of the performed engine tests and achieved emissions at base load and part load, about flame stability behaviour and transient operation results.

With the implementation of the EV-alpha burner the target “single digit NOx” could be achieved and the combustion stability kept at comparable levels.
Influence of Ambient Conditions on Laminar Burning Velocity, Ignition and Flame Extinction for Ethanol-Air Mixtures
Authors: de la Rosa Daniel , Crayford Andrew P. , Bowen Philip J. , Valera-Medina Agustin
Published: July 2013

Experimental studies of laminar ethanol - air gaseous flames have been undertaken in a large (34 l) cylindrical constant volume combustion bomb to investigate combustion fundamentals at varying ambient conditions. This vessel has been designed to minimise the influence of boundary walls, hence extending the quasi steady pressure region over which meaningful data may be obtained. Gaseous homogeneous mixtures are achieved by injecting liquid ethanol into the bomb which pre-vaporises prior to ignition. Initial pressure and equivalence ratio are predetermined using partial pressure methodology. Flame propagation is recorded utilising high-speed Schlieren photography, and low ignition energies were achieved via a variable discharge system enabling the sensitive early stages of flame propagation and extinction limits to be studied. Data is presented in terms of flame speed against stretch rate from which Markstein lengths and laminar burning velocities are derived for a variety of different initial conditions. The effect of ignition energy, initial pressure (from sub-atmospheric to elevated pressure) along with the effect of increasing initial temperature is studied. Results are discussed in terms of those of previous workers, and compared with predictions from detailed chemical kinetic schemes. Nonlinear trends witnessed during early stage flame propagation are further investigated as a suitable method for deriving extinction stretch rate.
Emission Reduction of Fuel Staged Aircraft Engine Combustor Using an Additional Premixed Fuel Nozzle
Authors: Yamamoto Takeshi , Shimodaira Kazuo , Yoshida Seiji , Kurosawa Yoji
Published: July 2013

The Japan Aerospace Exploration Agency (JAXA) is conducting research and development on aircraft engine technologies to reduce environmental impact for the TechCLEAN project. As a part of the project, combustion technologies have been developed with an aggressive target that is an 80% reduction over the NOx threshold of the ICAO CAEP/4 standard. A staged fuel nozzle with a pilot mixer and a main mixer was developed and tested using a single-sector combustor under the target engine’s LTO cycle conditions with a rated output of 40 kN and an overall pressure ratio of 25.8. The test results showed a 77% reduction over the CAEP/4 NOx standard. A reduction in smoke was found under a higher thrust condition than the 30% MTO condition, and a reduction in CO emission was found under a lower thrust condition than the 85% MTO condition. In the present study, an additional fuel burner was designed and tested with the staged fuel nozzle in a single-sector combustor to control emissions. The test results show that the combustor enables an 82% reduction in NOx emissions relative to the ICAO CAEP/4 standard and a drastic reduction in smoke and CO emissions.
Theoretical and Computational Analysis of an Auxiliary Power Unit (APU) Installation Cooling System
Authors: Shah Parthiv N. , Sur Tricia Waniewski , Miskovish R. Scott , Robinson Albert
Published: July 2013

This paper presents a theoretical one-dimensional model and computational fluid dynamics (CFD) simulations of a tailcone-installed APU cooling system. The work is motivated by the need to deliver sufficient cooling airflow to critical components within an aircraft tailcone compartment. The cooling system considered herein utilizes (1) an eductor system at the APU exhaust and (2) a ram air scoop near an upstream inlet to the compartment to induce the necessary cooling flow during ground and in-flight APU operation. A one-dimensional flow network model provides a framework for the quantification and matching of eductor pumping and system pressure drop characteristics. Detailed CFD models that simulate internal tailcone compartment flows driven by ambient conditions external to the aircraft in ground or flight operation support the one-dimensional model and are used to characterize component performance and assess different scoop and eductor designs. The one-dimensional flow network model is calibrated to the CFD results to predict system cooling performance under known APU loads at points on the ground and in the flight envelope. The agreement between the models is encouraging and suggests the modeling framework and CFD techniques discussed will be applicable to future designs and improvements of eductor-driven aircraft compartment cooling systems.
Including Heat Loss and Quench Effects in Algebraic Models for Large Eddy Simulation of Premixed Combustion
Authors: Keppeler Roman , Pfitzner Michael , Tay Wo Chong Luis , Komarek Thomas , Polifke Wolfgang
Published: July 2013

In technically relevant combustion devices, combustion can take place in the vicinity of walls which can significantly affect the reaction and the heat transfer. However, only few studies focus on modelling of flame-wall interaction (FWI) for algebraic combustion models and virtually none consider FWI for algebraic Large Eddy Simulation combustion models. In the present work heat loss models, as previously published in the literature, are employed to extend a LES algebraic combustion model. The performance of the FWI models is evaluated by simulations of a nonadiabatic swirl flame. The simulation results are compared with experimental data of velocity field and heat release. The extent of the quenching zone and heat loss effects are determined in the simulations and compared with data from direct numerical simulations. Comparison of simulation and experimental data shows a significant improvement when heat loss effects are incorporated. Also the characteristic Peclet numbers are correctly predicted by FWI models.
Absorption of Normal-Incidence Acoustic Waves by Double Perforated Liners of Industrial Gas Turbine Combustors
Authors: Jayatunga Charith , Qin Qin , Sanderson Victoria , Rubini Phil , You Danning , Krebs Werner
Published: July 2013

Perforated liners consist of sheet metal perforated with multiple holes with diameters of magnitude in the order of millimeters and regular spacing, backed by an air cavity in front of a rigid wall. This type of liner is very effective at absorbing sound and is used in many applications. At the resonance frequency, the liner shifts the phase of the incident wave by 180° thus providing damping through wave cancellation.

The perforations in the liner convert acoustic energy into flow energy through vortex shedding at the rims of the liner apertures.

Applied to gas turbine combustors they can attenuate thermoacoustic instabilities and as such significantly improve the reliability of the gas turbine with an additional benefit to the emissions. The Siemens SGT-100 to 400 engines exploit this technology in their DLE combustion system in a configuration of two concentric liners separated by an air cavity with the rear liner acting as the rigid wall in the conventional setting.

In this paper the evaluation of double perforated liners in the absorption of normal-incident plane acoustic waves in an impedance tube and in a gas turbine combustor environment is investigated.

A one-dimensional impedance model that embodies the electro-acoustic analogy was used to predict the absorption characteristics of the double perforated liner. The model was validated by comparing the predictions with experimental data obtained from the impedance tube, with excellent agreement. With the confidence in the equations of the model in predicting the acoustic behavior, the model was then applied to predict the damping performance under realistic gas turbine combustor operating conditions. The prediction also shows two distinct peaks in the absorption characteristics of a double-liner.

Geometric parameters such as hole diameters & thicknesses of the two liners, gap between the liners and the overall pressure drop across the liners have been considered for the predictions. A parametric study of these parameters carried out using the ISIGHT software with design investigation tools identified the order of importance of the parameters considered for sound absorption.

The work reported in this paper has successfully validated an impedance model in the prediction of double perforated liners in the absorption of normal-incident plane acoustic waves. Based on the parametric study carried out design guidelines are given for designing a double perforated liner for maximum absorption of normal incident acoustic waves.
Using Boundary Conditions to Account for Mean Flow Effects in a Zero Mach Number Acoustic Solver
Authors: Motheau Emmanuel , Nicoud Franck , Poinsot Thierry
Published: July 2013

The present study is devoted to the modeling of mean flow effects while computing thermoacoustic modes under the zero Mach number assumption. It is first recalled that the acoustic impedance modelling a compressor or a turbine must be prescribed under an energetical form instead of the classical acoustic variables. Then we demonstrate the feasibility to take into account the coupling between acoustic and entropy waves in a zero Mach number framework to capture a family of low frequency entropic modes. The proposed approach relies on a new Delayed Entropy Coupled Boundary Condition (DECBC) and proves able to capture a family of Low frequency entropic mode even though no mean flow term is included into the fluctuating pressure equation.
Large-Eddy Simulation in an Industrial Gasturbine Combustor for NOx Prediction
Authors: Hirano Kohshi , Nonaka Yoshiharu , Kinoshita Yasuhiro , Oshima Nobuyuki , Matsuya Kyohei
Published: July 2013

NOx emission reduction is important for developing gas-turbine engines. Predicting the thermal profile and pollutant-emission factor by numerical simulation is effective for reducing the development costs. Here a large eddy simulation coupled with a 2-scalar flamelet approach is applied to the numerical analysis of an industrial gas-turbine combustor. The combustor of an L20A-DLE gas-turbine engine is calculated. Combustor performance under different loads is investigated. NOx production decreases with reducing load, and this tendency agrees well with the experimental results. It is said that NOx production due to a large amount of supplemental burner fuel. NOx production in the simulation is lower than in the experiment. The simulated temperature in the combustor outlet is also lower than the adiabatic temperature. Moreover, the fuel is not burned completely within the combustor region. The difference in the combustion status in a supplemental burner is investigated. For the diffusion flame, a high-temperature region is observed locally owing to the presence of a fuel-rich region. For NOx production, NOx emission reduction is expected using a burner that introduces a premixed flame. From the simulation results, we can estimate NOx production in a gas-turbine combustor. The tendencies in the differences of the loads agreed well with the experimental data, and the superiority of a premixed flame was indicated.
Nonlinear Flame Describing Function Analysis of Galloping Limit Cycles Featuring Chaotic States in Premixed Combustors
Authors: Boudy Frédéric , Durox Daniel , Schuller Thierry , Candel Sébastien
Published: July 2013

Nonlinear prediction of combustion instabilities in premixed systems is undertaken on a generic configuration featuring an adjustable feeding manifold length, a multipoint injector composed of a perforated plate and a flame confinement tube. By changing the feeding manifold or flame tube lengths, the system exhibits different types of combustion regimes for the same flow operating conditions. Velocity, pressure and heat release rate measurements are used to examine oscillations during unstable operation. For many operating conditions, a limit cycle is reached at an essentially fixed oscillation frequency and quasi-constant amplitude. In another set of cases, the system features other types of oscillations characterized by multiple frequencies, amplitude modulation and irregular bursts which can be designated by “galloping” limit cycles or GLC. These situations are explored in this article. Imaging during GLCs indicates that the flame is globally oscillating but that the cycle is irregular. Prediction of these special oscillation states is tackled within the Flame Describing Function (FDF) framework. It is shown that it is possible to predict with a reasonable degree of agreement the ranges where a quasi-constant amplitude limit cycle will be established and ranges where the oscillation will be less regular and take the form of a galloping limit cycle. It is found that the FDF analysis also provides indications on the bounding levels of the oscillation envelope in the latter case.
Prediction of Blow-Offs of Bluff Body Stabilized Flames Utilizing Close-Coupled Injection of Liquid Fuels
Authors: Klusmeyer Alex , Cross Caleb , Lubarsky Eugene , Bibik Oleksandr , Shcherbik Dmitriy , Zinn Ben T.
Published: July 2013

This paper describes the development of an empirical approach that attempts to predict blow-out of bluff body stabilized flames using global flow parameters in systems where liquid fuel injectors are located a short distance upstream of the wake. This approach was created on the hypothesis that flame stability in such a combustion system (referred to as a close-coupled injection) is determined by the strength of the heat source developed in the bluff body recirculation zone and by the availability of sufficient contact time with fresh mixture for its ignition, similar in nature to premixed combustion systems. Based on this concept, global equivalence ratio on the classical DeZubay stability map was replaced by local equivalence ratio in the recirculation zone of the bluff body. This local equivalence ratio was determined experimentally using a chemiluminescence measurement system. Tests were conducted using a single bluff body with a close coupled injection system in a 76×152mm (3×6 inches) combustion tunnel. A wide range of fuel-air ratios and velocities were achieved by variation of the global equivalence ratio, incoming flow velocity, and injector size. The obtained experimental data set was used to develop a transfer function that allowed calculation of the local equivalence ratio in the recirculation zone based on the global flow parameters. Equivalence ratio in the recirculation zone was found to be exponentially dependent upon the square root of the fuel to air momentum flux ratio such that increasing the momentum flux ratio led to a reduction in the recirculation zone equivalence ratio. Additional adjustment of this general trend by the diameter of injector and air flow velocity was necessary to improve the quality of the prediction. The developed approach demonstrated a good prediction of the globally rich blow-out of the flame. In fact, the recirculation zone lean blow-out limit (corresponding with globally rich blow-out) predicted for close coupled injection using the developed transfer function closely coincided with the lean blow-out line of the classical DeZubay envelope and with results obtained with premixed injection using the same bluff body. On the contrary, globally lean (locally rich) blow-out was predicted ∼20% below the DeZubay rich blow-out line, possibly because of the limited range of the fuel flow rates on the experimental rig used.
Design, Evaluation and Performance Analysis of Staged Low Emission Combustors
Authors: Hegde Gajanana B. , Khandelwal Bhupendra , Sethi Vishal , Singh Riti
Published: July 2013

The most uncertain and challenging part in the design of a gas turbine has long been the combustion chamber. There has been large number of experimentations in industries and universities alike to better understand the dynamic and complex processes that occur inside a combustion chamber. This study concentrates on gas turbine combustors as a whole, and formulates a theoretical design procedure for staged combustors in particular. Not much of literatures available currently in public domain provide intensive study on designing staged combustors. The work covers an extensive study of design methods applied in conventional combustor designs, which includes the reverse flow combustor and the axial flow annular combustors. The knowledge acquired from this study is then applied to develop a theoretical design methodology for double staged (radial and axial) low emission annular combustors. Additionally a model combustor is designed for each type; radial and axial staging using the developed methodology. A prediction of the performance for the model combustors is executed. The main conclusion is that the dimensions of model combustors obtained from the developed design methodology are within the feasibility limits. The comparison between the radially staged and the axially staged combustor has yielded the predicted results such as lower NOx prediction for the latter and shorter combustor length for the former. The NOx emission result of the new combustor models are found to be in the range of 50–60ppm. However the predicted NOx results are only very crude and need further detailed study.
CFD Predictions of Isothermal Fuel-Air Mixing in a Radial Swirl Low NOx Combustor Using Various RANS Turbulence Models
Authors: King Phil T. , Andrews Gordon E. , Pourkashanian Mohamed M. , McIntosh Andy C.
Published: July 2013

A radial swirl DLE combustion system was investigated for its gaseous fuel-air mixing performance using various different RANS turbulence models. Two different configurations were investigated; vane passage fuel injection and fuel injection from the wall of an outlet throat directly into the shear layer. The results showed that for vane passage fuel injection, only the standard k-ε and standard Spalart-Allmaras models were able to provide a reasonable prediction for the combustor fuel-air distribution, out of all the RANS models and their variants available in Fluent v6.3, although both models predicted that the fuel and air were better mixed than in the measurements. For outlet throat wall fuel injection no models were able to provide a reasonable prediction. This same issue is also reported by several other researchers and represents a serious problem area in combustion modeling for low NOx applications. Improved fuel jet penetration was achieved by using an extremely low value of 0.1 for the turbulent Schmidt number, therefore future work will concentrate on using a localized value of Sc in the vicinity of the fuel injection hole.