bluuebunny/crossref_metadata_2025 huggingface dataset:
Histopathological diagnosis of graft‐versus‐host disease of the skin – an interobserver comparison
Authors: Ziemer M. , Haeusermann P. , Janin A. , Massi D. , Ziepert M. , Wolff D. , Greinix H. , Hillen U.
Published: August 2013

Background

Histopathology is an important tool in diagnosing cutaneous graft‐versus‐host disease (GvHD). Minimum diagnostic criteria for active chronic GvHD have recently been defined. However, they are not specific and their interpretation is dependent on observer judgement.

Objective

Aims of the study: i) to explore interobserver variability in the interpretation of histopathological changes in GvHD, and ii) to analyse the impact of detailed clinical data on histopathological diagnosis of GvHD.

Methods

Histopathological slides from 15 skin biopsies of GvHD and from dermatoses with histopathologically similar appearance were sent in two phases to four dermatopathologists experienced in cutaneous GvHD in France, Germany, Italy and Switzerland (first round of ‘blind’ review followed by a second round with complete clinical information provided).

Results

Interface dermatitis, especially vacuolar alteration, was the most inconsistently evaluated, particularly in cases with minor alterations. Interestingly, for vacuolar alteration and apoptotic keratinocytes, interobserver variability was lower in the adnexal epithelia than in the interfollicular epidermis.

Complete clinical information resulted in increased diagnostic confidence and greater concordance on the final diagnosis, rising from 53% (first round, k = 0.345, fair agreement) to 80% (second round, k = 0.529, moderate agreement). The percentage of correct diagnoses increased from 33.3% to 80%.

Conclusion

For the diagnosis of GvHD, histopathological analysis is of importance, but, for correct diagnosis, the correlation of pathological findings with clinical results is crucial. In cases of minor alteration, histopathologists should focus on the interpretation of vacuolar changes and apoptotic keratinocytes, possibly on the adnexal epithelia.
Propionibacterium acnes: an update on its role in the pathogenesis of acne
Authors: Beylot C. , Auffret N. , Poli F. , Claudel J.‐P. , Leccia M.‐T. , Del Giudice P. , Dreno B.
Published: August 2013

In recent years, significant progress has been made in the understanding of the pathophysiological mechanisms of acne and the role of Propionibacterium acnes. With this review, the authors aim to provide an update on the current understanding of the role of P. acnes in the development of acne lesions and analysing the potential implications for future treatments. A total of 188 articles published between January 1980 and March 2013 were searched using key words such as acne, P. acnes, microbiology, Corynebacterium acnes, acne vulgaris, pathogenesis, antibiotic, vaccination and a combination of those key words. From those articles, 77 were analysed in depth. Recent data confirm that P. acnes has a strong proinflammatory activity and targets molecules involved in the innate cutaneous immunity, keratinocytes and sebaceous glands of the pilosebaceous follicle and leads to the development of comedones. Furthermore, the profile of its different strains may differ between healthy subjects and acne patients. The better understanding of the role of P. acnes may allow for new perspectives in the treatment of acne. Novel therapies should target molecules implicated in the activation of innate immunity, including toll‐like receptors, protease‐activated receptors and topical antimicrobial peptides; the latter may be an alternative to topical antibiotics and thus a solution for limiting bacterial resistance induced by topical macrolides. Vaccines may also be promising. However, the most appropriate candidate remains to be selected.
Investigation of process temperature and screw speed on properties of a pharmaceutical solid dispersion using corotating and counter-rotating twin-screw extruders
Authors: Keen Justin M , Martin Charlie , Machado Augie , Sandhu Harpreet , McGinity James W , DiNunzio James C
Published: August 2013

Objective

The use of corotating twin screw hot-melt extruders to prepare amorphous drug/polymer systems has become commonplace. As small molecule drug candidates exiting discovery pipelines trend towards higher MW and become more structurally complicated, the acceptable operating space shifts below the drug melting point. The objective of this research is to investigate the extrusion process space, which should be selected to ensure that the drug is solubilized in the polymer with minimal thermal exposure, is critical in ensuring the performance, stability and purity of the solid dispersion.

Methods

The properties of a model solid dispersion were investigated using both corotating and counter-rotating hot-melt twin-screw extruders operated at various temperatures and screw speeds. The solid state and dissolution performance of the resulting solid dispersions was investigated and evaluated in context of thermodynamic predictions from Flory–Huggins Theory. In addition, the residence time distributions were measured using a tracer, modelled and characterized.

Key findings

The amorphous content in the resulting solid dispersions was dependent on the combination of screw speed, temperature and operating mode.

Conclusions

The counter-rotating extruder was observed to form amorphous solid dispersions at a slightly lower temperature and with a narrower residence time distribution, which also exhibited a more desirable shape.
The Scholarly Monograph Unbound
Authors: Fyfe Paul
Published: August 2013

Particularly in humanities disciplines, the scholarly monograph has held a privileged place within an ecology of prestige. But systemic changes in the economics of academic publishing and the technical affordances of digital, networked scholarship raise many questions about the “book” and its futures. This essay enters debates about the future of the book to illustrate the institutional pressures, technological shifts, and intellectual opportunities that are reshaping the scholarly monograph.
Trauma Studies and the Literature of the U.S. South
Authors: Hinrichsen Lisa
Published: August 2013

The history of the U.S. South is one undeniably littered with traumatic acts, laws, and legitimized behaviors: racially biased laws that relegated Blacks to the status of disposable bodies denied by White culture; the regulated, segregated spaces of Jim Crow; and brutal, repetitive acts of violence that include lynching, incest, rape, and murder. This essay assesses the role that trauma studies, as an interdisciplinary area of investigation that came to prominence in the early‐to‐mid‐1990s, has played in assessing the ways that injury is troped, represented, and repeated in southern literature and its criticism. This essay first outlines the history of trauma as a theory, drawing attention to the fissures within the concept as it has developed over time, while also surveying the surge of works published under this rubric. The essay then assesses how trauma studies, with its attention to the nuances of testimony, the interlocked nature of personal and political traumas, and the importance of collective and cultural perspectives, has come to influence criticism on the literature of the U.S. South.
(Old) English, Anglo‐Saxon Legal Texts in the Later 11th to Mid‐12th Centuries
Authors: Gobbitt Thomas
Published: August 2013

Manuscripts containing English language copies of Anglo‐Saxon laws and related texts continued to be produced and used well into the mid‐12th century. Interpretations of the underling manuscript contexts prevalent in the scholarship have tended to prioritise the Conquest as the defining feature underlying their production and use. Such interpretations assume that the collation of a wide range of Anglo‐Saxon legal texts into a single manuscript context was a direct result of Norman rulers struggling to understand their newly acquired realm. This article reassesses the impact of the Conquest on the manuscript contexts of Anglo‐Saxon law, by reviewing the extant scholarship on the surviving manuscripts, the role of the vernacular in the 12th century, and on legal history relating to Anglo‐Saxon law in the period. Case studies of the scribal augmenting and updating of a turn of the 12th century manuscript collection of the laws are examined. Through these case studies, I illustrate the extent of scribal agency in the subtle adaption of the materiality and mise‐en‐page of the laws in their manuscript contexts. I argued for a manuscript‐led approach to the study of Anglo‐Saxon laws and related texts produced and used in the later 11th and first half of the 12th centuries.
Comparison of bicarbonate‐buffered fluid and isotonic saline solution as Cell Saver washing fluids for packed red blood cells
Authors: Huber Dirk , Witt Lars , Sümpelmann Robert , Heinze Larissa , Müller Thomas , Lichtinghagen Ralf , Osthaus Wilhelm A.
Published: August 2013

Objectives

Massive transfusion (MT) can cause severe electrolyte and acid–base disturbances in neonates and infants due to the unphysiological composition of packed red blood cells (PRBCs). Washing of the PRBCs using Cell Saver systems prior to MT is recommended for this reason.

Aim

The composition of normal saline (NaCl), the standard wash fluid for Cell Saver systems, is considerably different from that of physiological plasma. The aim of the study presented here was to investigate the effect of washing the PRBCs with a bicarbonate‐buffered hemofiltration solution (BB‐HS) in comparison with washing with NaCl and to evaluate the impact on electrolyte concentrations, acid–base balance and the stability of PRBCs.

Methods

In an experimental in vitro setting, PRBCs were washed with Cell Saver systems prepared with NaCl or BB‐HS as washing solutions. Before and after the washing procedure, electrolyte concentrations, acid–base parameters, adenosine triphosphate (ATP) and free hemoglobin (fHb) concentrations were measured.

Results

In both groups, the potassium concentrations decreased (baseline: 18.4 ± 5.17 mmol·l−1, end of study: NaCl 2.71 ± 1,81 mmol·l−1, BB‐HS 2.50 ± 1.54 mmol·l−1, P < 0.05) while the acid–base balance improved only in the BB‐HS‐group (baseline: base excess −21.6 ± 3.52 mmol·l−1, end of study: NaCl −30.2 ± 1.42 mmol·l−1, BB‐HS −7.51 ± 2.49 mmol·l−1, P < 0.05). Furthermore, markers of erythrocyte stability such as fHb and ATP concentrations were improved in the BB‐HS‐group.

Conclusions

Washing of PRBCs with BB‐HS rather than NaCl results in a more physiological composition with improvements of electrolyte concentrations, acid–base balance and erythrocyte stability.
Democratic Authority and the Boundary Problem
Authors: Simmons A. John
Published: August 2013

Theories of political authority divide naturally into those that locate the source of states' authority in the history of states' interactions with their subjects and those that locate it in structural (or functional) features of states (such as the justice of their basic institutions). This paper argues that purely structuralist theories of political authority (such as those defended by Kant, Rawls, and contemporary “democratic Kantians”) must fail because of their inability to solve the boundary problem—namely, the problem of locating the boundaries between different states' domains of authority in the natural or intuitive places.
Is Secularism Neutral?
Authors: Ahdar Rex
Published: August 2013

This article argues that secularism is not neutral. Secularization is a process, the secular state is a structure, whereas secularism is a political philosophy. Secularism takes two main forms: first, a “benevolent” secularism that endeavours to treat all religious and nonreligious belief systems even‐handedly, and, second, a “hostile” kind that privileges unbelief and excludes religion from the public sphere. I analyze theEuropean Court of Human Rights decision inLautsi vItaly, which illustrates these types. The article concludes that secularism as a political philosophy cannot be neutral, and the secular state is not neutral in its effects, standpoint, governing assumptions or treatment of religious truth claims.
What Is “Law,” if “the Law” Is not Something that “Is”? A Modest Contribution to a Major Question
Authors: Svantesson Dan Jerker B.
Published: August 2013

After proposing an alternative definition of what “law” (jurisprudential concept) is, this article demonstrates the impossibility of identifying “the law” (what law‐makers announce, relative to a particular jurisdiction) as something that is in a particular way. Rather, the law is a more or less abstract range of options. Drawing upon this conclusion, the article calls for a reassessment of how we view the role of law‐makers. We need to remove the mystery that surrounds the law so as to provide for greater transparency. This transparency can be gained by requiring law‐makers to declare their inescapable biases where they influence their lawmaking.
Histopathological study of the causes for failure of intrascleral prostheses in dogs and cats
Authors: Naranjo Carolina , Dubielzig Richard R.
Published: August 2013

Objective

To characterize the histopathological causes for failure of intrascleral prosthesis placement in dogs and cats.

Procedures

The Comparative Ocular Pathology Laboratory of Wisconsin database was searched to find canine and feline evisceration samples that were diagnosed with neoplasia. A second population included canine and feline scleral shells that were removed after an evisceration surgery had been performed. The causes for removal were divided into: neoplasia, corneal abnormalities, and other causes.

Results

In dogs, 163 of 1985 evisceration samples (8.21%) contained a neoplasm, whereas 17 of 88 (19.31%) evisceration samples in cats contained a neoplasm. In dogs, severe corneal disease was diagnosed in 38 of 80 scleral shells (46.25%) and neoplasia was diagnosed in 31 of 80 scleral shells (38.75%). Malignant melanoma was the most frequently diagnosed tumor, in 14 of 31 scleral shells. In cats, eight of 12 scleral shells contained a tumor (66.7%), with feline diffuse iris melanoma being diagnosed most commonly (six of eight shells). Two of 12 feline scleral shells had severe corneal disease (16.7%). Epithelial downgrowth, lining the inner aspect of the fibrous tunic, was seen in 14 of 38 canine scleral shells and in two of two feline scleral shells with severe corneal disease.

Conclusions

Severe corneal disease and neoplasia are the most common causes for intrascleral prosthesis failure in dogs, whereas neoplasia is the single most common cause for intrascleral prosthesis failure in cats.
Thermodynamics-Based Mean Value Model for Diesel Combustion
Authors: Lee Byungchan , Jung Dohoy , Kim Yong-Wha , van Nieuwstadt Michiel
Published: August 2013

A thermodynamics-based computationally efficient mean value engine model that computes ignition delay, combustion phases, exhaust temperature, and indicated mean effective pressure has been developed for the use of control strategy development. The model is derived from the thermodynamic principles of ideal gas standard limited pressure cycle. In order to improve the fidelity of the model, assumptions that are typically used to idealize the cycle are modified or replaced with ones that more realistically replicate the physical process such as exhaust valve timing, in-cylinder heat transfer, and the combustion characteristics that change under varying engine operating conditions. The model is calibrated and validated with the test data from a Ford 6.7 liter diesel engine. The mean value model developed in this study is a flexible simulation tool that provides excellent computational efficiency without sacrificing critical details of the underlying physics of the diesel combustion process.
Effects of Rotation and Channel Orientation on the Flow Field Inside a Trailing Edge Internal Cooling Channel
Authors: Pascotto Matteo , Armellini Alessandro , Casarsa Luca , Giannattasio Pietro , Mucignat Claudio
Published: August 2013

The flow field inside a trailing edge (TE) cooling channel for gas turbine blades has been numerically investigated with reference to the effects of channel rotation and orientation. The channel consists of a single passage with high aspect ratio cross-section. The flow entering from the hub is discharged through both the channel tip and inter-pedestal passages at the TE. A commercial 3D RANS solver including a κ–ω SST turbulence model has been used to simulate the isothermal steady airflow at 20000 Reynolds number in the case of static channel and for two rotation numbers (Ro = 0.23, 0.46) at varying the channel orientation with respect to the rotation axis (γ = 0°, γ = 22.5°, γ = 45°). The present work extends a previous experimental analysis performed by the authors on the same channel geometry, the results of which are used to validate the numerical model. Rotation effects are shown to alter significantly the distribution of both the mass flow in the inlet duct and the velocity along the channel height. This causes remarkable modifications of the 3D flow structures in the inter-pedestal passages and, in particular, the disappearance of the horseshoe vortices from the pedestal upstream face. Changing the channel orientation results in an attenuation of the rotation effects in the inlet duct and in the hub region of the TE.
Experimental-Based Redesigns for Trailing Edge Film Cooling of Gas Turbine Blades
Authors: Benson Michael , Yapa Sayuri , Elkins Chris , Eaton John K.
Published: August 2013

Magnetic resonance imaging experiments have provided the three-dimensional mean concentration and three component mean velocity field for a typical trailing edge film-cooling cutback geometry built into a conventional uncambered airfoil. This geometry is typical of modern aircraft engines and includes three dimensional slot jets separated by tapered lands. Previous analysis of these data identified the critical mean flow structures that contribute to rapid mixing and low effectiveness in the fully turbulent flow. Three new trailing edge geometries were designed to modify the large scale mean flow structures responsible for surface effectiveness degradation. One modification called the Dolphin Nose attempted to weaken strong vortex flows by reducing three dimensionality near the slot breakout. This design changed the flow structure but resulted in minimal improvement in the surface effectiveness. Two other designs called the Shield and Rounded Shield changed the land planform and added an overhanging land edge while maintaining the same breakout surface. These designs substantially modified the vortex structure and improved the surface effectiveness by as much as 30%. Improvements included superior coolant uniformity on the breakout surface which reduces potential thermal stresses. The utilization of the time averaged data from combined magnetic resonance velocimetry (MRV) and concentration (MRC) experiments for designing improved trailing edge breakout film cooling is demonstrated.
Computational Analysis of Side-Wall Heat Transfer of a Turbine Blade Internal Cooling Passage With Truncated Ribs on Opposite Walls
Authors: Li Shian , Xie Gongnan , Sundén Bengt , Zhang Weihong
Published: August 2013

A problem involved in the increase of the turbine inlet temperature of gas turbine engine is the failure of material because of excessive thermal stresses. This requires cooling methods to withstand the increase of the inlet temperature. Rib turbulators are often used in the mid-section of internal cooling ducts to augment the heat transfer from blade wall to the coolant. This study numerically investigates side-wall heat transfer of a rectangular passage with the leading/trailing walls being roughened by staggered ribs whose length is less than the passage width. Such a passage corresponds to the internal cooling passage near the leading edge of a turbine blade. The inlet Reynolds number is ranging from 12,000 to 60,000. The detailed 3D fluid flow and heat transfer over the side-wall are presented. The overall performances of several ribbed passages are evaluated and compared. It is found that the side-wall heat transfer coefficients of the passage with truncated (continuous) ribs on opposite walls are about 20%–27% (28%–43%) higher than those of a passage without ribs, while the pressure loss could be reduced compared to a passage with continuous ribs. It is suggested that the usage of truncated ribs is a suitable way to augment the side-wall heat transfer and improve the flow structure near the leading edge.
Characterization of Metallic W-Seals for Inner to Outer Shroud Sealing in Industrial Gas Turbines
Authors: Sarawate Neelesh , Wolfe Chris , Sezer Ibrahim , Ziegler Ryan , Chupp Raymond
Published: August 2013

Sealing and clearance control are two of the most cost effective methods to reach desired goals of efficiency, power output, operational life and emission levels in turbomachinery. Metallic seals such as W seals are widely used in gas turbines to seal axial gaps between adjacent static components such as shrouds and nozzles. Often the seals are characterized in a laboratory controlled environment, and the test results are used in modeling the secondary flows. However in real operating conditions, the static components can shift relative to each other creating misalignments that result in non-uniform sealing surfaces. One such application includes sealing between the stage 1 outer and inner shrouds. The inner shrouds are often stacked with axial misalignments relative to the neighboring shrouds due to manufacturing and assembly tolerances. Characterizing the effect of shroud misalignments on the W seal leakage is reported in this article. A comprehensive test matrix is conducted to characterize W seal leakage for four different magnitudes of shroud offsets, three types of seals having varying stiffness, and two compression levels. It is observed that the W seal leakage is fairly insensitive to the compression levels and the type of seal at zero misalignments. The seal leakage increases substantially with misalignments up to four times than for a perfectly aligned condition. The seal behavior also changes with increasing offsets. The seal exhibits typical properties of a positively loaded member for small misalignments, however, the behavior resembles a loose seal for larger misalignments. For a positively loaded seal, the effective clearance of the seal increases with pressure differential, whereas in case of a loose seal, the effective clearance decreases with increasing pressure differential. The effect of misalignments must be considered when modeling the seal in the engine flow models using a weighted average of the effective clearance.
Uncertainty Quantification: A Stochastic Method for Heat Transfer Prediction Using LES
Authors: Carnevale M. , Montomoli F. , D’Ammaro A. , Salvadori S.
Published: August 2013

In Computational Fluid Dynamics (CFD) is possible to identify namely two uncertainties: epistemic, related to the turbulence model, and aleatoric, representing the random-unknown conditions such as the boundary values and or geometrical variations. In the field of epistemic uncertainty, Large Eddy Simulation (LES and DES) is the state of the art in terms of turbulence closures to predict the heat transfer in internal channels. The problem concerning the stochastic variations and how to include these effects in the LES studies is still open.

In this paper, for the first time in literature, a stochastic approach is proposed to include these variations in LES. By using a classical Uncertainty Quantification approach, the Probabilistic Collocation Method is coupled to Numerical Large Eddy Simulation (NLES) in a duct with pin fins. The Reynolds number has been chosen as a stochastic variable with a normal distribution. It is representative of the uncertainties associated to the operating conditions, i.e. velocity and density, and geometrical variations such as the pin fin diameter. This work shows that by assuming a Gaussian distribution for the value of Reynolds number of +/−25%, is possible to define the probability to achieve a specified heat loading under stochastic conditions, which can affect the component life by more than 100%.

The same method, applied to a steady RANS, generates a different level of uncertainty. This procedure proves that the uncertainties related to the unknown conditions, aleatoric, and those related to the physical model, epistemic, are strongly interconnected. This result has directed consequences in the Uncertainty Quantification science and not only in the gas turbine world.
Procedure for Calculation of Component Thermal Loads for Running Clearances of Heavy-Duty Gas Turbines
Authors: Bozzi Luca , Perrone Andrea , Giacobone Luca
Published: August 2013

The energy market development in the last decade has been influenced by several driving factors. To meet the strict customers’ requirements (related to low emissions, flexibility and high performances), operate gas turbine plants safely over a variety of off-design operating conditions has been fundamental. Accordingly, accurate evaluation of running clearances in stationary and transient conditions plays a significant role. On the other hand, the study of heat transfer in turbo-machinery is a fundamental activity to study the implications of off-design operating on components’ lifing.

Focus of the paper is the analysis of variations of components’ wall temperature and clearances due to the fluctuation of thermal loads acting on gas turbines components during operation.

The study is divided into two main sections: heat transfer analysis allows evaluating thermal loads and then a FEM analysis is performed in order to calculate the radial and axial clearances between rotor components and casing.

Thermal loads are obtained by a computational method based on heat transfer correlations. Parametric curves have been developed to calculate variations of thermal loads in transient conditions from steady-state data obtained by the correlative computational tool.

The two procedures for heat transfer analysis and evaluation of clearances have been validated against experimental data in several operating conditions. In particular, relative and absolute movements of rotor and turbine casing have been measured by means of proxy-meter probes located into the turbine bearing casing.
Rim Seal Ingestion in a Turbine Stage From 360-Degree Time Dependent Numerical Simulations
Authors: Wang Cheng-Zhang , Mathiyalagan Senthil Prasad , Johnson Bruce V. , Glahn J. Axel , Cloud David F.
Published: August 2013

Numerical simulations of turbine rim seal experiments are conducted with a time-dependent, 360-degree CFD model of the complete turbine stage with a rim seal and cavity. The turbine stage has 22 vanes and 28 blades and is modeled with a uniform flow upstream of the vane inlet, a pressure condition downstream of the blades and three coolant flow conditions previously employed during experiments at Arizona State University. The simulations show the pressure fields downstream of the vanes and upstream of the blades interacting to form a complex pressure pattern above the rim seal. Circumferential distributions of 15 and 17 sets of ingress and egress velocities flow through the rim seal at the two modest coolant flow rate conditions. These flow distributions rotate at wheel speed and are not associated with the numbers of blades or vanes. The seal velocity distribution for a high coolant flow rate with little or no ingestion into the stator wall boundary layer is associated with the blade pressure field. These pressure field characteristics and the rim seal ingress/egress pattern provide new insight to the physics of rim seal ingestion. Flow patterns within the rim cavity have large cells that rotate in the wheel direction at a slightly slower speed. These secondary flows are similar to structures noted in previous a 360-degree model and large sector models but not obtained in a single blade or vane sector model with periodic boundary condition at sector boundaries. The predictions of pressure profiles, sealing effectiveness and cavity velocity components are compared with experimental data.
Effect of Cross-Shaped Circular Jet Array on Impingement Heat Transfer
Authors: Yamane Yoshisaburo , Yamamoto Makoto , Honami Shinji
Published: August 2013

The purpose of this study is to clarify heat transfer characteristics for the high cooling performance with multiple jet impingement. In the present study, the influence of the interaction among adjacent impinging jets on heat transfer of target surface is experimentally investigated. The study is focused on the effect of jet injection shape on the heat transfer. 3×3 square array of cross-shaped circular jet is tested. Injection distances L are 2 and 4 jet hole diameters, and jet-to-jet spacing S are 4, 6 and 8 jet hole diameters. Experiments are conducted for a constant Reynolds number Re = 4,680 based on the jet hole diameter. Steady state thermochromic liquid crystal technique is employed to measure local and area averaged Nusselt numbers. The flow field is visualized by smoke-wire and oil flow techniques. It is found that the cross-shaped circular jet array improves heat transfer at the intermediate area enclosed by four impinging jets compared to that of circular jet array at the narrow injection distance. In the case of cross-shaped circular jet array, the wall jet produces a stronger turbulence than that of circular jet, which makes the heat transfer push up toward the apex of square detachment line at injection distance L/D = 2 and jet-to-jet spacing S/D = 6 and 8.
Density Ratio Effects on the Cooling Performances of a Combustor Liner Cooled by a Combined Slot/Effusion System
Authors: Andreini A. , Caciolli G. , Facchini B. , Tarchi L. , Coutandin D. , Peschiulli A. , Taddei S.
Published: August 2013

The aim of the present study is to investigate the effects of density ratio between coolant and mainflow on a real engine cooling scheme of a combustor liner. Measurements of heat transfer coefficient and adiabatic effectiveness were performed by means of a steady-state Thermochromic Liquid Crystals (TLC) technique; experimental results were used to estimate, through a 1D thermal procedure (Therm1d), the Net Heat Flux Reduction and the overall effectiveness in realistic engine working conditions.

In order to reproduce a representative value of combustor coolant to mainstream density ratio, tests were carried out feeding the cooling system with carbon dioxide (CO2), while air was used in the main channel; to highlight the effects of density ratio and, as a consequence, to distinguish between the influence of blowing ratio and velocity ratio, tests were replicated using air both as coolant and mainstream and results were compared.

The experimental analysis was performed on a test article replicating a slot injection and an effusion array with a central large dilution hole. Test section consists of a rectangular cross-section duct and a flat perforated plate provided with 272 holes arranged in 29 staggered rows (d = 1.65 mm, α = 30°, L/d = 5.5). Furthermore a dilution hole (D = 18.75 mm) is located at the 14th row; both effusion and dilution holes are fed by a channel replicating a combustor annulus. The rig allows to control mainstream and coolant flow parameters, especially in terms of Reynolds number of mainstream and effusion holes. Located upstream the first effusion row, a 6.0 mm high slot ensures the protection of the very first region of the liner.

Experiments were carried out imposing several values of effusion blowing and velocity ratios within a range of typical modern engine working conditions (BReff/VReff = 1.5; 3.0; 5.0; 7.0) and keeping constant slot flow parameters (BRsl ≈ 1.5).

Results point out the influence of density ratio on film cooling performance, suggesting that velocity ratio is the driving parameter for the heat transfer phenomena; concerning the effectiveness, results show that the adiabatic effectiveness is less sensitive to the cooling flow parameters, especially at the higher blowing/velocity ratios.
Method for 1-D Rotating/Stationary Disk Cavity Heat Transfer Analysis With Partial Flow Ingestion in a Gas Turbine
Authors: Hsia Kuo-Ting , Garner Chad , Vogel Gregory
Published: August 2013

The interface between rotating and stationary components in a gas turbine is commonly called “disk cavities”. In pursuit of a performance benefit from Secondary Air Flow System (SAF) flow reduction, rotating/stationary disk cavity flow ingestion management in the turbine section becomes an important subject.

To completely avoid ingestion, large amount of purging flow is utilized which reduces engine performance. Too much ingestion and the risk of reduced engine durability becomes an issue. Therefore, a partial ingestion condition is desired for optimizing SAF for performance. Typical methodology would be analysing purging flow using 3-D computational fluid dynamics (CFD) modeling in conjunction with engine test data to validate the design and ensure optimal SAF partial ingestion. This approach puts a very heavy demand on computational resources even at steady state. To extend the practice into a transient and unsteady flow field to attempt full design optimization will be even more taxing on computational resources and analysis labor time.

An quick alternative would be using a 1-D flow solver for the task in conjunction with baseload main gas path circumferential pressure variation either from main flow path 3D CFD or engine test data. Unfortunately, currently there are no 1-D flow solvers can resolve the poly-directional nature of partial flow ingestion. This paper presents a quick and reliable alternative using a numerical method for augmenting a 1-D flow solver to resolve the partial flow ingestion situation. This is used in conjunction with the 1-D flow solver to resolve the bulk cavity temperature and heat transfer in the disk cavity.

The results of this augmented 1-D flow solver show excellent agreement to field measurement data and 3-D CFD solutions. The tool enables a very realistic transient thermal analysis with partial flow ingestion at a fraction of the cost and analysis time of a full 3-D CFD analysis. This enables a faster design optimization with multiple iteration of a turbomachinery disk cavity with partial flow ingestion.
Impact of an Upstream Film-Cooling Row on Mitigation of Secondary Combustion in a High Fuel-Air Environment
Authors: Bohan Brian T. , Blunck David L. , Polanka Marc D. , Kostka Stanislav , Jiang Naibo , Roy Sukesh , Stouffer Scott D.
Published: August 2013

In advanced gas turbine engines that feature very short combustor sections, an issue of fuel-rich gases interacting with downstream components exists. In all of these engines there are regions downstream of the primary combustion section that will require the use of film-cooling in the presence of incompletely reacted exhaust. This will lead to the possibility of additional combustion reactions resulting from the combination of unburnt fuel and oxygen-rich cooling films. Research has been accomplished to understand this secondary reaction process. This experimental film-cooling study expands the previous investigations by attempting to reduce or remove the negative effects that result from secondary combustion in the coolant film. An upstream row of holes was added to a row of previously tested shaped coolant holes to understand if the reactions could be mitigated at the downstream locations. Several combinations of cooling schemes were investigated and the heat flux downstream was measured. Planar Laser Induced Fluorescence (PLIF) was used to measure OH concentration in the combustion zones to understand where the reactions occurred. It was discovered that creating a full sheet of air upstream could effectively protect the downstream row from the negative impacts of the fuel-rich crossflow.
Impact of Trench and Ramp Film Cooling Designs to Reduce Heat Release Effects in a Reacting Flow
Authors: DeLallo Michael R. , Polanka Marc D. , Blunck David L.
Published: August 2013

High freestream fuel-air ratios are a recent area of concern in film cooling due to the potential for heat release on the surface of film cooled turbine components. This investigation compared the potential for heat release from three cooling designs: namely a fanned, a trenched, and a ramped. Measurements of heat flux to the downstream surface are provided when subjected to a reacting mainstream flow. This work furthermore studied the effect of multiple injection points in series along the surface of a flat plate. The extremes of either an upstream set of normal holes or an upstream slot is evaluated on its ability to protect the downstream coolant flow from the fuel rich mainstream. Results are presented in terms of heat flux, augmentation of heat flux, and normalized temperature which quantifies the magnitude, change, and potential change of downstream heat release, respectively. Downstream heat release was expected to be a result of local equivalence ratio and characteristic chemical and flow times. Results suggest the method of coolant injection to be more impactful on local equivalence ratio than the volume of coolant injected.
High Rotation Number Effect on Heat Transfer in a Leading Edge Cooling Channel With Three Channel Orientations
Authors: Huang Szu-Chi , Liu Yao-Hsien
Published: August 2013

Heat transfer in a leading edge, triangular shaped cooling channel with three channel orientations under high rotation numbers is experimentally studied. Continuous ribs and V-shaped ribs, both at 45° rib angle of attack, are applied on the leading and trailing surfaces. For each rib case, three channel orientations (90°, 67.5°, and 45°) with respect to the plane of rotation are tested. The rib height to hydraulic diameter ratio (e/Dh) is 0.085 and the rib pitch to height ratio (P/e) is 9. Reynolds numbers are from 15000 to 25000, and the rotation numbers are from 0 to 0.65. Results show that the heat transfer variation is influenced by the combined effects of rib configuration and channel orientation. Effect of channel orientation influences local heat transfer distribution inside this triangular channel, and heat transfer is enhanced gradually on the leading surface when the channel orientation varies from 90° to 45° for both ribbed cases in this study.
Effect of Endwall Contouring on a Transonic Turbine Blade Passage: Part 2—Heat Transfer Performance
Authors: Panchal Kapil V. , Abraham Santosh , Ekkad Srinath V. , Ng Wing , Lohaus Andrew S. , Crawford Michael E.
Published: August 2013

Contouring of turbine endwalls has been widely studied for aerodynamic performance improvement of turbine passages. However, it is equally important to investigate the effect of contouring on endwall heat transfer, because a substantial increase in endwall heat transfer due to contouring will render the design impractical. In this paper, the effect of contouring on endwall heat transfer performance of a high-turning HP-turbine blade passage, operating under transonic exit Mach number conditions, is reported. Three endwall geometries were experimentally investigated at three different passage exit Mach numbers, 0.71, 0.88(design) and 0.95, for their heat transfer performance. One endwall is a non-contoured baseline endwall and the other two are contoured endwall geometries. One of the contoured endwall geometry was generated with the goal of reduction in stagnation pressure losses and the other was generated with the goal of reduced overall heat transfer through the endwall. The experiments were carried out in Virginia Tech’s transient, blow down, transonic linear cascade facility. Endwall surface temperatures were measured using infrared thermography technique. Local heat transfer coefficient values were calculated using the measured temperatures. The heat transfer coefficient values were then related to the endwall geometries using a camera matrix model. The measurement technique and the methodology for the post-processing of the heat transfer coefficient data have been presented in detail. Details of the flow behavior for these endwalls were obtained using CFD simulations and have been used to assist the interpretation of the experimental results. In this study, the heat transfer performance of the contoured endwalls in comparison to the non-contoured baseline case is presented. Both the contoured endwalls demonstrated a significant reduction in the overall average heat transfer coefficient values. The surface heat transfer coefficient distributions also indicated a reduction in the level of hot spots for most of the endwall surface. However, increase in the heat transfer coefficient values was observed especially in the area near the leading edge. The results indicate that, in addition to a probable improvement in aerodynamic performance, endwall contouring may also be used to improve the heat transfer performance of turbine passages. Additionally, aerodynamic behavior of these endwalls is discussed in detail in the companion paper GT2012-68425, “Effect of endwall contouring on a transonic turbine endwall: Part 1 – Aerodynamic performance.”
The Influence of HPT Forward Disc Cavity Platform Axial Overlap Geometry on Mainstream Ingestion
Authors: Mirzamoghadam A. V. , Giebert D. , Molla-Hosseini K. , Bedrosyan L.
Published: August 2013

In this paper, 3D unsteady and mixing plane CFD simulations including the mainstream full stage on two tested configurations plus a third cavity geometry variance are reported. The sector models were run at test conditions and compared with the corresponding matched Network 1-D flow model to derive the sensitivity of HPT stage forward disc cavity platform axial overlap geometry and supplied purge flow to cavity ingestion dynamics. The first configuration includes no axial overlap (i.e. ΔX/ΔR = 0); the second configuration increases axial overlap by 70% (ΔX/ΔR = 1.82); the third configuration has a larger rim cavity axial spacing and a smaller platform axial overlap (i.e. ΔX/ΔR = 1.67). The unsteady and mixing plane 3D CFD models of the three configurations are run across supplied purge flows ranging from nominal to 35% of the nominal. This was done to obtain a good comparison and to justify the need for unsteady solutions in disc cavity ingestion studies. For each configuration, the CFD predicted mainstream pressure pulse decay profile inside the cavity along with absolute, relative, and static temperatures related to the amount of ingestion that mixes with the supplied flow at several radial heights in the cavity are extracted on a time-averaged and pitch-wise averaged basis. The applied CFD-Network process yields cavity sealing effectiveness versus supplied purge flow and validates platform conductance factors used in 1-D Network flow model. In particular, the unsteady CFD results for the tested configurations were able to reproduce the Network-matched rim cavity effectiveness data at the critical location more closely. The sensitivity results indicate that although, the zero overlap geometry (configuration-1) has insufficient purge flow as evident by the low upper cavity effectiveness, the amount becomes sufficient as the platform axial overlap increases for configuration-2. The influence of increasing rim cavity axial spacing (configuration-3) allows for the same effectiveness to be achieved under a smaller platform axial overlap and lower purge flow supply.
Effect of Ingestion on Temperature of Turbine Discs
Authors: Pountney Oliver J. , Sangan Carl M. , Lock Gary D. , Owen J. Michael
Published: August 2013

This paper describes experimental results from a research facility which experimentally models hot-gas ingress into the wheel-space of an axial turbine stage with an axial-clearance rim seal. Thermochromic liquid crystal (TLC) was used to determine the effect of ingestion on heat transfer to the rotating disc; as far as the authors are aware, this is the first time that the measured effects of ingestion on adiabatic temperature have been published. An adiabatic effectiveness for the rotor was defined, and this definition was used to determine when the effect of ingress was first experienced by the rotor. Concentration measurements on the stator were used to determine the sealing effectiveness of the rim seal, and transient heat transfer tests with heated sealing air were used to determine the adiabatic effectiveness of the rotor. The thermal buffer ratio, which is defined as the ratio of the sealing flow rate when ingress first occurs to that when it is first experienced by the rotor, was shown to depend on the turbulent flow parameter. The local Nusselt numbers, Nu, which were measured on the rotor, were significantly smaller than those for a free disc; they decreased as the sealing flow rate decreased and as the ingress correspondingly increased. The values of Nu and adiabatic effectiveness obtained in these experiments provide data for the validation of CFD codes but caution is needed if they (particularly the values of Nu) are to be extrapolated to engine conditions.
Shear Layer Flame Stabilization Sensitivities in a Swirling Flow
Authors: Chterev I. , Foley C. W. , Noble D. R. , Ochs B. A. , Seitzman J. M. , Lieuwen T. C.
Published: August 2013

A variety of different flame configurations and heat release distributions can exist in high swirl, annular flows. Each of these different configurations, in turn, has different thermoacoustic sensitivities and influences on combustor emissions, nozzle durability, and liner heating. These different configurations arise because at least three flame stabilization locations are present, associated with the inner and outer shear layers of the annulus, and the stagnation point of the vortex breakdown region. This paper focuses on the sensitivities of the outer shear layer stabilization point to bulkhead temperature, flow velocity, swirl number, preheat temperature, and fuel/air ratio. It also characterizes the hysteresis that is present in conditions where the outer shear layer locally re-attaches and blows off. The sensitivities to bulkhead temperature, preheat temperature and fuel/air ratio follow the expected trends. Moreover, the strong bulkhead temperature sensitivities show that computations must include heat transfer to combustor hardware in order to capture flame stabilization correctly. The preheat temperature and fuel/air ratio sensitivities are captured with detailed kinetics calculations of the extinction stretch rate of the mixture. Somewhat counter intuitively, there is little variation in transition conditions with swirl number for the Sm∼0.6 and 0.8 swirlers analyzed here. Finally, velocity sensitivities are in many cases much weaker than what would be predicted assuming that the fluid mechanic straining time scales as 1/u.
Conjugate Heat Transfer Predictions of Effusion Cooling: The Influence of Injection Hole Size on Cooling Performance
Authors: Oguntade H. I. , Andrews G. E. , Burns A. D. , Ingham D. B. , Pourkashanian M.
Published: August 2013

Conjugate heat transfer CFD was undertaken on the influence of hole size on effusion cooling. The coupled thermal mixing between the hot-gas and coolant jets and the heat transfer within the effusion walls were modelled using the ANSYS FLUENT software. The heat and mass transfer analogy was employed to predict the adiabatic film cooling effectiveness separately from the overall cooling effectiveness by adding a tracer gas to the coolant air and predicting its concentration at the inner wall surface. The geometries predicted were those investigated experimentally by Andrews and his co-workers using a 152mm length of effusion cooling with 10 rows of square array holes in a flat metal wall. Effusion of X/D of 4.6 and 1.85 were investigated at constant X, the large hole diameter at the lower X/D drastically reduces the hole blowing rate and this improves the film cooling and deteriorates the internal wall cooling. The CFD predictions enable these qualitative effects to be investigated in more detail. The agreement of predictions and experiment was very good at low coolant mass flow rates, but under-predicted the measurements at higher flow rates by about 5–12%. The experimental results showed that the smaller X/D gave a better overall cooling performance and the predictions also showed this, but demonstrated that it was not just to due improved effusion film cooling as there was not the expected large reduction in internal wall cooling.