bluuebunny/crossref_metadata_2025_split huggingface dataset:
Towards an Understanding of Traverse Migration in the High Pressure Stage of a Gas Turbine: Effects of Geometry Fidelity and Turbulence Modelling
Authors: Srinivasan Karthik , Bather Simon 
Published: February 2018

The aerodynamic design of a turbine stage requires the accurate prediction of radial profiles of pressure, temperature and velocity at various axial locations within the turbine stage. In the case of hot gas path components like the High Pressure Turbine (HPT), which is located downstream of the combustor, the location of the hot spot and its migration through the stage is critical in arriving at an appropriate aerofoil cooling flow requirement and distribution. In addition, the migration of the flow and the evolution of the temperature traverse through the stage impacts the aerodynamic efficiency of the stage. This is predicted using CFD techniques and has been an inevitable part of the design process.
Typically, the fidelity of the computational model evolves with the component design. During early design phases, simplistic geometry is used for the simulations and progressively the fidelity is increased to resolve the geometrical features of interest, like that of the end wall film cooling and rim seal cavity geometries. The present paper provides an improved understanding of the temperature evolution in a HP turbine stage, particularly with respect to the geometry fidelity and the choice of turbulence models. Computational analyses are carried out using the Rolls-Royce in-house CFD solver, HYDRA.
The geometry fidelity comparisons dealt with are discrete endwall cooling holes vs. equivalent slot and explicit cavity resolution vs. patch surface techniques. In addition, comparisons of traverses predicted using the k-Epsilon realizable turbulence model and SST k-Omega model are presented and debated. The influence of the geometry fidelity and turbulence model on the evolution of radial distribution through the stage is presented along with supporting flow field interpretations. It is concluded that the slot representation of platform cooling flow is satisfactory to replicate the overall traverse at the exit of the High Pressure Nozzle during early stages of design. The near wall temperature gradient would be lower and in the present case the Horse Shoe Vortex (HSV) at the endwalls are not observed with discrete cooling flow modelling which indicates probable aerodynamic impact. The choice of turbulence modelling could have significant impact on the traverse prediction in comparison to the geometry approximations.
Prediction of Failure Loads for Fasteners Under Combined Loading Using Finite Element Analysis
Authors: Moodambail Anoop , Neri Remo , Venkataramanan Srinivasan , Sethy Premanjan , Bysani Prasanth Kumar 
Published: February 2018

Fasteners are typically designed to withstand axial or shear loads in a joint assembly. However, in selected scenarios fasteners are subjected to combination of axial, shear and bending loads. The criterion typically used to predict the ultimate failure of a member in combined shear and tension is based on the maximum normal stress and maximum shear stress theories. Test conducted by NASA found that under joint separation condition, the existing combined loading failure criteria over-predicts the strength of the bolts.
This paper develops the methodology of predicting fastener failure using finite element analysis with elasto-plastic material properties under combination of axial load and shear using a strain-based failure criterion. This methodology is validated with NASA test results. Elasto-plastic finite element analysis is shown to be an effective way to simulate test results. In order to define the full range capability values for different combinations of shear and tension loads, several cases were run with different load values. The study further extends to identify new limiting criteria under a combination of axial load and offset shear conditions for a selected stud.
The load capability can be used to calculate margin of safety for flange-joints. Further this approach can be generalized for application to all pins and fasteners subjected to combined shear and tension loads.
Structural Dynamic Behavior of Axial Compressor Rotor
Authors: Satish Kumar Subramani , Ganguli Ranjan , Kandagal Siddanagouda Basanagouda , Jana Soumendu 
Published: February 2018

The vibrations involved in a typical axial compressor rotor in an aircraft engine are complex. Generally, the compressor blades are arranged in a cantilever type configuration. It is also known that the amplitude of vibration is highest near the tip section of the shroudless blade. Compressors are limited by aerodynamic instabilities such as rotating stall and surge. Rotating stall generally initiates near the tip region of the compressor. Blade vibrations coupled with aerodynamic instabilities will lead to a catastrophic scenario of flutter that is asynchronous to the rotor speed. This aeroelastic interaction is detrimental if not taken into consideration. Knowledge of vibration characteristics of the compressor rotor will help in mapping the flutter zone for safe operation.
The modal characteristics of the transonic axial compressor rotor available at the Axial Flow Compressor Research (AFCR) facility of National Aerospace Laboratories (NAL) are established in this study. A cyclic-symmetric pre-stressed modal analysis is performed on a single sector of the compressor rotor consisting of a shroudless blade connected to the disk with a pin type dovetail arrangement for different speeds. The main diagnostic charts for turbomachinery vibration i.e., Campbell and Interference diagrams are generated for various speeds and harmonic indices/ nodal diameters of the compressor rotor. The critical crossings of the engine order excitation lines over the natural frequencies of the blade are highlighted.
Experimental modal investigations and analysis are carried out on the compressor rotor at the stationary condition and for two different boundary conditions. First, the blade alone modal characteristics under the free-free condition are established. Later, the complete blade-disk assembly mounted on a base test-stand is used to investigate the cantilever fixed-free boundary condition of the chosen blade.
The modal characteristics are established by performing impact hammer experiments. Blade excitation is provided by a calibrated Dytran make impact hammer and the response is measured using a calibrated accelerometer.
The structural dynamic data acquisition hardware and software from OROS is used for determining the natural frequencies, mode shapes and structural damping for each mode of the compressor rotor. There is a good agreement in the natural frequencies and mode shapes established using experiment and numerical methods for the first three modes investigated. Modal Assurance Criteria (MAC) analysis is carried out for two different modal identification algorithms to compare the mode shapes.
CFD Analyses of Flow in a Gas Turbine Combustor Swirl Cup
Authors: Karuppannan Srinivasan , Mehul Bhirud , Sivaramakrishna Gullapalli , Navindgi Raju D. , Muthuveerappan N. 
Published: February 2018

Swirl cups (hybrid atomizers) are being widely employed in aero gas turbine engine combustors for their established merits in terms of achieving satisfactory atomization over the entire combustor operating regime. Even though several investigators have worked on development of these swirl cups, there is a scanty data reported in literature relevant to their design.
In the present study, flow behavior in a swirl cup assembled in a confined chamber similar to a gas turbine combustor has been analyzed. Flow analysis has been carried out using ANSYS Fluent and turbulence has been modeled using Realizable k-ϵ model. Six swirl cup configurations have been analyzed; mass flow ratio between primary and secondary swirler and venturi converging area ratio have been varied. The effect of these parameters on downstream flow field has been studied by analyzing the profiles of axial, tangential and radial velocities downstream of swirl cup. The size and shape of the recirculation zone has been analyzed and reported for all configurations. Also, the mass flow recirculated by swirl cup has been estimated and compared amongst the configurations analyzed. Data thus generated is very useful in designing such swirl cups of gas turbine combustors.
Optimization of FLADE Variable Cycle Engine Performance Based on Improved Differential Evolution Algorithm
Authors: Xiao-bo Zhang , Zhan-xue Wang 
Published: February 2018

In this paper, a double bypass variable cycle engine with FLADE (Fan on Blade) is considered. The FLADE VCE is one of the research hotspots for future military and civil aircraft power device, which shows outstanding performance advantages. Compared to the mixed-flow turbofan, FLADE VCE is more complex than conventional aero-engine for its multi-components and multi-variable parts, which make it difficult to modeling and optimization.
For getting the performance of FLADE VCE, the model for engine performance simulation is researched. The method for FLADE performance simulation and the steady-state performance simulation model for FLADE VCE are developed. And a component-based engine performance simulation system is established based on object-oriented modeling method.
For obtaining the optimal integrated performance of FLADE VCE, suitable optimization method is required. Unfortunately, the optimization of FLADE VCE is a non-linear non-differentiable problem, which makes it difficult to solve by conventional deterministic optimization method. In order to solve this problem, the differential evolution (DE) algorithm is considered. To overcome the limitations of original DE algorithm, an improved DE algorithm with modifying mutation operator is proposed by this paper. The FLADE VCE optimization problem is solved by employing the improved DE algorithm.
Performance Evaluation of a Turbocharger Compressor by Varying the Exit Width, Eye Tip Radius and Extending the Shroud to Study Their Impact Using Computational Modelling
Authors: John Jerry Thomas , Mohanan Nikhil , Velayudhan A. K. D. 
Published: February 2018

Modern Internal combustion engines require high pressure ratios to perform efficiently as well as to reduce emissions. For such applications, a centrifugal compressor with high pressure ratio and broader operating range may be employed. The impeller design of such compressors plays a vital role in producing the efficient operation and hence today’s research focus rigorously over its design.
The objective of the current investigation is to study the performance of centrifugal compressors based on variation in exit width, eye tip radius and shroud extension. Shroud extension have previously found to generate higher pressure rise at the same time have the least amount of losses. The pressure ratio, power and torque requirement, isentropic efficiency and thermal aspects were the main considerations for the study.
Study of Condensate Generated During Direct Metal Laser Sintering
Authors: Chandra Achinadka Jagadish 
Published: February 2018

DMLS (Direct Metal Laser Sintering), an additive manufacturing technology, is increasingly becoming popular to build intricate high quality functional parts & rapid prototypes. DMLS technology uses a high intensity laser to build components layer by layer, directly from metal powder. CAD data is directly converted to part without the need for tooling. It is possible to build internal features and passages that are not possible in conventional manufacturing routes.
The process generates significant amount of condensate due to vaporization and suction applied to build chamber. Typically as much as 30% of the weight of powder ends up as condensate. The condensate so generated cannot be directly recycled. This results in significant reduction in profitability and process efficiency.
This study pertains to 18% Ni Maraging Steel grade C300, which commonly used in DMLS process. Maraging Steel is used extensively to build functional parts by DMLS process especially for Tool and Die applications.
In the present study chemistry, particle size distribution & morphology of the condensate was studied & compared with the powder. Parts were built using condensate and chemical, physical, mechanical, microstructure and XRD studies were done. These properties were compared with properties of parts built using fresh powder.
No difficulty was encountered in building parts using condensate. However, hardness and tensile properties were found to be inferior, thus it is not possible to recycle the condensate directly.
Present research investigates the cause of difference in these properties.
Genetic Polymorphisms in Cytokine Genes in Colombian Patients with Ocular Toxoplasmosis
Authors: Naranjo-Galvis C. A. , de-la-Torre A. , Mantilla-Muriel L. E. , Beltrán-Angarita L. , Elcoroaristizabal-Martín X. , McLeod R. , Alliey-Rodriguez N. , Begeman I. J. , López de Mesa C. , Gómez-Marín J. E. , Sepúlveda-Arias J. C. 
Published: February 2018

ABSTRACTToxoplasmosis is caused by infection with the protozoan parasiteToxoplasma gondii, which has the capacity to infect all warm-blooded animals worldwide. Toxoplasmosis is a major cause of visual defects in the Colombian population; however, the association between genetic polymorphisms in cytokine genes and susceptibility to ocular toxoplasmosis has not been studied in this population. This work evaluates the associations between polymorphisms in genes coding for the cytokines tumor necrosis factor alpha (TNF-α) (rs1799964, rs1800629, rs1799724, rs1800630, and rs361525), interleukin 1β (IL-1β) (rs16944, rs1143634, and rs1143627), IL-1α (rs1800587), gamma interferon (IFN-γ) (rs2430561), and IL-10 (rs1800896 and rs1800871) and the presence of ocular toxoplasmosis (OT) in a sample of a Colombian population (61 patients with OT and 116 healthy controls). Genotyping was performed with the “dideoxynucleotide (ddNTP) primer extension” technique. Functional-effect predictions of single nucleotide polymorphisms (SNPs) were done by using FuncPred. A polymorphism in the IL-10 gene promoter (−1082G/A) was significantly more prevalent in OT patients than in controls (P= 1.93e−08; odds ratio [OR] = 5.27e+03; 95% confidence interval [CI] = 3.18 to 8.739; Bonferroni correction [BONF] = 3.48e−07). In contrast, haplotype “AG” of the IL-10 gene promoter polymorphisms (rs1800896 and rs1800871) was present at a lower frequency in OT patients (P= 7e−04; OR = 0.10; 95% CI = 0.03 to 0.35). The +874A/T polymorphism of IFN-γ was associated with OT (P= 3.37e−05; OR = 4.2; 95% CI = 2.478 to 7.12; BONF = 6.07e−04). Haplotype “GAG” of the IL-1β gene promoter polymorphisms (rs1143634, rs1143627, and rs16944) appeared to be significantly associated with OT (P= 0.0494). The IL-10, IFN-γ, and IL-1β polymorphisms influence the development of OT in the Colombian population.
Nonspecific CD8
+
T Cells and Dendritic Cells/Macrophages Participate in Formation of CD8
+
T Cell-Mediated Clusters against Malaria Liver-Stage Infection
Authors: Akbari Masoud , Kimura Kazumi , Bayarsaikhan Ganchimeg , Kimura Daisuke , Miyakoda Mana , Juriasingani Smriti , Yuda Masao , Amino Rogerio , Yui Katsuyuki 
Published: February 2018

ABSTRACT

CD8
+
T cells are the major effector cells that protect against malaria liver-stage infection, forming clusters around
Plasmodium
-infected hepatocytes and eliminating parasites after a prolonged interaction with these hepatocytes. We aimed to investigate the roles of specific and nonspecific CD8
+
T cells in cluster formation and protective immunity. To this end, we used
Plasmodium berghei
ANKA expressing ovalbumin as well as CD8
+
T cells from transgenic mice expressing a T cell receptor specific for ovalbumin (OT-I) and CD8
+
T cells specific for an unrelated antigen, respectively. While antigen-specific CD8
+
T cells were essential for cluster formation, both antigen-specific and nonspecific CD8
+
T cells joined the clusters. However, nonspecific CD8
+
T cells did not significantly contribute to protective immunity. In the livers of infected mice, specific CD8
+
T cells expressed high levels of CD25, compatible with a local, activated effector phenotype.
In vivo
imaging of the liver revealed that specific CD8
+
T cells interact with CD11c
+
cells around infected hepatocytes. The depletion of CD11c
+
cells virtually eliminated the clusters in the liver, leading to a significant decrease in protection. These experiments reveal an essential role of hepatic CD11c
+
dendritic cells and presumably macrophages in the formation of CD8
+
T cell clusters around
Plasmodium
-infected hepatocytes. Once cluster formation is triggered by parasite-specific CD8
+
T cells, specific and unrelated activated CD8
+
T cells join the clusters in a chemokine- and dendritic cell-dependent manner. Nonspecific CD8
+
T cells seem to play a limited role in protective immunity against
Plasmodium
parasites.
Species Identification and Delineation of Pathogenic Mucorales by Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry
Authors: Shao Jin , Wan Zhe , Li Ruoyu , Yu Jin 
Published: February 2018

ABSTRACT

This study aimed to validate the effectiveness of matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS)-based identification of filamentous fungi of the order Mucorales. A total of 111 isolates covering six genera preserved at the Research Center for Medical Mycology of Peking University were selected for MALDI-TOF MS analysis. We emphasized the study of 23 strains of
Mucor irregularis
predominantly isolated from patients in China. We first used the Bruker Filamentous Fungi library (v1.0) to identify all 111 isolates. To increase the identification rate, we created a compensatory in-house database, the Beijing Medical University (BMU) database, using 13 reference strains covering 6 species, including
M. irregularis
,
Mucor hiemalis
,
Mucor racemosus
,
Cunninghamella bertholletiae
,
Cunninghamella phaeospora
, and
Cunninghamella echinulata
. All 111 isolates were then identified by MALDI-TOF MS using a combination of the Bruker library and BMU database. MALDI-TOF MS identified 55 (49.5%) and 74 (66.7%) isolates at the species and genus levels, respectively, using the Bruker Filamentous Fungi library v1.0 alone. A combination of the Bruker library and BMU database allowed MALDI-TOF MS to identify 90 (81.1%) and 111 (100%) isolates at the species and genus levels, respectively, with a significantly increased accuracy rate. MALDI-TOF MS poorly identified Mucorales when the Bruker library was used alone due to its lack of some fungal species. In contrast, this technique perfectly identified
M. irregularis
after main spectrum profiles (MSPs) of relevant reference strains were added to the Bruker library. With an expanded Bruker library, MALDI-TOF MS is an effective tool for the identification of pathogenic Mucorales.
Clinicoserological factors associated with response to steroid treatment and recurrence in patients with IgG4-related ophthalmic disease
Authors: Hong Ji Wook , Kang Sunah , Song Min Kyung , Ahn Chan Joo , Sa Ho-Seok 
Published: February 2018

PurposeTo investigate the factors associated with response to steroid treatment and recurrence in patients with IgG4-related ophthalmic disease (ROD).MethodsTwenty-eight patients with biopsy-proven IgG4-ROD treated between March 2010 and January 2017 were included in this retrospective study. Clinical features, serum IgG4 levels, systemic involvement, treatments and treatment outcome, factors associated with response to treatment and recurrence were assessed.ResultThirteen men and 15 women (mean age 50.8 years) were evaluated over mean follow-up period of 27.3 months. Elevated serum IgG4 levels (>1.35 g/L) and systemic disease were noted in 9 (32%) and 18 patients (64%), respectively. The lacrimal gland was involved in all patients, and 22 patients (78.6%) had bilateral involvement. Most patients (82%) responded well to systemic steroids, but 12 (43%) relapsed after the initial steroid treatment, requiring additional therapies to achieve remission. Complete response to initial steroid treatment was associated with elevated serum IgG4 levels before treatment (P=0.001) and bilateral orbital involvement (P=0.050). Recurrence was associated with elevated serum IgG4 levels before treatment (P=0.007), lower dose (P=0.057) and shorter duration of initial steroids (P=0.042). Patients with recurrence eventually required significantly more steroids than those without recurrence (P=0.011).ConclusionsPatients with IgG4-ROD responded well to systemic steroid treatment, but recurrence was common, particularly among those with elevated serum IgG4 levels and shorter duration of initial steroid treatment. Low-dose maintenance treatment with systemic steroids should be considered to avoid recurrence in patients with elevated serum IgG4 levels.
Detailed systematic analysis of recruitment strategies in randomised controlled trials in patients with an unscheduled admission to hospital
Authors: Rowlands Ceri , Rooshenas Leila , Fairhurst Katherine , Rees Jonathan , Gamble Carrol , Blazeby Jane M 
Published: February 2018

ObjectivesTo examine the design and findings of recruitment studies in randomised controlled trials (RCTs) involving patients with an unscheduled hospital admission (UHA), to consider how to optimise recruitment in future RCTs of this nature.DesignStudies within the ORRCA database (Online Resource for Recruitment Research in Clinical TriAls;www.orrca.org.uk) that reported on recruitment to RCTs involving UHAs in patients >18 years were included. Extracted data included trial clinical details, and the rationale and main findings of the recruitment study.ResultsOf 3114 articles populating ORRCA, 39 recruitment studies were eligible, focusing on 68 real and 13 hypothetical host RCTs. Four studies were prospectively planned investigations of recruitment interventions, one of which was a nested RCT. Most recruitment papers were reports of recruitment experiences from one or more ‘real’ RCTs (n=24) or studies using hypothetical RCTs (n=11). Rationales for conducting recruitment studies included limited time for informed consent (IC) and patients being too unwell to provide IC. Methods to optimise recruitment included providing patients with trial information in the prehospital setting, technology to allow recruiters to cover multiple sites, screening logs to uncover recruitment barriers, and verbal rather than written information and consent.ConclusionThere is a paucity of high-quality research into recruitment in RCTs involving UHAs with only one nested randomised study evaluating a recruitment intervention. Among the remaining studies, methods to optimise recruitment focused on how to improve information provision in the prehospital setting and use of screening logs. Future research in this setting should focus on the prospective evaluation of the well-developed interventions to optimise recruitment.