bluuebunny/crossref_metadata_2025 huggingface dataset:
Do Women Find the Progesterone Vaginal Ring Acceptable? Findings from Kenya, Nigeria, and Senegal
Authors: RamaRao Saumya , Obare Francis , Ishaku Salisu , Mané Babacar , Clark Heather , Liambila Wilson , Unumeri Godwin , Birungi Harriet , Diop Nafissatou , Rajamani Deepa , Townsend John
Published: February 2018

The progesterone vaginal ring (PVR) is a contraceptive designed for use by breastfeeding women in the first year postpartum. This Report presents results of an acceptability study of the PVR in Kenya, Nigeria, and Senegal. Women seeking postpartum family planning services were offered various contraceptive options including the PVR. Of the 174 participating women, 110 (63 percent) used one ring and 94 (54 percent) completed the study by using two rings over a six‐month period. Women were interviewed up to three times: at the time they entered the study, at 3 months (the end of the first ring cycle), and at 6 months (the end of the second ring cycle or when they exited if they had discontinued earlier). Many participants found the ring to be acceptable, with over three‐quarters reporting that it was easy to insert, remove, and reinsert. While a small proportion of women experienced ring expulsion, the majority did not. These findings suggest that even in countries with little or no use of vaginal health products, contraceptive vaginal rings offer women a new option that they are able and willing to use.
Frequency and causes of deferral amongst voluntary non‐remunerated blood donors from Pakistan – a single‐centre study
Authors: Jamal S. , Shaikh I. , Sohail S. , Ata U. , Ali A. , Saleem S.
Published: February 2018

Background

Amidst a system dependent on replacement donors in Pakistan, The Indus Hospital Blood Centre predominantly recruits voluntary non‐remunerated blood donors (VNRBD) to ensure provision of safe blood. Furthermore, due to unsafe practices of reuse of syringes in Pakistan, an additional criterion was added, deferring donors on recent history of therapeutic injections for medicinal purposes.

Methods

During the study period of 37 months (Dec 2013–Dec 2016), all potential donors visiting blood drives and the donor centre underwent a screening process via a brief physical examination and an interview. Donors were either accepted for donation, temporarily deferred or permanently deferred.

Results

In the study period, 63 582 potential donors visited, whereas 84% were VNRBD and 16% replacement donors. With an overall deferral of 24%, amidst VNRBD and replacement, the deferral rate was 25% and 18%, respectively. The major reasons for deferral were use of therapeutic injections followed by low haemoglobin. Furthermore, 54% of females and 21% of males visiting were deferred. Replacement donors, males and donors from underprivileged residential areas and factories had a comparatively higher proportion of deferral due to use of therapeutic injections.

Conclusion

The high deferral rate in this study is illustrative of the increased use of therapeutic injections amongst the Pakistani population. Additionally, due to the compulsion of providing blood donors associated with replacement donation, they are more likely to hide health conditions, hence the lower comparative deferral rate. The Pakistani population needs to be educated regarding the high risks associated with injections and replacement donors.
Contrast‐enhanced ultrasound complements two‐dimensional ultrasonography in diagnosing gallbladder diseases in dogs
Authors: Bargellini Paolo , Orlandi Riccardo , Paloni Chiara , Rubini Giuseppe , Fonti Paolo , Righi Cecilia , Peterson Mark E. , Rishniw Mark , Boiti Cristiano
Published: February 2018

Gall‐bladder diseases are common in dogs and two‐dimensional ultrasonography is a current standard method for diagnosis and treatment planning. However, findings from this modality can be nonspecific. The aim of this retrospective, case series study was to describe conventional and contrast‐enhanced ultrasound (using SonoVue®) findings in a group of dogs with histologically confirmed gall bladder disease. A total of 65 dogs were included. Branchlike, heterogeneous, and homogeneous contrast enhancement of echogenic intraluminal mass‐forming lesions was a contrast‐enhanced ultrasound characteristic of polypoid lesions due to cystic mucosal hyperplasia of the gallbladder and/or tumor, which had different wash‐in and washout characteristics. In dogs with mobile or immobile biliary sludge or mucocele, the echogenic intraluminal masses remained unenhanced. A double rim mark or enhancement defect in the gallbladder wall was a characteristic of edema or necrosis/rupture of the wall, respectively. Conventional ultrasonography correctly identified biliary sludge or mucocele in 36/37 dogs, cholecystitis/edema in 44/47 dogs, necrosis/rupture in 19/25 dogs, and gallbladder neoplasia in three of three dogs with these pathologies. It falsely identified biliary sludge or mucocele in eight of 28 dogs, cholecystitis/edema in three of 15 dogs, necrosis/rupture in 13/37 dogs, and gall‐bladder neoplasia in 20/59 dogs that did not have these pathologies. Contrast‐enhanced ultrasound correctly identified cholecystitis/edema in 42/47 dogs, but falsely identified cholecystitis/edema in three of 18 dogs. It correctly identified necrosis/rupture, benign polypoid lesions, and gallbladder neoplasia in all dogs with no false‐positive results. Findings supported contrast‐enhanced ultrasound as a complement to conventional ultrasonography for dogs with suspected gallbladder pathologies such as edema, necrosis, and rupture.
Effects of drought on weed emergence and growth vary with the seed burial depth and presence of a cover crop
Authors: Cordeau Stéphane , Wayman Sandra , Reibel Carole , Strbik Florence , Chauvel Bruno , Guillemin Jean‐Philippe
Published: February 2018

In conservation agriculture, weed seed germination could decrease with the presence of a cover crop, surface weed seed location and temporal drought in summer just after seed shedding. This study simultaneously examined the effects of a cover crop, burial depth (seed location) and hydric stress on weed emergence and early growth. It was hypothesized that drought would reduce weed emergence and the initial growth of weed seeds and that this effect would be greater when the seeds were on the soil surface and in the presence of a cover crop. Four annual weed species were chosen that are frequently found (Anisantha sterilis, Vulpia myuros, Sonchus asper, Veronica persica) and not frequently found (Alopecurus myosuroides, Poa annua, Cyanus segetum, Capsella bursa‐pastoris) in fields that implement conservation agriculture. The unburied seeds had 26% lower emergence, on average, than the buried seeds (significant for six of the eight species), hydric stress reduced emergence by 20% (for seven of the eight species) and the presence of a cover crop reduced the level of emergence by 17% (for all species). The unburied seeds with hydric stress were emerging under the “most stressful” set of factors, with a 45% decrease in emergence, compared with the seeds emerging under the “least stressful” set of factors (buried seeds without hydric stress). All the weed growth measurements (height, dry matter content and number of leaves) decreased with the presence of a cover crop. The species that are found frequently in the fields that implement conservation agriculture, compared with the species that are not frequently found in conservation agriculture fields, had higher rates of germination and a higher tolerance of hydric stress when their seeds were unburied.
Finite Time Passive Reliable Filtering for Fuzzy Systems With Missing Measurements
Authors: Vimal Kumar S. , Sakthivel R. , Sathishkumar M. , Marshal Anthoni S.
Published: February 2018

This paper investigates the problem of robust finite time extended passive reliable filtering for Takagi–Sugeno (T–S) fuzzy systems with randomly occurring uncertainties, missing measurements, and time-varying delays. Moreover, two stochastic variables satisfying the Bernoulli random distribution are introduced to characterize the phenomenon of the randomly occurring uncertainties and missing measurements. By skillfully choosing a proper Lyapunov–Krasovskii functional (LKF), a new set of sufficient conditions in terms of linear matrix inequalities (LMI) is derived to ensure that the filtering error system is robustly stochastically finite time bounded (SFTB) with a desired extended passive performance index. Based on the obtained sufficient conditions, an explicit expression for the desired filter can be computed. Finally, two numerical examples are provided to show the effectiveness of the proposed filter design technique.
Automated Coordinate Measuring Machine Inspection Planning Knowledge Capture and Formalization
Authors: Anagnostakis Dimitrios , Ritchie James , Lim Theodore , Sung Raymond , Dewar Richard
Published: February 2018

Capturing the strategy followed during a coordinate measuring machine (CMM) inspection planning session has been an extremely challenging issue due to the time-consuming nature of traditional methods, such as interviewing experts and technical documents data mining. This paper presents a methodology demonstrating how a motion capture-based system can facilitate direct and nonintrusive CMM operator logging for capturing planning strategies and representing in knowledge formats. With the use of recorded motion data, embedded knowledge and expertise can be captured automatically and formalized in various formats such as motion trajectory graphs, inspection plans, integrated definition (IDEF) model diagrams, and other representations. Additionally, a part program can be generated for driving a CMM to execute component measurement. The system's outputs can be used to help understand how a CMM inspection strategy is planned, as well as training aids for inexperienced operators and the rapid generation of part programs.
Multifault Diagnosis of Induction Motor at Intermediate Operating Conditions Using Wavelet Packet Transform and Support Vector Machine
Authors: Gangsar Purushottam , Tiwari Rajiv
Published: February 2018

This paper proposes advancement in the fault diagnosis of induction motors (IMs) based on the wavelet packet transform (WPT) and the support vector machine (SVM). The aim of this work is to develop and perform the fault diagnosis of IMs at intermediate operating conditions (i.e., the speed and the load) to take care of situations where the data are limited or difficult to obtain at required speeds and loads. In order to check the capability of proposed fault diagnosis, ten different IM fault (mechanical and electrical) conditions are considered simultaneously. In order to obtain the useful information from raw time series data that can characterize each of the fault classes at various operating conditions, the wavelet packet is applied to decompose the data of vibration and current signals from the experimental test rig. Fault features are then obtained using the decomposed data and further used for the diagnosis. In this work, five different wavelet functions (i.e., the Haar, Daubechies, Symlet, Coiflet, and Discrete Meyer) are considered in order to analyze the impact of different wavelets on the IM fault diagnosis. The proposed fault diagnosis has been initially attempted for the same speed and load cases and then extended innovatively to the intermediate speed and load cases. In order to check the robustness of the proposed methodology, the diagnosis is performed for a wide range of motor operating conditions. The results show the feasibility of the proposed fault diagnosis for the successful detection and isolation of various faults of IM, even with limited data or information at some motor operating conditions.
Design of a Tri-Axial Force Measurement Transducer for Plantar Force Measurements
Authors: Li Weizi , Dugnani Roberto
Published: February 2018

Transducers for spatial plantar force measurements have numerous applications in biomechanics, rehabilitation medicine, and gait analysis. In this work, the design of a novel, tri-axial transducer for plantar force measurements was presented. The proposed design could resolve both the normal and the shear forces applied at the foot's sole. The novelty of the design consisted in using a rotating bump to translate the external loads into axial compressive forces which could be measured effectively by conventional pressure sensors. For the prototype presented, multilayer polydimethylsiloxane (PDMS) thin-film capacitive stacks were manufactured and used as sensing units, although in principle the design could be extended to various types of sensors. A quasi-static analytic solution to describe the behavior of the transducer was also derived and used to optimize the design. To characterize the performance of the transducer, a 3 cm diameter, 1 cm tall prototype was manufactured and tested under various combination of shear and normal loading scenarios. The tests confirmed the ability of the transducer to generate strong capacitive signals and measure both the magnitude and direction of the normal and shear loads in the dynamic range of interest.
LesionAir: An Automated, Low-Cost Vision-Based Skin Cancer Diagnostic Tool
Authors: Wortman Tyler D. , Carlson Jay D. , Perez Edward , Slocum Alexander H.
Published: February 2018

Current techniques for diagnosing skin cancer lack specificity and sensitivity, resulting in unnecessary biopsies and missed diagnoses. Automating tissue palpation and morphology quantification will result in a repeatable, objective process. LesionAir is a low-cost skin cancer diagnostic tool that measures the full-field compliance of tissue by applying a vacuum force and measuring the precise deflection using structured light three-dimensional (3D) reconstruction. The technology was tested in a benchtop setting on phantom skin and in a small clinical study. LesionAir has been shown to measure deflection with a 0.085 mm root-mean-square (RMS) error and measured the stiffness of phantom tissue to within 20% of finite element analysis (FEA) predictions. After biopsy and analysis, a dermatopathologist confirmed the diagnosis of skin cancer in tissue that LesionAir identified as noticeably stiffer and the regions of this stiffer tissue aligned with the bounds of the lesion. A longitudinal, full-scale study is required to determine the clinical efficacy of the device. This technology shows initial promise as a low-cost tool that could rapidly identify and diagnose skin cancer.
An Improved Streamline Curvature Method for Centrifugal Compressor Performance
Authors: Chao-wei Zhang , Xue-zhi Dong , Xi-yang Liu , Qing Gao , Chun-qing Tan
Published: February 2018

This paper describes an improved throughflow calculation method on S2m based on streamline curvature method for predicting the performance of centrifugal compressor. A general method of specifying the empirical data provides separate treatment of blockage, deviation and losses. The spanwise and streamwise distribution laws of losses are described. The paper describes a new aspect of method about the mixing loss. Two-zone model considering the “jet and wake” can obtain the secondary flow width. For this reason, the improved prediction method combined with two-zone model is proposed to correct the mixing loss. Due to the average static pressure at outlet unknown, the secondary flow width is obtained by iterations.

This performance prediction method is validated with experimental and CFD data of three cases, including impeller(A), impeller(B) and impeller(C). The results show that the improved throughflow calculation method predicts the performance of centrifugal compressor more accurately than conventional throughflow calculation, with increased the accuracy of total pressure ratio and isentropic efficiency by about 3.18% and 1.30%.
Development of Turbine Blade Profiles Using Iterative Inverse Design Methodology
Authors: Rajendran Nanthini , Prasad Bhamidi , Sanyasiraju Y. V. S. S.
Published: February 2018

An iterative inverse design methodology is used to design gas turbine blades for the prescribed flow conditions. The input flow parameter considered here is the pressure distribution along the suction and pressure surfaces of the blade. The flow is regarded as inviscid. A guess blade is presumed and the flow analysis over the blade is determined using the existing commercial software. In case of mismatch of the flow parameters, the guessed profile surface is considered as a permeable membrane and the normal velocity on the blade surface is computed by conservation of momentum flux approach. The computed normal velocity is used to revise the blade geometry by mass conservation principle till the flow parameters converge. A few geometric constraints are enforced on the model to avoid quixotic blade model. The validation of the above method is being done using NACA profiles. The robustness of the method is verified by using various combinations of NACA blade profiles, where different initial guessed profiles are taken for the same prescribed pressure distribution.

This approach can be extended to three dimensional cases. To incorporate the complications attached with the three dimensional flows, three two dimensional sections can be considered on the blade geometry namely at hub, mid span and tip.
Impact of Inlet Fogging on the Performance of Steam Injected Cooled Gas Turbine Based Combined Cycle Power Plant
Authors: Shukla Anoop Kumar , Singh Onkar
Published: February 2018

Gas/steam combined cycle power plants are extensively used for power generation across the world. Today’s power plant operators are persistently requesting enhancement in performance. As a result, the rigour of thermodynamic design and optimization has grown tremendously. To enhance the gas turbine thermal efficiency and specific power output, the research and development work has centered on improving firing temperature, cycle pressure ratio, adopting improved component design, cooling and combustion technologies, and advanced materials and employing integrated system (e.g. combined cycles, intercooling, recuperation, reheat, chemical recuperation). In this paper a study is conducted for combining three systems namely inlet fogging, steam injection in combustor, and film cooling of gas turbine blade for performance enhancement of gas/steam combined cycle power plant. The evaluation of the integrated effect of inlet fogging, steam injection and film cooling on the gas turbine cycle performance is undertaken here. Study involves thermodynamic modeling of gas/steam combined cycle system based on the first law of thermodynamics. The results obtained based on modeling have been presented and analyzed through graphical depiction of variations in efficiency, specific work output, cycle pressure ratio, inlet air temperature & density variation, turbine inlet temperature, specific fuel consumption etc.
Energy and Exergy Investigations Upon Tri-Generation Based Combined Cooling, Heating, and Power (CCHP) System for Community Applications
Authors: Sharma Meeta , Singh Onkar
Published: February 2018

The continually increasing demand for electricity, cooling and heating accompanied by depleting energy sources, makes it inevitable to use the technologies to harness the available resources to their maximum capacity. The tri-generation systems are the advanced and popular technological option for efficient, reliable, flexible, and less polluting alternatives to utilize the conventional energy resources in an optimal way. In this work, the energy available with conventional fuel is utilized along with solar energy collected through parabolic trough collectors which are integrated with steam injected gas turbine cycle for combined power, heating and cooling requirements. Here a thermodynamic model has been developed for the considered tri-generation combined cooling, heating, and power (CCHP) system and the detailed energy and exergy analysis is performed. The results obtained, by the thermodynamic modeling and analyses of CCHP system based on the first and second law of thermodynamics have been presented and conclusions are drawn from their analysis. This work provides the energy efficient solution for combined heating, cooling, and power for medium load in community usage which may require plant size in the range of 10–50 MW. However, the cost effectiveness depends on the relative cost of gas turbine fuel with respect to other alternate systems with alternate fuels.
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.
Oxidation Coatings on Additively Manufactured CoCrMo
Authors: Somanatha Panicker Sujith , Srinivasan Dheepa
Published: February 2018

Additive manufacturing (AM) via the direct metal laser sintering (DMLS) route is a new technology for both new make and repair application in gas turbine hot gas path components. This paper presents the development of a new oxidation coating Ceral 10 as a protective coating on the AM CoCrMo alloys. A high Al activity slurry aluminide coating (Ceral 10) was deposited on the DMLS CoCrMo. The coating produced on DMLS CoCrMo was uniform and intact having a thickness of ∼ 80–100 μm. The slurry aluminide coating showed an Inward diffusion with the DMLS CoCrMo substrate having an Al of 38–40 wt% and Si (12–13 wt%) after the diffusion heat treatment. The interface with the substrate was gradual in terms of chemistry with an interdiffusion zone of 15–20 μm. The Ceral10 coating showed limited oxidation up to 1038°C (1000 h) and at 1066°C (after 500 h), coating spallation occurred. The distinct thermally grown oxide between the coating-substrate interface led to the spallation. The effectiveness of the Ceral 10 coating to protect the DMLS CoCrMo alloy at high temperatures is evaluated via detailed microstructural characterization.
Study of Process Parameter and Powder Variability on the Properties and Recrystallization Behavior of Direct Metal Laser Sintered CoCrMo
Authors: Chandrasekara Santhosh Kumar Rao , Sudarshan Reddy Anigani , Srinivasan Dheepa , Ananthanarayanan Durga
Published: February 2018

Additive manufacturing via the direct metal laser sintering (DMLS) route is an attractive technology for repair and refurbishment of gas turbine components. This paper presents the study of the role of various process parameters such as laser power, scan speed, layer thickness and powder variability in obtaining dense, pore-free parts of CoCrMo using the DMLS route. The variation in surface roughness of the built samples and the effect of powder variability on the part density were brought out via a systematic design of experiments (DOE). Different solution heat treatments were carried out to establish the recrystallization behavior of DMLS CoCrMo. The variation in microstructure and properties were evaluated between powders from two different sources, EOS and Praxair, as an important aspect towards practical applicability of the process for components.
Numerical Analysis of Jet Impingement Cooling Using Converging Conical Hole for Blade Leading Edge
Authors: Sivamani Seralathan , Ram Chaina , Thomai Micha Premkumar , Venkatesan Hariram
Published: February 2018

The objective of this present work is to investigate numerically the effect of converging conical hole on blade cooling at leading edge. Diameter ratio of the converging conical holes is maintained as two with a converging angle of 20°. Cylindrical geometry used by Lee et al. [5] for the experimental investigation is taken as base reference for this present numerical investigation. Turbulence model study is carried out with three different models and kω-SST is found to give closer result with the experimental data. Subsequent investigations are carried out using kω-SST turbulence model. The target surface for the present study is 19.05 cm in radius and the diameter of the impingement hole is 1.30 cm, 2.15 cm 3.40 cm. The jet hole to the target surface spacing is varied as R/4, R/2 and 3R/4. The steady-state Reynolds Averaged Navier Stokes equations are solved for different impingement hole diameters at Reynolds number of 11000, 23000 and 50000. The target surface is maintained at constant heat flux of 10000 W/m2. Numerically computed Nusselt number and temperature distribution for the convergent conical hole and cylindrical hole are compared. Around 186% increase in Nu and 13% decrease in surface temperature is observed at the stagnation point for the optimum case in this present study i.e, jet spacing R/2, converging conical hole diameter 2.15 cm and Re 23000. The converging conical hole configuration increases the fluid velocity in the potential core region and enhances the heat transfer. It is followed by 185% increase in Nu and 15.58% reduction in target surface temperature for Re 11000 and 170% increase in Nu and 7.28% reduction in temperature for Re 50000.
Adjoint Optimisation of Internal Turbine Cooling Channel Using NURBS-Based Automatic and Adaptive Parametrisation Method
Authors: Jesudasan Rejish , Zhang Xingchen , Mueller Jens-Dominik
Published: February 2018

A well-formulated design space parametrisation is the key to the success of design optimisation. Most parametrisation methods require manual set-up which typically results in a restricted design space and impedes the generation of superior designs which may be found outside this restricted envelope. In this work, we adopt a NURBS-based automatic and adaptive parametrisation approach where the optimisation begins in a coarser design space and adapts to finer parametrisation during the optimisation. Our approach takes CAD descriptions as input and to alter the shape perturbs the control points of the NURBS patches that form the boundary representation. Driven by adjoint sensitivity information the control net is adaptively enriched using knot insertion. The sensitivity-driven parametrisation method is applied here to reduce the pressure loss of a U-bend passage of a turbine blade serpentine cooling channel.
Structural Design and Analysis of Cylindrical Squirrel Cage to Meet Stiffness, Strength and High Cycle Fatigue Life for an Aero Engine
Authors: Kandhaswamy Srinivasan Senthil Kumar , Periarowthar Nazar
Published: February 2018

Squeeze film dampers have traditionally been used in aircraft engine to overcome stability and vibration problems that are not adequately handled with conventional style bearings. One of the key design features in a squeeze film damper [1] configuration is the introduction of flexibility in the bearing support. The simplest means to provide the support flexibility in the squeeze film damper is through the use of squirrel cage [2]. This paper deals with structural design analysis of cylindrical squirrel cage of an aircraft engine. Design of the squirrel cage needs a balance between stiffness and strength requirements. To meet the strength, stiffness and fatigue life requirements, squirrel cage web dimensions and fillet radius are modified. The various configurations of the squirrel cage have been evaluated to arrive at the optimum design. Stress analysis of the bearing has been carried out for axial, radial unbalance loads. Stress distribution in the web region has been studied in detail. High cycle fatigue life margins are estimated using Goodman diagram. The squirrel cage web dimensions and fillet radius are modified to improve HCF life requirements. The operating stresses in the squirrel cage are reduced while meeting the stiffness and HCF life requirements of the component.
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.
Comparative Studies on the Dynamic Performances of High Speed Turbocharger Rotor Supported on Oil-Free Bearings Versus Conventional Floating Ring Systems
Authors: Mutra Rajasekhara Reddy , Srinivas J.
Published: February 2018

Present work focuses on the dynamic modelling of the dual-disc rotor supported on oil-free bearings idealizing a turbocharger rotor bearing system. The equations of motion of the rotor system are formulated and solved by finite element method to obtain the dynamic response of the system. The gas-foil bearing forces obtained from finite-difference approach at each time-step of solution. The same rotor model is used with the conventional floating ring bearing system where, the bearing forces are provided as displacement dependent time-varying oil and floating ring forces. As a practical environmental condition, the effect of temperature on the viscosity is studied using Dowson equation. The dynamic responses are illustrated both for rotor supported on both gas-foil and floating-ring type bearings. The effects of changes in bearing clearances on the overall dynamic characteristics of the rotor are reported. In order to utilize the gas foil bearing model, an identification study is performed to predict the operating clearance and air viscosity using dynamic response data.
Experimental and Numerical Investigation of Operating Range Enhancement Techniques in Centrifugal Compressor for Turbochargers
Authors: Kumar Chandramohan Kishore , Purushothaman Kirubakaran , Pandurangi Vidyadheesh , Prasad Deshkulkarni Kishore
Published: February 2018

High speed centrifugal compressors are used in turbochargers and in small gas turbine engines that typically power cruise missiles, helicopters and auxiliary power units (APU). Centrifugal compressors have wider operating range compared to axial compressor and are compact. Though centrifugal compressors having a pressure ratio of the order of 12:1 per stage have been demonstrated with reasonably good isentropic efficiencies, achieving a wider operating range has always been a challenge. A Turbocharger that needs to be designed to function both at sea-level and 5 km altitude conditions, requires a wider compressor map to accommodate the diesel engine operating line. A wider compressor map can be achieved by various techniques. The approaches used in the present study include providing pinch in the diffuser entry region and ported shroud arrangement in the compressor casing. A parametric study has been carried out by varying geometric parameters and an appropriate configuration that offers lower total pressure loss and better diffuser pressure recovery is chosen. The flow mechanisms responsible for better performance is investigated numerically for various configurations with diffuser pinch. To further enhance the operating range, a ported shroud configuration in the compressor housing is designed and analysed with the finalized diffuser pinch. Results of computational analysis for different ported shroud slot geometries have been studied numerically and are presented. Two configurations have been tested in a turbo-drive based test rig. The first configuration is only with diffuser pinch and the second configuration is with diffuser pinch and ported shroud. The extent of map width enhancement obtained by each technique is presented and compared with numerical analysis. The test results show good match with the predicted trend and confirms that diffuser pinch and ported shroud configurations offer significant enhancement in achieving a wider operating range. The flow mechanisms responsible are discussed in detail in the paper.
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.
Aeroelastic Flutter Analysis of Linear Cascade Blades: STC5
Authors: Purushothaman Kirubakaran , Jeyaraman Sankar Kumar , Parida Sasikanta , Prasad Deshkulkarni Kishore
Published: February 2018

Study of aerodynamic flow and aeroelastic stability in vibrating blades of cascade is the main objective of this study. Standard test configuration (STC-5) was chosen for this study as it involves transonic flow regime in compressor blade cascades. CFD analysis were carried out for 11 test cases of STC-5 configuration and pressure coefficient values were compared with test data. The range of incidence angles vary from 2° to 10° and reduced frequency varies from 0.14 to 1.02. Inflow Mach number was fixed at 0.5 and Reynolds number was fixed at 1.4 × 106. Analysis of vibrating blades and comparison of test data results of axial compressor with linear cascade stator blades of fifth standard configuration at high subsonic speed is compared with CFD results. While doing this vibration of only the center blade is concerned when all the other blades in the cascade are fixed. Fluid structure interaction approach is used here to evaluate the unsteady aerodynamic force and work done for a vibrating blade in CFD domain. Energy method and work per cycle approach is adapted for aerodynamic damping prediction. A framework has been developed to estimate the work per cycle and aerodynamic damping ratio. Final sensitivity study was carried out to evaluate the influence of blade incidence and frequency on blade damping values.
Parametric Study on Laser Additive Manufacturing and Subsequent Post Processing of Inconel 718 Thin Walled Structures
Authors: Jinoop Arackal Narayanan , Paul Christ Prakash , Bindra Kushvinder Singh
Published: February 2018

Laser Additive Manufacturing (LAM) is one of the greener routes for fabrication of Inconel 718 (IN718) components. In the present work, Taguchi L9 array based optimization is performed using grey relational analysis to optimize the process parameters for the fabrication of thin walled structures using a 2 kW fibre laser based additive manufacturing system. Within the framework of the experimental conditions of the study, the LAM processing parameters, i.e., laser power, scan speed and powder feed rate, are optimized for minimum width and maximum height. The optimized parameters are used for the deposition of multi-layered walls and it is subjected to heat treatment at 1000 °C for duration of one-hour, followed by water quenching. Comprehensive investigations on microstructural and mechanical behaviour using optical microscopy (OM), X-ray diffraction (XRD) analysis, micro-hardness and automated ball indentation (ABI) are carried out. Microstructure examinations of LAM deposits of IN718 reveal intermixed dendritic and cellular structures. However, homogenization in microstructure is observed through heat treatment resulting in reduced micro-hardness. It is also observed that there is considerable increase in the crystallite size of the deposits after heat treatment. This study opens a new route for fabrication of thin walled structures using LAM with modified properties by erasing the thermal history through heat treatment.
Experimental Study of Unsteady Pressure Fluctuations due to Tip Leakage Flows in an Axial Flow Turbine
Authors: Senthil Kumaran R. , Kumar Kishor , Poornima N.
Published: February 2018

The tip leakage flow which is characterized by the blade tip vortex is a highly complex and unsteady phenomenon. It is of great interest to understand the unsteady pressure characteristics of tip leakage flow. The present study aims to focus on the unsteady pressure behavior caused by tip leakage flow of a single stage axial flow turbine. A series of experiments were carried out with a scaled up high work axial flow turbine in a Large Scale Rotating Rig to understand this unsteady pressure behavior. The pressure fluctuations were mapped at five axial locations on the casing across the rotor tip. Unsteady pressures were measured using calibrated fast response transducers. Measurements were phase-locked with the rotor. The pressure data was ensemble averaged and represented gross unsteadiness in the flow. Experiments were carried out over a range of flow coefficients (Cx/U) like 0.30, 0.32, 0.34 and 0.36. The blade pass frequency was the predominant one seen during the measurements. Mild influence of vane exit wake turbulence was also seen during the measurements. Constant speed flow coefficient variation did not seem to cause additional unsteadiness to the tip leakage flow.
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.
Atomization Characteristics of Jatropha-Derived Alternative Aviation Fuels From Aircraft Engine Injector
Authors: Sakthikumar Ramachandran , Sivakumar Deivandren , Raghunandan B. N. , Hu John T. C.
Published: February 2018

Search for potential alternative jet fuels is intensified in recent years to meet stringent environmental regulations imposed to tackle degraded air quality caused by fossil fuel combustion. The present study describes atomization characteristics of blends of jatropha-derived biofuel with conventional aviation kerosene (Jet A-1) discharging into ambient atmospheric air from a dual-orifice atomizer used in aircraft engines. The biofuel blends are characterized in detail and meet current ASTM D7566 specifications. The experiments are conducted by discharging fuel spray into quiescent atmospheric air in a fuel spray booth to measure spray characteristics such as fuel discharge behavior, spray cone angle, drop size distribution and spray patternation at six different flow conditions. The characteristics of spray cone angle are obtained by capturing images of spray and the measurements of spray drop size distribution are obtained using laser diffraction particle analyzer (LDPA). A mechanical patternator system comprising 144 measurement cells is used to deduce spray patternation at different location from the injector exit. A systematic comparison on the atomization characteristics between the sprays of biofuel blends and the 100% Jet A-1 is presented. The measured spray characteristics of jatropha-derived alternative jet fuels follow the trends obtained for Jet A-1 sprays satisfactorily both in qualitative and quantitative terms.