bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel Lead Garment Structural System to Alleviate Orthopedic Stress for Surgeons
Authors: Johnson Hilary , Miller Sally , Tawde Prianca , LaPenta Bethany , Teo Daniel , Cervantes Thomas , Mehta Nishaki , Slocum Alexander
Published: July 2018

Cardiovascular, orthopedic, and interventional radiology procedures using fluoroscopy require healthcare professionals to wear heavy lead garments for radiation protection, sometimes for up to 12 hours per day. Wearing lead garments for prolonged periods of time can lead to musculoskeletal injuries, discomfort, and fatigue. MobiLead is a mobile lead garment frame that was developed to reduce the weight supported by the user in an effort to mitigate these problems. The MobiLead system moves the lower garment load off the user’s body to a structural ground-supported frame and redistributes the upper load from the shoulders to the hips through a torso frame. The system is compact and maximizes the limited space available in operating rooms, while still giving the surgeon adequate mobility for various emergency procedures. Preliminary analysis of device effectiveness was conducted using electromyography and qualitative surgeon user feedback surveys. This paper will discuss the design, fabrication, and testing procedures for this mobile radiation protection system optimizing both support and mobility.
Design Proposal for a Portable Elbow Exoskeleton
Authors: Manna Soumya K. , Dubey Venketesh N.
Published: July 2018

Exoskeleton based rehabilitation for post-stroke recovery is being aggressively pursued due to unavailability of adequate number of caregivers and huge investment for the manual treatment [1]. The structural framework for providing different training exercises is not similar for all exoskeletons and there is no standardized protocol for rehabilitation following stroke [2]. Various approaches have been undertaken to come up with customized exoskeleton design for implementing a specific type of exercise. Though a few exoskeletons have proved to be beneficial in terms of clinical outcomes, there is still a long way to go before a useful rehabilitation device becomes acceptable to the users. After reviewing the 46 exoskeletons (commercial or prototypes) [3], two key requirements can be considered for the design of an exoskeleton; the structural parameter which decides the size, weight and the ease of control and the other is the nature of rehabilitation therapy which defines the type and intensity of the exercises performed during training.
Mechanical Performance of PLLA Stent
Authors: Wang Longzhen , Tong Junfei , Dong Pengfei , Wilson David L. , Bezerra Hiram G. , Gu Linxia
Published: July 2018

Stent implantation is widely used to treat blocked lumen. Stents were meshed structure made of polymers and metal alloys, including stainless steel, cobalt chrome and nitinol [1]. Clinical studies had demonstrated that stents helped to scaffold the diseased lesion up to one year when tissue adapted to the stented environment [2]. However, the permanently implanted stents inside artery were associated with complications such as stent fracture, tissue inflammation, in-stent restenosis and thrombosis [3]. Currently, biodegradable stents are attracting more attention due to its potential long-term efficacy in treating blocked lumens. The detailed characterizations of biodegradable stents are essential for the desired clinical outcomes.
Principles of Computer Numerical Control Applied to Small Research Animal Surgical Procedures
Authors: Rynes Matthew , Ghanbari Leila , Hu Jay Jia , Schulman Daniel Sousa , Johnson Gregory , Laroque Michael , Kodandaramaiah Suhasa B.
Published: July 2018

The tools and techniques available for systems neuroscientists for neural recording and stimulation during behavior have become plentiful in the last decade. The tools for implementing these techniques in vivo, however, have not advanced respectively. The use of these techniques requires the removal of sections of skull tissue without damaging the underlying tissue, which is a very delicate procedure requiring significant training. Automating a part of the tissue removal processes would potentially enable more precise procedures to be performed, and it could democratize these procedres for widespread adoption by neuroscience lab groups. Here, we describe the ‘Craniobot’, a microsurgery platform that combines automated skull surface profiling with a computer numerical controlled (CNC) milling machine to perform a variety of microsurgical procedures in mice. Surface profiling by the Craniobot has micrometer precision, and the surface profiling information can be used to perform milling operations with relatively quick, allowing high throughput. We have used the Craniobot to perform skull thinning, small to large craniotomies, as well as drilling pilot holes for anchoring cranial implants. The Craniobot is implemented using open source and customizable machining practices and can be built with of the shelf parts for under $1000.
Design Work of a Compressor Stage Through High-to-Low Speed Compressor Transformation
Authors: Zhang Chenkai , Hu Jun , Wang Zhiqiang , Gao Xiang
Published: July 2018

Low-speed model testing has advantages such as great accuracy, low cost and risk, so it’s widely used in the design procedure of HPC exit stage. The low-speed model testing project is conducted in Nanjing University of Aeronautics and Astronautics, to represent aerodynamic load and flow field structure of the seventh stage of a high-performance 10-stage high-pressure compressor. This paper outlines the design work of the low speed four-repeating-stage axial compressor, the third stage of which is the testing stage. The first two stages and the last stage provide the compressor with entrance and exit conditions respectively. The high-to-low speed transformation process involves both geometric and aerodynamic considerations. Accurate similarities demand the same Mach number and Reynolds number, which will not be maintained due to motor power/size and its low-speed feature. Compromises of constraints are obvious. Modeling principles are presented in high-to-low speed transformation. Design work is carried out based on these principles. Four main procedures are proceeded subsequently in the general design, including establishment of low-speed modeling target, global parameter design of modeling stage, throughflow aerodynamic design and blading design. In global parameter design procedure, rotational speed, shroud diameter, hub-tip ratio, mid-span chord and axial spacing between stages are determined by geometrical modeling principles. During throughflow design process, radial distributions of aerodynamic parameters such as D-Factor, pressure-rise coefficient, loss coefficients, stage reaction and other parameters are obtained by determined aerodynamic modeling principles. Finally, rotor and stator blade profiles of LSRC at seven span locations are adjusted, to make sure that blade surface pressure coefficients agree well with that of the HPC. 3D flow calculations are performed on low-speed four-stage axial compressor, and the resultant flow field structures agree well with that of the HPC. It’s worth noting that a large separation zone appears in both suction surfaces of LSRC and HPC. How to diminish it through 3D blading design in LSRC test rig is our further work.
Innovative Gas Turbine Engine Cycle Aerothermodynamical Analysis
Authors: Ezzuldeen Mustafa M.
Published: July 2018

The gas turbine engine design is fundamentally, taking the air flow into the compressing stage then combustion stage to add energy, and finally extracting energy in the turbine module. This journey of the flow in the engine is in serial connections. Posing the problem of the limiting turbine inlet temperature, the number that all the turbomachinery engineers desperately want to increase by tuning the inlet stages materials, or fine changes onto the blades’ profile or the flow paths. But the significant increase to this temperature lies under more fundamental and radical redesigns to the theory of the gas turbine operation, and its thermodynamical cycle. These principles were considered for long untouchable facts, and stayed lurking from the engineers examining eyes. This paper introduces one of these possibilities by genuine redesign concepts. Backed with CFD analysis, and Thermodynamical feasibility studies to address the potential problems of these modifications. The redesigns include implementing the new concept of the contra-rotating turbine more effectively to reduce the turbine module size, connecting pressurized fluid streams of two counter-rotating compressors in parallel instead of the serial connection, forming a protecting Pressurized shield for the entry turbine stages and, Extracting the energy in the process flow using flows interactions instead of flow-blades interactions.
Exit Blade Angle and Roughness Effect on Centrifugal Pump Performance
Authors: Bellary Sayed Ahmed Imran , Samad Abdus
Published: July 2018

Exit blade angle and impeller surface roughness has a significant effect on the performance of a centrifugal pump impeller handling different viscosity fluids. In this paper, a three-dimensional flow simulation using Reynolds averaged Navier Stokes (RANS) equations for the performance analysis of the impeller is reported. The analysis using water and viscous liquids has been accomplished for different flow conditions, exit blade angle and roughness values. Standard k-ε two equation model is used for the turbulent closure of steady incompressible flow. The investigation shows that the blade exit angle has influence on the head, shaft power and efficiency of the impeller for different liquids. Rise in head, increase in shaft power and decrease in hydraulic efficiency have been observed with increasing roughness.
A Design Environment for Performance Modeling and Analysis of Aero Engine Lubrication Systems
Authors: Mahendiran Prasath , Balasubramanian Bommaian , Manavalan Muralidhar , Rao Adithya
Published: July 2018

This paper presents the overview and capability of design Environment for performance modeling and analysis of aero engine lubrication systems. The design environment is implemented as an intuitive and easy to use toolbox implemented within the commercial off-the-shelf (COTS) simulation software environment MATLAB/Simulink®. The toolbox consists of a library of predefined reusable/generic lubrication system components like flow resistance elements, pumps and orifice. The component behavior is modeled mathematically using first principles and component characteristics. The developed components have been extensively verified & validated with actual hardware test data covering multiple test points in the flight envelope and also different failure modes of the system. The verification & validation methodology and the results of the component tests, is not the subject of the paper. The aero engine lubrication system is modeled by connecting the components drawn from the library to form a network consisting of nodes and flow paths. The solver implemented computes the unknown pressure and flow values in the lubrication circuit. The design environment has been used to perform steady state performance analysis of aero engine lubrication system. It has additional capability to perform parametric studies, trade studies, design exploration, analyzing simulation results and automated report generation, which will be described in the paper. The flexible software architecture and modular programming techniques has delivered the significant benefit of component models reuse. The generic nature of the toolbox can be exploited to perform system modeling and analysis of any hydraulic system.
Application of a High Order LES Approach to the Redistribution of Inlet Temperature Distortion in a Turbine
Authors: Biswas Debasish , Kitoh Aya
Published: July 2018

The demand of an increase in the cycle performance of today’s gas turbines creates severe heat loads in the first turbine stage, since higher operating temperatures are required. The mean flow temperature is usually well above the limit supported by the surrounding material. Cooling of both end-walls and the blades of the first stage is thus usually necessary. Consequently, mid-span streaks of hot gas pass through the first stator row and become hot jets of fluid. Also, the exit flow from a gas turbine combustor entering a turbine stage can have a wide variation in temperature. These variations may be both spatial and temporal. The implementation of cooling method requires a clear understanding of the aerodynamics involved. Both qualitative and quantitative assessments of the redistribution of inlet temperature distortions can be used to considerable advantage by the turbine designer. Experimentally it has been demonstrated that the rotor actually separates the hotter and cooler streams of fluid so that a hotter fluid migrates toward the pressure surface and cooler fluid migrates towards the suction surface. The main purpose of this study is to test the performance of a high-order LES model in terms of predicting this type of highly complicated unsteady flow and heat transfer phenomena. This work describes the performance of a high-order Large Eddy Simulation (LES) turbulent model (developed by the first author) related to the prediction of above mentioned redistribution of inlet temperature distortion in an experimental turbine. Because the understanding of the physical phenomena associated with this temperature redistribution behavior is a very challenging computational fluid dynamic problem. If the numerical method could predict the precisely measured data satisfactorily, then the fluid dynamic variables which are difficult to measure (but obtained as computed results) could be used to visualize the flow characteristics. This technique will also help to get rid off indirect measurement techniques with large measurement uncertainty. In our study emphasis is put to predict the unsteady turbulence characteristics. In this work 3-D unsteady Navier-Stokes analysis of a turbine stage (satisfying the experimental stator-rotor blade ratio) is carried out to study the above mentioned phenomena. The numerical results predicted the experimentally observed phenomena very well. The fact that the streamlines in the stator row remain unaffected was demonstrated by the numerical results. The measured characteristics of the streamline patterns in the rotor row resulted from the secondary flow effect and consequently the inlet temperature distortion effect is also very well predicted.
Experimental and Numerical Investigation of Effect of Blowing Ratio on Film Cooling Effectiveness and Heat Transfer Coefficient Over a Gas Turbine Blade Leading Edge Film Cooling Configurations
Authors: Giridhara Babu Yepuri , Lalgi Gururaj , Talanki Puttarangasetty Ashok Babu , Felix Jesuraj , V. Kenkere Sreenivas Rao , Vinod Kumar Nanjundaiah
Published: July 2018

Film cooling is one of the cooling techniques to cool the hot section components of a gas turbine engines. The gas turbine blade leading edges are the vital parts in the turbines as they are directly hit by the hot gases, hence the optimized cooling of gas turbine blade surfaces is essential. This study aims at investigating the film cooling effectiveness and heat transfer coefficient experimentally and numerically for the three different gas turbine blade leading edge models each having the one row of film cooling holes at 15, 30 and 45 degrees hole orientation angle respectively from stagnation line. Each row has the five holes with the hole diameter of 3mm, pitch of 20mm and has the hole inclination angle of 20deg. in spanwise direction. Experiments are carried out using the subsonic cascade tunnel facility of National Aerospace Laboratories, Bangalore at a nominal flow Reynolds number of 1,00,000 based on the leading edge diameter, varying the blowing ratios of 1.2, 1.50, 1.75 and 2.0. In addition, an attempt has been made for the film cooling effectiveness using CFD simulation, using k-€ realizable turbulence model to solve the flow field. Among the considered 15, 30 and 45 deg. models, both the cooling effectiveness and heat transfer coefficient shown the increase with the increase in hole orientation angle from stagnation line. The film cooling effectiveness increases with the increase in blowing ratio upto 1.5 for the 15 and 30 deg. models, whereas on the 45 deg. model the increase in effectiveness shown upto the blowing ratio of 1.75. The heat transfer coefficient values showed the increase with the increase in blowing ratio for all the considered three models. The CFD results in the form of temperature, velocity contours and film cooling effectiveness values have shown the meaningful results with the experimental values.
Unsteady Secondary Flow in an Annular Compressor Cascade
Authors: Hermle Georg , Lawerenz Martin
Published: July 2018

Subject of the experimental investigations presented is the analysis of secondary flow in an annular compressor cascade. Focus lies on the so-called rotating instability. The investigations concentrate on the unsteady pressure field in the area of the blade tip clearance in order to get deeper understanding of the phenomenon of rotating instability. Therefore, transducers were mounted along the leading edges around the circumference of the cascade. This arrangement allows the determination of the coherence and the phasing between the transducers by the cross correlation via Fourier and wavelet transform. The results show the influence of the Mach number and the incidence angle on the onset of the phenomenon. Furthermore, a relation between the characteristic frequencies of the rotating instability to certain modal types can be stated. Moreover, the wavelet cross power spectrum suggests that the phenomenon is not continuously present within the spectra but shows an unsteady appearance.
CFD Analysis to Understand the Flow Behaviour of a Single Stage Transonic Axial Flow Compressor
Authors: Shobhavathy M. T. , Hanoca Premakara
Published: July 2018

This paper comprises the Computational Fluid Dynamic (CFD) analysis to investigate the flow behaviour of a high speed single stage transonic axial flow compressor. Steady state analyses were carried out at design and part speed conditions to obtain the overall performance map using commercial CFD software ANSYS FLUENT. Radial distribution of flow parameters were obtained at 90% of design speed for the choked flow and near stall flow conditions. The predicted data were validated against available experimental results. The end wall flow fields were studied with the help of velocity vector plots and Mach number contours at peak efficiency and near stall flow conditions at 60% and 100% design speeds. This study exhibited the nature of a transonic compressor, having strong interaction between the rotor passage shock and the tip leakage vortex at design speed, which generates a region of high blockage in the rotor blade passage. The influence of this interaction extends around15% of the blade outer span at design speed and in the absence of blade passage shock at 60% design speed, the influence of tip leakage flow observed was around 8%.
Numerical Investigation of the Effect of Moving Endwall and Tip Clearance on the Losses in a Low Speed Axial Flow Compressor Cascade
Authors: Varpe Mahesh K. , Pradeep A. M.
Published: July 2018

This paper explores the effect of the tip-clearance in presence of the endwall motion, incident at 10°, on a rectilinear cascade of C4 blade. The width of the moving endwall considered here was 120% of an axial chord to represent the operating conditions close to that of an actual rotor in subsonic condition at peak load. The flow coefficient was varied from 0.3 to 0.6. The cascade was analysed computationally using ANSYS Fluent ©. The validation of numerical results of the cascade was done with the experimental result for no tip gap condition. The results agreed well with the experimental data. Detailed analysis of the numerical results was then carried out to explore the complex flow features, which was a consequence of the combined influence of the endwall effect, tip clearance and moving endwall. With no tip-gap, the endwall effects were substantial and extended up to 40%span of the blade and nearly 60% of the pitch whereas the flow coefficient does not alter the distribution along the span. The tip leakage flow counteracts the endwall flows and helps in minimizing them in the region towards the tip. The endwall motion does alter the pressure distribution at the blade tip but the relative variations in blade loading at the tip were not appreciable. Lower flow coefficient at 1% tip clearance gives the optimum pressure rise with reduced total pressure loss in the wake.
Development of a Novel Technique to Address Compressor Fouling in a Turbo-Shaft Engine
Authors: Kumar S. Saji , Muthu S. Esakki , Dileep S. , Mishra R. K.
Published: July 2018

Compressor washing is commonly used in gas turbine engines to retrieve engine power. Severity of fouling should be known to decide on mounted or uninstalled washing and also to optimize the time and money. The present study aims to develop a system for predicting and scheduling the washing process. One 1 MW turbo shaft engine has been taken as the model for this study. The deviations in performance parameters have been quantified based on test data over a period. Deterioration of engine health parameters namely efficiency and flow capability of compressor, gas generator turbine and power turbine are considered for analysis. Sensitivity analysis and ranking of the measurements were done using a correlative technique suggested by Stamatis. The interdependency and observability of the measurements were checked. The fault signatures of selected measurement set on component degradations were isolated and estimation charts were formed to predict the optimum time intervals for compressor washing. The study forms a base platform to apply techniques like artificial neural networks for the accurate forecasting of optimum cleaning intervals for turbo shaft engines.
CFD Simulation of Open-Cell Aluminum Metal Foams for Pressure Drop Characterization
Authors: Krishnanunni Abhay Girija , Sarasamma Jayakumar Janardhanan , Giridhara Babu Yepuri , Jesuraj Felix
Published: July 2018

Many researchers have done the CFD simulation of open-cell aluminum metal foams with a unit cell with periodic boundary conditions. However, this does not represent a real life situation, as the foam-fluid interactions cannot be properly modeled. In the present study the simulation is done for metal foam with the more number of foam cells to proximate the conditions close to the actual situations. The CFD simulation of open-cell aluminum metal foams was done using ANSYS FLUENT. The results are obtained by solving the Continuity, Momentum and Energy equations and standard k-ε turbulence model is used for simulation. The boundary conditions applied are same as those applied during the experiments conducted at Heat Transfer Lab, National Aerospace Laboratories, Bangalore. In this study the Aluminum Alloy (Al 6101-T6) metal foam of pore density 10 ppi is used for CFD analysis.
Performance Evaluation of Gear Pump by 2D Unsteady CFD Analysis
Authors: Kumar K. Anil , Balamuralikrishnan N.
Published: July 2018

Gas Turbine development activities have been associated with development of different pumps and its allied subsystems used for fuel supply and lubrication oil supply at different engine operating condition.

2D transient flow analysis of a Dual pump has been carried out in an environment with an adverse pressure gradient to map important parameters like pressure, velocity, mass flow and effect of slip. Three achievable close tolerances were selected and carried out the analysis. Finally identified tolerance to be maintained during manufacturing based on the analysis.

A moving dynamic mesh concept was adopted because of its capability to facilitate solving transient flow problem and motion of the domain boundaries. A simulated motion control was decided based on the time step, angular velocities of gears rotation motion and coded through a User defined function (UDF) to give angular momentum. Each analysis was carried out for 180 degree of rotation. The main parameter mass flow rate was monitored for different speed and outlet pressures. A validation experimental test was carried out at one rpm thus build up a confidence in implant design synthesis to meet challenges in future.
Comparative Study Between In-Situ Measured Vibration Data at Bearing and BTT on a LP Turbine Last Stage Blades in a Steam Turbo-Generator Set
Authors: Hahn W. , Sinha Jyoti K.
Published: July 2018

Cracking of the last stage blades of the low pressure (LP) turbines has been observed after 2007 in the 2 steam turbo-generator (TG) units out of the 4 units at the West Burton Power Plant UK. These 2 units were retrofitted with the new design LP rotor including blades in 1995 and 1997. Recent vibration measurements during machine transient and steady state operations confirms that the TG sets are running close to the machine critical speed and the blades are expected to have high vibration. Now the Unit 3 is fitted with the blade tip timing (BTT) system to monitor the LP1 last stage blades. Hence the present effort to compare the vibration of the blades by the BTT system with the bearing vibration to establish the correlation such that the status of the blade vibration can be accessed even without BTT measurement and the correlation may be used for other units with similar dynamics. The paper presents the comparison of the in-situ vibration measurement on bearings during machine run-up with online BTT data, observations, and possible correlation.
Experimental Studies on Stall Behavior in a Single Stage Transonic Axial Flow Compressor
Authors: Alone Dilipkumar Bhanudasji , Kumar Subramani Satish , Thimmaiah Shobhavathy M. , Mudipalli Janaki Rami Reddy , Pradeep A. M. , Iyengar Venkat S. , Ramamurthy Srinivasan
Published: July 2018

This paper describes the study of flow behavior of the transonic compressor stage in un-stalled and stalled conditions. Experiments were carried out in an open circuit single stage transonic axial flow compressor test rig. The test compressor was designed for 1.35 total to total pressure ratio at corrected mass flow rate of 22 kg/s. Both steady and unsteady measurements were carried out. The operating envelop of the compressor was experimentally determined to demark the stable and unstable operating range of the compressor at different operating speeds. Variations in the rotor inlet axial and tangential velocity in the tip region were studied using a calibrated single component hot wire probe. The compressor blade element performance was obtained at full flow and near stall conditions using a three hole aerodynamic probe. The variation in flow parameters like absolute flow angle, axial Mach number, absolute Mach number, tangential Mach number, static and total pressure ratio profiles at the rotor exit were obtained and their variations along the blade height were studied at full flow and near stall conditions. Static pressure variation in the tip region along the rotor chord was studied which showed reduction in slope as stall approached. Hotwire measurements showed abrupt variation in the axial velocity as compared to tangential velocity at stalled condition. It was observed that the flow turned in tangential direction at stall, as tangential component of velocity shows more fluctuations at stall in comparison with unstalled condition. The FFT analysis of the raw signals was performed and it was observed that the nature of the rotating stall was abrupt and stall cell travels nearly at half the rotor speed.
Experimental Investigation of Liquid Jet Breakup in Cross Flow of Swirling Air Stream
Authors: Sikroria Tushar , Kushari Abhijit , Syed Saadat , Lovett Jeffery A.
Published: July 2018

This paper presents the results of an experimental investigation of liquid jet breakup in a cross-flow of air under the influence of swirl (swirl numbers 0 and 0.2) at a fixed air flow Mach No. 0.12 (typical gas turbine conditions). The experiments have been conducted for various liquid to air momentum flux ratios (q) in the range of 1 to 25. High speed (@ 500 fps) images of the jet breakup process are captured and those images are processed using MATLAB to obtain the variation of breakup length and penetration height with momentum flux ratio. Using the high speed images, an attempt has been made to understand the physics of the jet breakup process by identification of breakup modes — bag breakup, column breakup, shear breakup and surface breakup. The results show unique breakup and penetration behavior which departs from the continuous correlations typically used. Furthermore, the images show a substantial spatial fluctuation of the emerging jet resulting in a wavy nature related to effects of instability waves. The results with 15° swirl show reduced breakup length and penetration related to the non-uniform distribution of velocity that offers enhanced fuel atomization in swirling fuel nozzles.
Thermo-Mechanical Stability Analysis of Composite Cylindrical Panels
Authors: Katariya P. V. , Panda S. K.
Published: July 2018

In this article, stability behavior of laminated composite curved panels under thermo-mechanical loading is analyzed. A generalized panel model is developed based on higher order shear deformation theory by taking the nonlinearity in Green-Lagrange sense for thermal distortion. The critical buckling load (mechanical/thermal) parameters are obtained by using the developed finite element model validated for both ANSYS and homemade computer code. The model has been discretized in ANSYS using an eight-noded serendipity shell element (shell281) and a nine noded isoparametric element for the computer code. The convergence test has been carried out and the results are compared with those available published literature. In this analysis, a uniform temperature distribution through the thickness is taken and the material properties for the composites are assumed to be temperature invariant. We note substantial effect of different parameters (support conditions, number of layers, thickness ratio and modular ratio) on thermo-mechanical stability behavior of laminated structures.
Design and Analysis Software for Propellers
Authors: Prathapanayaka Rajeevalochanam , Vinod Kumar Nanjundaiah , Settisara Janney Krishnamurthy , Nagishetty Hari Krishna
Published: July 2018

Recent interest in the field of micro and nano scale air vehicles attracted the attention of many researchers all over the world. The challenge associated with these classes of vehicles is to develop efficient miniaturized components. There are different types of micro and nano air vehicles out of which fixed wing micro air vehicle is one of them. Propulsion system for most of the fixed wing MAVs is propeller driven by an electric motor powered by a battery. The endurance of the MAV mainly depends on the performance of these two components. Hence there is a scope to improve the performance of the propeller and motor. Efficient propeller design and its performance analysis are an iterative process and time consuming. In the present study, to ease the process of propeller design and analysis NALPROPELLER code has been developed using MATLAB. This code is based on minimum induced loss theory presented by E.E.Larrabee to generate planform, blade element momentum theory along with Prandtl hub-tip loss model for overall performance analysis and the performance plots could be viewed in the GUI windows. The code consists of three modules namely single airfoil design, multi airfoil design and analysis module. This code is compared with one of the propeller design and analysis code available in the internet JavaProp by Martin Hepperle, which is also based on minimum induced loss method.

From literature Eppler 193 airfoil show high lift to drag ratios at low Reynolds numbers [16]. Eppler-193 airfoil is used in the evaluation of propeller performance.

A four inch diameter, two bladed, fixed pitch propeller is designed and analysed using this code. The design is compared with one of the design software JavaProp available online as an open source. A poly urethane casting propeller is fabricated based on the design. The performance comparison of the NALPROPELLER code, JavaProp and 3D CFD analysis is presented and discussed.
Linear Static and Free Vibration Analyses of Laminated Composite Spherical Shells
Authors: Singh Vijay K. , Panda S. K.
Published: July 2018

Linear static and free vibration behavior of laminated composite square base spherical shell panel has been investigated using finite element method. The present shell panel model is developed using ANSYS parametric design language code in ANSYS platform. The model is discretised using an eight nodded serendipity element (SHELL281) with six degrees of freedom per node from ANSYS element library. The responses are obtained using Gauss elimination and Block-Lanczos steps for the static and free vibration analysis, respectively. The results are computed using present developed model and the convergence test has also been done. Based on the convergence new results are obtained and compared with published results. The numerical simulations done for different parameters showing that the parameters such as thickness ratios, curvature ratios and lay up sequences have significant effect on transverse central deflections and fundamental free vibration frequencies of the shell structures.
Aeroderivative Gas Turbine Coupling Generator Redesign
Authors: Hernández Rossette Alejandro , García Illescas Rafael , Mazur Zdzislaw
Published: July 2018

A major failure event was experienced at a 44 MW plant powered by four aeroderivative gas turbines arranged in two units, property of the Federal Commission of Electricity (CFE).

The failure consisted of total fracture in the shaft coupling between the generator and free-turbine. Unit 2 has a twin pack configuration with two aero derivative Pratt&Whitney 20 MW gas turbines coupled to one generator at both end sides. The “A” side generator coupling was completely damaged as well as the coupling configuration at the free turbine.

Failure analysis showed as root cause, an abnormal configuration of the coupling systems between the free turbine to rotor generator at side “A”. This side had an additional shaft component to compensate a longer coupling distance between the turbine and generator. This was longer than the original distance, generating additional dynamic forces during operation leading to a fatigue failure mechanism.

The replacement coupling configuration for the rotor generator was different than the Original Equipment Manufacturer (OEM). The new (non-OEM) spare rotor generator was shorter in the longitudinal direction than the original one, forcing the addition of a new shaft in one side of the generator.

This work describes the rehabilitation process of the generator coupling by the replacement of the old configuration by a new redesigned coupling. This was done keeping the original configuration distances and components for both end shaft sides of the rotor generator. The paper includes the redesigned couple analysis by finite element method and the in-situ activities for the installation of the new couple in the rotor generator.
Comparison of Data Processing Techniques for Convective Heat Transfer Measurements in a Transient Transonic Hot Wind Tunnel
Authors: Xue S. , Roy A. , Ng W. F. , Ekkad S. V.
Published: July 2018

The present study compares two data processing techniques of calculating convective heat transfer coefficient (HTC) for experiments carried out at the Virginia Tech transonic wind tunnel facility. The discussion starts from the physical models and basic assumptions of the two methods denoted as Curve Fitting and Linear Regression, and is followed by application of both methods with the same set of experimental data for a comparative analysis. The linear regression method is found to be superior to the curve fitting method in eliminating the errors caused due to the transient starting up effect of the hot blow down.
Cooling Efficiency Enhancement Using Impingement Cooling Technique for Turbine Blades
Authors: Rajamani Keerthivasan , Ganesh Madhu , Paramanandam Karthikeyan , Jayamurugan Chandiran , Narayanan Sridharan R. , Srinivasan Balamurugan , Chandra A.
Published: July 2018

The effect of impingement cooling on the internal surface (cooling passage) of the leading edge region in a commercial turbine high pressure first stage rotor blade is investigated using Computational Fluid Dynamics (CFD) simulations. The flow domain is obtained by stretching the middle cross section (50% span) of the above mentioned blade. The simulations are performed for 3 different profiles in the cooling flow passage. In all the cases, the nozzle position and Mach number of cooling fluid is kept constant at E/D = 4.32 and 0.4 respectively. In the first case, the suction side profile is modified to facilitate shift in the vortex. This may reduce the crossflow effect, which will enhance the Nuavg. However, simulation results showed that Nuavg is reduced by 2% when compared to base case. In the second case, the coolant flow passage is smoothened at the apex to reduce dead zone and to enhance spreading of the jet. In this case, a 3% increase in Nuavg is obtained. Based on the analysis of velocity contours in the second case, the coolant flow passage in the third case is further modified to improve the spreading of flow. This resulted in 5% increase in the Nuavg when compared to base case.
Numerical Study on the Effect of Limiting Eddy Viscosity on Flow Separation Prediction for Airfoils in Wind Energy Applications
Authors: Loganathan Jaikumar , Sengupta Anindya , Gopinath Ashok
Published: July 2018

Pressure driven flow separation is an important category of flows and many aerodynamic devices are required to operate on the verge of boundary layer separation to maximize efficiency. Flow fields in wind engineering are inherently complex and are characterized by frequent occurrence of separated flows. Current one- and two-equation turbulence models do not capture all the relevant physics associated with flow separation and, hence, can result in erroneous predictions. These models are based on the Boussinesq assumption that relates the apparent turbulent shearing stresses to the rate of mean strain through an apparent scalar turbulent or “eddy viscosity”. A known drawback of this assumption is the inability to account for rapid changes in length scale which hence results in prediction of higher eddy viscosity. In this study the effect of limiting eddy viscosity in a k-ω SST model in CFX solver is studied and applied to predict flow over wind turbine airfoils like S825 and S827. For a certain clipping ratio range a significant improvement in separation prediction was observed when compared to the baseline turbulence model. The evolution of eddy viscosity and its impact on the macro scale flow structures is also discussed.
Numerical Study of Nanofluids Flow Characteristics Using LES–Lagrange Method and Molecular Dynamics Simulation
Authors: Hu Chengzhi , Heng Peng , Bai Minli , Lv Jizu , Wang Yuyan , Li Xiaojie
Published: July 2018

In order to reveal the mechanisms of heat transfer enhancement in nanofluids from the flow characteristics, this paper firstly used LES (Large eddy simulation)–Lagrange method to simulate the turbulent flow of nanofluids through a straight circular tube. It has been observed that nanoparticles would move up and down and sideways besides main flowing. The turbulent characteristics of nanofluids have been changed greatly in comparison with pure water: the turbulent intensity and Reynolds stress are enhanced obviously; there are more vortexes in the flow field. These flow characteristics of nanofluids can effectively strengthen the transport of momentum, mass and energy, which is the main reason for heat transfer enhancement in nanofluids. It is also found that nanofluids containing smaller diameter nanoparticles have higher turbulent intensity and flow activity. The flow characteristics of nanofluids are sensitive to the changes of smaller diameter nanoparticle size. While using different nanoparticle materials, the flow characteristics of nanofluids have a little change. At last, to verify the aforesaid views, the flow behaviors of nanofluids in the near wall region and main flow region have been simulated by molecular dynamics.
Experimental Study of VACNT Arrays as Thermal Interface Material
Authors: Ji Yulong , Li Gen , Ma Hongbin , Sun Yuqing
Published: July 2018

In order to improve thermal interface material (TIM), vertically aligned carbon nanotube (VACNT) arrays were synthesized by the chemical vapor deposition method, and then transferred by dipping in hydrofluoric acid (HF acid) solution to get a free standing VACNT array. Different TIM samples with sandwiched structures were fabricated by inserting the free standing VACNT arrays between two copper plates with and without bonding materials. The laser flash analysis method was applied to measure the overall thermal conductivity of these samples. Results show that: compared with two copper plates in direct contact, thermal conductivity of samples only with VACNT arrays as TIM can be enhanced about 142%–460% depending on the thickness of VACNT arrays. Conventional TIM made up of thermal paste (TG-550 with thermal conductivity of 5 W/mK) and a thermal pad (TP-260 US with thermal conductivity of 6 W/mK) was used as a bonding material between copper plates and VACNT arrays, thermal conductivity has been shown to further improve with the highest values at 8.904 W/mK and 10.17 W/mK corresponding to the different bonding materials and different thicknesses of VACNT arrays used. Results also show that the thicker the VACNT array is when used as a TIM, the lower the overall thermal conductivity of the corresponding samples. This lower thermal conductivity caused by more defects in amorphous carbon of thicker VACNT arrays and lower density of the corresponding sandwiched samples.
The Fourier Law at the Macro and Nanoscale
Authors: Prevenslik Thomas
Published: July 2018

The Fourier law implicitly assumes transient thermal disturbances are carried throughout the solid at an infinite velocity while not defining the carrier mechanism. Paradoxically, the phonon and electron carriers on which the Fourier law is based are limited to acoustic velocities. At the macroscale, the paradox is resolved by the thermal BB photons of QM that carry the Planck energy E = kT of the atoms in the disturbance throughout the solid at the speed of light. BB stands for blackbody and QM for quantum mechanics. The traditional Fourier equation in lattice temperature is expressed in terms of the Planck energy E of the atoms to show infinite carrier velocity is reasonably approximated by BB photons at the speed of light, thereby avoiding the unphysical alternative that absent BB photons the Fourier law is required to rely on thermal disturbances travelling at infinite velocity. Practically, the effect of BB photons on the accuracy of the Fourier solution is insignificant as the BB transient response of the semi-infinite solid is shown identical to that which includes the lag time caused by the speed of light. Fourier’s law is not applicable at the nanoscale as by QM the Planck energy of the atom is not available to be carried through the solid by the BB photon.
Enhanced Absorption of Carbon Dioxide Gas by Methanol Based Nanofluids in a Taylor-Couette Absorber
Authors: Pineda Israel Torres , Kang Yong Tae
Published: July 2018

Mass transfer enhancement by the use of nanoparticles suspended in a liquid phase (known as nanofluids) has been studied in recent years with positive results. Different theories have been proposed to explain the improvement in mass transfer, however it has not been possible to elucidate a definite answer. While the theory is still uncertain the experimental work continues in areas that will benefit much such as non-reactive gas absorption. In this study carbon dioxide (CO2) absorption experiments are performed in a Taylor-Couette absorber at different rotational speeds. The base fluid for the experiments is methanol. Al2O3 and SiO2 nanoparticles are combined with methanol to produce nanofluids with the purpose of enhancing the absorption of the CO2 gas into the methanol. The system is equipped with a mass flow controller at the inlet and a mass flow meter at the outlet to obtain the absorption rate. The Taylor-Couette absorber performance is compared to a modified version in which trays were added to enhance the absorption rate. Experiments in co-current and counter-current flow modes are carried out. The results of continuous absorption are presented. In addition, the two-phase flow pattern of the CO2 gas bubbles and the liquid methanol in the Taylor-Couette absorber and the modified version is analyzed with pictures obtained by a high speed camera.
Experimental Study of Wide-Range Spectral Radiation Properties of Air Plasma Sprayed Thermal Barrier Coatings
Authors: Yang Gang , Zhao Changying
Published: July 2018

In this paper the radiative properties of air plasma sprayed (APS) thermal barrier coatings are investigated by measuring the spectral diffuse reflectance and transmittance of samples with various thickness and porosities in a broad spectral band ranging from 0.25 to 15μm. The spectral absorption and scattering coefficients are obtained by a four flux model based on the experimental data. The results show that the porous zirconia ceramics exhibits high scattering coefficient (> 15000 m−1) and low absorption coefficient (< 500 m−1) in the spectral range from 0.5 to 6μm, and the corresponding spectral scattering albedo reaches up to 0.99. In addition, this study also found that the spectral scattering coefficient increases with increasing porosity, while the spectral absorption coefficient is not quite sensitive to the change of porosity. This result confirms the fact that scattering is mainly caused by the refractive index mismatch between bulk YSZ and internal void. Spectral scattering coefficient heavily depends on the microstructures of coatings, i.e., pore size, porosity and pore distribution, and this will in turn considerably affect the thermal radiation heat transfer inside the coating.
Compound Effect of EHD Force and Micro-Structured Surface Coated With Diamond Particles
Authors: Kano Ichiro
Published: July 2018

Boiling heat transfer enhancement via compound effect of the EHD effect and micro-structured surfaces has been experimentally and analytically investigated. A fluorinated dielectric liquid was selected as the working fluid. Pool boiling heat transfer in the saturated liquid was measured at atmospheric pressure. Micro-structured surfaces, which are mainly used for cutting tools, were developed with diamond particles using electro-deposition technique. Four different particle diameters were prepared: 5, 10, 15, and a mixture of 5 and 1.5 μm. The surface containing a mixture of 5 and 1.5 μm provided a 7 K reduction in the incipient superheat and a 26 % increase in the critical heat flux compared with those of a non-coated surface. Upon application of a −5 kV/mm electric filed to the micro structured surface (a mixture of 5 and 1.5 μm particles), a heat flux of 70.2 W/cm2 at a superheat of 21.7K was obtained. The experimental data correlated well with previous theoretical analysis.