bluuebunny/crossref_metadata_2025 huggingface dataset:
Age‐related bone loss is associated with FGF21 but not IGFBP1 in healthy adults
Authors: Lee Shuen Yee , Fam Kai Deng , Chia Kar Ling , Yap Margaret M. C. , Goh Jorming , Yeo Kwee Poo , Yap Eric P. H. , Chotirmall Sanjay H. , Lim Chin Leong
Published: January 2020

What is the central question of this study?

Fibroblast growth factor 21 (FGF21) plays important therapeutic roles in metabolic diseases but is associated with bone loss, through insulin‐like growth factor binding protein 1 (IGFBP1), in animals. However, the effect of the FGF21–IGFBP1 axis on age‐related bone loss has not been explored in humans.

What is the main finding and its importance?

Using ‘genetically linked’ parent and child family pairs, we show that the FGF21 concentration, but not the IGFBP1 concentration, is higher in older than in younger adults. Our results suggest that age‐associated decline in bone mineral density is associated with FGF21 and increased bone turnover but not likely to involve IGFBP1 in healthy humans.

Bone fragility increases with age. The fibroblast growth factor 21 (FGF21)–insulin‐like growth factor binding protein 1 (IGFBP1) axis regulates bone loss in animals. However, the role of FGF21 in mediating age‐associated bone fragility in humans remains unknown. The purpose of this study was to explore the FGF21‐regulatory axis in bone turnover and the age‐related decline in bone mineral density (BMD). Twenty ‘genetically linked’ family (parent and child) pairs were recruited. Younger adults were 22–39 years old and older adults 60–71 years old. The BMD and serum concentrations of FGF21, IGFBP1, receptor activator of nuclear factor‐κB ligand (RANKL), tartrate‐resistant acid phosphatase 5b (TRAP5b) and bone‐specific alkaline phosphatase (BAP) were measured. Older adults had 10–18% lower BMD at the hip and spine (P < 0.008) and a twofold higher FGF21 concentration (P < 0.001). The IGFBP1 concentration was similar in younger and older adults (P = 0.961). The RANKL concentration was 44% lower (P = 0.006), whereas TRAP5b and BAP concentrations were 36 and 31% higher (P = 0.01 and P = 0.004), respectively, in older adults than in younger adults. Adjusting for sex did not affect these results. The FGF21 concentration was negatively correlated with BMD at the spine (r = −0.460, P = 0.003), but not with the IGFBP1 concentration (r = −0.144, P = 0.374). The IGFBP1 concentration was not correlated with BMD at the hip or spine (all P > 0.05). In humans, FGF21 might be involved in the age‐associated decline in BMD, especially at the spine, through increased bone turnover. IGFBP1 is unlikely to be the downstream effector of FGF21 in driving the age‐associated decline in BMD and in RANKL‐associated osteoclast differentiation.
Determining the Optimal Location of Vent Augmenters in an Elliptical-Bladed Savonius Rotor
Authors: Alom Nur , Saha Ujjwal K.
Published: January 2020

The Savonius wind turbine rotor, or simply Savonius rotor is gaining importance throughout the globe as a device to produce electric power without donating much to global warming. Although this type of conventional rotor suffers from lower efficiency, it has many important rewards like simplicity, easier manufacturability, and lower maintenance cost. This has attracted the researcher’s attention towards improving its design further. To improve the Savonius rotor performance, several blade profiles/shapes and augmentation techniques have been evolved. In this study, an effort has been made to investigate the performance of a novel elliptical blade profile by incorporating the vent-augmentation technique. The prime objective is to decrease the negative thrust of the rotor by locating the vents optimally on the blade concave surface. In view of this, the vents are created at three different positions on the blade concave surfaces. Two-dimensional (2D) unsteady simulations are performed around the vented blade profiles of the Savonius rotor using SST k-ω turbulence model by FVM based solver ANSYS Fluent. The torque and power coefficients (CT and CP) are calculated at the revolving environments. The total pressure and velocity contours are obtained and analyzed. For a direct judgement, the results are also generated for the blade profiles without vent-augmenters. The study reveals an enhancement in performance of the vent-augmented elliptical blade profile of the Savonius rotor.
Brayton Cycle Supercritical CO2 Power Block for Industrial Waste Heat Recovery
Authors: Sathish Sharath , Kumar Pramod , Nagarathinam Logesh , Swami Lokesh , Namburi Adi Narayana , Bandarupalli Venkata Subbarao , Gopi Pramod Chandra
Published: January 2020

The Brayton cycle based supercritical CO2 (sCO2) power plant is an emerging technology with benefits such as; higher cycle efficiency, smaller component sizes, reduced plant footprint, lower water usage, etc. There exists a high potential for its applicability in waste heat recovery cycles, either as bottoming cycles for gas turbines in a combined cycle or for industrial waste heat recovery in process industries such as iron & steel, cement, paper, glass, textile, fertilizer and food manufacturing. Conventionally steam Rankine cycle is employed for the gas turbine and industrial waste heat recovery applications. The waste heat recovery from a coke oven plant in an iron & steel industry is considered in this paper due to the high temperature of the waste heat and the technological expertise that exists in the author’s company, which has supplied over 50 steam turbines/ power blocks across India for various steel plants. An effective comparison between steam Rankine cycle and sCO2 Brayton cycle is attempted with the vast experience of steam power block technology and extending the high pressure-high temperature steam turbine design practices to the sCO2 turbine while also introducing the design of sCO2 compressor. The paper begins with an analysis of sCO2 cycles, their configurations for waste heat recovery and its comparison to a working steam cycle producing 15 MW net power in a coke oven plant. The sCO2 turbomachinery design follows from the boundary conditions imposed by the cycle and iterated with the cycle analysis for design point convergence. The design of waste heat recovery heat exchanger and other heat exchangers of the sCO2 cycle are not in the scope of this analysis. The design emphasis is on the sCO2 compressor and turbine that make up the power block. This paper highlights the design of a sCO2 compressor and turbine beginning from the specific speed-specific diameter (Ns-Ds) charts, followed by the meanline design. Subsequently, a detailed performance map is generated.

The relevance of this paper is underscored by the first of a kind design and comparative analysis of a Brayton sCO2 power block with a working Steam Power block for the waste heat recovery in the energy intensive iron and steel industry.
Conjugate Heat Transfer Analysis of a Small Annular Combustor With Centrifugal Fuel Injection System
Authors: Rana Rampada , Prajwal Alosri , Sivaramakrishna Gullapalli , Navindgi Raju Dharappa , Muthuveerappan Nagalingam
Published: January 2020

Over the years, the requirements of higher specific thrust and lower specific fuel consumption have been necessitating a continual increase in the maximum temperature and pressure in gas turbine engines. However, such an increase has a direct impact on the structural integrity of various modules of the engine; combustor being one of the severely affected modules. This makes the combustor designer’s task of achieving the targeted life of liner, the hottest component of combustor, a challenging one. Estimation of liner metal temperature, thereby arriving at the combustor life, is an essential part of the design process. In the present study, CHT analysis of a radial annular combustor has been carried out. RANS based analysis of a sector combustor with periodicity in flow and geometry has been performed at realistic engine operating conditions using ANSYS Fluent. Predicted liner metal temperatures have been compared with the measured data and a close agreement has been noted between them, the maximum variation being ± 10%.
Design and Development of Aeroderivative Gas Turbine Lifting and Handling Structures
Authors: Santhanagopalakrishnan Babu , Ghumre Milind , Kammalapalli Ramesh , Pittella Gianfranco
Published: January 2020

Gas turbines Lifting devices (such as lifting lugs, eye bolts, trunnions, are provided on large stationary gas turbine parts as an aid in manufacturing, assembly, transport, shipping, test, installation, repair, and serviceability. Trunnions are used to lift the entire turbine including the base during assembly, transportation and installation Similarly, lugs are used to lift major components such as stator tube casings and subassemblies. In some circumstances there are geometric, fatigue, or assembly constraints that make the use of lugs problematic. In these circumstances, other approved lifting devices such as eye bolts, swivel hoist rings, and shackles may be used. Other devices may also be used for parts smaller than stator tube casings.

This paper presents the design and development of the Aeroderivative gas turbine lifting and support lug features which are used for lifting, handling and transportation of the full gas turbine. It describes the challenges encountered during development of LPT lifting lugs to meet product requirements. The effects of full engine deformations due to support legs under worst case conditions of full engine handling are presented here. The benefits resulted due change in lug position are explained which is leveraged for the final production design. It also talks about the various design options considered to reduce stresses and simplify the lugs manufacturing.
A Numerical Study on the Effect of Unbalance and Misalignment Fault Parameters in a Rigid Rotor Levitated by Active Magnetic Bearings
Authors: Kumar Prabhat , Tiwari Rajiv
Published: January 2020

This paper focusses on analysing the vibration behaviour of a rigid rotor levitated by active magnetic bearings (AMB) under the influence of unbalance and misalignment parameters. Unbalance in rotor and misalignment between rotor and both supported AMBs are key fault parameters in the rotor system. To demonstrate this dynamic analysis, an unbalanced rigid rotor with a disc at the middle levitated by two misaligned active magnetic bearings has been mathematically modelled. One of the novel concepts is also described as how the force due to active magnetic bearings on the rigid rotor is modified when the rotor is parallel misaligned with AMBs. With inclusion of inertia force, unbalance force and force due to misaligned AMBs, the equations of motion of the rigid rotor system are derived and converted into dimensionless form in terms of various non-dimensional system and fault parameters. Numerical simulations have been performed to yield the dimensionless rotor displacement and controlling current responses at AMBs. The prime intention of the present paper is to study the effect on the displacement response of the rigid rotor system and the current consumption of AMBs for different ranges of disc eccentricities and rotor-AMB misalignments.
Computational Analysis on the Use of Various Nimonic Alloys As Gas Turbine Blade Materials
Authors: Subbarao Rayapati , Mahato Nityanando
Published: January 2020

Blade failure is triggering more problems to the gas turbine engines, while being used in airline and jet engines. In this paper, causes of blade failure with respect to various Nimonic alloys is investigated by performing structural and thermal analyses. Using Ansys, both these analyses on turbine blade are carried out, which is utilized for determining equivalent stresses, deformation and thermal stresses by applying different turbine inlet temperatures and pressures. Turbine blade model is prepared using Solid Works. The computational model is then imported to Ansys workbench. Before importing to the solver, the domain is meshed and boundary conditions are applied. Properties like coefficient of thermal expansion and thermal conductivity are given as material conditions. Ambient temperature, rotational speed, inlet pressure and temperature are considered as boundary conditions. For various configurations and alloy materials, deformation, strain and thermal stresses are plotted and analyzed. After thorough investigation, the turbine blade failure region is identified and the trend is compared for different input temperatures and pressures. At the root of the blade, the stresses and strains are found to be more. Of all the materials considered, Nimonic-90 has less deformation and thermal stresses. Nimonic-80A has more equivalent stress, strain and deformation. Out of the other two materials, Nimonic-263 is showing favourable properties than Nimonic-105. However, the values of stresses and strains are comparable. Thus the present work is beneficial in identifying suitable Nimonic alloy as gas turbine blade material in order to avoid the frequent turbine blade failures.
Analysis of Static and Dynamic Performance Parameters of Two-Lobe Journal Bearing Operating With Non-Newtonian Lubricant
Authors: Kumar Ashutosh , Kakoty Sashindra Kumar
Published: January 2020

Static and dynamic performance parameters of two-lobe journal bearing, working with non-Newtonian lubricant has been obtained. Krieger-Dougherty model is used to obtain the effective viscosity of nano-lubricant for a given concentration of solid-particle in base lubricant. Modified Reynolds equation is solved to obtain bearing performance parameters for couple stress model and variable viscosity model. Dynamic coefficients are also determined for various couple stress parameter. Results reveal a noticeable increase in flow co-efficient and load carrying capacity while there is a decrease in friction variable. It also reveals a significant betterment in dynamic co-efficient of bearing.
Experimental and Numerical Assessment of Cross Flow Vertical Axis Wind Turbine
Authors: Seralathan Sivamani , Thomai Micha Premkumar , Jayakumar Rian Leevinson , Lokesh Reddy Basireddy Venkata , Venkatesan Hariram
Published: January 2020

Due to increase in energy demand along with environmental awareness, the attention is shifting towards renewable energy sources. A wind turbine developed from Banki water turbine is used in this study as it starts at low-wind speeds and has high starting torque. Experimental investigations are carried out on a test rig equipped with open jet wind tunnel with wind velocity varying from 7 to 11 m/s. Later, 3D steady-state numerical analyses are performed using ANSYS CFX for better understanding of the flow physics of cross flow VAWT. The experimental investigations revealed that cross flow VAWT has a good self-starting ability at relatively low-wind speeds. A peak power coefficient (Cp, max) value of 0.059 is observed for the tip speed ratio (λ) of 0.30. As the tip speed ratio is raised further, the Cp value is observed to decrease gradually. The numerical simulations reveal the reason for the drop in Cp value. This is due to lessening of positive interaction between the flow and cross flow VAWT blades at higher λ due to vortex formation. The torque coefficient is found to decrease almost linearly from a peak value of around 0.49 at λ = 0 to a value of 0 around λ = 0.60. Polar plot between angle and torque shows that torque output of the turbine is nearly same in all directions which reinforce the potency of cross flow VAWT to be omni-directional as it produces the same performance regardless of wind directions.
Acoustic Investigation on Unmanned Aerial Vehicle’s Rotor Using CFD-MRF Approach
Authors: Murugesan Ramesh , Raja Vijayanandh
Published: January 2020

Future developments have been indicated for further research and development in the Aeroacoustics of the components of Unmanned Aerial Vehicles (UAVs). In which the implementation of multi-rotor UAVs in the complex applications is quite high but it has the drawback of high drive-line noise levels, which is one of the prime radar detectability factors. As a result, an idea is emerged to design and test the quite UAV, in which the noise from propellers plays a major role. in order to the successful completion of the design study, a complete is conducted, in which the design parameters and various noise reduction methodologies in the rotating components have been noted and included in the final design. To minimize the noise signature issue in UAV, the idea finalized that to minimize the decibel of small Unmanned Aircraft System (UAS) propellers via leading-edge modifications. A computer-aided design of base propeller and three different versions propeller with leading-edge modifications are generated with the help of CATIA for Computational Fluid Dynamics (CFD) simulations. Comparative noise variation simulations between the existing and the propellers with modification are performed, in which dynamic conditions play a predominant to initiate the analysis and thereby the analyses are carried out with the help of ANSYS Workbench Fluent 16.2. Especially, to make an acceptable solution, the Moving Reference Frame (MRF) approach is used in order to capture the propeller rotation in an effective manner. Finally, a propeller with airfoil cut at the leading edge has induced the low noise.
Influence of Lewis Number on Heat Release Rate in Premixed Syngas Flames
Authors: Bhide Kedar G. , Sreedhara Sheshadri
Published: January 2020

Syngas is an attractive alternative to currently popular hydrocarbon fuels due to its ability to be synthesized from multiple sources and lower carbon content. Direct Numerical Simulation (DNS) studies on premixed and non-premixed syngas flames have recently received attention. In this light, DNS of turbulent premixed syngas has been performed. Influence of turbulence and differential diffusion effects on chemical pathways of fuels like Hydrogen and methane has been studied in the past. Similar study on syngas flame has not been reported in the literature. Two cases with variation in the intensity of turbulence have been reported in this study. Effect of differential diffusion and turbulence on heat release rate and fuel consumption rate has been discussed. The behavior of heat release rate and fuel consumption rate was largely similar between laminar and turbulent flames considered in this study. Influence of species Lewis number was found to be more pronounced than that of turbulence.
Simulation of Laser Cutting on Functionally Graded Material Used in Aviation Industry
Authors: Nath Subha , Das Apurba , Inaba Kazuaki , Karmakar Amit
Published: January 2020

Functionally graded materials (FGMs) are widely used in engineering applications for the advantages offered by the properties of materials in combination. It is a special type of composite material which is inhomogeneous (micro-scopically). Laser cutting offers advantages while cutting these materials compared to traditional cutting methods. The objective of this work is to investigate numerically the effect of process parameters such as laser power and scanning speed on kerf width, depth of cut and thermal stress. Gaussian heat source, representing the laser beam, is applied along a straight line path through the middle of the work piece. The FGM considered in this work material mainly consists of a FGM made of nickel and stainless steel (AISI 304). The work piece is assumed to be symmetric. In this simulation finite element software COMSOL MULTIPHYSICS is used to simulate the thermo-mechanical model. The model is meshed with nonuniform pattern tri-angular mesh. It is observed from the results of numerical simulation that with the increase of laser power the width and depth of the cut has increased. The cut has a very narrow kerf width with increasing scanning speed leading to considerable saving in material. The variation in thermal stress is observed on the material with the considered parameters.
Effect of Laser Energy Density on Bulk Properties of SS 316L Structures Built by Laser Additive Manufacturing Using Powder Bed Fusion
Authors: Nayak Saurav K. , Mishra Sanjay K. , Paul Christ P. , Jinoop Arackal N. , Yadav Sunil , Bindra Kushvinder S.
Published: January 2020

Laser Additive Manufacturing using Powder Bed Fusion (LAM-PBF) is one of the revolutionary technologies playing a key role in fourth industrial revolution for redefining manufacturing from mass production to mass customization. To upkeep the pace, Raja Ramanna Centre for Advanced Technology (RRCAT) has indigenously developed an LAM-PBF system and it is being used for process and component development for various engineering applications. This paper reports a parametric investigation to evaluate the influence of process parameters on the sample properties and to develop the process window for fabricating complex shaped engineering components. In the present work, an experimental investigation is carried out to investigate the effect of Laser Energy density (LED) on the porosity, microstructure and mechanical properties of SS 316L bulk structures fabricated by LAM-PBF system. LED is a combined parameter simultaneously considering the effect of Laser Power (P), Scan Speed (v), hatch spacing (h) and layer thickness (t). The effect of three LED values such as 83.33 J/mm3, 253.97 J/mm3 and 476.19 J/mm3 is investigated in the present work by building cuboidal samples at a layer thickness of 75 microns. Porosity is estimated using area fraction method in optical microscopy and it is found that the minimum porosity of 0.14 % and pore area of 1.28 mm2 are observed at 253.97 J/mm3. Maximum porosity of 18.85 % is observed at 83 J/mm3 due to incomplete fusion defects. However, porosity observed at 475 J/mm3 is 6.56 % with average pore size of 17.8 mm2. Microstructural studies show primarily columnar growth in all the samples with fine dendrites. The dendrite size is observed to be 3.2 μm, 2.4 μm and 1.46 μm at 83.33 J/mm3, 253.97 J/mm3 and 476.19 J/mm3 respectively. Micro-hardness and single cycle automatic ball indentation studies are found to be in agreement with dendritic size, with lower hardness at larger dendrite size. X-Ray Diffraction (XRD) studies indicate similar peaks at all the conditions, with slight peak shift observed with increase in LED primarily due to higher amount of residual stress. Thus, it can be inferred that LED of 253.97 J/mm3 is suitable for fabricating engineering components due to combination of lower porosity and fine dendritic structure.
Dynamic Characterization of an Additive Manufactured Turbine Wheel of Turbocharger
Authors: Selvam R. Panneer , Duraiselvam Muthukannan , Barad Sanjay G. , Kumar Dilip
Published: January 2020

Experimental Modal Analysis (EMA) is a conventional technique for establishing the modal parameters of the components. The modal parameters are the dynamic characteristics viz. frequency, mode shapes and damping that are used for assessing and validating the design predictions through correlation studies.

For this task EMA technique is adopted to assess the dynamic characteristics of an additive manufactured (AM) turbine wheel of a turbocharger. Correlation studies are undertaken to validate the theoretical model developed. These Correlation studies ensured that there is no major deviations to proceed for high speed spin testing of this turbine wheel in simulated environment. The possible interference or resonances in the operating range are identified for safe operation of the test rotor.
Investigation on Flow Characteristics and Performance of a Vertical Axis Wind Turbine With Deflector Plates
Authors: Karthik Selva Kumar K. , Kulkarni Vinayak , Sahoo Niranjan
Published: January 2020

In this article, a 3D computational study has been performed to understand the flow phenomenon over the vertical axis wind turbine with a three-bladed NACA0021. The rotary motion of the VAWT simulated with sliding mesh techniques with reference to the SST-Kω turbulence model using the CFD software. The observed results were found to be having a significant improvement in the enhancement of the power output. Also, the investigation was move forwarded to understand the flow characteristics of the VAWT with the presence of deflector plates in different orientation at the upstream conditions. The present of deflector plates creates an augmented flow phenomenon which creates an accelerated flow at the near wake region, causing a significant improvement in the coefficient of power of the wind turbine.
Metaheuristic Optimization of Dual-Element Vertical Axis Wind Turbine Using Genetic Algorithm
Authors: Kumar Sushrut , Gupta Priyam , Singh Raj Kumar
Published: January 2020

This paper presents a framework for the optimization of Dual-Element Vertical Axis Wind Turbine (VAWT) Blade configurations for improvement in power generation. Multi-element nature of the turbine was specifically chosen as this configuration offers better-attached flow over a conventional single element H-type turbine. The framework was based on a genetic evolutionary algorithm which is a metaheuristic optimization technique based on the principle of survival of the fittest. The class of genetic algorithm used was Invasive Weed Optimization. The geometry of the turbine consists of a rotor with three sets of dual-element airfoil oriented symmetrically. Effective chord length and relative chord angle were taken as modifying parameters for generating new configurations. The fitness of each individual was evaluated by performing two-dimensional Computational Fluid Dynamics Simulations. OpenFOAM was used for performing numerical simulations. Qualitative data of torque, pressure, velocity, and turbulence kinetic energy of best configuration is shown. A considerable increase in torque in the final geometry. The model was found ideal for optimizing multi-element VAWT configuration.
Lean Blowout Phenomena and Prior Detection of Lean Blowout in a Premixed Model Annular Combustor
Authors: Bhattacharya Arijit , Gupta Bikash , Hansda Satyajit , Haque Zohadul , Kumar Ashish , Mishra Manohar Kumar , De Somnath , Mukhopadhyay Achintya , Sen Swarnendu
Published: January 2020

Strict emission norms in the last few decades have paved the path for adaptation of new low NoX emission alternatives to power generation and aircraft propulsion. Lean combustion is a very promising and practicable technology for reducing NOX reduction and also have very high fuel efficiency. However, lean combustion technology suffers from inherent combustion instabilities that are manifested under different conditions, most importantly, thermoacoustic instability and lean blowout. Lean blowout occurs when a gas turbine combustor operating close to lean limit, for lowest NoX emission, faces abrupt changes in fuel homogeneity, quality or flow rate. While many work have been done in thermo-acoustic instability and flame propagation in annular combustors, studies in lean blowout in annular combustors are very limited. The lean limit of combustors are not fixed and is dependent on fuel characteristics and operating condition including environmental effects. So accurate online prediction of lean limit is very important to keep the combustors operating safely near lean limit. Recent works have demonstrated that single burner combustors leave out a significant amounts of physics including interaction of flames from different burners prior to blowout.

In this work, a stepped down swirl and bluff body stabilized annular combustor in CB configuration (having chamber and burner), is used as experimental test rig having 4 number of identical burners. Video and heat release data are taken at different conditions as lean blowout is approached. Frequent attachment and reattachment of the flames prior to lift off was seen. As lean blowout is approached, inherent subtle differences in the different burners get amplified when flame becomes sufficiently weak and flame symmetry is broken. As air fuel mixture is made gradually leaner, one by one the flames from different burners elongates although remains partially attached to burner. Further lowering the equivalence ratio results in lift off and merging of the flame fronts of different burners. Three pixel averaged color ratios are extracted from still camera RGB images as flame stability indicators which are, red by blue, red by green and blue by green. The parameters show marked change at the point of lift off as well as at the lean blowout point.
Random Field Modeling and Analysis of Rotor Bladed Disc Sector Using a Data Driven PCE Based Approach
Authors: Kumar Rahul , Gupta Sayan , Ali Shaikh Faruque
Published: January 2020

Bladed disc systems, are designed to be rotationally periodic i.e. each sector repeats itself in an angular manner. This ensures that the response characteristics preserve this rotational periodicity and is defined as a tuned system. However, due to manufacturing limitations, there are invariably random spatial variations in the sectors which constitute the rotor. This in turn destroys the periodicity (angular symmetry) of the rotor. Such a system is defined as a mistuned system, leads to energy localization and makes the rotor susceptible to damage leading to a loss of its service life. This study focusses on developing a methodology for modeling the random spatial inhomogeneities and integrating with finite element analysis for estimating the behavior of a sector of a rotor blade assembly. Approximations for the non-Gaussian random fields for the spatial inhomogeneities are directly developed from the data set of measurements available from coordinate measuring machine (CMM). Subsequently, Rosenblatt’s transformations are applied to each component of the discrete measurement data set for polynomial chaos (PC) representation of the parameter to get the estimated probability density function (pdf). Spearman’s rank correlation coefficient (SRCC) is calculated to obtain the correlation parameter. Kullback–Liebler entropy (KLE) is used as a metric to compare the estimated pdf obtained through the PC representation of the measured data. The in-house PC based developed codes are subsequently integrated with commercially available finite element software which enable quantifying the propagation of the spatial random uncertainties into the response characteristics. Statistical processing of the response quantities is carried out to estimate probabilistic measures of the corresponding response quantities.
Analysis of Part Electric Gas Turbine: A Novel Hybrid Propulsion Concept
Authors: Murthy M. S. N. , Kumar Subhash , Sreedhara Sheshadri
Published: January 2020

A gas turbine engine (GT) is very complex to design and manufacture considering the power density it offers. Development of a GT is also iterative, expensive and involves a long lead time. The components of a GT, viz compressor, combustor and turbine are strongly dependent on each other for the overall performance characteristics of the GT. The range of compressor operation is dependent on the functional and safe limits of surging and choking. The turbine operating speeds are required to be matched with that of compressor for wide range of operating conditions. Due to this constrain, design for optimum possible performance is often sacrificed. Further, once catered for a design point, gas turbines offer low part load efficiencies at conditions away from design point.

As a more efficient option, a GT is practically achievable in a split configuration, where the compressor and turbine rotate on different shafts independently. The compressor is driven by a variable speed electric motor. The power developed in the combustor using the compressed air from the compressor and fuel, drives the turbine. The turbine provides mechanical shaft power through a gear box if required. A drive taken from the shaft rotates an electricity generator, which provides power for the compressor’s variable speed electric motor through a power bank. Despite introducing, two additional power conversions compared to a conventional GT, this split configuration named as ‘Part Electric Gas Turbine’, has a potential for new applications and to achieve overall better efficiencies from a GT considering the poor part load characteristics of a conventional GT.
Numerical Analysis of Turbulent Mixing in Cross Flow Configurations
Authors: Patel Kashyap , Ram Chaina , Rasaniya Vishal
Published: January 2020

The gas turbine combustion chamber is a vital part of a gas turbine engine. Proper mixing of air in the combustor plays an important role in combustion. Increasing mixing rate is an important factor for better combustion efficiency. The injection of air in crossflow is widely studied over the years. The air injected at an angle in upstream direction gives better mixing by colliding with the crossflow. The computational analysis of the injected jet in cross flow is performed with different angles in the upstream direction. The k-omega SST turbulence model was used to investigate the mixing behavior. The air is injected at different angles and observed that with an increase in angle from 60° to 135°, the rate of mixing and turbulent intensity increased. The jet inclination in the upstream direction greatly influenced the mixing behavior. The jet penetration in perpendicular direction was almost the same for 120° and 135°. But there is added penalty in the form of the pressure loss at the angle 135°. So considering the pressure loss and ease of manufacturing the 120° jet inclination is preferable for better mixing among the four cases studied here. The idea of inclining jet in upstream direction can be implemented on the combustor for increased performance and shorter size.
Effect of Snubbers and Lacing Wire on Aerodynamic Performance of Last Stage Steam Turbine
Authors: Sreekumar P. , Varpe Mahesh K.
Published: January 2020

The aerodynamics design of a steam turbine stage is an agreement between the performance requirements and the mechanical limitations. The design of last stage of the low-pressure steam (LP) turbine is the most complicated because of the blade twist and a tapered blade along with high aspect ratio due to the sharp increase in the specific volume of the steam during its expansion. The choice of higher aspect ratio for increased power generation makes the turbine blade experience the vibration due to lower modal frequencies which depend on the running speed of a turbine. Therefore, the sensitive behavior of these blades is reduced by damping the blade vibrations which comes with the penalty of aerodynamic performance. The investigation reported here discusses the impact of lacing wire and snubber mounted at 70% blade span. Both, the lacing wire and snubber aligned parallel to the rotor axis deteriorates the efficiency by 0.75% and 1.7% respectively. However, the aerodynamically shaped snubber aligned with the streamline direction recovers the efficiency to that of base line. The mechanism of streamwise aligned snubber in containing aerodynamic performance loss is quite interesting and is being discussed.
Experimental Study of Self- Adjustable Flap for Fixed Wing MAV
Authors: Verma Anand , Kulkarni Vinayak
Published: January 2020

Current investigation is focused on experimental analysis for the improvement of aerodynamic performances of low aspect ratio wings (S5010 profile, AR = 1,2) at low Reynolds number. In this study self-adjustable flap is used as a lift enhancement device, is mounted on the suction surface of the wing. Present mounting allows the flap to rotate freely about its leading-edge without supplying any external energy. All the experiment performed in open circuit subsonic wind tunnel for the chord-based Reynolds number is 105. It has been observed, the flap remains attached to the wing surface at low angles of attack. But, as the angle of attack increases, flow separation initiates to occur along the trailing edge which lift ups the flap and adjusts itself in a situation so that the flow reattaches. Hence, the lift curve, for pre-stall angles is almost identical in both clean and flapped configurations. Further, both the flap locations are seen to improve the lift coefficient than the clean airfoil for post-stall angles. The flap is more effective for both the models when it is located at a position of 70% of chord length.
Novel Tubercle Design for a Wind Turbine Blade Operating at Low Reynolds Number
Authors: Deeksha R. , Varpe Mahesh K.
Published: January 2020

Wind energy has become one of the vital sustainable energy resources and a leading contender to the renewable resources race. The need of extending the aerodynamic performance of a wind turbine paved the way for radical approaches in the design of wind turbine blades. One such promising technique is the adoption of passive flow controls like leading edge protuberance or tubercles. In this paper the aerodynamic performance of NACA0009 (baseline) superimposed with a leading edge protuberance is numerically investigated in the post-stall operating conditions. The investigation objective was to identify the optimum pitch to amplitude ratio of the protuberance in the post stall operating condition for a low Reynolds number of 5 × 104. Computational fluid dynamics computations were performed using κ-ω SST turbulence model. The optimum pitch to amplitude ratio was found to be 6 which enhanced the aerodynamic lift coefficient by 42% in the post stall operating condition. The lift is reduced at lower AOA but gets complement in the post stall operating conditions.
Free Vibration Characteristics of Sandwich Conical Shells With FGM Face Sheets: A Finite Element Approach
Authors: Singha Tripuresh Deb , Das Apurba , Agarwal Gopal , Bandyopadhyay Tanmoy , Karmakar Amit
Published: January 2020

This paper presents an analytical investigation on the free vibration characteristics of symmetric sandwich conical shell with functionally graded material (FGM) face sheets using finite element method. Sandwich-type structures offer higher stiffness to weight ratio with excellent thermal barrier in high temperature application extending the operational life of the component. The sandwich-type conical structure used in the advanced supersonic and hypersonic space vehicles. The material properties of FGM face sheets are considered to be varied in thickness direction as per simple power law distribution in terms of the volume fractions of the FGM constituents. The core layer is considered as homogeneous and made of an isotropic material (Titanium alloy-Ti–6Al–4V). A finite element method is used to reduce the governing equations of vibration problem. The QR iteration algorithm used to solve the standard eigen value problem for determine the natural frequencies. Convergence studies are performed in respect of mesh sizes to substantiate the accuracy of the proposed method. Computer codes developed to obtain the numerical results for the combined effects of twist angle and rotational speed on the free vibration characteristics of symmetric sandwich conical shell with FGM face sheets. A detailed numerical study is carried out to examine the influence of the sandwich plate type, volume fraction index on the free vibration characteristics. The typical mode shapes are also illustrated for different cases.
Heat Transfer Enhancement With Vortex Generators
Authors: Islam Md. , Guangda L. , Ainane S. , Bojanampati S.
Published: January 2020

In this research, heat transfer and pressure drop from a tube with vortex generators (VGs) insert are numerically investigated. The effects of heights, attack angles of VGs inside a tube on heat transfer and flow behavior are investigated. CFD simulations, with and without VGs insert, are done for an air flow range (Reynolds numbers 6000 to 33000) and for a constant heat flux on the tube model surface. Four VGs are fitted in a circular pattern on the inner surface of the tube. We studied the characteristics of the delta winglet VGs for different attack angles and blockage ratios. The Nusselt number and friction factor results show the influence of the VGs insert on heat transfer and frictional factor. The maximum Nusselt number increment (Nu/Nu0) was achieved to be 1.75 while the maximum friction factor increment (f/f0) was 3.21. In order to understand the flow behavior and different vortices, path lines released by the VGs surface and details of the vortices are also studied.
Flow Interactions in Low Bypass Ratio Multi-Spool Turbofan Engines
Authors: Verma Vishwas , Singh Gursharanjit , Pradeep A. M.
Published: January 2020

Multi-spool compression systems are characterized by two or more compressor stages running at different rotational speeds. The response of an individual component can be different from an integrated system. Limiting operating conditions such as choke and stall points could have substantially different effects. The present paper explores the interactions and coupling significance between different stages of a multi-spool compression system. Further, an attempt is made by modifying the shape of the inter-compressor duct (ICD) to improve the system performance. The multi-spool system in this study comprises of the NASA stage 67 as the fan followed by in-house core and bypass ducts and a single stage booster. It is observed that the flow pattern in an ICD is entirely different in stand-alone modeling than in the integrated system modeling, owing to fan wakes and booster upstream influences. The booster performance is dependent on the duct exit flow pattern. The shape of the baseline ICD is tailored to reduce extra losses which is generated due to reduction in the length of the ICD and hence making the system more compact. It is shown that the shape tailoring optimization of ICD done independently result in a significant improvement in the duct exit flow pattern and hence an improvement in the booster performance. However, this gain in the performance is reduced to marginal values for an integrated system. This happens due to a strong coupling of the ICD flow pattern with the fan wakes and highly three dimensional nature of the ICD flow pattern. Therefore, it is found that component level optimization may not give rise to an equivalent system-level improvement.
Microstructure, Residual Stress and Wear Behaviour of Additively Manufactured Materials: Cold Spray L605 and DMLD IN718 and Maraging Steel for Gas Turbine Fuel Nozzle Repair
Authors: Sundaram Hariharan , Srinivasan Dheepa , Baummer James
Published: January 2020

Inconel 718 and Maraging Steel (18Ni300) were deposited via direct metal laser deposition (DMLD) on to high strength stainless steel (SS418) as a possible solution for a fuel nozzle swirler wear application. For the same opportunity, a Cobalt based alloy, L605, was deposited using the high-pressure Cold Spray (CS) system. Detailed characterization of the two additive manufacturing processes (DMLD and Cold spray) was carried out, for porosity, microstructure, phase stability, and structural integrity (bond strength, tensile strength and wear), to assess the suitability of the two different Additive Manufacturing (AM) techniques for addressing the swirler wear problem via new manufacturing technologies. Interfacial chemistry, dilution, heat affected zone and distortion were characterized for the DMLD deposition, while interfacial bonding and wear behaviour were studied for the cold sprayed coating. The fretting wear behavior of both AM processes and materials, was studied, to ascertain the suitability of the cold sprayed coating for wear applications. Detailed characterization and comparison of both the manufacturing technologies led to the DMLD process and maraging steel to be chosen as suitable for repair and restoration of the fuel nozzle swirler in the gas turbine.
Asymmetric Transverse Acoustic Excitation of a Hollow Cone Spray Sheet With Air Swirl
Authors: Bhattacharjee Rohit R. , Babu Aravind I. , Chakravarthy Satyanarayanan R.
Published: January 2020

The objective of this study was to experimentally observe the effects of externally perturbing a hollow cone spray sheet with acoustic excitation. These effects were quantified by measuring changes in the spray breakup length, swirl angle, and oscillatory behaviour of the sheet edge. We used a pressure swirl nozzle embedded into a swirler with 60° vane angles and a geometric swirl no. of SG = 0.981. Water was used to produce a hollow cone spray sheet and air was used as our swirler agent. For asymmetric forcing, only one side of the spray chamber was attached to a transverse duct (aligned perpendicular to the spray axis) along with two speakers. The duct harmonics were found to be 115 Hz, 204 Hz, and 313 Hz. Our experimental modes were also found to be comparable with results obtained numerically using the acoustic solver package from ANSYS. Our results show that for most cases the spray edges, cone angle, and breakup length responds to the acoustic forcing. While the cone angle increased with air swirl, for some cases without acoustic forcing the breakup length increased with air swirl.
Dynamic Characteristics of a Flexible Coupling
Authors: Aggarwal Mohit , Dutt J. K. , Chandraker S.
Published: January 2020

Flexible couplings are used to transmit power between two shafts and accommodate, more realistically, a combination of parallel, axial and angular misalignments, between them. Presence of misalignment of certain degree is considered unavoidable. The coupling also attenuates the transmission of fluctuation of torque and speed from one rotor to the other by flexing itself, and is thus helpful in providing nearly smooth transmission of speed and torque. However, in this process, the dynamic behavior of the rotors is also influenced by the coupling characteristics, as the coupling incorporates a flexible damped intermediate member between the shafts it couples. A detailed literature survey has shown that researchers so far have not attempted to find out the dynamic characteristics, the stiffness and damping of a coupling, and, instead, the effect of misalignment (combination of parallel and angular misalignment) is considered to generate forces independent of the coupling characteristics. This paper attempts to find out an analytical model for the dynamic characteristic of segmented link coupling in terms of suitable non-dimensional coefficients to generate the characteristics of a coupling element which may be used for dynamic analysis of coupled rotor shaft system.
Dynamic Behavior of String Subjected to Travelling Mass
Authors: Jena Shakti P. , Naresh Kumar S. , Cheedella Hemanth
Published: January 2020

The present study is based on the transverse vibration analogy of a string subjected to a travelling mass. The string is considered to be fixed at their both ends. The responses of the string due to the dynamic behavior of the travelling mass are determined using a numerical approach i.e. Green’s function. A Finite Element Model (FEM) has been developed to authenticate the numerical approach. For the responses analysis of the string, numerical example has been illustrated to study the behavior of the string due to the travelling mass and to check the convergence of the two proposed analogies (Green’s function and FEM). The complete analysis has been performed at constant travelling speed and different masses. The two approaches converge well and the Green’s function methodology found to be suitable one.
Design, Fabrication and Analysis of an Electric Ducted Fan
Authors: Vasanthakumar Parthasarathy , Tsering Jigme , Suddunuri Sumanth Siddhartha
Published: January 2020

Driven by rapid development in battery technology and increase in scope for electric air taxi vehicles, developing an efficient combustion free propulsion system to pair with an electric aircraft is crucial for future of aircraft industry. However, with current technology, ducted fan configuration engines are the only feasible option when it comes to combustion free propulsion system which are already being used in many unmanned drones and unmanned aerial vehicles.

In the present work, simple design, analysis and fabrication of ducted fan is performed. Propeller fan and duct is designed using basic principles of blade element theory and momentum theory. Using the parameters from the theoretical design phase, 3D model is made and fabricated using 3D printing and assembled to fit with tolerances suitable for mounting motor. A test stand capable of measuring thrust by varying rpm is designed and built using Arduino based interface. Finally, the designed model is analyzed in Ansys CFX for thrust output using an MRF simulation.