bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.
Sensitivity of Cascade Pressure Distribution for Inverse Design of Turbine Blade
Authors: Nanthini R. , Prasad B. V. S. S. S. , Sanyasiraju Y. V. S. S. 
Published: January 2020

Abstract
In an iterative inverse design of a turbine blade, choice of initial guess profile is crucial. As the pressure distribution is very sensitive to the leading and trailing edge shapes and the profile slope and curvature, a good initial guess profile will help in faster convergence. In this paper, the sensitivity of the pressure distribution is determined by carrying out numerical simulations with ANSYS Fluent 17.2 for the inviscid flow. The flow domain comprises of a two dimensional transonic turbine cascade. It consists of a turbine blade enclosed by inlet, outlet and periodic boundaries. Inlet total pressure, total temperature and inlet angle are given as the boundary conditions at the inlet and static pressure is imposed at the outlet boundary. The flow is solved for continuity, momentum and energy equations. Sensitivity of different parameters — leading edge thickness, trailing edge thickness, leading edge shape, inlet and outlet wedge angle on the pressure distribution is demonstrated for VKI blade cascade. It is found that the pressure side of the profile is less sensitive and that even a small variation in suction side of the profile geometry can affect the performance of the blade significantly. It is shown that, with the proposed methodology and sequence of steps, the final guess blade is quite close to the original blade.
Analysis of Aerostatic Thrust Bearing for S-CO2 Turbomachinery
Authors: Patel Ashutosh , K. Balasubramanian Aanand , Biradar Vijay , Srivatsa Shreyas , Kumar Pramod , Sonti Venkata R. 
Published: January 2020

Abstract
Preliminary analysis for the S-CO2 Brayton power cycle development suggests small size and high operating speed of turbomachinery. The axial thrust due to the pressure differential generated in the turbomachinery is transferred to the bearing through the shaft. Angular contact ceramic bearings used for high speed operations are incapable of withstanding high axial loads.
The current paper presents, theoretical and computational analysis of a 4-hole aerostatic thrust bearing for S-CO2 turbomachinery applications. CFD analysis is performed for different axial clearance gap between stationary and rotating discs of the thrust bearing. The computations have been performed for two different fluids — air and CO2. This computational domain of the flow regime splits into two regions: adiabatic flow through the orifice and isothermal flow in the clearance volume comprising the clearance gap. The influence of the following parameters such as, pressure distribution across thrust pad area, mass flow rate, load capacity and the local velocity in the gap on the stiffness of the bearing are investigated.