bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative Analysis of Propulsive System in Multi-Rotor Unmanned Aerial Vehicle
Authors: Sonaimuthu Balaji , Panchalingam Prabhagaran , Raja Vijayanandh 
Published: January 2020

Abstract
In an advanced Multi-rotor Unmanned Aerial Vehicle (UAV), the existing methodology of the propeller and its parametric modification leads to provide the various performance characteristics by inducing the operating efficiency. The subsisting solution for obtaining the thrust, rate of climb and forward speed by proliferating the propeller configuration and modification the design aspects in propeller by varying the pitch angle and consisting parameters in a Multi-rotor UAV. Instead of adding or modifying the design aspects, this article recommends the propeller with attaching Convergent-Divergent (C-D) Nozzle duct, which leads to producing the augmented thrust efficiency than the normal functioning system. And the comparison of the propeller with and without attaching the convergent nozzle duct, divergent nozzle duct, C-D nozzle duct has been analyzed using the numerical simulation and scrutinizing the optimized conceptual design of propeller is done with the help of ANSYS Workbench, where the design methodology is modeled by CATIA. By the result of the simulation, it leads to provide the efficient characteristics and design aspects of the Multi-rotor Unmanned Aerial Vehicle.
Performance Simulation of an Engine Retrofitted With Thrust Vectoring Capabilities
Authors: Sundararaj Ramraj H. , Chandra sekar T. , Arora Rajat , Rao A. N. , Kushari Abhijit 
Published: January 2020

Abstract
Thrust vectoring is a requirement for fifth generation fighters, giving them super-maneuverability capabilities, allowing them to execute tactical maneuvers that are not possible using conventional aerodynamic mechanisms. The most widely used and successful method for achieving this is by using gimbaled engines or nozzles. The complexities involved in this method, have encouraged future engine designers to explore different avenues for achieving thrust vectoring, one of which is fluidic thrust vectoring. In fluidic thrust vectoring, jet deflection is achieved by fluid injection at various locations on the nozzle.
During thrust vectoring operations, the engine performance is affected. This is primarily due to the change in effective nozzle area. When a nozzle is gimbaled, as is the method used in currently operational thrust vectored engines, or during fluidic thrust vectoring operations, there is a change in effective nozzle area. This impacts the engine mass flow rate, thus affecting the engine operation. The change in performance is similar to that of an engine fitted with a variable area nozzle.
In this study, we attempted to retrofit a thrust vectoring nozzle to an existing engine designed for a fourth-generation fighter aircraft, in order to give it fifth-generation fighter aircraft capabilities. A Twin spool mixed flow turbofan engine with a convergent nozzle is selected and its performance is simulated using Gasturb 13. The baseline engine consists of a low pressure spool, high pressure spool, combustion chamber and convergent-divergent nozzle. For the sake of simplicity, the convergent-divergent nozzle is replaced with a convergent nozzle, with no loss in thrust at design point. The design point is arrived at based on engine data available in open literature. Following this, offdesign performance is simulated, for studying the effect of thrust vectoring operations, which are modeled as a nozzle area change. Suitably scaled generic maps provided in Gasturb are used for off-design simulations. The effect of nozzle area change on engine performance is studied at sea level static conditions. The nozzle area is decreased by a maximum of 15%, in steps of 1%. During thrust vectoring operations, there is a significant change in bypass ratio and fan surge margin, with the other performance parameters being relatively constant.
Following this, simulations are conducted at different flight conditions to understand the effect of nozzle area change for different flight regimes. A total of seven different flight conditions are selected to understand the operational envelope of thrust vectoring operation. It is found that at all flight conditions, thrust vectoring has a significant influence on bypass ratio and fan surge margin. While for most conditions, there is an improvement in fan surge margin, there are two conditions where fan surge margin decreases substantially.
Comparative Assessment of Savonius Water Turbine With Conventional Savonius Wind Turbine
Authors: Sarma Neelam K. , Biswas Agnimitra , Misra Rahul D. 
Published: January 2020

Abstract
Wind turbine has gained a keen interest in the field of research but its low efficiency due to low working fluid density triggers the need for upgradation. However, this technology will get a boost if the factor of low density fluid is eradicated. This paper is intended towards the study of performance of the same design of Savonius wind turbine when operated in high density water. The density of water is approximately 1000 times more than air. In the present study, the performance of a two bladed Savonius wind turbine and a Savonius water turbine have been analyzed both experimentally and with the aid of Computational Fluid Dynamics (CFD) using Ansys 19.0, keeping the maximum power content (Pmax) of the fluid-stream constant. Coefficient of power (Cp) is one of the deciding factors for superiority of the turbines one over the other. For the study, three cases of power contents viz. 0.61 W, 6.2 W and 16.45 W have been considered. The results obtained suggest that the Savonius water turbine with the highest Cp value of 0.343 is dominant over Savonius wind turbine. The effects of tip speed ratio and Non-dimensional factor (γ) on performance of both the turbine kinds have also been studied.
Combustor Modeling and Design Modification of a Micro Gas Turbine Combustor With a Rotating Casing for Syngas Fuel
Authors: Shih Hsin-Yi , Ajvad Maaz 
Published: January 2020

Abstract
This study is an extension of the previous study, which presents the rotation effects of casing on syngas combustion. When syngas was applied to achieve the power output of proposed micro gas turbine, high temperature flame moves towards the exit of the combustor. Consequently, the temperature and temperature fluctuation at combustor exit increases. In this study, geometry of the can combustor is modified for the syngas application. In modified design, diameter of the fuel injector, length of the primary zone, configuration of primary and dilution holes is modified. To perform the numerical calculation, computational model which consists of three-dimension compressible k-ε realizable turbulent flow model and presumed probability density function for combustion process invoking a laminar flamelet assumption generated by detailed chemical kinetics from GRI 3.0 is used. Two typical composition of syngas are used namely: H2-rich (H2:CO = 80:20) and equal molar (H2:CO = 50:50). The combustion characteristics and NOx emissions were investigated to understand the rotating effects of syngas combustion in the modified design of the can combustor. In the modified design, the high-temperature flame gets stabilized along the wall of the combustor for both composition of syngas. Unlike in the previous design, the high-temperature flame moves towards the exit of the combustor. The exit temperature and pattern factor dropped and reached the design requirements after the modification. The rotation of casing enhances the swirling strength, which benefits proper mixing of fuel and air and leads to reduction in pattern factor and NOx emissions.
Supercritical Carbon Dioxide Turbomachinery Options for Kilowatt to Gigawatt Level Power Generation
Authors: Seshadri Lakshminarayanan , Raja Harini Nivetha , Kumar Pramod , Nassar Abdul , Giri Gaurav , Moroz Leonid 
Published: January 2020

Abstract
Supercritical Carbon Dioxide Brayton cycles can be used in conjunction with a host of heat sources associated with different magnitudes of net power generation. In this paper, the overall design features of the turbomachinery, namely the turbine and compressor are evaluated for kilowatt to Gigawatt range of net cycle power using a commercial design tool — AxSTREAM®. The thermodynamic cycle considered in all cases is a simple recuperated Brayton cycle with turbine and compressor inlet temperatures of 540 °C and 45 °C respectively. The highest and lowest pressures in the cycle are 210 bar and 85 bar respectively. The preliminary design is carried out using an inverse algorithm with a meanline solver that generates many geometries for the given boundary conditions using standard loss correlations to account for different losses in turbomachines. It, thus, provides the general design features of the compressor and turbine which include — machine size, shaft speed at design point, overall efficiency, number of blades, blade heights, blade angles and number of stages for axial turbines. The choice of axial or radial impeller and initial estimates of machine size and shaft speed are made based on standard specific speed-specific diameter charts and important loss parameters are presented for each case. This study serves as a first step towards in-depth blade profiling, 3-D analysis and design of the turbomachinery required to bring this technology to the practical realm.
Conjugate Heat Transfer Analysis of Military Aero Engine Combustor Liner With Impingement and Effusion Cooling
Authors: Suresh Batchu , Panigrahi Chinmayee , Davis Antonio , Kesavan V. , Kishore Prasad D. 
Published: January 2020

Abstract
Improvement in specific thrust is one of the desirable requirements for Military aero-engine which has led to a tremendous increase in turbine inlet temperatures. This has resulted in combustion chambers to operate at a gas temperature of the order of 2100K, making it difficult for the thermal designers to design a liner cooling configuration to bring down its metal temperature within allowable limits with available coolant air. The present study highlights the computational prediction of cooling effectiveness for impingement-effusion cooled combustor liner. The impingement cooling is adopted to the effusion cooled liner in order to enhance its coolant side heat transfer. 1-Dimensional (1-D) analysis is carried out to obtain a suitable impingement geometry to improve the coolant side heat transfer. Suitable geometrical features like impingement hole diameter (di) and distance of the impingement plate from effusion liner (z) are arrived for enhancement of coolant side heat transfer. Conjugate Heat Transfer analysis (CHT) is carried out for three cooling configurations with different impingement hole diameter. Effusion cooled liner with porosity 1% and holes inclined at 22° and for impingement plate hole porosity of 1.6% is maintained for all the configurations. CHT analysis is carried out for effusion cooled liner using ANSYS Fluent ver.14.5. The film cooling predictions are in good agreement for effusion cooled liner plate with measurements. SST k-ω turbulence model with enhanced wall function predicted well. The effectiveness obtained for effusion cooled liner and impingement-effusion cooled liner are compared. There is an improvement of 34% in effectiveness for impingement-effusion cooled liner compared to effusion cooled liner with a reduction of coolant air mass flow by 10%. The variation of temperature for the impingement-effusion cooled liner is lower. Parametric analysis is also carried out to study the effect of blowing ratio and metal thermal conductivity on the film cooling effectiveness for impingement-effusion cooled liner.
Accurate Prediction of Buffer Air Temperatures Using Lumped Heat Transfer Method
Authors: Gandla Pavan , Nidamanuri Naresh 
Published: January 2020

Abstract
Buffer air system plays a vital role in gas turbine engines as it pressurizes bearing compartments, thermal conditioning of life limiting parts, purging the hot gas ingestion and antiicing. Buffer air is normally tapped from compressor section and routed to several locations of the engine through tubes, struts and ducts. Air supply is controlled though a buffer valve which sources air from different sources based on the flight condition. Accurate prediction of steady state buffer air temperature is critical in achieving gas turbine performance, durability and operability. It allows design community to determine optimum amount of buffer air which directly impacts gas turbine efficiency. As buffer air passes through different section of the engine by the time it reaches its intended destination, it losses or gains heat which eventually alter its temperature. Buffer air is currently modelled through a network of chambers and restrictors which is solved through an iterative solver for flow and energy convergence. Heat transfer is neglected in this solver and captures only enthalpy balance and pressure losses.
An effort has been made to capture buffer air convective heat transfer as it passes through many channels and ducts on its routing. Lumped heat transfer method is employed and estimated the delta temperature b/w inlet and outlet of the corresponding passage. Outside and inside heat transfer coefficients are estimated using empirical correlations. Under steady state conditions, Final temperature of the buffer air would be the surrounding air temperature at that location and initial temperature of the air is its entry temperature. This delta temperate is incorporated in the buffer air network which then predicts corrected buffer air temperature for any flight conditions.
With this methodology predicted buffer air Temperature is matched very close to thermo couple test data for various engine power conditions. Buffer air network model fidelity is greatly improved and gives greater confidence on air temperature for any flight conditions.
Design studies are carried out and made a recommendation to incorporate thermal barrier coating on passages so that buffer temperature is retained which improves its thermal conditioning capabilities.
Modeling Combustion in a Rearward-Facing Step Using a Hybrid RANS/LES Method
Authors: Verma Ishan , Yadav Rakesh , Nakod Pravin , Sharkey Patrick , Li Shaoping , Meeks Ellen 
Published: January 2020

Abstract
With incremental High-Performance Computing (HPC) scalability and performance improvements, hybrid Reynolds Averaged Navier Stokes (RANS)/Large Eddy Simulation (LES) have become popular for modeling reactive flow configurations. Hybrid RANS/LES methods like Stress-Blended Eddy Simulation (SBES) are presented in this paper and have been applied to model near-wall flows using two-equation k-ω RANS formulation while switching to LES in the separated flow region using a blending function. Turbulent combustion in a rearward-facing step is modeled by using Flamelet Generated Manifold (FGM) with SBES turbulence. A turbulent premixed propane/air flame (φ = 0.57) is stabilized in the turbulent mixing layer (ReH = 22, 100) formed at the rearward-facing step. The results obtained show a good agreement with the experimental data for velocity, temperature and species mass fractions at various locations in the channel.
Flamelet Generated Manifold Simulation of Turbulent Non-Premixed Bluff Body Flames
Authors: Verma Ishan , Yadav Rakesh , Nakod Pravin , Sharkey Patrick , Li Shaoping , Meeks Ellen 
Published: January 2020

Abstract
In this paper, the turbulent jet diffusion flame stabilized behind a bluff body (HM1) is simulated using the Flamelet Generated Manifold (FGM) model. Interactions between turbulence and chemistry are detailed in this paper. In HM1 flame, ignition mainly occurs in the outer shear layer while mixing effects dominate in the recirculation zone. Turbulence is modeled by using variants of two-equation Reynolds Averaged Navier Stokes (RANS) models (steady and unsteady RANS), whilst turbulence-chemistry closure is based on FGM approach. Results are compared with experimental data to validate the dynamics and spatial structure of bluff-body flames. Different approaches based on the variants of steady RANS and unsteady RANS are compared for three mesh resolutions. Definitive advantages and disadvantages of each approach are identified on the basis of computational cost and accuracy. The results provide important insights into the simulation of bluff-body flames approaching the blow-off limit.
A Comparative Study of Heat Transfer Characteristics and Pressure Drop in Matrix Structures
Authors: Prajapati Anjana N. , Tariq Andallib 
Published: January 2020

Abstract
An experimental study on local heat transfer distributions and pressure loss in the closed matrix channels with an angle 45° has been conducted using liquid crystal thermography for a Reynolds number (Re) range 5800–14000. A total of five different configurations of matrixes have been considered for investigation. The thermo-hydraulic performance of the matrix structure with angle 45° is initially compared with that of the matrixes with angles 35° and 55° for a constant sub-channel aspect ratio (ARs) 0.8. Later, the sub-channel aspect ratio of matrix with angle 45° has been varied as 0.4 and 1.2 and the comparative results are presented. While comparing the performance parameters of different angles for the sub-channel aspect ratio 0.8, it is found that for lower Reynolds numbers (Re ≤ 8100), the angle 45° offers highest augmentation Nusselt number. However, for Re &gt; 8100, the angle 55° showed the highest augmentation Nusselt number. It has been also observed that the sub-channel aspect ratio 0.8 presents the highest augmentation Nusselt numbers as compared to ARs = 1.2 and 0.4 for Re ≤ 12400. Whereas, the friction factor fairly decreases with the increase in the sub-aspect ratio. A significant effect of angle has been found for friction factor as compared to sub-channel aspect ratio. The highest thermal performance factor (1.13) is obtained for the matrix with angle 45° and sub-channel aspect ratio 0.8 at Reynolds number 8100.
Characterization of Burner Stabilized Premixed and Non-Premixed Flame Using Digital Image Processing
Authors: Hassan Tarik , Sarkar Sourav , Mukhopadhyay Achintya , Sen Swarnendu 
Published: January 2020

Abstract
The present goal of combustion research is to enhance the burning efficiency resulting in minimal emission which is in fact, paves the way for a sustainable future. Researchers are investigating different parameters and factors associated with combustion to control the combustion process. Image processing is one of the most useful and safe tool for this job as it is nonintrusive and do not interfere with the combustion zone during experiment. Present work focuses on the digital image processing of the premixed and diffusion flame which has been utilized as a tool to characterize burner stabilized premixed and non-premixed Flame. The experiment is performed on a burner stabilized LPG-air flame. For premixed flame, several sets of experiments are done keeping the camera setting and image quality identical which resulted in an almost linearly increasing average RGB value with respect to equivalence ratio. Taking the relation of an experiment as standard, equivalence ratio is calculated for other experiments just by observing the average RGB value(R+G+B/3) of that image. It is found that almost in all cases the error values are lying between −10% to +10% of the actual value calculated from the flow rates of air and fuel. Diffusion flame is examined by passing fuel through the central channel of co-flow burner and air through the outer cylindrical channel. Air is used to stabilize the flame and for giving it a steady shape. Experiment is done keeping air flow constant while the fuel flow is varied and the image is captured. For diffusion flame, as the change in colour of flame is not much differentiable with the change in fuel, analysis is done to find the relation between fuel flow rate and flame area by counting the number of pixels. Finally, a direct relation of fuel amount and the image area is obtained.
Performance Evaluation of Contra-Rotating Fans Operating Under Different Speed Combinations
Authors: Joshi Navjot , Madasseri Payyappalli Manas , Pradeep A. M. 
Published: January 2020

Abstract
One of the advantages of a contra-rotating fan is its possibility to operate both the rotors at different speeds. Owing to this possibility, the performance of a contra-rotating fan can be controlled by operating it at different speed combinations. A numerical study of a low aspect ratio contra-rotating fan in low subsonic regime is carried out under various speed combinations of the rotors. Both steady state and Nonlinear Harmonic (NLH) simulations are performed to identify the important flow mechanisms in the contra-rotating fan. The results show that the diffusion factor of rotor-2 is significantly high towards the hub region which implies that large separations are likely to occur at the hub. The wake of rotor-1 is observed to impinge on the suction surface of rotor-2. Rotor-2 generates a strong suction effect at high rotational speeds and thereby delays the stall inception in the whole stage and shows an improvement in the stage pressure ratio. The upstream effect strongly influences the performance of rotor-1. When rotor-2 rotates at higher rotational speed, due to the suction effect, the flow angle at the exit of rotor-1 decreases which allows the fan to operate at lower flow coefficient. When the suction effect is very strong, it pulls the tip leakage vortex of rotor-1 towards the axial direction. Due to the suction effect, the location of the appearance of tip-leakage vortex moves further downstream. The tip-leakage vortex makes a higher angle with the blade chord at near stall conditions for speed combination Nd – 1.5Nd in contrast to a lower angle for speed combination Nd – 0.5Nd. In summary, the paper describes the performance changes, flow physics and the rotor-rotor interaction mechanisms for different speed combinations of a contra-rotating fan.
Impact of Sweep on Part Speed Performance of an Axial Compressor Rotor With Circumferential Casing Grooves
Authors: Goswami Shraman , Govardhan M. 
Published: January 2020

Abstract
High performance and increased operating range of an axial compressor is obtained by employing three-dimensional design features, such as sweep, as well as shroud casing treatments, such as circumferential casing grooves. A number of different rotor blades with different amounts of sweeps and different sweep starting spans are studied at design speed. Different swept rotors, including zero sweep, are derived from Rotor37 rotor geometry. In the current study the best performing rotor with sweep is analyzed at part speed. The analyses were done for baseline rotor, devoid of any sweep, and with and without circumferential casing grooves. A detailed flow field investigation and performance comparison is presented to understand the changes in flow field at part speed. It is found that that at 100% design speed, stall margin improvement is achived by both sweep and casing grooves, but at 90% speed improvement in stall margin due to sacing groove is very minimal over and above the gain due to sweep. It is also noticed that due to reduced shock loss efficiency is higher at 90% speed than at 100% speed.