bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermodynamic Modeling and Performance Simulation of Combined Cycle Power Plant Under Design and Off-Design Condition
Authors: Pattanayak Lalatendu , Padhi Biranchi Narayana , Gajjar Hemant 
Published: December 2021

Abstract
Combined cycle power plants (CCPP) are increasingly important for safer and cleaner electricity generation. In this context it is imperative to explore options to enhance its thermal performance for its design and off-design condition. This study presents the performance comparison of two heavy-duty gas turbined (GT) based CCPP with triple pressure steam bottoming cycle. The CCPP system component is modeled using a commercial software Ebsilon and the off-design performance prediction is made using necessary component correlations. The correlations make use of normalized curves that are generated from model runs and apply the factors received from such curve to design performance to estimate the off-design performance. The model simulation is validated against literatures. Furthermore, inlet air cooling technique (IAC) is introduced in this study to enhance the CCPP power production without compromising component performance. The performance comparison of both the CCPP units are presented in an integrated manner by considering interaction of bottoming cycle on GT operation. The results are established as a function of ambient temperature based on energy and exergy principle and the power boosting and economic profit. The results also demonstrate the benefit of IAC on part-load performance. The component level exergy analysis proved that IAC improves the system exergy efficiency.
Numerical Investigation Into the Effects of CoFlow Air on a Self-Excited Helium Jet
Authors: Nayak G Mahesh , B Abinash , B Saravanan , Raju P Satyanarayana 
Published: December 2021

Abstract
A numerical investigation is carried out on a helium jet having Reynolds number 150, and Richardson number 6.11. The effect of air co-flow on a self-excited helium jet is studied in the near field using commercial software ANSYS Fluent V18.1. The co-flow velocity ratio varied in the range of 0.17–0.87. The contours of the helium mole fraction along with the streamlines show the interaction of the toroidal vortex with the jet. The suppression of toroidal vortex is observed as the air co-flow velocity induced to the jet flow. Due to the suppression of vortices, radial spread/diffusion is limited, resulting in large gradients at the shear layer. The flickering frequency increases with the air co-flow. The amplitude of the oscillation at axial locations of higher z/d increases up to a certain co-flow velocity and then drops significantly at high co-flow velocity ratios. However, at upstream (near jet exit plane), oscillation amplitude decrease with increase in air co-flow. The velocity difference in the shear layer to the ambient elucidates the stabilization mechanism of the self-excited helium jet.
Numerical Investigation Into the Effect of Air Swirl on Non-Premixed Combustion
Authors: B Anuj , Nayak G Mahesh , B Yogesh , B Saravanan 
Published: December 2021

Abstract
Endeavour is made to investigate the effect of swirled air on methane-air combustion in a Harwell combustor geometry. The inlet air swirl intensity on combustion characteristics such as temperature, pollutant formation, and flow dynamics is studied. The modeling of turbulent characteristics is performed with the standard K–ε model using ANSYS Fluent. Eddy dissipation model with one step reaction is used for modeling chemical reaction and P-I radiation model for radiation heat transfer. The swirl number is achieved in the range of 0.0 to 0.6, by varying the tangential velocity to the air inlet. With the increase in swirl intensity, the maximum flame temperature drops, and most of the flame formation shifts towards the inlet of the furnace. The change in the flow field is aided by the formation of recirculating bubbles. The swirl causes the flame to spread radially away from the axis, thereby increasing the heat transfer flux to the furnace wall. As a result, a significant reduction in the formation of NO pollutants is observed.
Vaneless Diffuser Performance in a Super-Critical Carbon Dioxide Centrifugal Compressor With Real Gas Effects
Authors: Seshadri Lakshminarayanan , Kumar Pramod 
Published: December 2021

Abstract
Super-critical Carbon dioxide (s-CO2) flows are neither incompressible nor ideal gas flows. Unlike perfect gases, the enthalpy of s-CO2 near the critical point is a strong function of pressure. Incorporation of these effects is necessary for accurate modeling of flows in centrifugal compressor vaneless diffusers. This study reviews the existing vaneless diffuser modeling technique, and modifications are made to incorporate real gas effects. Like the existing procedure, the proposed formulation does not require multiple iterations for convergence. The results are obtained in a single step using a marching technique. Hence, this model can be incorporated in standard centrifugal compressor design and analysis tools, especially for super-critical carbon dioxide flows, subject to experimental validation.
Development of a New Loss Model for Turbomachinery Labyrinth Seals
Authors: Kulkarni Davendu Y. , di Mare Luca 
Published: December 2021

Abstract
The preliminary design of labyrinth seals requires a fast and accurate estimate of the leakage flow. While the conventional bulk flow models can quickly predict labyrinth seal discharge characteristics, they lack the accuracy and pragmatism of modern CFD technique and vice-a-versa. This paper presents a new 1D loss model for straight-through gas labyrinth seals that can provide quick seal leakage flow predictions with CFD-equivalent accuracy.
The present seal loss model is developed using numerical experimentation technique. Multiple CFD computations are conducted on straight-through labyrinth seal geometries for a range of pressure ratios. A distinct post-processing methodology is developed to extract the through-flow stream tube in seal. Total pressure losses and flow area variations experienced by the flow in seal stream-tube are systematically accounted for based on the well-known knife-to-knife (K2K) methodology. Regression analyses are conducted on the trends of variations of loss and area coefficients to derive the independent pressure loss and flow area correlations.
These novel correlations can predict the bulk leakage flow rate, windage flow rate and inter-knife static pressures over a wide range of variation of flow and geometry parameters. Validation study shows that the leakage mass flow rate predicted by this model is accurate within ±8% of measured test data. This fast and accurate model can be employed for various applications such as, in seal design-analysis workflows, for secondary air system (SAS) performance analysis and for the rotor-dynamic and aeroelastic assessments of seals.
Ring Segment Life Improvement Through Hook Gap and Stiffness Optimization
Authors: Gorai Saurabh , Khandelwal Ravi , Das Debdulal , Ahmed Fathi , Radan Radulovic 
Published: December 2021

Abstract
For large gas turbine new make or standard customer value program always aims for higher power and efficiency which calls for an incremental stage loading in terms of higher gas pressure and temperatures distributions for the new upgrade with less ownership costs. To bring down the ownership cost without compromising on the performance or operating hours it becomes important to squeeze and optimize the current design to its maximum limits. This leads to a situation where existing static components fails to meet the MI Strength and Lifing requirements due to change in pressure and temperature.
This paper describes the design challenges and the applied mitigations in the design optimizations of aft stage Ring Segment Hooks and Rails to meet requirements for higher loads at higher performance.
Several sensitivity studies were carried out and transfer functions were developed to bring down the hook loads and hook stresses for steady state max temperature and pressure conditions. Two strategies were adopted to optimize the hook loads. The first is to find the adequate gap between hook and slot and the other one is to vary the hook stiffness by changing the circumferential length.
This paper also presents a systematic approach and check points to decide the optimum gaps and the stiffness of the hooks. For that purpose, a co-relation was developed between hook load and hook to slot gap and the hook circumferential length and hook stiffness.
Design of Duct Passages for an Air Turbine Starter Test Rig
Authors: R Sadham Usean , B. V. S. S. S. Prasad , Dhabade Milind , Kurvinkop Amit , Tatiparthi Vishnuvardhan 
Published: December 2021

Abstract
In a typical air turbine starter (ATS) engine testing application, compressed air is supplied to the turbine by means of an inlet duct usually with a 90 degree bend and discharged from the turbine into the exhaust chimney through a combination of two duct passages. The primary duct is integral to the engine for connecting to the containment ring. The secondary duct is a transition piece for connecting to the exhaust chimney. As these ducts consume additional pressure and adversely affect the performance of the ATS under test. The design of pressure-efficient outlet ducts is therefore essential, and is the topic of present study. The aerodynamic performance of the overall passage depends on the (i) angle of bend, (ii) the shape of the connecting bolt, (iii) the outlet area and shape of the exhaust duct transiting between the bend and the chimney. Combinations of different angular bends, different shaped bolts and varying size of transition pieces are analyzed using the enterprise version of CFD tool, ANSYS. Three dimensional mesh independent simulations using k-epsilon turbulence model are carried out for a combined geometry of inlet duct, rotor-stator combination, outlet ducts together with the bolts. A combination of the duct passages that has resulted in lowest possible pressure drop is suggested as result of the study i.e. the 90 degree bend duct gives 9% pressure difference between inlet and outlet and this might slightly affect the efficiency of the air turbine stator, however the mass flow rate values remains similar to the stator inlet mass flow rate. Hence the 90 degree bend duct is suitable for the test rig. The static pressure loss and total pressure gain is about 0.04% and −0.004% respectively for baseline and aggressive duct of stator and rotor, hence the baseline duct profile is better than aggressive duct. Among different shapes of connecting bolt, the baseline geometry gives slightly lower efficiency of 85.6% when compared to all other models. But due to manufacturing feasibility the baseline geometry is preferred. Exhaust duct model 7 gives pressure drop as 0.062 bar twice the amount of pressure drop in model 6, but it does not affect the efficiency of air turbine starter. The shapes and sizes of the bend, bolts and the transition piece are recommended.
Performance Enhancement of Horizontal Axis Wind Turbine Using Numerical Techniques
Authors: Menon Poornima , G Srinivas 
Published: December 2021

Abstract
Wind turbines are one of the most prominent and popular sources of renewable energy, of which, horizontal axis wind turbines (HAWT) are the majorly chosen design for wind machines. These turbines rotate about the horizontal axis which is parallel to the ground. They comprise of aerodynamic blades (generated from the desired airfoil), that may be twisted or tapered as per the design requirements. The blades are attached to a rotor which is located either upwind or downwind. To help wind the orientation of the turbines, the upwind rotors have a tail vane, while the downwind rotors are coned which in turn help them to self-orient. One of the major reasons for the popularity of the horizontal wind turbine, is its ability to generate a larger amount of electricity for a given amount of wind. Due to its popularity, the enhancement in the design of HAWTs, is a major focus area for research. In the present study, a scaled-down CFD model of the NREL Phase VI was validated against the numerical and experimental data. The model used had a dual blade rotor and applied the S809 airfoil. The simulations were carried out using a rotating mesh in ANSYS Fluent. Validation was carried out for 3 velocities — 7m/s, 10m/s and 20m/s. Once validation was carried out, turbine was modified with the addition of vortex generators, in the form of cylindrical protrusions that reduce flow separation.
Design of Autonomous Unmanned System for Aerial Operations From Underwater Platforms
Authors: Devalla Vindhya , Thomas Cris , Neduncheran Adthithiyan , Capoor Shiv , Mondal Amit Kumar 
Published: December 2021

Abstract
Surveillance and reconnaissance play a very important role in military and civil aspects. They are the key factors in military tactics and in the event of civilian calamities. In case of naval warfare, the submarines which are operating under deep water are required to carry out open land mass surveillance in an efficient manner without reaching to the water surface nor revealing their presence and position. This research paper proposes the conceptualized design to develop an autonomous unmanned octocopter system which is capable of being launched from an underwater platform such as submarines, with the help of a tethered launching mechanism known as octopod, to carry out surveillance, reconnaissance and payload delivery. In this paper, we present a novel method for development of UAV with special application on aerial survey from underwater platforms. A variety of design options which are investigated from various trade studies to evaluate the performance along with design configuration to satisfy the specific requirements are also presented in this paper.
Aerodynamic Performance Evaluation of Axial Flow Fan Using Numerical Techniques
Authors: D. Raghuvaran , Shenoy Satvik , G Srinivas 
Published: December 2021

Abstract
Axial flow fans (AFF) are extensively used in various industrial sectors, usually with flows of low resistance and high mass flow rates. The blades, the hub and the shroud are the three major parts of an AFF. Various kinds of optimisation can be implemented to improve the performance of an AFF. The most common type is found to be geometric optimisation including variation in number of blades, modification in hub and shroud radius, change in angle of attack and blade twist, etc. After validation of simulation model and carrying out a grid independence test, parametric analysis was done on an 11-bladed AFF with a shroud of uniform radius using ANSYS Fluent. The rotational speed of the fan and the velocity at fan inlet were the primary variables of the study. The variation in outlet mass flow rate and total pressure was studied for both compressible and incompressible ambient flows. Relation of mass flow rate and total pressure with inlet velocity is observed to be linear and exponential respectively. On the other hand, mass flow rate and total pressure have nearly linear relationship with rotational speed. A comparison of several different axial flow tracks with the baseline case fills one of the research gaps.
Investigations on Structural Integrity of Piping Compensators Under Angular Rotational Deformation
Authors: Pagar Nitin D. , Sanap Sudarshan B. 
Published: December 2021

Abstract
The aim of this paper is to investigate the effect of angular rotational misalignment in pipe structure on the deflection based convolution stresses. Such stresses are generated in the thin walled unreinforced bellows compensators during the expansion-contraction function. On the convolution geometry, the most vulnerable stress type is meridional deflection stresses under the internal pressure. Therefore, it’s critical to check the structural integrity of pipe systems with bellows expansion joints, which typically connected to the process equipment’s including boilers, pressure vessels, reactors, heat exchangers, refineries, and so on. The findings of theoretical and experimental investigations of thin-walled unreinforced conditioned bellows subjected to different angular rotations are presented in this paper. The meridional deflection stresses are investigated for the different operating pressures when bellows subjected to angular rotations of 1°, 1.5° and 2° in the flexural plane. In addition, the testing is performed along various longitudinal lines across the periphery of the bellows to determine the maximum induced stress points on the convolution profile. The higher meridional stress is seen to be the bending stress at the bottom curved toroidal section of the convolution, which approaches towards the elastoplastic regime at 1° to 2° of angular deviation in flexural plane. These extreme stress points may prove the risky areas at the root of the convolution for the fatigue failures. Further, the results of the maximal convolution stress assessment are useful in predicting the structural integrity of bellows in elastic regime, when prone to the angular shift.
Plate tectonics and macrogeomorphology
Authors: Summerfield Michael A. 
Published: December 2021

Abstract
The plate tectonics revolution was the most significant advance in our understanding of the Earth in the twentieth century, but initially it had little impact on the discipline of geomorphology. Topography and landscape development were not considered to be important phenomena that deserved attention from the broader Earth-science community in the context of the new model of global tectonics. This situation began to change from the 1980s as various technical innovations enabled landscape evolution to be modelled numerically at the regional to subcontinental scales relevant to plate tectonics, and rates of denudation to be quantified over geological timescales. These developments prompted interest amongst Earth scientists from fields such as geophysics, geochemistry and geochronology in understanding the evolution of topography, the role of denudation in influencing patterns of crustal deformation, and the interactions between tectonics and surface processes. This trend was well established by the end of the century, and has become even more significant up to the present. In this chapter I review these developments and illustrate how plate tectonics has been related to landscape development, especially in the context of collisional orogens and passive continental margins. I also demonstrate how technical innovations have been pivotal to the expanding interest in macroscale landscape development in the era of plate tectonics, and to the significant enhancement of the status of the discipline of geomorphology in the Earth sciences over recent decades.
Tadalafil Enhances Immune Signatures in Response to Neoadjuvant Nivolumab in Resectable Head and Neck Squamous Cell Carcinoma
Authors: Luginbuhl Adam J. , Johnson Jennifer M. , Harshyne Larry A. , Linnenbach Alban J. , Shukla Sanket K. , Alnemri Angela , Kumar Gaurav , Cognetti David M. , Curry Joseph M. , Kotlov Nikita , Antysheva Zoya , Degryse Sandrine , Mannion Kyle , Gibson Michael K. , Netterville James , Brown Brandee , Axelrod Rita , Zinner Ralph , Tuluc Madalina , Gargano Stacey , Leiby Benjamin E. , Shimada Ayako , Mahoney My G. , Martinez-Outschoorn Ubaldo , Rodeck Ulrich , Kim Young J. , South Andrew P. , Argiris Athanassios 
Published: December 2021

Abstract

Purpose:
We hypothesize that the addition of the phosphodiesterase-5 inhibitor tadalafil to the PD-1 inhibitor nivolumab, is safe and will augment immune-mediated antitumor responses in previously untreated squamous cell carcinoma of the head and neck (HNSCC).

Patients and Methods:
We conducted a two-arm multi-institutional neoadjuvant randomized trial in any-stage resectable HNSCC (NCT03238365). Patients were stratified at randomization by human papillomavirus (HPV) status. Patients in both arms received nivolumab 240 mg intravenously on days 1 and 15 followed by surgery on day 28. Those in the combination therapy arm also received tadalafil 10 mg orally once daily for 4 weeks. Imaging, blood, and tumor were obtained pretreatment and posttreatment for correlative analysis.

Results:
Neoadjuvant therapy was well-tolerated with no grade 3 to 5 adverse events and no surgical delays. Twenty-five of 46 (54%) evaluable patients had a pathologic treatment response of ≥20%, including three (7%) patients with a complete pathologic response. Regardless of HPV status, tumor proliferation rate was a negative predictor of response. A strong pretreatment T-cell signature in the HPV-negative cohort was a predictor of response. Tadalafil altered the immune microenvironment, as evidenced by transcriptome data identifying enriched B- and natural killer cell gene sets in the tumor and augmented effector T cells in the periphery.

Conclusions:
Preoperative nivolumab ± tadalafil is safe in HNSCC and results in more than 50% of the patients having a pathologic treatment response of at least 20% after 4 weeks of treatment. Pretreatment specimens identified HPV status-dependent signatures that predicted response to immunotherapy while posttreatment specimens showed augmentation of the immune microenvironment with the addition of tadalafil.
A Brazilian Perspective on Audiobooks
Authors: de Oliveira Barbosa Rafael 
Published: December 2021

Abstract
This paper presents a Brazilian perspective on audiobooks. It contextualizes the past and current realities of the format in the country, on the basis of surveys coordinated by national associations connected to the book market and of archival research we have undertaken, and shows some examples of recorded literary works and recent initiatives in audiobook production. The ‘acoustic-editorial project’ idea is proposed as a way to highlight and deepen the materiality and production process of audiobooks, and to understand the editorial elements through which the listening experience is created. Authors from book history, bibliography, communication theory, and audiobook studies influenced this investigation and strengthened our construction of audiobooks as a research object.
Decadal Variability of the Upper-Ocean Salinity in the Southeast Indian Ocean: Role of Local Ocean–Atmosphere Dynamics
Authors: Wu Yue , Zheng Xiao-Tong , Sun Qi-Wei , Zhang Yu , Du Yan , Liu Lin 
Published: December 2021

AbstractOcean salinity plays a crucial role in the upper-ocean stratification and local marine ecosystem. This study reveals that ocean salinity presents notable decadal variability in upper 200 m over the southeast Indian Ocean (SEIO). Previous studies linked this salinity variability with precipitation anomalies over the Indo-Pacific region modulated by the tropical Pacific decadal variability. Here we conduct a quantitative salinity budget analysis and show that, in contrast, oceanic advection, especially the anomalous meridional advection, plays a dominant role in modulating the SEIO salinity on the decadal time scale. The anomalous meridional advection is mainly associated with a zonal dipole pattern of sea level anomaly (SLA) in the south Indian Ocean (SIO). Specifically, positive and negative SLAs in the east and west of the SIO correspond to anomalous southward oceanic current, which transports much fresher seawater from the warm pool into the SEIO and thereby decreases the local upper-ocean salinity, and vice versa. Further investigation reveals that the local anomalous wind stress curl associated with tropical Pacific forcing is responsible for generating the sea level dipole pattern via oceanic Rossby wave adjustment on decadal time scale. This study highlights that the local ocean–atmosphere dynamical adjustment is critical for the decadal salinity variability in the SEIO.