bluuebunny/crossref_metadata_2025 huggingface dataset:
MBSE Model on Gas Turbine Tip Clearance Control
Authors: Kulkarni Guruprasad , Price Sebastian
Published: January 2020

Model Based System Engineering (MBSE) is a systems engineering methodology to understand the customer needs and create functional model to capture requirements and develop design definitions. This paper represents the MBSE activity carried out on Turbine Tip Clearance Control (TCC) System for a Trent XWB Engine. TCC is a critical system of an Aircraft engine, whose function is vital throughout the engine life. This is a complex system as both mechanical and control systems need to interact seamlessly to meet its operational requirement. The key accomplishment of this study is, abstracting of complex mechanical system into functional model and connecting it to functional model of Controls in MBSE environment. This is done for a system that meets the standards of very safety critical and highly regulated industry of Civil Aircraft Engines.

The software used for building requirements models for TCC is Capella. Capella is open source free software built on Architecture Analysis and Design Integrated Approach (Arcadia) frame work. This framework extends and simplifies SysML. The advantages of this frame work over SysML are explained in [Ref. 1]. The Arcadia frame work is well suited to capture the complex systems involving multiple disciplines along with Mechanical systems as explained in [Ref. 2].

This paper presents a detailed study performed on product system level requirements and captures both functional and non-functional requirements such as operational and safety requirements. In the Arcadia framework this is represented at system analysis level. Further studies capture the logical and physical architecture which is representative in nature.
Automatized 3D-Scanning Application for the Virtualization of Large Components
Authors: Mönchinger Stephan , Schmidt Marvin M. , Dreßen Sebastian , Wissmann Patrick , Stark Rainer
Published: January 2020

Many of the large components of modern gas turbines are cast, resulting in rough surface profiles, which have to be machined to achieve the component’s final state. As there are high deviations in casting components, the real geometry does not meet the ideal model dimensions and is known neither to the supplier nor to the customer. While manual 3D-scanning processes, heavily depending on the operator’s qualification, get more attention, conventional means are still the basis for quality assurance of such parts.

Although significant time reduction can be reached by automated scanning, there is still a low variety of corresponding applications for large components on the market. Flexible systems are an approach for further development as most of the manufacturers handling large components already have and use machine tools for the processing of their components.

The designed and implemented prototypical system allows the acquisition of a large component’s surface with only a few manual inputs prior to the actual scanning procedure. It can be used with existing machining tools, allowing an easy implementation for different use cases of a pre-manufacturing scan, e.g. for CAM planning. The application is implemented in a small software tool that can be adapted to other machines with low effort. The implementation has been demonstrated in a real manufacturing environment with typical environmental conditions in the shop floor. The prototypical application has been built mainly with existing components.

Following the V-Model, each domain has been investigated individually followed by a complete system investigation. With a system price below 100.000€ the price is below 10% of most automated systems on the market. The presented cost efficient, low complexity prototypical system can provide early information about the product for a digital process chain in industry 4.0, enabling flexible, intuitive and easy integration.
Estimation of the Influence of the Inlet Nonuniformity on the Performance of a Fan of a Turbofan Engine
Authors: Popov Grigorii M. , Baturin Oleg V. , Novikova Yulia D. , Zubanov Vasilii M. , Volkov Andrei A.
Published: January 2020

The paper presents the results of numerical simulation of the effect of flow nonuniformities at the engine inlet on the working process of the engine fan. Flow nonuniformities is created by pushing the interceptor into the flow path of inlet device like as it is often done during field tests. The authors have created a numerical model capable of considering non-stationary processes in the fan using nonlinear harmonic analysis. As a result, qualitative and quantitative estimates were obtained of the influence of overlapping of the inlet duct by the interceptor on the main parameters of the fan workflow. It is shown that the more the duct is blocked, the more its parameters are deteriorated. Moreover, the deterioration is not linear, but according to the dependence of the 2nd order.
Parametric Studies on Gas Turbine Labyrinth Seal for the Secondary Air Flow Optimization at Static and Rotating Conditions
Authors: Raja Kaliraj Karthick , Yepuri Giridhara Babu , Janardanan Sarasamma Jayakumar , Kumar Kishor , Jesuraj Felix
Published: January 2020

Various studies have been carried out related to the labyrinth seals and reported in the open literature using the different seal arrangements at the stator-rotor seal cavity region. In the present study, numerical analysis has been carried out for the static and rotational effects of labyrinth seals at various flow and geometrical, parametric conditions for the optimized leak flow using straight and steeped seal configurations. And, an experimental data has been generated for the straight through seals, and the numerical data of the same case is validated with the experimental data. The k-omega SST turbulence model is considered with 5% turbulence intensity for the CFD analysis. At a particular seal clearance, as the number of teeth increases the leakage flow is found to be decreased. The leak flow is found to be lower with the stepped labyrinth seals in comparison to the straight through seals. The leak flow amount is found to be lower at a rotational condition in comparison to the stationary condition. From the overall results, it is observed that the stepped seal with a lower clearance at a compressor bleed air temperature and rotational conditions have shown better performance with the lower leak air mass flow.
Modified Brayton Cycle for Turbofans
Authors: Singhal Chirag , Hasan Sameer , Baig M. F.
Published: January 2020

In the present study, a design point analysis of twin-spool turbofan engines is carried out, considering fuel injection of Aviation Turbine Fuel (ATF) in the initial stages of the compressor instead of combustor The two-phase compression brings about intercooling in the modified Brayton cycle, by injecting the atomized fuel directly in the initial stages of axial-flow compressor. The intercooling effect results in reduction of compressor work while reinforcing the enthalpy of combustion of fuel due to change of state of fuel from liquid to vapor state. This brings about an improvement in the thrust and thermal efficiency of the modified cycle. Effect of the intercooling is investigated for different performance parameters namely Fuel flow rate ṁf Total thrust Fs, Thermal efficiency ηth, Overall efficiency ηo and Modified cycle factor MCF over the varying compressor pressure ratio (CPR).

Injecting the fuel in the 2nd stage of compression results in percentage increase of total thrust by 21.14%, MCF by 31.35%, ηo by 14.92% and decrease in Fuel flow rate ṁf by 7%. While injecting the fuel in the 5th stage of compression results in increased ηo by 17.54 %, MCF by 37.30%, total thrust by 5.68% and decrease in Fuel flow rate ṁf by 22% at a CPR = 30 and Turbine Inlet Temperature (TIT) = 1260K vis-à-vis conventional cycle. Injecting the fuel in latter stages of compressor brings about a decrease of total thrust as well as efficiency.
Effect of Process Parameters on Laser Directed Energy Deposition of Copper
Authors: Yadav Sunil , Paul Christ P. , Jinoop Arackal N. , Nayak Saurav K. , Rai Arun K. , Bindra Kushvinder S.
Published: January 2020

Laser Additive Manufacturing (LAM) is an advanced manufacturing processes for fabricating engineering components directly from CAD Model by depositing material in a layer by layer fashion using lasers. LAM is being widely deployed in various sectors such as power, aerospace, automotive etc. for fabricating complex shaped and customized components. One of the most commonly used LAM process is Directed Energy Deposition (LAM-DED) which is used for manufacturing near net shaped components with tailored microstructure, multi-materials (direct and graded) and complex geometry. This paper reports experimental investigation of LAM of Copper (Cu) tracks on Stainless Steel 304 L (SS 304L) using an indigenously developed LAM-DED system. Cu-SS304L joints find wider applications in tooling, automotive and aerospace sectors due to its combination of higher strength, thermal conductivity and corrosion resistance. However, laying Cu layers on SS304L is not trivial due to large difference in the thermo-physical properties. Thus, a comprehensive experiments using full factorial design are carried out and a number of Cu tracks were laid on SS304L substrate by varying laser power, scan speed and powder feed rate. The laid tracks are characterized for track geometry and porosity and the quality of the tracks are analyzed. Lower values of laser power and higher powder feed rate results in discontinuous deposition, while higher laser power and lower powder feed rate results in cracked deposits. Porosity is observed to vary from 6–45 % at different process conditions. Analysis of Variance (ANOVA) of deposition rate and track geometry is performed to estimate the major contributing process parameters. This study paves a way to understand effect of process parameters on LAM-DED for fabricating bimetallic joints and graded structures of Copper and SS304L.
Near Wake Regime Study on Wind Turbine Blade Tip Vortex
Authors: Siram Ojing , Sahoo Niranjan
Published: January 2020

In the present research article results on wind turbine blade tip vortex have been presented, the measurements have been done behind a model scale of horizontal axis wind turbine rotor. The rotor used for flow characterization is a three-bladed having NACA0012 cross-section, the study has been performed for low range tip speed ratio of 0–2 and wind speeds range of 3–6 m/s. The investigation has been conducted specifically to near wake regime, which is often expressed as the region of regular helical vortex structures. Although this nature of regular helical vortex pattern has always been a question of debate with respect to changes in the flow condition, rotor geometry and point of measurements. A systematic experiment was done mainly on the frequency of vortex shedding through hot-wire anemometry (HWA), and the corresponding frequency is express in terms of Strouhal number. Present article work within near wake regime includes tip vortex shedding stability analysis for different blade pitch angle and flow condition. From the systematic experimental observation, the evaluated data indicate that the Strouhal number has an incremental trend when the blade pitch angle is close to 40°, and above it inconsistency in frequency response is observed.
Effect of Liquid/Gas Density Ratio on Primary Jet Breakup of Pressure Swirl Atomizer: Experimental and Numerical Study
Authors: Michael Edin , Keerthi Santhosh Kumar , Kant Krishna , Kolhe Pankaj , Banerjee Raja , Chakravarthy S. R.
Published: January 2020

This work reports experimental and numerical study of primary jet breakup of a pressure swirl atomizer. Experiments were performed in a constant volume spray chamber and the spray pattern was characterized as a function of different liquid/gas density ratios which was achieved by changing the ambient pressure. The liquid/gas density ratio was varied between ≈ 102 to 103 and the axial Reynold number was maintained at 6 × 103. Diffused backlight imaging in conjunction with high speed videography was used to visualize the spray. Parameters like spray cone angle, spray breakup length and flapping frequency was estimated. Additionally, POD analysis was performed to find the sheet instability modes.

A corresponding numerical study using Coupled Level Set VOF method was performed keeping the liquid/gas density ratio of 10 and 102 to simulate the primary jet breakup using an in-house two-phase solver developed using OpenFOAM libraries. The solver was validated by following the numerical work of Fuster et al. Effect of computational mesh size on parameters like spray cone angle, breakup length was estimated.
Effects of Total Pressure Distribution on Performance of Small Size Counter-Rotating Axial-Flow Fan Stage for Electrical Propulsion
Authors: Bandopadhyay Tuhin , Mistry Chetan S.
Published: January 2020

Counter-rotating fan stage provides significant benefits over the conventional fan in terms of overall performance and size. For electric propulsion application, counter-rotating fan provides compactness and reduction in weight to achieve higher pressure rise with less power consumption as compared to the unducted propeller. Past literature suggests counter-rotating fans, designed with higher loading in front rotor has a flat performance map and a wider range of stable operation. This, in particular, benefits the electrical vehicle to have higher maneuver capability during operation.

The paper discusses the design methodology of counter-rotating fans for application in roadable electric aircraft ‘Airavat’ and the effect of different loading (total pressure) distributions in front and rear rotor on its overall performance. The fan is required to provide 10 N thrust and hence is designed for total pressure rise of 1000 Pa. The dimension of the fan is decided according to the design constraints of the vehicle. Rotors are designed for the rotational speed of 7500 rpm (Counter-clockwise and clockwise respectively) and flow coefficient of 1.25 at the mid. There are 8 blades in the front and 7 blades in the rear rotor. Fans are designed for four different total pressure rise and hence loading distributions namely, 1) 50%-50%, 2) 55%-45%, 3) 60%-40% and 4) 65%-35% in front and rear rotor. Other design parameters are kept the same for all the four cases.

The performance of the fans with different loading distributions is evaluated through computational study in Ansys CFX using mixing plane approach. It is observed that, as the loading increases in the front rotor, blade camber increases. The blade becomes more prone towards flow separation near the trailing edge under an adverse pressure gradient. Wake coming out from the front rotor grows thicker with higher loading, leading to flow acceleration (thus total pressure loss) in the axial gap between these rotors. As a consequence, flow incidents on the rear rotor other than the design incidence and thus the rear rotor operates under off-design condition. For the equal loading distribution case, the rear rotor does not provide the designed total pressure rise even though the front rotor performs well. With 55%-45% loading distribution, both the rotors give desired total pressure rise and maximum stable operating range. The detailed flow field study is discussed to bring important outcomes for achieving the desired total pressure rise.
Detailed Heat Transfer Characteristics of Matrix Cooling Channels With Rib Angle 35° Using Liquid Crystal Thermography
Authors: Prajapati Anjana N. , Tariq Andallib
Published: January 2020

Matrix cooling is relatively newer cooling technique and preferred over the conventional rib turbulators or pin fin cooling due to its capacity to provide the structural rigidity and higher heat transfer enhancement. The present investigation addresses the detailed study of local and averaged heat transfer augmentation distributions within the sub-channels of matrixes with rib angle 35° and varying sub-channels aspect ratios using liquid crystal thermography. The effects of varying sub-channel aspect ratios 1.2, 0.8 and 0.4 on averaged Nusselt number augmentation, friction factor ratio and thermo-hydraulic performance factor have been also verified within the Reynolds numbers range 5800–14000. The flow trend within the sub-channels is typically found to be eccentric and attributed to the possible vortical flow within the sub-channels and this eccentricity reduces as the sub-channel aspect ratio decreases. Results have shown that the highest Nusselt number augmentation and the lowest friction factor ratio are obtained for the highest sub-channel aspect ratio i.e., the best thermo-hydraulic performance factor (≥ 1) has been found for sub-channel aspect ratio 1.2. The sub-channel aspect ratio is found to have significant effect on both Nusselt number augmentation and friction factor ratio as compared to Reynolds number.
Impact of Sinusoidal Tip Gaps on Axial Compressor Rotor Performance: A Flow Field Investigation
Authors: Goswami Shraman , Malhotra Ashima
Published: January 2020

Performance of an axial compressor rotor depends largely on the tip leakage flow. Tip leakage flow results in tip leakage vortex which is a source of loss. This has an impact on the compressor efficiency as well as stall margin. A lot of work has been done to understand the tip leakage flow and controlling the same. Active and passive stall margin improvement methods mainly target the tip leakage vortex.

In the current study, numerical investigations are carried out to understand flow fields near tip region of rotors. The blade tip designed to have a tip gap as sine and cosine waves (single and double waves). Numerical methodology is validated with NASA Rotor37 test results. The performance parameters of the rotors with modified tip gap shapes are compared with constant tip clearance rotor. A detailed flow field investigation is presented to compare the tip flow structure and its impact on overall performance of the compressor.
Estimation of Active Magnetic Bearings (AMB) Dynamic Parameters and Residual Mass Imbalance Using FEM With PID Controller and Identification Algorithm of a Flexible Rotor System Fully Levitated on AMB
Authors: Murugan S. Bala , Behera R. K.
Published: January 2020

The dynamic analyses of rotating systems are always a testing task to obtain the definite results. This paper carries the dynamic modelling, analysis and identification of coupled flexible rotor system supported by an auxiliary Active Magnetic Bearings (AMBs). An identification algorithm is used to estimate the dynamic parameters of AMB, and rotor residual mass imbalance. The proposed algorithm is a right method for the analysis of fully levitated rotor on AMBs. Finite element method is used to model the dynamic flexible rotor system with PID controller. A conventional dynamic condensation technique is implemented in the development of identification algorithm to overcome the difficulty in numerical simulation. The least-squares fit technique is deployed to estimate the dynamic parameters in frequency domain. Then the algorithm is extended to find the misalignment forces and moments at the coupling point. Numerical study is carried to check the correctness of the algorithm. The proposed algorithm is yet to be tested to experimental results from a fully levitated rotor test rig supported with AMBs.
Thermal Analysis Validation Using Machine Learning
Authors: Nelanti Krishna , Barapu Raviraj , Thiraviyam Suresh , Nidamanuri Naresh
Published: January 2020

Aero-engine components analysis is quite complex in nature and same is the case with thermal analysis. Building an analytical model to simulate actual working conditions of a jet engine is challenging. Many approximations creep into analytical model in the process of simulating real time working environment. Thermal data match is the process to validate analytical model temperatures against experimental data i.e. temperatures measured by the thermocouples instrumented on various components of test engine.

Traditionally, Thermal boundary conditions are varied within permissible limits as mentioned in standard works to account the inability of empirical correlations in capturing physics and assumptions during modeling. Conventional thermal data match requires large number of iterations to match analytical model temperatures against engine data. This demands huge manual efforts and consumes more cycle time.

A methodology is developed using regression based ML algorithm which uses legacy thermal analysis data to identify scale factor to each thermal boundary condition (BC) that influences temperature at a thermocouple location. Initially ML algorithm identifies the weightage that each BC contributes towards data match status at thermocouple location. Once weights are acquired, objective function is formulated using predictor variables (Delta Temperature), response variables (BC Scale factors) along with the weights. Linear programming techniques are employed to solve the objective function subjected to constraints provided in the standard work. Thus, the output of the program is unique optimal scale factors which satisfy prescribed data match criteria.

The proposed methodology in this paper is validated by data matching compressor case analysis results against test engine thermocouple temperature data. With this approach, user intervention is mostly eliminated. 75% of cycle time reduction is achieved.
Modelling of Gas Cooler for S-CO2 Brayton Power Cycle
Authors: Pandey Vivek , Seshadri Lakshminarayanan , Gupta Jayesh , Mariayyah Ravishankar , Santhosh Nagavally Lingappa , Kumar Pramod
Published: January 2020

Supercritical Carbon dioxide (S-CO2) based Brayton power plants are being extensively researched as an alternative to steam-based power cycles due to high degree of recuperation favoured by higher heat capacities in supercritical state. Several studies revealed that PCHEs are suitable candidate for S-CO2 applications. Although, PCHEs have been well researched for various applications, there is very little information pertaining to the design or performance of PCHEs in S-CO2 applications.

This paper presents a novel methodology for design of a PCHE as gas cooler for a S-CO2 power block. In the first part, a thermal resistance network (TRN) model developed using MATLAB is used for full scale modelling of gas cooler. The geometrical information obtained from TRN model is used to optimize the overall footprint. In the second part, the MATLAB code coupled with a 1-D design tool (Flownex SE) and an optimization software; Isight, is used to optimize the inlet-exit manifold based on flow admittance approach. The 1-D design tool discretizes the inlet-exit manifolds to achieve optimum combination of flow admittances which facilitates identical channel mass flow rate and inlet pressure across each channel/stack ensuring minimum overall pressure drop.

In the current paper a case study for a 10 MW PCHE based gas cooler used in a simple recuperated S-CO2 cycle rejecting heat to ambient at 45 °C and 90 bar, is presented. The gas cooler uses water as the primary heat transfer maintained at 4 bar pressure to facilitate single phase heat transfer. Pinch temperature of 5 K is assumed to exist in all heat transfer surfaces. The MATLAB program is coupled with REFPROP property data base to retrieve the thermodynamic properties across all the nodes.
The Effect of Tip Clearance and Hub Rotation on the Performance of an Axial Compressor Stator
Authors: Jiang Chao , Hu Jun , Wang Jiayu , Li Jun , Xu Rong
Published: January 2020

In this paper, 1.5-stage high-speed compressor stator was studied using numerical computation method. Four gap cases were calculated under the condition of the hub being stationary or rotating, and the characteristic curves of the 1.5-stage compressor was obtained. Firstly, the influence of the change of the gap on the total pressure ratio and the efficiency curve was studied when the state of the hub is fixed. Then, the influence of the rotation of the hub on the total pressure ratio and the efficiency curve was discussed when the tip clearance is fixed. Finally, the total pressure loss of the stator channel would be analyzed. The above research would make people understand that the relative motion of the end wall has an important influence on the performance of the axial-flow compressor; when hub is stationary, the optimal gap is greater than 0, while when hub was rotating, the optimal gap was 0; and recognize that the variation of clearance and the motion state of the hub have an important influence on the distribution of total pressure loss along the span.
Numerical Prediction of Cooling Performance Sensitivity of 1st Stage Nozzle Guide Vane Under Aerothermal Conditions
Authors: Prapamonthon Prasert , Yin Bo , Yang Guowei , Zhang Mohan
Published: January 2020

To obtain high power and thermal efficiency, the 1st stage nozzle guide vanes of a high-pressure turbine need to operate under serious circumstances from burned gas coming out of combustors. This leads to vane suffering from effects of high thermal load, high pressure and turbulence, including flow-separated transition. Therefore, it is necessary to improve vane cooling performance under complex flow and heat transfer phenomena caused by the integration of these effects. In fact, these effects on a high-pressure turbine vane are controlled by several factors such as turbine inlet temperature, pressure ratio, turbulence intensity and length scale, vane curvature and surface roughness. Furthermore, if the vane is cooled by film cooling, hole configuration and blowing ratio are important factors too. These factors can change the aerothermal conditions of the vane operation. The present work aims to numerically predict sensitivity of cooling performances of the 1st stage nozzle guide vane under aerodynamic and thermal variations caused by three parameters i.e. pressure ratio, coolant inlet temperature and height of vane surface roughness using Computational Fluid Dynamics (CFD) with Conjugate Heat Transfer (CHT) approach. Numerical results show that the coolant inlet temperature and the vane surface roughness parameters have significant effects on the vane temperature, thereby affecting the vane cooling performances significantly and sensitively.
Numerical Simulation Studies on the Performance of a Diffuser Attached With Last Stage Compressor Outlet Guide Vanes
Authors: Sriram A. T.
Published: January 2020

Combustor pre-diffuser is an important element connecting the compressor and combustor. The design of pre-diffuser should be in such a way that the flow velocity to be within allowable limit to hold the flame in the combustor and also it should recover pressure with less amount of total pressure loss. The general practice is to design the compressor and combustor separately for their performance. However, integrated design of outlet guide vanes and pre-diffuser is given importance, on nowadays, to improve the overall performance. Basically, the outlet guide vane blades are modified to improve the performance. In the present work, numerical simulations studies have been carried out for a well-known high speed compressor, NASA Stage 37, to identify the influence of blade parameters. The computational domain consists of compressor rotor, stator and combustor pre-diffuser. The stator blades serve as outlet guide vanes. In literature, studies were shown that there is improvement in introducing blade sweep. Also, blade lean was shown some advantages for the case of a pre-diffuser with axial inlet and radial outlet with flow turning. However, in the present case of axial inlet and axial outlet, blade lean has not shown improvement in the performance. A diffuser showing slightly unstable condition in the conventional design, Area Ratio (AR) of 1.5 in the present case, has shown improvement with the presence of blade sweep.
Parametric Study for Adoption of Variable Cycle Engine Concept for Low Bypass Ratio Turbofan Engine
Authors: Swaminathan Kaviya , Mistry Chetan S.
Published: January 2020

Turbojet and turbofan engine propulsion system are extensively used in aircraft. Turbojets have simple engine design and extensively used for supersonic flights. Turbofan engine has high mass flow rate and efficient for subsonic application. Variable Cycle Engines, unlike the traditional engines, can vary between high thrust mode for supersonic operations and high efficiency mode for subsonic operations hence are potentially attractive for supersonic transport and advanced tactical fighter aircraft. Variable Cycle Engine can be described as the one that operates with two or more cycles, could serve as a possible solution to reconciling the necessary performance at different operating conditions. The aim of the engine is to combine the best traits of turbojet (high specific thrust) and turbofan (low specific fuel consumption, low noise). Traditional engines have fixed mass flow but VCE can alter the mass flow and function as high bypass engine for the subsonic case and low bypass engine at the supersonic case.

Different variable cycle engine design philosophies were studied and the engine architecture used in F120 was incorporated into the base design of a low bypass ratio Turbofan Engine. Cycle analysis of VCE was primarily done based on theoretical calculation and parametric study performed with the use of Gasturb software. Two Variable Area Bypass Injectors (VABI) were used to vary the mass flow through the core and the bypass stream. We aspire to achieve enhanced performance at subsonic and supersonic mission segments. Subsonic, supersonic and take off conditions were decided and the base engine was modified to have multiple operating points. The VCE combines two cycles (subsonic, supersonic) in same engine body and it is crucial for the engine components to deliver the required performance at both the design points. The engine design procedure consists of the matching of components like turbine, compressor, exhaust nozzle and the exhaust mixing area. Systematic study of turbine matching for such engine configuration with multiple operating points was carried out to understand the utility of variable geometry in a VCE. For turbine matching, the mass flow through turbine was held constant by adjusting the VABIs and this was repeated for different takeoff conditions to analyses the output in detail.

The non dimensional mass flow through the turbine was fixed for both the design points and hence the turbine could be designed to provide high efficiency. The fuel consumption was found to have decreased compared to the baseline condition which in turn leads to low SFC and higher endurance.
Design of High Transonic Axial Compressor Stage for Small Gas Turbine Applications
Authors: Kumar S. Satish , Kumar Lakshya , Kumaran R. Senthil , Kumar Veera Sesha , Shobhavathy M. T.
Published: January 2020

In the quest for achieving high performance, gas turbine engines demand efficient design of various engine components, mainly the compressor stages. The compressor stages consume most of the energy produced by the engine to provide the required pressure ratio. CSIR-NAL is involved in the development of a small gas turbine engine for UAV applications. In this regard, a high transonic single stage axial flow compressor is designed with a mass flow of 4.6 kg/s and pressure ratio of 1.6, for technology demonstration. In this paper, the aerodynamic and structural design of a high transonic axial compressor stage is discussed along with its performance characteristics. Preliminary mean-line design of the compressor stage is carried out, followed by detailed 3D blade design. Aerodynamic performance of the compressor stage is investigated numerically. Grid independency study is carried out, and the flow un-altering grid is used for steady simulations. Steady 3D RANS CFD simulations with SST turbulence model are carried out for estimating the compressor stage performance. At the design speed, the compressor is able to produce the desired pressure ratio and efficiency. Detailed flow investigations across the compressor stage are studied from choke to near stall flow conditions for different speeds. The compressor rotor blisk made of titanium alloy (Ti6AL4V) is subjected to stress analysis. The von-Mises stress and radial deformation are observed to be well within the safe limits of the chosen material. Modal analysis is carried out to study the structural dynamics of the rotor.
An Integral Approach to Designing of an Optimized and Reliable Anti-Icing System Under Off-Design Operating Regimes in a Gas Turbine
Authors: Mehta Nishit , Altukhova Olga , Nassar Abdul , Moroz Leonid
Published: January 2020

Anti-icing systems (AIS) are used in aviation and in ground gas turbines operating in humid climates where relative humidity is above 80% with mist and the temperature of the intake air drops to 5°C and below. Ice formation can disrupt the compressor work by causing vibrations, inlet flow blockage or even a surge in some cases. An anti-icing system is activated in such cases to heat the inlet air before it reaches the compressor. The objective of this work is to design and study an anti-icing system (AIS) for different ambient air parameters and different gas turbine modes of operation. A particular climatic situation (Saint-Petersburg, Russia) is considered as the basis for assessing the suitability of different anti-icing systems and to choose the best configuration out of different possible arrangements. The present work is divided in three major tasks. The first task involves the choice of the anti-icing system arrangement. The second task is to design the heating air supply system by determining the geometric sizes of bypass pipeline with fully open damper to ensure conduction of required air flow at the anti-icing system design condition. In the final task, the entire process is integrated and automated to calculate multiple iterations for different gas turbine operating regimes to assess the reliability of the designed anti-icing system at all operating conditions of the gas turbine. Such assessment is critical as it helps to identify the operating conditions at which the designed anti-icing system would not be able to heat the intake air to a certain temperature above the dew point temperature.
The Study on Effect of the Number of Nozzle Vanes in a Radial Flow Turbine for the Turbocharger
Authors: Kannan Ramesh , Prasad Bhamidi , Koppa Sridhara , George Libin , Karuppanan Kuppusamy
Published: January 2020

The effect of number of nozzle vanes in the turbine stage of a turbocharger is studied using computational fluid dynamics. The nozzle vane unit having 8, 9 and 10 numbers of nozzle vanes configuration is proposed for the radial flow turbine with 30 mm wheel tip diameter. At maximum opening position of the nozzle vanes and for the typical turbine expansion ratio of 2.5, the reduction in mass flow parameter with 10 numbers of nozzle vanes is about 1% lower compared to the 8 numbers of nozzle vanes. The maximum turbine flow range is not affected with higher number of nozzle vanes. The improvement in flow guidance is observed in nozzle vane unit having 10 numbers of nozzle vanes. The improvement in pressure distribution is observed in both the nozzle vane and turbine wheel with increase in number of nozzle vanes. The entropy generation in a turbine stage is found to decrease with increase in the number of nozzle vanes.
Experimental and Numerical Analysis of Turbulent Swirl Flow Structure in Double Swirler Burner
Authors: Sellan Dhanalakshmi , Murugan Raju , Balusamy Saravanan
Published: January 2020

Dynamic and kinematic characteristics of non-reactive turbulent swirl flow studies are significant for optimizing burner design, stability, and validating numerical simulations. The experiments were conducted on unconfined double swirler burner to understand the structure of non-reactive turbulent swirl flow for various inner and outer swirl Reynold’s numbers (Re). The burner is designed with double swirlers, inner and outer; both are medium swirlers with geometric swirl number of 0.8. The instantaneous 3C-2D velocity field in a plane is obtained by using Stereo Particle Image Velocimetry (SPIV) in backward-backward scattering position. In each case, 1000 image pairs are acquired with appropriate calibration and post-processed using cross-correlation and particle tracking technique. Turbulence parameters such as Reynolds stress and turbulence intensity as well as the velocity field of all three components are analyzed for various Re that are useful to understand the effect of turbulent mixing. Numerical study for the same cases are carried out, and experimental results are compared with numerical results. A computational domain contains 1146217 cells are generated for the 3D numerical simulation, and Large Eddy Simulation (LES) approach is used to predict the unsteady behavior of the flow fields. The increase in inner swirl Re increases both axial and azimuthal velocity component, which facilitate mixing in gas turbine application. The inner recirculation zone moves downstream with the rise in inner swirl Re and subsequently increasing the outer swirl Re leads to the operating condition where the blowout may occur.
Subharmonic frequency response in a magnetic pendulum
Authors: Luo Yao , Fan Wenkai , Feng Chenghao , Wang Sihui , Wang Yinlong
Published: January 2020

We study the subharmonic frequency response of a generalized driven oscillator excited by a nonlinear periodic force. We take a magnetic pendulum called the Doubochinski pendulum as an example. So-called “amplitude quantization,” i.e., the existence of multiple discrete periodic solutions, is identified as subharmonic resonance in response to nonlinear feeding. The subharmonic resonance frequency is found to be related to the symmetry of the driving force: Odd subharmonic resonance occurs under an even symmetric driving force, and vice versa. We obtain multiple periodic solutions and investigate the transition and competition between multistable orbits via frequency response curves and Poincaré maps. Experimentally observed phenomenon can easily be reproduced in a student laboratory. This provides a perfect example to demonstrate the rich dynamics related to the effect of nonlinear driving within the scope of undergraduate physics.
On the optimization of dissipative chain events
Authors: Sahu Renu Raman , Nain Rishabh , Singh Vijay A.
Published: January 2020

A chain event consists of a succession of similar events leading to a cumulative and, at times, dramatic and unexpected effect. In the present work, we consider two examples from undergraduate physics. The first is from mechanics, and it concerns one-dimensional collisions leading to efficient energy transfer between disparate masses. The second from optics deals with the rotation of the plane of polarization of light by a succession of suitably rotated polarizers. In each example, we examine the role of dissipation and arrive at an optimized arrangement for maximum energy/intensity transmission. Our selection of examples is deliberate, and it is to suggest that we may seek out many examples from undergraduate physics. This topic, namely, the cumulative (and at times dramatic) effect of a sequence of near similar events, is often not discussed in textbooks. Its consideration may make the subject matter livelier as well as educate students about the role of optimization at an early stage in their careers.
Planetary turmoil unleashed during Solar System infancy
Authors: Voosen Paul
Published: January 2020

Models and observations suggest that an earlier date for the upheaval can explain puzzles including a puny Mars.
Chromatin accessibility dynamics in a model of human forebrain development
Authors: Trevino Alexandro E. , Sinnott-Armstrong Nasa , Andersen Jimena , Yoon Se-Jin , Huber Nina , Pritchard Jonathan K. , Chang Howard Y. , Greenleaf William J. , Pașca Sergiu P.
Published: January 2020

Organoids recapitulate brain development

Gene expression changes and their control by accessible chromatin in the human brain during development is of great interest but limited accessibility. Trevino
et al.
avoided this problem by developing three-dimensional organoid models of human forebrain development and examining chromatin accessibility and gene expression at the single-cell level. From this analysis, they matched developmental profiles between the organoid and fetal samples, identified transcription factor binding profiles, and predicted how transcription factors are linked to cortical development. The researchers were able to correlate the expression of neurodevelopmental disease risk loci and genes with specific cell types during development.

Science
, this issue p.
eaay1645
The stillness of sleep
Authors: Wisden William , Franks Nicholas P.
Published: January 2020

A key neuron in the basal ganglia commands both sleep and immobility
In Vitro
Activity of Sulbactam-Durlobactam against Acinetobacter baumannii-
calcoaceticus
Complex Isolates Collected Globally in 2016 and 2017
Authors: McLeod Sarah M. , Moussa Samir H. , Hackel Meredith A. , Miller Alita A.
Published: January 2020

Acinetobacter baumannii
-
calcoaceticus
complex (ABC) organisms cause severe infections that are difficult to treat due to preexisting antibiotic resistance. Sulbactam-durlobactam (formerly sulbactam-ETX2514) (SUL-DUR) is a β-lactam–β-lactamase inhibitor combination antibiotic designed to treat serious infections caused by ABC organisms, including multidrug-resistant (MDR) strains. The
in vitro
antibacterial activities of SUL-DUR and comparator agents were determined by broth microdilution against 1,722 clinical isolates of ABC organisms collected in 2016 and 2017 from 31 countries across Asia/South Pacific, Europe, Latin America, the Middle East, and North America.
CD8 T Cells and STAT1 Signaling Are Essential Codeterminants in Protection from Polyomavirus Encephalopathy
Authors: Mockus Taryn E. , Netherby-Winslow Colleen S. , Atkins Hannah M. , Lauver Matthew D. , Jin Ge , Ren Heather M. , Lukacher Aron E.
Published: January 2020

A comprehensive understanding of JCPyV-induced PML pathogenesis is needed to define determinants that predispose patients to PML, a goal whose urgency is heightened by the lack of anti-JCPyV agents. A handicap to achieving this goal is the lack of a tractable animal model to study PML pathogenesis. Using intracerebral inoculation with MuPyV, we found that MuPyV encephalitis in wild-type mice causes an encephalopathy, which is markedly exacerbated in mice deficient in STAT1, a molecule involved in transducing signals from type I, II, and III IFN receptors. CD8 T cell deficiency compounded the severity of MuPyV neuropathology and resulted in dramatically elevated virus levels in the CNS. These findings demonstrate that STAT1 signaling and CD8 T cells concomitantly act to mitigate MuPyV-encephalopathy and control viral infection.
Curious case of myxoid adipocytic tumour with ureteropelvic junction obstruction in horseshoe kidney: dilemma in management
Authors: Nayyar Rishi , Kumar Prashant , Barwad Adarsh Wamanrao , Saini Sumit
Published: January 2020

Isolated renal involvement by myxoid adipocytic tumour is a very rare presentation. We are reporting a horseshoe kidney with ureteropelvic junction obstruction (UPJO) with myxolipoma, which was revealed after routine histopathological evaluation postbilateral open pyeloplasty. We evaluated the patient thoroughly and after detailed discussions with the patient and parents, took the decision to manage the patient on active surveillance with interval imaging and renal dynamic scans. Managing a myxolipoma associated with UPJO is a novel experience as a surgeon, by virtue of its extreme rarity. Isolated myxolipoma of renal pelvis in association with UPJO and horseshoe kidney has never been reported earlier to the best of our knowledge. The patient has not progressed at follow-up of 30 months with occasional mild abdominal discomfort. We intend to closely monitor the patient in similar fashion. Any significant progression of disease or renal failure shall entail nephrectomy with excision of mass and subsequent renal replacement therapy.
Pulmonary haemorrhage following thrombolysis with streptokinase in myocardial infarction
Authors: Prasad Krishna , Singh Parminder , Kanabar Kewal , Vijayvergiya Rajesh
Published: January 2020

Pulmonary haemorrhage is a rare but a life-threatening complication of thrombolytic therapy in patients with acute ST-elevation myocardial infarction (MI). It usually presents with anaemia, massive haemoptysis, acute-onset respiratory distress and diffuse bilateral lung infiltrates on imaging. We hereby describe two patients, who had pulmonary haemorrhage following streptokinase therapy for acute MI. The first patient improved with conservative treatment, while the second patient died due to respiratory failure. Streptokinase, a fibrin non-specific agent, is a widely used thrombolytic in low-income and middle-income countries. Pulmonary haemorrhage should be suspected in patients who develop sudden respiratory compromise after receiving thrombolytics, especially streptokinase. The management issues related to this uncommon life-threatening complication have been discussed in this article.
Ofatumumab for multirelapsing membranous nephropathy complicated by rituximab-induced serum-sickness
Authors: Podestà Manuel Alfredo , Ruggiero Barbara , Remuzzi Giuseppe , Ruggenenti Piero
Published: January 2020

Rituximab (375 mg/m2) achieved remission of the first episode and six relapses of nephrotic syndrome (NS) in a young male patient with podocyte phospholipase A2receptor (PLA2R)-related membranous nephropathy (MN) refractory to steroids and cyclosporine. Between-treatments interval averaged 17.4±4.2 months. The seventh infusion was complicated by delayed serum-sickness, which resolved with steroids. On subsequent relapse, the fully human anti-CD20 monoclonal antibody ofatumumab (300 mg) achieved remission of the NS, without significant side effects. Circulating CD19+B cells were depleted, proteinuria decreased from 10.9 to 1.3 g/day, and serum albumin, immunoglobulin levels and glomerular filtration rate normalised. Twenty-eight months later, despite transient anti-PLA2R depletion, ofatumumab (100 mg) failed to induce remission of the eighth relapse. Remission was safely achieved 5 months later with repeated ofatumumab infusion (300 mg). This treatment (€723) was less expensive than rituximab (€1801). Ofatumumab could be a safe and cost/effective rescue therapy for patients with MN sensitised against rituximab.