bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Analysis of NACA Aerofoil Using Synthetic Jet
Authors: Neve Mayuresh , Kalamkar V. R. , Wagh Akshay
Published: February 2018

Usually at high angle of attack, aerofoil stalls due to flow separation on suction surface of aerofoil. To delay the flow separation, pulsating jet arrangement, known as Synthetic jet is used in aerofoil. It is produced by periodic suction and ejection of fluid from an orifice. This condition can be achieved by inducing movement to diaphragm or by giving a zero mass flux sinusoidal boundary condition to the jet. This allows the reattachment of boundary layer which improves the lift and drag performance and angle at also delays stalling angle. In present study, CFD analysis on NACA0015 aerofoil is performed for different angles of attack and the Co-efficients of Drag (Cd) and Lift (C1) are validated with the experimental results of Gilarranz et al. [1]. The flow is simulated by solving Unsteady RANS coupled with k-ε realizable turbulence model with enhanced wall treatment. Synthetic jet is placed in NACA0015 airfoil at 12% of the chord length with width as 0.53% of chord and is studied for a Reynolds number Re = 8.96 × 105 and for angle of attack from 12 to 20 degrees [2]. The jet is almost tangential to the wall at an angle, αjet = 10° and chord length is considered as 0.375m for the study. Further, parametric analyses are conducted on NACA 0015 aerofoil to investigate effect of parameters (frequency, jet angle, jet velocity). It is observed that aerofoil’s performance is improved significantly for jet angle (30°–40°), jet frequency (100 Hz) and non dimensional jet velocity (1.8–2.0). A maximum increase of approximately 26% in Lift was observed at AOA 20°.
Flow Studies on a Single Stage Transonic Axial Flow Compressor Retrofitted With Circumferential Grooves and Varied Rotor-Stator Axial Gap
Authors: Darji Anand P. , Alone Dilipkumar Bhanudasji , Mistry Chetan S.
Published: February 2018

A transonic axial flow compressor undergoes severe vibrations due to instabilities like stall and surge when it operates at lower mass flow rate in the absence of any control devices. In present study, the attempt was made to understand the combine impact of circumferential casing grooves (CCG) of constant aspect ratio and different axial spacing between rotor and stator on the operating stability of single stage transonic axial compressor and that of rotor alone using numerical simulation. The optimum rotor-stator gap in the presence of grooved casing treatment was identified. The steady state numerical analysis was performed by using three-dimensional Reynolds Average Navier-Stokes equation adapting shear stress transport (SST) k-ω turbulence model. The study is reported in two sections. First section includes the detailed numerical study on baseline case having smooth casing wall (SCW). The computational results were validated with the experimental results available at Propulsion Division of CSIR-NAL, Bangalore. The computational study shows good agreement with experimental results. The second section comprises the effects of optimum designs of CCG and various axial spacing on the stall margin improvement of transonic compressor. Current computational study shows that the axial spacing between rotor and stator is an important parameter for improvement in stall margin not only for SCW but also for CCG. Therefore, the highest stall margin improvement of 9% has achieved for 75% axial spacing.
Revisiting V-3 Canon for the Application of Single Stage Gas Gun
Authors: Mathew Arun Tom , Koka Tirumala Rao , Payangapadan Murali Krishnan
Published: February 2018

Single stage gas guns are typically used for accelerating the projectiles in bird and hail impact tests of aerospace components and engines. In this paper an alternative design for single stage gas gun is studied, which is derived from V3 canon. Three dimensional numerical simulations is carried out for the optimal secondary connection angle with the main barrel. A one dimensional code is developed for the V3 canon based design. Design of experiments conducted to find the response surface for the optimal location of the secondary connection, volume and pressure of the secondary tank.
Influence of Fuel Jet Momentum on Characteristics of a Reverse-Cross Flow Combustor
Authors: Gupta Shreshtha Kumar , Arghode Vaibhav
Published: February 2018

The current work is aimed towards development of high thermal intensity, low emission combustor for gas turbine engines. Employing discrete and direct injection of air and fuel in a combustion chamber and has been demonstrated to result in low pollutant emissions (NOx, CO, UHC). From our previous investigations, we found that the reverse-cross flow configuration, where air is injected from the exit end and fuel is injected in the cross flow of the injected air, results in favorable combustion and emission characteristics. Though the air jet is the dominant jet, the fuel jet can also influence the flow field, mixing and the combustion behavior inside the combustor, which is the subject of the current investigation. Here we investigate a high thermal intensity combustor relevant to gas turbine engines (at equivalence ratio of 0.8, the combustor operates at thermal intensity of 39 MW/m3-atm and heat load of 6.25 kW). Natural gas is used as the fuel and two different fuel injection diameters of 1 mm and 2 mm are investigated. This result in significantly higher (four times) fuel jet momentum from the smaller fuel injection port as compared to the larger port. From computational fluid dynamics (CFD) studies, it is observed that for the case with higher fuel jet momentum, the fuel jet deflects the air jet such that the flow pattern is significantly altered as compared to the case with lower fuel jet momentum. OH* chemiluminescece images show that the reaction zone location is significantly affected with high momentum fuel jet. NOx is reduced whereas CO is increased with higher momentum fuel jet.
Secondary Air Performance Optimization of a Combined Impingement and Film Cooled Gas Turbine Nozzle Guide Vane
Authors: Kukutla Pol Reddy , Prasad Bhamidi V. S. S. S.
Published: February 2018

Multi-objective optimization of the film cooled holes for the coupled impingement-film cooled nozzle guide vane is conducted. Two objectives are considered to be minimized: coolant jet exit total temperature and static pressure drop, to assess the trade-off between them. Three-dimensional computationally using SIMPLE algorithm analysis and a k-ω SST turbulence model are used for generating a data base. The plenum mass flow rates and mainstream velocity are considered as the two design variables. The second order polynomial response surface method is chosen to develop the objective function approximation. The multi-objective optimization has been carried out with help of a genetic algorithm and sequential quadratic programing (fminicon) in MATLAB 7.11.0 (R2010b). The Pareto-optimal design points are obtained as the plenum coolant mass flow rate of 0.004kg/s and mainstream velocity of 10m/s. Based on these results, the global minimum coolant jet static pressure drop of 32.5 Pa and global minimum jet exit total temperature of 312K are observed for the film holes of the NGV surface. At these operating conditions, the coupled impingement -film cooled NGV is subjected to its higher safety and durability. This happened due to without cause of hot gas ingestion into the film cooled jets of the typically cooled NGV.
Transient Dynamic Analysis of Pretwisted Functionally Graded Conical Shells Subject to Low Velocity Impact: A Finite Element Approach
Authors: Das Apurba , Banerjee Ranojit , Karmakar Amit
Published: February 2018

This paper investigates on the problem of functionally graded (FG) shallow conical shells subjected to low-velocity impact by a solid spherical mass at the centre. Turbomachinery blades with low aspect ratio could be idealized as twisted rotating cantilever FG shallow conical shells. An analytic solution method is developed to solve and predict the impact response in terms of contact force, impactor displacement, initial velocity of impactor, target displacement and indentation of the FG conical shells with different sigmoidal power law exponent. A modified Hertzian contact law considering permanent indentation is used to calculate the contact force along with other impact response parameters. Using the Newmark’s time integration scheme the time dependent equations are solved. An eight noded isoparametric shell element is considered for the present finite element model. Parametric studies are performed to study the effects of triggering parameters like initial velocity of impactor (VOI), mass of the impactor (M0) and twist angle (Ψ) considering different sigmoidal power law exponent (N) for Ni (Nickel)-ZrO2 (Zirconia) and Ti (Titanium alloy-Ti–6Al–4V)-ZrO2 (Zirconia) functionally graded conical shell subjected to low velocity impact.
A Compliant Algorithm to Diagnose Multiple Centrifugal Pump Faults With Corrupted Vibration and Current Signatures in Time-Domain
Authors: Rapur Janani Shruti , Tiwari Rajiv
Published: February 2018

Centrifugal pumps (CPs) are crucial components in many plant operations. However, they are susceptible to failures due to mechanical faults and/or fluid flow abnormalities. These faults not only affect the CP system but also affect the systems delivering flow to it or receiving flow from it. Therefore, it is extremely crucial to recognize the faults and estimate their severity during operation, so that a corrective action may be initiated. In the present work, an attempt has been made to develop a flexible algorithm based on support vector machine (SVM) suitable to classify CP faults, like the suction and discharge blockages (with varying severities), impeller defects, pitted cover plate faults and dry runs. Also, a combination of mechanical faults (impeller defects and pitted cover plate faults) and suction and discharge blockage faults are considered. For the sake of classification, the CP vibration data and the motor line-current data are generated in time-domain for each fault experimentally. Furthermore, industrially operating CP signatures cannot be immune to noise generated from other operating equipment in the premises. Hence, to assess the robustness of the developed methodology, signals are corrupted by adding 5%, 10% and 25% additive white Gaussian noise. The developed algorithm is tested with corrupted data. The efficiency of fault predictions obtained while testing with noisy and non-noisy data are compared. The results are very promising and carry a high potential for industrial applications.
An Experimental Study of the Slip Factor in a Wet Gas Centrifugal Compressor With IGV
Authors: Vigdal Levi André B. , Bakken Lars E.
Published: February 2018

The introduction of wet gas compression provides the opportunity for future cost-effective production of oil and gas. A wet gas compressor consists of a robust unit able to increase the pressure of untreated natural gas. This permits longer transport of hydrocarbons without topside facilities if installed at the well head. Obvious benefits include prolonging the life of existing wells and the possibility of exploiting smaller hydrocarbon sources otherwise considered non-commercial.

Successful development of robust wet gas compressors requires further understanding of the phenomena which occur when liquid is present in the gas stream. Understanding the way the presence of liquid affects the velocity triangle and slip factor is essential for the design of wet gas compressors and for comprehending their response to varying levels of liquid content in the inlet stream.

An experimental study has been performed with various levels of liquid fractions and inlet swirl angles. Impeller-exit velocity components and shift in slip factors are presented within the experimental test boundary.

A shift in velocity components and slip factor is experienced with increasing liquid content and inlet guide vane (IGV) setting angle. Consequently, existing slip factor correlations not utilizing inlet flow characteristics are not valid for wet gas flow or with impeller inlet swirl.
Computational Studies on High Pressure Turbine Rim Seal Cavities
Authors: Chengappa Manjunath B. , Srinivasan Karthik , Chouhan Rohit , Bather Simon , Blidmark Eric
Published: February 2018

The efficiency of a turbine stage is impacted by a number of factors such as the component design philosophy, operating environment, leakage flow and its interaction with the main gas flow path. When looking at improving a turbine stage performance, there is a natural tendency amidst the designers to look into the factors listed above. Every engine manufacture has a unique style of component design philosophy and hence there are fewer opportunities to radically change the design. On the other hand, the operating environment or operating conditions are usually becoming more challenging. Hence, component designers typically look for opportunities to reduce the leakage or to reduce the losses due to interactive effect of the leakage with the gas path. The rim seal flow and its interaction with the gas path has been of interest for the past few decades and many studies have been carried out to understand the impact of cavity geometry, leakage flows and the ingestion of the hot gas into the rim seal cavities.

The rim seal cavities functionally act as a buffer cavity to dilute and dampen the effect of the hot gas ingested into the secondary air flow path and to prevent the discs from being exposed to ingested hot gas. The successful function of the rim seal cavity depends on multiple factors like rotor-stator axial clearance, cavity volume, cavity shape, cavity approach to the gas path and its interface, in addition to the leakage flow into the main flow path.

The present paper aims at providing a review of a typical rim seal cavity used in the High Pressure Turbine based on systematic CFD studies of the rim seal cavities. While the paper does not present validation data for the approach, the authors attempt to provide references to specific design aspects that are already available in the literature, which are usually less noticed.
Reduction of Secondary Flow Losses in Transonic Nozzle Guide Vane Through Axisymmetric Endwall Profile Optimization
Authors: Kaliyaperumal Ananthakrishnan , Govardhan Mukka
Published: February 2018

Improvement in performance and size of gas turbine engine pave the way to the design of high blade loading, low aspect ratio and the small axial gap in the initial stages of turbine. This gives rise to the substantial amount of losses especially secondary flow losses and at the same time, endwall contouring showed its effective part in reduction of secondary flow losses. The intended purpose of the present numerical investigation is to compute the secondary flow mechanisms occurring inside the nozzle guide vane of high pressure turbine stage, a typical representative of modern aero engine design and to optimize its endwall to reduce these losses. Axisymmetric variation in endwall profiles are achieved by functional approximation and genetic algorithm based numerical optimization method. Initially, nozzle guide vane endwalls are parameterized with control points of Bezier curve. A subset of control points are considered as the design variables having a constraint to move in radial coordinate. Statistical tool latin hypercube sampling is adopted to explore the design space. Based on the values of objective functions obtained from the numerical CFD calculations, functional approximation model is construed using the artificial neural network. Finally, a genetic algorithm is used to obtain the optimum solution and analyze the effect of the axisymmetric endwalls on secondary flow losses. Design of endwall profile is studied in three different approaches by confining the axisymmetric variation near hub, shroud and both endwalls. Based on the obtained optimized profiles, secondary flow mechanisms occurring inside the NGV passage are investigated. Reduction in total pressure loss coefficient and improvement in isentropic total-total efficiency are observed for the optimized profiles.
Computational Analysis on Primary Breakup and Deformation of Kerosene Jet in Subsonic Cross Flow Using VOF Method
Authors: Govindaraj Muthuselvan , Halebidu Suryanarayanarao Muralidhara , Kotegar Prateekkumar , Gupta Sonali , Shankar Sanjay , Deekshith Manoja , Mourya Suhruth , Kumar Akshaya
Published: February 2018

The main objective of this computational analysis is to investigate the effect of increase in Weber number at constant momentum flux ratio on the primary breakup process and deformation of kerosene jet in cross stream air flow. Unsteady computational analysis with VOF approach is carried out to simulate the two phase flow at three different cross flow Weber number conditions (150, 350 and 400) at constant momentum flux ratio of 17. Since the results of VOF technique is highly sensitive to the size and distribution of grid, grid optimization process is carried out, with both structured and unstructured forms of the grid. Since the structured grid with number of elements 17,96,181 displayed better matching with experimental results of upper trajectory of kerosene jet; this grid is used to investigate the effect of turbulence model and Weber number on the windward trajectory of kerosene jet in cross flow air stream. Initially to evaluate the results of computational analysis; simulations are carried out with larger computational domain (with number of elements 17,96,181). Windward trajectory of computational analysis is compared with experimental results of upper trajectory predicted using image processing technique and reasonable overall matching is observed.

To investigate the primary breakup process and deformation of liquid jet at three different increasing Weber number conditions, simulations are carried out with smaller computational domain with higher mesh density with number of elements 33,96,146. The computational technique used in the present analysis exactly captures the modes of breakup observed from experimental results at different Weber number operating conditions. To characterize the deformation of liquid jet at different Weber number conditions; near-field trajectory, cross stream dimension and wave length of liquid jet are quantified at different instants of time. With increase in Weber number, decrease in penetration of liquid jet along transverse direction and more bending of liquid jet along flow direction is observed. From the velocity profile along transverse direction of three different conditions, stronger shearing of liquid film is observed in higher Weber number conditions.
Multi Objective Optimisation of an Aero Engine Rotor System Using Nondominated Sorting Genetic Algorithm (NSGA)
Authors: Shibu Kalloor Joseph , Babu Ch. Kanna , K. Degaonkar Girish , Shankar K.
Published: February 2018

A comprehensive multi-objective optimisation methodology is presented and applied to a practical aero engine rotor system. A variant of Nondominated Sorting Genetic Algorithm (NSGA) is employed to simultaneously minimise the weight and unbalance response of the rotor system with restriction imposed on critical speed. Rayleigh beam is used in Finite Element Method (FEM) implemented in-house developed MATLAB code for analysis. The results of practical interest are achieved through bearing-pedestal model and eigenvalue based Rayleigh damping model. Pareto optimal solutions generated and best solution selected with the help of response surface approximation of the Pareto optimal front. The outcome of the paper is a minimum weight and minimum unbalance response rotor system which satisfied the critical speed constraints.
On the Dynamics of Instability Mitigation by Actuating Swirler Motion in a Lean Premixed Turbulent Combustor
Authors: Gopakumar Ramachandran , Belur Vishwanath Rahul , Singh Jasmeet , Dutta Ankit , Chaudhuri Swetaprovo
Published: February 2018

In this paper, we present a novel initial attempt on analysis of the mitigation mechanism of instability by rotating the otherwise static swirler in a lean premixed, swirl stabilized, labscale combustor. It has been reported in our previous work that increasing the swirler rotation rate mitigates the self-excited thermoacoustic instability in a model lab-scale combustor, over a range of conditions. Here, it is found that for a given period of observation, instead of a continuous and gradual decrease in the time localized pressure amplitude from the fully unstable state towards the fully mitigated state, the fraction of the time during which instability is present is reduced. With increasing swirler rotation rates, the instability becomes more intermittent with progressive reduction in frequency of their occurrence. High speed PIV results are also presented along with simultaneous pressure signals which support this claim. Such an intermittent route to instability mitigation could be attributed to the background turbulent flow field and is reminiscent of the intermittent opposite transition (implemented by changing the Reynolds number) from a fully chaotic state to a fully unstable state as recently discovered in Nair, Thampi and Sujith [1]. An attempt is made to model the behavior of pressure oscillations using the well established mean-field Kuramoto model. The variation of the order parameter r, which is the parameter for the measurement of synchronization between the oscillators provides critical insights on the transition from the unstable, intermittent to stable states.
Natural Frequencies of Pre-Twisted Airfoil Blades
Authors: Chakshu Neeraj Kavan , Sinha Sunil K.
Published: February 2018

In this paper, the natural frequencies of pre-twisted cantilever blades of various angles of twist having different airfoil cross sections in the NACA 6 series have been determined. The main objectives of this paper are to replicate the results previously published for the similar types of blades but with the assumption of a uniform rectangular cross-section and to compare it with the results obtained for blades with more refined airfoil cross-sections. Cantilevered type clamped-free boundary conditions have been used in this paper for all blades.

The comparison of the natural frequencies among different airfoils of the same NACA series has also been described in the paper in order to find out if any parameter of the airfoil such as camber, maximum thickness etc have any significant role in changing the frequencies of the beam. Commonly used commercial codes for finite element analysis have been used to determine these results.
Blade Fatigue Life Assessment of an Axial Compressor Rotor Through Probabilistic Method
Authors: Muthu Shanmugam Esakki , Prakash Raghu V. , Ammaiappan Shakthivel
Published: February 2018

The fatigue life of the titanium alloy axial compressor rotor blade was estimated based on stress based life method. The fatigue life of the compressor blade was evaluated through incremental amplitude test method. The incremental amplitude test method involves cumulative fatigue damage at different stress levels by using Miner’s Hypothesis. The probabilistic analysis of fatigue life was carried out by Weibull distribution method. The analytical and test methods results were compared and found satisfactory.
Performance of an Annular Combustor Under Windmill Conditions During Stand-Alone and Engine Level Altitude Test
Authors: Karuppannan Srinivasan , Maurya Dalton , Navindgi Raju D. , Muthuveerappan N.
Published: February 2018

Relight envelope of the combustor needs to be experimentally generated and established during the design and development of an aero gas turbine engine. Usually, during development stage of engine, compressor characteristics are not readily available at such low speeds and hence, it becomes difficult to specify the combustor inlet conditions such as pressure, temperature and Mach number during the engine light up studies. This paper compares the experimental test data generated on an annular combustor for windmill conditions during stand-alone mode and engine level tests under simulated flight conditions. The stand-alone combustor trials were conducted for the range of total pressure and temperature relevant to the flight altitude and Mach number range. During the engine level tests, combustor relight tests were conducted under simulated conditions (ISA+15) for altitudes ranging from 5.5 km to 10 km, flight Mach numbers in the range of 0.45 to 0.80. In this paper, effect of altitude and flight Mach number on the windmill spool speed, combustor pressure and temperature are studied.
A Study of Multiple Techniques to Simulate Blade Out Event
Authors: Ramanadham Koti Satish , Kasina Lakshman , Bommisetty Kondaiah , Raghavan Kotur Srinivasan
Published: February 2018

Successful demonstration of safety of aircraft engines during extreme events such as Foreign Object Damage and Containment are mandatory for FAA (Federal Aviation Administration) certification. According to FAA every engine has to undergo fan blade out tests and engine has to contain this event without leading to major hazard to aircraft and loss of life. The fan blade out containment test involves the intentional release of a fan blade when the engine is running at full power. The released blade must not pierce or fracture the engine cases during the impact and which in turn can cause damage to the aircraft.

The current trend in the industry is to minimize tests through analytical simulations and demonstrate compliance to regulations and flight-safety requirements. Accurate simulations of such events save significant effort, time and cost. This paper presents the various simulation techniques to demonstrate fan case containment when subjected to fan blade out event. The modeling is carried out with simplifications and assumptions to minimize problem size and maximizing the accuracy in simulation. Various simulation techniques analyzed in this study are used to assess the modeling approach and parameters influence on the event simulation. The effect of rotor imbalance on blade failure and blade kinetic energy are also studied in this paper. LS-DYNA has the capability to perform implicit and explicit methods which is used to analyze the blade out event in this study.
CFD Analyses of Combustor-Diffuser System of Marine Gas Turbine Engine
Authors: Karuppannan Srinivasan , Sondur Vaibhav Murlidhar , Sivaramakrishna Gullapalli , Navindgi Raju D. , Muthuveerappan N.
Published: February 2018

Reverse flow can annular combustor configuration becomes the inevitable option for industrial and marine gas turbine engine, due to its advantages over other configurations. The complexity associated with can annular configuration is optimum design of annular diffuser, as its flow field is dominated by downstream blockage created by transition duct geometry.

In the present study, flow behavior in the annular diffuser has been analyzed by simulating realistic downstream combustor liner and transition duct geometry. Flow analysis has been carried out using ANSYS Fluent and turbulence has been modeled using Realizable k-ε model. The diffuser is designed based on G* method, for optimum pressure recovery. Six diffuser configurations have been analyzed by varying the inner wall profile. The effect of parameters on flow field within diffuser and dump region has been studied. Also, the static pressure recovery and total pressure loss coefficient of diffuser is calculated and compared. The results show that the profile of the inner wall and the dump region needs to be tailored to get optimum performance from diffuser.
Performance Improvement of Gas Turbine Power Plant by Intake Air Passive Cooling Using Phase Change Material Based Heat Exchanger
Authors: Dandotiya Devendra , Banker Nitin D.
Published: February 2018

The power output of a gas turbine plant decreases with the increase in ambient temperature. Moreover, the ambient temperature fluctuates about 15–20°C in a day. Hence, cooling of intake air makes a noticeable improvement to the gas turbine performance. In this regard, various active cooling techniques such as vapor compression refrigeration, vapor absorption refrigeration, vapor adsorption refrigeration and evaporative cooling are applied for the cooling of intake air. This paper presents a new passive cooling technique where the intake air temperature is reduced by incorporating phase change material (PCM) based heat exchanger parallel to conventional air intake line. During the daytime, the air is passed through the PCM which has melting temperature lower than the peak ambient temperature. This will reduce the ambient air temperature before taking to the compressor. Once the PCM melts completely, the required ambient air would be drawn from the ambient through conventional air intake arrangement. During the night, when there is lower ambient temperature, PCM converts from liquid to solid. The selected PCM has a melting temperature less than the peak ambient temperature and higher than the minimum ambient temperature. It is observed from the numerical modeling of the PCM that about four hours are required for the melting of PCM and within this time, the intake air can also be cooled by 5°C. The thermodynamic analysis of the results showed about 5.2% and 5.2% improvement in net power output and thermal efficiency, respectively for four hours at an ambient temperature of 45°C.
Imbalance Response of Nonlinear Rotor-SFD Dynamic Systems With Structure Modelled As FRFs Using Harmonic Balance Method
Authors: Settipalli Manoj , Chandran Rahul , Ganji Venkatarao , Brockett Theodore
Published: February 2018

Squeeze-film-dampers (SFDs) used to couple rotor dynamic systems to linear static structures, such as those in aircraft engines and turbochargers, are often approximated as linear connections in dynamic simulations. Linearized stiffness and damping coefficients of the SFDs can be reasonably estimated for circular centered orbits. Selection of linearized properties for the SFD is challenged under more general whirling conditions, such as those occurring in non-centered dampers with steady gravity loading. In this paper, an efficient method for coupling the rotor system to a static structure modeled as frequency-response-functions (FRFs) through nonlinear SFDs is illustrated. The harmonic balance method (HBM) with arc length continuation technique is employed in the frequency domain to obtain the system periodic response. Degrees-of-freedom participating in the non-linear SFD model, when separated from the remaining linear degrees-of-freedom, are expanded in terms of Fourier coefficients. The algorithm allows the Fourier coefficients approximating the nonlinearity to be iteratively determined at each frequency of interest. The approach has a tremendous time advantage over a traditional nonlinear transient analysis. The method can be used to efficiently predict vibration response on the engine static structure to typical imbalance on the rotors to assess the risk of meeting the low vibration requirements typical of new designs. The prediction includes the primary driving frequencies and their harmonics in the vibration estimate. A flexible rotor system connected to structure through an SFD is used to demonstrate the approach and discuss the impact of results.
Parametric Study of Stability Criteria for Rotor Bearing Model With Viscoelastic Support
Authors: Chandraker S. , Dutt J. K. , Roy H.
Published: February 2018

In the last few decades, intensive research has been carried out on viscoelastic materials. Among them, most importantly polymers and composites thereof find extensive applications in engineering structures and rotors primarily due to quite high strength to weight ratio in comparison with metals. In dynamic modeling of rotor bearing system, incorporation of damping is very important as stationary (external) damping always helps in stability, however rotary damping (internal) promotes instability of rotors above a certain speed. Therefore for modeling point of view, it is very important to consider both internal or external damping effect. For this reason, the dissipation mechanism has been handled in such a way that it provides proper forces irrespective of its presence in a stationary or a rotary frame. Also in present work, both classical method and operator multiplier method are suggested to derive the equations of motion. The analysis also shows the stability zones of the rotor bearing system for various parametric values of different viscoelastic supports. It is found that choosing a right viscoelastic support can increase the stability criteria of the system to some extent.
Engineering and Economic Models of Vertical Axis Wind Turbines
Authors: Bah Elhadji Alpha A. , Sankar Lakshmi N. , Jagoda Jechiel I.
Published: February 2018

The interest in sustainable forms of energy is being driven by the anticipated scarcity of traditional fossil fuels over the coming decades. There is also a growing concern about the effects of fossil fuel emissions on human health and the environment. Many sources of renewable energy are being researched and implemented for power production. In particular, wind power generation by vertical-axis wind turbines is one of the option often considered. This option offers a robust design because of the relative simplicity of its technology. However, it also presents challenges that are inherent to its very concept. These systems suffer from dynamic stall, noticeably one of the main causes of the loss of performance. A dual-element concept is proposed as a way of alleviating the losses due to the dynamic stall. An economic analysis is done to establish the economic viability of the model. The Great Coast of Senegal is selected as a site of operation in this study.
Preliminary CFD Study on the Effect of Fuel Injector Coking on Fuel Spray Characteristics
Authors: Agarwal Parash , Sethi Vishal , Gauthier Pierre Q. , Sun Xiaoxiao , Liu Yize
Published: February 2018

Fuel injector coking involves deposit formation on the external or the internal surfaces of an injector or nozzle. This deposition of carbonaceous particles can result in uneven fuel-spray characteristics or localised burning (hot spots), which may eventually lead to mechanical failure or simply have a detrimental effect on the combustion system. This study focuses on the use of numerical methods to investigate the effect of coke formation on both the atomiser internal flow passages and its spray characteristics. Three different cases are examined; one investigating the clean injector; the second investigating the effect of internal coking; and the third investigating the effect of nozzle tip coking. A pressure swirl atomiser was considered for the purpose of the study. Validation of the numerical results for the clean injector condition is carried out against published experimental data. Two arbitrary geometries of coke deposits were created. The Volume of Fluid (VOF) multiphase model has been used in conjugation with a Geometrical Reconstruction Scheme (GRS) to simulate the interface representing the two phases. Spray cone angle and the liquid film thickness for the clean injector condition predicted by numerical simulation agreed well with the experimental data. Instabilities in the air core and the spray angle were also observed because of the presence of coke layers. Fouling present on the injector tip resulted in an earlier breakup of the film which can thereby affect the flame lift-off length. These stated observations can have significant implications both on the performance as well as the life of the combustion systems, thereby establishing the relevance of this study.
Dynamic Behaviour of Delaminated Composite Plate Under Blast Loading
Authors: Hirwani Chetan Kumar , Panda Subrata Kumar , Mahapatra Siba Sankar , Mandal Sanjib Kumar , De Apurba Kumar
Published: February 2018

In the present article, the dynamic behaviour of the delaminated composite plate subjected to blast loading has been investigated. For the investigation, a general finite element model using higher-order mid-plane kinematics has been developed. The model has been discretised using nine noded isoparametric Lagrangian elements having nine degrees of freedom at each node. The continuity in the laminated and delaminated section has been established using the intermittent continuity condition. The final governing equation has been solved by applying Newmark’s time integration scheme in conjunction with finite element steps. Further, the said responses have been evaluated by developing an in-house MATLAB code based on the proposed model. In order to illustrate the consistency and accuracy of the present model, convergence and comparison study has been conducted i.e. the responses are evaluated for different mesh sizes and compared them with those of responses of earlier published literature. Finally, various examples have been solved to illustrate the influence of the size and position of debonding, side to thickness ratio, aspect ratio and end condition on the dynamic response of composite structure and discussed in detail.
Large Eddy Simulation of a Compressor Stage
Authors: Mondal Pranab , Mathew Joseph
Published: February 2018

A methodology for large eddy simulation (LES) of a turbomachine stage is presented. Computations of mean fields (RANS) of stages may be performed separately of rotor and stator rows by providing an averaged solution as input to the down-stream row. In unsteady simulations, unsteady field information must be exchanged in both directions after every time step. Here a procedure for linear cascade simulations of a stage has been implemented in a high-resolution compressible flow solver for LES. The LES uses an explicit filtering method for sub-grid-scale modelling. Grids overlap at the interface between blade rows. Field data is transferred in both directions. Rotor velocity is added or subtracted as needed to tangential velocity component during this transfer. The relative movement of the rotor and stator grids is accounted for by suitable periodic tangential shifting of the paired grid points in the overlap for the transfer. The method has been tested against a published DNS of a statorrotor stage. The Reynolds number based on blade chord and mean axial velocity at inflow was 40000. Solution fields show the wake vortex street of the upstream blade row impinging on downstream blades and being convected through the downstream blade passage. The LES captured transition on rotor blade surface boundary layers. Blade surface pressure distributions agree closely on pressure surfaces. Separation and transition on downstream blade suction surface is delayed slightly at the present resolution, but this will improve with grid refinement, monotonically, for this LES method.
Design Aspects for Large Diameter, Low Speed Axial Flow Fan for Wind Tunnel Application
Authors: Kesharwani Shubham , Mistry Chetan S. , Roy Subhransu , Roy Arnab , Sinhamahapatra Kalyan P.
Published: February 2018

A large diameter, low speed axial flow fan has been designed to drive the Centre for Railway Research (CRR) wind tunnel at IIT Kharagpur. Total pressure rise of 1400 Pa is required from the fan at the design mass flow rate of 420 kg/s. The outer diameter of the fan is 4 m with 0.6 hub to tip ratio. The present paper discusses the design methodology and computational analysis of wind tunnel fan. The design methodology includes a preliminary mean line analysis using the fundamental governing equations and CFX inbuilt design module. Subsequently, detailed computational analysis of the rotors was carried out using ANSYS CFX®. Based on the results obtained from the CFX analysis, the mean line analysis was modified to achieve the desired performance of the rotor. Parametric study was undertaken with different blade number combination, axial spacing, blade chord length, location of maximum thickness, leading edge profile, etc. The selection of number of blades for rotor and stator is an important aspect for such fan design in terms of cost, utility installation and noise. For low background noise in wind tunnel higher number of blades with suitable combination was selected for the fan ensuring the tone noise (produced by interaction of rotor and stator) is generated at attenuable frequencies. The blade angles, chord lengths, blade camber were optimized for good aerodynamic performance in terms of blade loading, wake thickness, hub-tip pressure profile, overall efficiency and pressure rise. It is strongly believed that discussed design aspects in terms of selection of various geometrical parameters for wind tunnel fan will give useful guidelines for future design of a low speed, large diameter fan of such capacity.
Multi-Swirl Lean Direct Injection Burner for Enhanced Combustion Stability and Low Pollutant Emissions
Authors: Deepika V. , Chakravarthy S. R. , Muruganandam T. M. , Raja Bharathi N.
Published: February 2018

Control of emissions is a big challenge plaguing the gas turbine industry for years. This necessitates new combustor designs addressing the problem. This paper discusses the characterization of a novel burner* employing Lean Direct Injection (LDI) technology for reduced pollutant emissions and improved combustion. The burner is an array of multiple swirlers arranged closely, facilitating distributed mixing of fuel and air at each swirler throughout the length of the burner. This results in a uniform and rapid mixing, thus eliminating hot spots and enabling efficient combustion. The burner thus developed is capable of operating at very lean conditions of fuel, leading to overall temperatures being low. The burner is characterized in terms of lean blow out equivalence ratio, pressure drop, average exit temperature of the burnt mixture, pattern factor and emissions — CO, CO2, unburned hydrocarbon (UHC), NOx and soot. Results show very low NOx emissions. Enhanced combustion also results in reduction in overall emissions. It overcomes the drawback of flame flashback encountered in lean premixed pre-vaporized concept. LDI is also less susceptible to combustion instability. Pressure drop across the burner is observed to be very less compared to the conventional gas turbine combustors. Thus, this concept of multi-swirl LDI burner can be a potential contender to be employed in the combustors of gas turbine engines.
Passive, broadband suppression of radiation of low-frequency sound
Authors: Godin Oleg A. , Baynes Alexander B.
Published: February 2018

Anthropogenic noise pollution of the ocean is an acute and growing problem. This letter explores one possible mechanism of noise abatement. The far-field acoustic pressure due to a compact underwater source can be suppressed by placing a small compliant body in the vicinity of the source. Here, the feasibility and efficiency of the suppression are evaluated by quantifying the reduction in radiated acoustic energy for several simple geometries, which include sound sources in an unbounded fluid, near a reflecting boundary, or in a shallow-water waveguide. The analysis is streamlined using analytic solutions for sound diffraction by simple shapes.
REVIEWS OF ACOUSTICAL PATENTS
Authors: Fulop Sean A. , Rice Lloyd
Published: February 2018

The purpose of these acoustical patent reviews is to provide enough information for a Journal reader to decide whether to seek more information from the patent itself. Any opinions expressed here are those of the reviewers as individuals and are not legal opinions. Printed copies of United States Patents may be ordered at $3.00 each from the Commissioner of Patents and Trademarks, Washington, DC 20231. Patents are available via the Internet at http://www.uspto.gov.
Pharmacokinetics and Safety of Intravenous Murepavadin Infusion in Healthy Adult Subjects Administered Single and Multiple Ascending Doses
Authors: Wach Achim , Dembowsky Klaus , Dale Glenn E.
Published: February 2018

Murepavadin is the first in class of the outer membrane protein-targeting antibiotics (OMPTA) and a pathogen-specific peptidomimetic antibacterial with a novel, nonlytic mechanism of action targeting
Pseudomonas aeruginosa
. Murepavadin is being developed for the treatment of hospital-acquired bacterial pneumonia (HABP) and ventilator-associated bacterial pneumonia (VABP). The pharmacokinetics (PK) and safety of single and multiple doses of murepavadin were investigated in healthy male subjects. Part A of the study was a double-blind, randomized, placebo-controlled, single-ascending-dose investigation in 10 sequential cohorts where each cohort comprised 6 healthy male subjects; 4 subjects were randomized to murepavadin, and 2 subjects were randomized to placebo. Part B was a double-blind, randomized, placebo-controlled, multiple-ascending-dose investigation in 3 sequential cohorts. After a single dose of murepavadin, the geometric mean half-life (2.52 to 5.30 h), the total clearance (80.1 to 114 ml/h/kg), and the volume of distribution (415 to 724 ml/kg) were consistent across dose levels. The pharmacokinetics of the dosing regimens evaluated were dose proportional and linear. Murepavadin was well tolerated, adverse events were transient and generally mild, and no dose-limiting toxicity was identified.
New onset diabetes after nivolumab treatment
Authors: Capitao Ricardo , Bello Carlos , Fonseca Ricardo , Saraiva Catarina
Published: February 2018

The authors describe a case of a life-threatening diabetic emergency 25 days after initiation of nivolumab (3 mg/kg) for stage 4 lung adenocarcinoma. She was admitted to the emergency department, with hyperglycaemia-related signs and symptoms, such as polyuria, polydipsia, weight loss, confusion, asthenia, dehydration, hypotension and Kussmaul respiratory pattern. Her body mass index was 21.9 kg/m2and she did not show acanthosis nigricans. Arterial blood gas determination revealed high anion gap metabolic acidaemia and blood tests showed hyperglycaemia (1060 mg/dL), hyperketonaemia (beta-hydroxybutyrate: 6.6 mmol/dL), elevated total serum osmolality (389 mOsm/kg), low serum and urinary C-peptide and positive antiglutamic acid decarboxylase antibodies. Since nivolumab was initiated a few days before, and due to its known immune-mediated endocrine adverse events, we assumed the diagnosis of new onset immune-mediated type 1 diabetes mellitus. After prompt and adequate treatment of diabetic ketoacidosis/hyperosmolar hyperglycaemic state, she was discharged improved on multiple daily injections of insulin.
Depression and anxiety symptoms in 17 teams of female football players including 10 German first league teams
Authors: Junge Astrid , Prinz Birgit
Published: February 2018

Background

Information on the prevalence of mental health problems of elite athletes is inconclusive, most probably due to methodological limitations, such as low response rates, heterogeneous samples.

Aims

To evaluate the prevalence and risk factors of depression and anxiety symptoms in high-level female football players.

Methods

Female football players of 10 German first league (Bundesliga) and 7 lower league teams were asked to answer a questionnaire on players’ characteristics, the Center of Epidemiologic Studies Depression Scale (CES-D) and the Generalised Anxiety Disorder (GAD-7) scale.

Results

A total of 290 players (184 first and 106 lower league players) took part in the study. The CES-D score indicated mild to moderate symptoms of depression in 48 (16.6%) and severe symptoms in 41 (14.1%) players. The GAD-7 score indicated an at least moderate generalised anxiety disorder in 24 (8.3%) players. The prevalence of depression symptoms and generalised anxiety disorders was similar to the female general population of similar age. However, significantly more second league players reported symptoms of depression than first league players, and thus the prevalence of depression symptoms in second league players was higher than in the general population. Only a third of the 45 (15.7%) players who stated that they currently wanted or needed psychotherapeutic support received it.

Conclusion

The prevalence of depression and generalised anxiety symptoms in elite football players is influenced by personal and sport-specific variables. It is important to raise awareness of athletes’ mental health problems in coaches and team physicians, to reduce stigma and to provide low-threshold treatment.